CN113193245A - SOH (State of health) balancing method for distributed battery energy storage system of micro-grid - Google Patents

SOH (State of health) balancing method for distributed battery energy storage system of micro-grid Download PDF

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CN113193245A
CN113193245A CN202110470080.7A CN202110470080A CN113193245A CN 113193245 A CN113193245 A CN 113193245A CN 202110470080 A CN202110470080 A CN 202110470080A CN 113193245 A CN113193245 A CN 113193245A
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battery energy
soh
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distributed battery
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CN113193245B (en
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吴青峰
褚晓林
刘立群
于少娟
李岩
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Taiyuan University of Science and Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
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    • H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J15/00—Systems for storing electric energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
    • H02J7/005—Detection of state of health [SOH]
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract

The invention discloses a method for balancing SOH of a distributed battery energy storage system of a micro-grid, belongs to the technical field of inverter control of the distributed battery energy storage system of the micro-grid, and solves the problems that the SOH balance among groups of the distributed battery energy storage system cannot be realized by a SOH balancing scheme of the battery energy storage system and a central controller and global communication are needed. In addition, the invention also has the advantages of adjustable SOH balance speed and good control effect under the communication delay working condition and when the output power of the renewable energy source fluctuates.

Description

SOH (State of health) balancing method for distributed battery energy storage system of micro-grid
Technical Field
The invention belongs to the technical field of inverter control of a micro-grid distributed energy storage system, and particularly relates to a SOH (state of health) balancing method of a micro-grid distributed battery energy storage system.
Background
With the emphasis of governments on economic sustainability development, alternating current micro-grids composed of clean and renewable Distributed Generation (DG) devices such as photovoltaic devices and wind power devices have been rapidly developed and widely researched. Because the DG power generation such as photovoltaic power generation, wind power generation and the like has intermittency and volatility, a distributed energy storage system is generally installed in a microgrid to ensure the stability and reliability of load power supply.
The distributed battery energy storage system inverter in the island alternating current microgrid generally adopts droop control to realize power equalization and voltage frequency regulation. Due to the difference of the manufacturing process, the aging degree and the ambient temperature of the distributed battery energy storage system, the initial State of Health (SOH) values of the distributed battery energy storage system are inconsistent. When the distributed battery energy storage system inverter adopts the traditional droop control, the inconsistency of the initial SOH cannot be eliminated, so the SOH cannot be balanced. The uneven SOH can lead to inconsistent scrapping time of the distributed battery energy storage system, increase the maintenance cost of the microgrid and seriously shorten the service life of the distributed battery energy storage system. Therefore, research on the SOH equalization problem of the distributed battery energy storage system is necessary.
The existing SOH balancing scheme of the battery energy storage system only considers the SOH balancing among the battery systems in a single battery pack, and the SOH balancing among the distributed battery energy storage system groups cannot be realized. Meanwhile, the existing scheme needs a central controller and global communication, and has the disadvantages of large communication quantity, high cost and complex algorithm.
Disclosure of Invention
The purpose of the invention is: the method for balancing the SOH of the distributed battery energy storage system of the microgrid is provided for solving the problems that the existing SOH balancing scheme of the battery energy storage system cannot achieve the SOH balancing among the distributed battery energy storage system groups and needs a central controller and global communication, and the SOH balancing among the distributed battery energy storage system groups is achieved on the premise that the central controller is not needed, communication is reduced, and cost is reduced.
The design concept of the invention is as follows: each distributed battery energy storage system is regarded as an agent, active power output by an inverter of the distributed battery energy storage system is adjusted through DOD information interaction between the agents, SOH balance of the distributed battery energy storage system under different loads is achieved, the service life of the distributed battery energy storage system is prolonged, and maintenance cost and replacement cost of the distributed battery energy storage system in the microgrid are reduced. In addition, the invention also has the advantages of adjustable SOH balance speed and good control effect under the communication delay working condition and when the output power of the renewable energy source fluctuates.
The invention is realized by the following technical scheme.
