Suppress the control method of the battery energy storage system of regenerative resource output-power fluctuation
Technical field
The present invention is a kind of control method of the battery energy storage system that suppresses regenerative resource output-power fluctuation, a particularly energy storage control method for the state-of-charge based on battery energy storage system (SOC) and variable time constant filter, belongs to distributed power generation energy supply technical field.
Background technology
Renewable energy power generation technology, as photovoltaic generation with wind power generation is pollution-free, renewable with it, the advantage such as wide that distributes, has received increasing concern.But renewable energy power generation has the advantages that fluctuation is large, randomness is strong.Therefore, configure on the spot the energy-storage system of certain capacity, can effectively suppress the fluctuation of renewable energy power generation power output, improve the ability of electrical network receiving renewable energy power generation.
The control strategy of the energy-storage system that Chinese scholars proposes at present mainly contains two kinds:
1) one is basic filtering control method.The method is taking basic filtering principle as basis, adopt the low pass filter of determining time constant filter to process the power signal of regenerative resource, to obtain its desired value, recycle the difference between control and compensation regenerative resource power output desired value and measured value that discharges and recharges of energy-storage system.
2) its two state-of-charge (SOC) feedback that is battery energy storage system.The state-of-charge (SOC) of battery energy storage system refers to the real-time dump energy of battery.The method, on the basis of basic filtering control method, has been introduced SOC feedback element, directly the output power value of energy-storage system is modified, so that the SOC value stabilization of battery is in certain scope.
In the first control strategy, energy-storage system can well suppress the fluctuation of regenerative resource, but filter time constant is single definite value, easily cause the super-charge super-discharge of battery energy storage system in capacity one timing of energy-storage system, thereby make battery out of service, cause regenerative resource power output to occur larger fluctuation; In the second control strategy, introduce SOC feedback element, in suppressing regenerative resource output-power fluctuation, effectively avoid the super-charge super-discharge of battery, extend the useful life of battery, but the correction being obtained by SOC feedback element is directly revised the output power value of energy-storage system, affect the smooth effect of regenerative resource power output.
Summary of the invention
The object of the invention is to consider the problems referred to above and provide a kind of in suppressing regenerative resource output-power fluctuation, effectively avoid the super-charge super-discharge of battery, maintain the stable operation of battery energy storage system, extended the control method of the battery energy storage system of the inhibition regenerative resource output-power fluctuation in the useful life of battery.
Technical scheme of the present invention is: the control method that suppresses the battery energy storage system of regenerative resource output-power fluctuation, it is characterized in that this control method is based on lowpass filtering theory, by the fertile hereby low pass filter of single order Bart, regenerative resource output power value is carried out to filtering, obtain regenerative resource power output desired value, utilize the difference between control and compensation regenerative resource power output desired value and measured value that discharges and recharges of battery energy storage system, thereby reach the object that suppresses regenerative resource output-power fluctuation.
The fertile hereby time constant filter of low pass filter of single order Bart of above-mentioned employing, to select according to the capacity of the result of spectrum analysis of regenerative resource power output and energy-storage system, first regenerative resource typical case output power curve is carried out to fast Fourier transform and obtain its frequency spectrum, the frequency of the power fluctuation composition that will compensate according to battery energy storage system, design time constant filter, also will consider the capacity of battery energy storage system simultaneously.
Above-mentioned control method need to be carried out stepping to the state-of-charge of battery energy storage system (SOC) value, and in the time that state-of-charge (SOC) value of battery energy storage system is being moved in limits, energy-storage system adopts determines time constant filter control; In the time that state-of-charge (SOC) value of battery energy storage system exceedes operation limit value, energy-storage system adopts variable time constant filter control, the state-of-charge (SOC) of battery energy storage system refers to the real-time dump energy of battery, battery management system (BMS) is responsible for information and processing to battery, and charging and discharging currents by battery and Time Calculation go out the real-time state-of-charge of battery.
Above-mentioned control method is adjusted time constant filter according to the state-of-charge of battery energy storage system (SOC), in suppressing regenerative resource output-power fluctuation, avoid the super-charge super-discharge of battery, extend the life-span of battery, transfer function by the energy-storage system power output to based on filtering principle is analyzed, and obtains the relation of energy-storage system output power value and time constant filter; According to the value of feedback of the state-of-charge of battery energy storage system (SOC), by adjusting time constant filter, indirectly change the output power value of energy-storage system, thereby make state-of-charge (SOC) value stabilization of battery energy storage system in certain scope.
Above-mentioned control method, taking filtering principle as basis, by the control that discharges and recharges of energy-storage system, compensates the fluctuation composition of a certain special frequency channel of regenerative resource power output.
