Flywheel energy storage-fixed speed pumping storage coordinated frequency modulation system and parameter optimization configuration method
By constructing a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, optimizing the flywheel energy storage capacity and control strategy, the problems of slow response speed and high construction cost of constant-speed pumped storage were solved, achieving efficient grid frequency regulation and improved economic efficiency.
Patent Information
- Application Number
- CN202610241765.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-28
- Publication Date
- 2026-06-23
AI Technical Summary
Constant-speed pumped storage has a slow power response speed, making it difficult to meet the short-term high power demand during the primary frequency regulation phase of the power grid. Furthermore, flywheel energy storage has high construction costs, and there is an urgent need to optimize its configuration to improve frequency regulation capabilities.
A flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system is constructed. By coordinating the control of the flywheel energy storage array and the constant-speed pumped storage unit, the flywheel energy storage capacity is optimized. Simulation models and parameter optimization methods are used to determine the optimal number of flywheels and the grid frequency disturbance threshold. Combined with inertial control and droop control strategies, the coordinated operation of flywheel energy storage and constant-speed pumped storage is achieved.
It significantly improves the power response speed of constant-speed pumped storage units, reduces the number of unit start-ups and shutdowns, extends service life, reduces construction costs, and enhances the frequency regulation response characteristics and economic practicality of the power grid.
Smart Images
Figure CN122267803A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of power system frequency regulation technology, specifically, it relates to a flywheel energy storage-constant speed pumped storage coordinated frequency regulation system and a parameter optimization configuration method. Background Technology
[0002] The rapid increase in the proportion of renewable energy sources with randomness and volatility in the power grid has led to a decrease in grid inertia and a significant increase in the risk of frequency degradation. Energy storage technology, as a key technology in the energy internet, can participate in grid frequency regulation by contributing its own power, thereby improving the grid's ability to absorb renewable energy. Constant-speed pumped storage power stations, as a common large-scale energy storage technology, have large storage capacity and a wide range of applications. However, constant-speed pumped storage has a slow power response speed, making it difficult to meet the short-term high-power demands of the grid during primary frequency regulation. Flywheel energy storage has advantages such as fast power response speed, small footprint, and clean and environmentally friendly operation. Using flywheel energy storage in conjunction with constant-speed pumped storage to participate in grid frequency regulation can significantly improve the shortcomings of constant-speed pumped storage units, such as slow power response speed and output reversal.
[0003] Therefore, there is an urgent need for a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system and a parameter optimization configuration method to optimize the capacity configuration of the flywheel energy storage system and reduce the construction cost of flywheel energy storage. This will enable coordinated operation between flywheel energy storage and constant-speed pumped storage, improving the frequency regulation capability of constant-speed pumped storage power stations. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system and parameter optimization configuration method. By coordinating the control of flywheel-constant-speed pumped storage and optimizing the configuration of flywheel energy storage capacity, the construction cost of flywheel energy storage is reduced, and the coordinated operation of flywheel energy storage and constant-speed pumped storage is realized.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, including a constant-speed pumped storage unit and a flywheel energy storage array system connected in parallel on the grid side. The constant-speed pumped storage unit includes a speed governor, an electro-hydraulic servo system, a water pump turbine, a synchronous motor, and a transformer. The speed governor, the electro-hydraulic servo system, and the water pump turbine are electrically connected in sequence. The water pump turbine is connected to the synchronous motor through a drive shaft. The synchronous motor is electrically connected to the transformer, so that the synchronous motor is connected to the power grid. The flywheel energy storage array system consists of several flywheel energy storage mechanisms connected in parallel. Each flywheel energy storage mechanism includes a flywheel, a permanent magnet synchronous motor, and a converter. The flywheel is connected to the permanent magnet synchronous motor through a transmission shaft. The converter is connected to the stator winding of the permanent magnet synchronous motor. The converter of each flywheel energy storage mechanism is connected to the same converter through a DC bus. The converter is electrically connected to a transformer. The transformer converts the voltage on the AC side of the converter to the grid voltage, so that the converter is connected to the grid.
[0006] This invention also provides a parameter optimization configuration method for a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, comprising the following steps: Step 1: Construct a simulation model of the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system and determine the frequency regulation strategy; Step 2: Obtain data on the effect of the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system on the primary frequency regulation of the power grid through simulation testing; Step 3: Establish constraints and optimize the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system with the minimum flywheel energy storage array capacity as the objective function. Select the theoretically optimal number of flywheels and the theoretically optimal grid frequency disturbance threshold.
[0007] In the preferred embodiment, the simulation model constructed in step 1 includes a constant-speed pumped storage unit model, a flywheel energy storage array model, and a power grid frequency response model.
