Cascading failure ride-through control method of virtual synchronous generator and related device

Abstract

The invention belongs to the technical field of power grid voltage faults, and particularly relates to a cascading fault ride-through control method of a virtual synchronous generator and a related device. The control method comprises the following steps of firstly performing low-voltage fault ride-through control and then performing high-voltage fault ride-through control; low-voltage fault ride-through control is active power control, specifically, a virtual damping adaptive control method is adopted to dynamically adjust a virtual damping coefficient, and power angle divergence of a virtual synchronous generator during a low-voltage fault of a power grid is suppressed; the high-voltage fault ride-through control is reactive power control, specifically, a reactive droop coefficient adaptive adjustment control method is adopted to adjust the reactive droop coefficient of the virtual synchronous generator, and the reactive power and the output voltage during cascading failure are improved. The problem of fault ride-through of the virtual synchronous generator during low-voltage and high-voltage cascading faults of a power grid is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power grid voltage faults, and in particular relates to a cascading fault ride-through control method for a virtual synchronous generator and a related device. Background Art

[0002] With the rapid growth of installed capacity of renewable energy power generation, the power system will be characterized by a high proportion of renewable energy. In some remote areas, the large-scale deployment of renewable energy coupled with a limited supply of local thermal power units has resulted in weak frequency regulation and reactive power / voltage support capabilities. This has already led to, or is about to lead to, weak synchronous voltage support grid systems. Power electronic devices lack inertia and damping, making them unable to provide frequency and voltage support for the grid. This results in a reduction in the system's effective rotational inertia and a sharp drop in dynamic reactive power reserves, increasing the risk of safety and stability issues such as grid loss of synchronization, voltage collapse, frequency instability, and broadband oscillation.

[0003] Virtual Synchronous Generator (VSG) control technology has emerged as a response to this challenge. By incorporating the rotor's equations of motion to increase the system's inertia and damping, it can provide voltage and frequency support for the grid, preventing frequency instability caused by rapidly fluctuating loads. It also participates in voltage and frequency regulation, contributing to high grid stability. However, when the grid voltage drops, traditional VSG control strategies based on active power-frequency control can cause output current to exceed limits, potentially damaging power electronic components and causing the inverter to disconnect from the grid. Furthermore, even during low voltage ride-through, VSGs are unable to provide reactive power support for the grid, hindering grid voltage recovery.

[0004] High-voltage faults in power systems are often accompanied by low-voltage faults, known as cascading faults. These faults can be categorized as low-voltage and high-voltage cascading faults, and high-voltage and low-voltage cascading faults. Current research on grid voltage faults focuses primarily on low-voltage fault ride-through technology, while research on cascading voltage faults is limited, and effective control solutions are still lacking.

[0005] Therefore, how to achieve safe and stable operation of virtual synchronous generators when grid voltage cascading failures occur while providing reactive voltage support for the grid has become an urgent issue. Summary of the Invention

[0006] The purpose of the present invention is to provide a cascading fault ride-through control method and related devices for a virtual synchronous generator, so as to solve the problem of fault ride-through of the virtual synchronous generator when the grid voltage is low or high voltage cascading fault occurs.

[0007] The present invention is achieved through the following technical solutions: The present invention discloses a cascading fault ride-through control method for a virtual synchronous generator, including low voltage fault ride-through control and high voltage fault ride-through control; The specific process of low voltage fault ride-through control is as follows: The obtained VSG angular frequency variation, VSG output angular frequency differential and original virtual damping coefficient are dynamically adjusted by the virtual damping adaptive control method to obtain the virtual damping coefficient after virtual damping adaptive control; After calculating the active power reference value, active power sampling value, VSG frequency steady-state value, grid frequency and virtual damping coefficient after virtual damping adaptive control, the VSG power angle is output; The specific process of high voltage fault ride-through control is as follows: Obtain the reactive power droop coefficient setting value, common coupling point voltage, grid voltage, AC voltage upper limit coefficient and AC voltage lower limit coefficient; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage upper limit coefficient to obtain the gain coefficient of the upper limit AC voltage; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage lower limit coefficient to obtain the gain coefficient of the lower limit AC voltage; According to the size of the grid voltage, the value of the upper limit switch quantity and the value of the lower limit switch quantity are selected, and based on the gain coefficient of the upper limit AC voltage, the gain coefficient of the lower limit AC voltage, the value of the upper limit switch quantity, the value of the lower limit switch quantity and the reactive droop coefficient setting value, the updated reactive droop coefficient is obtained.

