U.S. patent application number 11/954219 was filed with the patent office on 2008-06-19 for maximum power point tracking system for the solar-supercapacitor power device and method using same.
Invention is credited to Ming-Hsin Sun.
Application Number | 20080141998 11/954219 |
Document ID | / |
Family ID | 39525646 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080141998 |
Kind Code |
A1 |
Sun; Ming-Hsin |
June 19, 2008 |
MAXIMUM POWER POINT TRACKING SYSTEM FOR THE SOLAR-SUPERCAPACITOR
POWER DEVICE AND METHOD USING SAME
Abstract
A maximum power point tracking system, named flash
supercapacitor-solar power device, and method for a solar power
system, which mainly adds a pulse-power supercapacitor for being
operated in a dynamic equilibrium are disclosed. The duty ratio D
is changed and the voltage variance of the supercapacitor is
observed to determine the next adjusting direction of the duty
ratio D of the DC/DC converter. In the present invention, only a
voltage value of the supercapacitor is needed to be monitored and
no current-detection is needed. The output power of the solar power
system can be actually estimated. The maximum power is traced in an
oscillatory way. Therefore, the operation process of the
perturbation and observation method, which is generally implemented
currently, is simplified. By utilizing the steady-state equilibrium
of the supercapacitor, only the voltage of the supercapacitor needs
to be detected, and there is no need to measure and calculate the
voltage and current values. The system is simple and easily
accessible, which is a maximum power point tracking system and
method with high efficiency for a solar power system.
Inventors: |
Sun; Ming-Hsin; (Hsinchu
County, TW) |
Correspondence
Address: |
Ming-Hsin Sun
235 Chung - Ho, Box 8-24
Taipei
omitted
|
Family ID: |
39525646 |
Appl. No.: |
11/954219 |
Filed: |
December 12, 2007 |
Current U.S.
Class: |
126/601 |
Current CPC
Class: |
G05F 1/67 20130101 |
Class at
Publication: |
126/601 |
International
Class: |
F24J 2/38 20060101
F24J002/38 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2006 |
TW |
095147546 |
Claims
1. A maximum power tracking point method applied to an solar power
system comprising the steps of adding an pulse-power
supercapacitor. operated in a dynamic equilibrium; changing a duty
ratio of a DC/DC converter; and observing a voltage variance of
said supercapacitor for determining a next adjusting manner of said
duty ratio of said DC/DC converter, wherein only a voltage value of
said supercapacitor is needed to be monitored and no
current-detection is needed for calculating an output power of said
solar power system, and tracking a maximum power point in an
oscillatory way.
2. The maximum power tracking point method of claim 1, comprising
the following steps of: (a) detecting an original voltage value of
said pulse-power supercapacitor; (b) when said voltage value of
said pulse-power supercapacitor exceeds a pre-set value, activating
a maximum power point tracking system; (c) adjusting said duty
ratio of said DC/DC converter; (d) detecting a new voltage value of
said pulse-power supercapacitor; (e) comparing said original and
new voltage values of said pulse-power supercapacitor; (f) in case
that said new voltage value is higher than said first voltage
value, adjusting said duty ratio of said DC/DC converter in a trend
toward an original variation direction of said duty ratio; (g) in
case that said second voltage value is lower than said original
voltage value, adjusting said duty ratio of said DC/DC converter in
a trend reverse to said original variation direction of said duty
ratio; and (h) repeating said steps (a)-(g) in sequence.
3. The maximum power tracking point method of claim 1, wherein said
pulse-power supercapacitor is selected from various high
energy-density and high power-density supercapacitors, ruthenium
dioxide supercapacitors, carbon supercapacitors, metal oxide
supercapacitors, polymer supercapacitors, gold capacitors, and
aluminum electrolytic capacitors having high capacities.
4. The maximum power tracking point of claim 1, wherein said DC/DC
converter is a step-up converter, a step-down converter, a
step-up/step-down converter, or any other similar converter.
5. The maximum power tracking point method of claim 1, wherein
solar energy inputted into/outputted from said pulse-power
supercapacitor is in a dynamic equilibrium state, and said solar
energy is transferred to said DC/DC converter; an output voltage of
said photovoltaic panel and an input energy of said pulse-power
supercapacitor are changed by adjusting said duty ratio of said
DC/DC converter; the voltage value of said pulse-power
supercapacitor serves as an energy characteristic of said
pulse-power supercapacitor and is measured and compared at
different times for observing an output energy change trend of said
photovoltaic panel, so as to track a maximum power point of said
solar power system.
