A method and related device for cascading fault ride-through control of a virtual synchronous generator

Abstract

This invention belongs to the field of power grid voltage fault technology, specifically relating to a method and related apparatus for cascading fault ride-through control of a virtual synchronous generator. The control method includes the following processes: first, low-voltage fault ride-through control is performed, followed by high-voltage fault ride-through control; the low-voltage fault ride-through control is active power control, specifically employing a virtual damping adaptive control method to dynamically adjust the virtual damping coefficient, suppressing the power angle divergence of the virtual synchronous generator during low-voltage grid faults; the high-voltage fault ride-through control is reactive power control, specifically employing a reactive power droop coefficient adaptive adjustment control method to adjust the reactive power droop coefficient of the virtual synchronous generator, improving reactive power and output voltage during cascading faults. This solves the problem of fault ride-through of virtual synchronous generators during low grid voltage and high-voltage cascading faults.

Description

Technical Field

[0001] This invention belongs to the field of power grid voltage fault technology, specifically relating to a cascading fault ride-through control method and related devices for a virtual synchronous generator. Background Technology

[0002] With the rapid growth of installed capacity of new energy power generation, the power system will be characterized by a high proportion of new energy. In some remote areas, the large-scale use of new energy coupled with a limited number of local thermal power units results in weak frequency regulation and reactive power / voltage support capabilities, leading to the formation or imminent formation of a weak synchronous voltage support grid system. Power electronic devices lack inertia and damping, failing to provide frequency and voltage support to the grid. This reduces the system's effective rotational inertia, drastically decreases dynamic reactive power reserves, and increases the risk of grid synchronism issues such as voltage collapse, frequency instability, and wideband oscillations.

[0003] Virtual Synchronous Generator (VSG) control technology has emerged to address this need. By introducing rotor motion equations to increase system inertia and damping, it can provide voltage and frequency support to the power grid, preventing frequency instability caused by rapidly fluctuating loads. It also participates in grid voltage and frequency regulation, resulting in high grid stability. However, when grid voltage drops, traditional VSG control strategies based on active power-frequency control can lead to excessive output current, damaging power electronic devices and causing inverter disconnection. Furthermore, it cannot provide reactive power support to the grid even during low-voltage ride-throughs, hindering grid voltage recovery.

[0004] High-voltage faults in power grids are generally accompanied by low-voltage faults, a phenomenon known as cascading faults. These cascading faults can be further categorized into low-voltage / high-voltage cascading faults and high-voltage / low-voltage cascading faults. Current research on grid voltage faults primarily focuses on low-voltage fault ride-through technology, while research on grid voltage cascading faults is limited, and effective control schemes are not yet mature.

[0005] Therefore, how to achieve safe and stable operation of virtual synchronous generators during grid voltage cascading faults, while providing reactive voltage support to the grid, is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method and related device for cascading fault ride-through control of a virtual synchronous generator, which solves the problem of fault ride-through of a virtual synchronous generator when the grid voltage is low or there is a high-voltage cascading fault.

[0007] This invention is achieved through the following technical solution:

[0008] This 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;

[0009] The low-voltage fault ride-through control process is as follows:

[0010] The obtained VSG angular frequency change, the differential of VSG output angular frequency, and the 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.

[0011] The active power reference value, active power sample value, VSG frequency steady-state value, grid frequency, and virtual damping coefficient after virtual damping adaptive control are calculated and the VSG power angle is output.

[0012] The high-voltage fault ride-through control process is as follows:

[0013] Obtain the reactive power droop factor setting value, common coupling point voltage, grid voltage, AC voltage upper limit factor, and AC voltage lower limit factor;

[0014] After the grid voltage is filtered, the gain coefficient of the upper limit AC voltage is obtained by calculating the voltage at the common coupling point and the upper limit coefficient of the AC voltage.

[0015] After the grid voltage is filtered, the gain coefficient of the lower limit AC voltage is obtained by calculating the voltage at the point of common coupling and the lower limit coefficient of the AC voltage.

[0016] Based on the magnitude of the grid voltage, the values ​​of the upper limit switch quantity and the lower limit switch quantity are selected. 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 set value of the reactive power droop coefficient, the updated reactive power droop coefficient is obtained.