[0008] Furthermore, the expression corresponding to the virtual damping adaptive control method is: ; The active power reference value, active power sampling value, VSG frequency steady-state value, grid frequency and virtual damping coefficient after virtual damping adaptive control are calculated to output the VSG power angle; the corresponding expression is: ; ; in, is the power angle change rate; is the change in VSG angular frequency; is the steady-state value of VSG frequency; is the grid frequency; is the rate of change of VSG angular frequency; is the virtual inertia coefficient; is the active power reference value; is the active power sampling value; is the proportional coefficient of the proportional branch in the virtual damping adaptive control; is the proportional coefficient of the integral branch in the virtual damping adaptive control; is the differential of the VSG output angular frequency; is the virtual damping coefficient after virtual damping adaptive control; is the virtual damping coefficient; and are the voltage at the point of common coupling and the grid voltage, respectively. is the transmission line reactance, is the VSG power angle, sin() is the sine function.

[0009] Furthermore, the calculation expressions of the gain coefficient of the upper limit AC voltage and the gain coefficient of the upper limit AC voltage are: ; in, is the gain coefficient of the upper limit AC voltage, is the gain coefficient of the lower limit AC voltage; is the AC voltage upper limit coefficient, is the lower limit coefficient of AC voltage; is the voltage at the common coupling point; R g is the grid resistance; L g is the grid inductance; is the grid angular frequency.

[0010] Furthermore, during the high voltage fault ride-through control process, it is also necessary to obtain the lower and upper limits of the grid voltage; According to the size of the grid voltage, the value of the upper limit switch quantity and the value of the lower limit switch quantity are selected, and based on the gain coefficient of the upper limit AC voltage, the gain coefficient of the lower limit AC voltage, the value of the upper limit switch quantity, the value of the lower limit switch quantity and the reactive droop coefficient setting value, the updated reactive droop coefficient is obtained, which is specifically: When the grid voltage is between the lower limit and the upper limit, the updated reactive power droop coefficient is equal to the reactive power droop coefficient setting value; When the grid voltage is higher than the upper limit, the upper limit switch value is set to 1, and the first voltage deviation is multiplied by the gain coefficient of the upper limit AC voltage as the reactive droop coefficient compensation amount; When the AC voltage is lower than the lower limit, the lower limit switch value is set to 1, and the second voltage deviation is multiplied by the gain coefficient of the lower limit AC voltage as the reactive droop coefficient compensation amount; When the grid voltage is higher than the upper limit or lower than the lower limit, the reactive droop coefficient compensation amount is superimposed on the reactive droop coefficient setting value to obtain an updated reactive droop coefficient.

[0011] Furthermore, the first voltage deviation is a result of multiplying the voltage at the common coupling point by the AC voltage upper limit coefficient and then subtracting the result from the grid voltage processed by the low-pass filter; The second voltage deviation is a result of multiplying the voltage at the common coupling point by the AC voltage lower limit coefficient and then subtracting the result from the grid voltage processed by the low-pass filter.

[0012] Furthermore, the calculation expression of the reactive droop coefficient compensation amount is: ; in, is the reactive droop coefficient compensation; is the gain coefficient of the upper limit AC voltage; is the gain coefficient of the lower limit AC voltage; is the AC voltage upper limit coefficient; is the lower limit coefficient of AC voltage; is the voltage at the point of common coupling; is the grid voltage; It is the upper limit switch value; is the lower limit switch value; Represents the transfer function of the low-pass filter in the complex frequency domain.