6. The maximum power tracking point method of claim 1, wherein when
an intensity of a sunshine is strong, said pulse-power
supercapacitor undergoes a maximum power point tracking; when said
intensity of said sunshine is weak or it is in a worse weather that
only a weak solar energy generates, said supercapacitor accumulates
weak electric energy transferred from said weak solar energy and
charges a accumulator when accumulated energy become higher,
wherein said pulse-power supercapacitor serves as an energy
accumulator of said weak electric energy.
7. The maximum power tracking point method of claim 6, wherein a
charging mode of said accumulator is based on a detected voltage of
said accumulator, undergoing a pulse charging in an initial period,
a full-speed charging in a middle period, and a pulse charging in
an ending period, wherein in said full-speed charging, said
electric energy generated by solar energy system is totally charged
into said accumulator.
8. The maximum power tracking point method of claim 6, wherein said
charging mode can be replaced by a normal charging mode such as a
constant current charging, a constant voltage charging, a constant
power, a two/three stages charging, or a speed charging.
9. The maximum power tracking point method of claim 6, wherein said
steps of charging said accumulator include an
intelligent-adjustable discharging step in which an output of said
accumulator is set in an adjustable constant current, an adjustable
constant voltage or an adjustable constant power for driving a
load.
10. The maximum power tracking point method of claim 9, wherein in
said discharging mode, said accumulator is controlled by a logic
control circuit through a DC/DC step-up/step-down converter to keep
a constant output which is not influenced when the voltage of said
accumulator is reduced and said constant output can be raised to
strengthen power outputted to said load.
11. The maximum power tracking point method of claim 10, wherein
when said accumulator is going to be full-charged by said
discharging step and there is still solar energy converted, said
pulse-power supercapacitor will serve as a second accumulator for
outputting power to said load without passing through said
accumulator.
12. A maximum power tracking point method applied to a solar power
system comprising: a photovoltaic panel; a pulse-power
supercapacitor, which is a dynamic-equilibrium energy-storing
device for receiving energy outputted from said photovoltaic panel
and outputting electric energy to a DC/DC converter; said DC/DC
converter, which is capable of adjusting an output voltage and
energy of said solar power system; and a pulse width modulation
driver for delivering pulse signal to control said DC/DC
converter.
13. The maximum power tracking point method of claim 12, wherein
said photovoltaic panel is constructed by a plurality of
photovoltaic units connected in serial/parallel as needed; and
wherein said DC/DC converter is a step-up converter a step-down
converter, a step-up/step-down converter or any other similar
converter.
14. (canceled)
15. The maximum power tracking point method of claim 12, wherein
said pulse-power supercapacitor is electrically connected to a
logic control circuit which is electrically connected to a
voltage/circuit guard circuit.
16. The power tracking method of claim 15, wherein said
voltage/current circuit is connected to an accumulator electrically
connected to a load for preventing said load from a damage caused
by over charging/discharging of said accumulator.
17. The power tracking method of claim 16, wherein said load is
selected from an LED array, a lamp, a mechanical device, a
monitoring equipment, a detecting apparatus, and a
signal-communicator, and said load is further connected to a
current detector for detecting a current on said load.
18. The maximum power tracking point power tracking method of claim
16, wherein said accumulator is a Lead-acid storage battery, or a
rechargeable battery selected from a Nickel-Cadmium battery, a
Nickel-Metal Hydride battery, a Lithium-ion battery, a
Lithium-polymer battery, and a Lead-acid storage battery.
19. The maximum power tracking point method of claim 1, wherein
said photovoltaic panel is connected to a first electric switch,
said first electric switch is electrically connected to said DC/DC
converter, and said DC/DC converter is electrically connected to a
second electric switch.
20. The maximum power tracking point method of claim 19, wherein
said first and second electric switches are semiconductor electric
switches which include higher operational speed than analog
switches; and wherein said logic control circuit is a
microcontroller or a microcontroller-like controller.
21. (canceled)
22. The maximum power tracking point method of claim 15, further
comprising a current detector for detecting a current of said load
and generating a detecting signal transmitted to said logic control
circuit through said voltage/current guard circuit for controlling
a current outputted from a battery to said load.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a novel maximum power
tracking point device and method for the solar power system, and
more particularly to a system and method for utilizing solar energy
to generate electricity.
