U.S. patent application number 14/035229 was filed with the patent office on 2015-03-26 for method for controlling pumping of pump units in a wet well.
This patent application is currently assigned to WATER RESOURCES AGENCY, MINISTRY OF ECONOMIC AFFAIRS. The applicant listed for this patent is WATER RESOURCES AGENCY, MINISTRY OF ECONOMIC AFFAIRS. Invention is credited to Ya-Ching CHANG, Hao-Ting CHAO, Hsin-Yi CHUNG, Chung-Hsien LU.
Application Number | 20150086385 14/035229 |
Document ID | / |
Family ID | 52691109 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150086385 |
Kind Code |
A1 |
LU; Chung-Hsien ; et
al. |
March 26, 2015 |
METHOD FOR CONTROLLING PUMPING OF PUMP UNITS IN A WET WELL
Abstract
A method for controlling pumping of a plurality of pump units in
a wet well is disclosed. The method uses a genetic algorithm to
determine which of the pump units is to be started and its initial
operating frequency when the liquid level in the wet well reaches a
first predetermined level for pumping. During the pumping process,
the pumping control method monitors the liquid level in the wet
well in real time to obtain real-time state information and
fine-adjusts the initial operating frequency of the pump unit to be
started according to the real-time state information. Therefore,
the present disclosure achieves optimum efficiency and energy
saving.
Inventors: |
LU; Chung-Hsien; (Taipei
City, TW) ; CHANG; Ya-Ching; (Taipei City, TW)
; CHAO; Hao-Ting; (Taipei City, TW) ; CHUNG;
Hsin-Yi; (Taipei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WATER RESOURCES AGENCY, MINISTRY OF ECONOMIC AFFAIRS |
Taipei City |
|
TW |
|
|
Assignee: |
WATER RESOURCES AGENCY, MINISTRY OF
ECONOMIC AFFAIRS
Taipei City
TW
|
Family ID: |
52691109 |
Appl. No.: |
14/035229 |
Filed: |
September 24, 2013 |
Current U.S.
Class: |
417/53 |
Current CPC
Class: |
F04D 15/0072
20130101 |
Class at
Publication: |
417/53 |
International
Class: |
F04B 49/04 20060101
F04B049/04 |
Claims
1. A method for controlling pumping of a plurality of pump units in
a wet well, comprising the steps of: (1) monitoring inflow of the
wet well; (2) when a liquid level in the wet well reaches a first
predetermined level for pumping, calculating an objective through
an algorithm according to pumping performances of the pump units
and the inflow so as to determine one of the pump units to be
started and an initial operating frequency thereof and to generate
an initial control signal; (3) sending the initial control signal
to the one of the pump units to be started, and setting the initial
operating frequency to the one of the pump units to be started for
pumping; (4) monitoring the liquid level in the wet well in real
time to obtain real-time state information; (5) determining whether
a fine adjustment condition is met according to the real-time state
information, wherein when the fine adjustment condition is met, the
initial operating frequency for the one of the pump units to be
started is fine-adjusted and the step (4) is performed, and when
the fine adjustment condition is not met, the step (6) is
performed; and (6) determining whether the liquid level in the wet
well reaches a second predefined level for stopping pumping,
wherein when the liquid level in the wet well reaches the second
predefined level, the pump units are stopped, and when the liquid
level in the wet well does not reach the second predefined level,
the step (4) is performed.
2. The method of claim 1, wherein the algorithm is a genetic
algorithm.
3. The method of claim 2, wherein the pumping performances of the
pump units comprise pumping capacities and energy consumptions
assessed through performance curves of the pump units and pipeline
system curves of a pumping station, and the objective is a minimum
total energy consumption of the pump units.
4. The method of claim 3, wherein the genetic algorithm comprises
an operation based on a condition that a total of the pumping
capacities of the pump units is equal to the inflow of the wet
well.
5. The method of claim 1, wherein the real-time state information
is a liquid level difference in a unit time.
