A control method and system for a wind energy storage system with minimum grid inertia demand estimation

Abstract

The present invention discloses a control method and system for a wind energy storage system that requires estimation of the minimum inertia of the power grid, relating to the technical field of power grid frequency regulation control. The method first establishes a model of a wind energy storage system with combined thermal power units participating in the primary frequency regulation of the power grid according to the physical information of thermal power units, wind energy storage power stations, and loads in the power grid; then, on the premise of not considering the energy storage system, estimates the minimum inertia demand of the power grid for primary frequency regulation, analyzes whether the actual inertia of the power grid can be satisfied, and conducts control of the energy storage system; finally, considering the minimum inertia demand of the power grid with the energy storage system, further completes the optimized control of power grid generator tripping, load shedding, and the energy storage system. The present invention realizes the primary frequency regulation control under the coordination of the virtual inertia of thermal power units, wind turbines, and the energy storage system through the estimation of the minimum inertia demand of the power grid and the analysis of the actual inertia of the power grid before and after adding the energy storage system, and can effectively optimize the output of thermal power units and the energy storage system in combination with the actual situation of the power grid inertia, improving the active support level of the energy storage system for primary frequency regulation services.

Description

Technical Field

[0001] The present invention relates to a control method and system for a wind energy storage system including an estimation of the minimum inertia requirement of a power grid, and belongs to the technical field of power grid frequency modulation control. Background Art

[0002] In the construction of a power system, the further increase in the proportion of new energy sources such as photovoltaic and wind power and the decrease in the installed capacity of thermal power units will cause a decrease in the overall inertia of the power system. Even if virtual inertia control and other active compensation control methods are adopted in photovoltaic power stations and wind turbine generator stations, their randomness and uncertainty still pose threats and challenges to the frequency stability of the power system. Configuring a certain capacity of energy storage system in new energy power stations can greatly reduce such risks and improve the safety of power grid operation through reasonable and effective control strategies. Therefore, the active cooperation of new energy and energy storage systems with thermal power units for collaborative optimization control to achieve the regulation and stability of the power grid frequency has become a key issue to be studied in the development of power systems.

[0003] At present, experts and scholars at home and abroad have conducted extensive research on the primary frequency modulation control model and active support strategies of wind energy storage systems, including virtual inertia control and improvement of wind turbine converters, fuzzy control and improvement of wind energy storage systems in combination, etc. However, the consideration of the inertia requirement and inertia level of the power system is insufficient, and the control optimization strategy under the coordination of thermal power units, wind turbine generator stations and energy storage systems needs to be improved. For this reason, starting from analyzing the relationship between the minimum inertia requirement of the system and the current inertia level, through the estimation of the minimum inertia requirement for power system frequency modulation before and after adding an energy storage system and the change of the actual inertia level, the present invention establishes an optimized control method for a wind energy storage system. After fully considering the inertia level and requirement of the power system, a collaborative control strategy and optimization process for a wind energy storage system considering the output of thermal power units are established, so as to maximize the ability and rationality of the power system as a whole to meet the requirements of frequency modulation services and effectively ensure the safe operation of the power system. Summary of the Invention

[0004] The present invention provides a control method and system for a wind energy storage system including an estimation of the minimum inertia requirement of a power grid to solve the collaborative optimization control of thermal power units, wind turbine generators and energy storage systems considering the minimum inertia requirement analysis of the power system under the influence of a high proportion of wind turbine generators connected to the power grid frequency, and complete the active control process of primary frequency modulation of the power system.

[0005] The technical solution adopted by the present invention is as follows: A control method for a wind energy storage system including an estimation of the minimum inertia requirement of a power grid, the steps are as follows:

[0006] Step 1: Based on the physical information of thermal power units, wind storage power stations, and loads in the power grid, establish a model for the wind storage system of combined thermal power units to participate in the primary frequency regulation of the power grid, including: the differential equation of the power grid frequency change rate and the active power change amount; the power grid equivalent inertia constraint; the control constraints of the power grid frequency, thermal power units, wind turbines, energy storage systems, and load users' active power change amounts; the energy state constraint of the energy storage system; the maximum frequency deviation, deviation change rate constraint, and power supply rated power constraint; the thermal power unit ramp rate constraint; the energy state limit constraint of the energy storage system;

[0007] Step 2: Establish an estimation model for the minimum inertia demand of the power grid under the condition that the energy storage system does not participate in the primary frequency regulation control mode, and use an optimization algorithm to solve the minimum inertia demand of the power grid;

[0008] Step 3: Judge the relationship between the actual inertia of the power grid and the minimum inertia demand of the power grid under the condition that the energy storage system does not participate in the primary frequency regulation control mode, and determine whether the energy storage system enters the primary frequency regulation control mode or the energy state regulation mode;

[0009] Step 4: Judge the relationship between the actual inertia of the power grid and the minimum inertia demand of the power grid after adding the energy storage system, and determine whether the energy storage system enters the primary frequency regulation control mode or enters the power grid high-frequency generator tripping and low-frequency load shedding mode;

[0010] Step 5: Establish an optimization objective function for the energy storage system to participate in the primary frequency regulation control, aiming at reducing the output of thermal power units, solve the optimization objective function for the energy storage system to participate in the primary frequency regulation control, obtain the power control value of the energy storage system, and complete the primary frequency regulation control of the energy storage system.

