A consistency control method and control system of multiple energy storage systems

Abstract

The present invention proposes a consistency control method and a control system for multiple energy storage systems. Aiming at the nonlinear characteristics of dead zones in energy storage systems, the present invention proposes a consistency control method based on distributed robustness. By combining backstepping with graph theory, a distributed controller is recursively designed for each energy storage system to synchronize the outputs of adjacent systems while keeping the entire system bounded. It is proved that when an undirected graph is connected, the outputs of all energy storage systems are controllable, that is, consistency control of multiple energy storage systems is achieved. The present invention does not require prior knowledge of unknown system parameters and dead zone characteristics, and has good applicability.

Description

Technical Field

[0001] The present invention relates to a consistency control method and system for a multi-energy storage system, and belongs to the cross-field of electrical and control system design. Background Art

[0002] Since the beginning of the 21st century, the consistency control of multiple systems has attracted widespread attention in the control community. Early research in this field focused on control objects with linear systems. However, in practice, the system has uncertainty and may be disturbed. In this case, synchronization of the entire system is sometimes unnecessary and impossible. In recent years, with the widespread application of energy storage systems represented by batteries and capacitors, consistency control between energy storage systems has become a research hotspot. Since the input and output of energy storage systems have nonlinear characteristics, the output synchronization problem of nonlinear multi-systems has attracted widespread attention from researchers.

[0003] In the past few decades, various controllers have been proposed for the stabilization or asymptotic tracking of single nonlinear systems. On this basis, researchers have studied the consistency control of multiple strict feedback systems, where the unknown parameters of the system are estimated by state updaters and the uncertain control direction is considered in the dynamic changes of multiple systems. The performance is improved by adding Nussbaum functions to the controller and adding nonlinear damping parts. However, due to the dead zone characteristics of the input of some systems, there are control difficulties in the controllability of the output of multiple systems. Summary of the invention

[0004] The present invention extends the single system tracking method with dead zone nonlinearity to a multi-interaction system, and provides a consistency control method and control system for a multi-energy storage system that takes into account the system dead zone and does not require understanding of the system nonlinear characteristics.

[0005] In order to achieve the above object, the specific technical solution of the present invention is as follows:

[0006] A consistency control method for a multi-energy storage system, wherein each energy storage system in the multi-energy storage system is a nonlinear energy storage system with a dead zone characteristic, and a mathematical model is expressed as:

[0007]

[0008] y i =x i1

[0009] Wherein, i=1,2…,N is the number of energy storage systems in the multi-energy storage system, and n is the number of state quantities obtained by each energy storage system. is the system state quantity, is the corresponding derivative, is the output of the nonlinear energy storage system, b i >0 is high frequency gain, is a set of smooth and bounded functions describing the state quantities of the system, where d i (t) is a bounded external disturbance, is the unknown parameter vector, Represents a control input with a nonlinear characteristic with deadband.

[0010] The consistency control method comprises the following steps:

[0011] (1) Obtain the state quantity of each energy storage system at the current moment

[0012] (2) Calculate the control input of each energy storage system based on the acquired state quantity

[0013]

[0014] Among them, b ir ≥0, b il ≤0,m i >0 are three constants, For the above input, is a dummy control variable, expressed as follows:

[0015]

[0016] where a ij Represents the elements in the weighted adjacency matrix A of the multi-energy storage system, a1,…,a n >1 is the control gain, represents the set of energy storage systems adjacent to energy storage system i, Yes i =1 / β i The estimate of β i =b i m i >0,b i is the high frequency gain of the system, It is the border The estimated update rate is:

[0017]

[0018]

[0019] γ,η>0 is the system control gain constant, ξ i1 ,...,ξ in is the output error between energy storage system i and adjacent energy storage system j, which can be solved by the following method:

[0020]

[0021] and They represent θ i Dynamic adaptive update parameters and its neighborhood θ j Dynamic update parameters, the update rate is as follows:

[0022]

[0023]

[0024] γ1,γ2 are two tuning gains.

[0025] The intermediate function f i1 ,…,f in , Calculated by the following formula:

[0026] f i1 =0

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035] Where m=3,…,n.

[0036] (3) According to the control input Combined with the mathematical model of the system, the control target of each state quantity of each energy storage system is obtained. According to the control target of each state quantity, the state quantity of each energy storage system is controlled to make the output of each energy storage system consistent.

[0037] Furthermore, the system state quantity includes: voltage, current, etc.

[0038] A consistency control system applied to a multi-energy storage system comprises one or more processors for executing any of the above-mentioned consistency control methods for the multi-energy storage system.