[0008] In the preferred embodiment, in the constant-speed pumped storage unit model, the speed governor model is a PI controller, the electro-hydraulic servo system is a servo motor and is represented by a first-order transfer function model, the output of the servo motor is the guide vane opening adjustment speed, the guide vane opening adjustment speed is integrated to obtain the guide vane opening command and input to the pump turbine, the pump turbine is a nonlinear model, and the output mechanical power is related to the guide vane opening and the grid frequency.
[0009] In the preferred embodiment, the flywheel energy storage array model employs a dual-closed-loop PI control strategy for the flywheel's permanent magnet synchronous motor. The outer loop selects either a speed loop or a power loop based on the control objective. The speed loop is selected when the grid frequency does not fluctuate or the flywheel speed is outside the specified operating range, while the power loop is selected when the flywheel participates in frequency regulation. The inner loop is a current loop.
[0010] In the preferred embodiment, the power grid frequency response model adopts a simplified SFR model, whose transfer function expression is: ; in: Represents the power grid frequency response transfer function; Indicates the change in power grid frequency; Power variation of conventional generator sets; Power variation in a flywheel energy storage array system; This indicates the change in load power. Represents the system's inertial time constant; Represents a complex variable in the complex frequency domain; This represents the damping coefficient of the system.
[0011] In the preferred embodiment, the frequency modulation control strategy determined in step 1 is as follows: Set a threshold for the magnitude of power grid frequency disturbances. When the magnitude of the power grid frequency disturbance is less than At this time, the constant-speed pumped storage unit does not participate in frequency regulation; only the flywheel energy storage array system participates in grid inertial response and primary frequency regulation. The frequency regulation strategy uses a combination of inertial control and droop control, and the power command expression is as follows: ; in, This is the frequency modulation power command value for the flywheel energy storage array; For the flywheel energy storage array, is the inertial control coefficient. For the droop control coefficient of the flywheel energy storage array, This refers to the change in power grid frequency. When the magnitude of the power grid frequency disturbance is greater than During frequency regulation, both the flywheel energy storage array system and the constant-speed pumped storage unit participate in frequency regulation. In the inertial response phase, the constant-speed pumped storage unit employs droop control, while the flywheel energy storage array system uses a combination of inertial and droop control. In the primary frequency regulation phase, the flywheel energy storage array system gradually withdraws from frequency regulation using a first-order RC filter. At this time, the power command of the constant-speed pumped storage unit compensates for the power withdrawal of the flywheel energy storage array system based on the inertial response. The power expressions for both energy storage systems participating in frequency regulation are as follows: ; ; in, This refers to the frequency regulation power command value for a constant-speed pumped storage unit. This refers to the sag control coefficient for a constant-speed pumped storage unit. R , C These are the resistor and capacitor of a first-order RC filter, respectively.
[0012] In the preferred embodiment, in step 1, a simulation model is built in Simulink.
[0013] In the preferred embodiment, step 2 involves a simulation test under a load step disturbance condition: when the initial operating power of the constant-speed pumped storage unit is less than the rated power, the system load is set to suddenly increase at t=10s. When the initial operating power of the constant-speed pumped-storage unit is equal to its rated power, the system load is set to suddenly increase at t=10s. ,in This refers to the rated power of a constant-speed pumped storage unit. This represents the power change due to a step disturbance in the power grid load.
[0014] In a preferred embodiment, the data indicators collected during the simulation test include: the absolute value of the maximum frequency deviation during the frequency modulation process. The rise time of active power of hydropower units during primary frequency regulation Time required for the frequency to stabilize during a single frequency modulation. The power curves of constant-speed pumped storage units are compared, and the active power regulation of the constant-speed pumped storage units is read from the power curves. Overshoot of active power of constant-speed pumped storage units And the number of active power waveform oscillations n of the constant-speed pumped storage unit.
[0015] In the preferred embodiment, the simulation time of the simulation test lasts for 30 seconds after the frequency reaches stability at the end of the first frequency modulation; the criterion for determining that the frequency reaches stability at the first frequency modulation is that the frequency fluctuation amplitude is less than 0.033Hz.
[0016] In the preferred embodiment, the constraints established in step 3 include: The dynamic performance of primary frequency regulation for constant-speed pumped storage units must meet the following constraints, including: ; in: A constraint function representing the power rise time of a constant-speed pumped storage unit; A constraint function representing the frequency settling time of a single frequency modulation. A constraint function representing the power back-adjustment of a constant-speed pumped storage unit; A constraint function representing the power overshoot of a constant-speed pumped storage unit; A constraint function representing the number of oscillations in the power curve of a constant-speed pumped storage unit; A constraint function representing the maximum value of the frequency modulation deviation; This indicates the active power rise time of a constant-speed pumped storage unit. This indicates the time required for the frequency to stabilize after one frequency modulation. This indicates the reverse adjustment amount of the active power of a constant-speed pumped storage unit; This indicates the overshoot of the active power of a constant-speed pumped storage unit. This represents the total power change caused by a step disturbance in the power grid load; n is the number of oscillations in the active power waveform of the constant-speed pumped-storage unit. Set the SOC operating range constraints for the flywheel and the upper and lower limits of the power output constraints for the constant-speed pumped storage unit: ; in, Limit constraint function for flywheel charging state; upper limit constraint function for flywheel charge state; Lower limit constraint function for the power of a constant-speed pumped storage unit; Power limit constraint function for constant-speed pumped storage units; This represents the state of charge (SOC) value of a single flywheel. This indicates the minimum operating power of a constant-speed pumped storage unit. This indicates the maximum operating power of a constant-speed pumped storage unit.
