A frequency modulation control method for energy storage based on a segmented parameter adaptive VSG network type

Abstract

The application discloses a kind of based on segmented parameter adaptive VSG network type energy storage frequency modulation control method, belong to electric power technical field, the method includes: obtaining the operating parameter of VSG network type energy storage system, to obtain system operating parameter;Based on the VSG network type energy storage system of thermal power generating set composition, obtain thermal power generating set transfer function;Based on the VSG network type energy storage system of energy storage system composition, obtain energy storage system transfer function;Based on the thermal power generating set transfer function and the energy storage system transfer function, obtain the transfer function expression between power disturbance and system frequency;The segmented equation of the moment of inertia and damping coefficient of the VSG network type energy storage system is obtained to modulate frequency;The modulation result is verified to obtain the validity of modulation result.Solve the problem of insufficient flexibility of frequency modulation operation in power system in the prior art.

Description

Technical Field

[0001] This application belongs to the field of power technology, specifically, it relates to a frequency regulation control method for energy storage based on segmented parameter adaptive VSG network. Background Technology

[0002] VSG control features flexible and variable moment of inertia J and damping D. During primary frequency regulation in wind and energy storage systems, adaptively changing J and D helps the system frequency recover quickly after disturbances, improving system stability. Traditional VSG adaptive control typically establishes a relationship between moment of inertia J and damping coefficient D and df / dt and Δf to adaptively adjust the magnitudes of J and D. However, during primary frequency regulation in wind and energy storage systems, df / dt decreases and approaches zero when the frequency approaches its lowest or highest point, causing J and D to change prematurely. The new steady-state frequency is 50Hz lower or higher than the rated value, resulting in Δf ≠ 0. This means that J and D cannot recover to their initial values ​​J0 and D0 after adaptive adjustment, leading to system instability and exacerbating grid frequency degradation.

[0003] Therefore, how to achieve flexible control of the VSG control system is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the insufficient control flexibility of existing VSG technologies, this application discloses a segmented parameter adaptive VSG network-based energy storage frequency regulation control method, specifically:

[0005] A method for frequency regulation control of energy storage network based on piecewise parameter adaptive VSG, the method comprising:

[0006] Obtain the operating parameters of the VSG grid-type energy storage system to obtain the system operating parameters;

[0007] Based on the thermal power unit configuration of the VSG grid-type energy storage system, the transfer function of the thermal power unit is obtained.

[0008] Based on the energy storage system configuration of the VSG network-type energy storage system, the energy storage system transfer function is obtained;

[0009] Based on the transfer function of the thermal power unit and the transfer function of the energy storage system, obtain the transfer function expression between power disturbance and system frequency;

[0010] The piecewise equations for the moment of inertia and damping coefficient of the VSG grid-type energy storage system are obtained for frequency modulation.

[0011] The frequency modulation results are verified to determine their validity.

[0012] Optionally, obtaining the operating parameters of the VSG-based energy storage system to obtain system operating parameters includes:

[0013] Obtain the composition of the VSG grid-type energy storage system and the structure of the thermal power unit and energy storage system;

[0014] Based on the structure of thermal power units and energy storage systems, the equation parameters within the transfer functions of thermal power systems and energy storage systems are obtained.

[0015] Optionally, the process of obtaining the transfer function of a thermal power unit based on the VSG grid-type energy storage system includes:

[0016] Obtain the frequency regulation control type of the thermal power unit to obtain the transfer function mode;

[0017] Based on the operating parameters of the thermal power unit, the transfer function is further obtained. The transfer function of the thermal power unit is:

[0018] ,

[0019] Among them, T RH F represents the reheater time constant; HP ΔP represents the mechanical torque of a high-pressure turbine. g (s) represents the output power of the thermal power unit; Δf(s) represents the output frequency of the thermal power unit; K g G represents the frequency regulation coefficient of a thermal power unit. g (s) represents the equivalent transfer function of the thermal power unit; s represents the Laplace complex variable.

[0020] Optionally, the energy storage system configuration based on the VSG grid-type energy storage system, and the acquisition of the energy storage system transfer function, include:

[0021] Based on the energy storage system configuration of the VSG network-type energy storage system, a signal model is constructed for the energy storage system.

[0022] Based on the signal model, the transfer functions of frequency and active power of the energy storage system are obtained, and their expressions are:

[0023] ,

[0024] Among them, K b G represents the VSG frequency modulation coefficient; E =EU / Z, where U is the grid connection point voltage, E is the inverter output electromotive force, Z is the VSG output line impedance, and G is the voltage at the grid connection point. E Represents the synchronization power factor; ΔP b (s) represents the output power of the energy storage VSG response; G b (s) represents the energy storage equivalent transfer function; K bJ represents the frequency regulation coefficient of energy storage; D represents the moment of inertia; and D represents the damping coefficient. Indicates the rated angular frequency.

