Methods and systems for improving the adaptability of flexible loop closing devices to power grid phase transitions

Abstract

This invention provides a method and system for improving the adaptability of flexible loop-closing devices to grid phase jumps, belonging to the field of grid control technology. The invention samples the voltage and current at the PCC (Power Control Center) to calculate the jump compensation phase, inputs this phase into the active-frequency compensation control module, and calculates the actual output active and reactive power of the three-phase grid-connected inverter. The active power is input into the active-frequency compensation control module to obtain an internal potential phase reference, which is then used by the reactive-voltage control module to obtain an internal potential amplitude reference. Finally, the internal potential phase reference and amplitude reference are combined to generate a modulation wave. After passing through the SVPWM modulation module, pulse trigger signals for each switch in the main circuit of the three-phase grid-connected inverter are obtained. This invention suppresses instantaneous inrush currents during grid phase jumps, improves the adaptability of flexible loop-closing devices to grid phase jumps, and ensures the safety of the device.

Description

Technical Field

[0001] This invention belongs to the field of power grid control technology and relates to a method and system for improving the ability of flexible loop closing devices to adapt to power grid phase jumps. Background Technology

[0002] This invention is an improvement based on the Chinese invention patent application "Control method and system for simulated synchronous condenser operation of new energy grid-connected inverter" (application publication number CN117240117A, application publication date December 15, 2023). The purpose is to suppress overcurrent during grid short-circuit faults and ensure the safe operation of the flexible loop-closing device.

[0003] The virtual synchronous generator control of flexible loop-closing devices, by simulating the basic behavior of synchronous generators, can provide frequency and voltage support for the connected network, making it a good solution for improving the operational capacity of distribution networks. When a grid-side short-circuit fault occurs, causing a phase jump in the voltage at the point of common coupling (PCC), the internal potential of the virtual synchronous generator cannot respond instantaneously to the phase jump because the active frequency link in the conventional virtual synchronous generator's internal potential control uses integral control. This causes the phase difference between the voltage at the PCC and the internal potential to increase instantaneously. The maximum voltage deviation caused by this phase difference reaches twice the peak grid voltage. Due to the small filter impedance, the instantaneous current caused by the voltage is difficult to control, easily leading to safety accidents. To suppress overcurrent during grid short-circuit faults and ensure the safe operation of flexible loop-closing devices, the main current solutions are to use voltage amplitude control based on the severity of the fault or to add virtual resistance control to limit the fault current. However, these two methods do not consider that changes in the external grid topology caused by grid faults can also cause voltage phase jumps at the point of common coupling (PCC). Summary of the Invention

[0004] The technical solution of this invention is used to solve the problem of how to improve the ability of flexible loop-closing devices to adapt to power grid phase jumps.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0006] This invention provides a method for improving the adaptability of flexible loop closing devices to power grid phase jumps, comprising: The three-phase voltage u at PCC s Output three-phase current i s The input is fed into the power calculation module for power calculation, thereby obtaining the actual active power P transmitted to the power grid. e and reactive power Q e ; Active power P eThe signal is sent to the active-frequency compensation control module to obtain the generated phase θ0 of the virtual synchronous generator; The three-phase voltage u at PCC s The input is fed into the phase jump calculation module. When the voltage amplitude at the PCC drops to the threshold, the phase jump compensation θ is calculated. c The calculated jump compensation phase θ c The internal potential phase reference θ is obtained by superimposing the generated phase θ0 of the virtual synchronous generator; The voltage amplitude U at PCC is obtained by amplitude calculation. s Then the voltage amplitude U s With reactive power Q e The signal is transmitted to the reactive power-voltage control module to generate an internal potential amplitude reference E; The internal potential phase reference θ and internal potential amplitude reference E are input into the internal potential generation module to obtain a three-phase sinusoidal internal potential modulation wave e. abc ; The three-phase sinusoidal internal potential modulation wave e abc The pulse trigger signals for each switching transistor in the main circuit of the three-phase grid-connected inverter are sent to the SVPWM modulation module.