[0017] Furthermore, the expression corresponding to the virtual damping adaptive control method is:

[0018] ;

[0019] The active power reference value, active power sample value, VSG frequency steady-state value, grid frequency, and virtual damping coefficient after virtual damping adaptive control are calculated and the VSG power angle is output; the corresponding expression is:

[0020] ;

[0021] ;

[0022] in, The rate of change of the work angle; This refers to the change in the angular frequency of the VSG. This represents the steady-state value of the VSG frequency. The power grid frequency;

[0023] The rate of change of VSG angular frequency; This is the virtual inertia coefficient; This is a reference value for active power. This is the active power sample value; This refers to the proportional coefficient of the proportional branch in virtual damping adaptive control. This refers to the proportional coefficient of the integral branch in virtual damped adaptive control; Differentiate the VSG output angular frequency;

[0024] The virtual damping coefficient is the result of virtual damping adaptive control. This is the virtual damping coefficient;

[0025] and These are the common coupling point voltage and the grid voltage, respectively. For the reactance of the transmission line, Let be the VSG angle, and sin() be the sine function.

[0026] Furthermore, the calculation expressions for the gain coefficient of the upper limit AC voltage and the upper limit AC voltage are as follows:

[0027] ;

[0028] in, The gain coefficient is the upper limit of the AC voltage. The gain coefficient is the lower limit AC voltage. This is the upper limit coefficient for AC voltage. This is the lower limit coefficient for AC voltage;

[0029] R is the voltage at the common coupling point; g For grid resistance; L g For mains inductance; This is the angular frequency of the power grid.

[0030] 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.

[0031] The steps involve selecting upper and lower limit switching values ​​based on the grid voltage, and then, based on the gain coefficient of the upper AC voltage, the gain coefficient of the lower AC voltage, the upper and lower switching values, and the reactive power droop coefficient setting, obtaining the updated reactive power droop coefficient. Specifically:

[0032] 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.

[0033] When the grid voltage is higher than the upper limit, the upper limit switch value is 1, and the first voltage deviation is multiplied by the gain coefficient of the upper limit AC voltage as the reactive power droop coefficient compensation amount.

[0034] When the AC voltage is lower than the lower limit, the value of the lower limit switch is 1, and the second voltage deviation is multiplied by the gain coefficient of the lower limit AC voltage as the reactive power droop coefficient compensation amount.

[0035] When the grid voltage is higher than the upper limit or lower than the lower limit, the reactive power droop coefficient compensation is added to the reactive power droop coefficient setting value to obtain the updated reactive power droop coefficient.

[0036] Furthermore, the first voltage deviation is the result of multiplying the common coupling point voltage by the AC voltage upper limit coefficient and then subtracting it from the grid voltage processed by the low-pass filter;

[0037] The second voltage deviation is the result of multiplying the common coupling point voltage by the AC voltage lower limit coefficient and then subtracting it from the grid voltage processed by the low-pass filter.

[0038] Furthermore, the calculation expression for the reactive power droop coefficient compensation is as follows:

[0039] ;

[0040] in, This is the compensation amount for reactive power droop coefficient; The gain coefficient is the upper limit of the AC voltage. The gain coefficient is the lower limit AC voltage. This is the upper limit coefficient for AC voltage; This is the lower limit coefficient for AC voltage; The voltage at the common coupling point; This refers to the grid voltage. This is the upper limit of the switch quantity; This is the lower limit of the switching quantity; This represents the transfer function of a low-pass filter in the complex frequency domain.

[0041] Furthermore, when the grid voltage is higher than the upper limit or lower than the lower limit, the updated formula for calculating the reactive power droop factor is as follows:

[0042] ;

[0043] The set value for the reactive power droop factor. This is the updated reactive power droop coefficient.

[0044] This 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:

[0045] The low-voltage fault ride-through control module is used for low-voltage fault ride-through control. The specific process is as follows:

[0046] The obtained VSG angular frequency change, the differential of VSG output angular frequency, and the 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.

