VSG secondary frequency modulation control method and system based on segmented integral coefficient

Abstract

The invention belongs to the technical field of secondary frequency modulation control of a virtual synchronous generator, discloses a VSG secondary frequency modulation control method and system based on segmented integral coefficients, and proposes that values of the frequency integral coefficients are determined based on frequency offset segments, two fixed integral coefficients are respectively determined, and when the frequency offset is lower than a threshold value, the VSG secondary frequency modulation control method and system based on the segmented integral coefficients are started. When the frequency deviation is higher than the threshold value, the value of the integral coefficient is small, and when the frequency deviation is higher than the threshold value. According to the control method provided by the invention, the frequency maximum offset is reduced, the adjustment times of the frequency integral coefficient are reduced, and the performance of dynamic frequency adjustment of the virtual synchronous generator and the stability of the system are improved; the integral coefficient is set in a segmented manner, so that the frequency offset is reduced, and the dynamic adjustment time of the frequency is shortened. According to the control method provided by the invention, the integral coefficient is only changed twice in the dynamic adjustment process, so that the change frequency of the integral coefficient is reduced, and the stability of frequency change in the dynamic process is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary frequency modulation control of virtual synchronous generators, and in particular relates to a VSG secondary frequency modulation control method and system based on a piecewise integral coefficient. Background Art

[0002] With the increasing installed capacity and proportion of renewable energy, the degree of power electronics in power systems is constantly improving. For new power electronics power systems, a series of new control strategies are constantly proposed. In view of the low inertia and low damping characteristics of power electronic equipment, virtual synchronous generator (VSG) control technology came into being.

[0003] According to the regulation characteristics of VSG output frequency, VSG parameter adaptive control can be divided into two types: primary frequency regulation control and secondary frequency regulation control. Primary frequency regulation is a differential regulation, and the frequency cannot return to the initial value when it is finally stable. Secondary frequency regulation compensates for the frequency deviation, and the frequency deviation is zero in steady state. When VSG is off-grid, if the system suddenly switches to heavy load, the system frequency is likely to fall out of the safe range of frequency. Therefore, under off-grid conditions, secondary frequency regulation control of VSG can improve the safety and reliability of the power system.

[0004] The traditional control method of fixed parameter values ​​cannot solve the contradiction between system adjustment time and frequency oscillation. Although the improved integral coefficient adaptive control can improve the frequency regulation performance, too frequent adjustment of the integral coefficient will lead to greater frequency fluctuations during the frequency regulation process.

[0005] In the "Secondary Frequency Regulation Scheme of Microgrid Inverter Based on Improved Virtual Synchronous Generator Algorithm", Li Bin [1] adopted a fixed integral coefficient and determined the value of the integral coefficient according to the VSG power ratio. The value of the integral coefficient of each VSG is a fixed value. In the "Research on VSG Control Strategy of Microgrid Inverter Based on Integral Compensation", Zhu Zuobin [2] adopted a fixed integral coefficient to achieve secondary regulation of VSG frequency.

[0006] The defects of the prior art are that the integral coefficient is fixed, and the contradiction between the frequency adjustment time and the overshoot cannot be resolved. Only the function of secondary frequency adjustment is realized, and the adjustment performance is not improved.

[0007] Through the above analysis, the problems and defects of the prior art are as follows:

[0008] (1) The traditional control method of fixed parameter values ​​cannot solve the contradiction between system adjustment time and frequency oscillation. Although the improved integral coefficient adaptive control can improve the frequency regulation performance, too frequent adjustment of the integral coefficient will lead to greater frequency fluctuations during the frequency regulation process.

[0009] (2) The integral coefficient is set to a fixed value, which cannot solve the contradiction between the frequency adjustment time and overshoot. It only realizes the function of secondary frequency adjustment, and does not improve the adjustment performance. Summary of the invention

[0010] In view of the problems existing in the prior art, the present invention provides a VSG secondary frequency modulation control method based on segmented integral coefficients.

[0011] The present invention is implemented in this way: a VSG secondary frequency modulation control method based on a segmented integral coefficient comprises:

[0012] Step 1, design the VSG secondary frequency modulation structure;

[0013] Step 2: Design a segmented secondary frequency modulation control strategy.

