CN115882490A - SOC-based storage battery improved droop control method and system - Google Patents

SOC-based storage battery improved droop control method and system Download PDF

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CN115882490A
CN115882490A CN202211727649.4A CN202211727649A CN115882490A CN 115882490 A CN115882490 A CN 115882490A CN 202211727649 A CN202211727649 A CN 202211727649A CN 115882490 A CN115882490 A CN 115882490A
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soc
battery
power
droop
coefficient
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于爽
潘欢
封啸
纳春宁
李峰
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Ningxia University
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a method and a system for improving droop control of a storage battery based on SOC (system on chip), which comprises the following steps: acquiring the SOC of each storage battery, and calculating the average SOC and the average depth of discharge of the storage batteries based on the SOC; improving the droop coefficient by using PI control with SOC balance between storage batteries as a target based on the average charge state and the average depth of discharge; aiming at realizing power equalization among the storage batteries, calculating a power equalization compensation item of each storage battery by using PI control; the method comprises the following steps of calculating a voltage deviation compensation item by utilizing PI control with the aim of realizing consistency of output voltages of storage battery interface converters; and adjusting the output reference voltage of each storage battery interface converter according to the improved droop coefficient, the power average compensation term and the voltage deviation compensation term. The invention can effectively improve the bus voltage regulation precision and reduce the deviation of the direct current bus voltage.

Description

SOC-based storage battery improved droop control method and system
Technical Field
The invention belongs to the technical field of micro-grids, and particularly relates to a method and a system for improving droop control of a storage battery based on SOC.
Background
Frequency and phase do not exist in the light storage charging direct current microgrid, and bus voltage is an important reference index for measuring stability of the microgrid. Droop control is the most common method for regulating the dc bus voltage, and as a typical peer-to-peer control, has a strong scalability compared to other control methods, and enables power distribution even without communication. However, droop control also has certain limitations: due to the line impedance, droop control faces a tradeoff between bus voltage regulation deviation and power distribution accuracy. To solve this problem, chen F, burgos D, boroyvich D (interrogation of nonlinear droop control in DC Power distribution systems: load sharing, voltage regulation, effectiveness, and stability, IEEE Transactions on Power Electronics,2019,34 (10): 9404-9421) proposed a nonlinear droop control method that better eases the above-mentioned contradiction in the case of constant Power Load, but does not perform well in the case of non-constant Power Load. In order to further improve the control effect of droop control and expand the applicable occasions of droop control, researchers have introduced distributed secondary control in droop control, each distributed Power supply or Energy storage unit has its own independent controller (Zhao X Y, yang L h.an improved droop control method to improved Power supply sharing in isolated DC microprocessors, 12th IEEE PES Asia-capacitive Power and Energy Engineering Conference, 2020. The control mode has small dependence on a communication network and is widely applied to secondary adjustment of the droop control. Augustine S, lakshminaramma N, mishra M K (Control of photovoltaic-based low-voltage dc micro-grid system for power sharing with modified droop algorithm, the organization of Engineering and Technology,2016,9 (6): 1132-1143) proposes an adaptive droop Control based on a proportional droop index algorithm for a photovoltaic low-voltage direct current micro-grid, the Control method better realizes system power distribution and bus voltage regulation, but The proportional droop index has high dependence on communication, and once communication is lost or fails, secondary regulation easily fails. In order to avoid the above situation, mohammad J, safe P, hossei M (Enhanced frequency drop method for decentralized Power sharing control in DC microprocessors, IEEE Journal of emitting and Selected topologies in Power Electronics,2021,9 (2): 1290-1301) proposes a frequency injection adaptive droop control, which adjusts a droop coefficient by a low amplitude ac signal injected into a DC bus, thereby fundamentally avoiding the dependence of secondary control on communication, achieving bus voltage regulation while ensuring Power distribution accuracy, but the injected low amplitude ac signal may increase the voltage and current ripple of the DC bus, and reducing the bus voltage quality. Zhang Qinjin, chen Long, liu Yancheng, etc. (direct current micro-grid power distribution strategy based on active frequency injection, power system and its automation report, 2021,33 (7): 11-19) improve frequency injection adaptive droop control, so that low-amplitude alternating current signals are not injected under the steady state condition of the system, and are injected only when the system power changes, namely, the traditional droop control is adopted in the steady state, and the frequency injection adaptive droop control is adopted when the system power changes. Although the control method avoids the influence of low-amplitude alternating current signals on the bus voltage when the system is in a steady state, when the power of the direct current micro-grid changes frequently, the system may be unstable due to frequent droop control switching.