[0017] In the preferred embodiment, the objective function constructed in step 3 is to minimize the number of flywheels in the flywheel energy storage array, thereby achieving the optimization objective of minimizing the capacity of the flywheel energy storage array. The expression of the objective function is: ; in, This represents the total rated power of the flywheel energy storage array; For the number of flywheels, This refers to the rated power of a single flywheel.
[0018] In the preferred embodiment, in step 3, the decision variables for optimizing the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system are the number of flywheels in the flywheel energy storage array and the grid frequency disturbance threshold.
[0019] In the preferred scheme, when optimizing the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, the number of flywheels in the flywheel energy storage array is divided into three segments: low capacity, medium capacity, and high capacity, and each segment is sampled using a different density: Low capacity: When the number of flywheels is At that time, the total capacity of the flywheel energy storage array is equal to 5% of the rated power of the constant speed pumped storage unit, and the sampling step size within this range is 1 unit; Medium capacity: When the number of flywheels is At that time, the total capacity of the flywheel energy storage array is equal to 10% of the rated power of the constant speed pumped storage unit, and the sampling step size within this range is 2 units; High capacity: When the number of flywheels is At that time, the total capacity of the flywheel energy storage array is equal to 15% of the rated power of the constant speed pumped storage unit, and the sampling step size within this range is 3 units.
[0020] In the preferred scheme, when optimizing the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, for each sampling station... Select the power grid frequency disturbance threshold The typical values were used for simulation testing. For each set of parameters, a frequency step disturbance simulation was performed once according to the method in step 2. The constraint index values obtained after each simulation were calculated and recorded.
[0021] In a preferred embodiment, the power grid frequency disturbance threshold The typical value is .
[0022] In the preferred scheme, between any two adjacent sampling numbers, for any intermediate number of sampling stations... The following linear interpolation method is used to estimate whether the constraint conditions are satisfied: Let A and B be the number of two adjacent sampling stations, and Then, its constraint index value is calculated using the following formula: ; in, For the first j The function value of the frequency modulation constraint. j =1,2,...,10, respectively corresponding to ~ ; like , , For all constraints j If all are true, then determine This is one of the feasible solutions.
[0023] In the preferred scheme, the number of flywheels... Starting with a value of 1, the number of flywheels is incremented sequentially. The constraint state for each number of flywheels is calculated through simulation or linear interpolation. The first number of flywheels that satisfies all constraints is determined to be the theoretically optimal number of flywheels. After determining the theoretically optimal number of flywheels, the power grid frequency disturbance threshold is then considered. Select the typical value with the smallest frequency difference in the corresponding simulation results from the typical values, and then take values within a range of 0.01Hz adjacent to the typical value and perform simulation again according to step 2. Select the value that minimizes the frequency difference in the simulation results as the theoretically optimal power grid frequency disturbance threshold.
[0024] The flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system and parameter optimization configuration method provided by this invention have the following beneficial effects: 1. This invention utilizes the fast response speed of flywheel energy storage arrays to assist pumped storage in grid inertial response and primary frequency regulation. The flywheel energy storage arrays independently undertake the frequency regulation task for small load disturbances, enabling fixed-speed pumped storage units to participate in frequency regulation only when grid frequency disturbances exceed the threshold. This significantly reduces the number of start-ups and shutdowns and the frequency of operation adjustments of pumped storage units, reduces mechanical wear, and effectively extends the service life of pumped storage units. At the same time, it improves the inherent defects of slow power response speed and output reversal of fixed-speed pumped storage units, and enhances the response characteristics of the overall frequency regulation system.
[0025] 2. With the minimum capacity of the flywheel energy storage array as the core optimization objective, the precise and rational configuration of flywheel energy storage is achieved by determining the theoretically optimal number of flywheels and the grid frequency disturbance threshold. This avoids the waste of construction costs caused by over-configuration of flywheel energy storage capacity. Under the premise of meeting the grid frequency regulation technical requirements, the initial construction investment of flywheel energy storage is reduced to the minimum, thereby improving the economic practicality of the energy storage system.