6. The method of claim 5, wherein when the liquid level difference
in the unit time is less than a minimum allowable value, the fine
adjustment condition is not met.
7. The method of claim 5, wherein when the liquid level difference
in the unit time is less than zero, the fine adjustment condition
is met, and the initial operating frequency for the one of the pump
units to be started is fine-adjusted downward but greater than or
equal to a minimum safety frequency.
8. The method of claim 5, wherein when the liquid level difference
in the unit time is greater than a limit value, the fine adjustment
condition is met, and the initial operating frequency for the one
of the pump units to be started is fine-adjusted upward.
9. The method of claim 1., wherein the step (3) further comprises
determining whether the one of the pump units to be started is
already started, wherein when the one of the pump units to be
started is already started, the initial operating frequency for the
one of the pump units is set to the one of the pump units to be
started, and when the one of the pump units to be started is not
started, the one of the pump units to be started is started first
and then the operating frequency is set to the one of the pump
units to be started.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present disclosure relates to pumping control methods,
and more particularly, to an energy-saving pumping control method
applied in a wet well.
[0003] 2. Description of Related Art
[0004] Conventional wastewater pumping stations are divided into
wet well and dry well types according to the installation of pump
units. The pump units in a dry well typed pumping station are
installed in a pipe gallery to facilitate visits by staff for
maintenance and repairs, while the submersible pump units in a wet
well typed pumping station are installed in a sewer tank that is
used for temporarily storing wastewater. The wet well typed pumping
station can have a reduced volume and save cost for deep excavation
of the pumping station.
[0005] Since wastewater can be temporarily stored in the wet well,
the pump units are generally started to pump wastewater out of the
wet well when the wastewater level rises to a high level. During
the wastewater pumping process, the total pumping capacity of the
pump units is greater than the inflow of the wet well and therefore
the wastewater level in the wet well begins to drop. When the
wastewater level reaches a low level, the pump units are stopped.
Meanwhile, wastewater continuously flows into the wet well and the
wastewater level begins to rise again. When the wastewater level
reaches the high level, the pump units are started again for
another pumping cycle.
[0006] In such a pumping method, the pump units are started over
and over again. If the pump units are often started before heat
generated is completely dissipated out of the pump units, the pump
units are easily damaged. Further, multiple pump units that are
connected in parallel in the wet well may come from different
manufacturers and have different characteristic curves and
different horsepower. As such, even if the pump its are set at the
same rated flow, it is difficult to achieve optimum efficiency and
energy saving through manual operations. Furthermore, a high
operating safety factor is required in manual operations and it is
difficult to perform a customized adjustment of operating
frequencies of the pump units through manual operations. Therefore,
the above-described method easily causes energy waste and the
device lifetime is adversely affected by frequent switching of the
pump units.
[0007] Therefore, there is a need to provide a method of pumping
control in a wet well that is applicable to a plurality of pump
units so as to overcome the above-described drawbacks.
SUMMARY
[0008] In view of the above-described drawbacks, the present
disclosure provides a method of pumping control in a wet well. The
method includes calculating the number and operating frequencies of
pump units to be started according to inflow of the wet well so as
to cause the total pumping capacity of the pump units to be equal
to the inflow of the wet well, thereby reducing the incidence of a
low liquid level, reducing the switching frequency of the pump
units and achieving optimum efficiency and energy saving.
[0009] The present disclosure provides a pumping control method for
controlling pumping of a plurality of pump units in a wet well,
which comprises the steps of: (1) monitoring inflow of the wet
well; (2) when the liquid level in the wet well reaches a first
predetermined level for pumping, calculating an objective through
an algorithm according to pumping performances of the pump units
and the inflow so as to determine one of the pump units to be
started and its initial operating frequencies and to generate an
initial control signal; (3) sending the initial control signal to
the one of the pump units to be started to set its initial
operating frequencies for pumping; (4) monitoring the liquid level
in the wet well in real time to obtain real-time state information;
(5) determining whether a fine adjustment condition is met
according to the real-time state information, wherein if yes, the
initial operating frequency of the one of the pump units to be
started is fine-adjusted and the process goes back to the step (4),
and if not, the process goes to the step (6); and (6) determining
whether the liquid level in the wet well reaches a second
predetermined level for stopping pumping, wherein if yes, the pump
units are stopped, and if not, the process goes back to step
(4).
