Energy storage system power management method and system for power systems

Abstract

The application discloses a power management method for an energy storage system of a power system, comprising 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; constructing a power management objective function of the energy storage system and solving the power management objective function, so as to complete power management of the energy storage system of the target power system. The application further discloses a system for implementing the power management method for the energy storage system of the power system. The power management method and system for the energy storage system of the power system provided by the application can model and analyze the power system and the energy storage system thereof, creatively propose an objective function considering voltage estimation values and SOC values of the energy storage system and solve the objective function, so that the application can not only realize power management of the energy storage system of the power system, but also has the advantages of fast and efficient management process, high reliability and good accuracy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrical automation, and particularly relates to a power management method and system for an energy storage system of a power system. BACKGROUND

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

[0003] At present, environmental problems are becoming more and more serious, so more and more new energy power generation systems begin to be integrated into the power system and generate electricity. However, with the gradual increase of new energy penetration rate, the randomness of the output of the new energy power generation system has a greater and greater impact on the safe and reliable operation of the power system. The energy storage system of the power 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 modulation response characteristics. Therefore, the energy storage system has become an important part of the power system.

[0004] In the operation process, in addition to participating in the peak load shifting and frequency stabilization of the power grid, the energy storage system can also directly power the nearby load. In the existing control scheme, the power of the energy storage system is defined according to the load balancing method, and the charging power of the load is also considered. In the case of voltage deficiency, the power reference of all loads will be limited. At this time, the energy storage system will change its working mode according to the Q-V drop strategy to support the voltage. However, the existing control scheme does not consider the low-voltage system; this situation will affect the operation reliability of the energy storage system, thereby affecting the stable and reliable operation of the power system. SUMMARY

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

[0006] The second purpose of the present application is to provide a system for implementing the power management method for the energy storage system of the power system.

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

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

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

[0010] S3. Based on the modeling results obtained in step S2, construct the power management objective function of the energy storage system;

[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] Step S2, which involves modeling the target power system and energy storage system based on the data obtained in step S1, specifically includes the following steps:

[0013] The power grid is connected to the AC bus; the AC bus is connected to the DC bus through a series-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 DC bus voltage v DC After the difference is calculated, 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, and the reactive power reference value. and the actual value of reactive power Q in The difference is used to obtain the output voltage u of the AC / DC converter after droop control. inv ;

[0015] Voltage value V at the common coupling point PCC The reference charging current of the battery energy storage system is obtained by power management after the state of charge (SOC) of the energy storage system is processed. The battery energy storage system voltage u is then obtained through a current loop. ess .

[0016] Step S3, which involves constructing the power management objective function of the energy storage system based on the modeling results obtained in step S2, specifically includes the following steps:

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

[0018]

[0019] In the formula J k Let be the objective function value; α be the first weight value, and α≥0; β be the second weight value, and β≥0; This is the voltage reference value at the common coupling point; The estimated common-coupled point voltage value considering the impact of the energy storage system's charging power, and V PCC,k Let k be the common coupling point voltage value obtained at the k-th measurement point.pe ΔP is a constant related to active power and voltage amplitude. ESS,k ΔP represents the power difference between adjacent sampling points. ESS,k =P ESS,k -P ESS,k-1 P ESS,k The power at sampling point k; SOC k+1 The state of charge at sampling point k+1;

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

[0021] Solve for J k Regarding P ESS,k The gradient of the energy storage system is calculated, and the gradient value is set 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] In the formula, m is an intermediate variable, and η ch The charge / discharge efficiency is given by E, where Δt is the step size. bat It provides energy for the battery.

[0025] This invention also provides a system for implementing the power management method for an energy storage system in a power system, comprising a data acquisition module, a system modeling module, a target construction module, and a power management module; the data acquisition module, system modeling module, target construction module, and power management module are connected in series; the data acquisition module acquires data information of the target power system and the energy storage system and uploads the data information to the system modeling module; the system modeling module models the target power system and the energy storage system based on the received data information and the acquired data information, and uploads the data information to the target construction module; the target construction module constructs a power management objective function for the energy storage system based on the received data information and the obtained modeling results, and uploads the data information to the power management module; the power management module solves the constructed objective function based on the received data information to complete the power management of the energy storage system in the target power system.

