Reconfigurable novel energy storage distributed cooperative operation control method and system

Abstract

The invention discloses a reconfigurable novel energy storage distributed cooperative operation control method and system, and the method comprises the steps: obtaining a virtual impedance correction item through the feedback processing of auxiliary control uQi based on a reactive power distribution error during reactive power distribution; secondly, carrying out secondary distribution on reactive power output by each virtual synchronous generator, and distributing error self-adaptive virtual inductance and resistance through the reactive power; a virtual impedance voltage drop under a dq coordinate system is calculated through an inverter output current and an angular frequency, a dq component of an output voltage is controlled based on P-f, Q-E, a dq component of a voltage loop input reference value is output, and finally a PWM signal is output to the inverter. According to the invention, voltage frequency recovery and flexible power distribution of the reconfigurable novel energy storage system are realized, the influence of circulating current is reduced, stable and reliable operation of the energy storage system is ensured, the cycle life of the energy storage system is prolonged, and the practicability is relatively good.

Description

Technical Field

[0001] The present invention belongs to the technical field of power energy storage operation control, and specifically relates to a new type of reconfigurable energy storage distributed collaborative operation control method and system. Background Art

[0002] With the rapid development of electrochemical energy storage, the inherent safety of energy storage systems has become increasingly prominent, and the "short board effect" of the battery system brought about by the fixed series-parallel mode of traditional battery energy storage systems is the fundamental reason for the safety and economic problems of current electrochemical energy storage systems. In recent years, reconfigurable battery energy storage systems have received widespread attention. Each battery pack in the system is deeply coupled with a control switch, which can quickly diagnose and remove faulty batteries to ensure the normal operation of electrochemical energy storage, greatly improving the availability and reliability of the system, and providing a new path for the safety and economy of electrochemical energy storage systems.

[0003] In practical applications, in order to meet the requirements of high-power power supply systems, it is necessary to use inverters to realize parallel operation of multiple energy storage systems, which can effectively improve the reliability of power supply of energy storage systems. Due to the differences in output impedance and line impedance of each energy storage system, circulation may occur between energy storage systems; at the same time, there is a deviation in the output voltage frequency of each energy storage system, which makes the power distribution effect poor.

[0004] In response to the problems of communication interconnection, frequency recovery, power distribution, etc. in the above parallel steady-state operation, domestic and foreign scholars have proposed a consistency-based parallel virtual synchronous generator (virtual synchronous generator) distributed control strategy, aiming to achieve system frequency recovery and flexible power distribution, and ensure the reliability of parallel operation of energy storage systems. However, the above studies are all carried out on traditional energy storage systems, and there are relatively few studies on the parallel operation of multiple reconfigurable battery energy storage systems. It is urgent to consider the structural characteristics of reconfigurable battery energy storage and combine the existing research foundation to achieve voltage frequency recovery and flexible power distribution of reconfigurable battery energy storage. Summary of the invention

[0005] The purpose of the present invention is to provide a distributed collaborative operation control method and system for a reconfigurable new energy storage, aiming to solve the above-mentioned problems and realize flexible power allocation of the reconfigurable new energy storage.

[0006] The present invention is mainly achieved through the following technical solutions:

[0007] A novel reconfigurable energy storage distributed coordinated operation control method includes a plurality of virtual synchronous generators connected in parallel, wherein an inverter is provided on the DC side of the virtual synchronous generator, and the inverter is controlled by active power distribution and reactive power distribution to realize flexible distribution of power output, wherein the reactive power distribution includes the following steps:

[0008] Step S1: When the line impedances of the virtual synchronous generators are inconsistent, an adaptive virtual impedance technology is introduced to perform secondary distribution of the reactive power output by the virtual synchronous generators;

[0009] Step S11: First, obtain u according to the reactive power distribution consistency algorithm Qi :

[0010]

[0011] Among them, u Qi is the target voltage;

[0012] c Q is the adjustment coefficient;

[0013] e Qi It is the accumulated sum of reactive power deviation;

[0014] m is the number of virtual synchronous generators;

[0015] f(Q i ) is the objective function of the i-th virtual synchronous generator;

[0016] f(Q j ) is the objective function of the jth virtual synchronous generator;

[0017] l ij is the element in the Laplace matrix L of the i-th row and the j-th column, used to characterize the communication connection relationship between the virtual synchronous generators;

[0018] Step S12: Then, the reactive power distribution error is controlled by auxiliary control u Qi Feedback to a proportional-integral PI controller to obtain a virtual impedance correction term. The control equation of the proportional-integral PI controller is as follows:

[0019]

[0020] Where, s is the Laplace operator;

[0021] K pQ and K iQ are the proportional coefficient and integral coefficient of the PI controller respectively,

[0022] δQ i is the virtual impedance correction value;

[0023] Step S13: Obtain reactive power distribution information of adjacent virtual synchronous generators through a distributed communication network to update the local reactive power distribution error, and adaptively adjust its own virtual inductance and resistance according to formula (13):

[0024]

[0025] Among them, L vi and R vi They are adaptive virtual inductance and resistance through reactive power allocation error;