[0010] According to the present disclosure, the minimum total
energy consumption is calculated by using a genetic algorithm
according to the pumping performances of the pump units and the
inflow of the wet well so as to determine which of the pump units
are to be started and their initial operating frequencies for
pumping. During the pumping process, the liquid level of the wet
well is continuously monitored and it is determined whether a fine
adjustment condition is met such that the initial operating
frequencies of the pump units to be started are fine-adjusted so as
to cause the total pumping capacity to be equal to the inflow of
the wet well, thereby reducing the incidence of a low liquid level,
saving energy consumption, reducing the switching frequency of the
pump units and increasing the device lifetime.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a flow chart showing a method of pumping control
in a wet well according to the present disclosure.
DETAILED DESCRIPTION
[0012] The following illustrative embodiments are provided to
illustrate the disclosure, these and other advantages and effects
can be apparent to those in the art after reading this
specification.
[0013] It should be noted that all the drawings are not intended to
limit the present disclosure, Various modifications and variations
can be made without departing from the spirit of the present
disclosure. Further, terms such as "on", "a" etc. are merely for
illustrative purposes and should not be construed to limit the
scope of the present disclosure.
[0014] FIG. 1 is a flow diagram showing a method of pumping control
in a wet well according to the present disclosure. The method of
the present disclosure is applicable to a plurality of pump units
that are connected in parallel in the wet well or in other
combinations.
[0015] Referring to FIG. 1, at step S01, inflow of the wet well is
monitored. In particular, the liquid level in the wet well is
sensed through a plurality of liquid level sensors in the wet well
such that the inflow of the wet well is calculated according to the
change of the liquid level with time. At step S02, when the liquid
level in the wet well reaches a predetermined level for pumping, as
sensed by a high liquid level sensor, the process goes to step S03.
At step S03, an objective is calculated by a computer through an
algorithm according to pumping performances of the pump units and
the inflow of the wet Well so as to determine which of the pump
units are to be started and their initial operating frequencies and
generate an initial control signal. In particular, the objective is
a minimum total energy consumption of the pump units.
[0016] The pump units may be manufactured by different
manufacturers and therefore have different performances. Further,
the pump units may have different pumping capacities according to
their positions and connections to the pipeline of the pumping
station. Therefore, the pumping performances of the pump units
include pumping capacities and energy consumptions that are
assessed through performance curves of the pump units and pipeline
system curves of the pumping station. The pumping capacity can be a
maximum pumping capacity and a minimum pumping capacity, for
example. The energy consumption can be energy consumption at the
maximum pumping capacity, energy consumption at the minimum pumping
capacity, or energy consumption at a pumping capacity between the
maximum pumping capacity and the minimum pumping capacity.
[0017] The algorithm performed by the computer is a genetic
algorithm. The genetic algorithm determines which of the pump units
are to be started and their initial operating frequencies according
to the pumping performances of the pump units and the inflow of the
wet well so as to achieve an optimum total pumping capacity that is
equal to the inflow of the wet well and a minimum total energy
consumption. Further, the algorithm can be operated based on a
condition that the total pumping capacity is equal to the inflow of
the wet well.