A SOH (sequence of events) balancing method for a micro-grid distributed battery energy storage system comprises the following steps:
s1: estimating the SOH of the battery energy storage system, and analyzing factors influencing the SOH balance: SOH is an indicator of the degree of aging and degradation of a distributed battery energy storage system and is therefore typically expressed in terms of a percentage. Since the distributed battery energy storage system is a nonlinear system and the SOH is difficult to directly measure due to the influence of multiple parameters of the SOH receiver, the SOH needs to be estimated;
estimating the SOH of the distributed battery energy storage system by using a SOH estimation method based on a life cycle, wherein the expression is as follows:
Figure RE-RE-GDA0003088264900000021
in formula (1): cleftRepresenting the remaining life cycle, C, of the distributed battery energy storage systemtotalRepresents the total life cycle, C, of the distributed battery energy storage systemalcIndicating cumulative lifecycle, SOH0Represents the initial value of SOH;
c in formula (1)totalThe relationship to DOD is:
Ctotal＝a·DOD-b (2)
in formula (2): DOD represents the depth of discharge of the distributed battery energy storage system, and a and b are constants;
the SOH expression obtained by substituting formula (2) into formula (1) is:
Figure RE-RE-GDA0003088264900000022
DOD in the formula (3) can be represented by relative SOH of SOHRTo indicate that:
DOD＝(SOHR)z·DODmax (4)
in formula (4): DODmaxRepresents the maximum of all DODs, z being the scaling factor;
relative value SOH of SOH in formula (4)RThe expression of (a) is as follows:
Figure RE-RE-GDA0003088264900000023
in the formula Qi,maxRepresents the maximum capacity, Q, of the ith distributed battery energy storage systemn,maxRepresents the maximum capacity, Δ SOC, of all distributed battery energy storage systemsi,minRepresenting the minimum value of the change in SOC, Δ SOC, over a certain timeaveRepresenting the average value of the SOC variation of all the distributed battery energy storage systems;
s2: improved P-f droop control:
in order to overcome the defect that the SOH balance of a battery energy storage system cannot be realized by the traditional P-f droop control, an improved P-f droop control scheme is provided, and the SOH balance of a distributed battery energy storage system is realized by the following formula:
Figure RE-RE-GDA0003088264900000024
in the formula (6), frefIs a reference value of voltage, m is a droop coefficient, P is an active power output by the inverter, DODiIs the ith distributed typeDepth of discharge, DOD, of battery energy storage systemaveThe average value of DODs of all the distributed battery energy storage systems is shown, and n is the number of the distributed battery energy storage systems;
to calculate DOD in equation (6)aveRegarding each distributed battery energy storage system as an agent, communicating between the agents of the adjacent distributed battery energy storage systems, and determining DOD by using an average consistency algorithmaveThe expression is as follows:
Figure RE-RE-GDA0003088264900000031
in formula (7): DODave_iRepresenting DODiAverage value of (D), DODiRepresenting a distributed battery energy storage systemiIs a scaling factor, and is DOD in an iterative processi[k]And DODj[k]Is obtained according to the formula (4) and thetaij[k]Is 0; the distributed battery energy storage system agent utilizes the communication line to communicate with the nearest adjacent distributed battery energy storage system agent, and DOD of the distributed battery energy storage system can be obtained through a plurality of iterations according to the formula (7)ave。
The scheme has the advantages that a central controller is omitted, communication is only needed between adjacent agents, and communication quantity and construction cost are reduced.
Further, before the step S2, the SOH balance influence of the conventional P-f droop control is analyzed to determine the SOH balance mechanism influenced by the conventional P-f droop control and the relationship between the droop control and the SOH balance. In a medium-high voltage micro-grid, the main component of the line impedance is the inductance. Therefore, the inverter of the distributed battery energy storage system adopts a P-f droop control algorithm, and the expression of the P-f droop control algorithm is as follows:
f＝fref-m(P-Pref) (8)
E＝Eref-n(Q-Qref) (9)
in the equations (8) and (9), E and f are the output voltage and frequency of the inverter, respectively, and frefAnd ErefReference values for voltage and frequency, respectively, P and Q for inversion, respectivelyActive power and reactive power output by the device, m and n are droop coefficients respectively, PrefAnd QrefThe reference values of active power and reactive power are respectively.