[0026] and are static virtual inductance and resistance respectively, to ensure that the equivalent impedance is inductive;

[0027] k QL and k QR They are used to adjust the proportional gain of virtual inductance and resistance respectively;

[0028] Step S2: Calculate the virtual impedance voltage drop in the dq coordinate system. The calculation formula is as follows:

[0029]

[0030] Where ω0 is the angular frequency of the inverter output;

[0031] u vdi 、u vqi are the components of the voltage drop of the i-th virtual synchronous generator on the d and q axes respectively;

[0032] I odi and I oqi are the components of the output current of the i-th virtual synchronous generator on the d and q axes respectively;

[0033] Step S3: The voltage reference value after introducing virtual impedance control is:

[0034]

[0035] in, and The d and q components of the voltage loop input reference value;

[0036] and The d and q components of the output voltage are controlled by Pf and QE respectively;

[0037] Step S4: performing voltage and current dual closed-loop control based on the voltage reference value and outputting a PWM signal to the inverter.

[0038] In order to better implement the present invention, further, in step S11, the equation for power distribution consistency control of reactive power distribution is:

[0039]

[0040] in, is the state variable in the system;

[0041] Y i and X i are the translation amounts of the Pf and QE droop characteristic curves of the i-th virtual synchronous generator;

[0042] X j is the translation amount of the Pf droop characteristic curve of the jth virtual synchronous generator;

[0043] k pi is the active power-frequency droop coefficient of the i-th virtual synchronous generator;

[0044] k pj is the active power-frequency droop coefficient of the jth virtual synchronous generator;

[0045] According to the continuous average consensus algorithm, if all virtual synchronous generators reach a consensus, then each variable can converge to its average value, that is:

[0046]

[0047] In order to better implement the present invention, further, when the reactive power is distributed according to the rated capacity of the energy storage, the output of each virtual synchronous generator needs to meet the following requirements:

[0048]

[0049] Among them, Q i represents the reactive power output by the i-th virtual synchronous generator;

[0050] Q iref represents the rated reactive power of the i-th virtual synchronous generator;

[0051] Define the objective function f(Q i )=Q i / Q iref , and must meet the following requirements:

[0052]

[0053] Among them, k qi is the reactive power-voltage droop coefficient of the i-th virtual synchronous generator;

[0054] Reference input x iref With the actual input x i The difference Δx i =x iref -(a2-b2x iref )x i , where x i and x iref Q i , Q ireffunction; a2 and b2 are selection coefficients, and their values ​​are determined by the output allocation objective function.

[0055] In order to better implement the present invention, further, the active power distribution includes the following steps:

[0056] Step T1: When the system allocates active power according to the rated capacity of energy storage, the output of each virtual synchronous generator must meet the following requirements:

[0057]

[0058] Among them, P i is the active power output by the i-th virtual synchronous generator;

[0059] P iref is the rated active power of the i-th virtual synchronous generator;

[0060] Define the objective function f(P i )=P i / P iref , and must meet the following requirements:

[0061]

[0062] Among them, k pi is the active power-frequency droop coefficient of the i-th virtual synchronous generator;

[0063] Reference input y iref With the actual input y i The difference Δy i =y iref -(a1+b1y iref )y i , where y i and iref P i , P iref function; a1, b1 are selection coefficients, whose values ​​are determined by the output allocation objective function;

[0064] Step T2: Design a frequency recovery unit based on Pf droop control, and its control equation is:

[0065]

[0066] Among them, J i is the virtual moment of inertia of the i-th virtual synchronous generator;

[0067] ω0 is the system frontal frequency;

[0068] is the angular frequency differential of the i-th virtual synchronous generator;

[0069] ω i is the angular frequency measured for the i-th virtual synchronous generator;

[0070] Y i is the translation amount of the Pf droop characteristic curve of the i-th virtual synchronous generator;

[0071] Step T3: Adjacent virtual synchronous generators exchange their active power deviation information, determine the shift of the Pf droop curve, and modify the active power setting value to shift the droop curve upward from l1 to l2. The operating point becomes C, that is, the frequency is restored to f a , the frequency recovery unit is designed as:

[0072]

[0073] Among them, k i is the frequency recovery coefficient of the i-th virtual synchronous generator;

[0074] k pj is the active power-frequency droop coefficient of the jth virtual synchronous generator;

[0075] Y i * is the differential of the Pf droop characteristic curve shift of the i-th virtual synchronous generator;

[0076] Y j are respectively the translation amounts of the Pf droop characteristic curve of the jth virtual synchronous generator.