[0026] 3. The parameter optimization method described in this invention uses piecewise sampling combined with linear interpolation to quickly evaluate the frequency modulation effect of each flywheel array capacity. Compared with the enumeration method, it significantly reduces the number of simulations, requires no high-performance computing resources, and simplifies the optimization solution process.
[0027] The number of flywheels is divided into three segments (low, medium, and high) according to capacity, and a differentiated sampling step size is set. By combining linear interpolation to estimate the constraint conditions of the number of intermediate units, the number of simulation tests is greatly reduced compared with the traditional enumeration method. It does not rely on high-performance computing resources, simplifies the optimization solution process, reduces the operational difficulty and computational cost of parameter configuration, and improves the efficiency and feasibility of flywheel energy storage array parameter optimization.
[0028] 4. The dynamic performance constraints for primary frequency regulation of the constant-speed pumped storage unit established during the optimization process are directly derived from the requirements of relevant national standards. This ensures that the optimized system parameters and frequency regulation strategies fully comply with the technical specifications of power grid frequency regulation. The optimization results can pass the power grid frequency regulation acceptance smoothly without additional experimental verification or secondary verification, which greatly shortens the technology implementation cycle and enhances the engineering application value of the system solution. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the flywheel energy storage-constant speed pumped storage coordinated frequency regulation system proposed in this invention; Figure 2 This is a control block diagram of the frequency modulation method proposed in this invention; Figure 3 This is a schematic diagram of the parameter optimization configuration method for the flywheel energy storage-constant speed pumped storage coordinated frequency regulation system proposed in this invention; Figure 4 This is a nonlinear model of a water pump turbine; In the diagram: speed controller 10, electro-hydraulic servo system 20, water pump and turbine 30, drive shaft 1 41, drive shaft 2 42, synchronous motor 50, transformer 1 60, flywheel 70, permanent magnet synchronous motor 80, converter 1 90, DC bus 100, converter 2 110, transformer 2 120, power grid 130. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.
[0031] Example 1: This embodiment provides a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, such as Figure 1 As shown, the system includes a constant-speed pumped storage unit and a flywheel energy storage array system connected in parallel on the grid side. The constant-speed pumped storage unit includes a governor 10, an electro-hydraulic servo system 20, a pump-turbine 30, a synchronous motor 50, and a transformer 60. The governor 10, the electro-hydraulic servo system 20, and the pump-turbine 30 are electrically connected in sequence. The pump-turbine 30 is connected to the synchronous motor 50 through a drive shaft 41. The synchronous motor 50 is electrically connected to the transformer 60, so that the synchronous motor 50 is connected to the power grid 130.
[0032] The governor 10 converts the difference between the pumped-storage unit power command and the actual power into a turbine guide vane opening command. The electro-hydraulic servo system 20 adjusts the guide vane opening of the pump-turbine 30 according to the guide vane opening command. The pump-turbine 30 can control the output mechanical power by changing the guide vane opening. The drive shaft 41 connects the pump-turbine 30 to the synchronous motor 50. The synchronous motor 50 is used to realize the mutual conversion of mechanical energy and electrical energy, thereby providing or absorbing active power to the power grid to participate in the frequency regulation process.
[0033] The flywheel energy storage array system consists of several flywheel energy storage mechanisms connected in parallel. Each flywheel energy storage mechanism includes a flywheel 70, a permanent magnet synchronous motor 80, and a converter 90. The flywheel 70 is connected to the permanent magnet synchronous motor 80 through a transmission shaft 42. The converter 90 is connected to the stator winding of the permanent magnet synchronous motor 80. Each flywheel energy storage mechanism's converter 90 is connected to the same converter 110 through a DC bus 100. The converter 110 is electrically connected to a transformer 120. The transformer 120 converts the voltage on the AC side of the converter 110 into the grid voltage, enabling the converter 110 to be connected to the grid.
[0034] The flywheel 70 stores kinetic energy through rotation, and changes in its rotational speed achieve the absorption and release of kinetic energy. The permanent magnet synchronous motor 80, acting as the drive motor for the energy storage flywheel, can adjust its active power by controlling converter one 90 and converter two 110. It is connected to the flywheel via drive shaft two 42 to control the flywheel's rotational speed. Converter one is connected to the stator winding of the permanent magnet synchronous motor 80, controlling the amplitude and frequency of the stator current. Converter two rectifies the AC power from the grid side into DC power, which is then transmitted to converter one via DC bus 100. Transformer two 120 converts the voltage on the AC side of converter 110 to the grid voltage, enabling converter 110 to connect to the grid normally. In the flywheel energy storage array, multiple flywheels 70 are connected in parallel on DC bus 100.
[0035] Example 2: This embodiment provides a parameter optimization configuration method for a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, including the following steps: Step 1: Construct a simulation model of the flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system and determine the frequency regulation strategy. Specifically, build the simulation model in Simulink.