[0018] The genetic algorithm is an optimum search algorithm, which
originates from Darwin's theory of natural selection and survival
of the fittest. The genetic algorithm generates chromosomes by
coding variables, calculates fitness values of the chromosomes and
then performs selection, crossover and mutation to generate
offspring chromosomes, thereby gradually approaching an optimum
solution. In particular, the genetic algorithm includes the steps
of: [0019] (1) setting chromosomes according to the pumping
capacities and energy consumptions of the pump units; [0020] (2)
setting a margin of error for the pumping capacities; [0021] (3)
setting an error weight Wq for the pumping capacities and an energy
consumption weight Wp, wherein Wq and Wp are values between 0 and
1, and the sum of Wq and Wp is 1; [0022] (4) inputting chromosomes,
wherein N randomly selected chromosomes are provided, N is a
constant and each of the chromosomes represents the pumping
capacity and energy consumption of one of the pump units; [0023]
(5) fitness sorting, wherein if the pumping capacities of the
chromosomes are within the margin of error, the chromosomes are
sorted in an ascending order of energy consumptions, otherwise, if
the pumping capacities of the chromosomes are out of the margin of
error, a fitness function based on Wq and Wp is calculated for the
chromosomes such that the chromosomes are sorted in an ascending
order of the fitness function values; [0024] (6) keeping a number
of excellent chromosomes in the order of the fitness function
values and replicating the chromosomes to cause the number of the
chromosomes to reach N; [0025] (7) keeping the first X % of the
chromosomes in the order of the fitness function values and
crossing the first X % of the chromosomes with the remaining (1-X
%) of the chromosomes, wherein X is a constant; [0026] (8) mutating
the crossed chromosomes to keep the diversity advantage of the
chromosomes, thereby preventing omission of important information
in the search process; [0027] (9) calculating the number of pump
units that have a minimum total energy consumption according to the
mutated chromosomes; [0028] (10) determining whether the desired
number of convergence times for calculating the minimum total
energy consumption is reached, if yes, the process goes to the next
step, otherwise, the process goes back to step (5) for fitness
sorting; and [0029] (11) outputting the pump units to be started
and their initial operating frequencies and generating an initial
control signal, wherein the pump units to be started have a minimum
total energy consumption.
[0030] Through the above-described genetic algorithm, which of the
pump units are to be started and their suitable pumping capacities
as well as their operating frequencies are determined based on a
condition that the total pumping capacity is equal to the inflow of
the wet well so as to achieve the objective of a minimum total
energy consumption. For example, five pump units 1, 2, 3, 4, 5 can
be provided. The pump units 2, 4, 5 are determined to be started.
The total pumping capacity is the sum of the pumping capacities of
the pump units 2, 4, 5, and the minimum total energy consumption is
the sum of the energy consumptions of the pump units 2, 4, 5. The
pump units 2, 4, 5 have their respective operating frequencies.
Therefore, an initial control signal is generated by the computer.
Then, at step S04, the initial control signal is sent to the pump
units to be started so as to set their initial operating
frequencies for pumping. Before setting the initial operating
frequencies of the pump units to be started, a step of determining
whether the pump units to be started are already started is
performed. If the pump units to be started are already started, the
initial operating frequencies of the pump units are set. If the
pump units to be started are not started, the pump units are
started first and then their initial operating frequencies are
set.
[0031] During the pumping process, at step S05, the liquid level in
the wet well is continuously monitored in real time by the computer
through the liquid level sensors so as to generate real-time state
information. The real-time state information is a liquid level
difference in a unit time. In an embodiment, the real-time state
information is a liquid level difference per second. In the present
disclosure, the liquid level difference in a unit time is the
change of the liquid level in each time interval. For example,
.DELTA.h(t)=h(t)-h(t-1). Therein, t represents time, h represents
the liquid level, and .DELTA.h(t) represents the liquid level
difference in a unit time. Since the inflow of the wet well is not
fixed, the change of the liquid level in the wet well needs to be
monitored in real time so as to generate real-time state
information of .DELTA.h(t), thereby determining whether the liquid
level is rising, dropping or steady. According to the real-time
state information, the operating frequencies of the started pump
units can be fine-adjusted through the computer so as to cause the
total pumping capacity to be equal to the inflow of the wet well,
thus reducing the incidence of a low liquid level. To perform the
fine adjustment process, the computer determines whether the
real-time state information meets a fine adjustment condition at
step S06.