[0011] Further preferably, the differential equation of the power grid frequency change rate and the active power change amount is as follows:

[0012]

[0013] Among them, N G represents the number of thermal power units, N W represents the number of wind turbines, N E represents the number of energy storage systems, N L represents the number of load users, H sys represents the power grid equivalent inertia, D sys represents the power grid equivalent damping coefficient, S base represents the power system capacity, f N represents the power grid rated frequency, ΔP G,i (t) represents the active power change amount of the i-th thermal power unit at time t, ΔP W,i (t) represents the active power change amount of the i-th wind turbine at time t, ΔP ESS,i (t) represents the active power change amount of the i-th energy storage system at time t, ΔP L,i(t) represents the change in active power of the i-th load user at time t, and Δf(t) represents the change in grid frequency at time t.

[0014] Further preferably, the grid equivalent inertia constraint is as follows:

[0015]

[0016] Among them, H G,i represents the inertia coefficient of the i-th thermal power unit, H W,i represents the inertia coefficient of the i-th wind power unit, H ESS,i represents the inertia coefficient of the i-th energy storage system, represents the rated power of the i-th thermal power unit, represents the rated power of the i-th wind power unit, represents the rated power of the i-th energy storage system.

[0017] The control constraints of grid frequency, thermal power unit, wind power unit, energy storage system, and the change in active power of load users are as follows:

[0018]

[0019] Among them, P G,i (t) represents the active power of the i-th thermal power unit at time t, P W,i (t) represents the active power of the i-th wind power unit at time t, P ESS,i (t) represents the active power of the i-th energy storage system at time t, P L,i (t) represents the active power of the i-th load user at time t, f(t) represents the grid frequency at time t, t0 represents the initial time, R G,i represents the droop coefficient of the i-th thermal power unit, T G,ch,i represents the time constant of the i-th steam turbine, T G,i represents the time constant of the i-th governor, T E,i represents the time constant of the i-th energy storage system, T W,i represents the time constant of the i-th wind power unit, K W,i represents the virtual inertia coefficient of the i-th wind power unit, K E,i represents the control coefficient of the i-th energy storage system, and s represents the transfer function.

[0020] Further preferably, the energy state constraint of the energy storage system is as follows:

[0021]

[0022] Among them, C SOE,i (t) represents the energy state of the i-th energy storage system at time t, η cDenote the charging efficiency of the energy storage system as η d Denote the discharging efficiency of the energy storage system; Δt represents the time interval, Denote the capacity of the i-th energy storage system.

[0023] Further preferably, the maximum frequency deviation, the deviation change rate constraint, and the power supply rated power constraint are as follows:

[0024]

[0025] Among them, δ represents the allowable threshold of the grid frequency deviation, and ε represents the allowable threshold of the grid frequency change rate, Denote the maximum output power of the i-th wind turbine at time t.

[0026] Further preferably, the ramp rate constraint of the thermal power unit is as follows:

[0027]

[0028] Among them, Denote the ramp threshold of the i-th thermal power unit.

[0029] Further preferably, the energy state limit constraint of the energy storage is as follows:

[0030]

[0031] Among them, Denote the upper limit of the energy state of the i-th energy storage system, Denote the lower limit of the energy state of the i-th energy storage system.

[0032] Further preferably, the specific process of step 2 is as follows:

[0033] Step 2.1: In terms of the constraints of the grid frequency regulation control process, let the control coefficient of the energy storage system be equal to zero, define the grid inertia demand as the optimization variable, let the grid inertia demand be equal to the grid equivalent inertia in formula (1), and at the same time remove the rated power of the energy storage system, the inertia coefficient of the energy storage system, and the energy state constraint of the energy storage system from the power system capacity; in addition, add the following range constraint for the grid inertia demand:

[0034]

[0035] Among them, H eq Denote the grid inertia demand, Denote the upper limit of the grid inertia demand;

[0036] The grid minimum inertia demand estimation model is expressed as:

[0037]

[0038] In the formula, Represents the minimum inertia demand of the power grid;

[0039] Step 2.2: Set the allowable threshold of power grid frequency deviation, the allowable threshold of power grid frequency change rate, the ramp threshold of thermal power units, and the virtual inertia control coefficient of wind power units. Taking the power grid inertia demand as the optimization variable, use the swarm intelligence optimization algorithm to obtain the minimum inertia demand of the power grid.