[0026] The present invention provides a power management method and system for energy storage systems in power systems. By modeling and analyzing the power system and its energy storage system, it creatively proposes and solves an objective function that simultaneously considers the voltage estimate and the SOC value of the energy storage system. Therefore, the present invention can not only realize power management of energy storage systems in power systems, but also achieve fast, efficient, reliable and accurate management process. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A schematic diagram of a method flow of the method of the application.

[0028] Figure 2 A schematic diagram of a value analysis curve of a and β of an embodiment of the method of the application.

[0029] Figure 3 A schematic diagram of a functional module of the system of the application. DETAILED DESCRIPTION

[0030] As Figure 1 shown is a schematic diagram of a method flow of the method of the application: the energy storage system power management method for a power system disclosed by the application comprises the following steps:

[0031] S1. obtaining data information of a target power system and an energy storage system;

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

[0033] The power system is connected to an AC bus through a grid; the AC bus is connected to a DC bus through a series-connected isolation transformer and an 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] a DC bus voltage reference value and a DC bus voltage actual value v DC After the difference is obtained, the active power reference value is obtained through PI control; the difference between the active power reference value in and the active power actual value P in , and the difference between the reactive power reference value and the reactive power actual value Q inv , through droop control, to obtain the output voltage u inv of the AC / DC converter;

[0035] The voltage value V PCC of the common coupling point and the state of charge value SOC of the energy storage system are obtained through power management to obtain the battery energy storage system reference charging current The battery energy storage system voltage u ess is obtained through the current loop;

[0036] S3. constructing a power management objective function of the energy storage system according to the modeling result obtained in step S2; specifically comprising the following steps:

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

[0038]

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

[0040] The objective function value is minimized to achieve the minimum AC voltage error compared with 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 including the following steps:

[0042] As can be seen from the objective function constructed in step S3 and the corresponding variable definition, the objective function is controlled by the variable P ESS,k , therefore, according to the reference tracking target, there is an optimal value that can minimize the objective function value J k ;

[0043] Therefore, the gradient of J k with respect to P ESS,k is solved, and the gradient value is set to 0 to obtain the optimal solution of the power management objective function of the energy storage system;

[0044] The optimal solution of the power management objective function of the energy storage system is finally obtained as

[0045]

[0046] In the equation, m is an intermediate variable, and η ch is the charging and discharging efficiency, At is the step size, E bat is the pool energy.

[0047] Through the optimal solution of the power management objective function of the energy storage system​ As can be seen from the expression, the optimal control objective can be achieved with only simple mathematical operations.

[0048] Through the Analysis shows that k pe The grid properties for control perception are defined. With k pe As the value increases, the controller considers the grid impedance less. (Assume...) α = 1, β = 0 and P ESS,k-1 =0. It can be seen that, assuming the same voltage deviation, k pe The control effect is more pronounced when the value is smaller. Furthermore, k... pe Gain is closely related to control performance. It can be seen that a lower k... pe The value represents a fast control response because it indicates a rigid characteristic of the power grid, thus requiring a higher power level to affect the PCC AC voltage. However, due to k pe The impact depends on the grid conditions, P ESS,k It may not reflect the expected voltage compensation. To make the gain k... pe To accurately estimate the voltage deviation caused by the power input of the energy storage system, it is necessary to estimate the grid impedance.

[0049] Because of k pe By linking 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 taking into account the grid impedance.

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

[0051]

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

[0053] The voltage compensation applied by the energy storage system can be estimated from the maximum PCC voltage deviation of the load's nominal power. Therefore, k pe This can be achieved by replacing the predicted voltage compensation with Apply voltage compensation to the energy storage system. Rated charging power for the energy storage system.

[0054] Figure 2 Displayed in SOC k= 80% and different PCC voltage operating points to analyze the relationship between the α (constant related to voltage regulation) and β (constant related to energy storage system charging) gains. In this case, depending on the characteristics of the system under consideration, a fixed gain k based on the previous design criteria is used pe In addition, the proposed deterministic approach relies on the relationship between α and β regardless of their absolute values. Therefore, to facilitate the analysis of the relationship between β / α, it is considered that α is 1 and β varies from 0.1 to 10.

