Energy storage system power management method and system for electric power system

Abstract

The invention discloses an energy storage system power management method for a power system. The method comprises the following steps: acquiring data information of a target power system and an energy storage system; modeling the target power system and the energy storage system; and constructing and solving a power management objective function of the energy storage system to complete power management of the energy storage system of the target power system. The invention also discloses a system for realizing the energy storage system power management method for the electric power system. According to the energy storage system power management method and system for the electric power system provided by the invention, through modeling and analysis of the electric power system and the energy storage system thereof, the objective function which simultaneously considers the voltage estimation value and the SOC value of the energy storage system is creatively proposed and solved; therefore, energy storage system power management for a power system can be realized, and the management process is rapid and efficient, high in reliability and good in accuracy.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to a power management method and system for an energy storage system of an electric power system. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring the stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] At this stage, environmental problems are becoming more and more serious, so more and more new energy power generation systems are beginning to be integrated into the power system and generate electricity. However, with the gradual increase in the penetration rate of new energy, the randomness of the output of new energy power generation systems has an increasing impact on the safe and reliable operation of the power system. The power system energy storage system can provide active and reactive support at the same time, and can quickly and accurately respond to the dispatching instructions of the power grid dispatching center, and has good frequency response characteristics. Therefore, the energy storage system has become an important part of the power system.

[0004] During operation, in addition to participating in peak shaving and valley filling and frequency stabilization of the power grid, the energy storage system can also directly supply power to nearby loads. In the existing control scheme, the power of the energy storage system is defined according to the load balancing method, while taking into account the charging power of the load. In the case of insufficient voltage, the power reference of all loads will be limited. At this time, the energy storage system will change its operating mode according to the QV reduction strategy to support the voltage. However, the existing control scheme does not take low voltage systems into account; this situation will affect the operating reliability of the energy storage system to a certain extent, thereby affecting the stable and reliable operation of the power system. Summary of the invention

[0005] One of the purposes of the present invention is to provide a power management method for an energy storage system of an electric power system with high reliability and good accuracy.

[0006] A second objective of the present invention is to provide a system for implementing the energy storage system power management method for the power system.

[0007] The energy storage system power management method for the power system provided by the present invention comprises the following steps:

[0008] S1. Obtain data information of the target power system and energy storage system;

[0009] S2. Modeling the target power system and energy storage system according to the data information obtained in step S1;

[0010] S3. Constructing a power management objective function of the energy storage system according to the modeling results obtained in step S2;

[0011] S4. Solve the objective function constructed in step S3 to complete the power management of the energy storage system of the target power system.

[0012] The step S2 of modeling the target power system and energy storage system according to the data information obtained in step S1 specifically includes the following steps:

[0013] The power system grid is connected to the AC bus; the AC bus is connected to the DC bus through a serially connected isolation transformer and AC / DC converter; the energy storage system is directly connected to the DC bus through an energy storage DC / DC converter; the DC load is connected to the DC bus through a load DC / DC converter;

[0014] DC bus voltage reference value and the actual value of the DC bus voltage v DC After making the difference, the active power reference value is obtained through PI control Active power reference value And the actual value of active power P in The difference between the reactive power and the reference value And the actual value of reactive power Q in The difference between the two values ​​is obtained by droop control, and the output voltage u of the AC / DC converter is obtained by droop control. inv ;

[0015] The voltage value of the common coupling point V PCC The reference charging current of the battery energy storage system is obtained by power management based on the state of charge value SOC of the energy storage system. Then the battery energy storage system voltage u is obtained through the current loop ess .