[0047] The active power reference value, active power sample value, VSG frequency steady-state value, grid frequency, and virtual damping coefficient after virtual damping adaptive control are calculated and the VSG power angle is output.

[0048] The high-voltage fault ride-through control module is used for high-voltage fault ride-through control. The specific process is as follows:

[0049] Obtain the reactive power droop factor setting value, common coupling point voltage, grid voltage, AC voltage upper limit factor, and AC voltage lower limit factor;

[0050] After the grid voltage is filtered, the gain coefficient of the upper limit AC voltage is obtained by calculating the voltage at the common coupling point and the upper limit coefficient of the AC voltage.

[0051] After the grid voltage is filtered, the gain coefficient of the lower limit AC voltage is obtained by calculating the voltage at the point of common coupling and the lower limit coefficient of the AC voltage.

[0052] Based on the magnitude of the grid voltage, the values ​​of the upper limit switch quantity and the lower limit switch quantity are selected. 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 set value of the reactive power droop coefficient, the updated reactive power droop coefficient is obtained.

[0053] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program to implement the steps of the cascading fault ride-through control method for the virtual synchronous generator.

[0054] The present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the cascading fault ride-through control method for the virtual synchronous generator.

[0055] Compared with the prior art, the present invention has the following beneficial technical effects:

[0056] This invention discloses a cascading fault ride-through control method for a virtual synchronous generator. It divides the low-voltage and high-voltage cascading fault ride-through process into two aspects: active power control and reactive power control. In active power control, dynamic damping control is proposed to suppress power angle divergence under low-voltage faults, and adaptive droop coefficient control is proposed to provide reactive power support under high-voltage faults. This invention employs a dual control mechanism, performing refined control on active and reactive power separately, improving the system's adaptability and stability under different fault conditions and overcoming the limitations of single control strategies in existing technologies. It achieves intelligent ride-through control of the virtual synchronous generator during grid voltage cascading faults, ensuring the safe operation and stability of the system during faults by rationally allocating active and reactive power. Therefore, the method proposed in this invention can effectively improve the stability of the virtual synchronous generator during grid voltage cascading faults. Attached Figure Description

[0057] Figure 1 This is a block diagram of a virtual damping adaptive control system.

[0058] Figure 2 When a power grid fault occurs, virtual damping adaptive control is adopted. Phase trajectory;

[0059] Figure 3 The VSG stability region is composed of different virtual inertia and virtual damping critical values;

[0060] Figure 4 The simulation curves are obtained from the stability analysis of virtual damped adaptive control.

[0061] Among them, (a) is Phase trajectory curve; (b) Figure shows the VSG power angle. The time-domain response curve;

[0062] Figure 5 This is the control block diagram for the reactive power control loop;

[0063] Figure 6 This is the block diagram for adaptive adjustment control of reactive power droop coefficient;

[0064] Figure 7 The simulation curves are obtained from the stability analysis of the adaptive adjustment control of reactive power droop coefficient.

[0065] Among them, (a) is Phase trajectory curve; (b) Figure is Time-domain response curve; (c) Figure is Time-domain response curve;

[0066] Figure 8Simulation waveforms comparing the performance of the control method of the present invention and the control method without the present invention under voltage cascading faults;

[0067] 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; and (e) shows the change of output frequency over time. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0069] The detailed description of the embodiments of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the figures and embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0070] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0071] Voltage cascading faults consist of two parts: low-voltage faults and high-voltage faults. 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.

[0072] This invention first introduces the relevant content of the active power control improvement method.

[0073] like Figure 1 The diagram shown is a virtual damping adaptive control block diagram. The present invention proposes a method that can dynamically adjust the virtual damping coefficient based on the change in VSG angular frequency and the derivative of the angular frequency. This method is used to suppress VSG power angle divergence during grid voltage faults, ensure VSG stability, and not affect VSG operation when the grid is normal.

[0074] like Figure 1 As shown, VSG power angle is used express, and It is the adjustment coefficient. It is a differential operator. Virtual damping adaptive control superimposes the VSG angular frequency change, the differential of the VSG output angular frequency, and the original virtual damping coefficient, dynamically adjusting the virtual damping coefficient according to different fault states to obtain the virtual damping coefficient after adaptive control. The characteristic of this control strategy is that it does not affect the VSG's virtual damping coefficient in steady state, but during faults, it dynamically adjusts the VSG's virtual damping coefficient according to the degree of grid voltage fault.