[0077] In order to better implement the present invention, further, each reconfigurable new energy storage system is composed of N battery groups connected in series, and the reconfigurable new energy storage performs battery group reconstruction according to the active output of the virtual synchronous generator, including the following steps:

[0078] Step D1: measuring the voltage of each battery pack in real time, and mapping it with the open circuit voltage-state of charge of the battery pack to obtain an initial SOC value;

[0079] Step D2: using the extended Kalman filter method to correct the initial SOC value to achieve accurate estimation of the SOC value of each battery pack;

[0080] Step D3: Sort the SOC values ​​of the battery packs from high to low, and use the active output demand of the virtual synchronous generator as a reconstruction constraint. Control the battery packs through high-frequency power electronic switches, and sequentially merge them into the discharge network from high SOC value to low SOC value until the active output demand of the virtual synchronous generator is met. The reconstruction constraint is as follows:

[0081] P c ≤P≤(1+δ)P(18)

[0082] And P = U bat .I bat ,

[0083] Among them, P c is the active power output demand of the virtual synchronous generator;

[0084] P is the inverter output active power;

[0085] δ is the corresponding safety threshold parameter;

[0086] U bat ,I bat are the voltage and current output by the reconfigurable battery energy storage system respectively.

[0087] The present invention is mainly achieved through the following technical solutions:

[0088] A reconfigurable new energy storage distributed coordinated operation control system is based on the above-mentioned reconfigurable new energy storage distributed coordinated operation control method, the virtual synchronous generator includes a control module, the control module is connected to the inverter through a voltage and current dual closed-loop control module, and the voltage and current dual closed-loop control module is used to output a PWM signal to the inverter;

[0089] The control module includes a reactive power distribution unit, which includes a PI control unit, an adaptive virtual impedance unit and a virtual voltage unit arranged in sequence from front to back. The input end of the PI control unit is connected to a consistency control unit, which is used to make the output of each virtual synchronous generator consistent; the PI control unit is used to control the reactive power distribution error through an auxiliary control u Qi The feedback processing obtains the virtual impedance correction term and sends it to the adaptive virtual impedance unit; the adaptive virtual impedance unit is used to redistribute the reactive power output by each virtual synchronous generator, and outputs it to the virtual voltage unit through the adaptive virtual inductance and resistance of the reactive power distribution error; the virtual voltage unit is used to calculate the virtual impedance voltage drop in the dq coordinate system through the inverter output current and angular frequency, and then control the dq component of the output voltage based on Pf and QE to output the dq component of the voltage loop input reference value.

[0090] In order to better realize the present invention, the control module further includes an active power distribution unit, a frequency recovery unit and a Pf control unit which are arranged in sequence from front to back. The active power distribution unit is used to determine the objective function according to the operating requirements to flexibly distribute the power output; the frequency recovery unit is used to adjust the voltage frequency to restore it to the rated value; the frequency recovery unit is connected to the consistency control unit.

[0091] In order to better implement the present invention, further, it also includes a reconfigurable battery energy storage system, the virtual synchronous generator is connected to the reconfigurable battery energy storage system through a DC-DC conversion circuit, each virtual synchronous generator receives information from other virtual synchronous generators through at least one communication line to determine the communication connection Laplace matrix L, and the reconfigurable battery energy storage system performs constant current discharge control through an interconnected PI constant current discharge controller and a DC-DC conversion circuit.

[0092] In order to better implement the present invention, further, the DC-DC conversion circuit includes an inductor L bat , resistor R bat , capacitor C, switch tube K1 and switch tube K2, and an inductor L connected in series is arranged between the reconfigurable battery energy storage system and the DC side of the inverter. bat , resistor R bat and switch tube K2, the resistor R bat A switch tube K1 is connected in parallel between the switch tube K1 and the switch tube K2, and a capacitor C is connected in parallel between the switch tube K2 and the DC side of the inverter; the PI constant current discharge controller is based on the output current I of the reconfigurable battery energy storage system bat and the expected discharge current The current difference generates a PWM modulation signal and acts on the switch tubes K1 and K2 to perform PI constant current discharge control.

[0093] In order to better implement the present invention, further, each reconfigurable new energy storage system is composed of N battery groups connected in series, and the reconfigurable new energy storage system reconstructs the battery group according to the active output of the virtual synchronous generator, including the following steps:

[0094] Step D1: measuring the voltage of each battery pack in real time, and mapping it with the open circuit voltage-state of charge of the battery pack to obtain an initial SOC value;

[0095] Step D2: using the extended Kalman filter method to correct the initial SOC value to achieve accurate estimation of the SOC value of each battery pack;

[0096] Step D3: Sort the SOC values ​​of the battery packs from high to low, and use the active output demand of the virtual synchronous generator as a reconstruction constraint. Control the battery packs through high-frequency power electronic switches, and sequentially merge them into the discharge network from high SOC value to low SOC value until the active output demand of the virtual synchronous generator is met. The reconstruction constraint is as follows:

[0097] P c ≤P≤(1+δ)P(18)

[0098] And P = U bat .I bat ,

[0099] Among them, P c is the active power output demand of the virtual synchronous generator;

[0100] P is the inverter output active power;

[0101] δ is the corresponding safety threshold parameter;

[0102] U bat ,I bat are the voltage and current output by the reconfigurable battery energy storage system respectively.

