U.S. patent application number 14/348648 was filed with the patent office on 2014-11-06 for detecting device and method, and program.
This patent application is currently assigned to OMRON CORPORATION. The applicant listed for this patent is Hiroshi Imai, Yasuhiro Kawabata, Shuichi Misumi, Hiroshi Sameshima. Invention is credited to Hiroshi Imai, Yasuhiro Kawabata, Shuichi Misumi, Hiroshi Sameshima.
Application Number | 20140327428 14/348648 |
Document ID | / |
Family ID | 46171492 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140327428 |
Kind Code |
A1 |
Misumi; Shuichi ; et
al. |
November 6, 2014 |
DETECTING DEVICE AND METHOD, AND PROGRAM
Abstract
The present invention relates to a detecting device and method,
and a program which can detect a power state easily at low cost. A
current transformer measures current of a commercial power system
from a commercial power supply through a connection point of the
commercial power system and a power generation system from a solar
power generation system that supplies power having the same
frequency as the commercial power supply. A current transformer
measures power at the power generation system side through the
connection point. A decision value calculator calculates a decision
value based on a value obtained through multiplication of a
measured value of current through the current transformer and
through the current transformer. A flow detector detects a power
flow of the commercial power system based on the calculated value.
The present invention can be applied to a power measuring system
for use in homes, for example.
Inventors: |
Misumi; Shuichi; (Kyoto,
JP) ; Imai; Hiroshi; (Nara, JP) ; Kawabata;
Yasuhiro; (Kyoto, JP) ; Sameshima; Hiroshi;
(Nara, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Misumi; Shuichi
Imai; Hiroshi
Kawabata; Yasuhiro
Sameshima; Hiroshi |
Kyoto
Nara
Kyoto
Nara |
|
JP
JP
JP
JP |
|
|
Assignee: |
OMRON CORPORATION
Kyoto
JP
|
Family ID: |
46171492 |
Appl. No.: |
14/348648 |
Filed: |
December 8, 2011 |
PCT Filed: |
December 8, 2011 |
PCT NO: |
PCT/JP2011/078444 |
371 Date: |
July 15, 2014 |
Current U.S.
Class: |
324/76.11 |
Current CPC
Class: |
G01R 21/06 20130101;
G01R 21/133 20130101; G01R 21/00 20130101; Y02B 10/14 20130101;
Y02B 10/10 20130101; G01R 19/2513 20130101; G01R 19/14
20130101 |
Class at
Publication: |
324/76.11 |
International
Class: |
G01R 21/00 20060101
G01R021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2011 |
JP |
2011-261161 |
Claims
1. A detecting device configured to detect a power state,
comprising: a first current transformer configured to measure first
current at a side of a first power system from a commercial power
supply through a connection point of the first power system and a
second power system from a power generator configured to supply
power having the same frequency as the commercial power supply; a
second current transformer configured to measure second current at
the second power system side through the connection point; a first
calculator configured to calculate a decision value based on a
value obtained through multiplication of a measured value of the
first current and that of the second current; and a detector
configured to detect a power flow of the first power system based
on the decision value.
2. The detecting device according to claim 1, wherein the detector
decides that the power flow of the first power system is a
direction in which power is supplied from the commercial power
supply regardless of the decision value if an effective value of
the first current is greater than that of the second current.
3. The detecting device according to claim 1, wherein the detector
decides that the power flow of the first power system is a
direction in which power is supplied from the commercial power
supply if the effective value of the second current is equal to or
smaller than a specified value.
4. The detecting device according to claim 1, wherein the first
calculator calculates, as the decision value, an integrated value
of the multiplied value for n cycles (n is a natural number) of the
power of the commercial power supply.
5. The detecting device according to claim 1, wherein the first
calculator is calculated, as the decision value, a value obtained
through multiplication of the measured value of the first current
and that of the second current when the second current reaches a
positive or negative peak.
6. The detecting device according to claim 1, further comprising a
second calculator configured to calculate first power to be
supplied from the commercial power supply to the first power system
and second power to be supplied from the power generator to the
first power system based on the measured value of the first current
and the power flow of the first power system.
7. The detecting device according to claim 6, wherein the second
calculator further calculates third power to be supplied to a load
connected to the connection point based on the measured value of
the first current, the measured value of the second current and the
power flow of the first power system.
8. The detecting device according to claim 6 further comprising a
display configured to display the first power and the second
power.
9. The detecting device according to claim 6, further comprising a
communicator configured to transmit, to an outside, information
including at least one combination in the first power and the
second power, and the measured value of the first current and the
power flow of the first power system.
10. A method of detecting a power state by a detecting device,
comprising the steps of: measuring first current by a first current
transformer at a side of a first power system from a commercial
power supply through a connection point of the first power system
and a second power system from a power generator configured to
supply power having the same frequency as the commercial power
supply and measuring second current by a second current transformer
at the second power system side through the connection point;
calculating a decision value based on a value obtained through
multiplication of a measured value of the first current and that of
the second current; and detecting a power flow of the first power
system based on the decision value.
11. A detecting device comprising: a calculator configured to
calculate a decision value based on a value obtained through
multiplication of a measured value of first current measured by a
first current transformer at a side of a first power system from a
commercial power supply through a connection point of the first
power system and a second power system from a power generator
configured to supply power having the same frequency as the
commercial power supply and a measured value of second current
measured by a second current transformer at the second power system
side from the connection point; and a detector configured to detect
a power flow of the first power system based on the decision
value.
12. A method of detecting a power state by a detecting device,
comprising the steps of: calculating a decision value based on a
value obtained through multiplication of a measured value of first
current measured by a first current transformer at a side of a
first power system from a commercial power supply through a
connection point of the first power system and a second power
system from a power generator configured to supply power having the
same frequency as the commercial power supply and a measured value
of second current measured by a second current transformer at the
second power system side from the connection point; and detecting a
power flow of the first power system based on the decision
value.
13. A non-transitory computer readable storage medium encoded with
an executable computer program for detecting a power state and
that, when executed by a processor, causes the processor to perform
operations comprising: calculating a decision value based on a
value obtained through multiplication of a measured value of first
current measured by a first current transformer at a side of a
first power system from a commercial power supply through a
connection point of the first power system and a second power
system from a power generator configured to supply power having the
same frequency as the commercial power supply and a measured value
of second current measured by a second current transformer at the
second power system side from the connection point; and detecting a
power flow of the first power system based on the decision value.
Description
BACKGROUND
[0001] 1. Field
[0002] The present invention relates to a detecting device and
method, and a program, and more particularly to a detecting device
and method and a program which are suitably used in detection of a
power state in facilities provided with a private power
generator.
[0003] 2. Related Art
[0004] In recent years, with spread of a solar power generation
system or start of an excess power purchasing scheme of the solar
power generation system, the need for knowing generated power and
sold power (excess power), for example, in the solar power
generation system, power purchased from a commercial power supply,
power consumed in homes also increases in ordinary homes.
[0005] Moreover, there has been proposed a technique for detecting
a state in which excess power of a private power generator such as
a solar power generation system is supplied to a commercial power
supply side and power is thus sold (which is hereinafter referred
to as a power selling state) or a state in which the power is
supplied from the commercial power supply and is thus purchased
(which is hereinafter referred to as a power purchasing state) (for
example, see Japanese Laid-Open Patent Publications No.
2004-279321, No. 2004-297959 and No. 11-225440). Referring to the
inventions described in the Japanese Laid-Open Patent Publications
No. 2004-279321, No. 2004-297959 and No. 11-225440, voltage and
current of the power system on the commercial power supply side are
measured, power is calculated from the measured voltage and
current, a power flow is detected based on a sign (plus or minus)
of the calculated power, and it is decided whether the power
purchasing state or the power selling state is set.