[0014] Further, the method for designing the VSG secondary frequency modulation structure is as follows:

[0015] (1) Design the VSG primary frequency modulation control block diagram;

[0016] According to the VSG active frequency control equation:

[0017]

[0018] The active frequency control block diagram can be obtained;

[0019] (2) Design the VSG secondary frequency modulation control block diagram;

[0020] Add an integral link to the active frequency control equation:

[0021]

[0022] The frequency secondary regulation control block diagram can be obtained.

[0023] Furthermore, the method for designing a segmented secondary frequency modulation control strategy is as follows:

[0024] 1) Calculate the value range of the frequency integral coefficient:

[0025] The frequency integral coefficient is set to correspond to the damping ratio of the second-order system in the range of 0.1 to 0.3. The integral coefficient k satisfies the following conditions:

[0026]

[0027] According to the values ​​of Kp, D, and J, the value range of the integral coefficient k is determined as follows:

[0028]

[0029] 2) Method for determining segmented secondary frequency modulation:

[0030] In the value range of the integral coefficient k, the values ​​k1 and k2 are taken respectively, and the segmented control strategy is designed as follows:

[0031]

[0032] The value of ε is determined according to the variation range of the frequency offset.

[0033] Control block diagram of segmented secondary frequency modulation.

[0034] Another object of the present invention is to provide a VSG secondary frequency modulation control system based on a piecewise integral coefficient that implements the above-mentioned VSG secondary frequency modulation control method based on a piecewise integral coefficient, comprising:

[0035] VSG primary frequency modulation control module is used to design the VSG primary frequency modulation control block diagram, and obtain the active frequency control block diagram according to the VSG active frequency control equation;

[0036] The VSG secondary frequency regulation control module is used to add an integral link to the active frequency control equation to obtain a frequency secondary regulation control block diagram;

[0037] The segmented integral coefficient calculation module is used to calculate the value range of the frequency integral coefficient, set the frequency integral coefficient to correspond to the damping ratio in the range of 0.1 to 0.3 of the second-order system, and determine the value range of the integral coefficient k;

[0038] The segmented control strategy design module is used to respectively select values ​​k1 and k2 within the value range of the integral coefficient k, determine the value according to the variation range of the frequency offset, and design the control strategy of segmented secondary frequency modulation.

[0039] Further, the VSG primary frequency modulation control module includes:

[0040] According to the active frequency control equation:

[0041]

[0042] Designed active frequency control block diagram;

[0043] The VSG secondary frequency modulation control module adds an integral link to the active frequency control equation:

[0044]

[0045] Designed frequency secondary regulation control block diagram.

[0046] Furthermore, the segmented control strategy design module includes:

[0047] Calculate the value range of the frequency integral coefficient k, and determine the value range of the integral coefficient k according to the values ​​of Kp, D, and J:

[0048]

[0049] In the value range of the integral coefficient k, the values ​​k1 and k2 are taken respectively, and the designed segmented control strategy is as follows:

[0050]

[0051] The value of ε is determined according to the variation range of the frequency offset.

[0052] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0053] First, the present invention proposes to determine the value of the frequency integral coefficient based on the frequency offset segment, and determine two fixed integral coefficients respectively. When the frequency deviation is lower than the threshold, the integral coefficient takes a small value, and when the frequency deviation is higher than the threshold, the integral coefficient takes a large value. The control method proposed in this application reduces the maximum frequency offset while reducing the number of adjustments of the frequency integral coefficient, thereby improving the performance of dynamic frequency regulation of the virtual synchronous generator and the stability of the system.

[0054] By setting the integral coefficient in segments, not only the frequency offset is reduced, but also the dynamic adjustment time of the frequency is shortened. Compared with other parameter adaptive control methods, the proposed control method only changes the integral coefficient twice during the dynamic adjustment process, which greatly reduces the number of changes of the integral coefficient and improves the stability of the frequency change during the dynamic process.

[0055] 1) Reduce the frequency offset and the dynamic frequency adjustment time.

[0056] 2) The number of times the integral coefficient is adjusted is reduced, and the stability of the system is improved.

[0057] The present invention proposes a segmented control strategy for determining the value of the integral coefficient based on the frequency offset. The dynamic adjustment of the frequency is divided into two longitudinal parts, namely, the part where the frequency offset is lower than the threshold and the part where the frequency offset is higher than the threshold. For the part where the frequency offset is higher than the threshold, a larger integral coefficient is used to improve the dynamic performance of the frequency response. For the part where the frequency offset is lower than the threshold, a smaller integral coefficient is used to reduce the overshoot in the steady state.