[0025] Optionally, obtaining the transfer function expression between power disturbance and system frequency based on the transfer function of the thermal power unit and the transfer function of the energy storage system includes:

[0026] The structure of the VSG grid-type energy storage system is obtained in order to determine the relationship between the thermal power unit and the energy storage system.

[0027] Based on the correlation, the transfer function expression between power disturbance and system frequency is obtained, which is expressed as:

[0028] ,

[0029] Wherein, ΔP L (s) represents the power disturbance; D s H represents the damping coefficient of the system. s This represents the system's inertia coefficient.

[0030] Optionally, obtaining the piecewise equations for the moment of inertia and damping coefficient of the VSG grid-type energy storage system for frequency modulation includes:

[0031] Based on the relationship between active power, moment of inertia, and damping coefficient of VSG grid-type energy storage system, piecewise equations for moment of inertia and damping coefficient are obtained.

[0032] The piecewise equation for the moment of inertia is:

[0033] ,

[0034] Where J0 represents the initial value of the moment of inertia; K J1 and K J2 The coefficient of change of moment of inertia; a represents the control exponential decay rate; b represents the initial control amplification factor; T J The threshold value for the change in moment of inertia is represented; df / dt represents the rate of change of frequency.

[0035] The piecewise equation for the damping coefficient is:

[0036] ,

[0037] Where D0 represents the initial value of the damping coefficient; K d1 and K d2 This represents the coefficient of variation of the damping coefficient; It represents the change in frequency.

[0038] Optionally, verifying the frequency modulation result to obtain the validity of the frequency modulation result includes:

[0039] The modeling and simulation of the VSG grid-type energy storage system were obtained, and the results were acquired to obtain the simulation results.

[0040] The effectiveness of frequency modulation is determined based on simulation results.

[0041] The beneficial effects of this application are that a primary frequency regulation model of a wind-storage system is established, and the influence of the virtual moment of inertia J and damping coefficient D on the system frequency response is analyzed. The results show that the values ​​of J and D directly affect the system frequency overshoot, response speed, and recovery time. Too small a value for J weakens the system's inertial support, while too large a value exacerbates frequency oscillations and prolongs the settling time. Too small a value for D easily causes power oscillations, while too large a value reduces the system response speed. Therefore, in VSG parameter adaptive control, it is necessary to reasonably adjust and limit J and D. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the embodiments of this application or the prior art will be briefly introduced below. Obviously, the following description is only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are used to provide a further understanding of this disclosure and constitute a part of the specification. They are used together with the following detailed description to explain this disclosure, but do not constitute a limitation of this disclosure. In the drawings:

[0043] Figure 1 A flowchart of a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment;

[0044] Figure 2 A block diagram of the energy storage VSG control in a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in this application embodiment;

[0045] Figure 3 This application provides a system frequency equivalent model diagram for a segmented parameter adaptive VSG network-based energy storage frequency regulation control method, as shown in the embodiments of this application.

[0046] Figure 4 A simplified equivalent model diagram of a thermal power unit in a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in this application embodiment;

[0047] Figure 5 A small-signal model diagram of a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in this application embodiment;

[0048] Figure 6 A coordinate diagram illustrating the influence of rotational inertia on the system in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment;

[0049] Figure 7 A coordinate diagram illustrating the influence of damping coefficient on the system in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment;

[0050] Figure 8 This application provides a diagram illustrating the primary frequency regulation variation curve of a system in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method, as shown in the embodiments of this application.

[0051] Figure 9 A graph showing the relationship between the absolute value of frequency deviation and the exponential factor for different values ​​of 'a' in a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in this application embodiment;

[0052] Figure 10 This is a graph showing the relationship between the absolute value of frequency deviation and the exponential factor for different b values ​​in a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in this application embodiment. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, in the embodiments of this application, "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0054] This application discloses a frequency regulation control method for energy storage based on piecewise parameter adaptive VSG network, such as... Figure 1 The diagram shown is a flowchart of a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment. Specifically:

[0055] Obtain the operating parameters of the VSG grid-type energy storage system to obtain the system operating parameters;

[0056] Based on the thermal power unit configuration of the VSG grid-type energy storage system, the transfer function of the thermal power unit is obtained.