[0055] In 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 an energy storage system with SOC k = 80%, for a fixed β / α ratio, the reference power of the energy storage system is approximately -10 kW under normal voltage conditions. It can be made explicit that as β increases, the management center will prioritize the energy storage system to be charged at a higher rate.

[0056] Similarly, Figure 2 (b) details the variation of the three β cases throughout the voltage range. It can be seen that the lower the β / α ratio, the higher the priority of the energy storage system discharging behavior to meet the demand for voltage stability control. At the same time, as β / α increases, the curve moves further to the left and the priority of the energy storage system charging increases.

[0057] From the above analysis, it can be seen that considering that the objective 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 at 5. This ratio allows the energy storage system to have the highest charging rate under normal voltage conditions, while still providing the highest discharging power to the energy storage system in the event of a voltage deficit.

[0058] As Figure 3The system for realizing the power management method of the energy storage system of 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 sequentially connected; the data acquisition module is used for acquiring data information of a target power system and an energy storage system and uploading the data information to the system modeling module; the system modeling module is used for modeling the target power system and the energy storage system according to the received data information and the acquired data information and uploading data information to the target construction module; the target construction module is used for constructing a power management target function of the energy storage system according to the received data information and the obtained modeling result and uploading data information to the power management module; and the power management module is used for solving the constructed target function according to the received data information to complete power management of the energy storage system of the target power system.

Claims

1. A method for power management of an energy storage system for a power system, comprising the steps of: S1. obtaining data information of a target power system and an energy storage system; S2. modeling the target power system and the energy storage system according to the data information obtained in step S1; specifically comprising the steps of: a power system grid connects an AC bus; the AC bus connects a DC bus through a series-connected isolation transformer and an AC / DC converter; the energy storage system connects the DC bus directly through an energy storage DC / DC converter; a DC load connects the DC bus through a load DC / DC converter; Direct current bus voltage reference value And direct current bus voltage actual value v DC After subtraction, the active power reference value is obtained through PI control Active power reference value And the difference between the active power actual value P in And the difference between the reactive power reference value And the reactive power actual value Q in The output voltage u of the AC / DC converter is obtained through droop control inv ; The voltage value V of the common coupling point PCC The state of charge value SOC of the battery energy storage system after power management The battery energy storage system voltage u is obtained through the current loop ess ; S3. constructing a power management objective function of the energy storage system according to the modeling result obtained in step S2; specifically comprising the steps of: using the following formula as the power management objective function of the energy storage system: wherein J k is the objective function value; a is a first weight value, and a > 0; b is a second weight value, and b > 0; is the voltage reference value of the PCC; is the estimated PCC voltage value considering the influence of the charging power of the energy storage system, and V PCC,k is the PCC voltage value obtained at the kth measurement point, k pe is a constant related to the active power and the voltage amplitude, AP ESS,k is the power difference between adjacent sampling points, AP ESS,k = P ESS,k - P ESS,k-1 , P ESS,k is the power at the sampling point k; SOC k+1 is the state of charge at the sampling point k+1; S4. solving 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 power systems of claim 1, wherein The solving of the objective function constructed in step S3 in step S4 specifically comprises the steps of: Solve J k Regarding P ESS,k The gradient of the gradient, and let the gradient value be 0, get the optimal solution of the power management objective function of the energy storage system; to obtain the optimal solution of the power management objective function of the energy storage system for where m is an intermediate variable, and η ch is the charge and discharge efficiency, Δt is the step size, E bat is the battery energy.

3. A system implementing the method of power management of an energy storage system for an electric power system according to claim 1 or 2, characterized in that comprising a data acquisition module, a system modeling module, an objective construction module and a power management module; the data acquisition module, the system modeling module, the objective construction module and the power management module are sequentially connected in series; the data acquisition module is used to obtain data information of a target power system and an 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 upload the data information to the objective construction module; the objective 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 result, 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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