The time constant filter of the filter that above-mentioned control method adopts, under the condition that allow at energy storage system capacity, selects by renewable energy resources power output is carried out to spectrum analysis.
Above-mentioned control method is by state-of-charge (SOC) value of battery management system (BMS) battery energy storage system that provides, according to the relation between the size of energy-storage system output power value and time constant filter, adjust in real time the size of time constant filter, thereby make state-of-charge (SOC) value stabilization of battery energy storage system in certain scope.
Above-mentioned regenerative resource power output is P
t; The power output of battery energy storage system is
; The power that injects power distribution network is
; Battery energy storage system power output reference value is
Can obtain according to principle of energy balance,
Wherein,
for just, represent battery energy storage system electric discharge;
for negative, represent battery energy storage system charging;
Regenerative resource power output P
t, by the fertile hereby low pass filter of single order Bart, obtain regenerative resource power output reference value P
t_ref, itself and P
tsubtract each other the power output reference value that obtains energy-storage system
for just representing energy storage system discharges, it is the charging of negative indication energy-storage system.The SOC value of battery that energy storage controller is uploaded by BMS, changes the size of time constant filter, thereby makes the SOC value stabilization of battery in certain scope according to the method for adjustment of variable time constant filter;
Wherein, the fertile hereby low pass filter of single order Bart is shown below:
Wherein, s is differential operator; T is time constant filter;
The fertile hereby amplitude-frequency function of low pass filter of single order Bart is the function of a monotone decreasing, equals at 0 o'clock in frequency, gets maximum 1; Frequency equals cut-off frequency w
ctime, amplitude is 0.707;
In filtering control method, the relation of each variable is as follows:
S in (3) formula is used
represent, and can obtain after difference:
By (4) Shi Ke get,
Wherein, T
dfor computing cycle, P
t_ref(t-1) be renewable energy power generation power P
t_ref(t) reference value in a upper moment from formula (6), is calculated cycle T in real system
ddetermine, so the reference signal of next moment battery power output
only with the renewable energy power generation power P of current time
t(t), the reference value P of previous moment renewable energy power generation power
t_ref(t-1) relevant with time constant filter T;
The state-of-charge SOC of battery refers to the dump energy that battery is current, in Practical Project, due to cell memory capacity and operating voltage lower, therefore large capacity energy-storage system is all made up of multiple battery pack connection in series-parallel; Battery management system (BMS) estimates the SOC value of each battery pack, and then by relatively obtaining the SOC value of whole energy-storage system;
On the basis of basic filtering control method, add SOC FEEDBACK CONTROL, in the time that SOC value is within the scope of limit value, energy-storage system adopts predefined time constant filter value to control; In the time that SOC value exceedes limit value, by changing the size of time constant filter, little by little change the power output of battery, thereby make the SOC value stabilization of battery in the scope limiting, effectively avoid deeply filling deeply and put of battery.
Battery SOC can carry out stepping according to its limit value, and SOC is divided into working range
, adjusting range
, normal range (NR)
and forbidden range and
.Wherein
, as shown in Figure 5.SOC
maxwith SOC
minbe respectively battery SOC bound, when battery operated, SOC scope mustn't exceed
, when SOC value of battery equals SOC
maxtime, energy storage inverter restriction charging, only allows electric discharge, when SOC value of battery is less than or equal to SOC
mintime, energy storage inverter restriction electric discharge, only allows charging.
with
the object arranging is for avoiding battery sharply to decline because super-charge super-discharge causes the life-span, general
get 1,
get 0.3;
with
be respectively the bound of battery SOC value while normally working, the object of its setting is to retain certain operation to regulate nargin, when SOC exists
while operation in scope, time constant filter is constant, and battery normally moves.When SOC exists
when operation, time constant filter starts to change in scope, so as to avoid or delay SOC to
or
approach.SOC bound nargin is desirable 10%,
The modification method of time constant filter is mainly SOC value and the regenerative resource fluctuation size current according to battery, based on the relation of time constant filter and energy storage power output, optimize and choose time constant filter rate of change, original time constant filter is revised, thus avoid or delay SOC to
or
approach, to can ensure the compensation effect that battery is lasting, and extend its life-span.Wherein, T
dfor control cycle; T
(t)for the time constant filter of current time; T
(t+1)for the time constant filter in next moment; T
min, T
maxfor the bound of time constant filter; C is the rate of change of time constant filter.C and T
dthe product correction that is time constant filter, be shown below:
ΔT=C·T
d (7)
Generally speaking, time constant filter is larger, and the required power of battery, capacity are more.Therefore when SOC operates in adjusting range
time, its time constant filter should reduce, and in the time that SOC more approaches its bound, its time constant filter also should more approach its lower limit T
minthereby, avoid or delay SOC to
or
approach, to can ensure the compensation effect that battery is lasting, and extend its life-span.