[0006] In order to measure voltage in a power system on a
commercial power supply side (hereinafter referred to as a
commercial power system) in ordinary homes, it is necessary to
directly insert a dedicated measuring unit into the commercial
power system.
[0007] However, the measuring unit highly requires safety and
reliability and is manufactured at high cost. Moreover, an
installation work for the measuring unit is required and an
electrical failure occurs under construction. Furthermore, a
qualification is required for the installation work. For this
reason, ordinary people cannot perform the installation work.
Accordingly, time and labor, cost and the like are increased so
that it is impossible to introduce the facilities for simply
detecting the power state in homes.
SUMMARY
[0008] In consideration of the circumstances, it is an object of
the present invention to enable detection of a power state easily
at low cost.
[0009] A detecting device according to a first aspect of the
present invention includes a first current transformer configured
to measure first current at a side of a first power system from a
commercial power supply through a connection point of the first
power system and a second power system from a power generator
configured to supply power having the same frequency as the
commercial power supply, a second current transformer configured to
measure second current at the second power system side through the
connection point, a first calculator configured to calculate a
decision value based on a value obtained through multiplication of
a measured value of the first current and a measured value of the
second current, and a detector configured to detect a power flow of
the first power system based on the decision value.
[0010] In the detecting device according to the first aspect of the
present invention, first current is measured at a side of a first
power system from a commercial power supply through a connection
point of the first power system and a second power system from a
power generator configured to supply power having the same
frequency as the commercial power supply and second current is
measured at the second power system side through the connection
point, a decision value is calculated based on a value obtained
through multiplication of a measured value of the first current and
a measured value of the second current, and a power flow of the
first power system is detected based on the decision value.
[0011] Accordingly, it is possible to detect the power flow at the
commercial power supply side easily at low cost.
[0012] The first calculator is configured from an analog
multiplication circuit or integration circuit, a digital arithmetic
circuit, a microcomputer, various processors or the like, for
example. The detector is configured from a comparison circuit or a
decision circuit using an operational amplifier or the like, a
digital arithmetic circuit, a microcomputer, various processors or
the like, for example.
[0013] The detector can be caused to decide that the power flow of
the first power system is a direction in which power is supplied
from the commercial power supply regardless of the decision value
if an effective value of the first current is greater than that of
the second current.
[0014] Consequently, it is possible to prevent the power from being
decided to be sold regardless of the purchase of the power from the
commercial power supply.
[0015] The detector can be caused to decide that the power flow of
the first power system is a direction in which power is supplied
from the commercial power supply if the effective value of the
second current is equal to or smaller than a specified value.
[0016] When the current of the power generation system is extremely
small and the decision of the flow is unstable, consequently, it is
possible to prevent the power from being decided to be sold
regardless of the purchase of the power from the commercial power
supply.
[0017] The first calculator can be caused to calculate, as the
decision value, an integrated value of the multiplied value for n
cycles (n is a natural number) of the power of the commercial power
supply.
[0018] Consequently, it is possible to enhance detection precision
in the power flow at the commercial power side.
[0019] The first calculator can be caused to calculate, as the
decision value, a value obtained through multiplication of the
measured value of the first current and that of the second current
when the second current reaches a positive or negative peak.
[0020] Consequently, it is possible to enhance detection precision
in the power flow at the commercial power supply side in the case
in which a capacitive load is connected.
[0021] It is possible to further provide a second calculator
configured to calculate first power to be supplied from the
commercial power supply to the first power system and second power
to be supplied from the power generator to the first power system
based on the measured value of the first current and the power flow
of the first power system.
[0022] Consequently, it is possible to easily measure power sold by
a private power generator and power purchased from the commercial
power supply at low cost.
[0023] The second calculator is configured from a digital
arithmetic circuit, a microcomputer, various processors or the
like, for example. The first power is set to be the purchased power
and the second power is set to be the sold power, for example.
[0024] The second calculator can be caused to further calculate
third power to be supplied to a load connected to the connection
point based on the measured value of the first current, the
measured value of the second current and the power flow of the
first power system.
[0025] Consequently, it is possible to easily measure power
consumed by a load at low cost.
[0026] The third power is set to be the consumed power, for
example.
[0027] It is possible to further provide a display configured to
display the first power and the second power.
[0028] Consequently, it is possible to cause a user to readily
grasp the sold power and the purchased power.
[0029] The display is configured from various display devices,
various light emitting devices or the like, for example.
[0030] It is possible to further provide a communicator configured
to transmit, to an outside, information including at least one
combination in the first power and the second power, and the
measured value of the first current and the power flow of the first
power system.
[0031] Consequently, it is possible to give a notice of the
detected power state to an outside.
[0032] The communicator is configured from various cable or
wireless communicators, for example.
[0033] A detecting method according to the first aspect of the
present invention by a detecting device configured to detect a
power state includes the steps of measuring first current by a
first current transformer at a side of a first power system from a
commercial power supply through a connection point of the first
power system and a second power system from a power generator
configured to supply power having the same frequency as the
commercial power supply and measuring second current by a second
current transformer at the second power system side through the
connection point, calculating a decision value based on a value
obtained through multiplication of a measured value of the first
current and a measured value of the second current, and detecting a
power flow of the first power system based on the decision
value.
[0034] In the detecting method according to the first aspect of the
present invention, first current is measured at a side of a first
power system from a commercial power supply through a connection
point of the first power system and a second power system from a
power generator configured to supply power having the same
frequency as the commercial power supply and second current is
measured at the second power system side through the connection
point, a decision value is calculated based on a value obtained
through multiplication of a measured value of the first current and
a measured value of the second current, and a power flow of the
first power system is detected based on the decision value.
[0035] Accordingly, it is possible to detect the power flow at the
commercial power supply side easily at low cost.
[0036] The calculating step is executed by an analog multiplication
circuit or integration circuit, a digital arithmetic circuit, a
microcomputer, various processors or the like, for example. The
detecting step is executed by a comparison circuit or a decision
circuit using an operational amplifier or the like, a digital
arithmetic circuit, a microcomputer, various processors or the
like, for example.
[0037] A detecting device according to a second aspect of the
present invention includes a calculator configured to calculate a
decision value based on a value obtained through multiplication of
a measured value of first current measured by a first current
transformer at a side of a first power system from a commercial
power supply through a connection point of the first power system
and a second power system from a power generator configured to
supply power having the same frequency as the commercial power
supply and a measured value of second current measured by a second
current transformer at the second power system side from the
connection point, and a detector configured to detect a power flow
of the first power system based on the decision value.
[0038] In the detecting device according to the second aspect of
the present invention, a decision value is calculated based on a
value obtained through multiplication of a measured value of first
current measured by a first current transformer at a side of a
first power system from a commercial power supply through a
connection point of the first power system and a second power
system from a power generator configured to supply power having the
same frequency as the commercial power supply and a measured value
of second current measured by a second current transformer at the
second power system side from the connection point, and a power
flow of the first power system is detected based on the decision
value.
[0039] Accordingly, it is possible to detect the power flow at the
commercial power supply side easily at low cost.
[0040] The calculator is configured from an analog multiplication
circuit or integration circuit, a digital arithmetic circuit, a
microcomputer, various processors or the like, for example. The
detector is configured from a comparison circuit or a decision
circuit using an operational amplifier or the like, a digital
arithmetic circuit, a microcomputer, various processors or the
like, for example.
[0041] A detecting method according to the second aspect of the
present invention by a detecting device configured to detect a
power state includes the steps of calculating a decision value
based on a value obtained through multiplication of a measured
value of first current measured by a first current transformer at a
side of a first power system from a commercial power supply through
a connection point of the first power system and a second power
system from a power generator configured to supply power having the
same frequency as the commercial power supply and a measured value
of second current measured by a second current transformer at the
second power system side from the connection point, and detecting a
power flow of the first power system based on the decision
value.