[0075] illustrate Figure 1 The corresponding process: The input to the low-voltage ride-through VSG damped adaptive control block diagram is the active power reference value. Active power sampling value Virtual damping coefficient after virtual damping adaptive control The output is the VSG power angle. ; This is the result of the summation of three intermediate variables, specifically the change in VSG frequency. Virtual damping coefficient and proportionality coefficient The product of, and the VSG output angular frequency With proportionality coefficient and differential operators The product of these is then superimposed. Subsequently, the virtual inertia coefficient is used. With integration Processing and comparing with the steady-state value of VSG frequency After superposition, then integration is performed. The VSG output power angle is obtained through processing. .

[0076] Specifically, such as Figure 1 As shown, the output signal expression can be derived from the virtual damping adaptive control block diagram as follows:

[0077] (1)

[0078] (2)

[0079] (3)

[0080] in, The rate of change of the work angle; This refers to the change in the angular frequency of the VSG. This represents the steady-state value of the VSG frequency. The power grid frequency;

[0081] The rate of change of VSG angular frequency; This is the virtual inertia coefficient; This is a reference value for active power. This is the active power sample value; This refers to the proportional coefficient of the proportional branch in virtual damping adaptive control. This refers to the proportional coefficient of the integral branch in virtual damped adaptive control; Differentiate the VSG output angular frequency;

[0082] The virtual damping coefficient is the result of virtual damping adaptive control. This is the virtual damping coefficient;

[0083] and These are the common coupling point voltage and the grid voltage, respectively. For the reactance of the transmission line, Let be the VSG angle, and sin() be the sine function.

[0084] When using formulas (1)-(3) to plot low-voltage grid faults, i.e. At that time, under virtual damping adaptive control The phase trajectory is as follows Figure 2 As shown.

[0085] Depend on Figure 2 It can be seen that, The phase trajectory stabilizes 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.

[0086] During a low-voltage power grid fault, i.e., when the grid voltage... When the output is reduced from 1 pu to 0.5 pu, the following is obtained: Figure 3 The stability region of the virtual synchronous generator is shown, composed of different critical values ​​of virtual inertia and virtual damping coefficient. Figure 3 It can be seen that when virtual inertia Increase to During the process, the virtual damping coefficient It will not increase. Exceeding... After that, if virtual inertia If it continues to increase, the virtual damping coefficient will... It also begins to increase, and the relationship is approximately linear. Dividing the entire region into stable and unstable regions, we can draw the following conclusions:

[0087] 1. If virtual inertia Increase the virtual damping coefficient The amount must be increased further, otherwise the VSG system risks instability. If the virtual inertia... Decrease the virtual damping coefficient No changes are needed.

[0088] 2. Virtual inertia No need to follow the virtual damping coefficient The virtual inertia increases with the increase of the physical inertia, but the virtual inertia... It must be in the virtual damping coefficient It decreases when it decreases.

[0089] The above analysis shows that, in order for the VSG system to remain stable, a sufficient virtual damping coefficient must be ensured. Virtual damping coefficient It plays a crucial role in maintaining the stability of the VSG system during oscillation.

[0090] When a low-voltage power grid fault occurs, a stability analysis of the virtual damped adaptive control is performed. and The effect on adaptive control of virtual damping coefficient is as follows: Figure 4 As shown, Figure (a) represents Phase trajectory curve, Figure (b) shows the VSG power angle. The time-domain response curve.

[0091] Without incorporating the virtual damping adaptive control method proposed in this invention, the VSG power angle... This can lead to divergence; and after incorporating the virtual damping adaptive control method proposed in this invention, and When the time is too short, VSG power angle Divergence can also occur, specifically as follows: Figure 4 The green and orange-red simulation curves are shown in the image.