BACKGROUND OF THE INVENTION
[0002] Due to the highly-developing industry and
hurriedly-increased population, the energy resources on earth are
consumed with unprecedented speed. It is expectable that some
energy resources, which prop up human civilization in recent
hundreds years, will be exhausted within the coming generations.
The petroleum on earth may run out in 40-50 years, while the
generation of natural gas can last only 60 years and the mineral
resources of uranium can only support the use for about 70 years.
Even for coal mine, which is estimated to last longer, the period
should be no more than about 200 years. Such finite energy
resources are not nearly enough for the endlessly developing human
civilization in the future. Accordingly, the exploitation of
alternative energy sources is of great urgency and necessity, and
renewable energy is exactly what human beings aspire to.
[0003] The use of most renewable energies is limited to special
regions; only the solar energy can be applied in most general
conditions and can be scaled-down in applications. The applications
of solar energy are advantaged in (1) being safe, reliable,
low-noisy, and non-pollutant; (2) causing no greenhouse gas (3)
gaining energy anywhere, without consuming fuel and using moving
mechanical parts; (4) easy maintenance, long life-time, short
installing period, and flexible scale; (5) no need of security
guard and installation of power-supply cables; (6) low cost in
remote districts; and (7) convenient combination with buildings.
Therefore, much of energy providers' attention has come to solar
energy.
[0004] The solar energy photoelectric transform can roughly be
divided into three types: photovoltaic cells, solar radiation, and
solar-decomposed water serving as the fuel for electric power
generations. Wherein, the solar radiation applications are most
economic for large-scaled power generations, and photovoltaic cells
(solar cells) are preferably using in the medium/small-scaled
applications. Solar cells are made of the semiconductor. The
sunshine lighting on the solar cell forms current on the
semiconductor surface. The current is stored as a DC power or
converted into an AC power being connected to an AC grid in
parallel.
[0005] The critical techniques of the photovoltaic power are (A)
solar cell/photovoltaic panel; (B) tracking and obtaining of the
maximum power points; 15 (C) technique for charging the battery;
and (D) technique for the solar system discharging. The solar cells
are made by semiconductor processes. Generally speaking, there are
single crystal, polycrystalline, and amorphous solar cells.
Furthermore, much recent interest has been directed towards the
development of flexible or organic solar cells. The maximum
conversion efficiency of the current commercial photovoltaic panel
is below 18%. The tracking and obtaining of the maximum power point
is the most concerted critical technology which needs to be
improved urgently. The most important energy-storage medium for the
medium/small solar power energy system and the islanding operation
of a large-scaled solar power system is the accumulator (battery).
In the solar power applications, the accumulator charging technique
is critical and necessary. On the other hand, the system
discharging technique is getting more important since the
requirement of the user to the quality of the discharging of the
solar energy system becomes higher.
[0006] The solar energy is nevertheless not a perfect renewable
energy. The electric power generated by the solar power system will
change according to the variances of the sunshine surroundings, the
sunshine angle, and the temperature. That is to say, the solar
energy is a variable renewable energy. The solar power generated at
different time may be different to varied sunshine. Therefore, a
maximum power point tracking (MPPT) method must be applied to
obtain the maximum electric power of a solar cell. Normally, the
electric power is indicated by the voltage and current. Therefore,
these variables are often taken into consideration in the operation
of a solar energy system to track and obtain the maximum power.
[0007] There is not a linear relationship between the voltage and
the current of the solar cell while unique working curves may occur
in responding to different atmosphere surroundings with different
sunshine conditions and temperatures. As shown in FIG. 1, the
voltage/current curves respectively represent a strong sunshine
condition, a medium sunshine condition, and a weak sunshine
condition. Further refer to the power/voltage diagram of the
photovoltaic panel indicated in FIG. 2. It is shown that each of
the working curves has a maximum power point, which is the point
that the maximum power is obtained from the photovoltaic panel.
According to various maximum power point tracking techniques, the
voltage/current state for obtaining the maximum power, which has
different time points varied with different surrounding conditions,
is tracked so that the energy can be quickly obtained and input
into the system. The conventional maximum power point tracking
techniques include (A) voltage feedback method; (B) power feedback
method; (C) perturbation and observation method, (D) incremental
and conductance method; (E) line fitting method; and (F) real
measuring method.
