A distributed collaborative control method based on heterogeneous battery energy storage system

Abstract

The present invention discloses a distributed collaborative control method based on a heterogeneous battery energy storage system, which relates to the technical field of collaborative control of heterogeneous battery energy storage systems, and includes the following steps: S1. A distributed controller obtains relevant information of neighboring batteries; S2. A primary controller in a distributed controller calculates control inputs to achieve sharing of active power and reactive power in a power grid and consistency of energy levels; S3. A secondary controller in a distributed controller calculates control inputs to achieve collaborative control of voltage and frequency; S4. A kinetic equation is used to update relevant information of the i-th battery; S5. Steps S1-S4 are repeated until the task cycle ends. The present invention can achieve sharing of reactive power and active power of batteries in a heterogeneous battery energy storage system, consistency of battery energy levels, and coordination of battery voltage and frequency within a fixed time.

Description

Technical Field

[0001] The present invention relates to the technical field of coordinated control of heterogeneous battery energy storage systems, and in particular to a distributed coordinated control method based on heterogeneous battery energy storage systems. Background Art

[0002] The cooperative control technology of battery energy storage systems has received extensive attention in recent years due to its key role in improving battery life and power quality. The main control objectives of this technology include achieving active and reactive power sharing between battery groups, consistent energy levels, and coordinated control of voltage and frequency. As the scale of battery energy storage systems continues to expand, traditional centralized cooperative control methods require increasingly high communication overhead and have a fatal single-point failure problem of the central unit. Distributed control is gradually becoming the mainstream solution for the design of cooperative control algorithms for battery energy storage systems because it only requires each battery to share its battery status with its neighbors.

[0003] Heterogeneous battery energy storage system refers to an energy storage system composed of batteries with different characteristics. There are two main reasons for studying it: (1) In actual power systems, it is very difficult to design batteries with exactly the same structure; (2) Batteries with different characteristics can achieve complementary characteristics and thus improve economic benefits. However, most previous studies only focus on battery systems with the same properties, which greatly limits the application of these control strategies. In the paper "A Consensus Approach to Real-Time Distributed Control of Energy Storage Systems in Wind Farms, IEEE Transactions on Smart Grid, vol. 10, no. 1", Baros et al. studied a type of coordination problem of heterogeneous battery energy storage systems in a droop control microgrid, realizing active and reactive power sharing and coordinated control of voltage and frequency. In addition, in the paper "Multi-Agent Consensus Design for Heterogeneous Energy Storage Devices With Droop Control in Smart Grids, IEEE Transactions on Smart Grid, vol. 10, no. 2", Khazaei et al. proposed more droop control microgrid structures to improve the control response speed. In addition, from the perspective of safety protection, the document "Control of Heterogeneous Battery Energy Storage Systems-Based Microgrid Connected via Detail-Balanced Communication Topology, IEEE Control Systems Letters, vol. 7" provides a new control scheme for directed connected microgrid systems to achieve the coordination of battery energy levels and frequencies of heterogeneous battery energy storage systems. However, the convergence of the control strategy in the above document has not been strictly proved, and the controller cannot achieve reactive power sharing and voltage consistency control.

[0004] Convergence speed is an important indicator for evaluating the performance of control algorithms. However, in the existing consensus controller designs for heterogeneous cooperative battery energy storage systems, some controllers can only achieve asymptotic convergence, which means that the heterogeneous battery energy storage system cannot reach a cooperative state within a limited time. In order to solve this problem, control algorithms with finite-time convergence are further proposed in the prior art, such as "Distributed Finite-Time Consensus Control for Heterogeneous Battery Energy Storage Systems in Droop-Controlled Microgrids, IEEE Transactions on Smart Grid, vol. 10, no. 5". However, the upper bound of the convergence time of these control algorithms directly depends on the initial state information of the battery system, and the above-mentioned literature cannot even give an explicit expression for achieving energy level coordination. Therefore, in heterogeneous battery energy storage systems where it is difficult to obtain the initial state information of all batteries, such control algorithms are no longer applicable. Summary of the invention

[0005] The purpose of the present invention is to provide a distributed collaborative control method based on a heterogeneous battery energy storage system, which solves the problem that in the existing heterogeneous battery energy storage system, there is no control algorithm that can solve the active and reactive power sharing, energy level consistency and frequency and voltage collaborative control of the battery system within a limited time.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A distributed collaborative control method based on a heterogeneous battery energy storage system, wherein the topological hierarchical structure of the heterogeneous battery energy storage system includes a battery, an internal voltage / current controller for converting the calculation result of a distributed controller into the actual state of the battery, a droop controller and a distributed controller, wherein the distributed controller obtains neighbor battery information, combines reference voltage and frequency, calculates and outputs active power, reactive power, nominal voltage, nominal frequency and other parameters, and then controls various states of the battery through the droop controller and the internal voltage / current controller. The control method of the system includes the following steps:

[0008] S1. Distributed controller obtains the reactive power Q of neighbor batteries i , Active power P i , energy level E i , nominal voltage and nominal frequency information;

[0009] S2. The primary controller in the distributed controller calculates the control input for active power sharing. For reactive power sharing To achieve consistent energy levels

[0010] S3. The control input is calculated by the secondary controller in the distributed controller to achieve voltage coordination. For frequency coordination

[0011] S4. Update the reactive power Q of the i-th battery using the kinetic equation i , Active power P i , energy level E i , nominal voltage Nominal frequency Information, battery frequencyω i And voltage information V i ;

[0012] S5. Repeat steps S1-S4 until the task cycle ends. The distributed controller will complete the reactive power Q of the battery system within T1. i , Active power P i The coordinated control of energy level E is completed within 2T1 i The coordinated control of the frequency ω is completed within T2 i and voltage V i collaborative control.

[0013] Preferably, in S2, the method for realizing active power sharing is For reactive power sharing To achieve consistent energy levels The calculation expression is:

[0014]

[0015]

[0016] In the formula, sign(~) is the sign function, a ij are the elements of the adjacency matrix corresponding to the topological graph of the heterogeneous battery energy storage system, c1,c 2, >0,0<α<1,β>1 are the control algorithm parameters to be selected, is the constant of the heterogeneous structure of each battery, i,j is the serial number of the battery in the microgrid system, P i is the active power of the ith battery, Q i is the reactive power of the ith battery, Ei is the energy level of the ith battery.

[0017] Preferably, in S3, the voltage coordination For frequency coordination The calculation expression is:

[0018]

[0019] In the formula, b i It is used to indicate whether the i-th battery in the heterogeneous battery energy storage system can directly receive the reference voltage and reference frequency. If so, b i =1, otherwise b i =0,ω i is the frequency of the ith battery, ω ref 、V ref are the reference frequency and reference voltage of the power grid respectively, is the nominal frequency of the ith battery, is the nominal voltage of the ith battery.

[0020] Preferably, in S4, the kinetic equation is:

[0021]

[0022]

[0023] In the formula, are the active power, reactive power, energy level, nominal frequency, and first-order derivative of the nominal voltage of the i-th battery, respectively.

[0024] Preferably, T1 satisfies the following relationship:

[0025]

[0026] Where G(~) is the Euler Gamma function, λ2 is the Federer eigenvalue of the communication topology graph corresponding to the heterogeneous battery energy storage system, and N is the number of batteries in the heterogeneous battery energy storage system.

[0027] Preferably, T2 satisfies the following relationship:

[0028]

[0029] In the formula, λ1 is a matrix The minimum eigenvalue of is the Laplace matrix of the communication topology of the heterogeneous battery energy storage system, Among them, if the i-th battery in the battery system can directly receive the reference voltage and reference frequency, then b i =1, otherwise b i =0.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention can realize the sharing of battery reactive power and active power in a heterogeneous battery energy storage system within a fixed time.

[0032] 2. The present invention can achieve consistency of battery energy levels in a heterogeneous battery energy storage system within a fixed time.

[0033] 3. The present invention can achieve coordination of battery voltage and frequency in a heterogeneous battery energy storage system within a fixed time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the hierarchical structure of the heterogeneous battery energy storage system of the present invention;

[0035] Figure 2 A schematic diagram of the communication topology structure of the IEEE-57 test system according to an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the coordinated control results of the heterogeneous battery energy storage system of the present invention;

[0037] Figure 4 The schematic diagram of the implementation result of the controller of the present invention in the STM32 microcontroller;

[0038] Figure 5 A schematic diagram showing the comparison of the convergence time of the reference voltage of the present invention and the prior art;

[0039] Figure 6 It is a schematic diagram comparing the convergence time of the reference frequency of the present invention and the prior art. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Figure 1The figure shows a heterogeneous battery energy storage system with an undirected, unweighted, connected communication topology. The hierarchical structure includes batteries, batteries connected to the power grid, an internal voltage / current controller for converting the calculation results of the distributed controller into the actual state of the battery, a droop controller and a distributed controller. The distributed controller obtains neighbor battery information, combines the reference voltage and frequency, calculates and outputs active power, reactive power, nominal voltage, nominal frequency and other parameters, and then controls the various states of the battery through the droop controller and the internal voltage / current controller. The droop controller is used to control its voltage and frequency through the nominal voltage and nominal frequency of the battery.

[0042] The present invention can achieve the following control objectives:

[0043] (1) Realize the sharing of battery reactive power and active power in heterogeneous battery energy storage systems:

[0044] Right now, in is the constant of the heterogeneous structure of each battery, i,j is the serial number of the battery in the microgrid system, P i is the active power of the ith battery, Q i is the reactive power of the ith battery.