[0039] The beneficial effects of the present invention are:

[0040] The method and system of the present invention can be used for consistency control of nonlinear multi-energy storage systems. It is not necessary to have prior knowledge of the parameters and dead zone characteristics of unknown systems, and can achieve consistency control of the outputs of multiple systems, ensuring that the output of each system is controllable, thereby improving the applicability of the control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a series capacitor model diagram.

[0042] Figure 2 It is the capacitor voltage output waveform.

[0043] Figure 3 is the unknown parameter θ i Estimates 's change graph.

[0044] Figure 4 is 1 / β i Estimated change graph.

[0045] Figure 5 It is an uncertainty estimate of the boundaries of a dynamic system. DETAILED DESCRIPTION

[0046] The present invention proposes a consistency control method applied to multiple energy storage systems. The method introduces graph theory methods and considers the coordination of multiple systems, thereby realizing consistency control of multiple energy storage input systems with dead zone characteristics without knowing the nonlinear characteristics of the system input.

[0047] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings:

[0048] Each energy storage system in the multi-energy storage system is a nonlinear energy storage system with dead zone characteristics. Considering the characteristics of the nonlinear multi-system, the multi-energy storage system is firstly mathematically modeled, as shown below:

[0049]

[0050] y i =x i1

[0051] Wherein, i=1,2…,N is the number of energy storage systems in the multi-energy storage system, and n is the number of state quantities obtained by each energy storage system. is the system state quantity, which can be voltage, current, etc. is the corresponding derivative, is the output of the nonlinear energy storage system, bi >0 is high frequency gain, d i (t) is a bounded external disturbance, is the unknown parameter vector, is a set of smooth and bounded functions describing the state quantities of the system, where The control input represents the input with dead zone nonlinear characteristics, which can be specifically expressed as:

[0052]

[0053] Among them, v i is the input of the above formula, b ir ≥0, b il ≤0,m i >0 are three constants.

[0054] For the established nonlinear multi-energy storage system, its control objective is to design appropriate input Make the output of each system stable and controllable. and They represent θ i Dynamic adaptive update parameters and its neighborhood θ j Dynamic update parameters. It is the border An estimate of x i Indicates the state of the energy storage system i itself, Status information of the energy storage systems adjacent to energy storage system i.

[0055] For a system consisting of N energy storage systems, a consistency controller is set for each individual energy storage system i, such as the following form:

[0056]

[0057] where sgn is the sign function, represents the set of energy storage systems adjacent to energy storage system i, Yes i =1 / β i The estimate of β i =b i m i >0,b i is the high frequency gain of the system, It is the border The estimate of , the update rate (corresponding derivative) is as follows:

[0058]

[0059]

[0060] γ,η>0 is the system control gain constant, is a dummy control variable, and the parameter update formula is as follows:

[0061]

[0062] yes The derivative of yes The derivative of .

[0063] a ij Representing the weighted adjacency matrix of multiple energy storage systems The elements in represent the adjacency relationship between energy storage system i and energy storage system j.

[0064] where f i1 ,…,f in , is an intermediate function, calculated by the following formula:

[0065]

[0066]

[0067]

[0068] where m = 3,…,n; a1,…,a n >1 is the control gain, γ1 and γ2 are two tuning gains.

[0069] Therefore, by obtaining the state quantity of each energy storage system at the current moment in real time The control input of each energy storage system is calculated using the consistency controller based on the acquired state quantity Finally, the control input quantity is substituted into the mathematical model of the system to obtain a new state quantity, which is the control target of each state quantity of each energy storage system. According to the control target of each state quantity, the state quantity of each energy storage system is controlled to make the output of each energy storage system consistent in the multi-energy storage system.

[0070] Furthermore, for the first energy storage system, the initial step is defined as follows:

[0071]

[0072] Where X1 = [x 11 ,…,x N1 ] T , L is the Laplace matrix of the system undirected graph, since L = L T ≥0, the derivative of W1 with respect to time can be obtained as

[0073]

[0074] in is the output error between energy storage system i and adjacent energy storage system j; definition The above formula can be rewritten as:

[0075]

[0076] The energy function is defined as

[0077]

[0078] in Taking its derivative, we get:

[0079]

[0080] For the second energy storage system,

[0081]

[0082] in, is a known quantity, and the unknown parameters only exist in θ i Among them. and Substituting into the above formula, we have

[0083]

[0084] in definition

[0085]

[0086] Can be launched

[0087]

[0088] For the mth (3≤m≤n) energy storage system,

[0089]

[0090] definition

[0091]

[0092] in V m Derivative with respect to time for

[0093]

[0094] For the Nth energy storage system, similarly, we can get

[0095]

[0096] Prove that when t→∞ The proof process is as follows: Since V ≥ 0, Therefore the variable is bounded, is uniformly continuous and satisfies that when t→∞, Considering ξ1=[ξ 11 ,…,ξ N1 ] T =LX1, Null(L)=span{1 N}, so when t→∞, X1(t)=[x 11 (t),…,x N1 (t)] T ∈span{1 N}, thus completing the proof: the control method of the present invention can ensure that the output of each system is controllable and the estimated parameters are bounded.