In the above methods, the influence of the State of Charge (SOC) of the battery on the system power regulation effect is not considered. Wu Qingfeng, sun Xiaofeng, wang Yanan and the like (micro-grid distributed energy storage system SOC balance strategy based on distributed droop control, 2018,33 (06): 1247-1256) indicate that frequent power changes in a direct current micro-grid can cause SOC changes of batteries connected in parallel, once SOC differences among the batteries connected in parallel are too large, overcharge or overdischarge phenomena can occur to partial batteries, and the batteries can be damaged in extreme casesAnd further, stability of the system is deteriorated, so that it is important to maintain SOC balance between the batteries. Since the control of the energy storage unit belongs to the equipment level control, the droop control is still applicable, liu Xiaonan, sun Kai, huang Lipei and the like (a load power dynamic distribution method with a bus voltage drop compensation function in a direct current microgrid energy storage system, the Chinese motor engineering report, 2013,33 (16): 37-46) indicates that in order to realize the SOC balance among the storage batteries, the storage batteries with higher SOC must be required to discharge or absorb higher power, and the storage batteries with lower SOC discharge or absorb lower power, that is, the storage batteries with higher SOC correspond to a large droop coefficient in the droop control, and the storage batteries with lower SOC correspond to a small droop coefficient. Lu X N, sun K, guerrero J M (State-of-Charge Balance Using Adaptive drag Control for Distributed Energy Storage Systems in DC Microgrid Applications [ J]IEEE Transactions on Industrial Electronics,2014,61 (6): 2804-2815) proposed an improved droop control strategy based on the energy storage battery SOC, but this improved droop control can only achieve SOC equalization when the battery is discharging, and has certain limitations. Diaz N L, dragevic T, vasquez JC (Intelligent distributed generation and storage units for DC microorganisms-a new control on cooperative control with communication control [ J]IEEE Transaction on Smart Grid,2014,5 (5): 2476-2485) utilizes fuzzy algorithm to improve the control of SOC balance droop of the storage battery, and realizes adaptive power distribution during charging and discharging of the storage battery, but the power distribution effect of the method during discharging of the storage battery is poor. Lu X N, sun K, guerrero J M (Double-queue State-of-Charge-Based Droop Control Method for Distributed Energy Storage Systems in Autonomous DC Microgrids [ J]IEEE Transactions on Smart Grid,2015,6 (1): 147-157) then proposes a dual-quadrant droop control strategy based on the energy storage device SOC, which links the droop coefficient to the SOC of the battery: droop coefficient and SOC during charging n Is in direct proportion; droop coefficient and SOC during discharge n In inverse proportion. Oliveira T R, silva W G, donoso P F (Distributed Secondary Level Control for Energy Storage Management in DC Mic)rogrids[J]IEEE Transactions on Smart Grid,2016,8 (6): 2597-2607) improves the control strategy in the dual-quadrant droop control strategy based on the energy storage device SOC, and the SOC is used n Replacement is exp [ p (SOC-ASOC)]And (both p and A are regulating coefficients), the equalizing speed of the SOC of the storage battery is further improved, but the two schemes are relatively high in dependence on communication, and the selection of the coefficients is relatively complex, so that the reliability is not high. Bhosale R, gupta R, agarwal V (A Novel Control Stratagene to Achieve SOC Balancing for Batteries in a DC micro grid with draw Control [ J]IEEE Transactions on Industry Applications,2021,57 (4): 4196-4206) further proposes a control strategy for SOC balancing without droop control that generates a common time reference (T) through the voltage control loop of the battery ref ) Reuse of T ref The output current of the storage battery is controlled, the stability of the bus voltage is guaranteed, and meanwhile SOC balance is achieved, but the control strategy is complex in structure, and when the control strategy works together with other units in a cooperative mode, the robustness of the whole system is poor.
In short, when the load power in the optical storage charging dc micro-grid changes, the bus voltage and the power condition of the storage battery pack also change, and in order to reduce the bus voltage regulation deviation and improve the power distribution precision between the storage battery packs, U-P droop control is often used to manage the storage batteries. In practical applications, however, due to the existence of line impedance, when the system power changes, the power distributed by each storage battery pack cannot be truly balanced. In the past, the SOC between the storage battery packs has large deviation, so that the phenomenon of overcharge or overdischarge of part of the storage battery packs is caused, the storage battery is damaged under extreme conditions, and the normal operation of a system is influenced.