When the traditional P-f droop control is adopted, the active power output by the inverters among the multiple battery packs is equally divided in a steady state, and the equal division of the active power means that the distributed battery energy storage system discharges with the same DOD. According to the formula (3), if the initial SOH among the distributed battery energy storage system groups is inconsistent, but the DOD is consistent, the SOH among the distributed battery energy storage system groups is unbalanced.
Furthermore, the microgrid distributed battery energy storage system is an island alternating current microgrid system consisting of a photovoltaic, a fan, a battery energy storage system, a power electronic converter and a load, the photovoltaic is connected to the grid through a DC/DC converter and an inverter in the island alternating current microgrid system, the fan is connected to the grid through the inverter, the distributed battery energy storage system supplies power to the load through the inverter in parallel, the photovoltaic and fan inverters adopt an MPPT control scheme, and the distributed battery energy storage system inverter adopts an S2 improved P-f droop control scheme.
Compared with the prior art, the invention has the beneficial effects that:
1. the SOH balance of the battery energy storage system in the island alternating-current microgrid is realized, the frequency of the system is kept not to deviate in the SOH balance process, the service life of the distributed battery energy storage system is prolonged, and the maintenance cost of the microgrid is reduced.
2. Only communication between adjacent distributed battery energy storage system agents is needed, a central controller is not needed, the communication quantity is small, and the cost is low;
3. the scheme can still obtain good control effect under the condition that the photovoltaic output power fluctuates and the communication is delayed. Adjusting the droop coefficient can achieve adjustment of the SOH equalization speed.
Drawings
FIG. 1 is a diagram of a distributed battery energy storage system structure of an island microgrid;
FIG. 2 is a SOH simulation waveform diagram of a distributed battery energy storage system inverter employing conventional P-f droop control;
FIG. 3 is a waveform diagram of an active power simulation of a distributed battery energy storage system inverter using conventional P-f droop control;
FIG. 4 is a waveform diagram of frequency simulation of a distributed battery energy storage system inverter using conventional P-f droop control;
FIG. 5 is a communication diagram of various distributed battery energy storage system agents;
FIG. 6 is a SOH simulation waveform diagram of a distributed battery energy storage system inverter employing improved P-f droop control;
FIG. 7 is a waveform diagram of an active power simulation of a distributed battery energy storage system inverter using improved P-f droop control;
FIG. 8 is a waveform diagram of frequency simulation of a distributed battery energy storage system inverter using modified P-f droop control;
fig. 9 is an overall control block diagram of a distributed battery energy storage system inverter;
FIG. 10 is a waveform of SOH simulation under different loads;
FIG. 11 is a waveform diagram of active power simulation under different loads;
FIG. 12 is a waveform of frequency simulation under different loads;
FIG. 13 is a waveform of SOH simulation under photovoltaic output power fluctuation;
FIG. 14 is a graph of active power simulation waveforms under photovoltaic output power fluctuation;
FIG. 15 is a waveform diagram of frequency simulation under photovoltaic output power fluctuation;
FIG. 16 is a waveform of SOH simulation with communication delay;
FIG. 17 is a waveform diagram of active power simulation with communication delay;
FIG. 18 is a waveform of frequency simulation with communication delay;
FIG. 19 is a graph of a simulation waveform of SOH equalization speed adjustment (droop coefficient of 0.62);
fig. 20 is a waveform diagram of simulation of SOH equalization speed adjustment (droop coefficient of 0.72).
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. Unless otherwise specified, the examples follow conventional experimental conditions.
In this embodiment, a structure diagram of the distributed battery energy storage system is shown in fig. 1, the distributed battery energy storage system supplies power to a common load or a local load through respective inverters in parallel, and the switch CB can control the connection and disconnection of the load.
ZnRepresenting the line impedance of the microgrid, due to the non-uniformity of the line length and the degree of ageing, ZnValues generally not equal, pnActive power, i, output for inverters of distributed battery energy storage systemsnAnd charging and discharging current for the distributed battery energy storage system.
A SOH (sequence of events) balancing method for a micro-grid distributed battery energy storage system comprises the following steps:
s1: estimating the SOH of the battery energy storage system, and analyzing factors influencing the SOH balance: and estimating the SOH of the distributed battery energy storage system by adopting a SOH estimation method based on the life cycle.