[0058] Second, the present invention solves the problems of slow response speed and low regulation accuracy in the VSG secondary frequency modulation control method in the prior art. In the frequency regulation process, the traditional VSG control method is often difficult to respond quickly to load changes, resulting in large frequency offset and reduced system stability. Especially when there is a large load fluctuation, the existing control strategy is difficult to ensure that the dynamic performance and steady-state performance of the system are met at the same time. Therefore, there is an urgent need for a VSG secondary frequency modulation control method that can improve the response speed and regulation accuracy.

[0059] The present invention significantly improves the response speed and regulation accuracy of the system by designing a secondary frequency modulation control strategy of a segmented integral coefficient. The segmented integral coefficient control strategy selects a suitable integral coefficient according to the frequency offset, and can respond quickly to large load changes and reduce frequency offset. At the same time, by accurately calculating the value range of the frequency integral coefficient, it is ensured that the system can maintain a high regulation accuracy under various working conditions, thereby effectively improving the stability of the system.

[0060] In addition, the segmented control strategy adopted by the present invention can be adaptively adjusted and the integral coefficient can be adjusted in real time according to the load changes, overcoming the problem that the fixed integral coefficient in the traditional method cannot take into account both dynamic performance and steady-state performance. The segmented control strategy not only improves the flexibility of frequency regulation, but also provides the best control effect under different load conditions, significantly improving the overall performance of the system.

[0061] In summary, the present invention has achieved significant technical progress while solving the problems of the prior art. By optimizing the VSG secondary frequency modulation control structure and strategy, the present invention not only improves the response speed and regulation accuracy of the system, but also enhances the stability and adaptability of the system, providing strong support for the promotion of VSG technology in practical applications.

[0062] Third, whether the technical solution of the present invention solves the technical problem that people have always been eager to solve but have never succeeded in solving: it solves the problem that the fixed integral coefficient in the traditional method cannot take into account both dynamic performance and steady-state performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a flow chart of a VSG secondary frequency modulation control method based on a piecewise integral coefficient provided in an embodiment of the present invention.

[0064] Figure 2 It is a structural block diagram of a VSG secondary frequency modulation control system based on a piecewise integral coefficient provided in an embodiment of the present invention.

[0065] Figure 3 It is a detailed structural block diagram of a VSG secondary frequency modulation control system based on a piecewise integral coefficient provided in an embodiment of the present invention.

[0066] Figure 4 This is an active frequency control block diagram provided by an embodiment of the present invention.

[0067] Figure 5 It is a frequency secondary adjustment control block diagram provided by an embodiment of the present invention.

[0068] Figure 6 It is a control block diagram of the segmented secondary frequency modulation provided by an embodiment of the present invention.

[0069] Figure 7 It is a schematic diagram of segmented secondary frequency modulation provided by an embodiment of the present invention.

[0070] Figure 8 It is a simulation effect diagram provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0072] like Figure 1 As shown, a VSG secondary frequency modulation control method based on a piecewise integral coefficient provided by an embodiment of the present invention comprises the following steps:

[0073] S101, design VSG secondary frequency modulation structure;

[0074] S102, design a segmented secondary frequency modulation control strategy.

[0075] The detailed working principle of the embodiment of the present invention.

[0076] 1. Primary frequency modulation control design:

[0077] The primary frequency control mainly stabilizes the frequency by adjusting the output power. The control block diagram is based on the active frequency control equation and achieves the initial stabilization of the frequency by adjusting the damping coefficient D.

[0078] In practical applications, the output power P of the VSG will be determined by the current frequency ω and the reference frequency ω. * The difference between them is adjusted to ensure the initial stability of the frequency.

[0079] 2. Secondary frequency modulation control design:

[0080] Based on the primary frequency modulation control, the secondary frequency modulation control adds an integral control link to eliminate frequency deviation and achieve precise frequency control.

[0081] By adding the integral term K to the active frequency control equation i ∫(ω-ω *)dt, the frequency deviation can be accumulated and compensated to achieve more precise frequency control.

[0082] Segmented integral coefficient design: In order to improve the response speed and stability of frequency modulation control, the integral coefficient K i It is designed as a piecewise function and uses different integral coefficients according to different frequency deviation ranges to optimize control performance.

[0083] 3. Specific implementation steps:

[0084] Step 1: Design the VSG primary frequency modulation control block diagram:

[0085] Based on the VSG active frequency control equation, a primary frequency modulation control block diagram is designed to ensure rapid response and adjustment when the frequency deviation is small.