Disclosure of Invention
In order to solve the problems, the invention provides an improved droop control method and system of a storage battery based on SOC (system on chip), which can reduce the regulation deviation of the bus voltage and improve the power distribution precision between storage battery groups by improving droop control when the load power in an optical storage charging direct current micro-grid changes and the power conditions of the bus voltage and a storage battery pack change accordingly. In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
an improved droop control method for a storage battery based on SOC comprises the following steps:
s1, acquiring the state of charge (SOC) of each storage battery, and calculating the average state of charge and the average depth of discharge of the storage batteries based on the SOC;
s2, improving the droop coefficient by using PI control with the SOC balance between the storage batteries as a target based on the average charge state and the average discharge depth obtained in the step S1;
s3, calculating a power equalization compensation item of each storage battery by utilizing PI control with the aim of realizing power equalization among the storage batteries;
s4, calculating a voltage deviation compensation item by utilizing PI control with the aim of realizing the consistency of the output voltages of the storage battery interface converters;
and S5, adjusting the output reference voltage of each storage battery interface converter according to the improved droop coefficient obtained in the step S2, the power average compensation term obtained in the step S3 and the voltage deviation compensation term obtained in the step S4.
In step S2, the modified droop coefficient is expressed as:
Figure BDA0004020603630000031
in the formula (I), the compound is shown in the specification,
Figure BDA0004020603630000032
represents the SOC balance droop coefficient of the ith storage battery, namely the improved droop coefficient delta d i For the adjustment of the sag factor of the i-th battery, d i Representing the U-P droop coefficient of the ith battery interface converter;
adjustment term Δ d of droop coefficient of the ith storage battery i The expression of (c) is:
Figure BDA0004020603630000041
in the formula, k P-SOC Indicating the proportionality coefficient, k, for regulating the SOC balance I-SOC Represents an integration coefficient for adjusting the SOC equalization, s represents a complex variable,
Figure BDA0004020603630000042
indicating the average state of charge, SOC, of the i-th battery i Indicates the state of charge of the ith battery,
Figure BDA0004020603630000043
indicating the mean depth of discharge, DOD, of the ith cell i Indicating the depth of discharge, P, of the ith cell i And the output power of the ith battery interface converter is shown.
In step S3, the calculation formula of the power equipartition compensation term of the storage battery is:
Figure BDA0004020603630000044
in the formula, k P-P Coefficient of proportionality, k, representing the mean of the regulated power I-P An integral coefficient representing the average of the regulated power, s represents a complex variable,
Figure BDA0004020603630000045
represents the mean value of the normalized unit output power, is->
Figure BDA0004020603630000046
Represents the power equalization compensation term of the i-th battery>
Figure BDA0004020603630000047
The normalized unit output power of the i-th battery is shown.
Normalized unit output power of the i-th storage battery
Figure BDA0004020603630000048
The calculation formula of (c) is:
Figure BDA0004020603630000049
in the formula (I), the compound is shown in the specification,
Figure BDA00040206036300000410
indicating the virtual power of the i-th battery, P i The output power of the ith storage battery interface converter is represented;
virtual power of the i-th storage battery
Figure BDA00040206036300000411
The calculation formula of (2) is as follows:
Figure BDA00040206036300000412
in the formula,. DELTA.U set A set value representing the deviation of the dc bus voltage,
Figure BDA00040206036300000413
indicates the SOC balance droop coefficient of the ith storage battery, namely the improved droop coefficient, and->
Figure BDA00040206036300000414
P r Indicating rated value, Δ U, of battery output power max And the maximum deviation value of the direct current bus voltage is shown.
In step S4, the calculation formula of the voltage deviation compensation term is:
Figure BDA00040206036300000415
in the formula, k P-U Proportionality coefficient, k, representing deviation of regulated voltage I-U An integral coefficient representing the deviation of the adjustment voltage,
Figure BDA00040206036300000416
represents the ith storageA voltage deviation compensation term of the battery, s representing a complex variable, based on the comparison result of the comparison result>
Figure BDA00040206036300000417
Represents the mean value of the output voltage of the battery interface converter, and/or>
Figure BDA00040206036300000418
Representing the nominal value of the dc bus voltage.
In step S5, the calculation formula of the regulated output reference voltage is:
Figure BDA00040206036300000419
in the formula (I), the compound is shown in the specification,
Figure BDA00040206036300000420
represents the output reference voltage, < > or < > of the improved i-th battery interface converter>
Figure BDA00040206036300000421
Represents the nominal value of the DC bus voltage, is greater than or equal to>
Figure BDA00040206036300000422
Represents the power equalization compensation term of the i-th battery>
Figure BDA00040206036300000423
Indicates a voltage deviation compensation term for the i-th battery>
Figure BDA0004020603630000051
Represents the SOC balance droop coefficient of the ith storage battery, namely the improved droop coefficient, P i And the output power of the ith battery interface converter is shown.