[0013] Furthermore, when the grid voltage is higher than the upper limit or lower than the lower limit, the updated reactive droop coefficient calculation expression is: ; is the reactive droop coefficient setting value, is the updated reactive droop coefficient.

[0014] The present invention also discloses a cascading fault ride-through control system for a virtual synchronous generator, comprising a low-voltage fault ride-through control module and a high-voltage fault ride-through control module: The low voltage fault ride-through control module is used to perform low voltage fault ride-through control. The specific process is as follows: The obtained VSG angular frequency variation, VSG output angular frequency differential and original virtual damping coefficient are dynamically adjusted by the virtual damping adaptive control method to obtain the virtual damping coefficient after virtual damping adaptive control; After calculating the active power reference value, active power sampling value, VSG frequency steady-state value, grid frequency and virtual damping coefficient after virtual damping adaptive control, the VSG power angle is output; The high voltage fault ride-through control module is used to perform high voltage fault ride-through control. The specific process is as follows: Obtain the reactive power droop coefficient setting value, common coupling point voltage, grid voltage, AC voltage upper limit coefficient and AC voltage lower limit coefficient; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage upper limit coefficient to obtain the gain coefficient of the upper limit AC voltage; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage lower limit coefficient to obtain the gain coefficient of the lower limit AC voltage; According to the size of the grid voltage, the value of the upper limit switch quantity and the value of the lower limit switch quantity are selected, and based on the gain coefficient of the upper limit AC voltage, the gain coefficient of the lower limit AC voltage, the value of the upper limit switch quantity, the value of the lower limit switch quantity and the reactive droop coefficient setting value, the updated reactive droop coefficient is obtained.

[0015] The present invention also discloses a computer device, comprising a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the cascading fault ride-through control method of the virtual synchronous generator are implemented.

[0016] The present invention also discloses a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the cascading fault ride-through control method of the virtual synchronous generator are implemented.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for controlling the cascading fault ride-through of a virtual synchronous generator, which divides the low- and high-voltage cascading fault ride-through into two aspects: active power control and reactive power control. In the active power control, dynamic damping control is proposed to suppress the power angle divergence under low-voltage faults, and droop coefficient adaptive control is proposed to have the reactive power support function under high-voltage faults. The present invention adopts a dual control mechanism to perform fine control on active and reactive power respectively, thereby improving the adaptability and stability of the system under different fault conditions and overcoming the limitations of the single control strategy in the prior art. It realizes the intelligent ride-through control of the virtual synchronous generator during the cascading fault of the power grid voltage, and ensures the safe operation and stability of the system during the fault by rationally allocating active and reactive power. Therefore, in the event of a cascading fault of the power grid voltage, the method proposed by the present invention can effectively improve the stability of the virtual synchronous generator during the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the block diagram of virtual damping adaptive control; Figure 2 When the power grid fails, the virtual damping adaptive control is used. phase trajectory; Figure 3 The VSG stable region consists of different virtual inertia and virtual damping critical values; Figure 4 The simulation curve obtained for the stability analysis of virtual damping adaptive control; Among them, (a) is Phase trajectory curve; (b) Figure shows the VSG power angle Time domain response curve of Figure 5 It is the control block diagram of the reactive power control loop; Figure 6 This is the reactive droop coefficient adaptive regulation control block diagram; Figure 7 This is the simulation curve obtained by the stability analysis of the adaptive control of reactive droop coefficient; Among them, (a) is Phase trajectory curve; (b) Figure is Time domain response curve; (c) Figure is Time domain response curve; Figure 8 The simulation waveforms are for comparing the performance of the control method of the present invention and that of the control method without the present invention under voltage cascading faults; Among them, (a) shows the change of grid voltage over time; (b) shows the change of active power over time; (c) shows the change of reactive power over time; (d) shows the change of power angle over time; (e) shows the change of output frequency over time. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a further detailed description with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0020] The detailed description of the embodiment of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. All other embodiments derived by those skilled in the art based on the figures and embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0021] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0022] Voltage cascading faults consist of two parts: a low-voltage fault and a high-voltage fault. Virtual synchronous generator (VSG) control includes low-voltage fault ride-through control and high-voltage fault ride-through control. Low-voltage fault ride-through control is active power control, while high-voltage fault ride-through control is reactive power control. The voltage cascading fault ride-through control method designed in this invention requires improvements to the active power loop and the reactive power loop.