The current expression for SOH includes two major categories: capacity-based and internal resistance-based, wherein capacity-based SOH is expressed as follows:
Figure RE-RE-GDA0003088264900000051
in the formula: qmaxRepresents the maximum available capacity, Q, available to the distributed battery energy storage systemratedRated capacity for a distributed battery energy storage system;
another SOH expression based on internal resistance is:
Figure RE-RE-GDA0003088264900000052
in the formula: rEIs the internal resistance, R, at the end of the life of the distributed battery energy storage systemCFor internal resistance of current, RNThe rated internal resistance of the new battery.
Although the SOH value can be estimated based on the capacity and internal resistance methods, the capacity-based method requires a long-time offline charge and discharge test on the distributed battery energy storage system, and the estimation result based on the internal resistance method is affected by the ambient temperature, so that the capacity-based method and the internal resistance-based method are not suitable for online estimation of the SOH.
Based on the method, the SOH of the distributed battery energy storage system is estimated by adopting a SOH estimation method based on the life cycle, and the expression of the SOH estimation method is as follows:
Figure RE-RE-GDA0003088264900000053
in formula (1): cleftRepresenting the remaining life cycle, C, of the distributed battery energy storage systemtotalRepresents the total life cycle, C, of the distributed battery energy storage systemalcIndicating cumulative lifecycle, SOH0Represents the initial value of SOH;
c in formula (1)totalThe relationship to DOD is:
Ctotal＝a·DOD-b (2)
in formula (2): DOD represents the depth of discharge of the distributed battery energy storage system, and a and b are constants;
the SOH expression obtained by substituting formula (2) into formula (1) is:
Figure RE-RE-GDA0003088264900000054
DOD in the formula (3) can be represented by relative SOH of SOHRTo indicate that:
DOD＝(SOHR)z·DODmax (4)
in formula (4): DODmaxRepresents the maximum of all DODs, z being the scaling factor;
relative value SOH of SOH in formula (4)RThe expression of (a) is as follows:
Figure RE-RE-GDA0003088264900000061
in the formula Qi,maxRepresents the maximum capacity, Q, of the ith distributed battery energy storage systemn,maxRepresenting all distributed battery energy storage systemsSystem maximum capacity, Δ SOCi,minRepresenting the minimum value of the change in SOC, Δ SOC, over a certain timeaveRepresenting the average value of the SOC variation of all the distributed battery energy storage systems;
the currently common method for estimating the SOC of the distributed battery energy storage system is an ampere integral method, and the expression of the method is as follows:
Figure RE-RE-GDA0003088264900000062
in the formula: SOC0For an initial SOC value, Q, of a distributed battery energy storage systemratedRated capacity of the distributed battery energy storage system, P is active power output by an inverter of the distributed battery energy storage system, VdcIs the output voltage of the distributed battery energy storage system.
The expression for Δ SOC in the above equation is:
Figure RE-RE-GDA0003088264900000063
the expression of z in the above formula is as follows:
Figure RE-RE-GDA0003088264900000064
according to the formula, the SOH of the distributed battery energy storage system is closely related to the active power output by the inverter.
S2, analyzing the influence of the traditional P-f droop control on the SOH balance, and determining the influence of the traditional P-f droop control on the SOH balance mechanism and the relation between the droop control and the SOH balance; the distributed battery energy storage system inverter adopts a P-f droop control algorithm, and the expression is as follows:
f＝fref-m(P-Pref) (6)
E＝Eref-n(Q-Qref) (7)
in equations (6) and (7), E and f are the output voltage and frequency of the inverter, respectively, and frefAnd ErefParameters of voltage and frequency, respectivelyConsidering value, P and Q are respectively active power and reactive power output by the inverter, m and n are respectively droop coefficients, PrefAnd QrefThe reference values of active power and reactive power are respectively.
Fig. 2 to 4 show SOH, active power and frequency waveforms of the distributed battery energy storage system inverter when the conventional droop control is adopted, and the load is increased when t is 0.8s in fig. 4.