[0040] Further preferably, the said Step 3 includes:

[0041] Step 3.1: In the mode where the energy storage system does not participate in primary frequency regulation control, the true inertia of the power grid where the energy storage system does not participate in primary frequency regulation The calculation formula is as follows:

[0042]

[0043] Judge the true inertia of the power grid where the energy storage system does not participate in primary frequency regulation Whether it is greater than the minimum inertia demand of the power grid If so, the energy storage system enters the energy regulation mode and proceeds to Step 3.2; if not, the energy storage system enters the primary frequency regulation control mode and proceeds to Step 4;

[0044] Step 3.2: Establish an optimization objective function for the energy regulation control of the energy storage system. Taking the optimal energy state of the energy storage system as the goal, solve the optimization objective function for the energy regulation control of the energy storage system to obtain the power control value of the energy storage system and complete the regulation control of the energy state of the energy storage system.

[0045] Further preferably, the specific process of the said Step 3.2 is as follows:

[0046] Step 3.2.1: Taking the optimal energy state of the energy storage system as the goal, establish an optimization objective function for the energy regulation control of the energy storage system;

[0047]

[0048] Among them, Represents the optimal energy state of the i-th energy storage system, which is the set parameter when solving the parameters of the optimization objective function for the energy regulation control of the energy storage system. T is the primary frequency regulation time of the power grid; the optimization objective function for the energy regulation control of the energy storage system includes all the constraint conditions described in Step 1, and the true inertia of the power grid is And the control coefficient of the energy storage system is equal to zero.

[0049] Step 3.2.2: Using the swarm intelligence optimization algorithm, with the control coefficient of the energy storage system as the optimization variable and the optimal energy state of the energy storage system as the objective, combined with the operation constraints of the energy storage system participating in the frequency regulation control process, solve the optimization objective function of the energy storage system energy regulation control, obtain the power control value of the energy storage system, and complete the energy state regulation control of the energy storage system.

[0050] Further preferably, the specific process of step 4 is as follows:

[0051] Step 4.1: In the mode of the energy storage system participating in primary frequency regulation control, the true inertia of the power grid in which the energy storage system participates in primary frequency regulation The calculation formula is as follows:

[0052]

[0053] Judge whether the true inertia of the power grid in which the energy storage system participates in primary frequency regulation is greater than the minimum inertia requirement of the power grid If so, go to step 5 to start optimizing the primary frequency regulation control process of the energy storage system; if not, go to step 4.2 to start the power grid high-frequency generator tripping or low-frequency load shedding control process;

[0054] Step 4.2: If the power grid frequency deviation is greater than 0, it is necessary to gradually cut off the thermal power units or wind turbine units, and the specific cut-off sequence should be carried out in accordance with the operation requirements; if the power grid frequency deviation is less than 0, it is necessary to gradually reduce the electrical load, and the specific reduction sequence should be carried out in accordance with the importance of the load, and return to step 2.

[0055] Further preferably, the specific process of step 5 is as follows:

[0056] Step 5.1: With the goal of reducing the output of thermal power units, establish an optimization objective function for the energy storage system to participate in primary frequency regulation control:

[0057]

[0058] The optimization objective function for the energy storage system to participate in primary frequency regulation control includes all the constraint conditions described in step 1, the true inertia of the power grid is and the control coefficient of the energy storage system is not equal to zero;

[0059] Step 5.2: Using the swarm intelligence optimization algorithm, with the control coefficient of the energy storage system as the optimization variable and the goal of reducing the output of thermal power units, combined with the operation constraints of the energy storage system participating in the frequency regulation control process, solve the optimization objective function for the energy storage system to participate in primary frequency regulation control, obtain the power control value of the energy storage system, and complete the primary frequency regulation control of the energy storage system.

[0060] The present invention also discloses a wind-storage system control system including an estimation of the minimum inertia requirement of the power grid, comprising:

[0061] The wind energy storage system of the combined thermal power unit participates in the primary frequency regulation model module of the power grid, which is used to set: the differential equation of the power grid frequency change rate and the active power change amount; the equivalent inertia constraint of the power grid; the control constraints of the power grid frequency, thermal power unit, wind turbine, energy storage system, and load user's active power change amount; the energy state constraint of the energy storage system; the maximum frequency deviation, deviation change rate constraint, and power supply rated power constraint; the ramp rate constraint of the thermal power unit; the energy state limit constraint of the energy storage;

[0062] The power grid minimum inertia demand calculation module is used to estimate the power grid minimum inertia demand according to the power grid minimum inertia demand estimation model and solve the power grid minimum inertia demand by using an optimization algorithm;

[0063] The inertia judgment and comparison module is used to judge the relationship between the actual inertia of the power grid and the power grid minimum inertia demand in the case where the energy storage system does not participate in the primary frequency regulation control mode; and judge the relationship between the actual inertia of the power grid and the power grid minimum inertia demand after adding the energy storage system;

[0064] The frequency regulation control module is used to execute the primary frequency regulation control mode, energy state regulation mode, or power grid high-frequency load shedding and low-frequency load shedding mode according to the result judged by the inertia judgment and comparison module, and is used to establish an optimization objective function for the energy storage system to participate in the primary frequency regulation control. With the goal of reducing the output of the thermal power unit, solve the optimization objective function for the energy storage system to participate in the primary frequency regulation control, obtain the power control value of the energy storage system, and complete the primary frequency regulation control of the energy storage system.