[0092] like Figure 4 As shown in Figure (a), with and The increase, The stability of the phase trajectory gradually increases, and the oscillations continuously decrease; for example... Figure 4 As shown in Figure (b), with and The increase in VSG power angle The continuous decrease and movement away from the critical value indicate that the stability of the VSG system is gradually increasing.

[0093] The following section introduces relevant methods for improving reactive power control.

[0094] Figure 5 This is the control block diagram of the reactive power control loop, which adjusts the VSG output voltage through reactive power. The feedback loop uses the reactive power droop factor. To correct reactive power, this invention proposes an Adaptive Droop Coefficient Control (ADCC) method to improve reactive power and output voltage performance during cascading faults.

[0095] like Figure 5 As shown, the reactive power control loop completes reactive power control by taking the difference between the output voltage V and the voltage reference value V0, adjusting the ratio, and then feeding it back to the reactive power reference value Q0.

[0096] Figure 6 This is a block diagram of the adaptive adjustment control for a reactive power droop system. and These are the upper and lower limit coefficients for AC voltage, responsible for controlling the voltage limits at which adaptive regulation takes effect. The low-pass filter (LPF) filters out grid voltage. High-frequency components in the signal should be removed to avoid affecting the control effect. and These are the gain coefficients corresponding to the upper and lower limits of AC voltage in adaptive regulation control. This is the upper limit of the switch quantity. It is a lower limit switch quantity, used to represent the value of the grid voltage exceeding the upper or lower limit.

[0097] When the grid voltage When the value is between the lower limit and the upper limit, , , All are zero, and the reactive power droop factor equals the reactive power droop factor set value. .

[0098] When the grid voltage When the upper limit value is exceeded, the upper limit switch quantity is activated. Take 1, and multiply the first voltage deviation by As compensation amount for reactive power droop coefficient .

[0099] When the AC voltage is below the lower limit, the lower limit switch quantity... Take 1, and multiply the second voltage deviation by As compensation amount for reactive power droop coefficient .

[0100] reactive power droop coefficient compensation amount When the AC voltage is higher than the upper limit or lower than the lower limit, the reactive power droop factor setting is added. The reactive power droop factor is rationally allocated to improve AC voltage regulation performance during cascading faults. The updated expression for the reactive power droop factor is then: ;

[0101] in, (4)

[0102] This represents the transfer function of a low-pass filter (LPF) in the complex frequency domain.

[0103] Wherein, the first voltage deviation is the voltage at the common coupling point. With AC voltage upper limit coefficient After multiplication, it is then compared with the grid voltage processed by the low-pass filter (LPF). The result of the difference.

[0104] The second voltage deviation is the voltage at the common coupling point. With AC voltage lower limit coefficient After multiplication, it is then compared with the grid voltage processed by the low-pass filter (LPF). The result of the difference.

[0105] AC voltage upper limit coefficient With AC voltage lower limit coefficient It needs to be set according to the actual situation, and and It can be obtained from the following formula:

[0106] (5)

[0107] in, The gain coefficient of the upper limit AC voltage, The gain coefficient is the lower limit AC voltage. This is the upper limit coefficient for AC voltage. This is the lower limit coefficient for AC voltage; R is the voltage at the common coupling point; g It is the grid resistance; L g It is the inductance of the power grid; This is the angular frequency of the power grid.

[0108] The gain coefficient of the upper limit AC voltage and the upper limit AC voltage can be calculated by equation (4), and the stability analysis of the reactive power droop adaptive adjustment control can be performed.

[0109] like Figure 7 As shown in Figure (a), a stability analysis was performed on the adaptive adjustment control of the reactive power droop coefficient, resulting in the following figure: Phase trajectory curve, as shown in Figure (b) The time-domain response curve, as shown in Figure (c) Time-domain response curve.

[0110] Depend on Figure 7As can be seen from Figure (a), under different voltage variations, the reactive power droop coefficient adaptive control can significantly reduce the... Phase trajectory oscillation ensures stable operation of the VSG.

[0111] Depend on Figure 7 As can be seen from Figure (b), under different voltage variations, when using adaptive control of the reactive power droop coefficient, the VSG power angle... It will tend to stabilize over time.