[0042] In the detecting method according to the second aspect of
the present invention, a decision value is calculated based on a
value obtained through multiplication of a measured value of first
current measured by a first current transformer at a side of a
first power system from a commercial power supply through a
connection point of the first power system and a second power
system from a power generator configured to supply power having the
same frequency as the commercial power supply and a measured value
of second current measured by a second current transformer at the
second power system side from the connection point, and a power
flow of the first power system is detected based on the decision
value.
[0043] Accordingly, it is possible to detect the power flow at the
commercial power supply side easily at low cost.
[0044] The calculating step is executed by an analog multiplication
circuit or integration circuit, a digital arithmetic circuit, a
microcomputer, various processors or the like, for example. The
detecting step is executed by a comparison circuit or a decision
circuit using an operational amplifier or the like, a digital
arithmetic circuit, a microcomputer, various processors or the
like, for example.
[0045] A program according to the second aspect of the present
invention causes a computer to execute processing including the
steps of calculating a decision value based on a value obtained
through multiplication of a measured value of first current
measured by a first current transformer at a side of a first power
system from a commercial power supply through a connection point of
the first power system and a second power system from a power
generator configured to supply power having the same frequency as
the commercial power supply and a measured value of second current
measured by a second current transformer at the second power system
side from the connection point, and detecting a power flow of the
first power system based on the decision value.
[0046] In the computer configured to execute the program according
to the second aspect of the present invention, a decision value is
calculated based on a value obtained through multiplication of a
measured value of first current measured by a first current
transformer at a side of a first power system from a commercial
power supply through a connection point of the first power system
and a second power system from a power generator configured to
supply power having the same frequency as the commercial power
supply and a measured value of second current measured by a second
current transformer at the second power system side from the
connection point, and a power flow of the first power system is
detected based on the decision value.
[0047] Accordingly, it is possible to detect the power flow at the
commercial power supply side easily at low cost.
[0048] According to the first or second aspect of the present
invention, it is possible to detect the power state easily at low
cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a block diagram showing an embodiment of a power
monitoring system to which the present invention is applied;
[0050] FIG. 2 is a diagram showing an example of an installation
position of a current transformer;
[0051] FIG. 3 is a flowchart for explaining power monitor
processing;
[0052] FIG. 4 is a graph showing an example of a phase difference
in voltage and current through a load;
[0053] FIG. 5 is a graph showing another example of the phase
difference in the voltage and the current through the load;
[0054] FIG. 6 is a chart for explaining a method of calculating a
decision value;
[0055] FIG. 7 is a chart for explaining the method of calculating a
decision value;
[0056] FIG. 8 is a graph showing an example of a waveform of
current in the case in which a capacitive load is connected;
[0057] FIG. 9 is a chart for explaining the method of calculating a
decision value;
[0058] FIG. 10 is a view showing an example of a method of
installing a current transformer in the case of a single phase
three-wire type;
[0059] FIG. 11 is a graph showing an example of a state in which a
power factor of a power generation system is minimized;
[0060] FIG. 12 is a graph showing an example of the state in which
the power factor of the power generation system is minimized;
[0061] FIG. 13 is a block diagram showing a variant of the power
monitoring system to which the present invention is applied;
[0062] FIG. 14 is a flowchart for explaining a first embodiment of
power monitor processing to be executed by the power monitoring
system in FIG. 13;
[0063] FIG. 15 is a graph showing a condition for deciding that a
power selling state is set by the processing of FIG. 14;
[0064] FIG. 16 is a flowchart for explaining a second embodiment of
the power monitor processing to be executed by the power monitoring
system in FIG. 13;
[0065] FIG. 17 is a graph showing a condition for deciding that a
power selling state is set by the processing of FIG. 16; and
[0066] FIG. 18 is a block diagram showing an example of a structure
of a computer.
DETAILED DESCRIPTION
[0067] An embodiment for carrying out the present invention is
descried below. Explanation is given in the following order.
[0068] 1. Embodiment
[0069] 2. Variant
1. Embodiment
Example of Structure of Power Monitoring System
[0070] FIG. 1 is a block diagram showing an embodiment of power
monitoring system 101 to which the present invention is applied,
and FIG. 2 shows an example of installation positions of current
transformers 111p and 111c in power monitoring system 101.
[0071] A left side of a dotted line in FIG. 2 is set to be an
interior of a home in which power monitoring system 101 and solar
power generation system 151 are provided. Moreover, a power system
from solar power generation system 151 to connection point C, a
power system from commercial power supply 152 to connection point
C, and a power system from connection point C to load 153 are
hereinafter referred to as a power generation system, a commercial
power system and a load power system, respectively. In the
following, it is assumed that the respective power systems are of a
single phase two-wire type in the interior.
[0072] In the following, furthermore, voltage of the power
generation system (=output voltage of solar power generation system
151) is represented by v.sub.p1, current is represented by
i.sub.p1, and a direction of arrow Ap1 is set to be a positive
direction. In the following, moreover, voltage of the commercial
power system (=output voltage of commercial power supply 152) is
represented by v.sub.c1, current is represented by i.sub.c1, and a
direction of arrow Ac1 is set to be a positive direction.
Accordingly, current of i.sub.p1+i.sub.c1 flows to the load power
system in a direction of arrow Apc.
[0073] Power monitoring system 101 serves to detect and monitor a
power state in the interior. As described below, power monitoring
system 101 detects a power flow of the commercial power system
(which is hereinafter referred to as commercial side power) based
on current i.sub.p1 and current i.sub.c1 and decides whether a
power purchasing state or a power selling state is set. Moreover,
power monitoring system 101 measures power generated by solar power
generation system 151 and excess power of solar power generation
system 151, that is, sold power supplied from solar power
generation system 151 to the commercial power system. Furthermore,
power monitoring system 101 measures purchased power supplied from
commercial power supply 152 to the commercial power system and
consumed power supplied from solar power generation system 151 and
commercial power supply 152 to the load power system and consumed
by load 153.
[0074] Solar power generation system 151 includes solar battery
module 161 and PV (Photo Voltaic) controller 162.
[0075] Solar battery module 161 generates DC power by solar power
generation and supplies the generated DC power to PV controller
162.
[0076] PV controller 162 converts DC power supplied from solar
battery module 161 into AC power having almost equal voltage and
frequency to those of commercial power supply 152, and furthermore,
synchronizes a phase of the voltage of the converted AC power with
a phase of the voltage of commercial power supply 152. Then, PV
controller 162 outputs the AC power (hereinafter referred to as
generated power).
[0077] Load 153 is configured from various electrical apparatus,
for example, electric appliances such as a refrigerator.
[0078] The power generation system and the commercial power system
join together and the load power system is branched at connection
point C. Connection point C corresponds to a distribution board in
a home, for example.
[0079] The structure of power monitoring system 101 is described in
more detail.
[0080] Power monitoring system 101 includes current transformer
111p, current transformer 111c and detecting device 112. Moreover,
detecting device 112 includes measuring unit 121p, measuring unit
121c, arithmetic unit 122, display 123 and communicator 124.
[0081] Current transformer 111p is provided on a wiring between
solar power generation system 151 and connection point C and
measures current i.sub.p1 of the power generation system. More
accurately, current transformer 111p converts current i.sub.p1
(primary current) into current i.sub.p2 (secondary current) and
supplies current i.sub.p2 to measuring unit 121p. It is assumed
that current transformer 111p is provided in such an orientation
that current i.sub.p2 flows in a direction of arrow Ap2 when
current i.sub.p1 flows in the direction of arrow Ap1.
[0082] Measuring unit 121p converts current i.sub.p2 into voltage
v.sub.p2 by built-in resistor Rp. Voltage v.sub.p2 has a positive
value when current i.sub.p1 flows in the direction of arrow Ap1 and
current i.sub.p2 flows in the direction of arrow Ap2, and has a
negative value when current i.sub.p1 flows in a reverse direction
to arrow Ap1 and current i.sub.p2 flows in a reverse direction to
arrow Ap2. In other words, a phase of current i.sub.p1 and that of
voltage v.sub.p2 are coincident with each other when the direction
of arrow Ap1 is positive.