[0023] The present invention first introduces the relevant contents of the active power control improvement method.

[0024] like Figure 1 As shown in the block diagram of virtual damping adaptive control, the present invention proposes a method that can dynamically adjust the virtual damping coefficient according to the change in VSG angular frequency and the angular frequency differential, which is used to suppress the VSG power angle divergence when the grid voltage fails, ensure the stability of the VSG, and will not affect the operation of the VSG when the grid is normal.

[0025] like Figure 1 As shown, the VSG power angle is express, and is the adjustment coefficient, is a differential operator. Virtual damping adaptive control dynamically adjusts the virtual damping coefficient based on the VSG angular frequency change and the differential of the VSG output angular frequency, along with the original virtual damping coefficient. This adaptive control strategy maintains the VSG's virtual damping coefficient in steady state, but dynamically adjusts it during a fault condition, depending on the severity of the grid voltage fault.

[0026] illustrate Figure 1 Corresponding process: The input of the low voltage ride-through VSG damping adaptive control block diagram is the active power reference value , active power sampling value , virtual damping coefficient after virtual damping adaptive control ; Output is VSG power angle ; It is the result of superposition of three intermediate variables, specifically the VSG frequency change , virtual damping coefficient and the proportionality factor The product of the VSG output angular frequency and proportionality coefficient and differential operators Then, through the virtual inertia coefficient and integral operation process, and with the VSG frequency steady-state value After superposition, the integral operation Processing to obtain VSG output power angle .

[0027] Specifically, if Figure 1 As shown in the figure, the output signal expression can be derived from the virtual damping adaptive control block diagram as follows: (1) (2) (3) in, is the power angle change rate; is the change in VSG angular frequency; is the steady-state value of VSG frequency; is the grid frequency; is the rate of change of VSG angular frequency; is the virtual inertia coefficient; is the active power reference value; is the active power sampling value; is the proportional coefficient of the proportional branch in the virtual damping adaptive control; is the proportional coefficient of the integral branch in the virtual damping adaptive control; is the differential of the VSG output angular frequency; is the virtual damping coefficient after virtual damping adaptive control; is the virtual damping coefficient; and are the voltage at the point of common coupling and the grid voltage, respectively. is the transmission line reactance, is the VSG power angle, sin() is the sine function.

[0028] When the low voltage grid fault is drawn using formula (1)-formula (3), that is, When the virtual damping adaptive control The phase trajectory of Figure 2 shown.

[0029] Depend on Figure 2 It can be seen that The phase trajectory runs stably at another equilibrium point after the oscillation process, indicating that the virtual damping adaptive control enhances the stability of the virtual synchronous generator during low-voltage grid faults.

[0030] When the low voltage grid fails, the grid voltage When it is reduced from 1p.u to 0.5pu, we get Figure 3 The virtual synchronous generator stability region is composed of different virtual inertia and virtual damping coefficient critical values ​​shown in FIG. Figure 3 It can be seen that when the virtual inertia Increase to During the process, the virtual damping coefficient Will not increase. Then, if the virtual inertia Continue to increase, the virtual damping coefficient It also begins to increase and is approximately linear. The entire area is divided into stable and unstable areas, and the following conclusions can be drawn: 1. If the virtual inertia Increase, virtual damping coefficient It must continue to increase, otherwise the VSG system is at risk of instability. Reduce, virtual damping coefficient No need to change.

[0031] 2. Virtual inertia No need to follow the virtual damping coefficient increases with the increase of , but the virtual inertia The virtual damping coefficient must be When it decreases, it also decreases.