[0112] Depend on Figure 7 As can be seen from Figure (c), under different voltage variations, the change in VSG angular frequency is as follows when using adaptive control of reactive power droop coefficient. It will tend to stabilize over time.

[0113] The cascading fault performance improvement method proposed in this invention serves as a fundamental approach to enhance the stability of the VSG during grid voltage cascading faults. With appropriate parameter design, it can ensure the VSG's continuous and stable operation during the fault process. However, the magnitude of grid voltage drops or surges is unpredictable, and traditional damping control only performs well under faults of specific voltage amplitudes and cannot change the output damping magnitude as the voltage fault changes. Therefore, traditional damping control cannot guarantee VSG stability under different voltage faults.

[0114] Figure 8 The control method of the present invention and the control method without the present invention are respectively used in voltage cascading faults. The simulation waveforms for performance comparison are shown below: (a) The grid voltage changes over time; (b) The active power changes over time; (c) The reactive power changes over time; (d) The power angle changes over time; (e) The output frequency changes over time. It can be seen that the system without the method proposed in this invention cannot guarantee the stable operation of the VSG during the low-voltage fault phase. At this time, the active power of the VSG changes significantly, and the VSG power angle continuously increases. However, by incorporating the control method proposed in this invention, the damping output can be adjusted according to different low-voltage fault degrees, ensuring the stable operation of the VSG during the low-voltage fault phase.

[0115] Meanwhile, in high-voltage faults, 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 voltage faults in complex power grids, the control method proposed in this invention can effectively improve the stability of VSG under voltage cascading faults.

[0116] This invention primarily analyzes low-voltage and high-voltage cascading faults as an example. These faults are generally caused by load switching during low-voltage faults or by the failure to promptly remove compensation capacitor banks during low-voltage faults. The research on low-voltage and high-voltage cascading faults is divided into two parts: the low-voltage fault stage and the high-voltage fault stage. The low-voltage fault stage focuses on improving stability, proposing dynamic damping control to enhance the stability of the VSG under low-voltage faults. The phase plane method is used to analyze the improvement effect, and the results show that dynamic damping control can effectively improve VSG stability during low-voltage faults. The high-voltage fault stage focuses on power overshoot and power oscillation, proposing virtual capacitor feedback control to reduce power overshoot and power oscillation, and enabling the VSG to absorb reactive power, helping the voltage at the fault point to recover. Finally, the phase plane method analysis shows that virtual capacitor feedback control effectively reduces power overshoot and oscillation during high-voltage faults.

[0117] This invention also discloses a cascading fault ride-through control system for a virtual synchronous generator, comprising:

[0118] The low-voltage fault ride-through control module is an active power control module. Specifically, it adopts a virtual damping adaptive control method to dynamically adjust the virtual damping coefficient and suppress the divergence of the virtual synchronous generator power angle during low-voltage faults in the power grid.

[0119] The high-voltage fault ride-through control module is a reactive power control module. Specifically, it adopts an adaptive adjustment control method for reactive power droop coefficient to adjust the reactive power droop coefficient of the virtual synchronous generator, thereby improving the reactive power and output voltage during cascading faults.

[0120] This invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a cascading fault-crossing control method for the virtual synchronous generator. The memory may include main memory, such as high-speed random access memory, or it 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, which may be an industry-standard architecture bus, a peripheral component interconnection standard bus, an extended industry-standard architecture bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory stores the program; specifically, the program may include program code, which includes computer operation instructions. The memory may include main memory and non-volatile memory, and provides instructions and data to the processor.

[0121] The present invention also discloses a computer-readable storage medium storing a computer program that, when executed by a processor, implements a cascading fault ride-through control method for the virtual synchronous generator. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory.

[0122] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) containing computer-usable program code.