[0083] Moreover, measuring unit 121p supplies a signal indicative
of voltage v.sub.p2 (hereinafter referred to as signal v.sub.p2) to
arithmetic unit 122.
[0084] Current transformer 111c is provided on a wiring of the
interior between commercial power supply 152 and connection point C
and measures current i.sub.c1 of the commercial power system. More
accurately, current transformer 111c converts current i.sub.c1
(primary current) into current i.sub.c2 (secondary current) and
supplies current i.sub.c2 to measuring unit 121c. It is assumed
that current transformer 111c is provided in such an orientation
that current i.sub.c1 flows in a direction of arrow Ac2 when
current i.sub.c1 flows in a direction of arrow Ac1.
[0085] Measuring unit 121c converts current i.sub.c2 into voltage
v.sub.c2 by built-in resistor Rc. Voltage v.sub.c2 has a positive
value when current i.sub.c1 flows in the direction of arrow Ac1 and
current i.sub.c2 flows in the direction of arrow Ac2, and has a
negative value when current i.sub.c1 flows in a reverse direction
to arrow Ac1 and current i.sub.c2 flows in a reverse direction to
arrow Ac2. In other words, a phase of current i.sub.c1 and that of
voltage v.sub.c2 are coincident with each other when the direction
of arrow Ac1 is positive.
[0086] In the power purchasing state in which the commercial side
power is supplied in the direction of arrow Ac1, a difference
between the phase of voltage v.sub.c1 and that of voltage v.sub.c2
(=a phase of current i.sub.c1) is equal to or smaller than
.+-..pi./2 in consideration of a power factor of load 153 and a
phase synchronization error of PV controller 162. To the contrary,
in the power selling state in which the commercial side power is
supplied in the reverse direction to arrow Ac1, the difference
between the phase of voltage v.sub.c1 and that of voltage v.sub.c2
(=the phase of current i.sub.c1) ranges from -.pi. to -.pi./2 or
from .pi./2 to .pi.. As described below, it is empirically apparent
that a general power factor of a load for a home is equal to or
higher than cos(.pi./6).
[0087] Moreover, measuring unit 121c supplies a signal indicative
of voltage v.sub.c2 (hereinafter referred to as signal v.sub.c2) to
arithmetic unit 122.
[0088] Arithmetic unit 122 is configured from a microcomputer, for
example, and includes converter 131, decision value calculator 132,
flow detector 133, and power calculator 134.
[0089] Converter 131 converts a value of voltage v.sub.p2 indicated
by signal v.sub.p2 into a value of current i.sub.p1 based on a
current transformation ratio of current transformer 111p and a
resistance value of resistor Rp which are known, and gives a notice
of the value obtained by the conversion to decision value
calculator 132 and power calculator 134. Moreover, converter 131
converts the value of voltage v.sub.c2 indicated by signal v.sub.c2
into a value of current i.sub.c1 based on a current transformation
ratio of current transformer 111c and a resistance value of
resistor Rc which are known, and gives a notice of the value
obtained by the conversion to decision value calculator 132 and
power calculator 134.
[0090] Decision value calculator 132 calculates a decision value to
be used for detecting the flow of the commercial side power based
on a measured value of current i.sub.p1 and that of current
i.sub.c1 as described below. Decision value calculator 132 gives a
notice of the decision value obtained by the calculation to flow
detector 133.
[0091] Flow detector 133 detects the flow of the commercial side
power and gives a notice of a detection result to power calculator
134 based on the decision value calculated by decision value
calculator 132 as described below.
[0092] Power calculator 134 calculates generated power, sold power,
purchased power and consumed power based on the measured value of
current i.sub.p1, the measured value of current i.sub.c1, and the
detection result of the flow of the commercial side power as
described below. Power calculator 134 gives a notice of the result
obtained by the calculation to display 123 and communicator
124.
[0093] Display 123 is configured from a display device such as an
LCD (Liquid Crystal Display), a light emitting device such as an
LED (Light Emitting Diode), or the like, and displays a power state
of each unit thereon.
[0094] Communicator 124 is configured from various communication
devices and transmits power state information indicative of the
power state of each unit to an external device. An optional method
can be employed for a communication method of communicator 124
regardless of cable or wireless.
[0095] [Power Monitor Processing]
[0096] Next, power monitor processing to be executed by power
monitoring system 101 is described with reference to a flowchart of
FIG. 3. The processing is started when a power supply of power
monitoring system 101 is turned ON, and is ended when the power
supply is turned OFF, for example.
[0097] In step S1, power monitoring system 101 measures current.
Specifically, current transformer 111p converts current i.sub.p1
flowing through the power generation system into current i.sub.p2
and supplies current i.sub.p2 to measuring unit 121p. Measuring
unit 121p converts current i.sub.p2 into voltage v.sub.p2 and
supplies signal v.sub.p2 Indicative of voltage v.sub.p2 to
converter 131. Moreover, current transformer 111c converts current
i.sub.c1 flowing through the commercial power system into current
i.sub.c2 and supplies current i.sub.c2 to measuring unit 121c.
Measuring unit 121c converts current i.sub.c2 into voltage v.sub.c2
and supplies signal v.sub.c2 Indicative of voltage v.sub.c2 to
converter 131.
[0098] Converter 131 converts a value of voltage v.sub.p2 indicated
by signal v.sub.p2 into a value of current i.sub.p1 and gives a
notice of the value obtained by the conversion to decision value
calculator 132 and power calculator 134. Moreover, converter 131
converts a value of voltage v.sub.c2 indicated by signal v.sub.c2
into a value of current i.sub.c1 and gives a notice of the value
obtained by the conversion to decision value calculator 132 and
power calculator 134.
[0099] In step S2, decision value calculator 132 calculates a
decision value and gives a notice of the calculated decision value
to flow detector 133.
[0100] In step S3, flow detector 133 detects a flow of the
commercial side power based on the decision value and gives a
notice of the detected flow to power calculator 134.
[0101] With reference to FIGS. 4 to 9, description is given to a
specific example of a method of detecting the decision value and
the flow of the commercial side power in the processing of steps S2
and S3.
[0102] For example, in the case in which current i.sub.p1 and
current i.sub.c1 are continuously measured by an analog circuit or
the like, decision value V1 obtained in accordance with the
following equation (1) is used.
[ Equation 1 ] D 1 = .intg. t = 0 t = T ip ( t ) .times. ic ( t ) t
( 1 ) ##EQU00001##
[0103] Time T indicates time of one cycle for the power of
commercial power supply 152 (=1/frequency of commercial power
supply 152).
[0104] Decision value V1 is a value obtained by integrating, for
one cycle, a value calculated though multiplication of an
instantaneous value of current i.sub.p1 and that of current
i.sub.c1 at almost the same time. When the phase of current
i.sub.p1 is represented by .phi.p and the phase of current i.sub.c1
is represented by .phi.c, accordingly, the decision value is
obtained as V1.gtoreq.0 if |.phi.p-.phi.c|.ltoreq..pi./2 is set,
and the decision value is obtained as V1<0 if
.pi./2<|.phi.p-.phi.c|.ltoreq..pi. is set.
[0105] As described above, it is empirically apparent that the
power factor of the general load for homes is equal to or higher
than cos(.pi./6). Therefore, a phase difference between a voltage
waveform and a current waveform is equal to or smaller than
.pi./6.