[0057] Based on the energy storage system configuration of the VSG network-type energy storage system, the energy storage system transfer function is obtained;

[0058] Based on the transfer function of the thermal power unit and the transfer function of the energy storage system, obtain the transfer function expression between power disturbance and system frequency;

[0059] The piecewise equations for the moment of inertia and damping coefficient of the VSG grid-type energy storage system are obtained for frequency modulation.

[0060] The frequency modulation results are verified to determine their validity.

[0061] Optionally, obtaining the operating parameters of the VSG-based energy storage system to obtain system operating parameters includes:

[0062] Obtain the composition of the VSG grid-type energy storage system and the structure of the thermal power unit and energy storage system;

[0063] Based on the structure of thermal power units and energy storage systems, the equation parameters within the transfer functions of thermal power systems and energy storage systems are obtained.

[0064] Optionally, the process of obtaining the transfer function of a thermal power unit based on the VSG grid-type energy storage system includes:

[0065] Obtain the frequency regulation control type of the thermal power unit to obtain the transfer function mode;

[0066] Based on the operating parameters of the thermal power unit, the transfer function is further obtained. The transfer function of the thermal power unit is:

[0067] ,

[0068] Among them, T RH F represents the reheater time constant; HP ΔP represents the mechanical torque of a high-pressure turbine. g (s) represents the output power of the thermal power unit; Δf(s) represents the output frequency of the thermal power unit; K g G represents the frequency regulation coefficient of a thermal power unit. g (s) represents the equivalent transfer function of the thermal power unit; s represents the Laplace complex variable.

[0069] Optionally, the energy storage system configuration based on the VSG grid-type energy storage system, and the acquisition of the energy storage system transfer function, include:

[0070] Based on the energy storage system configuration of the VSG network-type energy storage system, a signal model is constructed for the energy storage system.

[0071] Based on the signal model, the transfer functions of frequency and active power of the energy storage system are obtained, and their expressions are:

[0072] ,

[0073] Among them, K b G represents the VSG frequency modulation coefficient; E =EU / Z, where U is the grid connection point voltage, E is the inverter output electromotive force, Z is the VSG output line impedance, and G is the voltage at the grid connection point. E Represents the synchronization power factor; ΔP b (s) represents the output power of the energy storage VSG response; G b (s) represents the energy storage equivalent transfer function; K b J represents the frequency regulation coefficient of energy storage; D represents the moment of inertia; and D represents the damping coefficient. Indicates the rated angular frequency.

[0074] Optionally, obtaining the transfer function expression between power disturbance and system frequency based on the transfer function of the thermal power unit and the transfer function of the energy storage system includes:

[0075] The structure of the VSG grid-type energy storage system is obtained in order to determine the relationship between the thermal power unit and the energy storage system.

[0076] Based on the correlation, the transfer function expression between power disturbance and system frequency is obtained, which is expressed as:

[0077] ,

[0078] Wherein, ΔP L (s) represents the power disturbance; D s H represents the damping coefficient of the system. s This represents the system's inertia coefficient.

[0079] Optionally, obtaining the piecewise equations for the moment of inertia and damping coefficient of the VSG grid-type energy storage system for frequency modulation includes:

[0080] Based on the relationship between active power, moment of inertia, and damping coefficient of VSG grid-type energy storage system, piecewise equations for moment of inertia and damping coefficient are obtained.

[0081] The piecewise equation for the moment of inertia is:

[0082] ,

[0083] Where J0 represents the initial value of the moment of inertia; K J1 and K J2 The coefficient of change of moment of inertia; a represents the control exponential decay rate; b represents the initial control amplification factor; T J The threshold value for the change in moment of inertia is represented; df / dt represents the rate of change of frequency.

[0084] The piecewise equation for the damping coefficient is:

[0085] ,

[0086] Where D0 represents the initial value of the damping coefficient; K d1 and K d2 This represents the coefficient of variation of the damping coefficient; It represents the change in frequency.

[0087] Optionally, verifying the frequency modulation result to obtain the validity of the frequency modulation result includes:

[0088] The modeling and simulation of the VSG grid-type energy storage system were obtained, and the results were acquired to obtain the simulation results.

[0089] The effectiveness of frequency modulation is determined based on simulation results.

[0090] To better illustrate the implementation methods described above, this application provides a detailed explanation of all the above content, specifically:

[0091] The wind-storage integrated system mainly consists of a wind power generation system, an energy storage system, loads, and a thermal power-synchronous generator. The wind power generation system employs maximum power point tracking (MPPT) control, continuously outputting a rated active power of 100MW to the system. The energy storage system has a capacity of 20MW / 40MWh and adopts a grid-type VSG control strategy. When power disturbances occur in the system, the energy storage can quickly absorb surplus power on the bus side or compensate for power deficits on the bus side, thereby participating in system frequency regulation. The load is connected to the 220kV thermal power-synchronous generator side, with a maximum power disturbance amplitude of ±20MW. To simulate the primary frequency regulation characteristics of thermal power units, a synchronous generator equivalent to a traditional thermal power unit is used, with its rated capacity set at 300MW.