[0065] Compared with the closest prior art, the beneficial effects of the present invention are: compared with the prior art wind energy storage system combined frequency regulation control method, the present invention calculates the power grid minimum inertia demand in the case of no energy storage system output, compares it with the actual inertia of the power grid, and establishes an optimization objective function for the energy storage system energy regulation control to meet the power grid minimum inertia demand and a primary frequency regulation control mode with inertia support of the energy storage system when the power grid minimum inertia demand is not met, establishes an optimal control process for power grid low-frequency load shedding, high-frequency load shedding, or taking into account the states of thermal power and energy storage systems, forms a control method for the wind energy storage system considering the estimation of the power grid minimum inertia demand, reasonably optimizes the coordinated control process of thermal power, wind power, and energy storage systems under the consideration of the current power grid inertia level and demand, effectively takes into account the operating states of thermal power, wind power, and energy storage systems, improves the primary frequency regulation ability of the power grid, and will be of great significance for the wind energy storage system to actively support the power grid frequency service. Description of the Drawings

[0066] The present invention will be further described below with reference to the drawings.

[0067] Figure 1 It is a flowchart of a control method for a wind energy storage system including the estimation of the power grid minimum inertia demand described in the present invention.

[0068] Figure 2 It is a schematic diagram of the wind energy storage system of a combined thermal power unit participating in the primary frequency regulation of the power grid. Specific implementation manners

[0069] To enable those skilled in the art to better understand the technical solution of this invention patent, in combination with the accompanying drawings in the embodiments of this invention patent, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0070] The present invention provides a control method for a wind energy storage system including the estimation of the minimum inertia requirement of the power grid. Taking a power system composed of multiple thermal power plants, a wind energy storage power station, and multiple load users as an example, the implementation steps of the method in this embodiment are shown as Figure 1 shown, and specifically include the following steps:

[0071] Step 1: According to the physical information of thermal power units, wind energy storage power stations, and loads in the power grid, establish a model of the wind energy storage system of a combined thermal power unit participating in the primary frequency regulation of the power grid as shown in Figure 2 shown, which mainly includes: a differential equation of the power grid frequency change rate and the active power change amount, as shown in Equation (1); a power grid equivalent inertia constraint, as shown in Equation (2); a control constraint on the power grid frequency, thermal power units, wind turbines, energy storage systems, and load users' active power change amounts, as shown in Equation (3); an energy state constraint of the energy storage system, as shown in Equation (4); a maximum frequency deviation, deviation change rate constraint, and power supply rated power constraint, as shown in Equation (5); a thermal power unit ramp rate constraint, as shown in Equation (6); and an energy state limit constraint of the energy storage, as shown in Equation (7).

[0072]

[0073] Among them, N G represents the number of thermal power units, N W represents the number of wind turbines, N E represents the number of energy storage systems, N L represents the number of load users, H sys represents the power grid equivalent inertia, D sys represents the power grid equivalent damping coefficient, S base represents the power system capacity, f N represents the power grid rated frequency, ΔP G,i (t) represents the active power change amount of the i-th thermal power unit at time t, ΔP W,i (t) represents the active power change amount of the i-th wind turbine at time t, ΔPESS,i (t) represents the change in active power of the i-th energy storage system at time t, ΔP L,i (t) represents the change in active power of the i-th load user at time t, and Δf(t) represents the change in grid frequency at time t.

[0074]

[0075] Among them, H G,i represents the inertia coefficient of the i-th thermal power unit, H W,i represents the inertia coefficient of the i-th wind power unit, H ESS,i represents the inertia coefficient of the i-th energy storage system, represents the rated power of the i-th thermal power unit, represents the rated power of the i-th wind power unit, represents the rated power of the i-th energy storage system.

[0076]

[0077] Among them, P G,i (t) represents the active power of the i-th thermal power unit at time t, P W,i (t) represents the active power of the i-th wind power unit at time t, P ESS,i (t) represents the active power of the i-th energy storage system at time t, P L,i (t) represents the active power of the i-th load user at time t, f(t) represents the grid frequency at time t, t0 represents the initial time, R G,i represents the droop coefficient of the i-th thermal power unit, T G,ch,i represents the i-th steam turbine time constant, T G,i represents the i-th governor time constant, T E,i represents the i-th energy storage system time constant, T W,i represents the i-th wind power unit time constant, K W,i represents the virtual inertia coefficient of the i-th wind power unit, K E,i represents the control coefficient of the i-th energy storage system, and s represents the transfer function.