[0008] The most common used method is the perturbation and
observation method. The system is as shown in FIG. 3. It is
advantaged in its simple structure and fewer measuring parameters.
Accordingly, this method is popularly used in the solar MPPT
system. The basic algorithm is to periodically increase or decrease
the resistance of the load 5 to change the terminal voltage of the
photovoltaic panel 1 and to track and calculate the output power 2.
Observe and compare the variance before and after the perturbation,
and then accordingly determine whether to increase or decrease the
resistance of the load 5 in the next period. If the output power
increases, adjust the load 5 at the same trend. On. the other hand,
if the output power decreases, change the variant direction of the
load 5 at the next period. According to such repeatedly oscillatory
perturbing and observing, a maximum power point of the solar cell
will be approached.
[0009] The important character of the "perturbation and
observation" MPPT method is to change the load of the output
terminal by controlling the duty ratio D of the DC/DC converter 4
so as to perturb the output power of the photovoltaic panel in an
oscillatory way, track and approach the maximum power point of the
solar cell. When the maximum power point is approached, the
oscillatory perturbing is not stopped and is still operated around
the maximum power point. Once the incident intensity, the
surrounding and the temperature of the sunshine are varied, the
maximum power point for the operation of the solar power system
will be changed accordingly, and the oscillatory perturbing will
response to the change immediately to initiate a new maximum power
point tracking.
[0010] The DC/DC converter is constructed by inductors, capacitors,
diodes, and electric switches. The DC/DC converter can be a
step-up, step-down, or step-up/step-down DC/DC converter, and a
pulse signal is provided in cooperated with a pulse width
modulation (PWM) device 3 or a pulse frequency modulation (PFM)
device. The load of the terminal is adjusted by controlling the
duty ratio so as to track the maximum power point.
[0011] The supercapacitors have excellent energy-storing ability,
and, when being applied to solar energy devices, are advantaged in
increased efficiency, long cycle life, maintain free, and extended
operation time, etc. The U.S. patent No. 2004/0183982 discloses a
solar energy charging system which utilizes a double-layered
capacitor (i.e. a supercapacitor) as an energy-storing device. The
solar system is adjusted and controlled by a DC/DC converter for
tracking the maximum power point. In many electric applications
such as the Real-Time Clock (RTC) reserving memory, and the solar
energy LED lamp, the supercapacitors have substituted for the
batteries. In the past, the energy density of the supercapacitors
is far below that of the battery, and thus is limited in the
energy-storing applications. However, in the recent years, the
energy density of the supercapacitors increases rapidly, and thus
the supercapacitors are implemented to substitute for batteries
even more popularly. Even the DC power-accumulating of the solar
power system are considered to utilize the supercapacitors,
especially in the maximum power point tracking. U.S. patent No.
2006/0312102 further discloses an efficient solar power system
charging to a supercapacitor circuit in the maximum power. It is
designed to perform both the maximum power point tracking and the
constant-current charging of a supercapacitor by one circuit.
Furthermore, the supercapacitors are roughly divided into the
energy-releasing type supercapacitors and the pulse-power type
supercapacitors. The former has a battery-like characteristic, and
is mainly used to store energy. Since the energy is stored in a
physical way, the life and reliability of the energy-releasing type
supercapacitors are far longer and higher than those of the
chemical batteries. The latter is used to provide a strong pulse
power. Its characteristic is similar to that of a capacitor with
enormous power density.
SUMMARY OF THE INVENTION
[0012] The primary object of the present invention is to provide a
novel maximum power point tracking method and device for the solar
power system, named "Peter perturbation-and-observation solar
energy maximum power point tracking method" and device, which is a
supercapacitor dynamic equilibrium method and able to be applied to
all solar power energy systems.
[0013] The present invention provides a pulse-power supercapacitor
electrically connected between a photovoltaic panel and a DC/DC
converter. The supercapacitor with low internal resistance and fast
response, servers as a steady-state input/output energy storing
device. Accordingly, a novel, instant and efficient solar energy
maximum power point tracking method is developed. Furthermore, an
intelligent coordinating solar power system is designed based on
this maximum power point tracking method.
[0014] Furthermore, the present invention provides a power tracking
method applied to an solar power system comprising the steps of
adding an pulse-power supercapacitor operated in a dynamic
equilibrium; changing a duty ratio of a DC/DC converter; and
observing a voltage variance of the said supercapacitor for
determining a next adjusting manner of the said duty ratio of the
said DC/DC converter, wherein only a voltage value of the
supercapacitor is needed to be monitored and no current-detection
is needed for calculating an output power of said solar power
system, and tracking a maximum power point in an oscillatory
way.