[0103] The beneficial effects of the present invention are as follows:

[0104] The present invention realizes the voltage frequency recovery and flexible power distribution of the reconfigurable new energy storage, reduces the influence of circulating current, ensures the stable and reliable operation of the energy storage system, and improves the cycle life of the energy storage system, and has good use and promotion effects. The present invention can realize the power distribution and frequency recovery functions of the system only through a small amount of information interaction between adjacent virtual synchronous generators, and at the same time can reduce the influence of line circulating current and ensure the stable and reliable operation of the energy storage system; secondly, considering the SOC size of each battery group, and combining the active output demand of the virtual synchronous generator, the reconstruction of each battery group in the energy storage is realized, and the cycle life of the energy storage system is improved. The present invention is of great significance to the parallel operation control of the reconfigurable new energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] Figure 1 This is the schematic diagram of the parallel operation of the new reconfigurable energy storage system;

[0106] Figure 2 It is the principle block diagram of the virtual synchronous generator;

[0107] Figure 3 It is a schematic diagram of a DC-DC conversion circuit;

[0108] Figure 4 This is the principle block diagram of the constant current controlled DC-DC conversion circuit;

[0109] Figure 5 It is a principle block diagram of reactive power distribution of the present invention;

[0110] Figure 6 It is a principle block diagram of active power distribution of the present invention;

[0111] Figure 7 This is the schematic diagram of frequency recovery;

[0112] Figure 8 A schematic diagram of the series structure of a battery pack;

[0113] Fig. 9 Schematic diagram of the reconstruction process of the reconfigurable new energy storage in Example 2. DETAILED DESCRIPTION

[0114] Embodiment 1:

[0115] A new type of reconfigurable energy storage distributed collaborative operation control system, such as Figure 1 As shown in Figure 1, the new reconfigurable energy storage parallel operation structure mainly includes m reconfigurable battery energy storage systems and m virtual synchronous generators. Figure 2 As shown, the virtual synchronous generator mainly includes a main circuit and a control system, wherein the main circuit is a conventional grid-connected inverter topology, including a DC side, a DC / AC converter and a filter circuit. Each reconfigurable battery energy storage system is connected to the DC side of the inverter through a DC-DC conversion circuit, and m virtual synchronous generators are connected in parallel through a common bus, and then connected to a three-phase load. The reconfigurable battery energy storage system performs constant current discharge control through a DC-DC conversion circuit. Specifically, the rules of distributed communication of the present invention are defined as follows: there are at least one or two communication lines between the virtual synchronous generators of each energy storage, and each virtual synchronous generator in parallel has at least one communication line for receiving information from other virtual synchronous generators. According to the communication connection information, the communication connection Laplace matrix L can be determined.

[0116] like Figure 3 As shown, the DC-DC conversion circuit includes an inductor L bat , resistor R bat , capacitor C, switch tube K1, switch tube K2. Figure 4 As shown, during constant current discharge control, the output current I of the reconfigurable battery energy storage system is detected in real time bat , the output current I of the reconfigurable battery energy storage system bat and the expected discharge current The current difference is obtained by subtracting, and the obtained current difference generates a PWM modulation signal through a PI constant current discharge controller and acts on the switch tubes K1 and K2 to perform PI constant current discharge control.

[0117] like Figure 2 As shown, the control system of the virtual synchronous generator includes a control module and a voltage-current dual closed-loop control module, wherein the control module is connected to the inverter via the voltage-current dual closed-loop control module, and the voltage-current dual closed-loop control module is used to output a PWM signal to the inverter. The control module includes a reactive power distribution unit and an active power control module.

[0118] like Figure 5 As shown, the reactive power distribution unit includes a consistency control unit, a PI control unit, an adaptive virtual impedance unit and a virtual voltage unit arranged in sequence from front to back, wherein the consistency control unit is used to make the output of each virtual synchronous generator consistent; the PI control unit is used to control u based on the reactive power distribution error through auxiliary controlQ The feedback processing obtains the virtual impedance correction term and sends it to the adaptive virtual impedance unit; the adaptive virtual impedance unit is used to redistribute the reactive power output by each virtual synchronous generator, and outputs it to the virtual voltage unit through the adaptive virtual inductance and resistance of the reactive power distribution error; the virtual voltage unit is used to calculate the virtual impedance voltage drop in the dq coordinate system through the inverter output current and angular frequency, and then control the dq component of the output voltage based on Pf and QE to output the dq component of the voltage loop input reference value.

[0119] like Figure 6 As shown, the active power control module includes an active power distribution unit, a frequency recovery unit and a Pf control unit which are arranged in sequence from front to back. The active power distribution unit is used to determine the objective function according to the operating requirements to flexibly distribute the power output; the frequency recovery unit is used to adjust the voltage frequency to restore it to the rated value; the frequency recovery unit is connected to the consistency control unit.

[0120] The present invention can realize the power distribution and frequency recovery functions of the system through a small amount of information interaction between adjacent virtual synchronous generators, and at the same time reduce the influence of line circulation to ensure the stable and reliable operation of the energy storage system; secondly, considering the SOC size of each battery group and combining the active output demand of the virtual synchronous generator, the reconstruction of each battery group in the energy storage is realized, and the cycle life of the energy storage system is improved. The present invention is of great significance to the parallel operation control of the reconfigurable new energy storage.