[0036] 1. The constructed simulation models include a constant-speed pumped storage unit model, a flywheel energy storage array model, and a power grid frequency response model, as detailed below: In the constant-speed pumped storage unit model, the governor model is a PI controller. The electro-hydraulic servo system is a servo motor and is represented by a first-order transfer function model. The servo motor output is the guide vane opening adjustment speed. The guide vane opening adjustment speed is integrated to obtain the guide vane opening command, which is then input to the pump turbine. Specifically, the model of the electro-hydraulic servo system is shown below: ; In the formula, K a , T a These represent the amplification factor and time constant of the servo motor speed loop, respectively, and s represents the Laplace operator, 1 / s This indicates the integration process.
[0037] The pump-turbine system is a nonlinear model. A simplified model of a typical traditional turbine speed control system is selected, such as... Figure 4 As shown, the output mechanical power is related to the guide vane opening and the power grid frequency.
[0038] In the flywheel energy storage array model, the permanent magnet synchronous motor of the flywheel adopts a dual closed-loop PI control strategy. The outer loop selects either the speed loop or the power loop according to the control target. The speed loop is selected when the grid frequency does not fluctuate or the flywheel speed is not within the specified operating range, and the power loop is selected when the flywheel participates in frequency regulation. The inner loop is the current loop.
[0039] The power grid frequency response model adopts a simplified SFR model, and its transfer function expression is as follows: ; in: Represents the power grid frequency response transfer function; Indicates the change in power grid frequency; Power variation of conventional generator sets; Power variation in a flywheel energy storage array system; This indicates the change in load power. Represents the system's inertial time constant; Represents a complex variable in the complex frequency domain; This represents the damping coefficient of the system.
[0040] 2. Frequency modulation control strategy, such as Figure 2 As shown, specifically: Set a threshold for the magnitude of power grid frequency disturbances. When the magnitude of the power grid frequency disturbance is less than At this time, the constant-speed pumped storage unit does not participate in frequency regulation; only the flywheel energy storage array system participates in grid inertial response and primary frequency regulation. The frequency regulation strategy uses a combination of inertial control and droop control, and the power command expression is as follows: ; in, This is the frequency modulation power command value for the flywheel energy storage array; For the flywheel energy storage array, is the inertial control coefficient. For the droop control coefficient of the flywheel energy storage array, This refers to the change in power grid frequency. At this time, the constant-speed pumped storage unit does not participate in frequency regulation in order to reduce the number of start-ups and shutdowns of the unit and extend the service life of the hydropower station unit.
[0041] When the magnitude of the power grid frequency disturbance is greater than During this process, both the flywheel energy storage array system and the constant-speed pumped storage unit participate in frequency regulation. In the inertial response phase, the constant-speed pumped storage unit employs droop control, while the flywheel energy storage array system uses a combination of inertial and droop control. In the primary frequency regulation phase, the flywheel energy storage array system gradually withdraws from frequency regulation using a first-order RC filter. At this time, the power command from the constant-speed pumped storage unit compensates for the power withdrawal of the flywheel energy storage array system based on the inertial response, preventing a secondary frequency drop in the grid.
[0042] The power expressions for the two types of energy storage participating in frequency regulation are as follows: ; ; in, This refers to the frequency regulation power command value for a constant-speed pumped storage unit. This refers to the sag control coefficient for a constant-speed pumped storage unit. R , C These are the resistor and capacitor of a first-order RC filter, respectively.
[0043] While performing frequency regulation using the above method, the grid frequency is continuously monitored. When the grid frequency change rate remains stable near 0 for 30 seconds, it indicates that one frequency regulation process is over. At this time, the flywheel energy storage array switches to controlling its rotation speed to keep its state of charge within a reasonable range, preparing for the next frequency regulation action.
[0044] Step 2: Obtain the effect data of the flywheel energy storage-constant speed pumped storage coordinated frequency regulation system participating in the primary frequency regulation of the power grid through simulation testing.
[0045] The simulation test is a load step disturbance simulation test: Based on the mathematical model and control strategy established in step 1, a simulation model is built in Simulink. When the initial operating power of the constant-speed pumped storage unit is less than the rated power, the system load is set to suddenly increase at t=10s. When the initial operating power of the constant-speed pumped-storage unit is equal to its rated power, the system load is set to suddenly increase at t=10s. ,in This refers to the rated power of a constant-speed pumped storage unit. This represents the power change due to a step disturbance in the power grid load.
[0046] The data collected during the simulation test included: the simulation time lasting until 30 seconds after the frequency stabilized at the end of the first frequency modulation, and recording the absolute value of the maximum frequency deviation during the frequency modulation process. The rise time of active power of hydropower units during primary frequency regulation Time required for the frequency to stabilize during a single frequency modulation. And the power curve of the hydropower unit, read the active power adjustment amount from the power curve. Overshoot And the number of oscillations, n. The criterion for determining whether the frequency has reached stability is that the frequency fluctuation amplitude is less than 0.033Hz.