[0086] Step 2: Design the VSG secondary frequency modulation control block diagram:

[0087] On the basis of the primary frequency modulation control block diagram, an integral control link is added to eliminate the frequency deviation through integral control to ensure accurate frequency control.

[0088] Adopt segmented integral coefficients and design different integral coefficients K according to different frequency deviation ranges. i , to optimize control response and stability.

[0089] Through the above steps and methods, VSG secondary frequency modulation control based on segmented integral coefficients can be realized, effectively improving the frequency control performance and stability of VSG.

[0090] The method for designing a VSG secondary frequency modulation structure provided by an embodiment of the present invention is as follows:

[0091] (1) Design the VSG primary frequency modulation control block diagram;

[0092] According to the VSG active frequency control equation:

[0093]

[0094] The active frequency control block diagram can be obtained;

[0095] (2) Design the VSG secondary frequency modulation control block diagram;

[0096] Add an integral link to the active frequency control equation:

[0097]

[0098] The frequency secondary regulation control block diagram can be obtained.

[0099] The method for designing a segmented secondary frequency modulation control strategy provided by an embodiment of the present invention is as follows:

[0100] 1) Calculate the value range of the frequency integral coefficient:

[0101] The frequency integral coefficient is set to correspond to the damping ratio of the second-order system in the range of 0.1 to 0.3. The integral coefficient k satisfies the following conditions:

[0102]

[0103] According to the values ​​of Kp, D, and J, the value range of the integral coefficient k is determined as follows:

[0104]

[0105] 2) Method for determining segmented secondary frequency modulation:

[0106] In the value range of the integral coefficient k, the values ​​k1 and k2 are taken respectively, and the segmented control strategy is designed as follows:

[0107]

[0108] The value of ε is determined according to the variation range of the frequency offset.

[0109] Control block diagram of segmented secondary frequency modulation.

[0110] like Figure 2 As shown, a VSG secondary frequency modulation control system based on a piecewise integral coefficient provided by an embodiment of the present invention includes:

[0111] Frequency modulation structure design module, used to design VSG secondary frequency modulation structure;

[0112] The control strategy design module is used to design the segmented secondary frequency modulation control strategy.

[0113] The present invention is specifically implemented:

[0114] 1. Overall idea of ​​technical solution

[0115] For the part where the frequency deviation is higher than the threshold, a larger integral coefficient is used to improve the dynamic performance of the frequency response. For the part where the frequency deviation is lower than the threshold, a smaller integral coefficient is used to reduce the overshoot in the steady state.

[0116] 2. Specific implementation of technical solutions Figure 3 ;

[0117] Among them, C dc is the DC bus capacitance, I abc is the inverter output current, r and L are filter inductance and resistance respectively, C is filter capacitor, R is load, U s ,I sare the load terminal voltage and current respectively. P and Q are active power and reactive power respectively. m is the mechanical power, J is the moment of inertia, ω0 is the reference rotation angular frequency, D is the damping coefficient, k is the integral coefficient, Δf is the frequency offset, ε is the frequency offset threshold, K q is the voltage droop coefficient, Q ref is the reference reactive power, K u is the excitation regulation coefficient, U s is the synchronous generator output voltage, U ref is the reference output voltage of the synchronous generator, and E0 is the reference excitation electromotive force.

[0118] Step 1: Design the VSG secondary frequency modulation structure

[0119] Step 11: Design the VSG primary frequency modulation control block diagram

[0120] According to the VSG active frequency control equation:

[0121]

[0122] Available active frequency control frame Figure 4 :

[0123] Step 12: Design the VSG secondary frequency modulation control block diagram

[0124] Add an integral link to the active frequency control equation:

[0125]

[0126] Available frequency secondary adjustment control frame Figure 5 :

[0127] Step 2: Design a segmented secondary frequency modulation control strategy

[0128] Step 21: Calculate the value range of the frequency integral coefficient:

[0129] The frequency integral coefficient is set to correspond to the damping ratio of the second-order system in the range of 0.1 to 0.3. The integral coefficient k satisfies the following conditions:

[0130]

[0131] According to the values ​​of Kp, D, and J, the value range of the integral coefficient k is determined as follows:

[0132]

[0133] Step 22: Determine the method of segmented secondary frequency modulation, such as Figure 7 As shown:

[0134] In the value range of the integral coefficient k, the values ​​k1 and k2 are taken respectively, and the segmented control strategy is designed as follows:

[0135]

[0136] The value of ε is determined according to the variation range of the frequency offset.