[0121] Embodiment 2:

[0122] A novel reconfigurable energy storage distributed collaborative operation control method specifically comprises the following steps:

[0123] 1-1) In the consistency control unit ij is an element in the Laplace matrix L, representing the i-th row and j-th column, which is used to characterize the communication connection relationship between the virtual synchronous generators. The corresponding equation for power distribution consistency control is:

[0124]

[0125] Among them, Y i , X i They respectively represent the translation of the Pf and QE droop characteristic curves of the i-th virtual synchronous generator.

[0126] According to the continuous average consistency algorithm, the algorithm can be described as follows:

[0127]

[0128] Among them, z iis the state variable in the system, c is the diffusion coefficient, a ij is an element in the adjacency matrix, representing the connection relationship between each virtual synchronous generator. When time tends to infinity, each state variable z i tend to be consistent, then:

[0129]

[0130] Among them, avg(z) is the state variable z i The average value of .

[0131] If all virtual synchronous generators reach a consensus, then each variable can converge to its average value, that is:

[0132]

[0133] 1-2) In the active power distribution unit, y i ,y iref P i , P iref function; a1, b1 are selection coefficients, whose values ​​are determined by the output distribution objective function; output Δy i =y iref -(a1+b1y iref )y i is the difference between the reference input and the actual input; define f(P i ), f(P iref ) is the objective function, which is generally a linear function. There are many selection methods, which can be determined according to specific needs. Among them, P i represents the active power output by the i-th virtual synchronous generator; P iref represents the rated active power of the i-th virtual synchronous generator. Assuming that each reconfigurable new energy storage system consists of N battery packs connected in series, the rated active power expression of each virtual synchronous generator is as follows:

[0134]

[0135] Among them, SOC ij represents the capacity of the jth battery pack in the i-th energy storage system; P ij Represents the rated active power of the jth battery pack in the i-th energy storage system.

[0136] When the system distributes active power according to the rated capacity of energy storage, the output of each virtual synchronous generator must meet the following requirements:

[0137]

[0138] Then the objective function is selected as f(P i )=P i / Piref ; The selection coefficient is a1=1, b1=0. And it must satisfy:

[0139]

[0140] Among them, k pi represents the active power-frequency droop coefficient of the i-th virtual synchronous generator.

[0141] 1-3) In the reactive power distribution unit, x i , x iref Q i , Q iref function; a2, b2 are selection coefficients, whose values ​​are determined by the output distribution objective function; output Δx i =x iref -(a2-b2x iref )x i is the difference between the reference input and the actual input; define f(Q i ), f(Q iref ) is the objective function, which is generally a linear function. There are many selection methods, which can be determined according to specific needs. Among them, Q i represents the reactive power output by the i-th virtual synchronous generator; Q iref represents the rated reactive power of the i-th virtual synchronous generator. Assuming that each reconfigurable new energy storage system consists of N battery packs connected in series, the rated reactive power expression of each virtual synchronous generator is as follows:

[0142]

[0143] Among them, SOC ij represents the capacity of the jth battery pack in the i-th energy storage system; Q ij Represents the rated reactive power of the jth battery pack in the i-th energy storage system.

[0144] When the system distributes reactive power according to the rated capacity of energy storage, the output of each virtual synchronous generator must meet the following requirements:

[0145]

[0146] Then the objective function is selected as f(Q i )=Q i / Q iref ; The selection coefficient is a2=1, b2=0. And it must meet the following requirements:

[0147]

[0148] Among them, k qi represents the reactive power-voltage droop coefficient of the i-th virtual synchronous generator.

[0149] When the line impedances of the virtual synchronous generators are inconsistent, the reactive power output by the virtual synchronous generators cannot be distributed in proportion to the rated reactive power of their respective energy storages. It is necessary to introduce adaptive virtual impedance technology to perform secondary reactive power distribution. First, according to the reactive power distribution consistency algorithm of formula (11), u Q , reactive power distribution error is controlled by auxiliary control u Q Feedback to a proportional integral (PI) controller to obtain the virtual impedance correction term, whose control equation is shown in equation (12):

[0150]

[0151] Among them, K pQ and K iQ are the proportional coefficient and integral coefficient of the PI controller, δQ i is the virtual impedance correction value.

[0152] The reactive power distribution information of adjacent virtual synchronous generators is obtained through a distributed communication network to update the local reactive power distribution error and adaptively adjust its own virtual inductance and resistance according to formula (13).

[0153]

[0154] Among them, L vi , R vi They are adaptive virtual inductance and resistance through reactive power distribution error; are static virtual inductance and resistance respectively, to ensure that the equivalent impedance is inductive; k QL With k QR It is used to adjust the proportional gain of virtual inductance and resistance.

[0155] The adaptive virtual impedance technology is implemented in the form of voltage drop. According to the virtual impedance obtained above, the virtual impedance voltage drop in the dq coordinate system can be calculated by the inverter output current and angular frequency. The calculation formula is as follows:

[0156]

[0157] Among them, V vdi and V vqi is the voltage drop component in the dq axis; I odi and I oqi is the dq component of the output current of the i-th virtual synchronous generator.