[0092] The VSG control structure of the energy storage converter is as follows Figure 2 The diagram shown is a block diagram of the energy storage VSG control in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment. The outer loop employs active-frequency droop control and reactive-voltage droop control to generate voltage phase angle and voltage amplitude signals, respectively. The virtual moment of inertia J and damping coefficient D can be adaptively adjusted according to the system operating state. The inner loop uses voltage and current dual closed-loop decoupled control, and ultimately generates a drive signal through an SVPWM signal generator to control the energy storage converter.

[0093] II. System Frequency Equivalent Model

[0094] The system frequency equivalent model is shown in Figure 3, which is the system frequency equivalent model diagram in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment:

[0095] G in the diagram g (s) is the equivalent transfer function of the thermal power unit, G b (s) is the energy storage equivalent transfer function. ΔP L (s) represents the load disturbance, ΔP g (s) represents the output power of the thermal power unit, ΔP b (s) represents the output power of the energy storage VSG response; K g K is the frequency regulation coefficient of the thermal power unit. b H represents the frequency regulation coefficient for energy storage. s D s These are the system inertia and the system damping coefficient, respectively.

[0096] The primary frequency regulation response of a thermal power unit is mainly affected by the governor, turbine, and reheater. Among these, the reheater dynamics alter the unit's active power response, making it a crucial factor influencing the frequency regulation response speed. To facilitate system frequency dynamic analysis, while maintaining model simplicity and considering key dynamic characteristics, this application reduces the thermal power unit's frequency regulation response to a simplified model consisting of a governor gain and a reheat turbine connected in series, as shown below. Figure 4 The figure shown is a simplified equivalent model diagram of a thermal power unit in a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in an embodiment of this application.

[0097] The frequency regulation control of thermal power units is proportional control, and its transfer function expression is as follows:

[0098] (1)

[0099] In the formula, T RH F is the reheater time constant, typically taken as 7.0 s; HP This represents the mechanical torque of the high-pressure turbine, typically taken as 0.3.

[0100] The energy storage system employs virtual synchronous machine control, constructing its small-signal model, such as... Figure 5 The diagram shown is a small-signal model of a VSG-based frequency regulation control method for energy storage network based on piecewise parameter adaptive VSG, provided in an embodiment of this application.

[0101] Based on the small-signal model, the transfer function expressions for frequency and active power can be obtained:

[0102] (2)

[0103] In the formula, K b G is the VSG frequency modulation coefficient; E =EU / Z, where U is the grid connection point voltage, E is the inverter output electromotive force, and Z is the VSG output line impedance.

[0104] Combining equations (1) and (2) and substituting them into the system block diagram, the power disturbance ΔP can be obtained. L The transfer function expression between the system frequency f and the system frequency f is:

[0105] (3)

[0106] With a damping coefficient D=600, and taking moments of inertia J=0.01, 5, 10, 15, and 20 respectively, the system frequency response curves for different J values ​​are obtained, as follows. Figure 6 The figure shows the influence of rotational inertia on the system in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment. As can be seen from the figure, when the damping coefficient D remains constant, as the rotational inertia J increases, the overshoot and oscillation amplitude of the system frequency response gradually increase, and the settling time also prolongs. Therefore, the upper limit of J should not be too large. This application sets the upper limit of J to 5 to provide certain inertial support during the frequency recovery phase, while avoiding secondary oscillations and prolonged settling time during the recovery process caused by an excessively large J value. On the other hand, J needs to be reduced during the frequency deviation phase to reduce the inertial lag in the initial stage of disturbance, allowing the energy storage to participate in power regulation more quickly. However, J cannot be too small either; otherwise, the equivalent inertia will be too low, easily causing the VSG output power to change too quickly, reducing the stability of system operation. Therefore, the lower limit of J is set to 0.05, so that it can improve the response speed in the initial stage of disturbance while avoiding the instability risk caused by excessively low inertia.