[0106] For example, FIG. 4 is a graph showing a result obtained by
applying AC voltage of 100V to a fluorescent light and measuring
current through a current transformer. In FIG. 4, an axis of
abscissa indicates time and an axis of ordinate indicates voltage
and current. Waveform 201 represents a waveform of voltage,
waveform 202 represents a waveform of current in the case in which
a current transformer is attached in a direction in which a current
value is positive when the voltage and the current have the same
phase, and waveform 203 represents a waveform of the current in the
case in which the current transformer is attached in the direction
in which the current value is positive when the voltage and the
current have reverse phases to each other. In this case, the
difference between the phases of the voltage applied to the
fluorescent light and the current flowing to the fluorescent light
is approximately 11.5 degrees (<.pi./6).
[0107] FIG. 5 is a graph showing a result obtained by applying AC
voltage of 100V to another load and measuring current through the
current transformer attached in the direction in which the current
value is positive when the voltage and the current have the same
phase.
[0108] In FIG. 5, an axis of abscissa indicates time and an axis of
ordinate indicates voltage and current. Waveform 211 represents a
waveform of the voltage, waveform 212 represents a waveform of the
current in the case in which the load is a microwave oven, and
waveform 213 represents a waveform of the current in the case in
which the load is a personal computer and a display. Also in this
example, the phase difference between the voltage and the current
is smaller than .pi./6.
[0109] Accordingly, it is possible to assume that the phase
difference between voltage v.sub.p1 and current i.sub.p1 in the
power generation system is equal to or smaller than .+-..pi./6.
Moreover, it is possible to assume that the phase difference
between voltage v.sub.c1 and current i.sub.c1 in the commercial
power system is equal to or smaller than .+-..pi./6 in the power
purchasing state and is equal to or smaller than .pi..+-..pi./6 in
the power selling state. Consequently, it is possible to assume
that |.phi.p-.phi.c|.ltoreq..pi./3 is obtained and the decision
value is obtained as V1.gtoreq.0 in the power purchasing state. On
the other hand, it is possible to assume that
2.pi./3|.phi.p-.phi.c|.ltoreq..pi. is obtained and the decision
value is obtained as V1<0 in the power selling state.
[0110] Therefore, it is possible to detect the flow of the
commercial side power based on decision value V1. In other words,
it is possible to decide that there is set the power purchasing
state in which the commercial side power is supplied in the
direction of arrow Ac1 with the decision value V1.gtoreq.0 and to
decide that there is set the power selling state in which the
commercial side power is supplied in the direction of arrow Ac1
with decision value V1<0.
[0111] In the case in which current i.sub.p1 and current i.sub.c1
are discretely measured by a digital arithmetic circuit or the like
as shown in FIG. 6, for example, decision value V2 calculated in
accordance with the following Equation (2) is used.
[ Equation 2 ] D 2 = k = 0 m ip [ k ] .times. ic [ k ] ( 2 )
##EQU00002##
[0112] FIG. 6 shows an example of the waveforms of current i.sub.p1
and current i.sub.c1 in the power selling state, and an axis of
abscissa indicates time and an axis of ordinate indicates a current
value. Moreover, circle and square marks in FIG. 6 represent
sampling points. For easy understanding of the drawings, FIG. 6
shows only a part of the sampling points.
[0113] Moreover, k in the equation (2) indicates numbers of the
sampling points of current i.sub.p1 and current i.sub.c1, and m
indicates the number of sampling operations per cycle. Furthermore,
i.sub.p1 [k] indicates a sampling value of current i.sub.p1 at a
kth sampling point and i.sub.c1 [k] indicates a sampling value of
current i.sub.c1 at the kth sampling point.
[0114] Decision value V2 is a value obtained by integrating, for
one cycle, a value calculated though multiplication of the sampling
values of current i.sub.p1 and current i.sub.c1 at almost the same
time. In the same manner as decision value V1, accordingly, the
decision value is obtained as V2.gtoreq.0 when
|.phi.p-.phi.c|.ltoreq..pi./2 is set, and the decision value is
obtained as V2<0 when .pi./2<|.phi.p-.phi.c|.ltoreq..pi. is
set.
[0115] In the same manner as in the case in which decision value V1
is used, accordingly, it is possible to decide that the power
purchasing state is set with decision value V2.gtoreq.0 and the
power selling state is set with decision value V2<0.
[0116] For example, in the case in which a value of current
i.sub.p1 and a value of current i.sub.c1 are set to be
i.sub.p1(t.sub.max) and i.sub.c1(t.sub.max) at time t.sub.max that
current i.sub.p1 reaches a positive peak, respectively as shown in
FIG. 7, decision value V3 calculated in accordance with the
following equation (3) may be used.
V3=i.sub.p1(t.sub.max).times.i.sub.c1(t.sub.max) (3)
[0117] Also in this case, in the same manner as the case in which
decision value V1 is used, it is possible to decide that the power
purchasing state is set with decision value V3.gtoreq.0 and to
decide that the power selling state is set with decision value
V3<0.
[0118] By utilizing value i.sub.p1 (t.sub.min) of current i.sub.p1
and value i.sub.c1(t.sub.min) of current i.sub.c1 at time t.sub.min
that current i.sub.p1 reaches a negative peak respectively,
similarly, it is also possible to use decision value V4 calculated
in accordance with the following equation (4).
V4=i.sub.p1(t.sub.min).times.i.sub.c1(t.sub.min) (4)
[0119] Also in this case, in the same manner as the case in which
decision value V3 is used, it is possible to decide that the power
purchasing state is set with decision value V4.gtoreq.0 and to
decide that the power selling state is set with decision value
V4<0.
[0120] FIG. 8 shows an example of waveforms of current i.sub.p1 and
current i.sub.c1 in the power selling state in the case in which
load 153 is mainly configured from a capacitive load (a capacitor
load). An axis of abscissa indicates time and an axis of ordinate
indicates current.
[0121] As shown in the drawing, in the case in which load 153 is
mainly configured from the capacitive load, current i.sub.p1 of the
power generation system has a pulse-shaped waveform in which a
sharp peak appears for a short period of time. In some cases,
detection precision in the flow of the commercial side power is
higher in the use of decision value V3 or decision value V4 to be
the integrated value of current i.sub.p1 and current i.sub.c1 at
time that current i.sub.p1 of the power generation system reaches a
peak than the use of decision value V1 or decision value V2
obtained by integrating, for one cycle, the value calculated
through the multiplication of current i.sub.p1 and current
i.sub.c1.
[0122] In the case in which current i.sub.p1 and current i.sub.c1
cannot be measured at the same time for reason of a short sampling
interval or the like, it is also possible to calculate the decision
value by using current i.sub.p1 and current i.sub.c1 measured in
different cycles, for example.
[0123] In the case in which current i.sub.p1 and current i.sub.c1
are continuously measured, for example, decision value V5
calculated in accordance with the following equation (5) is
used.
[ Equation 3 ] D 5 = .intg. t = 0 t = T ip ( t ) .times. ic ( t +
nT ) t ( 5 ) ##EQU00003##
[0124] n in the equation (5) is set to be a natural number.
[0125] Decision value V5 is obtained by integrating, for one cycle,
a value calculated through multiplication of the instantaneous
value of current i.sub.p1 and an instantaneous value of current
i.sub.c1 with a delay of n cycles. In the same manner as in the
case in which decision value V1 is used, accordingly, it is
possible to decide that the power purchasing state is set with
decision value V5.gtoreq.0 and to decide that the power selling
state is set with decision value V5<0.
[0126] In the case in which current i.sub.p1 and current i.sub.c1
are discretely measured, for example, decision value V6 calculated
in accordance with the following equation (6) is used.
[ Equation 4 ] D 6 = k = 0 m ip [ k ] .times. ic [ n .times. m + k
] ( 6 ) ##EQU00004##
[0127] As shown in FIG. 9, decision value V6 is obtained by
integrating, for one cycle, a value calculated through
multiplication of the sampling value of current i.sub.p1 and a
sampling value of current i.sub.c1 with a delay of n cycles. In the
same manner as in the case in which decision value V1 is used,
accordingly, it is possible to decide that the power purchasing
state is set with decision value V6.gtoreq.0 and to decide that the
power selling state is set with decision value V6<0.