[0158] The voltage reference value after the introduction of virtual impedance control is:

[0159]

[0160] in, and The dq components of the voltage loop input reference value; and Pf and QE control the dq components of the output voltage.

[0161] 1-4) Design a frequency recovery unit based on Pf droop control, and its control equation is:

[0162]

[0163] Among them, J i is the virtual moment of inertia of the ith virtual synchronous generator, ω i represents the angular frequency measured by the i-th virtual synchronous generator, Y i is the translation amount of the Pf droop characteristic curve of the i-th virtual synchronous generator.

[0164] Taking the frequency recovery of a single virtual synchronous generator as an example, the adjustment process is as follows: Figure 7 As shown. a To set the frequency, P a To set the active power, the initial operating point of the virtual synchronous generator is A. When the load increases, the operating point moves from A to B. At this time, the actual output active power P b With P a There is a deviation, and its frequency is reduced to f b .

[0165] According to step 1-1), the adjacent virtual synchronous generators exchange their active power deviation information, determine the Pf droop curve translation, and modify the active power setting value to make the droop curve shift upward from l1 to l2, and the operating point becomes C, that is, the frequency is restored to f a , the frequency recovery unit can be designed as:

[0166]

[0167] Among them, k i is the frequency recovery coefficient of the i-th virtual synchronous generator; Y i , Y j are the translation amounts of the Pf droop characteristic curves of the i-th and j-th virtual synchronous generators respectively.

[0168] Preferably, the reconfigurable new energy storage performs battery group reconstruction according to the active output of the virtual synchronous generator. Taking the reconstruction process of an energy storage system as an example, Fig. 9 As shown, the specific steps include:

[0169] 1) Measure the voltage of each battery pack in real time and map it with the open circuit voltage-state of charge (OCV-SOC) of the battery pack to obtain the initial SOC value;

[0170] 2) using the extended Kalman filter method (EKF method) to estimate the SOC value of the battery pack, and correcting the SOC value obtained in step 1) to achieve accurate estimation of the SOC value of each battery pack;

[0171] 3) Arrange the battery packs in descending order according to their SOC values;

[0172] 4) Turn on each battery pack in order from large to small according to the SOC value. Figure 8 As shown in the figure, the reconfigurable battery energy storage system is a structure of N battery groups in series. Due to the constant current discharge of energy storage, the output voltage is changed through the series circuit to meet the active output demand of the virtual synchronous generator. The battery group is controlled by a high-frequency power electronic switch and is sequentially incorporated into the discharge network from high SOC value to low SOC value.

[0173] 5) The active output demand of the virtual synchronous generator obtained in step 1-2) is used as the reconstruction constraint condition. The reconstruction constraint condition is as follows:

[0174]

[0175] Among them, P c is the active output demand of the virtual synchronous generator; P is the active power output of the inverter; δ is the corresponding safety threshold parameter; U bat ,I bat are the voltage and current output by the reconfigurable battery energy storage system respectively.

[0176] 6) If formula (18) is satisfied, the reconstruction is completed, otherwise go to step 4).

[0177] Embodiment 3:

[0178] A new type of reconfigurable energy storage distributed collaborative operation control method, the specific verification steps are as follows:

[0179] (1) The simulation time is set to 10s; the load is set to 70kW+30kvar, and another 70kW+30kvar load is connected after 5s; the expected discharge current is 20A; three reconfigurable new energy storage systems are set to operate in parallel, and each energy storage is set to have a structure of 8 battery packs in series; the voltage variation range of each battery pack is 434.7826V~581.9936V, and the voltage variation range corresponds to the state of charge SOC variation range of 5%~95%; the ratio of the rated active power of the three energy storages is P1:P2:P3=1:2:4.

[0180] (2) Establish an active power distribution unit, set the ratio of the active power-frequency droop coefficients of the three energy storages to 1:2:4, and observe whether the active power output of each energy storage is distributed according to 1:2:4.

[0181] (3) Establish a reactive power distribution unit, set the reactive power-voltage droop coefficient ratio of the three energy storages to 1:2:4, and observe whether the reactive power output of each energy storage is distributed according to 1:2:4.

[0182] (4) Establish a frequency recovery unit to observe whether the system frequency recovers to the rated frequency in a short time when the load changes for 5 seconds.

[0183] (5) According to the reconstruction strategy, observe whether the energy storage systems 1, 2, and 3 are discharged by one battery group, two battery groups, and four battery groups respectively within 0 to 5 seconds; when the load changes within 5 seconds, observe whether the energy storage systems 1, 2, and 3 are discharged by two battery groups, four battery groups, and eight battery groups respectively within 5 to 10 seconds.

[0184] (6) According to the above steps, it can be verified whether the reconfigurable new energy storage distributed collaborative operation model has the functions of power allocation and frequency recovery.