An SOC-based battery improved droop control system, comprising:
a state of charge acquisition calculation module: the system comprises a controller, a storage battery, a controller and a controller, wherein the controller is used for acquiring the state of charge (SOC) of each storage battery and calculating the average state of charge and the average depth of discharge based on the SOC;
droop coefficient improvement module: the device is used for acquiring the average charge state and the average depth of discharge output by the calculation module based on the charge state and improving the droop coefficient of the storage battery by using PI control with the SOC balance among the storage batteries as a target;
the power equalization compensation module: the device is used for calculating a power sharing compensation item by utilizing PI control based on the power sharing between the storage batteries as a target;
the voltage deviation compensation module: the device is used for calculating a voltage deviation compensation item by utilizing PI control based on the aim that the output voltages of the storage battery interface converters are consistent;
an output reference voltage regulation module: and the output reference voltage of each storage battery interface converter is adjusted based on the improved droop coefficient output by the droop coefficient improving module, the power average compensation item output by the power average compensation module and the voltage deviation compensation item output by the voltage deviation compensation module.
The invention has the beneficial effects that:
the improved droop control based on the SOC is provided for the storage battery, and the secondary control of virtual power regulation and bus voltage recovery regulation is introduced on the premise of ensuring the SOC balance of the storage battery so as to realize the power sharing among the storage batteries connected in parallel; when the system power changes, the voltage fluctuation is small, and the recovery time is short; the PI control is adopted, so that the bus voltage regulation precision is effectively improved, the deviation of the direct current bus voltage is reduced, and the SOC balance, the power equalization and the bus voltage regulation among the storage batteries are realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic flow chart of the present application.
Fig. 2 is a diagram of a dual loop control architecture.
Fig. 3 is a schematic diagram of the secondary regulation of the present application.
Fig. 4 is a graph showing a change in SOC of a battery in accordance with a conventional droop control.
Fig. 5 is a change curve of the SOC of the battery according to the present application.
Fig. 6 is a graph of battery power distribution for conventional droop control.
Fig. 7 is a power distribution diagram of the battery according to the present application.
Fig. 8 is a simulation comparison graph of the bus voltage regulation effect of the present application and the conventional droop control.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art based on the embodiments of the present invention without inventive step, are within the scope of the present invention.
For n parallel storage batteries on a direct current bus of a light storage and charging direct current micro-grid, the expression of the traditional U-P droop control is as follows:
Figure BDA0004020603630000061
in the formula (I), the compound is shown in the specification,
Figure BDA0004020603630000062
indicating the output reference voltage, P, of the i-th battery interface converter i The output power of the ith storage battery interface converter is represented; />
Figure BDA0004020603630000063
A nominal value representing the dc bus voltage; d i The value range of the U-P droop coefficient of the ith battery interface converter is as follows:
Figure BDA0004020603630000064
in the formula, Δ U max Represents the maximum deviation value, P, allowed by the DC bus voltage r A rated value representing the output power of the battery; delta U set Set value, P, representing the deviation of the DC bus voltage set Set values representing output power of the storage battery, each satisfying Δ U set <ΔU max ，P set <P r 。
Example 1: an improved droop control method for a storage battery based on SOC comprises the following steps:
s1, acquiring the SOC of each storage battery, and calculating the average SOC and the average depth of discharge of the storage batteries based on the SOC;
the calculation formula of the average state of charge of the storage battery is as follows:
Figure BDA0004020603630000065
in the formula (I), the compound is shown in the specification,
Figure BDA0004020603630000066
represents the average state of charge of the ith battery, n represents the total number of batteries, SOC i Indicating the state of charge of the ith battery. Specifically, the SOC can be obtained by first measuring the output current of the battery and then based on an ampere-hour integration method, which is not described in detail in this embodiment of the prior art.
Figure BDA0004020603630000067
In the formula, DOD i Indicating the depth of discharge of the i-th battery and DOD i ＝1-SOC i ，
Figure BDA0004020603630000068
Indicates the ith storage batteryAverage depth of discharge of.
S2, improving the droop coefficient by using PI control with the SOC balance between the storage batteries as a target based on the average charge state and the average discharge depth obtained in the step S1;
the expression of the improved droop coefficient is as follows:
Figure BDA0004020603630000069
in the formula (I), the compound is shown in the specification,
Figure BDA0004020603630000071
indicates the SOC balance droop coefficient of the i-th storage battery, namely the improved droop coefficient delta d i For the adjustment term of the droop coefficient of the ith storage battery, the corresponding expression is as follows:
Figure BDA0004020603630000072
in the formula, k P-SOC Indicating the proportionality coefficient, k, for regulating the SOC balance I-SOC Denotes an integration coefficient for adjusting the SOC equalization, and s denotes a complex variable.