[0032] The above analysis shows that in order to keep the VSG system stable, it is necessary to ensure that there is a sufficient virtual damping coefficient . Virtual damping coefficient It plays a key role in maintaining the stability of the VSG system during the oscillation process.

[0033] When the low voltage grid fails, the stability analysis of virtual damping adaptive control is carried out. and The impact on the adaptive control of virtual damping coefficient is as follows: Figure 4 As shown, Figure (a) shows Phase trajectory curve, Figure (b) shows the VSG power angle Time domain response curve.

[0034] When the virtual damping adaptive control method proposed in the present invention is not added, the VSG power angle There will be divergence; and after adding the virtual damping adaptive control method proposed by the present invention, and If the VSG power angle is too small, There will also be divergence, such as Figure 4 This is shown in the green and orange simulation curves.

[0035] like Figure 4As shown in Figure (a), with and The increase, The stability of the phase trajectory gradually increases and the oscillation decreases; Figure 4 As shown in Figure (b), with and The increase of VSG power angle It keeps decreasing and moving away from the critical value, indicating that the stability of the VSG system is gradually increasing.

[0036] The following introduces the methods for improving reactive power control.

[0037] Figure 5 The control block diagram of the reactive power control loop is shown in Figure 2. The reactive power is used to adjust the VSG output voltage, where the feedback loop is controlled by the reactive droop coefficient. To correct the reactive power, the present invention proposes an adaptive droop coefficient control (ADCC) method to improve the reactive power and output voltage performance during cascading faults.

[0038] like Figure 5 As shown in FIG, the reactive power control loop completes reactive power control by making a difference between the output voltage V and the voltage reference value V0, and then feeding back the difference after proportional adjustment to the reactive power reference value Q0.

[0039] Figure 6 This is the adaptive regulation control block diagram of the reactive power droop system. and They are the upper and lower limit coefficients of AC voltage, which are responsible for controlling the voltage limit of adaptive regulation. The low-pass filter LPF is used to filter out the grid voltage. The high frequency components in the circuit can avoid affecting the control effect. and They are the gain coefficients corresponding to the upper and lower limit AC voltages in the adaptive regulation control. is the upper limit switch value, It is the lower limit switch value, which is used to indicate that the grid voltage exceeds the upper limit or lower limit.

[0040] When the grid voltage When it is between the lower limit and the upper limit, 、 、 All are zero, the reactive power droop coefficient is equal to the reactive power droop coefficient setting value .

[0041] When the grid voltage When the upper limit value is exceeded, the upper limit switch Take 1 and multiply the first voltage deviation by As reactive droop coefficient compensation .

[0042] When the AC voltage is lower than the lower limit, the lower limit switch Take 1 and multiply the second voltage deviation by As reactive droop coefficient compensation .

[0043] Reactive power droop coefficient compensation When the AC voltage is higher than the upper limit or lower than the lower limit, it is superimposed on the reactive droop coefficient setting value. The reactive power droop coefficient is reasonably allocated to improve the AC voltage regulation performance during cascading faults. At this time, the expression of the updated reactive power droop coefficient is: ; in, (4) Represents the transfer function of the low-pass filter (LPF) in the complex frequency domain.

[0044] The first voltage deviation is the common coupling point voltage and AC voltage upper limit coefficient After multiplication, it is then combined with the grid voltage processed by the low-pass filter LPF The result of doing something bad.

[0045] The second voltage deviation is the common coupling point voltage and AC voltage lower limit coefficient After multiplication, it is then combined with the grid voltage processed by the low-pass filter LPF The result of doing something bad.

[0046] AC voltage upper limit coefficient and AC voltage lower limit coefficient It needs to be set according to the actual situation. and It can be obtained by the following formula: (5) in, is the gain coefficient of the upper limit AC voltage, is the gain coefficient of the lower limit AC voltage; is the AC voltage upper limit coefficient, is the lower limit coefficient of AC voltage; is the voltage at the common coupling point; R g is the grid resistance; L g is the grid inductance; is the grid angular frequency.