[0185] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A new type of reconfigurable distributed energy storage coordinated operation control method, the coordinated operation control method uses the inverter set on the DC side of the virtual synchronous generator to change the power output of the virtual synchronous generator, characterized in that: The control method is implemented by an active power distribution method and a reactive power distribution method, and the reactive power distribution method comprises the following steps: Step S1: When the line impedances of the virtual synchronous generators are inconsistent, an adaptive virtual impedance technology is introduced to perform secondary distribution of the reactive power output by the virtual synchronous generators; Step S2: Calculate the virtual impedance voltage drop in the dq coordinate system to obtain the voltage reference value after virtual impedance control. Step S3: Perform voltage and current dual closed-loop control based on the voltage reference value and output a PWM signal to the inverter.

2. A new type of reconfigurable energy storage distributed collaborative operation control method according to claim 1, characterized in that: The specific steps of the adaptive virtual impedance technology are as follows: Step S11: Obtain u according to the reactive power distribution consistency algorithm Qi : Among them, u Qi is the target voltage; c Q is the adjustment coefficient; e Qi It is the accumulated sum of reactive power deviation; m is the number of virtual synchronous generators; f(Q i ) is the objective function of the i-th virtual synchronous generator; f(Q j ) is the objective function of the jth virtual synchronous generator; l ij is the element in the Laplace matrix L of the i-th row and the j-th column, used to characterize the communication connection relationship between the virtual synchronous generators; Step S12: Reactive power distribution error is controlled by auxiliary control u Qi Feedback to a proportional-integral PI controller to obtain a virtual impedance correction term. The control equation of the proportional-integral PI controller is as follows: Where s is the Laplace operator; K pQ and K iQ are the proportional coefficient and integral coefficient of the PI controller respectively, δQ i is the virtual impedance correction value; Step S13: Obtain reactive power distribution information of adjacent virtual synchronous generators through a distributed communication network to update the local reactive power distribution error, and adaptively adjust its own virtual inductance and resistance according to formula (13): Among them, L vi and R vi They are adaptive virtual inductance and resistance through reactive power allocation error; and are static virtual inductance and resistance respectively, to ensure that the equivalent impedance is inductive; k QL and k QR They are used to adjust the proportional gains of virtual inductance and resistance respectively.

3. A new type of reconfigurable energy storage distributed collaborative operation control method according to claim 1, characterized in that: The calculation formula of virtual impedance voltage drop in dq coordinate system is as follows: Where, ω0 is the angular frequency of the inverter output; u vdi 、u vqi are the components of the voltage drop of the i-th virtual synchronous generator on the d and q axes respectively; I odi and I oqi are the components of the output current of the i-th virtual synchronous generator on the d and q axes respectively; The voltage reference value after the introduction of virtual impedance control is: in, and The d and q components of the voltage loop input reference value are: and The d and q components of the output voltage are controlled for Pf and QE respectively.

4. A new type of reconfigurable energy storage distributed coordinated operation control method according to claim 2, characterized in that: In step S11, the equation for power distribution consistency control of reactive power distribution is: in, is the state variable in the system; Y i and X i are the translation amounts of the Pf and QE droop characteristic curves of the i-th virtual synchronous generator; X j is the translation amount of the Pf droop characteristic curve of the jth virtual synchronous generator; k pi is the active power-frequency droop coefficient of the i-th virtual synchronous generator; k pj is the active power-frequency droop coefficient of the jth virtual synchronous generator; According to the continuous average consensus algorithm, if all virtual synchronous generators reach a consensus, then each variable can converge to its average value, that is:

5. A new type of reconfigurable energy storage distributed coordinated operation control method according to claim 2, characterized in that: When reactive power is distributed according to the rated capacity of energy storage, the output of each virtual synchronous generator meets the following conditions: Among them, Q i represents the reactive power output by the i-th virtual synchronous generator; Q iref represents the rated reactive power of the i-th virtual synchronous generator; Define the objective function f(Q i )=Q i / Q iref , and must meet the following requirements: Among them, k qi is the reactive power-voltage droop coefficient of the i-th virtual synchronous generator; Reference input x iref With the actual input x i The difference Δx i =x iref -(a2-b2x iref )x i , where x i and x iref Q i , Q iref function; a2 and b2 are selection coefficients, and their values ​​are determined by the output allocation objective function.

6. A new type of reconfigurable energy storage distributed coordinated operation control method according to claim 1, characterized in that: The active power distribution method comprises the following steps: Step T1: When the system allocates active power according to the rated capacity of energy storage, the output of each virtual synchronous generator must meet the following requirements: Among them, P i is the active power output by the i-th virtual synchronous generator; P iref is the rated active power of the i-th virtual synchronous generator; Define the objective function f(P i )=P i / P iref , and must meet the following requirements: Among them, k pi is the active power-frequency droop coefficient of the i-th virtual synchronous generator; Reference input y iref With the actual input y i The difference Δy i =y iref -(a1+b1y iref )y i , where y i and iref P i , P iref function; a1, b1 are selection coefficients, whose values ​​are determined by the output allocation objective function; Step T2: Design a frequency recovery unit based on Pf droop control, and its control equation is: Among them, J i is the virtual moment of inertia of the i-th virtual synchronous generator; ω0 is the system frontal frequency; is the angular frequency differential of the i-th virtual synchronous generator; ω i is the angular frequency measured for the i-th virtual synchronous generator; Y i is the translation amount of the Pf droop characteristic curve of the i-th virtual synchronous generator; Step T3: Adjacent virtual synchronous generators exchange their active power deviation information, determine the shift of the Pf droop curve, and modify the active power setting value to shift the droop curve upward from l1 to l2. The operating point becomes C, that is, the frequency is restored to f a , the frequency recovery unit is designed as: Among them, k i is the frequency recovery coefficient of the i-th virtual synchronous generator; k pj is the active power-frequency droop coefficient of the jth virtual synchronous generator; Y i * is the differential of the Pf droop characteristic curve shift of the i-th virtual synchronous generator; Y j are respectively the translation amounts of the Pf droop characteristic curve of the jth virtual synchronous generator.