In this application introduces battery SOC to U-P flagging control, changes the size of flagging coefficient through battery SOC, realizes that SOC between the battery is balanced, consequently, the expression after the update of output reference voltage is:
Figure BDA0004020603630000073
s3, calculating a power equalization compensation item of each storage battery by utilizing PI control with the aim of realizing power equalization among the storage batteries;
from the equations (5) and (6), it can be seen that the SOC equalization droop coefficient
Figure BDA0004020603630000074
It is adaptively changed according to the SOC or DOD of the i-th battery. In thatDuring the period of the discharge, the discharge is carried out, when the storage battery i has SOC higher than->
Figure BDA0004020603630000075
When it is too low, the droop coefficient->
Figure BDA0004020603630000076
Will adaptively decrease; when the SOC of the battery i is lower than +>
Figure BDA0004020603630000077
When it is too low, the droop coefficient->
Figure BDA0004020603630000078
Will increase adaptively. However, when the inter-battery SOC deviation is excessively large, such a problem occurs: SOC balance droop coefficient->
Figure BDA0004020603630000079
The relationship in equation (2) may not be satisfied, thereby defeating the proposed control strategy. To avoid this problem, virtual power P is introduced v To satisfy equalized droop coefficient>
Figure BDA00040206036300000710
The corresponding expression is:
Figure BDA00040206036300000711
in the formula (I), the compound is shown in the specification,
Figure BDA00040206036300000712
represents the virtual power of the i-th battery>
Figure BDA00040206036300000713
ΔU set <ΔU max 。/>
Since the line impedance can affect the power sharing effect between the storage batteries, in order to realize the power sharing between the storage batteries, a normalized unit is introduced in the improved droop controlOutput power
Figure BDA00040206036300000714
The calculation formula is as follows:
Figure BDA00040206036300000715
in the formula (I), the compound is shown in the specification,
Figure BDA00040206036300000716
and represents the normalized unit output power of the i-th battery.
The power average compensation term of the storage battery is calculated by utilizing PI control, and the calculation formula is as follows:
Figure BDA00040206036300000717
in the formula, k P-P Coefficient of proportionality, k, representing the mean of the regulated power I-P Represents an integral coefficient of the adjustment power average,
Figure BDA00040206036300000718
means representing the mean value of the normalized unit output power, based on the mean value of the normalized unit output power>
Figure BDA00040206036300000719
Represents the power equalization compensation term of the i-th battery>
Figure BDA00040206036300000720
And represents the normalized unit output power of the i-th battery.
Average value of normalized unit output power
Figure BDA00040206036300000721
The calculation formula of (2): i.e. i
Figure BDA00040206036300000722
S4, calculating a voltage deviation compensation item by using PI control with the aim of realizing consistency of the output voltage of each storage battery interface converter;
in addition, in order to further improve the regulation effect of the bus voltage, a voltage deviation compensation item is added in the secondary control
Figure BDA0004020603630000081
And calculating a voltage deviation compensation term of the storage battery by using PI control, wherein the calculation formula is as follows:
Figure BDA0004020603630000082
in the formula, k P-U Proportionality coefficient, k, representing deviation of regulated voltage I-U An integral coefficient representing the deviation of the adjustment voltage,
Figure BDA0004020603630000083
represents a voltage deviation compensation term which represents the i-th battery in the case of secondary control>
Figure BDA0004020603630000084
The average value of the output voltage of the battery interface converter is shown.
S5, adjusting the output reference voltage of each storage battery interface converter according to the improved droop coefficient obtained in the step S2, the power average compensation item obtained in the step S3 and the voltage deviation compensation item obtained in the step S4;
as shown in fig. 1, the overall expression of the droop control strategy improved according to the combination of equations (7), (10) and (12) is:
Figure BDA0004020603630000085
in the formula (I), the compound is shown in the specification,
Figure BDA0004020603630000086
indicating an improved i-th battery interfaceThe output of the converter is referenced to the voltage.
When the regulation is specifically controlled, the reference voltage is output by adopting double-loop control as shown in figure 2
Figure BDA0004020603630000087
And the actual output voltage U bati Comparing and obtaining the reference value of the current by the voltage control loop>
Figure BDA0004020603630000088
Current reference value and actual output current U ibati Compared with the prior art, the current control loop obtains the PWM driving waveform, and the voltage of the converter is controlled by the PWM driving waveform, so that the output of the storage battery is controlled. The improved droop control in the application only needs low-bandwidth communication, and SOC balance, power equalization and bus voltage regulation among the storage batteries can be achieved. In addition, the application adopts an empirical adjustment method to determine the PI parameters: the scaling factor P is adjusted first (from the middle to both sides) and then the integral factor I is adjusted (from 0 to large).