[0128] Returning to FIG. 3, in step S4, power calculator 134
calculates power of each unit. Specifically, power calculator 134
calculates generated power P.sub.p in accordance with the following
equation (7) if power generated from solar power generation system
151 is represented by P.sub.p.
P.sub.p=vr.sub.p1.times.ir.sub.p1.times.PF.sub.p (7)
[0129] vr.sub.p1 represents an effective value of voltage v.sub.p1
and a nominal value of output voltage of solar power generation
system 151 is used, for example. For the use, a measured value of
the effective value of voltage v.sub.p1 may be acquired from solar
power generation system 151.
[0130] ir.sub.p1 represents an effective value of current i.sub.p1
which is calculated based on a measured value of current
i.sub.p1.
[0131] PF.sub.p represents the power factor of the power generation
system and is a constant set based on an experimental result, an
actual measurement result, a theoretical equation or the like, for
example.
[0132] In the case in which it is decided that the power purchasing
state is set when purchased power is represented by P.sub.cb and
sold power is represented by P.sub.cs, power calculator 134
calculates purchased power P.sub.cb and sold power P.sub.cs in
accordance with the following equations (8) and (9).
P.sub.cb=vr.sub.c1.times.ir.sub.c1.times.PF.sub.c (8)
P.sub.cs=0 (9)
[0133] vr.sub.c1 represents an effective value of voltage v.sub.c1
and nominal voltage of commercial power supply 152 is used, for
example. The output voltage of solar power generation system 151 is
controlled to be equal to the voltage of commercial power supply
152. For this reason, the measured value of the effective value of
voltage v.sub.p1 may be acquired from solar power generation system
151 and thus used as voltage vr.sub.c1.
[0134] ir.sub.c1 represents an effective value of current i.sub.c1
which is calculated based on a measured value of current
i.sub.c1.
[0135] PF.sub.c represents the power factor of the commercial power
system and is a constant set based on an experimental result, an
actual measurement result, a theoretical equation or the like, for
example.
[0136] On the other hand, if it is decided that the power selling
state is set, power calculator 134 calculates purchased power
P.sub.cb and sold power P.sub.cs in accordance with the following
equations (10) and (11).
P.sub.cb=0 (10)
P.sub.cs=vr.sub.c1.times.ir.sub.c1.times.PF.sub.c (11)
[0137] A right side of equation (8) is equal to that of equation
(11).
[0138] If it is decided that the power purchasing state is set,
power calculator 134 calculates load power P.sub.I of load 153 in
accordance with the following equation (12).
P.sub.I=vr.sub.c1.times.(ir.sub.p1+ir.sub.c1).times.PF.sub.I
(12)
[0139] PF.sub.I represents the power factor of the load power
system and is a constant set based on an experimental result, an
actual measurement result, a theoretical equation or the like, for
example.
[0140] On the other hand, if it is decided that the power selling
state is set, power calculator 134 calculates load power P.sub.I of
load 153 in accordance with the following equation (13).
P.sub.I=vr.sub.c1.times.(ir.sub.p1-ir.sub.c1).times.PF.sub.I
(13)
[0141] Then, power calculator 134 gives a notice of a calculated
value of the power of each unit to display 123 and communicator
124.
[0142] In step S5, display 123 displays the power state of each
step. For example, display 123 displays generated power P.sub.p,
sold power P.sub.cs, purchased power P.sub.cb and load power
P.sub.I which are calculated by using a numerical value, a time
series graph or the like. For example, display 123 displays whether
the power purchasing state or the power selling state is set in a
character, a symbol, an icon or the like over a screen or carries
out indication through lighting, flashing, a color variation or the
like by means of an LED etc.
[0143] Consequently, a user can grasp the power state of each unit
in a home.
[0144] In step S6, communicator 124 gives a notice of the power
state of each unit. Specifically, communicator 124 transmits, to an
external device, power state information including generated power
P.sub.p, sold power P.sub.cs, purchased power P.sub.cb and load
power P.sub.I which are calculated, and whether the power
purchasing state or the power selling state is set.
[0145] The external device to be a transmitting destination stores
received information and analyzes a use situation of power or the
like based on the received information, for example.
[0146] Furthermore, the measured values of current i.sub.p1 and
current i.sub.c1 may be included in the power state information.
Moreover, all of the information do not always need to be
transmitted but the information to be transmitted may be selected
depending on necessity of the device to be the transmitting
destination, for example.
[0147] In addition, the transmission of the power state information
does not always need to be performed by loop process for power
monitor processing every time but is preferably carried out in a
predetermined timing every predetermined period or when a storage
amount of information exceeds a predetermined amount, for example.
Alternatively, the power state information may be transmitted
according to a request given from the external device.
[0148] Then, the processing returns to step S1 and processing after
step S1 is executed.
[0149] As described above, it is possible to detect the flow of the
commercial side power by simply installing only current
transformers 111p and 111c in the power system and measuring
current i.sub.p1 and current i.sub.c1 without disposing a voltage
measuring unit in the power system. Moreover, it is possible to
measure the generated power, the sold power, the purchased power
and the consumed power.
[0150] Therefore, it is possible to install power monitoring system
101 safely without a power failure, to easily provide power
monitoring system 101, and furthermore, to reduce necessary cost.
As a result, it is possible to detect the power state easily at low
cost. By omitting a high voltage measuring unit which greatly
requires safety and reliably, furthermore, it is possible to
enhance the safety and reliability of the whole power monitoring
system 101.
2. Variant
[0151] Although the description has been given to the example in
which the present invention is applied to the single phase two-wire
type power system, the present invention can also be applied to a
power system of a single phase three-wire type.
[0152] FIG. 10 shows an example of a method of installing a current
transformer in the case of the single phase three-wire type. As
shown in FIG. 10, it is preferable to provide two current
transformers including current transformer 251 and current
transformer 252 between voltage line L1 and neutral line N (which
is hereinafter referred to as an L1 phase) and between voltage line
L2 and neutral line N (which is hereinafter referred to as an L2
phase), respectively.
[0153] In the case of the single phase three-wire type, when
current i.sub.p1 and current i.sub.p1 are to be measured discretely
and serially, it is preferable to continuously measure current
having the same phase in order of current i.sub.p1 having an L1
phase, current i.sub.p1 having the L1 phase, current i.sub.p1
having an L2 phase, current ip.sub.1 having the L2 phase, for
example.
[0154] Although the description has been given to the example in
which the value obtained by the multiplication of current i.sub.p1
and current i.sub.c1 is integrated for one cycle when decision
values V1, V2, V5 and V6 are to be calculated, it is also possible
to carry out the integration for n cycles (n is a natural number of
two or more).
[0155] Furthermore, the installing directions of current
transformers 111p and 111 c are not restricted to the above example
but can be set to optional directions. In the case in which only
one of current transformers 111p and 111c is installed in a reverse
direction to that in the above example, a decision result of the
flow of the commercial side power is reverse to that in the above
example.
[0156] Although the values of voltage v.sub.p2 and voltage v.sub.c2
are converted into the values of current i.sub.p1 and current
i.sub.c1 and the decision value is then calculated in the above
description, moreover, it is also possible to calculate the
decision value by directly using voltage v.sub.p2 and voltage
v.sub.c2. In this case, it is basically sufficient to simply
replace current i.sub.p1 and current i.sub.c1 in the equations (1)
to (6) with voltage v.sub.p2 and voltage v.sub.c2.