7. A coordinated operation control system using a new type of reconfigurable energy storage distributed coordinated operation control method according to claims 1-6, characterized in that: It comprises a plurality of virtual synchronous generators connected in parallel, wherein the virtual synchronous generator comprises a control module, wherein the control module is connected to an inverter via a voltage-current dual closed-loop control module, and the voltage-current dual closed-loop control module is used to output a PWM signal to the inverter; The control module includes a reactive power distribution unit, which includes a PI control unit, an adaptive virtual impedance unit and a virtual voltage unit arranged in sequence from front to back. The input end of the PI control unit is connected to a consistency control unit, which is used to make the output of each virtual synchronous generator consistent; the PI control unit is used to control the reactive power distribution error through an auxiliary control u Qi The feedback processing obtains the virtual impedance correction term and sends it to the adaptive virtual impedance unit; the adaptive virtual impedance unit is used to redistribute the reactive power output by each virtual synchronous generator, and outputs it to the virtual voltage unit through the adaptive virtual inductance and resistance of the reactive power distribution error; the virtual voltage unit is used to calculate the virtual impedance voltage drop in the dq coordinate system through the inverter output current and angular frequency, and then control the dq component of the output voltage based on Pf and QE to output the dq component of the voltage loop input reference value.

8. The coordinated operation control system according to claim 7, characterized in that: The control module further includes an active power distribution unit, a frequency recovery unit and a Pf control unit which are arranged in sequence from front to back. The active power distribution unit is used to determine the objective function according to the operation requirements so as to flexibly distribute the power output; the frequency recovery unit is used to adjust the voltage frequency to restore it to the rated value; The frequency recovery unit is connected to a consistency control unit.

9. A new type of reconfigurable energy storage distributed cooperative operation control system according to claim 7, characterized in that: It also includes a reconfigurable battery energy storage system, wherein the virtual synchronous generator is connected to the reconfigurable battery energy storage system through a DC-DC conversion circuit, each virtual synchronous generator receives information from other virtual synchronous generators through at least one communication line to determine a communication connection Laplace matrix L, and the reconfigurable battery energy storage system performs constant current discharge control through an interconnected PI constant current discharge controller and a DC-DC conversion circuit.

10. A new type of reconfigurable energy storage distributed cooperative operation control system according to claim 9, characterized in that: The DC-DC conversion circuit includes an inductor L bat , resistor R bat , capacitor C, switch tube K1 and switch tube K2, and an inductor L connected in series is arranged between the reconfigurable battery energy storage system and the DC side of the inverter. bat , resistor R bat and switch tube K2, the resistor R bat A switch tube K1 is connected in parallel between the switch tube K1 and the switch tube K2, and a capacitor C is connected in parallel between the switch tube K2 and the DC side of the inverter; the PI constant current discharge controller is based on the output current I of the reconfigurable battery energy storage system bat and the expected discharge current The current difference generates a PWM modulation signal and acts on the switch tubes K1 and K2 to perform PI constant current discharge control.

11. A new type of reconfigurable energy storage distributed cooperative operation control system according to claim 9, characterized in that: Each reconfigurable new energy storage system is composed of N battery groups connected in series. The reconfigurable new energy storage system reconfigures the battery group according to the active output of the virtual synchronous generator, specifically including the following steps: Step D1: measuring the voltage of each battery pack in real time, and mapping it with the open circuit voltage-state of charge of the battery pack to obtain an initial SOC value; Step D2: using the extended Kalman filter method to correct the initial SOC value to achieve accurate estimation of the SOC value of each battery pack; Step D3: Sort the SOC values ​​of the battery packs from high to low, and use the active output demand of the virtual synchronous generator as a reconstruction constraint. Control the battery packs through high-frequency power electronic switches, and sequentially merge them into the discharge network from high SOC value to low SOC value until the active output demand of the virtual synchronous generator is met. The reconstruction constraint is as follows: P c ≤P≤(1+δ)P(18) And P=U bat .I bat , Among them, P c is the active power output demand of the virtual synchronous generator; P is the inverter output active power; δ is the corresponding safety threshold parameter; U bat ,I bat are the voltage and current output by the reconfigurable battery energy storage system respectively.

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