BRIEF DESCRIPTIONS OF DRAWINGS
[0015] The invention as well as a preferred mode of use, further
objectives and advantages thereof, will best be understood by
reference to the following detailed description of an illustrative
embodiment when read in conjunction with the accompanying drawings,
wherein:
[0016] FIG. 1 is a voltage-current diagram of a photovoltaic panel
exposed on sunlight with various intensities;
[0017] FIG. 2 is a power-voltage diagram of a photovoltaic panel
exposed on sunlight with various intensities;
[0018] FIG. 3 is a flow diagram of a conventional perturbation and
observation maximum power tracking method for a solar energy
system;
[0019] FIG. 4 schematically illustrates the flow and system
structure of the present invention;
[0020] FIG. 5 is a flowchart of a power tracking according to an
embodiment of the present invention; and
[0021] FIG. 6 schematically illustrates the system structure
according to another embodiment of the present invention.
DETAILED DESCRIPTIONS OF THE INVENTION
[0022] Normally, the output power P of the photovoltaic panel is
needed to be calculated in a perturbation and observation MPPT
method. If the power is not at the maximum point, the duty ratio of
the DC/DC converter is adjusted so as to change the resistance of
the load and thus vary the output of the photovoltaic panel. The
output power P of the solar power system is then be calculated
again. The two calculated output powers are compared to obtain the
power change situation, and then the duty ratio of the DC/DC
converter is adjusted accordingly. The process steps are repeated
to obtain the maximum power in an oscillatory way.
[0023] The primary process is shown in FIG. 5. The value of the
power P is indicated by the voltage and the current of the circuit.
Therefore, the values of the voltage V and the current I of the
system must be detected to calculate the power P: P=I.times.V.
[0024] As shown in FIGS. 4-6, in the present invention, the current
I is not necessary to be detected and only the voltage V needs to
be detected. In the method of the present invention, the
pulse-power supercapacitor 7 is disposed between the photovoltaic
panel 6 and the DC/DC converter 8 for serving as an electric energy
buffer. The electric energy is generated by the photovoltaic panel
6, inputted into the pulse-power supercapacitor 7, and then
outputted to the DC/DC converter 8. In a steady state, it can be
seen that the net electric energy inputted in/outputted from the
pulse-power supercapacitor 7 is zero, i.e. there is no electric
energy accumulated and lost in the supercapacitor. The energy
generated by the photovoltaic panel 6 totally flows into the DC/DC
converter 8, and a dynamic equilibrium is established (i.e. steady
state). [0025] Electric energy of the solar power system
W=P.times.t, wherein [0026] P: power [0027] t: time [0028]
therefore, W=I.times.V.times.t; [0029] if we eliminate the time
factor, i.e. let t-1 sec, then W=P=I.times.V.
[0030] At any moment, energy flowing into the pulse-power
supercapacitor 7=energy flowing out of the pulse-power
supercapacitor 7, i.e., the energy flowing from the photovoltaic
panel 6 into the pulse-power supercapacitor 7 is equal to the
energy flowing from the pulse-power supercapacitor 7 into the DC/DC
converter 8. The energy generated by the photovoltaic panel 6=The
energy flowing into the pulse-power supercapacitor 7=The energy
flowing out of the pulse-power supercapacitor 7=The energy flowing
into the DC/DC converter 8.
[0031] Therefore, the conventional perturbation and observation
method for tracking the maximum solar power can only detect the
power generated by the photovoltaic panel 6. In the present
invention, the same function can be performed by detecting the
energy or power of the pulse-power supercapacitor 7. The energy of
the pulse-power supercapacitor 7 is related to its electric
capacity:
W=1/2C.times.V.sup.2 [0032] W: energy of the pulse-power
supercapacitor 7, [0033] C: electric capacity of the pulse-power
supercapacitor 7, [0034] V: voltage of the pulse-power
supercapacitor 7.