[0107] With the moment of inertia J=1, and damping coefficients D=250, 500, 1000, 1500, 3000, and 4000 respectively, the system frequency response curves for different values ​​of D are obtained, as follows. Figure 7 The figure shows the influence of the damping coefficient on the system in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment. As can be seen from the figure, for the damping coefficient D, parameter analysis shows that while increasing D can enhance the damping effect, it will reduce the system's frequency response speed, slowing down the frequency recovery process; conversely, too small a D will weaken the VSG's ability to suppress power oscillations, easily causing output power oscillations in the energy storage converter. Therefore, this application sets the lower limit of D to 250, enabling the system to improve the active power response speed with smaller damping during frequency deviation phases, while retaining necessary damping support; setting the upper limit of D to 1000 is to prevent excessive damping from causing slow system response and prolonged adjustment time.

[0108] The system frequency primary frequency modulation change curve is as follows: Figure 8The figure shown is a curve of the primary frequency regulation of the system in a segmented parameter adaptive VSG network-type energy storage frequency regulation control method provided in an embodiment of this application. The primary frequency regulation is divided into two processes: frequency deviation and frequency recovery. Interval ① is the system frequency deviation process, and interval ② is the system frequency recovery process.

[0109] When a power system's active power balance is disrupted by a sudden load change, the system frequency will change significantly. At the instant the disturbance occurs, the frequency deviates sharply due to the supporting effect of rotational inertia. At this point, the power deficit is buffered primarily by the system's inertial response and the primary frequency regulation intervention of energy storage. In this situation, the moment of inertia J and damping coefficient D should be reduced to decrease the frequency overshoot and accelerate the power output of the energy storage system to quickly compensate for the power deficit. However, in the initial stage of frequency deviation, Δf has just begun to change and is therefore very small. Using only a linear transformation K|Δf| would result in slow changes in J and D, leading to an insufficiently proactive energy storage response. Therefore, an exponential adjustment factor is introduced. This enhances the sensitivity of parameters to small frequency deviations. When the system frequency first deviates from its rated value, a larger exponent value amplifies the adjustment effect of the frequency deviation on J and D, enabling the energy storage system to quickly participate in active power support and suppress further frequency deviation. After the power deficit is compensated, the system frequency begins to show an inflection point, the deviation rate slows significantly, and the frequency enters a slow recovery phase. Eventually, the system reaches a new power balance point, but the stable frequency value will be lower than the rated frequency and will remain at that level. At this point, the moment of inertia J and damping coefficient D should be appropriately increased to accelerate the frequency recovery process.

[0110] (4) (5)

[0111] In the formula, J0 and D0 are the initial values ​​of J and D, where J0=1 and D0=600. df / dt is the derivative of the system frequency, and T... J T D Let T be the threshold values ​​for the changes in J and D, respectively. When df / dt is less than the threshold value, the system frequency can be considered to have reached steady state, where T is the threshold value. J =0.2、T D =0.2. K J1 K J2 K d1 K d2 K represents the coefficients of change in J and D, which determine the rate of change of J and D. J1 =3、K J2 =10、K d1 =800, K d2 =200. a and b are exponential enhancement parameters, where a controls the exponential decay rate; a larger a indicates a shorter initial amplification time, such as... Figure 9The diagram shown illustrates the relationship between the absolute value of frequency deviation and the exponential factor for different values ​​of 'a' in a segmented parameter adaptive VSG network-based energy storage frequency regulation control method provided in this application embodiment; 'b' represents the initial control amplification factor, with larger 'b' indicating more drastic initial changes, such as... Figure 10 The figure shown is a graph showing the relationship between the absolute value of frequency deviation and the exponential factor for different b values ​​in a segmented parameter adaptive VSG network energy storage frequency regulation control method provided in this application embodiment. In this application, a=15 and b=20 are used.

[0112] (1) When When the system frequency deviates from its stable point, it indicates that the system frequency has begun to shift. At this point, J should be decreased to reduce the system frequency overshoot. Similarly, when... When the system frequency reaches a stable point, it indicates that the system frequency is approaching a stable point and is beginning to recover. At this time, J should be increased to make the system frequency stabilize faster.

[0113] (2) When When the system frequency is considered to be in a stable state, D is initially set to D0. When the system frequency is considered to be deviating, it is necessary to quickly compensate for the power deficit to restore the system frequency to stability. In this case, D should be decreased to allow the VSG to output power quickly. At that time, appropriately increasing D will speed up the recovery time for the system frequency to reach a new steady state.

[0114] To verify the effectiveness of the proposed algorithm, a simulation model of the wind-storage system was built in MATLAB / Simulink software, and simulation verification was performed. Four operating conditions were set up: a sudden load increase of 20MW, a sudden load decrease of 20MW, a sudden wind speed increase of 0.5m / s, and a sudden wind speed decrease of 0.5m / s. The system frequency response curves and the changes in J and D of the existing VSG adaptive control technology and the improved piecewise parameter adaptive VSG control proposed in this application were observed.