[0007] Furthermore, the phase jump compensation θ c The calculation method is as follows: Define a reference voltage vector U with the same frequency as the three-phase voltage at PCC, but with arbitrary phase. ref Let AB be the vector. Before the phase jump, the terminal point of the three-phase voltage at PCC is C0. After the jump, its phase jumps to C1. That is, the jump angle of the three-phase voltage at PCC is φ1-φ0, where φ0 and φ1 are the three-phase voltage vectors U and U at PCC before the jump, respectively. s0 and the three-phase voltage vector U at PCC after the transition s1 The angle between the vector AB and the phase θ of the jump compensation. c The calculation is as follows:

[0008] Where d0 represents U s0 The component projected onto the d-axis, q0 represents U s0 The component projected onto the q-axis, d1, represents U. s1 The component projected onto the d-axis, q1 represents U s1 The component projected onto the q-axis has the vector AB in the positive direction of the d-axis, and the vector AB rotated 90° counterclockwise to become the positive direction of the q-axis.

[0009] Furthermore, the control equations of the active power-frequency compensation control module are as follows:

[0010] Among them, P ref For reference active power, P e This refers to the actual active power; J, D p These represent the moment of inertia and the active droop coefficient, respectively; θ is the internal potential phase reference, θ c For the phase jump compensation, θ0 is the generation phase of the virtual synchronous generator, and ω and ω n These represent the actual and rated values ​​of the angular frequency, respectively; k is the slope for compensating for phase attenuation during the linear attenuation phase.

[0011] Furthermore, the actual active power P calculated in the power calculation module... e and reactive power Q e The calculation formula is as follows:

[0012]

[0013] in, , , These are the three-phase voltages output from the main circuit of the three-phase grid-connected inverter; , , These are the three-phase currents output from the main circuit of the three-phase grid-connected inverter.

[0014] Furthermore, the control equation of the reactive power-voltage control module is as follows:

[0015]

[0016] in, , U represents the voltage components of the three-phase voltage output from the main circuit of a three-phase grid-connected inverter in the αβ coordinate system. s This represents the voltage amplitude.

[0017] Furthermore, the formula for calculating the internal potential amplitude reference is as follows:

[0018] Where E is the reference value for the internal potential amplitude, and K q D is the reactive inertia coefficient. q U is the reactive power droop factor. N Q is the reference amplitude of the phase voltage output from the main circuit of the three-phase grid-connected inverter. ref For reference reactive power.

[0019] Furthermore, the internal potential generation module obtains a three-phase sinusoidal internal potential modulation wave e abc The calculation expression is:

[0020] Where θ is the internal potential phase reference.

[0021] This invention also provides a three-phase grid-connected inverter control system, comprising: a three-phase grid-connected inverter main circuit and a virtual synchronous generator control unit; the three-phase grid-connected inverter main circuit includes: a DC power supply U dc Three-phase inverter, three-phase LC filter (L f C f DC power supply U dc The DC input of the three-phase inverter is connected to one end of the three-phase LC filter, and the other end of the three-phase LC filter is connected to the equivalent line reactance L. g One end is connected, and the equivalent line reactance L g The other end is connected to the power grid u g Connected; The virtual synchronous generator control unit includes: a power calculation module, an active power-frequency compensation control module, a reactive power-voltage control module, an internal potential generation module, an SVPWM modulation module, and a phase jump calculation module; The three-phase voltage u at sampling point PCC s Output three-phase current i s The input is fed into the power calculation module for power calculation, thereby obtaining the actual active power P transmitted to the power grid. e and reactive power Q e ; active power P e The signal is transmitted to the active-frequency compensation control module to obtain the generated phase θ0 of the virtual synchronous generator; the three-phase voltage u at the PCC is then converted. s The input is sent to the phase jump calculation module. When the voltage amplitude at the PCC drops to a set threshold, the phase jump compensation θ is calculated. c The calculated jump compensation phase θ c The internal potential phase reference θ is obtained by superimposing the generated phase θ0 of the virtual synchronous generator; the voltage amplitude U is obtained by calculating the amplitude of the three-phase voltage at PCC. s Then the voltage amplitude U s With reactive power Q e The data is fed into the reactive power-voltage control module to generate the internal potential amplitude reference E; the internal potential phase reference θ and the internal potential amplitude reference E are then input into the internal potential generation module to obtain the three-phase sinusoidal internal potential modulation wave e. abc ; modulate the three-phase sinusoidal internal potential wave e abcThe pulse trigger signals for each switching transistor in the main circuit of the three-phase grid-connected inverter are sent to the SVPWM modulation module.

[0022] The present invention also provides an electronic device, including a memory and a processor, wherein the memory is used to store a program that supports the processor in executing the above-described method for improving the ability of a flexible loop-closing device to adapt to grid phase transitions, and the processor is configured to execute the program stored in the memory.