[0035] Since the value of the electric capacity C of the
pulse-power supercapacitor 7 is a constant, the energy of the
pulse-power supercapacitor 7 can be indicated by the voltage of the
pulse-power supercapacitor 7. That is, when the voltage of the
pulse-power supercapacitor 7 is obtained, the energy of the
pulse-power supercapacitor 7 is thus known, and so is the power of
the photovoltaic panel. Since the method of the present invention
only has to detect the voltage of the pulse-power supercapacitor 7,
it is a simple and efficient method. The operation flowchart is
shown in FIG. 5 and explained below. [0036] (A) first detect the
voltage Vc of the pulse-power supercapacitor 7; when the voltage
value Vc exceeds a pre-set value, activate a maximum power point
tracking system; [0037] (B) change the duty ratio D of the DC/DC
converter 8; [0038] (C) detect the voltage again to obtain a new
Vc; (D) if the new Vc is higher than the original Vc, adjust the
duty ratio D of the DC/DC converter 8 in a trend toward the
original variant direction; if the new Vc is lower than the
original Vc, adjust the duty ratio D of the DC/DC converter 8 in a
trend toward a reverse direction of the original variant direction,
[0039] (E) reset the value of Vc as new Vc value; [0040] (F) repeat
the above-mentioned steps.
[0041] When the maximum power of the photovoltaic panel 6 is
obtained according to the method of the invention, the logic
control circuit 10A will determine the charging mode according to
the voltage situation of the accumulator 11. The accumulator 11 is
charged by the current/voltage adjusted by the DC/DC converter
8.
[0042] When the accumulator 11 is in a low voltage, it is charged
in a pulse-charging mode by the system until the voltage is above
the present voltage. The energy generated by the photovoltaic panel
6 on the instance is totally charged into the accumulator 11. In
the later stage of the charging, the accumulator 11 is charged to
be full in a pulse-charging mode. According to a three-stage
charging method, the charging is efficient, fast, and low energy
lost.
[0043] The present invention provides an intelligent adjustable
discharging mode. The discharging of the solar power system
according to the present invention is adjustable. The discharging
mode is determined by the logic control circuit 10A, and is
controlled by the DC/DC converter 8 to execute a constant
voltage/constant current/constant power discharging or other
discharging operations. The DC/DC converter 8 is capable of
changing the output condition of the accumulator.
[0044] The load 10 of the system can be a LED array, a lamp, a
mechanical device, a monitoring equipment, a detecting apparatus,
or a signal communicator, etc . . . . In case the load 10 is a LED
array, the constant current is needed to control the luminance. The
accumulator used for a solar power system is usually a 12V
lead-acid battery for storing energy and discharging. When the
accumulator is full-charged, the voltage is up to 16V, while the
utilizing voltage range is between 13.8V to 11V. When the LED is
driven by the accumulator 11, the driving current will vary because
of the variation of the voltage of the lead-acid battery. Hence,
the luminance of the LED will be getting darker. The constant power
of the intelligent adjustable discharging is capable of keeping a
constant luminance of the LED. The constant power control is
capable of keeping the serial current passing through the LED
constant, and thus preventing the streetlamp using the LED from
getting darker. In some other cases such as a mechanical device, a
monitoring equipment, or a detecting apparatus, the load 10 must
operate in a constant voltage. A constant voltage can stabilize an
operation of a machine. The system is capable of being discharging
in a constant voltage, and thus is efficient. Even more, the
constant voltage outputted to the load 10 can be turned higher.
[0045] In another embodiment of the present invention, a solar
energy device utilizing an intelligent solar energy
charging/discharging method based on the present invention is
provided. It can be applied on solar energy LED lamp sources such
as the solar street lights, the solar traffic signals lights, and
various solar lights.
[0046] Generally speaking, the system based on the present
invention is added with a pulse-power supercapacitor 7 for a
dynamic equilibrium operation. By changing a duty ratio D of a
DC/DC converter 8 and observing a voltage variance of the
pulse-power supercapacitor 7, a next adjusting manner of the duty
ratio D of the DC/DC converter 8 is determined. Accordingly, the
maximum power can be traced in an oscillatory way.
[0047] In this method, only the voltage of the pulse-power
supercapacitor 7 has to be monitored, and the current does not need
to be measured. The output power of the solar power system can be
actually estimated accordingly.
[0048] According to the concept, the present invention at least
includes a photovoltaic panel 6, a pulse-power supercapacitor 7, a
DC/DC converter 8, a logic control circuit 9, and a load 10.