[0115] To better illustrate the beneficial effects of this application, the specific implementation uses Chinese Patent CN120433254A, "A VSG Frequency Regulation Control Method for Grid-type Energy Storage in a Wind Storage System," as a reference. First, based on this patent, the grid-type frequency regulation results under conditions of sudden load reduction, sudden load increase, sudden wind speed reduction, and sudden wind speed increase are analyzed. Then, under the same conditions of sudden load reduction, sudden load increase, sudden wind speed reduction, and sudden wind speed increase, the grid-type frequency regulation results of this application are compared. The results are as follows:

[0116] (1) Under the condition of sudden load reduction, the system load suddenly decreases by 20MW at 0.7s, and the system input power is greater than the load consumption power, so the system frequency begins to rise. When using the existing VSG adaptive control method, the maximum system frequency is 50.16Hz, the time to reach the highest point is 0.103s, and the time to reach the new steady state is 0.28s. As can be seen from the frequency response curve, although the adaptive method used in the existing technology can adjust J and D according to the frequency change, when the frequency is close to the highest point, the rate of frequency change gradually decreases, which makes it easy for the controller to judge that the system has entered a steady state in advance, resulting in the premature recovery of J and D parameters, thereby weakening the suppression effect of frequency rise overshoot in the early stage of disturbance.

[0117] After adopting the technical solution of this application, the maximum system frequency is 50.158Hz, the time to reach the highest point is 0.112s, and the time to reach the new steady state is also 0.112s. The control strategy further divides the frequency change process into a frequency deviation stage and a frequency recovery stage. In the frequency deviation stage, the improved method can quickly reduce the moment of inertia J and damping coefficient D according to the frequency deviation, enabling the energy storage system to absorb the surplus power in the system more quickly and suppressing the frequency from continuing to rise. In the frequency recovery stage, J and D are readjusted according to the frequency change rate. Increasing J is beneficial to improving the stability of the recovery stage, and appropriately increasing D can enhance the damping effect and suppress the secondary overshoot and oscillation during the recovery process. Therefore, compared with the existing VSG adaptive control method, the piecewise adaptive method can reduce the maximum frequency value when the load suddenly decreases, shorten the time for the frequency to reach the extreme point, and enable the system to enter a new stable operating state more smoothly.

[0118] (2) Under the condition of sudden load increase, the system load suddenly increases by 20MW at 0.7s, the load power demand increases, the system has an active power deficit, resulting in a drop in system frequency. When using the existing VSG adaptive control method, the lowest system frequency is 49.833Hz, the time to reach the lowest point is 0.108s, and the time to reach the new steady state is 0.16s. As can be seen from the frequency response curve in the figure, the adaptive method used in the existing technology can adjust J and D after the disturbance occurs. However, since the parameter changes are mainly affected by the frequency change rate, when the frequency drops to near the lowest point, df / dt is close to zero, which can easily cause J and D to recover prematurely, weakening the energy storage support capacity when the frequency is still at a large deviation, thus leading to a lower lowest frequency and an unstable recovery process.

[0119] After adopting the technical solution of this application, the lowest system frequency is 49.84Hz, the time to reach the lowest point is 0.102s, and the time to reach the new steady state is 0.148s. During the frequency drop deviation phase, the controller rapidly reduces J and D according to the frequency deviation. The reduction of J can reduce the equivalent inertial lag in the early stage of the disturbance, allowing the energy storage to release active power more quickly; the reduction of D can improve the active power response speed of the VSG and accelerate the power deficit compensation. After the frequency enters the recovery phase, J and D no longer recover prematurely because df / dt is close to zero, but are adjusted in segments according to the frequency recovery trend, making the parameter changes more matched with the frequency dynamic process. As can be seen from the figure, the segmented adaptive method can raise the lowest frequency point, shorten the time to reach the lowest frequency point, and reduce the oscillation in the recovery phase. Therefore, this method can more effectively suppress frequency drop overshoot under load surge conditions and improve the speed and stability of the system's primary frequency regulation.

[0120] (3) Under the condition of sudden wind speed reduction, at 0.7s, the system wind speed suddenly drops from 12 m / s to 11.5 m / s, the wind power output decreases, the system input power decreases, and the system frequency drops. When using the existing VSG adaptive control method, the lowest system frequency is 49.925 Hz, the time to reach the lowest point is 0.105s, and the time to reach the new steady state is 0.16s. As can be seen from the figure, the adaptive method used in the existing technology can adjust J and D in the early stage of disturbance, but when the frequency drops to near the lowest point, due to the decrease in the rate of frequency change, the parameters are prone to premature rebound, resulting in insufficient support effect at the lowest frequency point, and the system recovery process is also prone to a certain lag.