[0047] The gain coefficient of the upper limit AC voltage and the gain coefficient of the upper limit AC voltage can be calculated by formula (4), and the stability analysis of the reactive droop adaptive regulation control can be performed.

[0048] like Figure 7 As shown in Figure (a), the stability analysis of the reactive droop coefficient adaptive regulation control is carried out, and the Phase trajectory curve, shown in Figure (b) The time domain response curve, shown in Figure (c) Time domain response curve.

[0049] Depend on Figure 7 As can be seen from Figure (a) in the figure, under different voltage changes, the use of reactive droop coefficient adaptive control can significantly reduce Phase trajectory oscillation ensures stable operation of VSG.

[0050] Depend on Figure 7 As can be seen from Figure (b) in the figure, under different voltage changes, when the reactive droop coefficient adaptive control is adopted, the VSG power angle It will stabilize over time.

[0051] Depend on Figure 7 As can be seen from Figure (c) in the figure, under different voltage changes, when the reactive droop coefficient adaptive control is adopted, the VSG angular frequency change is It will stabilize over time.

[0052] The method for improving cascading fault performance proposed in this paper serves as a basic approach to enhance the stability of VSGs during cascading grid voltage faults. Proper parameter design can ensure continued stable operation of the VSG during faults. However, the extent of sudden grid voltage dips or surges is unpredictable. Traditional damping control only performs well under faults with specific voltage amplitudes and cannot adapt the output damping level to changes in voltage fault conditions. Therefore, traditional damping control cannot guarantee the stability of the VSG under different voltage fault conditions.

[0053] Figure 8 The control method of the present invention and the control method without the present invention are respectively Simulated waveforms comparing performance under these conditions: (a) Grid voltage versus time; (b) Active power versus time; (c) Reactive power versus time; (d) Power angle versus time; (e) Output frequency versus time. It can be seen that a system without the proposed method cannot guarantee stable VSG operation during a low-voltage fault. During this period, the VSG's active power varies significantly, and the VSG's power angle continuously increases. However, the proposed control method can adjust the damping output according to the severity of the low-voltage fault, ensuring stable VSG operation during this period.

[0054] At the same time, the control method proposed in this invention can significantly reduce the transient overshoot of active and reactive power during high voltage faults. From the perspective of adapting to complex grid voltage faults, the control method proposed in this invention can effectively improve the stability of VSG under voltage cascading faults.

[0055] The present invention mainly analyzes low-voltage and high-voltage chain failures as an example. Low-voltage and high-voltage chain failures are generally caused by load switching during low-voltage faults, or by the failure to promptly withdraw the compensation capacitor group during low-voltage faults. The study of low-voltage and high-voltage chain failures is divided into two parts: the low-voltage fault stage and the high-voltage fault stage. The low-voltage fault stage mainly focuses on improving stability. Dynamic damping control is proposed to enhance the stability of VSG under low-voltage faults, and the phase plane method is used to analyze the improvement effect. The results show that dynamic damping control can effectively improve the stability of VSG during low-voltage faults. The high-voltage fault stage mainly focuses on power overshoot and power oscillation. Virtual capacitor feedback control is proposed to reduce power overshoot and power oscillation, and can enable VSG to absorb reactive power to help the voltage at the fault point recover. Finally, the phase plane method is used for analysis, which shows that virtual capacitor feedback control effectively reduces power overshoot and oscillation during high-voltage faults.

[0056] The present invention also discloses a cascading fault ride-through control system for a virtual synchronous generator, comprising: Low voltage fault ride-through control module: Low voltage fault ride-through control is active power control. Specifically, it adopts a virtual damping adaptive control method to dynamically adjust the virtual damping coefficient to suppress the divergence of the virtual synchronous generator power angle when the grid is under low voltage fault; High voltage fault ride-through control module: High voltage fault ride-through control is reactive power control. Specifically, the reactive droop coefficient adaptive adjustment control method is used to adjust the reactive droop coefficient of the virtual synchronous generator to improve the reactive power and output voltage during cascading faults.