[0016] The step S3 constructs the power management objective function of the energy storage system according to the modeling result obtained in step S2, and specifically includes the following steps:

[0017] The following formula is used as the power management objective function of the energy storage system:

[0018]

[0019] Where J k is the objective function value; α is the first weight value, and α≥0; β is the second weight value, and β≥0; is the voltage reference value of the common coupling point; is the estimated voltage value of the common coupling point considering the charging power of the energy storage system, and V PCC,k is the voltage value of the common coupling point obtained at the kth measurement point, kpe is a constant related to active power and voltage amplitude, ΔP ESS,k is the power difference between adjacent sampling points, ΔP ESS,k =P ESS,k -P ESS,k-1 , P ESS,k is the power at sampling point k; SOC k+1 is the state of charge at sampling point k+1;

[0020] Step S4 of solving the objective function constructed in step S3 specifically includes the following steps:

[0021] Solve for J k About P ESS,k The gradient of , and set the gradient value to 0, to obtain the optimal solution of the power management objective function of the energy storage system;

[0022] Finally, the optimal solution of the power management objective function of the energy storage system is obtained for

[0023]

[0024] Where m is an intermediate variable, and η ch is the charge and discharge efficiency, Δt is the step length, E bat For battery energy.

[0025] The present invention also provides a system for implementing the energy storage system power management method for the electric power system, comprising a data acquisition module, a system modeling module, a target construction module and a power management module; the data acquisition module, the system modeling module, the target construction module and the power management module are connected in series in sequence; the data acquisition module is used to acquire data information of the target electric power system and the energy storage system, and upload the data information to the system modeling module; the system modeling module is used to model the target electric power system and the energy storage system according to the received data information and the acquired data information, and upload the data information to the target construction module; the target construction module is used to construct a power management objective function of the energy storage system according to the received data information and the obtained modeling results, and upload the data information to the power management module; the power management module is used to solve the constructed objective function according to the received data information to complete the power management of the energy storage system of the target electric power system.

[0026] The energy storage system power management method and system for the electric power system provided by the present invention, through modeling and analysis of the electric power system and its energy storage system, creatively proposes and solves an objective function that simultaneously considers the voltage estimation value and the SOC value of the energy storage system. Therefore, the present invention can not only realize the power management of the energy storage system for the electric power system, but also the management process is fast and efficient, with high reliability and good accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure is a schematic diagram of the method flow of the present invention.

[0028] Figure 2 Schematic diagram of the analysis curve of the values ​​of α and β in the embodiment of the method of the present invention.

[0029] Figure 3 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0030] like Figure 1 The method flow diagram of the method of the present invention is shown as follows: The power management method of the energy storage system for the power system disclosed in the present invention comprises the following steps:

[0031] S1. Obtain data information of the target power system and energy storage system;

[0032] S2. Modeling the target power system and energy storage system according to the data information obtained in step S1; specifically comprising the following steps:

[0033] The power system grid is connected to the AC bus; the AC bus is connected to the DC bus through a serially connected isolation transformer and AC / DC converter; the energy storage system is directly connected to the DC bus through an energy storage DC / DC converter; the DC load is connected to the DC bus through a load DC / DC converter;

[0034] DC bus voltage reference value and the actual value of the DC bus voltage v DC After making the difference, the active power reference value is obtained through PI control Active power reference value And the actual value of active power P in The difference between the reactive power and the reference value And the actual value of reactive power Q in The difference between the two values ​​is obtained by droop control, and the output voltage u of the AC / DC converter is obtained by droop control. inv ;

[0035] The voltage value of the common coupling point V PCC The reference charging current of the battery energy storage system is obtained by power management based on the state of charge value SOC of the energy storage system. Then the battery energy storage system voltage u is obtained through the current loop ess ;

[0036] S3. According to the modeling results obtained in step S2, a power management objective function of the energy storage system is constructed; specifically, the following steps are included:

[0037] The following formula is used as the power management objective function of the energy storage system:

[0038]

[0039] Where J k is the objective function value; α is the first weight value, and α≥0; β is the second weight value, and β≥0; is the voltage reference value of the common coupling point; is the estimated voltage value of the common coupling point considering the charging power of the energy storage system, and V PCC,k is the voltage value of the common coupling point obtained at the kth measurement point, k pe is a constant related to active power and voltage amplitude, ΔP ESS,k is the power difference between adjacent sampling points, ΔP ESS,k =P ESS,k -P ESS,k-1 , P ESS,k is the power at sampling point k; SOC k+1 is the state of charge at sampling point k+1;

[0040] The objective function value is minimized to achieve the smallest AC voltage error compared to the steady-state value while maximizing the energy storage of the energy storage system;