[0078]

[0079] Among them, C SOE,i (t) represents the energy state of the i-th energy storage system at time t, η c represents the charging efficiency of the energy storage system, η d represents the discharging efficiency of the energy storage system; Δt represents the time interval, represents the capacity of the i-th energy storage system.

[0080]

[0081] Among them, δ represents the allowable threshold of the grid frequency deviation, and ε represents the allowable threshold of the grid frequency change rate. represents the maximum output power of the i-th wind turbine at time t.

[0082]

[0083] Among them, represents the ramp threshold of the i-th thermal power unit.

[0084]

[0085] Among them, represents the upper limit of the energy state of the i-th energy storage system. represents the lower limit of the energy state of the i-th energy storage system.

[0086] Step 2: Establish an estimation model for the minimum inertia demand of the power grid in the case where the energy storage system does not participate in the primary frequency regulation control mode, and use an optimization algorithm to solve the minimum inertia demand of the power grid.

[0087] Step 2.1: Regarding the constraints in the power grid frequency regulation control process, set the control coefficient of the energy storage system to zero, define the power grid inertia demand as the optimization variable, make the power grid inertia demand equal to the equivalent inertia of the power grid in formula (1), and at the same time remove the rated power of the energy storage system, the inertia coefficient of the energy storage system, and the energy state constraint of the energy storage system from the power system capacity; in addition, add the following range constraint for the power grid inertia demand:

[0088]

[0089] Among them, H eq represents the power grid inertia demand. represents the upper limit of the power grid inertia demand.

[0090] The estimation model for the minimum inertia demand of the power grid is expressed as:

[0091]

[0092] In the formula, represents the minimum inertia demand of the power grid.

[0093] Step 2.2: Set the allowable threshold of the power grid frequency deviation, the allowable threshold of the power grid frequency change rate, the ramp threshold of the thermal power unit, and the virtual inertia control coefficient of the wind turbine. Taking the power grid inertia demand as the optimization variable, use swarm intelligence optimization algorithms such as genetic algorithms and particle swarm algorithms to obtain the minimum inertia demand of the power grid.

[0094] Step 3: Determine the relationship between the actual inertia of the power grid and the minimum inertia demand of the power grid when the energy storage system does not participate in the primary frequency modulation control mode, and determine whether the energy storage system enters the primary frequency modulation control mode or the energy state regulation mode.

[0095] Step 3.1: When the energy storage system does not participate in the primary frequency modulation control mode The actual inertia of the power grid when the energy storage system does not participate in primary frequency modulation The calculation formula is as follows:

[0096]

[0097] Judge the actual inertia of the power grid when the energy storage system does not participate in primary frequency modulation Whether it is greater than the minimum inertia demand of the power grid If so, the energy storage system enters the energy regulation mode and proceeds to Step 3.2; if not, the energy storage system enters the primary frequency modulation control mode and proceeds to Step 4.

[0098] Step 3.2: Establish an optimization objective function for the energy regulation control of the energy storage system. With the optimal energy state of the energy storage system as the goal, solve the optimization objective function for the energy regulation control of the energy storage system to obtain the power control value of the energy storage system and complete the energy state regulation control of the energy storage system.

[0099] Step 3.2.1: With the optimal energy state of the energy storage system as the goal, establish an optimization objective function for the energy regulation control of the energy storage system;

[0100]

[0101] Among them, represents the optimal energy state of the i-th energy storage system, which is the set parameter during the solution of the parameters of the optimization objective function for the energy regulation control of the energy storage system. T is the primary frequency modulation time of the power grid. The optimization objective function for the energy regulation control of the energy storage system includes all the constraint conditions described in Step 1. The actual inertia of the power grid is and the control coefficient of the energy storage system is equal to zero.

[0102] Step 3.2.2: Use the swarm intelligence optimization algorithm with the control coefficient of the energy storage system as the optimization variable and the optimal energy state of the energy storage system as the goal, and combine the operation constraints during the process of the energy storage system participating in the frequency modulation control to solve the optimization objective function for the energy regulation control of the energy storage system to obtain the power control value of the energy storage system and complete the energy state regulation control of the energy storage system.

[0103] Step 4: Determine the relationship between the actual inertia of the power grid after adding the energy storage system and the minimum inertia demand of the power grid, and determine whether the energy storage system enters the primary frequency modulation control mode or enters the high-frequency load shedding and low-frequency load shedding mode of the power grid;

[0104] Step 4.1: Under the condition that the energy storage system participates in the primary frequency modulation control mode, the actual inertia of the power grid in which the energy storage system participates in the primary frequency modulation The calculation formula is as follows:

[0105]

[0106] Judge whether the actual inertia of the power grid in which the energy storage system participates in the primary frequency modulation is greater than the minimum inertia requirement of the power grid If it is, go to Step 5 to start optimizing the primary frequency modulation control process of the energy storage system; if not, go to Step 4.2 to start the power grid high-frequency generator tripping or low-frequency load shedding control process;