[0137] Control box for segmented secondary frequency modulation Figure 6 for:

[0138] 3. Technical effects:

[0139] By setting the integral coefficient in segments, not only the frequency offset is reduced, but also the dynamic adjustment time of the frequency is shortened. Compared with other parameter adaptive control methods, the proposed control method only changes the integral coefficient twice during the dynamic adjustment process, which greatly reduces the number of changes of the integral coefficient and improves the stability of the frequency change during the dynamic process.

[0140] The expected control effects are as follows Figure 7 As shown:

[0141] 4. Technical effects brought about by the technical solution of the present invention

[0142] 1) Reduce the frequency offset and the dynamic frequency adjustment time.

[0143] 2) The number of times the integral coefficient is adjusted is reduced, and the stability of the system is improved.

[0144] 5. Regarding the technical solution in 4, are there other alternative solutions that can also achieve the purpose of the invention?

[0145] There is no other solution that can achieve the same invention purpose.

[0146] 6. Key technical points and pre-protection points of the invention

[0147] 1) A segmented control strategy based on the frequency offset is proposed to determine the value of the integral coefficient. The dynamic adjustment of the frequency is divided into two parts, namely the part where the frequency offset is lower than the threshold and the part where the frequency offset is higher than the threshold. For the part where the frequency offset is higher than the threshold, a larger integral coefficient is used to improve the dynamic performance of the frequency response. For the part where the frequency offset is lower than the threshold, a smaller integral coefficient is used to reduce the overshoot in the steady state.

[0148] The following are two specific industrial application embodiments of a VSG secondary frequency modulation control method based on a segmented integral coefficient:

[0149] Embodiment 1: Frequency regulation control in a wind power generation system

[0150] 1) Design of primary frequency regulation control block diagram: Based on the VSG active frequency control equation, a primary frequency regulation control block diagram is designed for the wind power generation system to ensure that the system can respond and adjust quickly to maintain frequency stability when the frequency deviation is small due to wind speed changes.

[0151] 2) Secondary frequency modulation control block diagram design: Based on the primary frequency modulation control block diagram, an integral control link is added to eliminate the frequency deviation through the segmented integral coefficient. According to different frequency deviation ranges (such as within ±0.1Hz, ±0.1Hz to ±0.5Hz), different integral coefficients k1 and k2 are designed to optimize the control response and stability.

[0152] 3) Determination of the segmented integral coefficient:

[0153] Calculate the value range of the frequency integral coefficient, set the damping ratio between 0.1 and 0.3, and determine the value range of the integral coefficient k as k1 between 0.05 and 0.15 and k2 between 0.15 and 0.3.

[0154] According to the frequency deviation range, design a segmented control strategy. For example, when the frequency deviation is within ±0.1Hz, use the integral coefficient k1; when the frequency deviation is between ±0.1Hz and ±0.5Hz, use the integral coefficient k2.

[0155] 4) Application results: Through the secondary frequency modulation control of the segmented integral coefficient, the wind power generation system can quickly recover when the frequency deviation is large, ensuring the frequency stability of the power grid and improving the grid-connected performance and system stability of wind power generation.

[0156] Example 2: Frequency Regulation Control in Microgrid

[0157] 1) Design of primary frequency regulation control block diagram: In the microgrid system, based on the VSG active frequency control equation, the primary frequency regulation control block diagram is designed to ensure that when the frequency deviation caused by load changes is small, the system can respond and adjust quickly to maintain frequency stability.

[0158] 2) Secondary frequency modulation control block diagram design: Based on the primary frequency modulation control block diagram, an integral control link is added to eliminate the frequency deviation through the segmented integral coefficient. According to different frequency deviation ranges (such as within ±0.2Hz, ±0.2Hz to ±0.6Hz), different integral coefficients k1 and k2 are designed to optimize the control response and stability.

[0159] 3) Determination of the segmented integral coefficient:

[0160] Calculate the value range of the frequency integral coefficient, set the damping ratio between 0.1 and 0.3, and determine the value range of the integral coefficient k as k1 between 0.05 and 0.12 and k2 between 0.12 and 0.25.