[0045] (2) Achieve consistency in battery energy levels in heterogeneous battery energy storage systems:

[0046] Right now, in is a constant for each cell heterogeneous structure, and E i is the energy level of the ith battery.

[0047] (3) Realize the coordination of battery voltage and frequency in heterogeneous battery energy storage systems:

[0048] That is, V i =V j =V ref and ω i =ω j =ω ref , where V i is the voltage of the ith battery, ω i is the frequency of the ith battery, ω ref , V ref They are the reference frequency and reference voltage of the power grid respectively.

[0049] In order to achieve the above control objectives, the present invention proposes a distributed collaborative control method based on a heterogeneous battery energy storage system, comprising the following steps:

[0050] S1. Distributed controller obtains the reactive power Q of neighbor batteries i , Active power P i , energy level E i , nominal voltage and nominal frequency Information; input distributed controller parameters c1, c2, α, β, iteration step size Δτ, and iteration counter counter.

[0051] S2. The primary controller in the distributed controller calculates the control input for active power sharing. For reactive power sharing To achieve consistent energy levels

[0052]

[0053] In the formula, sign(~) is the sign function, a ij are the elements of the adjacency matrix corresponding to the topological graph of the heterogeneous battery energy storage system, c1,c2,>0,0<α<1,β>1 are the control algorithm parameters to be selected, is the constant of the heterogeneous structure of each battery, i,j is the serial number of the battery in the microgrid system, P i is the active power of the ith battery, Q i is the reactive power of the ith battery, E i is the energy level of the ith battery.

[0054] S3. The control input is calculated by the secondary controller in the distributed controller to achieve voltage coordination. For frequency coordination

[0055]

[0056] In the formula, b i It is used to indicate whether the i-th battery in the heterogeneous battery energy storage system can directly receive the reference voltage and reference frequency. If so, b i =1, otherwise b i =0,ω i is the frequency of the ith battery, ω ref 、V ref are the reference frequency and reference voltage of the power grid respectively, is the nominal frequency of the ith battery, is the nominal voltage of the ith battery.

[0057] S4. Update the reactive power Q of the i-th battery using the kinetic equation i , Active power P i , energy level E i , nominal voltage Nominal frequency Information, battery frequencyω i And voltage information V i ;

[0058] The kinetic equation is:

[0059]

[0060] In the formula, are the first-order derivatives of the active power, reactive power, energy level, nominal frequency, and nominal voltage of the ith battery, respectively. is the constant of the heterogeneous structure of each battery, i,j is the serial number of the battery in the microgrid system, P i is the active power of the ith battery, Q i is the reactive power of the ith battery, E i is the energy level of the ith battery, is the nominal frequency of the ith battery, is the nominal voltage of the ith battery, ω i is the frequency of the ith battery, V i is the voltage of the ith battery, is the control input for active power sharing, is the control input for reactive power sharing, is the control input used to achieve consistent energy levels, is the control input for voltage coordination, is the control input used to achieve frequency coordination.

[0061] S5. Repeat steps S1-S4 until the task cycle ends, and the distributed controller completes the reactive power Q of the battery system within T1. i , Active power P i The coordinated control of energy level E is completed within 2T1 i The coordinated control of the frequency ω is completed within T2 i and voltage V i collaborative control.

[0062] T1 satisfies the following relationship:

[0063]

[0064] Where G(~) is the Euler Gamma function, λ2 is the Federer eigenvalue of the communication topology graph corresponding to the heterogeneous battery energy storage system.

[0065] T2 satisfies the following relationship:

[0066]

[0067] In the formula, λ1 is a matrix The minimum eigenvalue of is the Laplace matrix of the communication topology of the heterogeneous battery energy storage system, Among them, if the i-th battery in the battery system can directly receive the reference voltage and reference frequency, then b i =1, otherwise b i =0.

[0068] Figure 2 The figure shows the communication topology of the IEEE-57 test system, which includes seven heterogeneous batteries and a virtual leader, that is, only battery 2 can directly receive the reference voltage and reference frequency. The parameters of the distributed controller are designed as c1=c2=1, α=1 / 3, β=3, and the specific grid parameters are set to K E =K P =[1.1,1.3,1.05,0.95,1.2,0.9,1.25],K Q [1.1,1.05,1.4,1.35,0.95,1.23,1.08], the initial state of the power grid is set as follows:

[0069] P(0)=[1.2,1.4,1.6,1.8,2.0,2.2,2.4]pu;

[0070] Q(0)=[0.7,0.9,1.1,1.3,1.5,1.7,1.9]pu;