[0157] In power monitoring system 101, furthermore, the power
factor of current i.sub.p1 is minimized immediately before solar
battery module 161 starts power generation or immediately after it
ends the power generation in some cases. For example, FIG. 11 shows
an example of a transition for the effective value of current
i.sub.p1 before or after solar battery module 161 starts the power
generation in the morning. A portion surrounded by a circle in FIG.
11 illustrates a time zone immediately before the start of the
power generation by solar battery module 161. As in this example,
current i.sub.p1 flows regardless of no power generation of solar
battery module 161 in some cases. At this time, current i.sub.p1 is
mainly generated due to flow of current into a capacitive load such
as a capacitor in PV controller 162, and a phase is greatly
different from that of current i.sub.p1 in the power generation of
solar battery module 161.
[0158] On the other hand, FIG. 12 shows an example of a transition
for the effective value of current i.sub.p1 before or after solar
battery module 161 stops the power generation in the evening. A
portion surrounded by a circle in FIG. 12 illustrates a time zone
immediately after the stop of the power generation by solar battery
module 161. As in this example, current i.sub.p1 flows regardless
of no power generation of solar battery module 161 in some cases.
At this time, current i.sub.p1 is also generated mainly due to flow
of current into a capacitive load such as a capacitor in PV
controller 162, and a phase is greatly different from that of
current i.sub.p1 in the power generation of solar battery module
161.
[0159] In the time zones surrounded by the circles in FIGS. 11 and
12, thus, current i.sub.p1 having a greatly different phase from
that in the power generation of solar battery module 161 flows.
Consequently, there is a fear that the flow of the commercial side
power might be detected reversely to an actual flow. In other
words, although solar battery module 161 does not generate power,
it is decided that the flow of the commercial side power is set
into the power selling state. Although the power is purchased from
commercial power supply 152, there is a fear that the power might
be decided to be sold. If this is caused when high power is
consumed by load 153 and a large amount of power is purchased from
commercial power supply 152, for example, considerable deviation
occurs in a result of the calculation of the sold power and the
purchased power.
[0160] FIG. 13 shows an example of a structure of power monitoring
system 301 which prevents erroneous detection in the flow of the
commercial side power. In FIG. 13, corresponding portions to FIG. 1
have the same reference numerals and portions subjected to the same
processing are properly omitted because the explanation is
repeated.
[0161] Power monitoring system S301 is different from power
monitoring system 101 in FIG. 1 in that detecting device 311 is
provided in place of detecting device 112. Detecting device 311 is
different from detecting device 112 in that arithmetic unit 321 is
provided in place of arithmetic unit 122.
[0162] Arithmetic unit 321 is different from arithmetic unit 122 in
that flow detector 331 is provided in place of flow detector
133.
[0163] Flow detector 331 detects a flow on the commercial side
power based on the measured values of current i.sub.p1 and current
i.sub.c1 in addition to a decision value calculated by decision
value calculator 132, and gives a notice of a detected result to
power calculator 134.
[0164] With reference to a flowchart of FIG. 14, description is
given to a first embodiment of power monitor processing to be
executed by power monitoring system 301. This processing is started
when a power supply of power monitoring system 301 is turned ON and
is ended when the power supply is turned OFF, for example.
[0165] The processing of steps S101 to S103 are the same as those
of steps S1 to S3 of FIG. 3. In other words, current i.sub.p1 and
current i.sub.c1 are measured and a decision value is calculated,
and a flow of commercial side power is decided based on the
decision value.
[0166] In step S104, flow detector 331 decides whether a result of
the decision in the processing of step S103 is set into the power
selling state or not. If it is decided that the result of the
decision is set into the power selling state, the processing
proceeds to step 3105.
[0167] In step S105, flow detector 331 decides whether the current
of the commercial power system is larger than the current of the
power generation system or not. In other words, if flow detector
331 compares the effective value of current i.sub.c1 with that of
current i.sub.p1 and decides that the effective value of current
i.sub.c1 is greater, the processing proceeds to step S106.
[0168] In step S106, flow detector 331 corrects the flow into the
power purchasing state. In other words, in the power selling state
of the flow and in a state in which the effective value of current
i.sub.c1 is greater than that of current i.sub.p1, higher power
than the power generation amount of solar power generation system
151 is supplied to commercial power supply 152 side. This state
cannot really occur. For this reason, flow detector 331 decides
that erroneous detection in the flow of commercial side power
occurs, and corrects the result of the detection in the flow from
the power selling state to the power purchasing state. Then, flow
detector 331 gives a notice of the corrected flow to power
calculator 134.
[0169] Thereafter, the processing proceeds to step S107.
[0170] On the other hand, if it is decided that the effective value
of current i.sub.c1 is equal to or smaller than the effective value
of current i.sub.p1 in step S105, the processing of step S106 is
skipped so that the flow is not corrected and the processing
proceeds to step S107. At this time, flow detector 331 gives power
calculator 134 a notice of the flow decided in the processing of
step S103.
[0171] If it is decided that the decision result is the power
purchasing state in step S104, moreover, the processing of steps
S105 and S106 is skipped and the processing proceeds to step S107.
At this time, flow detector 331 gives power calculator 134 a notice
that the flow is set into the power purchasing state.
[0172] In steps S107 to S109, subsequently, the same processing as
those of steps S4 to S6 in FIG. 3 are executed and the processing
then returns to step S101, and the processing after step S101 are
executed.
[0173] FIG. 15 is a graph indicative of a condition for deciding
that the power selling state is set in the processing of FIG. 14.
In FIG. 15, it is supposed that the effective value of current
i.sub.p1 is set to be positive when phase difference .phi.p-.phi.c
between current i.sub.p1 and current i.sub.c1 is
.pi./2<|.phi.p-.phi.c|.ltoreq..pi. (that is, the decision value
<0) and the effective value of current i.sub.p1 is set to be
negative when phase difference .phi.p-.phi.c between current
i.sub.p1 and current i.sub.c1 is |.phi.p-.phi.c|.ltoreq..pi./2
(that is, the decision value.gtoreq.0). Moreover, a slanted line
part in FIG. 15 indicates a region decided to be set into the power
selling state and the other parts indicate a region decided to be
set into the power purchasing state.
[0174] As shown in FIG. 15, the power selling state is decided to
be set with 0<the effective value of current i.sub.c1.ltoreq.the
effective value of current i.sub.p1, and the power purchasing state
is decided to be set in the other cases. In other words, even if
the decision value <0 is obtained, the power selling state is
not decided to be set but the power purchasing state is decided to
be set without the effective value of current i.sub.c1.ltoreq.the
effective value of current i.sub.p1. In other words, when a
calculated value of the sold power is greater than that of the
generated power even if the power selling state is decided to be
set based on the decision value, the power purchasing state is
decided to be set.
[0175] On the other hand, if the decision value 0 is obtained, the
power purchasing state is decided to be set regardless of the
relationship between current i.sub.c1 and current i.sub.p1 in the
same manner as the processing of FIG. 3.
[0176] With reference to a flowchart of FIG. 16, next, description
is given to a second embodiment of the power monitor processing to
be executed by power monitoring system 301. This processing is
started when a power supply of power monitoring system 301 is
turned ON and is ended when the power supply is turned OFF, for
example.
[0177] In step S201, current i.sub.p1 and current i.sub.c1 are
measured in the same manner as the processing of step S1 in FIG.
3.
[0178] In step S202, flow detector 331 decides whether the current
of the power generation system is equal to or smaller than a
specified value or not. In other words, if flow detector 331
compares the effective value of current i.sub.p1 with a
predetermined specified value and decides that the effective value
of current i.sub.p1 is greater than the specified value, the
processing proceeds to step S203.
[0179] The specified value is set to be a value with which the flow
is decided stably, for example, a value which is ten times as great
as a detection limit of the current.
[0180] In step S203, the decision value is calculated in the same
manner as the processing of step S2 in FIG. 3. In step S204, the
flow of the commercial side power is decided in the same manner as
the processing of step S3 in FIG. 3.