[0057] The present invention also discloses a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for controlling cascading faults of a virtual synchronous generator is implemented. The memory may include internal memory, such as a high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device. The processor, network interface, and memory are interconnected via an internal bus. The internal bus may be an industrial standard architecture bus, a peripheral component interconnect standard bus, an extended industrial standard architecture bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the programs may include program code, and the program code includes computer operating instructions. The memory may include internal memory and non-volatile memory, and provides instructions and data to the processor.

[0058] The present invention also discloses a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the cascading fault ride-through control method of the virtual synchronous generator. Specifically, the computer-readable storage medium includes but is not limited to, for example, a volatile memory and / or a non-volatile memory.

[0059] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, optical storage, etc.) containing computer-usable program code.

[0060] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0061] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0062] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A cascading fault ride-through control method for a virtual synchronous generator, characterized in that: The cascading fault ride-through control method includes low voltage fault ride-through control and high voltage fault ride-through control; The specific process of low voltage fault ride-through control is as follows: The obtained VSG angular frequency variation, VSG output angular frequency differential and original virtual damping coefficient are dynamically adjusted by the virtual damping adaptive control method to obtain the virtual damping coefficient after virtual damping adaptive control; After calculating the active power reference value, active power sampling value, VSG frequency steady-state value, grid frequency and virtual damping coefficient after virtual damping adaptive control, the VSG power angle is output; The specific process of high voltage fault ride-through control is as follows: Obtain the reactive power droop coefficient setting value, common coupling point voltage, grid voltage, AC voltage upper limit coefficient and AC voltage lower limit coefficient; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage upper limit coefficient to obtain the gain coefficient of the upper limit AC voltage; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage lower limit coefficient to obtain the gain coefficient of the lower limit AC voltage; According to the size of the grid voltage, the value of the upper limit switch quantity and the value of the lower limit switch quantity are selected, and based on the gain coefficient of the upper limit AC voltage, the gain coefficient of the lower limit AC voltage, the value of the upper limit switch quantity, the value of the lower limit switch quantity and the reactive droop coefficient setting value, the updated reactive droop coefficient is obtained.

2. The cascading fault ride-through control method of a virtual synchronous generator according to claim 1, characterized in that: The expression corresponding to the virtual damping adaptive control method is: ； The active power reference value, active power sampling value, VSG frequency steady-state value, grid frequency and virtual damping coefficient after virtual damping adaptive control are calculated to output the VSG power angle; the corresponding expression is: ； ； in, is the power angle change rate; is the change in VSG angular frequency; is the steady-state value of VSG frequency; is the grid frequency; is the rate of change of VSG angular frequency; is the virtual inertia coefficient; is the active power reference value; is the active power sampling value; is the proportional coefficient of the proportional branch in the virtual damping adaptive control; is the proportional coefficient of the integral branch in the virtual damping adaptive control; is the differential of the VSG output angular frequency; is the virtual damping coefficient after virtual damping adaptive control; is the virtual damping coefficient; and are the voltage at the point of common coupling and the grid voltage, respectively. is the transmission line reactance, is the VSG power angle, sin() is the sine function.

3. The cascading fault ride-through control method of a virtual synchronous generator according to claim 1, characterized in that: The calculation expressions of the gain coefficient of the upper limit AC voltage and the gain coefficient of the upper limit AC voltage are: ； in, is the gain coefficient of the upper limit AC voltage, is the gain coefficient of the lower limit AC voltage; is the AC voltage upper limit coefficient, is the lower limit coefficient of AC voltage; is the voltage at the common coupling point; R g is the grid resistance; L g is the grid inductance; is the grid angular frequency.