[0123] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0124] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0125] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0126] 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, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for cascading fault ride-through control of 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 low-voltage fault ride-through control process is as follows: The obtained VSG angular frequency change, the differential of VSG output angular frequency, and the 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. The active power reference value, active power sample value, VSG frequency steady-state value, grid frequency, and virtual damping coefficient after virtual damping adaptive control are calculated and the VSG power angle is output. The high-voltage fault ride-through control process is as follows: Obtain the reactive power droop factor setting value, common coupling point voltage, grid voltage, AC voltage upper limit factor, and AC voltage lower limit factor; After the grid voltage is filtered, the gain coefficient of the upper limit AC voltage is obtained by calculating the voltage at the common coupling point and the upper limit coefficient of the AC voltage. After the grid voltage is filtered, the gain coefficient of the lower limit AC voltage is obtained by calculating the voltage at the point of common coupling and the lower limit coefficient of the AC voltage. Based on the magnitude of the grid voltage, the values ​​of the upper limit switch quantity and the lower limit switch quantity are selected. 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 set value of the reactive power droop coefficient, the updated reactive power droop coefficient is obtained.

2. The cascading fault ride-through control method for 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 sample value, VSG frequency steady-state value, grid frequency, and virtual damping coefficient after virtual damping adaptive control are calculated and the VSG power angle is output; the corresponding expression is: ； ； in, The rate of change of the work angle; This refers to the change in the angular frequency of the VSG. This represents the steady-state value of the VSG frequency. The power grid frequency; The rate of change of VSG angular frequency; This is the virtual inertia coefficient; This is a reference value for active power. This is the active power sample value; This refers to the proportional coefficient of the proportional branch in virtual damping adaptive control. This refers to the proportional coefficient of the integral branch in virtual damped adaptive control; Differentiate the VSG output angular frequency; The virtual damping coefficient is the result of virtual damping adaptive control. This is the virtual damping coefficient; and These are the common coupling point voltage and the grid voltage, respectively. For the reactance of the transmission line, Let be the VSG angle, and sin() be the sine function.

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

4. The cascading fault ride-through control method for a virtual synchronous generator according to claim 1, characterized in that, During high-voltage fault ride-through control, it is also necessary to obtain the lower and upper limits of the grid voltage. The steps involve selecting upper and lower limit switching values ​​based on the grid voltage, and then, based on the gain coefficient of the upper AC voltage, the gain coefficient of the lower AC voltage, the upper and lower switching values, and the reactive power droop coefficient setting, obtaining the updated reactive power droop coefficient. 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 1, and the first voltage deviation is multiplied by the gain coefficient of the upper limit AC voltage as the reactive power droop coefficient compensation amount. When the AC voltage is lower than the lower limit, the value of the lower limit switch is 1, and the second voltage deviation is multiplied by the gain coefficient of the lower limit AC voltage as the reactive power droop coefficient compensation amount. When the grid voltage is higher than the upper limit or lower than the lower limit, the reactive power droop coefficient compensation is added to the reactive power droop coefficient setting value to obtain the updated reactive power droop coefficient.

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

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

7. The cascading fault ride-through control method for 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 formula for calculating the reactive power droop factor is: ； The set value for the reactive power droop factor. This is the updated reactive power droop coefficient.

8. A cascading fault ride-through control system for a virtual synchronous generator, characterized in that, Includes 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 for low-voltage fault ride-through control. The specific process is as follows: The obtained VSG angular frequency change, the differential of VSG output angular frequency, and the 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. The active power reference value, active power sample value, VSG frequency steady-state value, grid frequency, and virtual damping coefficient after virtual damping adaptive control are calculated and the VSG power angle is output. The high-voltage fault ride-through control module is used for high-voltage fault ride-through control. The specific process is as follows: Obtain the reactive power droop factor setting value, common coupling point voltage, grid voltage, AC voltage upper limit factor, and AC voltage lower limit factor; After the grid voltage is filtered, the gain coefficient of the upper limit AC voltage is obtained by calculating the voltage at the common coupling point and the upper limit coefficient of the AC voltage. After the grid voltage is filtered, the gain coefficient of the lower limit AC voltage is obtained by calculating the voltage at the point of common coupling and the lower limit coefficient of the AC voltage. Based on the magnitude of the grid voltage, the values ​​of the upper limit switch quantity and the lower limit switch quantity are selected. 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 set value of the reactive power droop coefficient, the updated reactive power 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, it implements the steps of the cascading fault ride-through control method for the virtual synchronous generator as described in any one of claims 1 to 7.

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

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