As can be seen from the analysis of fig. 3, the active power output by the inverter is equally divided in the steady state, and the equally divided active power means that the distributed battery energy storage system discharges with the same DOD. According to the SOH estimation formula, if the initial SOH among the distributed battery energy storage system groups is inconsistent, but the DOD is consistent, the imbalance of the SOH among the distributed battery energy storage system groups is caused (as shown in fig. 2).
Fig. 4 illustrates that the frequency of the system may shift on the basis of the reference value since the droop control is a poor control. In addition, the load is increased to cause frequency shift.
S3: improved P-f droop control:
Figure RE-RE-GDA0003088264900000071
in the formula (6), frefIs a reference value of voltage, m is a droop coefficient, P is an active power output by the inverter, DODiFor depth of discharge, DOD, of the ith distributed battery energy storage systemaveThe average value of DODs of all the distributed battery energy storage systems is shown, and n is the number of the distributed battery energy storage systems;
to calculate DOD in equation (6)aveRegarding each distributed battery energy storage system as an agent, communicating between the agents of the adjacent distributed battery energy storage systems, and determining DOD by using an average consistency algorithmaveThe expression is as follows:
Figure RE-RE-GDA0003088264900000072
in formula (7): DODave_iRepresenting DODiAverage value of (2)，DODiRepresenting a distributed battery energy storage systemiIs a scaling factor, and is DOD in an iterative processi[k]And DODj[k]Is obtained according to the formula (4) and thetaij[k]Is 0; the distributed battery energy storage system agent utilizes the communication line to communicate with the nearest adjacent distributed battery energy storage system agent, and DOD of the distributed battery energy storage system can be obtained through a plurality of iterations according to the formula (7)ave。
Solving DOD using the above consistency algorithmaveHas the advantages that: a central controller is omitted, communication is only needed between adjacent agents, and the communication quantity and the construction cost of the microgrid are reduced.
Fig. 5 is a process of equalizing SOH, and as can be analyzed from fig. 7, different from fig. 3, after the inverter of the distributed battery energy storage system adopts the proposed scheme, the active power of the inverter is not equally divided, but the active power output by the distributed battery energy storage system with a high SOH is large (i.e., in a deep discharge state), and the SOH is decreased at a high speed; the distributed battery energy storage system with low SOH outputs less active power (namely in a shallow discharge state), and the SOH is slowly reduced, so that the SOH can be balanced after being regulated for a period of time.
In addition, the active power regulating factor ranges
Figure RE-RE-GDA0003088264900000073
And is combined with the traditional droop control through a multiplication relation, therefore, the frequency does not shift in the SOH equalization process.
The overall control block diagram of the distributed battery energy storage system inverter is shown in fig. 9. Firstly, instantaneous values P and Q of active power and reactive power are firstly subjected to Low Pass Filter (LPF) to obtain average values P and Q, and then the reference voltage V of the inverter voltage ring can be obtained through the improved P-f droop controlref。
In the specific implementation mode, the scheme provided under different working conditions is adopted for simulation verification. And (3) establishing a simulation model of the 3 distributed battery energy storage systems by using PSCAD/EMTDC simulation software according to the graph 5, and verifying the effectiveness of the proposed scheme under different working conditions.
The simulation parameters are as follows:
TABLE 1 simulation parameters
Item (symbol) Simulation parameters
Line impedance R1+jX1 0.2+j1.0/Ω
Line impedance R2+jX2 0.4+j2.0/Ω
Line impedance R3+jX3 0.6+j3.0/Ω
Rated frequency f ref 50/Hz
Voltage on the direct current side VDC 800/V
Rated capacity of distributed battery energy storage system Qrated 1000/Ah
Coefficient of sag m 0.032e-3rad/W
DOD coefficient a 694
DOD coefficient b 0.795
Distributed battery energy storage system accumulation period Calc 400
Working condition 1: and (4) carrying out simulation verification on the proposed scheme under different loads. Simulation waveforms of the proposed scheme under different loads are shown in fig. 10-12. According to the scheme, the active power output by the inverter of the distributed battery energy storage system can be adjusted according to the state of SOH, so that SOH balance among groups of the distributed battery energy storage system is realized, and the frequency does not deviate in the SOH balance process. When the load is increased when t is 0.9s, the active power output by the inverter is increased, the SOH is reduced at a higher speed, the frequency is shifted to a certain extent, and the SOH balance can still be ensured.