Example 2: an SOC-based battery improved droop control system, comprising:
a state of charge acquisition calculation module: the system comprises a controller, a storage battery, a controller and a controller, wherein the controller is used for acquiring the state of charge (SOC) of each storage battery and calculating the average state of charge and the average depth of discharge based on the SOC;
droop coefficient improvement module: the device is used for acquiring the average state of charge and the average depth of discharge output by the calculation module based on the state of charge, and improving the droop coefficient of the storage battery by using PI control with the SOC balance between the storage batteries as a target;
the power equalization compensation module: the power equalization compensation item is calculated by utilizing PI control based on the power equalization between the storage batteries as a target;
the voltage deviation compensation module: the device is used for calculating a voltage deviation compensation item by utilizing PI control based on the aim that the output voltages of the storage battery interface converters are consistent;
an output reference voltage regulation module: and the output reference voltage of each storage battery interface converter is adjusted based on the improved droop coefficient output by the droop coefficient improving module, the power average compensation item output by the power average compensation module and the voltage deviation compensation item output by the voltage deviation compensation module. The output end of the output reference voltage regulating module is connected with the storage battery interface converter, so that the output of the storage battery interface converter can be regulated conveniently.
In this embodiment, the calculation formulas of the data such as the average state of charge, the average depth of discharge, the power average compensation term, the voltage deviation compensation term, and the improved droop coefficient are the same as those in embodiment 1.
Fig. 3 shows a secondary regulation process of the improved droop control of the present application, wherein a solid line represents the U-P characteristic curve of the initial droop control of the battery, i.e., the conventional droop control method, and a dashed line represents the U-P characteristic curve of the present application, i.e., the improved droop control after the secondary regulation is introduced. Due to the existence of line impedance, the two storage batteries 1 and 2 do not realize power equalization and work at points A1 and A2 respectively, and a power equalization regulation term delta U is introduced p1 And Δ U p2 And then, the working point is moved from A1 and A2 to A point, so that the power sharing of the two storage batteries is realized. Further, in the voltage deviation compensation term Δ U U The operating point of the battery is shifted from point a to point B, and the average voltage of both is restored to the nominal value.
The simulation model of the light storage charging direct current micro-grid is built in MATLAB/Simulink, a photovoltaic power generation unit, an electric vehicle charging unit and two groups of storage batteries are arranged in the simulation model, a traditional droop control strategy and the improved droop control strategy are respectively adopted for the storage batteries, the photovoltaic power generation unit and the electric vehicle charging load are equivalent to a constant-power direct current power supply, the effectiveness of the improved droop control is verified, and specific simulation parameters are shown in table 1.
TABLE 1 improved droop control SOC balance simulation parameters
Figure BDA0004020603630000091
The following is a simulation of the SOC balance effect of the storage battery, the photovoltaic power generation unit provides 3000W of constant output power, the initial charging load power of the electric vehicle is 2000W, the absorption power of the load is increased to 3500W at 2s, and the charging load power of the electric vehicle is decreased to 2000W at 4 s. As can be seen from fig. 4 and 5, the SOC of the battery increases within 0-2s, which indicates that the battery absorbs power from the dc bus, suppressing power redundancy in the system; within 2-4s, the SOC of the storage battery is reduced, which indicates that the storage battery outputs power to the direct current bus to make up for the power shortage in the system; the case in 4s-6s is the same as the case in 0-2s, and will not be described. As can be seen by comparing fig. 4 and 5, the SOC deviation between the two batteries using the conventional droop control becomes larger and larger as time goes by; the SOC deviation between the two storage batteries adopting the improved droop control becomes smaller and smaller, and at about t =4.6s, the SOC of the two storage batteries is consistent and can be kept balanced.
In order to better verify the power sharing effect of the present application, it is necessary to avoid the influence of the SOC equalization adjustment of the storage batteries on the power sharing, so that the initial SOCs of the two storage batteries are both set to 66%, and other simulation parameters are the same as those in table 1. As can be seen from fig. 6 and 7, in 0 to 2s, the storage battery absorbs power from the dc bus, suppressing power redundancy in the system; in 2-4s, the storage battery outputs power to the direct current bus to make up for the power shortage in the system; the case in 4s-6s is the same as the case in 0-2s, and will not be described. As can be seen from fig. 6, due to the line impedance, when the system power changes, the conventional droop control strategy cannot ensure power sharing between the storage batteries, a certain distribution error exists, and the adjustment speed is slow. Compared with the scheme shown in fig. 7, the improved droop control strategy can effectively reduce the influence of line impedance on power distribution precision, realize power equalization among storage batteries, and when the system power changes, the regulation speed is faster, so that the effectiveness of the improved droop control on power deviation compensation is fully verified.