[0047] Step 3: Establish constraints and optimize the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system with the minimum flywheel energy storage array capacity as the objective function. Select the theoretically optimal number of flywheels and the theoretically optimal grid frequency disturbance threshold.
[0048] like Figure 3 As shown, the specific steps include: 1. Establish an optimization model. According to the technical specifications for primary frequency regulation of hydropower generating units in the standard "Technical Regulations and Test Guidelines for Primary Frequency Regulation of Grid-Connected Power Sources" (GB / T 40595-2021), the dynamic performance of primary frequency regulation of hydropower generating units must meet the following constraints, including: ; in, A constraint function representing the power rise time of a constant-speed pumped storage unit; A constraint function representing the frequency settling time of a single frequency modulation. A constraint function representing the power back-adjustment of a constant-speed pumped storage unit; A constraint function representing the power overshoot of a constant-speed pumped storage unit; A constraint function representing the number of oscillations in the power curve of a constant-speed pumped storage unit; A constraint function representing the maximum value of the frequency modulation deviation; The rise time of active power during primary frequency regulation of a constant-speed pumped-storage unit. To achieve frequency stability during primary frequency modulation (frequency fluctuation amplitude less than 100%) The time taken for 0.033Hz This is the active power adjustment of a constant-speed pumped-storage unit. Let n be the overshoot of the active power of the constant-speed pumped-storage unit, and n be the number of oscillations in the active power waveform of the constant-speed pumped-storage unit. The inertial response and the absolute value of the maximum grid frequency deviation during primary frequency regulation.
[0049] In addition, considering the safe and stable operation of the flywheel array and the constant-speed pumped storage unit, the SOC operating range constraint of the individual flywheel and the upper and lower limits of the power output of the constant-speed pumped storage unit are set: ; in, Limit constraint function for flywheel charging state; upper limit constraint function for flywheel charge state; Lower limit constraint function for the power of a constant-speed pumped storage unit; Power limit constraint function for constant-speed pumped storage units; This represents the state of charge (SOC) value of a single flywheel. This indicates the minimum power required for the constant-speed pumped-storage unit to operate. This indicates the maximum power output of the constant-speed pumped-storage unit.
[0050] 2. Objective Function Construction. The objective function is to minimize the number of flywheels in the flywheel energy storage array, thereby achieving the optimization objective of minimizing the capacity of the flywheel energy storage array. The expression of the objective function is: ; in, This represents the total rated power of the flywheel energy storage array; For the number of flywheels, This refers to the rated power of a single flywheel.
[0051] 3. Segmented Sampling. The flywheel array unit count range is divided into the following three segments, with each segment sampled using a different density: Low capacity: ,in The total capacity of the flywheel array is equal to 5% of the rated power of the pumped storage unit. The sampling step size within this interval is 1 unit.
[0052] Medium capacity: ,in The total capacity of the flywheel array of this number of units is equal to 10% of the rated power of the pumped storage unit. The sampling step size within this interval is 2 units.
[0053] High capacity: ,in The total capacity of the flywheel array of this number of units is equal to 15% of the rated power of the pumped storage unit. The sampling step size within this interval is 3 units.
[0054] 4. Constraint Calculation: For each number of sampling stations Select Simulation tests were conducted using four typical values. For each set of parameters, a frequency step disturbance simulation was performed once using the method in step 2. The constraint index values obtained after each simulation were calculated and recorded.
[0055] Between two adjacent sampling stations, for any intermediate number of stations The following linear interpolation method is used to estimate whether the constraint conditions are satisfied: Let A and B be the number of two adjacent sampling stations, and Then, its constraint index value is calculated using the following formula: ; in, For the first j The function value of the frequency modulation constraint. j =1,2,...,10, respectively corresponding to ~ .
[0056] like , , If all constraints j are true, then determine... This is one of the feasible solutions.
[0057] 5. Obtain the optimal solution: Based on the above sampling and simulation methods, from... Starting with a value of 1, the number of flywheels is incremented sequentially. The constraint state for each individual flywheel is calculated through simulation or linear interpolation. The first flywheel number to satisfy all constraints is determined as the theoretically optimal flywheel number. .
[0058] After determining the theoretically optimal number of flywheels, among its four types... Select the typical value with the smallest frequency difference from the corresponding simulation results, and then select its adjacent values. For the 0.01Hz case, repeat step 2 for simulation, and select the value that minimizes the frequency difference in the simulation results as the theoretically optimal power grid frequency disturbance threshold. .