[0121] After adopting the technical solution of this application, the lowest system frequency is 49.929Hz, the time to reach the lowest point is 0.103s, and the time to reach the new steady state is 0.14s. The controller can quickly identify the frequency deviation state when the frequency drops due to a sudden decrease in wind speed, and promptly reduce J and D, enabling the energy storage system to quickly compensate for the power deficit. After entering the frequency recovery stage, the improved method adjusts J and D according to the frequency change rate, avoiding the problem of misjudging the steady state near the frequency extreme point in the existing VSG adaptive control method. As can be seen from the image results, the piecewise adaptive method raises the lowest frequency point and shortens the time to reach the lowest frequency point, indicating that it can effectively improve the frequency drop problem under the condition of sudden wind speed reduction and improve the support capability of the wind storage system to the disturbance of wind power reduction.

[0122] (4) Under the condition of sudden wind speed increase, at 0.7s, the system wind speed suddenly increases from 12m / s to 12.5m / s. The output power of wind power generation increases with the increase of wind speed, resulting in excess active power in the system and causing the system frequency to rise, which is similar to the frequency change trend under the condition of sudden load reduction. When using the existing VSG adaptive control method, the highest value of the system frequency reaches 50.138Hz, the time required to reach the highest point is 0.148s, and the time to reach the new steady state is 0.23s. It can be seen from the frequency response curve that although the adaptive method used in the existing technology can adjust J and D with the frequency change, when the frequency is close to the highest point, df / dt decreases and approaches zero, which easily causes the parameters to recover prematurely, resulting in insufficient suppression effect of the system on frequency rise overshoot. At the same time, since the steady state frequency after the first frequency adjustment may not return to the rated value, the existing VSG adaptive control method may also have the problem that the parameters are difficult to fully recover to the initial value.

[0123] After adopting the technical solution of this application, the system frequency reached a maximum of 50.128Hz, with a time of 0.138s to reach the maximum and a time to reach a new steady state of 0.21s. During the frequency rise deviation phase, the controller rapidly reduces J and D according to the frequency deviation, enabling the energy storage VSG to absorb the excess power brought by the sudden increase in wind speed more quickly, thereby suppressing further frequency rise. During the frequency recovery phase, the improved method readjusts the parameters according to the frequency change rate, ensuring that the changes in J and D correspond to the frequency recovery process, avoiding the problem of premature parameter recovery near the frequency extreme point. As can be seen from the figure, the system frequency peak value is lower under the piecewise adaptive method, the time to reach the peak is shortened, and the change process of J and D is more in line with the actual needs of the frequency deviation and recovery phases. Therefore, under the condition of sudden wind speed increase, the piecewise adaptive method can effectively reduce frequency rise overshoot and improve the system's response speed and stability to disturbances caused by rapid increases in wind power.

[0124] Table 1. Comparison of frequency response of the two adaptive methods under four operating conditions.

[0125]

[0126] A comprehensive analysis of the four operating conditions reveals that while existing VSG adaptive control methods can improve system frequency response to some extent, their parameter adjustments are susceptible to the influence of the zero-crossing point of the frequency change rate. This can lead to premature recovery of J and D parameters when the frequency approaches its highest or lowest point, resulting in a mismatch between parameter changes and the actual frequency dynamics. The method presented in this application distinguishes between the frequency deviation phase and the frequency recovery phase, making the adjustment logic of J and D clearer: during the frequency deviation phase, it rapidly enhances the energy storage power response to suppress further frequency deviation; during the frequency recovery phase, it readjusts J and D to reduce secondary overshoot and oscillations, allowing the system to more smoothly enter a new stable state. Therefore, compared to existing VSG adaptive control methods, the improved adaptive method better reduces frequency overshoot, shortens dynamic response time, and improves the stability of the primary frequency regulation process of the wind-storage system under both load and wind speed disturbances.

[0127] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to computer program instructions. The aforementioned computer program can be stored in a non-volatile storage medium, and when executed, it performs the steps of the above method embodiments. Alternatively, if the integrated unit of the present invention is implemented as a software functional module and sold or used as an independent product, it can also be stored in a non-volatile storage medium. Based on this understanding, the technical solution of the embodiments of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a non-volatile storage medium and includes several instructions to cause an electronic device (which may be a personal computer, server, network device, etc.) to execute all or part of the methods described in the various embodiments of the present invention.