[0107] Step 4.2: If the power grid frequency deviation is greater than 0, it is necessary to gradually cut off the thermal power units or wind turbines, and the specific cutting sequence should be carried out in accordance with the operation requirements; if the power grid frequency deviation is less than 0, it is necessary to gradually reduce the electrical load, and the specific reduction sequence should be carried out in accordance with the importance of the load, and return to Step 2;

[0108] Step 5: Establish an optimization objective function for the energy storage system to participate in the primary frequency modulation control. With the goal of reducing the output of the thermal power unit, solve the optimization objective function for the energy storage system to participate in the primary frequency modulation control, obtain the power control value of the energy storage system, and complete the primary frequency modulation control of the energy storage system;

[0109] Step 5.1: With the goal of reducing the output of the thermal power unit, establish an optimization objective function for the energy storage system to participate in the primary frequency modulation control:

[0110]

[0111] The optimization objective function for the energy storage system to participate in the primary frequency modulation control includes all the constraint conditions described in Step 1, the actual inertia of the power grid is and the control coefficient of the energy storage system is not equal to zero.

[0112] Step 5.2: Use the swarm intelligence optimization algorithm with the control coefficient of the energy storage system as the optimization variable, with the goal of reducing the output of the thermal power unit, and combine the operation constraints of the energy storage system participating in the frequency modulation control process to solve the optimization objective function for the energy storage system to participate in the primary frequency modulation control, obtain the power control value of the energy storage system, and complete the primary frequency modulation control of the energy storage system.

[0113] This embodiment provides a wind energy storage system control system including an estimation of the minimum inertia requirement of the power grid, including:

[0114] The wind energy storage system of the combined thermal power unit participates in the primary frequency modulation model module of the power grid, which is used to set: the differential equation of the grid frequency change rate and the active power change amount; the grid equivalent inertia constraint; the grid frequency, thermal power unit, wind turbine unit, energy storage system, and load user active power change amount control constraints; the energy state constraint of the energy storage system; the maximum frequency deviation, deviation change rate constraint, and power supply rated power constraint; the ramp rate constraint of the thermal power unit; the energy state limit constraint of the energy storage system;

[0115] The grid minimum inertia demand calculation module is used to estimate the grid minimum inertia demand according to the grid minimum inertia demand estimation model and solve the grid minimum inertia demand by using an optimization algorithm;

[0116] The inertia judgment and comparison module is used to judge the relationship between the actual grid inertia and the grid minimum inertia demand in the case where the energy storage system does not participate in the primary frequency modulation control mode; and judge the relationship between the actual grid inertia and the grid minimum inertia demand after adding the energy storage system;

[0117] The frequency modulation control module is used to execute the primary frequency modulation control mode, the energy state adjustment mode, or the grid high-frequency load shedding and low-frequency load shedding mode according to the result judged by the inertia judgment and comparison module, and is used to establish an optimization objective function for the energy storage system to participate in the primary frequency modulation control. With the goal of reducing the output of the thermal power unit, solve the optimization objective function for the energy storage system to participate in the primary frequency modulation control, obtain the power control value of the energy storage system, and complete the primary frequency modulation control of the energy storage system.

[0118] Finally, it should be noted that: the described embodiments are only a part of the embodiments of the present application, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

Claims

1. A control method for a wind energy storage system with estimation of the minimum inertia requirement of the power grid, characterized in that, The steps are as follows: Step 1: According to the physical information of thermal power units, wind storage power stations and loads in the power grid, establish a model for the wind storage system of combined thermal power units to participate in the primary frequency regulation of the power grid, including: the differential equation of the power grid frequency change rate and the active power change; the power grid equivalent inertia constraint; the control constraints of the power grid frequency, thermal power units, wind turbines, energy storage systems and load users' active power changes; the energy state constraint of the energy storage system; the maximum frequency deviation, deviation change rate constraint and power supply rated power constraint; the ramp rate constraint of thermal power units; the energy state limit constraint of energy storage. Step 2: Establish an estimation model for the minimum inertia demand of the power grid under the condition that the energy storage system does not participate in the primary frequency regulation control mode, and use an optimization algorithm to solve the minimum inertia demand of the power grid. Step 3: Judge the relationship between the actual inertia of the power grid and the minimum inertia demand of the power grid under the condition that the energy storage system does not participate in the primary frequency regulation control mode, and determine whether the energy storage system enters the primary frequency regulation control mode or the energy state regulation mode. Step 4: Judge the relationship between the actual inertia of the power grid and the minimum inertia demand of the power grid after adding the energy storage system, and determine whether the energy storage system enters the primary frequency regulation control mode or enters the power grid high-frequency load shedding and low-frequency load shedding mode. Step 5: Establish an optimization objective function for the energy storage system to participate in the primary frequency regulation control. With the goal of reducing the output of thermal power units, solve the optimization objective function for the energy storage system to participate in the primary frequency regulation control, and obtain the power control value of the energy storage system to complete the primary frequency regulation control of the energy storage system. The differential equation of the power grid frequency change rate and the active power change is as follows: ； Among them, represents the number of thermal power units, represents the number of wind turbines, represents the number of energy storage systems, represents the number of load users, represents the equivalent inertia of the power grid, represents the equivalent damping coefficient of the power grid, represents the power system capacity, represents the rated frequency of the power grid, represents at the active power change of the th thermal power unit at time represents at the active power change of the th wind turbine at time represents at the active power change of the th energy storage system at time represents at the active power change of the th load user at time represents the change in the power grid frequency at time t; The power grid equivalent inertia constraint is as follows: ； Among them, represents the inertia coefficient of the th thermal power unit, represents the inertia coefficient of the th wind power unit, represents the inertia coefficient of the th energy storage system, represents the rated power of the th thermal power unit, represents the rated power of the th wind power unit, represents the rated power of the th energy storage system.