[0181] In step S205, it is decided whether the decision result is
set into the power selling state or not in the same manner as the
processing of step S104 in FIG. 14. If it is decided that the
decision result is the power selling state, the processing proceeds
to step S206.
[0182] In step S206, flow detector 331 decides whether the current
of the commercial power system is larger than that of the power
generation system or not. At this time, flow detector 331 decides
that the current of the commercial power system is larger than the
current of the power generation system when the following equation
(14) is satisfied differently from the processing of step S105 in
FIG. 14, for example.
Effective value of current i.sub.c1>a.times.effective value of
current i.sub.p1+b (14)
[0183] The constant a is equal to or greater than one and is set
based on an assumed value of a gain error in measuring units 121p
and 121c, converter 131 or the like, for instance. Moreover, the
constant b is equal to or greater than zero and is set based on an
assumed value of a noise error in measuring units 121p and 121c,
converter 131 or the like, for example.
[0184] Consequently, the relationship between the current of the
commercial power system and that of the power generation system can
be decided more accurately in consideration of the gain error or
the noise error.
[0185] If it is decided that the current of the commercial power
system is larger than that of the power generation system, the
processing proceeds to step S207.
[0186] In step S206, it is also possible to use the same deciding
method as that in step S105 of FIG. 14. To the contrary, in step
S105 of FIG. 14, it is also possible to use the same deciding
method as that of step S206.
[0187] In step S207, the flow is corrected into the power
purchasing state in the same manner as the processing of step S106
in FIG. 14, and the corrected flow is given as a notice to power
calculator 134. Then, the processing proceeds to step S209.
[0188] On the other hand, if it is decided that the current of the
commercial power system is equal to or smaller than that of the
power generation system in step S206, the processing of step S207
is skipped and the flow is not corrected, and the processing
proceeds to step S209. At this time, flow detector 331 gives power
calculator 134 a notice of the flow decided in the processing of
step S204.
[0189] If it is decided that the decision result is the power
purchasing state in step S205, moreover, the processing of steps
S206 and S207 is skipped and the processing proceeds to step S209.
At this time, flow detector 331 gives power calculator 134 a notice
that the flow is set into the power purchasing state.
[0190] If it is decided that the effective value of current
i.sub.p1 is equal to or smaller than the specified value in step
S202, furthermore, the processing proceeds to step S208.
[0191] In step S208, flow detector 331 decides that the flow is set
into the power purchasing state. In other words, if the effective
value of current i.sub.p1 is equal to or smaller than the specified
value, it is decided that the flow is set into the power purchasing
state regardless of the decision value. Then, flow detector 331
gives power calculator 134 a notice that the flow is set into the
power purchasing state. Thereafter, the processing proceeds to step
S209.
[0192] Consequently, it is possible to prevent the flow from being
erroneously detected as the power selling state when current
i.sub.p1 takes a minimum value, for example, around 6:45 and around
17:35 at an edge of the time zone surrounded by the circles in
FIGS. 11 and 12.
[0193] On the other hand, in the case in which the power generation
amount of solar battery module 161 is small and current i.sub.p1 is
small, there is a possibility that the power purchasing state might
be detected erroneously regardless of the flow in the power selling
state. However, excess power is generated when the power generation
amount of solar battery module 161 is small, the power selling
state is rarely set. Consequently, there is a very low possibility
that the erroneous detection might occur. Even if the erroneous
detection occurs, moreover, it is supposed that influence of the
erroneous detection is very small because the amount of power is
small.
[0194] Then, the same processing as those in steps S4 to S6 in FIG.
3 are executed in steps S209 to S211 and the processing thereafter
returns to step S201, and the processing after step S201 are
executed.
[0195] FIG. 17 is the same graph as FIG. 15 and shows a condition
for deciding that the power selling state is set in the processing
of FIG. 16. A slanted line part in FIG. 17 indicates a region
decided to be set into the power selling state, and the other
portions indicate a region decided to be set into the power
purchasing state.
[0196] As shown in FIG. 17, it is decided that the power selling
state is set if 0<effective value of current
i.sub.c1.ltoreq.a.times.effective value of current i.sub.p1+b and
effective value of current i.sub.p1>specified value c are taken,
and it is decided that the power purchasing state is set in the
other cases.
[0197] In other words, also when the decision value <0 is
obtained, the power selling state is not decided to be set but the
power purchasing state is decided to be set if neither
0<effective value of current i.sub.c1.ltoreq.a.times.effective
value of current i.sub.p1+b nor effective value of current
i.sub.p1>specified value c are taken. In other words, also in
the case in which the power selling state is decided to be set
based on the decision value, the power purchasing state is decided
to be set when the calculated value of the sold power is greater
than the calculated value of the generated power+an error or the
effective value of current i.sub.p1 is equal to or smaller than the
specified value c.
[0198] On the other hand, if the decision value.gtoreq.0 is
obtained, the power purchasing state is decided to be set
regardless of the relationship between current i.sub.c1 and current
i.sub.p1 in the same manner as the processing of FIG. 3.
[0199] In the embodiment according to the present invention,
moreover, it is possible to employ a private power generator of an
optional type, for example, wind power generation, diesel power
generation, a fuel cell or the like in addition to the solar power
generation.
[0200] In addition, the present invention can be applied to power
systems of various facilities including private power generators,
for example, a building, a factory, commercial facilities, public
facilities and the like in addition to ordinary homes.
[0201] [Example of Structure of Computer]
[0202] The above serial processing of detecting devices 112 and 311
can also be executed by hardware or software. In the case in which
the serial processing are executed by software, a program
constituting the software is installed into a computer. The
computer includes a computer incorporated in dedicated hardware, a
general-purpose personal computer capable of executing various
functions by installing various programs and the like, for
example.
[0203] FIG. 18 is a block diagram showing an example of a structure
of hardware in a computer configured to execute the serial
processing in accordance with a program.
[0204] In the computer, CPU (Central Processing Unit) 401, ROM
(Read Only Memory) 402 and RAM (Random Access Memory) 403 are
connected mutually through bus 404.
[0205] Input/output interface 405 is further connected to bus 404.
Input unit 406, output unit 407, storage unit 408, communicator 409
and drive 410 are connected to input/output interface 405.
[0206] Input unit 406 is configured from a keyboard, a mouse, a
microphone and the like. Output unit 407 is configured from a
display, a speaker and the like. Storage unit 408 is configured
from a hard disk, a nonvolatile memory and the like. Communicator
409 is configured from a network interface and the like. Drive 410
drives removable media 411 such as a magnetic disk, an optical
disk, a magneto-optical disk or a semiconductor memory.
[0207] In the computer having the structure described above, CPU
401 loads a program stored in storage unit 408 into RAM 403 through
input/output interface 405 and bus 404 and executes the program,
for example. Thus, the above serial processing are carried out.
[0208] The program to be executed by the computer (CPU 401) can be
recorded in removable media 411 serving as package media and can be
thus offered, for example. Moreover, the program can be provided
through cable or wireless transmission media such as a local area
network, internet or digital satellite broadcasting.
[0209] In the computer, the program can be installed into storage
unit 408 through input/output interface 405 by attachment of
removable media 411 to drive 410. Moreover, the program can be
received by communicator 409 through the cable or wireless
transmission media and can be thus installed into storage unit 408.
In addition, the program can be previously installed into ROM 402
and storage unit 408.
[0210] The program to be executed by the computer may be a program
to be processed in time series in order described in this
specification or may be a program to be processed in parallel or in
a necessary timing when calling is performed.
[0211] In this specification, moreover, it is assumed that the
terms of the system imply a whole apparatus configured from
devices, units and the like.
[0212] Furthermore, the embodiment according to the present
invention is not restricted to the embodiments described above but
various changes can be made without departing from the gist of the
present invention.
* * * * *