[0128] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A frequency regulation control method for energy storage based on piecewise parameter adaptive VSG network, characterized in that, The method includes: Obtain the operating parameters of the VSG grid-type energy storage system to obtain the system operating parameters; Based on the thermal power unit configuration of the VSG grid-type energy storage system, the transfer function of the thermal power unit is obtained. Based on the energy storage system configuration of the VSG network-type energy storage system, the energy storage system transfer function is obtained; Based on the transfer function of the thermal power unit and the transfer function of the energy storage system, obtain the transfer function expression between power disturbance and system frequency; The piecewise equations for the moment of inertia and damping coefficient of the VSG grid-type energy storage system are obtained for frequency modulation. The frequency modulation results are verified to determine their validity. The thermal power unit configuration based on the VSG grid-type energy storage system, and the acquisition of the thermal power unit transfer function, include: Obtain the frequency regulation control type of the thermal power unit to obtain the transfer function mode; Based on the operating parameters of the thermal power unit, the transfer function is further obtained. The transfer function of the thermal power unit is: ， Among them, T RH F represents the reheater time constant; HP ΔP represents the mechanical torque of a high-pressure turbine. g (s) represents the output power of the thermal power unit; Δf(s) represents the output frequency of the thermal power unit; K g G represents the frequency regulation coefficient of a thermal power unit. g (s) represents the equivalent transfer function of the thermal power unit; s represents the Laplace complex variable; The step of obtaining the piecewise equations for the moment of inertia and damping coefficient of the VSG grid-type energy storage system for frequency modulation includes: Based on the relationship between active power, moment of inertia, and damping coefficient of VSG grid-type energy storage system, piecewise equations for moment of inertia and damping coefficient are obtained. The piecewise equation for the moment of inertia is: ， Where J0 represents the initial value of the moment of inertia; K J1 and K J2 The coefficient of change of moment of inertia; a represents the control exponential decay rate; b represents the initial control amplification factor; T J The threshold value for the change in moment of inertia is represented; df / dt represents the rate of change of frequency. The piecewise equation for the damping coefficient is: ， Where D0 represents the initial value of the damping coefficient; K d1 and K d2 This represents the coefficient of variation of the damping coefficient; Indicates the change in frequency; T D The threshold representing the change in damping coefficient 2. The frequency regulation control method for energy storage based on piecewise parameter adaptive VSG network as described in claim 1, characterized in that, The process of obtaining the operating parameters of the VSG-based energy storage system to obtain system operating parameters includes: Obtain the composition of the VSG grid-type energy storage system and the structure of the thermal power unit and energy storage system; Based on the structure of thermal power units and energy storage systems, the equation parameters within the transfer functions of thermal power systems and energy storage systems are obtained.

3. The frequency regulation control method for energy storage based on piecewise parameter adaptive VSG network as described in claim 1, characterized in that, The energy storage system configuration based on the VSG network-type energy storage system, and the acquisition of the energy storage system transfer function, include: Based on the energy storage system configuration of the VSG network-type energy storage system, a signal model is constructed for the energy storage system. Based on the signal model, the transfer functions of frequency and active power of the energy storage system are obtained, and their expressions are: ， Among them, K b G represents the VSG frequency modulation coefficient; E =EU / Z, where U is the grid connection point voltage, E is the inverter output electromotive force, Z is the VSG output line impedance, and G is the voltage at the grid connection point. E Represents the synchronization power factor; ΔP b (s) represents the output power of the energy storage VSG response; G b (s) represents the energy storage equivalent transfer function; K b J represents the frequency regulation coefficient of energy storage; D represents the moment of inertia; and D represents the damping coefficient. Indicates the rated angular frequency.

4. The frequency regulation control method for energy storage based on piecewise parameter adaptive VSG network as described in claim 1, characterized in that, The step of obtaining the transfer function expression between power disturbance and system frequency based on the transfer function of the thermal power unit and the transfer function of the energy storage system includes: The structure of the VSG grid-type energy storage system is obtained in order to determine the relationship between the thermal power unit and the energy storage system. Based on the correlation, the transfer function expression between power disturbance and system frequency is obtained, which is expressed as: ， Where, ΔP L (s) represents the power disturbance; D s H represents the damping coefficient of the system. s This represents the system's inertia coefficient.

5. The frequency regulation control method for energy storage based on piecewise parameter adaptive VSG network as described in claim 1, characterized in that, The verification of the frequency modulation results to obtain the validity of the frequency modulation results includes: The modeling and simulation of the VSG grid-type energy storage system were obtained, and the results were acquired to obtain the simulation results. The effectiveness of frequency modulation is determined by obtaining simulation results.

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