[0049] The method of the invention includes the following steps of:
[0050] (a) detecting a voltage value of the pulse-power
supercapacitor 7; [0051] (b) when the voltage value of the
pulse-power supercapacitor 7 exceeds a pre-set value, activating a
maximum power point tracking system; [0052] (c) adjusting the duty
ratio D of the DC/DC converter 8; [0053] (d) detecting a new
voltage value of the pulse-power supercapacitor 7 again; [0054] (e)
comparing the new and original voltage values of the pulse-power
supercapacitor 7; [0055] (f) in case that the new voltage value is
higher than the original voltage value, adjusting the duty ratio D
of the DC/DC converter 8 in a trend toward an original variation
direction; [0056] (g) in case that the new voltage value is lower
than the original voltage value, adjusting the duty ratio D of the
DC/DC converter 8 in a trend toward an reverse variation direction
of the original variation direction; and [0057] (h) repeating steps
(a)-(g) in sequence.
[0058] According to the above-mentioned method of the present
invention, another novel intelligent coordinating solar power
system, named flash supercapacitor 7-solar power device, is
provided.
[0059] The flash supercapacitor 7-solar power device at least
includes a photovoltaic panel 6, a pulse-power supercapacitor 7, a
DC/DC step-up/step-down converter 8, an accumulator 11, a voltage
detector for pulse-power supercapacitor 7 and first electric switch
12, a logic control circuit 10A, a second electric switch 13, a
voltage/current guard circuit, a load 10, and a current detector.
The operation processes include generating the electric energy
through the photovoltaic transform of the photovoltaic panel;
executing a maximum power tracking through the pulse-power
supercapacitor 7 and the DC/DC converter 8; accumulating the solar
energy by charging the accumulator 11 in a three-stage-charging
controlled by the logic control circuit 10A; and driving the load
10 in an intelligent adjusting method at final. In case the load 10
is a LED array, it is driven by a constant current, voltage or
power stably. Accordingly, the luminance of the LED array will not
be getting darker due to a voltage variance of the accumulator
11.
[0060] The photovoltaic panel 6 of the present invention is a
photovoltaic unit array. The photovoltaic units can be connected in
serial/parallel according to desired output voltage/current. The
solar energy is transferred into electric power under sunshine in
various strengths.
[0061] Furthermore, according to the above descriptions, the
pulse-power supercapacitor 7 of the present invention is a
capacitor with low internal resistance and high capacity and is
capable of being an electric energy buffer. The pulse-power
supercapacitor 7, operated in a dynamic equilibrium and a steady
state, receives the electric energy outputted from the photovoltaic
panel 6 and outputs electric energy to the DC/DC converter 8. The
pulse-power supercapacitor 7 might be a metal-oxide supercapacitor,
a carbon supercapacitor, a polymer supercapacitor, a hybrid
supercapacitor, an aluminum electrolytic supercapacitor, or other
similar high-capacity capacitors.
[0062] Moreover, the DC/DC converter 8 of the present invention is
preferably a step-up converter 8 capable of adjusting the
resistance of the load 10 so as to change the output voltage of the
photovoltaic panel 6. The DC/DC converter 8 also might be a
step-down converter 8, a step-up/step-down converter 8, or any
other similar DC/DC converter 8.
[0063] In addition, a pulse signal is provided by a pulse width
modulator to control the duty ratio D of the DC/DC converter 8, so
as to adjust the output of the photovoltaic panel 8. The flash
supercapacitor 7-solar power system of the present invention is a
novel intelligent coordinating solar power system, which integrates
functions of the maximum power tracking, the three-stage-charging,
and the intelligent adjustable discharging.
[0064] The photovoltaic panel 6 of the present invention is a
photovoltaic unit array. The photovoltaic units can be connected in
serial/parallel according to desired output voltage/current. The
solar energy is transferred into electric power under sunshine in
various strengths. Furthermore, according to the above
descriptions, the pulse-power supercapacitor 7 of the present
invention is a capacitor with low internal resistance and high
capacity and is capable of being an electric energy buffer. The
pulse-power supercapacitor 7, operated in a dynamic equilibrium and
a steady state, receives the electric energy outputted from the
photovoltaic panel 6 and outputs electric energy to the DC/DC
converter 8. The pulse-power supercapacitor 7 can be a metal-oxide
supercapacitor, a carbon supercapacitor, a polymer supercapacitor,
a hybrid supercapacitor, an aluminum electrolytic supercapacitor,
or similar high-capacity capacitors. Besides, when the sunshine is
weak, the weak current can be accumulated to a strong current
before stored to the accumulator 11 or driving the load 10
directly.