[0097] Furthermore, a specific embodiment is provided, in which the method is applied to the voltage control of a multi-energy storage system composed of supercapacitors. Figure 1 As shown in the figure, four capacitors are connected in series. Due to the characteristics of electronic components, the input of each supercapacitor has a dead zone nonlinear characteristic. The output consistency problem of supercapacitors is solved by comprehensive distributed adaptive control.

[0098] For each supercapacitor, its voltage is collected as the state quantity of the system, and a model as shown in (1) is constructed. Due to the electronic characteristics of the component, the input of the capacitor has dead zone nonlinearity, and its control input is set as follows:

[0099]

[0100] Given parameter m i =1,b ir =0.7,b il=-0.7. The initial values ​​of the four supercapacitors are designed as: x1(0)=2, x2(0)=1.5, x3(0)=2.7, x4(0)=1.7. Establish a controller in the form of (3)~(4), set the control gain to γ1=1; a1=5; γ=2; η=3, the system parameters are: θ1=1.2; θ2=1.5; θ3=0.8; θ4=2, and the initial values ​​of the remaining parameters of the update rate are all set to 0. According to the model combined with the output of the controller, the control targets x1(t), x2(t), x3(t), x4(t) of each state quantity of each supercapacitor are finally obtained, and the state quantity of each supercapacitor is controlled to make the output of each supercapacitor consistent. In this embodiment, the output is the voltage of the supercapacitor.

[0101] The simulation results are as follows Figures 2 to 5 shown. Figure 2 This indicates that the voltage of the supercapacitor eventually stabilizes at the same value. Figure 3 , 4 are the unknown parameters θ i Estimates and 1 / β i Estimates As you can see, both outputs eventually remain bounded and stable. Figure 5 Shows the unknown parameters The border The estimate of , which turns out to be bounded.

[0102] Corresponding to the aforementioned embodiment of a consistency control method for multiple energy storage systems, the present invention also provides an embodiment of a consistency control system applied to multiple energy storage systems.

[0103] An embodiment of the present invention provides a consistency control system applied to a multi-energy storage system, including one or more processors for implementing the consistency control method of the multi-energy storage system in the above embodiment.

[0104] An embodiment of the consistency control system applied to a multi-energy storage system of the present invention can be applied to any device with data processing capability, and the any device with data processing capability can be a device or apparatus such as a computer.

[0105] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A consistency control method applied to a multi-energy storage system, characterized in that: Each energy storage system in the multi-energy storage system is a nonlinear energy storage system with dead zone characteristics, and the mathematical model is expressed as: and i =x i1 Wherein, i = 1, 2…, N is the number of energy storage systems in the multi-energy storage system, and n is the number of state quantities obtained by each energy storage system; is the system state quantity, is the corresponding derivative, is the output of the nonlinear energy storage system, b i >0 is high frequency gain, is a set of smooth and bounded functions describing the state quantities of the system, where k=1,…,n;d i (t) is a bounded external disturbance, is the unknown parameter vector, A control input representing an input with a nonlinear characteristic with a dead zone; The consistency control method comprises the following steps: (1) Obtain the state quantity of each energy storage system at the current moment (2) Calculate the control input of each energy storage system based on the acquired state quantity Among them, b ir ≥0, b il ≤0,m i >0 are three constants, For the above input, is a dummy control variable, expressed as follows: where a ij Represents the elements in the weighted adjacency matrix of the multi-energy storage system, a1,…,a n >1 is the control gain, represents the set of energy storage systems adjacent to energy storage system i, Yes i =1 / β i The estimate of β i =b i m i >0,b i is the high frequency gain of the system, It is the border The estimated update rate is: γ,η>0 is the system control gain constant, ξ i1 ,...,ξ in is the output error between energy storage system i and adjacent energy storage system j, which can be solved by the following method: and They represent θ i Dynamic adaptive update parameters and its neighborhood θ j Dynamic update parameters, the update rate is as follows: γ1,γ2 are two tuning gains; The intermediate function f i1 ,…,f in , Calculated by the following formula: f i1 ＝0 Where m = 3,…,n; (3) According to the control input Combined with the mathematical model of the system, the control target of each state quantity of each energy storage system is obtained. According to the control target of each state quantity, the state quantity of each energy storage system is controlled to make the output of each energy storage system consistent.

2. The method according to claim 1, characterized in that: The system state quantity includes: voltage and current.

3. A consistency control system applied to a multi-energy storage system, characterized in that: It includes one or more processors for executing the consistency control method of the multi-energy storage system described in any one of claims 1-2.

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