4. The method for controlling cascading fault ride-through of a virtual synchronous generator according to claim 1, characterized in that: During the high voltage fault ride-through control process, it is also necessary to obtain the lower and upper limits of the grid voltage; According to the size of the grid voltage, the value of the upper limit switch quantity and the value of the lower limit switch quantity are selected, and based on the gain coefficient of the upper limit AC voltage, the gain coefficient of the lower limit AC voltage, the value of the upper limit switch quantity, the value of the lower limit switch quantity and the reactive droop coefficient setting value, the updated reactive droop coefficient is obtained, which is specifically: When the grid voltage is between the lower limit and the upper limit, the updated reactive power droop coefficient is equal to the reactive power droop coefficient setting value; When the grid voltage is higher than the upper limit, the upper limit switch value is set to 1, and the first voltage deviation is multiplied by the gain coefficient of the upper limit AC voltage as the reactive droop coefficient compensation amount; When the AC voltage is lower than the lower limit, the lower limit switch value is set to 1, and the second voltage deviation is multiplied by the gain coefficient of the lower limit AC voltage as the reactive droop coefficient compensation amount; When the grid voltage is higher than the upper limit or lower than the lower limit, the reactive droop coefficient compensation amount is superimposed on the reactive droop coefficient setting value to obtain an updated reactive droop coefficient.

5. The cascading fault ride-through control method of a virtual synchronous generator according to claim 4, characterized in that: The first voltage deviation is the result of multiplying the voltage at the common coupling point by the AC voltage upper limit coefficient and then subtracting it from the grid voltage processed by the low-pass filter; The second voltage deviation is a result of multiplying the voltage at the common coupling point by the AC voltage lower limit coefficient and then subtracting the result from the grid voltage processed by the low-pass filter.

6. The method for controlling cascading fault ride-through of a virtual synchronous generator according to claim 4, characterized in that: The calculation expression of the reactive droop coefficient compensation amount is: ； in, is the reactive droop coefficient compensation; is the gain coefficient of the upper limit AC voltage; is the gain coefficient of the lower limit AC voltage; is the AC voltage upper limit coefficient; is the lower limit coefficient of AC voltage; is the voltage at the point of common coupling; is the grid voltage; It is the upper limit switch value; is the lower limit switch value; Represents the transfer function of the low-pass filter in the complex frequency domain.

7. The method for controlling cascading fault ride-through of a virtual synchronous generator according to claim 6, characterized in that: When the grid voltage is higher than the upper limit or lower than the lower limit, the updated reactive droop coefficient calculation expression is: ； is the reactive droop coefficient setting value, is the updated reactive droop coefficient.

8. A cascading fault ride-through control system for a virtual synchronous generator, characterized in that: Including low voltage fault ride-through control module and high voltage fault ride-through control module: The low voltage fault ride-through control module is used to perform low voltage fault ride-through control. The specific process is as follows: The obtained VSG angular frequency variation, VSG output angular frequency differential and original virtual damping coefficient are dynamically adjusted by the virtual damping adaptive control method to obtain the virtual damping coefficient after virtual damping adaptive control; After calculating the active power reference value, active power sampling value, VSG frequency steady-state value, grid frequency and virtual damping coefficient after virtual damping adaptive control, the VSG power angle is output; The high voltage fault ride-through control module is used to perform high voltage fault ride-through control. The specific process is as follows: Obtain the reactive power droop coefficient setting value, common coupling point voltage, grid voltage, AC voltage upper limit coefficient and AC voltage lower limit coefficient; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage upper limit coefficient to obtain the gain coefficient of the upper limit AC voltage; After the grid voltage is filtered, it is calculated with the common coupling point voltage and the AC voltage lower limit coefficient to obtain the gain coefficient of the lower limit AC voltage; According to the size of the grid voltage, the value of the upper limit switch quantity and the value of the lower limit switch quantity are selected, and based on the gain coefficient of the upper limit AC voltage, the gain coefficient of the lower limit AC voltage, the value of the upper limit switch quantity, the value of the lower limit switch quantity and the reactive droop coefficient setting value, the updated reactive droop coefficient is obtained.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the cascading fault ride-through control method for a virtual synchronous generator according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the cascading fault ride-through control method for a virtual synchronous generator according to any one of claims 1 to 6 are implemented.

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