[0161] According to the frequency deviation range, a segmented control strategy is designed. For example, when the frequency deviation is within ±0.2Hz, the integral coefficient k1 is used; when the frequency deviation is between ±0.2Hz and ±0.6Hz, the integral coefficient k2 is used.

[0162] 4) Application results: Through the secondary frequency modulation control of the segmented integral coefficient, the microgrid system can recover quickly when the load changes greatly, ensuring the frequency stability of the power grid, improving the independent operation and stability of the microgrid, and enhancing the system's anti-disturbance ability.

[0163] These two embodiments demonstrate the practical effects and advantages of the VSG secondary frequency modulation control method based on segmented integral coefficients in different industrial applications.

[0164] Build a simulation model in Simulink. When the load increases from 35KW to 70KW, the frequency change curve is as follows Figure 8 As shown, compared with the control of fixed integral coefficient, the maximum frequency offset and frequency adjustment time under the segmented integral coefficient control are greatly reduced, which verifies the actual control effect of the present invention.

[0165] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A VSG secondary frequency modulation control method based on segmented integral coefficient, characterized in that: The following steps are involved: Step 1: Based on the VSG active frequency control equation, design a frequency modulation control block diagram to ensure rapid response and adjustment when the frequency deviation is small; Step 2, design the VSG secondary frequency modulation control block diagram: On the basis of the primary frequency modulation control block diagram, an integral control link is added to eliminate the frequency deviation through integral control to ensure accurate frequency control; a segmented integral coefficient is used to design different integral coefficients K according to different frequency deviation ranges. i , to optimize control response and stability.

2. The VSG secondary frequency modulation control method based on the segmented integral coefficient as claimed in claim 1, characterized in that: The method for designing the VSG secondary frequency modulation structure: (1) Design the VSG primary frequency modulation control block diagram; According to the VSG active frequency control equation: The active frequency control block diagram can be obtained; (2) Design the VSG secondary frequency modulation control block diagram; Add an integral link to the active frequency control equation: The frequency secondary regulation control block diagram can be obtained.

3. The VSG secondary frequency modulation control method based on the segmented integral coefficient as claimed in claim 1, characterized in that: The method for designing a segmented secondary frequency modulation control strategy: 1) Calculate the value range of the frequency integral coefficient: The frequency integral coefficient is set to correspond to the damping ratio of the second-order system in the range of 0.1 to 0.

3. The integral coefficient k satisfies the following conditions: According to the values ​​of Kp, D, and J, the value range of the integral coefficient k is determined as follows: 2) Method for determining segmented secondary frequency modulation: In the value range of the integral coefficient k, the values ​​k1 and k2 are taken respectively, and the segmented control strategy is designed as follows: The value of ε is determined according to the variation range of the frequency offset. Control block diagram of segmented secondary frequency modulation.

4. A VSG secondary frequency modulation control system based on a piecewise integral coefficient that implements the VSG secondary frequency modulation control method according to any one of claims 1 to 3, characterized in that: include: VSG primary frequency modulation control module is used to design the VSG primary frequency modulation control block diagram, and obtain the active frequency control block diagram according to the VSG active frequency control equation; The VSG secondary frequency regulation control module is used to add an integral link to the active frequency control equation to obtain a frequency secondary regulation control block diagram; The segmented integral coefficient calculation module is used to calculate the value range of the frequency integral coefficient, set the frequency integral coefficient to correspond to the damping ratio in the range of 0.1 to 0.3 of the second-order system, and determine the value range of the integral coefficient k; The segmented control strategy design module is used to respectively select values ​​k1 and k2 within the value range of the integral coefficient k, determine the value according to the variation range of the frequency offset, and design the control strategy of segmented secondary frequency modulation.

5. The VSG secondary frequency modulation control system based on piecewise integral coefficient as claimed in claim 4, characterized in that: The VSG primary frequency modulation control module includes: According to the active frequency control equation: Designed active frequency control block diagram; The VSG secondary frequency modulation control module adds an integral link to the active frequency control equation: Designed frequency secondary regulation control block diagram.

6. The VSG secondary frequency modulation control system based on piecewise integral coefficient as claimed in claim 4, characterized in that: The segmented control strategy design module includes: Calculate the value range of the frequency integral coefficient k, and determine the value range of the integral coefficient k according to the values ​​of Kp, D, and J: In the value range of the integral coefficient k, the values ​​k1 and k2 are taken respectively, and the designed segmented control strategy is as follows: The value of ε is determined according to the variation range of the frequency offset.

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