Working condition 2: the photovoltaic output power fluctuates. The power of the photovoltaic output changes with the change of the illumination intensity, the simulation waveforms under the working condition are shown in fig. 13-15, and the load is increased when t is 1 s. P in FIG. 14pvPower output for photovoltaic, P, as the intensity of illumination decreasespvAnd is continuously decreased. Fig. 13 to fig. 15 illustrate that, when the photovoltaic output power fluctuates, the power output by the inverter of the distributed battery energy storage system also fluctuates, but the proposed scheme can still achieve SOH equalization among groups of the distributed battery energy storage system and ensure that no frequency shift occurs during the SOH equalization.
Working condition 3: communication is delayed. Communication delays are inevitable in communication systems. Fig. 16-18 are simulation waveforms of the proposed scheme under the condition of communication delay. Distributed battery energy storage system when t is 0.4s1A communication delay of 0.2s occurs, and the load is increased when t is 0.8 s. Fig. 16-18 demonstrate that the communication delay may cause waveform fluctuation, but the proposed scheme can still achieve SOH equalization and maintain frequency quality after a period of time adjustment, thereby verifying the validity of the proposed scheme under the condition of communication delay.
Working condition 4: adjustment of the SOH equalization speed. Fig. 19 and 20 are SOH equalization speed simulation waveforms for different droop coefficients. It can be analyzed from fig. 19 and 20 that the droop coefficient can affect the equalizing speed of SOH, and the larger the droop coefficient is, the faster the equalizing speed of SOH is
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (3)

1. A SOH (state of health) balancing method for a micro-grid distributed battery energy storage system is characterized by comprising the following steps of:
s1: estimating the SOH of the battery energy storage system, and analyzing factors influencing the SOH balance: estimating the SOH of the distributed battery energy storage system by using a SOH estimation method based on a life cycle, wherein the expression is as follows:
Figure FDA0003045030290000011
in formula (1): cleftRepresenting the remaining life cycle, C, of the distributed battery energy storage systemtotalRepresents the total life cycle, C, of the distributed battery energy storage systemalcIndicating cumulative lifecycle, SOH0Represents the initial value of SOH;
c in formula (1)totalThe relationship to DOD is:
Ctotal＝a·DOD-b (2)
in formula (2): DOD represents the depth of discharge of the distributed battery energy storage system, and a and b are constants;
the SOH expression obtained by substituting formula (2) into formula (1) is:
Figure FDA0003045030290000012
DOD in the formula (3) can be represented by relative SOH of SOHRTo indicate that:
DOD＝(SOHR)z·DODmax (4)
in formula (4): DODmaxRepresents the maximum of all DODs, z being the scaling factor;
relative value SOH of SOH in formula (4)RThe expression of (a) is as follows:
Figure FDA0003045030290000013
in the formula Qi,maxRepresents the maximum capacity, Q, of the ith distributed battery energy storage systemn,maxRepresents the maximum capacity, Δ SOC, of all distributed battery energy storage systemsi,minRepresenting the minimum value of the change in SOC, Δ SOC, over a certain timeaveRepresenting the average value of the SOC variation of all the distributed battery energy storage systems;
s2: improved P-f droop control:
Figure FDA0003045030290000014
in the formula (6), frefIs a reference value of voltage, m is a droop coefficient, P is an active power output by the inverter, DODiFor depth of discharge, DOD, of the ith distributed battery energy storage systemaveThe average value of DODs of all the distributed battery energy storage systems is shown, and n is the number of the distributed battery energy storage systems;
to calculate DOD in equation (6)aveRegarding each distributed battery energy storage system as an agent, communicating between the agents of the adjacent distributed battery energy storage systems, and determining DOD by using an average consistency algorithmaveThe expression is as follows:
Figure FDA0003045030290000015
in formula (7): DODave_iRepresenting DODiAverage value of (D), DODiRepresenting a distributed battery energy storage systemiIs a scaling factor, and is DOD in an iterative processi[k]And DODj[k]Is obtained according to the formula (4) and thetaij[k]Is 0; the distributed battery energy storage system agent communicates with its nearest neighbor distributed battery energy storage system agent using a communication line according to equation (7)DOD of distributed battery energy storage system can be obtained through a plurality of iterationsave。
2. The SOH equalization method of the microgrid distributed battery energy storage system of claim 1, characterized in that: before the step S2, analyzing the influence of the traditional P-f droop control on the SOH balance to determine the influence of the traditional P-f droop control on the SOH balance mechanism and the relation between the droop control and the SOH balance; the distributed battery energy storage system inverter adopts a P-f droop control algorithm, and the expression is as follows:
f＝fref-m(P-Pref) (8)
E＝Eref-n(Q-Qref) (9)
in the equations (8) and (9), E and f are the output voltage and frequency of the inverter, respectively, and frefAnd ErefReference values for voltage and frequency, P and Q are active power and reactive power output by the inverter, m and n are droop coefficients, PrefAnd QrefThe reference values of active power and reactive power are respectively.