[0041] S4. Solving the objective function constructed in step S3 to complete the power management of the energy storage system of the target power system; specifically comprising the following steps:

[0042] From the objective function constructed in step S3 and the corresponding variable definition, we can see that the objective function receives the variable P ESS,k Therefore, according to the reference tracking target, there is an optimal value that can make the objective function value J k Minimum;

[0043] Therefore, solving for J k About P ESS,k The gradient of , and set the gradient value to 0, to obtain the optimal solution of the power management objective function of the energy storage system;

[0044] Finally, the optimal solution of the power management objective function of the energy storage system is obtained for

[0045]

[0046] Where m is an intermediate variable, and η ch is the charge and discharge efficiency, Δt is the step length, E bat For pool energy.

[0047] Optimal solution of the power management objective function through energy storage system From the expression, it can be seen that only simple mathematical operations are required to achieve the optimal control goal.

[0048] By analyzing , it can be known that k pe defines the grid characteristics of control perception. As the value of k pe increases, the grid impedance considered by the controller becomes weaker. Assuming α = 1, β = 0 and P ESS,k-1 = 0. It can be seen that assuming the same voltage deviation, a smaller value of k pe has a more obvious effect on the control effect. In addition, the k pe gain is closely related to the control performance. It can be seen that a lower value of k pe represents a fast control response because it indicates that the grid has rigid characteristics, thus requiring a higher power level to affect the PCC AC voltage. However, since the influence of k pe depends on the grid conditions, P ESS,k does not necessarily reflect the expected voltage compensation. In order to accurately estimate the voltage deviation caused by the power access of the energy storage system by the gain k pe , it is necessary to estimate the grid impedance.

[0049] Since k pe relates the power of the energy storage system to the corresponding AC voltage deviation, the estimated voltage change caused by the power of the energy storage system can be fully calculated by considering the grid impedance.

[0050] By simplifying the low-voltage grid dominated by resistance, the maximum change in the PCC voltage can be obtained based on the load nominal active power relationship, that is:

[0051]

[0052] In the formula, V grid is the grid voltage, R g is the grid resistance, is the input rated active power of loads such as fast charging piles;

[0053] From the maximum PCC voltage deviation of the load nominal power, the voltage compensation applied by the energy storage system can be estimated. Therefore, k pe can be obtained by replacing the predicted voltage compensation with is the voltage compensation applied by the energy storage system, is the rated charging power of the energy storage system.

[0054] Figure 2 Shows at SOC k= 80% and the power management behavior at different PCC voltage operating points to analyze the relationship between the gains α (a constant related to voltage regulation) and β (a constant related to energy storage system charging). In this case, a fixed gain k based on the previous design criteria is used according to the characteristics of the system under consideration. pe In addition, the proposed deterministic method relies on the relationship between α and β regardless of their absolute values. Therefore, in order to facilitate the analysis of the relationship between β / α, we consider setting α to 1 and setting β to vary from 0.1 to 10.

[0055] exist Figure 2 In (a), the behavior of the deterministic equation is highlighted by changing the relationship between β / α at three operating points. It can be noted that considering SOC k =80% energy storage system, for a fixed β / α ratio, under normal voltage conditions, the reference power of the energy storage system is about -10kw. It is clear that as β increases, the management center will give priority to the energy storage system to charge at a higher rate.

[0056] same, Figure 2 (b) Details of the changes in the three β cases over the entire voltage range are given. It can be seen that the lower the β / α ratio, the higher the priority of the energy storage system discharge behavior, thereby meeting the needs of voltage stability control. At the same time, as β / α increases, the curve moves to the left, and the energy storage system charging priority increases.

[0057] From the above analysis, it can be seen that considering that the goal of the power management strategy is to maintain a high energy storage system SOC while performing voltage stability control, the value of β / α can be fixed to 5. This ratio allows the energy storage system to have the highest charging rate under normal voltage, while still providing the energy storage system with the highest discharge power under insufficient voltage.