Variable time constant filter control method process is as follows:
The first step, gathers the SOC value that battery BMS system provides;
Second step, judges SOC value, if SOC is greater than SOC
max, energy storage inverter restriction charging, only allows electric discharge, and jumps to the 4th step; Otherwise, carry out next step;
The 3rd step, if SOC is less than SOC
min, energy storage inverter restriction electric discharge, only allows charging, carries out next step;
The 4th step, if SOC is less than
and be greater than
, battery, with the constant control of fixing time of initial time constant filter, forwards the 5th step to;
If SOC is greater than
judgement
whether be greater than 0, if
be greater than 0,, if
be less than 0,, forward the 5th step to;
If SOC is less than
judgement
whether be greater than 0, if
be greater than 0,, if
be less than 0,, forward the 5th step to;
The 5th step, calculates the value P of current time renewable energy power generation power after after filtering by formula (5)
t_ref(t), carry out next step;
The 6th step, is calculated the reference value of next moment electric power generation cell by formula (6)
, and control command is issued to energy storage inverter, return to the first step.
The present invention considers that regenerative resource power output is because being subject to the impact of natural cause, has fluctuation greatly and the strong feature of randomness, affects the stable operation of power distribution network.For suppressing the fluctuation of regenerative resource power output, the present invention is based on basic filtering principle, utilize regenerative resource power output inhibition good and add SOC feedback element, avoid the super-charge super-discharge of battery, and innovate, in the time adding SOC feedback element, by regulating the size of time constant filter, indirectly change the power output of energy-storage system, thereby in suppressing regenerative resource output-power fluctuation, effectively avoid the super-charge super-discharge of battery, maintained the stable operation of battery energy storage system, extended the useful life of battery.The present invention is a kind of energy storage control method based on the real-time state-of-charge of battery and variable time constant, is a kind of control method of battery energy storage system of convenient and practical inhibition regenerative resource output-power fluctuation.
Brief description of the drawings
Fig. 1 is the structure chart of regenerative resource of the present invention and energy-storage system;
Fig. 2 is the fertile hereby low pass filter Bode diagram of Bart of the present invention;
Fig. 3 is energy-storage system power output transfer function Bode diagram schematic diagram of the present invention;
Fig. 4 is battery SOC limit value schematic diagram of the present invention;
Fig. 5 is the variable time constant filter control method of the present invention structure chart;
Fig. 6 time constant filter method of adjustment control block diagram;
Fig. 7 is the variable time constant filter control flow chart of the present invention.
Embodiment
Embodiment:
Below according to Figure of description, to further statement in detail of technical scheme of the present invention.
Battery energy storage system and renewable energy system grid connected structure figure are as shown in Figure 1.Regenerative resource is connected to power distribution network by its energy converter, and battery energy storage system is connected to the grid-connected ac bus place of regenerative resource by its two-way inverter.Energy storage controller, by gathering the power output signal of regenerative resource, according to the power output reference value that calculates energy-storage system based on the variable time constant filter control method of battery SOC, suppresses the fluctuation of regenerative resource power output.In figure, arrow represents energy flow direction, P
tfor regenerative resource power output;
for the power output of battery energy storage system;
for injecting the power of power distribution network;
for battery energy storage system power output reference value.
Can obtain according to principle of energy balance,
Wherein,
for just, represent battery energy storage system electric discharge;
for negative, represent battery energy storage system charging.
In variable time constant filter energy storage control method based on battery SOC refers to energy-storage system the fluctuation composition of a certain frequency range suppresses in to regenerative resource power output, according to the size of SOC value of battery, time constant filter is revised, so that the SOC value all-the-time stable of battery is in certain scope, avoid the super-charge super-discharge of battery., its structure chart as shown in Figure 2.Regenerative resource power output P
t, by the fertile hereby low pass filter of single order Bart, obtain regenerative resource power output reference value P
t_ref, itself and P
tsubtract each other the power output reference value that obtains energy-storage system
for just representing energy storage system discharges, it is the charging of negative indication energy-storage system.The SOC value of battery that energy storage controller is uploaded by BMS, changes the size of time constant filter, thereby makes the SOC value stabilization of battery in certain scope according to the method for adjustment of variable time constant filter.