1. The Fine Adjustment Condition Not Being Met:
[0032] If .DELTA.h(t) is less than a minimum allowable value but
greater than zero, the fine adjustment condition is not met. In
such a circumstance, the liquid level is substantially steady and
the inflow of the wet well is slightly greater than the total
pumping capacity. The minimum allowable value is the minimum margin
of error set by a user. Since the inflow of the wet well is not
fixed, the total pumping capacity may not be always equal to the
inflow of the wet well. Such a margin of error prevents an
adjustment of the operating frequencies of the pump units when a
slight change of the liquid level occurs so as to save energy
consumption. Therefore, if it is determined that the fine
adjustment condition is not met at step S06, the process goes to
step S08.
2. The Fine Adjustment Condition Being Met:
[0033] On the other hand, if it is determined that the fine
adjustment condition is met at step S06, the operating frequencies
of the started pump units are fine adjusted at step S07. The fine
adjustment condition is determined to be net when the liquid level
rises or drops significantly.
[0034] If the liquid level rises significantly, i.e., .DELTA.h(t)
is greater than a limit value set by a user, it means that the
inflow of the wet well increases and the total pumping capacity is
less than the inflow. As such, the operating frequencies of the
pump units need to be fine-adjusted so as to increase the total
pumping capacity. Otherwise, the liquid level may rise fast to a
warning liquid level and become dangerous. Therefore, when
.DELTA.h(t) is greater than the limit value, the initial operating
frequencies of the pump units to be started are fine-adjusted
upward so as to cause the total pumping capacity of the pump units
to be equal to or greater than the inflow of the wet well.
[0035] If the liquid level drops significantly, i.e., .DELTA.h(t)
is less than zero, it means that the total pumping capacity is
greater than the inflow of the wet well. As such, the operating
frequencies of the pump units need to be fine-adjusted so as to
reduce the total pumping capacity. Therefore, the initial operating
frequencies of the pump units to be started are fine-adjusted
downward. But the initial operating frequencies must be greater
than a minimum safety frequency so as to prevent the pump units
from coming into an unsafe area where an erosion of the pump units
may occur.
[0036] After the fine adjustment of the operating frequencies of
the pump units at step S07, the process goes back to step S05 to
continuously monitor the liquid level in the wet well so as to
determine whether there is a need to fine-adjust the operating
frequencies of the pump units. If it is determined that the liquid
level difference per second does not meet the fine adjustment
condition, the process goes to step S08. At step S08, it is
determined whether the liquid level in the wet well reaches a
predetermined level for stopping pumping, as sensed by a low liquid
level sensor. If it is determined that the liquid level in the wet
well reaches the predetermined level for stopping pumping, the
process goes to step S09 to stop the pump units. Otherwise, if it
is determined that the liquid level in the wet well does not reach
the predetermined level for stopping pumping, the process goes back
to step S05 to continuously monitor the liquid level in the wet
well so as to continuously determine whether there is a need to
fine-adjust the operating frequencies of the pump units until the
liquid level in the wet well reaches the predetermined level for
stopping pumping.
[0037] According to the present disclosure, a genetic algorithm is
used to determine which of the pump units are to be started and
their initial operating frequencies for pumping according to the
pumping performances of the pump units and the inflow of the wet
well, thereby achieving a minimum total energy consumption.
Further, during the pumping process, the operating frequencies of
the pump units can be fine-adjusted according to the real-time
change of the liquid level in the wet well so as to cause the total
pumping capacity to be equal to the inflow of the wet well, thereby
reducing the incidence of a low liquid level, saving energy
consumption, reducing the switching frequency of the pump units and
increasing the device lifetime. Therefore, the present disclosure
achieves optimum efficiency and energy saving.
[0038] The above-described descriptions of the detailed embodiments
are only to illustrate the preferred implementation according to
the present disclosure, and it is not to limit the scope of the
present disclosure. Accordingly, all modifications and variations
completed by those with ordinary skill in the art should fall
within the scope of present disclosure defined by the appended
claims.
* * * * *