[0071] E(0)=[1.3,1.6,1.2,1.7,1.8,2.4,2.5]pu;

[0072] V(0)=[1.8,2.0,2.2,2.4,2.6,2.8,3.0]pu;

[0073] ω(0)=[2.3,2.5,2.7,2.9,3.1,3.3,3.5]pu;

[0074] The experimental results are as follows Figure 3As shown, at t=10s, a load change of -1.4+1.6jp.u is applied to the entire power grid. It can be seen that the controller achieves each control target within 5s, which verifies the effectiveness of the present invention. At the same time, in order to illustrate that the controller of the present invention has good hardware realizability, the present invention runs the code shown in Table 1 on the STM32ZET6F103 single-chip microcomputer:

[0075] Table 1 Fixed time distributed controller calculation code

[0076]

[0077]

[0078] The status results of the first and seventh batteries are as follows Figure 4 As shown in the figure. The grid parameters and controller parameters are the same as those in the simulation experiment, and the iteration step is set to 0.01. It can be seen that after 500 iterations, all batteries have achieved the sharing of reactive power and active power, the consistency of energy level, and the coordination of voltage and frequency.

[0079] like Figure 5-Figure 6 As shown, the controller of the present invention is compared with the asymptotically convergent controller and the finite time controller in the prior art. The constant gain and exponential term of all controllers are kept consistent. The grid controller parameters remain unchanged, and the initial state of the grid is reset to:

[0080] P(0)=[0.5,1.5,2.6,3.8,5.0,6.2,7.4]pu;

[0081] Q(0)=[0.7,1.9,2.1,3.3,4.5,5.7,6.9]pu;

[0082] E(0)=[1.3,1.6,1.2,1.7,1.8,2.4,2.5]pu;

[0083] V(0)=[1.8,3.0,4.2,5.4,6.6,7.8,9.0]pu;

[0084] ω(0)=[0.9,2.1,3.3,4.5,5.7,6.9,8.1]pu;

[0085] The residuals of the frequency and voltage of all batteries and the reference values ​​are selected as observation quantities. It can be seen that the controller in the present invention has a faster convergence speed, which means that the control objectives (1)-(3) will be achieved in a shorter time, thus verifying the excellent characteristic of the present invention that it can converge quickly within a fixed time.

Claims

1. A distributed collaborative control method based on a heterogeneous battery energy storage system, characterized in that: The following steps are involved: S1. Distributed controller obtains reactive power of neighbor batteries , Active Power , energy level , nominal voltage and nominal frequency ; S2. The primary controller in the distributed controller calculates the control input for active power sharing. , used to achieve reactive power sharing , used to achieve consistent energy levels , the calculation expression is: (Formula 9); (Formula 10); (Formula 11); In the formula, is the symbolic function, is the element of the adjacency matrix corresponding to the topological graph of the heterogeneous battery energy storage system, are the control algorithm parameters to be selected, , is the constant for the heterogeneous structure of each cell, is the serial number of the battery in the microgrid system, For the The active power of each battery, For the The reactive power of a battery, For the The energy level of each battery; S3. The control input is calculated by the secondary controller in the distributed controller to achieve voltage coordination. , used to achieve frequency coordination , the calculation expression is: (Formula 12); (Formula 13); In the formula, , Used to represent the first Can the battery directly receive the reference voltage and reference frequency? If so, ,on the contrary , For the The frequency of the battery, , are the reference frequency and reference voltage of the power grid respectively, For the The nominal frequency of each battery, For the Nominal voltage of the battery; S4. Update the first Reactive power of batteries , Active Power , energy level , nominal voltage , nominal frequency , the frequency of the battery and voltage information ; S5. Repeat steps S1-S4 until the task cycle ends, and the distributed controller will The reactive power of the battery system is completed , Active Power The collaborative control of Internal energy level collaborative control and Complete frequency and voltage collaborative control; Said The following relations are satisfied: (Formula 14); In the formula, is the Euler Gamma function, , is the Federer eigenvalue of the communication topology graph corresponding to the heterogeneous battery energy storage system, and N is the number of batteries in the heterogeneous battery energy storage system; Said The following relations are satisfied: (Formula 15); In the formula, , For the matrix The minimum eigenvalue of is the Laplace matrix of the communication topology of the heterogeneous battery energy storage system, , where if the battery system A battery is able to directly receive the reference voltage and reference frequency, then ,on the contrary .

2. A distributed collaborative control method based on a heterogeneous battery energy storage system according to claim 1, characterized in that: In S4, the kinetic equation is: (Formula 1); (Formula 2); (Formula 3); , (Formula 4); , (Formula 6); (Formula 7); (Formula 8); In the formula, , , , , Respectively Active power, reactive power, energy level, nominal frequency, and first-order derivative of nominal voltage of each battery.

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