3. The SOH equalization method of the microgrid distributed battery energy storage system of claim 1, characterized in that: the microgrid distributed battery energy storage system is an island alternating current microgrid system consisting of a photovoltaic, a fan, a battery energy storage system, a power electronic converter and a load, the photovoltaic is connected with an inverter through a DC/DC converter in the island alternating current microgrid system, the fan is connected with the grid through the inverter, the distributed battery energy storage system supplies power to the load through the inverter in parallel, the photovoltaic and fan inverters adopt an MPPT control scheme, and the distributed battery energy storage system inverter adopts an S2 improved P-f droop control scheme.
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015070602A1 (en) * 2013-11-12 2015-05-21 国家电网公司 Microgrid inverter sagging automatic control method based on small-signal stability analysis
CN109390927A (en) * 2019-01-03 2019-02-26 燕山大学 It is a kind of based on SOC without interconnected communication distributed energy storage droop control method
US20190181648A1 (en) * 2017-12-11 2019-06-13 Ge Energy Power Conversion Technology Limited Method and system for droop control of power systems
CN110365052A (en) * 2019-08-08 2019-10-22 东北大学 Microgrid energy-storage system state consistency control method based on power optimization scheduling
CN111668865A (en) * 2020-07-21 2020-09-15 广东电网有限责任公司电力科学研究院 Hierarchical control method and related device for echelon utilization energy storage system
CN112600188A (en) * 2020-12-07 2021-04-02 内蒙古工业大学 Multi-energy-storage SOC (system on chip) balanced segmentation self-adaptive droop control method for direct-current micro-grid
CN112713605A (en) * 2020-12-24 2021-04-27 太原科技大学 SOC (State of Charge) balancing method for non-equal-capacity battery energy storage unit of alternating-current micro-grid

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015070602A1 (en) * 2013-11-12 2015-05-21 国家电网公司 Microgrid inverter sagging automatic control method based on small-signal stability analysis
US20190181648A1 (en) * 2017-12-11 2019-06-13 Ge Energy Power Conversion Technology Limited Method and system for droop control of power systems
CN109390927A (en) * 2019-01-03 2019-02-26 燕山大学 It is a kind of based on SOC without interconnected communication distributed energy storage droop control method
CN110365052A (en) * 2019-08-08 2019-10-22 东北大学 Microgrid energy-storage system state consistency control method based on power optimization scheduling
CN111668865A (en) * 2020-07-21 2020-09-15 广东电网有限责任公司电力科学研究院 Hierarchical control method and related device for echelon utilization energy storage system
CN112600188A (en) * 2020-12-07 2021-04-02 内蒙古工业大学 Multi-energy-storage SOC (system on chip) balanced segmentation self-adaptive droop control method for direct-current micro-grid
CN112713605A (en) * 2020-12-24 2021-04-27 太原科技大学 SOC (State of Charge) balancing method for non-equal-capacity battery energy storage unit of alternating-current micro-grid

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
NAN LI等: "SOH balancing control method for MMC battery Energy Stoage System", 《IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS》 *
ZHAN MA等: "Multilayer SOH equalization scheme for MMC battery energy storage system", 《IEEE POWER ELECTRONICS REGULAR PAPER》 *
吴青峰等: "微电网储能系统过充和过放保护方案", 《电源技术》 *

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