[0059] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, characterized in that, It includes a constant-speed pumped storage unit and a flywheel energy storage array system connected in parallel on the grid side. The constant-speed pumped storage unit includes a governor, an electro-hydraulic servo system, a water pump turbine, a synchronous motor, and a transformer. The governor, the electro-hydraulic servo system, and the water pump turbine are electrically connected in sequence. The water pump turbine is connected to the synchronous motor through a drive shaft. The synchronous motor is electrically connected to the transformer, so that the synchronous motor is connected to the power grid. The flywheel energy storage array system consists of several flywheel energy storage mechanisms connected in parallel. Each flywheel energy storage mechanism includes a flywheel, a permanent magnet synchronous motor, and a converter. The flywheel is connected to the permanent magnet synchronous motor through a transmission shaft. The converter is connected to the stator winding of the permanent magnet synchronous motor. The converter of each flywheel energy storage mechanism is connected to the same converter through a DC bus. The converter is electrically connected to a transformer. The transformer converts the voltage on the AC side of the converter to the grid voltage, so that the converter is connected to the grid.
2. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 1, characterized in that, Includes the following steps: Step 1: Construct a simulation model of the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system and determine the frequency regulation strategy; Step 2: Obtain data on the effect of the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system on the primary frequency regulation of the power grid through simulation testing; Step 3: Establish constraints and optimize the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system with the minimum capacity of the flywheel energy storage array as the objective function.
3. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 2, characterized in that, In step 1, the constructed simulation model includes a constant-speed pumped storage unit model, a flywheel energy storage array model, and a power grid frequency response model.
4. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 3, characterized in that, In the constant-speed pumped storage unit model, the speed governor model is a PI controller, the electro-hydraulic servo system is a servo motor and is represented by a first-order transfer function model. The output of the servo motor is the guide vane opening adjustment speed. The guide vane opening adjustment speed is integrated to obtain the guide vane opening command, which is then input to the pump turbine. The pump turbine is a nonlinear model, and its output mechanical power is related to the guide vane opening and the grid frequency.
5. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 3, characterized in that, In the flywheel energy storage array model, the permanent magnet synchronous motor of the flywheel adopts a dual closed-loop PI control strategy. The outer loop selects either the speed loop or the power loop according to the control target. The speed loop is selected when the grid frequency does not fluctuate or the flywheel speed is not within the specified operating range, and the power loop is selected when the flywheel participates in frequency regulation. The inner loop is the current loop.
6. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 3, characterized in that, The power grid frequency response model adopts a simplified SFR model, and its transfer function expression is as follows: ； in: Represents the power grid frequency response transfer function; Indicates the change in power grid frequency; Power variation of conventional generator sets; Power variation in a flywheel energy storage array system; This indicates the change in load power. Represents the system's inertial time constant; Represents a complex variable in the complex frequency domain; This represents the damping coefficient of the system.
7. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 2, characterized in that, The frequency modulation control strategy determined in step 1 is as follows: Set a threshold for the magnitude of power grid frequency disturbances. When the magnitude of the power grid frequency disturbance is less than At this time, the constant-speed pumped storage unit does not participate in frequency regulation; only the flywheel energy storage array system participates in grid inertial response and primary frequency regulation. The frequency regulation strategy uses a combination of inertial control and droop control, and the power command expression is as follows: ； in, This is the frequency modulation power command value for the flywheel energy storage array; For the flywheel energy storage array, is the inertial control coefficient. For the droop control coefficient of the flywheel energy storage array, This refers to the change in power grid frequency. When the magnitude of the power grid frequency disturbance is greater than During frequency regulation, both the flywheel energy storage array system and the constant-speed pumped storage unit participate in frequency regulation. In the inertial response phase, the constant-speed pumped storage unit employs droop control, while the flywheel energy storage array system uses a combination of inertial and droop control. In the primary frequency regulation phase, the flywheel energy storage array system gradually withdraws from frequency regulation using a first-order RC filter. At this time, the power command of the constant-speed pumped storage unit compensates for the power withdrawal of the flywheel energy storage array system based on the inertial response. The power expressions for both energy storage systems participating in frequency regulation are as follows: ； ； in, This refers to the frequency regulation power command value for a constant-speed pumped storage unit. This refers to the sag control coefficient for a constant-speed pumped storage unit. R , C These are the resistor and capacitor of a first-order RC filter, respectively.
8. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 2, characterized in that, In step 1, a simulation model is built in Simulink.
9. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 2, characterized in that, In step 2, the simulation test is a load step disturbance simulation test: when the initial operating power of the constant-speed pumped storage unit is less than the rated power, the system load is set to suddenly increase at t=10s. When the initial operating power of the constant-speed pumped-storage unit is equal to its rated power, the system load is set to suddenly increase at t=10s. ,in This refers to the rated power of a constant-speed pumped storage unit. This represents the power change due to a step disturbance in the power grid load.
10. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 9, characterized in that, The data metrics collected during the simulation test include: the absolute value of the maximum frequency deviation during frequency modulation. The rise time of active power of hydropower units during primary frequency regulation Time required for the frequency to stabilize during a single frequency modulation. The power curves of constant-speed pumped storage units are compared, and the active power regulation of the constant-speed pumped storage units is read from the power curves. Overshoot of active power of constant-speed pumped storage units And the number of active power waveform oscillations n of the constant-speed pumped storage unit.
11. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 10, characterized in that, The simulation test lasts for 30 seconds after the frequency reaches stability at the end of the first frequency modulation; the criterion for determining that the frequency reaches stability at the first frequency modulation is that the frequency fluctuation amplitude is less than 0.033Hz.
12. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 2, characterized in that, In step 3, the established constraints include: The dynamic performance of primary frequency regulation for constant-speed pumped storage units must meet the following constraints, including: ； in: A constraint function representing the power rise time of a constant-speed pumped storage unit; A constraint function representing the frequency settling time of a single frequency modulation. A constraint function representing the power back-adjustment of a constant-speed pumped storage unit; A constraint function representing the power overshoot of a constant-speed pumped storage unit; A constraint function representing the number of oscillations in the power curve of a constant-speed pumped storage unit; A constraint function representing the maximum value of the frequency modulation deviation; This indicates the rise time of active power during primary frequency regulation of a constant-speed pumped storage unit; This indicates the time required for the frequency to stabilize after one frequency modulation. This represents the total power change caused by a step disturbance in the power grid load; Set the SOC operating range constraints for the flywheel and the upper and lower limits of the power output constraints for the constant-speed pumped storage unit: ； in, Limit constraint function for flywheel charging state; upper limit constraint function for flywheel charge state; Lower limit constraint function for the power of a constant-speed pumped storage unit; Power limit constraint function for constant-speed pumped storage units; This represents the state of charge (SOC) value of a single flywheel. This indicates the minimum operating power of a constant-speed pumped storage unit. This indicates the maximum operating power of a constant-speed pumped storage unit.
13. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 12, characterized in that, The objective function constructed in step 3 is to minimize the number of flywheels in the flywheel energy storage array, thereby achieving the optimization objective of minimizing the capacity of the flywheel energy storage array. The expression of the objective function is: ； in, This represents the total rated power of the flywheel energy storage array; For the number of flywheels, This refers to the rated power of a single flywheel.
14. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 13, characterized in that, In step 3, the decision variables for optimizing the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system are the number of flywheels in the flywheel energy storage array and the grid frequency disturbance threshold.
15. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 14, characterized in that, When optimizing the flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, the number of flywheels in the flywheel energy storage array is divided into three segments: low capacity, medium capacity, and high capacity, and a different sampling density is used for each segment: Low capacity: When the number of flywheels is At that time, the total capacity of the flywheel energy storage array is equal to 5% of the rated power of the constant speed pumped storage unit, and the sampling step size within this range is 1 unit; Medium capacity: When the number of flywheels is At that time, the total capacity of the flywheel energy storage array is equal to 10% of the rated power of the constant speed pumped storage unit, and the sampling step size within this range is 2 units; High capacity: When the number of flywheels is At that time, the total capacity of the flywheel energy storage array is equal to 15% of the rated power of the constant speed pumped storage unit, and the sampling step size within this range is 3 units.
16. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 15, characterized in that, When optimizing a flywheel energy storage-constant-speed pumped storage coordinated frequency regulation system, for each number of sampling stations Select the power grid frequency disturbance threshold The typical values were used for simulation testing. For each set of parameters, a frequency step disturbance simulation was performed once according to the method in step 2. The constraint index values obtained after each simulation were calculated and recorded.
17. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 16, characterized in that, The power grid frequency disturbance threshold The typical value is .
18. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 16, characterized in that, Between two adjacent sampling stations, for any intermediate number of stations The following linear interpolation method is used to estimate whether the constraint conditions are satisfied: Let A and B be the number of two adjacent sampling stations, and Then, its constraint index value is calculated using the following formula: ； in, For the first j The function value of the frequency modulation constraint. j =1,2,...,10, respectively corresponding to ~ ; like , , For all constraints j If all are true, then determine This is one of the feasible solutions.
19. The parameter optimization configuration method for a flywheel energy storage-constant-speed pumped-storage coordinated frequency regulation system according to claim 18, characterized in that, From the number of flywheels Starting with a value of 1, the number of flywheels is incremented sequentially. The constraint state for each number of flywheels is calculated through simulation or linear interpolation. The first number of flywheels that satisfies all constraints is determined to be the theoretically optimal number of flywheels. After determining the theoretically optimal number of flywheels, the power grid frequency disturbance threshold is then considered. Select the typical value with the smallest frequency difference in the corresponding simulation results from the typical values, and then take values within a range of 0.01Hz adjacent to the typical value and perform simulation again according to step 2. Select the value that minimizes the frequency difference in the simulation results as the theoretically optimal power grid frequency disturbance threshold.