Wherein, the fertile hereby low pass filter of single order Bart is shown below:
Wherein, s is differential operator; T is time constant filter.Its amplitude-versus-frequency curve as shown in Figure 3.
As shown in Figure 3, the fertile hereby amplitude-frequency function of low pass filter of single order Bart is the function of a monotone decreasing, equals at 0 o'clock in frequency, gets maximum 1; Frequency equals cut-off frequency w
ctime, amplitude is 0.707.
In filtering control method, the relation of each variable is as follows:
The baud schematic diagram of battery energy storage system power output transfer function as shown in Figure 4.
In Fig. 4, T is time constant filter, and w is the corresponding frequency of time constant filter.By
Fig. 4 can find out: be T for time constant filter
1curve, energy-storage system power output pass letter be greater than w for frequency
1its power output amplitude of wave component be 1, energy-storage system can be greater than w by compensating frequency in theory
1all wave components; T in figure
1>T
2>T
3, w
1<w
2<w
3, time constant is larger, and its corresponding frequency is just less, and the frequency range that energy-storage system can compensate is just larger, and the output power value of energy-storage system is also just larger.
S in (3) formula is used
represent, and can obtain after difference:
By (4) Shi Ke get,
Wherein, T
dfor computing cycle, P
t_ref(t-1) be renewable energy power generation power P
t_ref(t) reference value in a upper moment.From formula (6), in real system, calculate cycle T
ddetermine, so the reference signal of next moment battery power output
only with the renewable energy power generation power P of current time
t(t), the reference value P of previous moment renewable energy power generation power
t_ref(t-1) relevant with time constant filter T.
The state-of-charge SOC of battery refers to the dump energy that battery is current.In Practical Project, due to cell memory capacity and operating voltage lower, therefore large capacity energy-storage system is all made up of multiple battery pack connection in series-parallel.Battery management system (BMS) estimates the SOC value of each battery pack, and then by relatively obtaining the SOC value of whole energy-storage system.
The present invention, on the basis of basic filtering control method, has added SOC FEEDBACK CONTROL, and in the time that SOC value is within the scope of limit value, energy-storage system adopts predefined time constant filter value to control; In the time that SOC value exceedes limit value, by changing the size of time constant filter, little by little change the power output of battery, thereby make the SOC value stabilization of battery in the scope limiting, effectively avoid deeply filling deeply and put of battery.
The stepping of battery SOC limit value as shown in Figure 5.
with
the bound of SOC value while normally working for battery that namely time constant filter is constant, in the time that SOC exceedes this two limit values, time constant filter starts to change;
with
the maximin of SOC when battery operated, when SOC value of battery equals
time, energy storage inverter restriction charging, only allows electric discharge, when SOC value of battery is less than
time, energy storage inverter restriction electric discharge, only allows charging.
The modification method of time constant filter as shown in Figure 6.Wherein, T
dfor control cycle; T
(t)for the time constant filter of current time; T
(t+1)for the time constant filter in next moment; T
min, T
maxfor the bound of time constant filter; C is the rate of change of time constant filter.C and T
dthe product correction that is time constant filter, be shown below:
ΔT=C·T
d (7)
The flow chart of variable time constant filter control method as shown in Figure 7.
The first step, gathers the SOC value that battery BMS system provides;
Second step, judges SOC value, if SOC is greater than SOC
max, energy storage inverter restriction charging, only allows electric discharge, and jumps to the 4th step; Otherwise, carry out next step;
The 3rd step, if SOC is less than
, energy storage inverter restriction electric discharge, only allows charging, carries out next step;
The 4th step, if SOC is less than
and be greater than
, battery, with the constant control of fixing time of initial time constant filter, forwards the 5th step to;
If SOC is greater than
, judgement
whether be greater than 0, if
be greater than 0,, if
be less than 0,, forward the 5th step to;
If SOC is less than
, judgement
whether be greater than 0, if
be greater than 0,, if
be less than 0,, forward the 5th step to;
The 5th step, calculates the value P of current time renewable energy power generation power after after filtering by formula (5)
t_ref(t), carry out next step;
The 6th step, is calculated the reference value of next moment electric power generation cell by formula (6)
, and control command is issued to energy storage inverter, return to the first step.
The present invention is the control method that suppresses the battery energy storage system of regenerative resource output-power fluctuation, and this invention belongs to distributed power generation energy supply technical field.Energy-storage system adopts after control method proposed by the invention, can effectively suppress the fluctuation of regenerative resource power output, and the state-of-charge that keeps battery be SOC value stabilization in certain scope, avoided the super-charge super-discharge of battery, extended the useful life of battery