2. The wind-storage system control method with minimum grid inertia demand estimation according to claim 1, characterized in that The control constraints of the power grid frequency, thermal power units, wind turbines, energy storage systems and load users' active power changes are as follows: ； Among them, represents the active power of the th thermal power unit at time represents the active power of the th wind power unit at time represents the active power of the th energy storage system at time represents the active power of the th load user at time represents the grid frequency at time represents the initial time, represents the th droop coefficient of the thermal power unit, represents the th steam turbine time constant, represents the th governor time constant, represents the th energy storage system time constant, represents the th wind power unit time constant, represents the th virtual inertia coefficient of the wind power unit, represents the th energy storage system control coefficient, represents the transfer function; The energy state constraint of the energy storage system is as follows: ； Among them, represents the energy state of the nth energy storage system at moment, represents the charging efficiency of the energy storage system, represents the discharging efficiency of the energy storage system; represents the time interval, represents the capacity of the nth energy storage system; The maximum frequency deviation, deviation change rate constraint and power supply rated power constraint are as follows: ； Among them, represents the allowable threshold of the power grid frequency deviation, represents the allowable threshold of the power grid frequency change rate, represents the maximum output power of the The ramp rate constraint of thermal power units is as follows: ； Among them, represents the ramping threshold of the i-th thermal power unit; The energy state limit constraint of energy storage is as follows: ； Among them, represents the upper limit of the energy state of the th energy storage system, represents the lower limit of the energy state of the th energy storage system.

3. The wind power storage system control method with minimum inertia demand estimation of power grid according to claim 2, characterized in that The specific process of Step 2 is as follows: Step 2.1: In terms of the constraints of the power grid frequency regulation control process, let the control coefficient of the energy storage system be equal to zero, define the power grid inertia demand as the optimization variable, let the power grid inertia demand be equal to the power grid equivalent inertia in formula (1), and at the same time remove the rated power of the energy storage system, the inertia coefficient of the energy storage system and the energy state constraint of the energy storage system from the power system capacity; in addition, add the following range constraint for the power grid inertia demand: ； Among them, represents the grid inertia demand, represents the upper limit of the grid inertia demand; The power grid minimum inertia demand estimation model is expressed as: ； Wherein, represents the minimum inertia requirement of the power grid; Step 2.2: Set the allowable threshold of the power grid frequency deviation, the allowable threshold of the power grid frequency change rate, the ramp threshold of thermal power units and the virtual inertia control coefficient of wind turbines. With the power grid inertia demand as the optimization variable, use the swarm intelligence optimization algorithm to obtain the minimum inertia demand of the power grid.

4. The wind-solar energy storage system control method with minimum grid inertia demand estimation according to claim 3, characterized in that Step 3 includes: Step 3.1: In the case where the energy storage system does not participate in the primary frequency regulation control mode, the true inertia of the power grid without the energy storage system participating in primary frequency regulation The calculation formula is as follows: ； Judge the true inertia of the power grid where the energy storage system does not participate in primary frequency modulation Is it greater than the minimum inertia demand of the power grid , if so, the energy storage system enters the energy regulation mode and proceeds to step 3.2; if not, the energy storage system enters the primary frequency modulation control mode and proceeds to step 4; Step 3.2: Establish an optimization objective function for the energy regulation control of the energy storage system. With the best energy state of the energy storage system as the goal, solve the optimization objective function for the energy regulation control of the energy storage system, and obtain the power control value of the energy storage system to complete the energy state regulation control of the energy storage system.