[0065] When the sunshine is strong and the accumulator 11 is
full-charged or almost full-charged, it is inefficient to
accumulate the solar energy into the accumulator 11. In such a
situation, the electric energy of the supercapacitor is preferably
used for driving the load 10 directly. That is to say, the
supercapacitor serves as a second accumulator 11. Accordingly, the
designed capacity of the accumulator 11 of the solar power system
can be reduced and thus the cost of the system construction is also
reduced.
[0066] In the embodiment of the present invention shown in FIG. 6,
the DC/DC step-up/step-down converter 8 receives the signal from
the logic control circuit 10A to execute a maximum power point
tracking on the solar energy outputted by the supercapacitor. The
duty ratio D of the converter 8 is adjusted to obtain the maximum
power of the photovoltaic panel 6. The charging method applied in
the system of the present invention is an adjustable charging
method. Furthermore, in the discharging process, the DC/DC
step-up/step-down converter 8, under the control of the logic
control circuit 10A, has the accumulator 11 to drive the load 10 in
an intelligent adjustable way.
[0067] Moreover, the accumulator 11 is a secondary (rechargeable)
battery, and is preferably in the system a lead-acid battery. It
can also be a nickel-metal hydride (Ni-MH) battery or a lithium
battery. In this system, the accumulator 11 serves as the first
energy-storing device. The voltage detector of the pulse-power
supercapacitor 7 of the present invention and the first electric
switch 12 is connected among the photovoltaic panel 6, the
supercapacitor 7, and the DC/DC step-up/step-down converter 8, and
is controlled to be switched by the logic control circuit 10A. The
voltage detector of the pulse-power supercapacitor 7 is the
detecting point of the maximum power tracking of the solar energy
system. The first electric switch 12 is capable of switching the
connection of the photovoltaic panel input system/photovoltaic
panel 6 to the pulse-power supercapacitor 7, the pulse-power
supercapacitor 7 to the second electric switch 13, the pulse-power
supercapacitor 7 to the DC/DC step-up/step-down supercapacitor 8,
and the photovoltaic panel 6 to the DC/DC step-up/step-down
converter supercapacitor 8. In addition, the logic control circuit
10A of the present invention is the control center of the
pulse-power supercapacitor 7-solar power system, which receives the
voltage status of the voltage detector of the pulse-power
supercapacitor 7 and the accumulator 11, and the voltage/current
status of the load 10. When executing the maximum power tracking of
the system, the logic control circuit 10A controls the input of the
photovoltaic panel, the output of the supercapacitor, and the duty
ratio D of the DC/DC step-up/step-down converter 8 to adjust the
resistance of the load 10. The logic control circuit 10A also
controls the three-stage-charging during the charging process, and
controls the electric energy to drive the load 10 in an intelligent
adjustable way during the discharging process. The second electric
switch 13 of the present invention is located behind the circuit
relating to the photovoltaic panel maximum power tracking, and is
connected between the accumulator 11 and the load 10, so as to
switch the solar power system to the accumulator 11 for charging,
or to the load 10 for discharging.
[0068] The voltage/current guard circuit is used for preventing
damages caused by the over-charging or over-discharging of the
accumulator 11, so as to extend the life of the accumulator 11. The
load 10 of the system can be a LED array, a lamp, a mechanical
device, a monitoring equipment, a detecting apparatus, or a signal
communicator, etc . . . . Some of these devices, such as LED
arrays, need to be operated in a constant current to control the
luminance. Some other devices, such as mechanical devices,
monitoring equipments, detecting apparatuses, etc . . . , need to
be operated in a constant for stable operations. The system can
drive the load 10 for various desired conditions in an intelligent
adjustable and most efficient way.
[0069] Furthermore, the present invention further includes a
current detector 14 for detecting a current of the load 10 and
generating a detecting signal. The detecting signal is transmitted
to the logic control circuit 10A through the voltage/current guard
circuit 15 for controlling a current outputted from the accumulator
to the load 10.
[0070] While the invention has been described in terms of what is
presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention needs not be
limited to the disclosed embodiment. On the contrary, it is
intended to cover various modifications and similar arrangements
included within the spirit and scope of the appended claims which
are to be accorded with the broadest interpretation so as to
encompass all such modifications and similar structures.
* * * * *