Fig. 8 shows a change curve of the dc bus voltage during the improved droop control, that is, the droop control and the conventional droop control, and it can be seen from the figure that, compared with the conventional droop control, the droop control and the conventional droop control can reduce the voltage deviation of the dc bus, and when the system power changes, the fluctuation of the dc bus voltage is smaller and the recovery is faster.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (8)

1. An improved droop control method for a storage battery based on SOC is characterized by comprising the following steps:
s1, acquiring the state of charge (SOC) of each storage battery, and calculating the average state of charge and the average depth of discharge of the storage batteries based on the SOC;
s2, improving the droop coefficient by using PI control with the SOC balance among the storage batteries as a target based on the average charge state and the average discharge depth obtained in the step S1;
s3, calculating a power equalization compensation item of each storage battery by using PI control with the aim of realizing power equalization among the storage batteries;
s4, calculating a voltage deviation compensation item by utilizing PI control with the aim of realizing the consistency of the output voltages of the storage battery interface converters;
and S5, adjusting the output reference voltage of each storage battery interface converter according to the improved droop coefficient obtained in the step S2, the power average compensation term obtained in the step S3 and the voltage deviation compensation term obtained in the step S4.
2. The improved droop control method for the SOC-based battery according to claim 1, wherein in step S2, the improved droop coefficient is expressed by:
Figure FDA0004020603620000011
in the formula (I), the compound is shown in the specification,
Figure FDA0004020603620000012
showing the SOC balance droop of the ith batteryCoefficient, i.e. sag coefficient, Δ d, after improvement i For the adjustment of the sag factor of the i-th battery, d i Representing the U-P droop coefficient of the ith battery interface converter;
adjustment term delta d of droop coefficient of the ith storage battery i The expression of (a) is:
Figure FDA0004020603620000013
in the formula, k P-SOC Indicating the proportionality coefficient, k, for regulating the SOC balance I-SOC Represents an integration coefficient for adjusting the SOC equalization, s represents a complex variable,
Figure FDA0004020603620000014
indicating the average state of charge, SOC, of the i-th battery i Indicates the state of charge of the ith battery,
Figure FDA0004020603620000015
indicating the mean depth of discharge, DOD, of the ith cell i Indicating the depth of discharge, P, of the ith cell i And the output power of the ith battery interface converter is shown.
3. The improved droop control method for the SOC-based battery according to claim 1, wherein in step S3, the calculation formula of the power-share compensation term of the battery is:
Figure FDA0004020603620000016
in the formula, k P-P Coefficient of proportionality, k, representing the mean of the regulated power I-P An integral coefficient representing the average of the regulated power, s represents a complex variable,
Figure FDA0004020603620000017
representing normalized unit outputOut of the mean value of the power, is greater or less>
Figure FDA0004020603620000018
Represents the power equalization compensation term of the i-th battery>
Figure FDA0004020603620000019
The normalized unit output power of the i-th battery is shown.
4. The method of claim 3 wherein the normalized unity output power of the ith battery
Figure FDA00040206036200000110
The calculation formula of (2) is as follows:
Figure FDA0004020603620000021
in the formula (I), the compound is shown in the specification,
Figure FDA0004020603620000022
indicating the virtual power of the i-th battery, P i The output power of the ith storage battery interface converter is represented; />
Virtual power of the i-th storage battery
Figure FDA0004020603620000023
The calculation formula of (2) is as follows:
Figure FDA0004020603620000024
in the formula, Δ U set A set value representing the deviation of the dc bus voltage,
Figure FDA0004020603620000025
represents the ithThe SOC of the accumulator equalizes the droop factor, i.e. the droop factor after improvement, and>
Figure FDA0004020603620000026
ΔU set <ΔU max ，P r indicating rated value, Δ U, of battery output power max And the maximum deviation value of the direct current bus voltage is shown.
5. The improved droop control method for SOC-based batteries according to claim 1, wherein in step S4, the voltage deviation compensation term is calculated by the formula:
Figure FDA0004020603620000027
in the formula, k P-U Proportionality coefficient, k, representing deviation of regulated voltage I-U An integral coefficient representing the deviation of the adjustment voltage,
Figure FDA0004020603620000028
represents the voltage deviation compensation term of the i-th battery, s represents a complex variable, and/or>
Figure FDA0004020603620000029
Represents the mean value of the output voltage of the battery interface converter, and/or>
Figure FDA00040206036200000210
Representing the nominal value of the dc bus voltage.