5. The wind energy storage system control method including the estimation of the minimum inertia requirement of the power grid according to claim 4, characterized in that The specific process of Step 3.2 is as follows: Step 3.2.1: Establish an optimization objective function for the energy regulation control of the energy storage system with the goal of the optimal energy state of the energy storage system. ； Among them, represents the optimal energy state of the th energy storage system, which is a set parameter when solving the parameters of the optimization objective function for the energy regulation and control of the energy storage system. T is the primary frequency regulation time of the power grid. The optimization objective function for the energy regulation and control of the energy storage system includes all the constraint conditions in Step 1. The true inertia of the power grid is and the control coefficient of the energy storage system is equal to zero. Step 3.2.2: Using the swarm intelligence optimization algorithm, with the control coefficient of the energy storage system as the optimization variable and the optimal energy state of the energy storage system as the objective, combined with the operation constraints of the energy storage system participating in the frequency regulation control process, solve the optimization objective function of the energy storage system energy regulation control to obtain the power control value of the energy storage system and complete the energy state regulation control of the energy storage system.

6. The wind-solar energy storage system control method with minimum grid inertia demand estimation according to claim 5, characterized in that The specific process of step 4 is as follows: Step 4.1: Under the primary frequency regulation control mode in which the energy storage system participates, the true inertia of the power grid in which the energy storage system participates in primary frequency regulation The calculation formula is as follows: ； Judge the true inertia of the power grid in which the energy storage system participates in primary frequency regulation Whether it is greater than the minimum inertia demand of the power grid If so, go to step 5 to start optimizing the primary frequency regulation control process of the energy storage system; if not, go to step 4.2 to start the high-frequency generator tripping or low-frequency load shedding control process of the power grid; Step 4.2: If the grid frequency deviation is greater than 0, it is necessary to gradually cut off the thermal power units or wind turbines, and the specific cutting sequence should be carried out in accordance with the operation requirements; if the grid frequency deviation is less than 0, it is necessary to gradually reduce the electrical load, and the specific reduction sequence should be carried out in accordance with the importance of the load, and return to step 2.

7. The control method of the wind power and energy storage system with the minimum inertia demand estimation of the power grid according to claim 6, characterized in that The specific process of step 5 is as follows: Step 5.1: With the goal of reducing the output of the thermal power unit, establish the optimization objective function of the energy storage system participating in primary frequency regulation control: ； The optimization objective function for the energy storage system to participate in primary frequency regulation includes all the constraint conditions described in Step 1, and the true inertia of the power grid is and the control coefficient of the energy storage system is not equal to zero; Step 5.2: Using the swarm intelligence optimization algorithm, with the control coefficient of the energy storage system as the optimization variable and the goal of reducing the output of the thermal power unit, combined with the operation constraints of the energy storage system participating in the frequency regulation control process, solve the optimization objective function of the energy storage system participating in primary frequency regulation control to obtain the power control value of the energy storage system and complete the energy storage system's participation in primary frequency regulation control.

8. A control system for a wind energy storage system with estimation of the minimum inertia requirement of the power grid, characterized in that, Including: A wind-solar-storage system combined with a thermal power unit participating in the grid primary frequency regulation model module, used to set: the differential equation of the grid frequency change rate and the active power change amount; the grid equivalent inertia constraint; the grid frequency, thermal power unit, wind turbine, energy storage system, and load user active power change amount control constraint; the energy storage system energy state constraint; the maximum frequency deviation, deviation change rate constraint, and power supply rated power constraint; the thermal power unit ramp rate constraint; the energy storage energy state limit constraint; The grid minimum inertia demand calculation module is used to estimate the grid minimum inertia demand according to the grid minimum inertia demand estimation model and solve the grid minimum inertia demand using the optimization algorithm; The inertia judgment and comparison module is used to judge the relationship between the actual grid inertia and the grid minimum inertia demand in the case where the energy storage system does not participate in the primary frequency regulation control mode; and judge the relationship between the actual grid inertia and the grid minimum inertia demand after adding the energy storage system; The frequency regulation control module is used to execute the primary frequency regulation control mode, energy state regulation mode, or grid high-frequency load shedding and low-frequency load shedding mode according to the judgment result of the inertia judgment and comparison module, and is used to establish the optimization objective function of the energy storage system participating in primary frequency regulation control, with the goal of reducing the output of the thermal power unit, solve the optimization objective function of the energy storage system participating in primary frequency regulation control to obtain the power control value of the energy storage system and complete the energy storage system's participation in primary frequency regulation control; The differential equation of the grid frequency change rate and the active power change amount is as follows: ； Among them, represents the number of thermal power units, represents the number of wind turbines, represents the number of energy storage systems, represents the number of load users, represents the equivalent inertia of the power grid, represents the equivalent damping coefficient of the power grid, represents the power system capacity, represents the rated frequency of the power grid, represents at time the th active power change of the thermal power unit, represents at time the th active power change of the wind turbine, represents at time the th active power change of the energy storage system, represents at time the th active power change of the load user, represents the change in the power grid frequency at time t; The grid equivalent inertia constraint is as follows: ； Among them, represents the inertia coefficient of the th thermal power unit, represents the inertia coefficient of the th wind power unit, represents the inertia coefficient of the th energy storage system, represents the rated power of the th thermal power unit, represents the rated power of the th wind power unit, represents the rated power of the th energy storage system.

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