[0058] like Figure 3The figure shows a schematic diagram of the functional modules of the system of the present invention: the system disclosed in the present invention for implementing the power management method of the energy storage system for the power system comprises a data acquisition module, a system modeling module, a target construction module and a power management module; the data acquisition module, the system modeling module, the target construction module and the power management module are connected in series in sequence; the data acquisition module is used to acquire data information of the target power system and the energy storage system, and upload the data information to the system modeling module; the system modeling module is used to model the target power system and the energy storage system according to the received data information and the acquired data information, and upload the data information to the target construction module; the target construction module is used to construct a power management target function of the energy storage system according to the received data information and the obtained modeling results, and upload the data information to the power management module; the power management module is used to solve the constructed target function according to the received data information to complete the power management of the energy storage system of the target power system.

Claims

1. A method for managing power of an energy storage system for an electric power system, comprising the following steps: S1. Obtain data information of the target power system and energy storage system; S2. Modeling the target power system and energy storage system according to the data information obtained in step S1; S3. Constructing a power management objective function of the energy storage system according to the modeling results obtained in step S2; S4. Solve the objective function constructed in step S3 to complete the power management of the energy storage system of the target power system.

2. The energy storage system power management method for an electric power system according to claim 1, characterized in that The step S2 of modeling the target power system and energy storage system according to the data information obtained in step S1 specifically includes the following steps: The power system grid is connected to the AC bus; the AC bus is connected to the DC bus through a serially connected isolation transformer and AC / DC converter; the energy storage system is directly connected to the DC bus through an energy storage DC / DC converter; the DC load is connected to the DC bus through a load DC / DC converter; DC bus voltage reference value and the actual value of the DC bus voltage v DC After making the difference, the active power reference value is obtained through PI control Active power reference value And the actual value of active power P in The difference between the reactive power and the reference value And the actual value of reactive power Q in The difference between the two values ​​is obtained by droop control, and the output voltage u of the AC / DC converter is obtained by droop control. inv ; The voltage value of the common coupling point V PCC The reference charging current of the battery energy storage system is obtained by power management based on the state of charge value SOC of the energy storage system. Then the battery energy storage system voltage u is obtained through the current loop ess .

3. The energy storage system power management method for an electric power system according to claim 2, characterized in that The step S3 constructs the power management objective function of the energy storage system according to the modeling result obtained in step S2, and specifically includes the following steps: The following formula is used as the power management objective function of the energy storage system: Where J k is the objective function value; α is the first weight value, and α≥0; β is the second weight value, and β≥0; is the voltage reference value of the common coupling point; is the estimated voltage value of the common coupling point considering the charging power of the energy storage system, and V PCC,k is the voltage value of the common coupling point obtained at the kth measurement point, k pe is a constant related to active power and voltage amplitude, ΔP ESS,k is the power difference between adjacent sampling points, ΔP ESS,k =P ESS,k -P ESS,k-1 , P ESS,k is the power at sampling point k; SOC k+1 is the state of charge at sampling point k+1.

4. The energy storage system power management method for an electric power system according to claim 3, characterized in that Step S4 of solving the objective function constructed in step S3 specifically includes the following steps: Solve for J k About P ESS,k The gradient of , and set the gradient value to 0, to obtain the optimal solution of the power management objective function of the energy storage system; Finally, the optimal solution of the power management objective function of the energy storage system is obtained for Where m is an intermediate variable, and η ch is the charge and discharge efficiency, Δt is the step length, E bat For battery energy.

5. A system for implementing the power management method of energy storage system for power system according to any one of claims 1 to 4, characterized in that It includes a data acquisition module, a system modeling module, a target building module and a power management module; the data acquisition module, the system modeling module, the target building module and the power management module are connected in series in sequence; the data acquisition module is used to acquire data information of the target power system and the energy storage system, and upload the data information to the system modeling module; the system modeling module is used to model the target power system and the energy storage system according to the received data information and the acquired data information, and upload the data information to the target building module; The target construction module is used to construct the power management target function of the energy storage system according to the received data information and the obtained modeling results, and upload the data information to the power management module; The power management module is used to solve the constructed objective function according to the received data information to complete the power management of the energy storage system of the target power system.

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