6. The improved droop control method for SOC-based batteries according to claim 1, wherein in step S5, the formula for calculating the regulated output reference voltage is:
Figure FDA00040206036200000211
in the formula (I), the compound is shown in the specification,
Figure FDA00040206036200000212
represents the output reference voltage, < > or < > of the improved i-th battery interface converter>
Figure FDA00040206036200000213
Represents the nominal value of the DC bus voltage, is greater than or equal to>
Figure FDA00040206036200000214
Represents the power equalization compensation term of the i-th battery>
Figure FDA00040206036200000215
Represents the voltage deviation compensation term of the i-th battery>
Figure FDA00040206036200000216
Represents the SOC balance droop coefficient of the ith storage battery, namely the improved droop coefficient P i And the output power of the ith battery interface converter is shown.
7. An SOC-based battery droop control system, comprising:
a state of charge acquisition calculation module: the system is used for acquiring the state of charge (SOC) of each storage battery and calculating the average state of charge and the average depth of discharge based on the SOC;
droop coefficient improvement module: the device is used for acquiring the average charge state and the average depth of discharge output by the calculation module based on the charge state and improving the droop coefficient of the storage battery by using PI control with the SOC balance among the storage batteries as a target;
the power equalization compensation module: the power equalization compensation item is calculated by utilizing PI control based on the power equalization between the storage batteries as a target;
the voltage deviation compensation module: the device is used for calculating a voltage deviation compensation item by utilizing PI control based on the aim that the output voltages of the storage battery interface converters are consistent;
an output reference voltage regulation module: and the output reference voltage of each storage battery interface converter is adjusted based on the improved droop coefficient output by the droop coefficient improving module, the power average compensation item output by the power average compensation module and the voltage deviation compensation item output by the voltage deviation compensation module.
8. The SOC-based battery improved droop control system of claim 7, wherein the improved droop coefficient is expressed by:
Figure FDA0004020603620000031
in the formula (I), the compound is shown in the specification,
Figure FDA0004020603620000032
represents the SOC balance droop coefficient of the ith storage battery, namely the improved droop coefficient delta d i For the adjustment of the sag factor of the i-th battery, d i The U-P droop coefficient of the ith storage battery interface converter is represented;
adjustment term Δ d of droop coefficient of the ith storage battery i The expression of (a) is:
Figure FDA0004020603620000033
in the formula, k P-SOC Coefficient of proportionality, k, representing the adjustment of SOC equalization I-SOC Represents an integration coefficient for adjusting the SOC equalization, s represents a complex variable,
Figure FDA0004020603620000034
indicating the average state of charge, SOC, of the i-th battery i Indicates the state of charge of the ith battery,
Figure FDA0004020603620000035
means average depth of discharge, DOD, of the ith cell i Indicating the depth of discharge, P, of the ith cell i And the output power of the ith battery interface converter is shown. />
CN202211727649.4A 2022-12-27 2022-12-27 SOC-based storage battery improved droop control method and system Pending CN115882490A (en)

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CN116094016A (en) * 2023-04-11 2023-05-09 深圳市德兰明海新能源股份有限公司 Energy storage equipment alternating current multiphase system and electric quantity balance control method thereof
CN116191516A (en) * 2023-04-03 2023-05-30 国网江苏省电力有限公司南通供电分公司 Multi-port energy hub multi-converter direct-current voltage/droop control method based on honeycomb active power distribution network
CN116565827A (en) * 2023-06-01 2023-08-08 广东工业大学 Injection frequency-based SOC (State of charge) balance control strategy of direct-current micro-grid energy storage system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116191516A (en) * 2023-04-03 2023-05-30 国网江苏省电力有限公司南通供电分公司 Multi-port energy hub multi-converter direct-current voltage/droop control method based on honeycomb active power distribution network
CN116191516B (en) * 2023-04-03 2024-03-15 国网江苏省电力有限公司南通供电分公司 DC voltage/power droop control method for multi-port energy hub multi-converter
CN116094016A (en) * 2023-04-11 2023-05-09 深圳市德兰明海新能源股份有限公司 Energy storage equipment alternating current multiphase system and electric quantity balance control method thereof
CN116565827A (en) * 2023-06-01 2023-08-08 广东工业大学 Injection frequency-based SOC (State of charge) balance control strategy of direct-current micro-grid energy storage system
CN116565827B (en) * 2023-06-01 2024-01-02 广东工业大学 Injection frequency-based SOC (State of charge) balance control strategy of direct-current micro-grid energy storage system

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