[0023] The present invention also provides a storage medium storing a computer program, which, when executed by a processor, performs the steps of the method described above for improving the ability of a flexible loop-closing device to adapt to grid phase transitions.

[0024] The beneficial effects of this invention are as follows: This invention calculates the jump compensation phase θ by sampling the voltage and current at the PCC. c The active and reactive power of the three-phase grid-connected inverter are calculated by inputting the active-frequency compensation control module. The active power is then input into the active-frequency compensation control module to obtain the internal potential phase reference. The reactive-voltage control module then obtains the internal potential amplitude reference. Finally, the internal potential phase reference and amplitude reference are combined to generate a modulation wave. After passing through the SVPWM modulation module, the pulse trigger signals of each switch in the main circuit of the three-phase grid-connected inverter are obtained. When a grid-side short-circuit fault causes a voltage phase jump at the PCC, this invention adds phase compensation measures to directly compensate for the jump phase in the internal potential, suppressing the instantaneous inrush current during the grid phase jump, improving the flexible loop-closing device's ability to adapt to grid phase jumps, and ensuring the safety of the device. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the three-phase grid-connected inverter control system used in the method of this invention; Figure 2 This is a vector diagram of the calculation method for the jump compensation phase in the method of the present invention; Figure 3 This is a control block diagram of the active-frequency compensation control module of the method of the present invention; Figure 4 This is a control block diagram of the reactive power-voltage control module of the method of the present invention; Figure 5 This is a schematic diagram of the internal potential generation module in the method of the present invention; Figure 6 This is a schematic diagram of the state transition of the method of the present invention; Figure 7 This is a schematic diagram of the program flow of the method of the present invention; Figure 8This is a simulation waveform diagram of the virtual synchronous generator jump compensation phase of the method of the present invention; Figure 9 This is a simulation waveform of the output current amplitude of the virtual synchronous generator according to the method of the present invention; Figure 10 This is a simulation waveform of the active power output of the virtual synchronous generator according to the method of the present invention; Figure 11 This is a simulation waveform of the reactive power output of the virtual synchronous generator according to the method of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 like Figure 1 As shown, the three-phase grid-connected inverter control system used in the method for improving the adaptability of the flexible loop-connected device to grid phase jumps according to the present invention includes: a three-phase grid-connected inverter main circuit and a virtual synchronous generator control unit.

[0028] The main circuit of the three-phase grid-connected inverter includes: a DC power supply U dc Three-phase inverter, three-phase LC filter (L f C f DC power supply U dc The DC input of the three-phase inverter is connected to one end of the three-phase LC filter, and the other end of the three-phase LC filter is connected to the equivalent line reactance L. g One end is connected, and the equivalent line reactance L g The other end is connected to the power grid u g Connected.

[0029] The virtual synchronous generator control unit includes: a power calculation module, an active power-frequency compensation control module, a reactive power-voltage control module, an internal potential generation module, an SVPWM modulation module, and a phase jump calculation module; it calculates the three-phase voltage u at the sampling point PCC. s Output three-phase current i s The input is fed into the power calculation module for power calculation, thereby obtaining the actual active power P transmitted to the power grid. e and reactive power Q e; active power P e The signal is transmitted to the active-frequency compensation control module to obtain the generated phase θ0 of the virtual synchronous generator; the three-phase voltage u at the PCC is then converted. s The input is sent to the phase jump calculation module. When the voltage amplitude at the PCC drops to a set threshold (e.g., the set threshold is 0.9U), the input is processed. s When the jump compensation phase θ is calculated, the calculation begins. c The calculated jump compensation phase θ c The internal potential phase reference θ is obtained by superimposing the generated phase θ0 of the virtual synchronous generator; the voltage amplitude U is obtained by calculating the amplitude of the three-phase voltage at PCC. s Then the voltage amplitude U s With reactive power Q e The data is fed into the reactive power-voltage control module to generate the internal potential amplitude reference E; the internal potential phase reference θ and the internal potential amplitude reference E are then input into the internal potential generation module to obtain the three-phase sinusoidal internal potential modulation wave e. abc ; modulate the three-phase sinusoidal internal potential wave e abc The pulse trigger signals for each switching transistor in the main circuit of the three-phase grid-connected inverter are sent to the SVPWM modulation module.

[0030] like Figure 2 As shown, the jump compensation phase θ c The calculation method is as follows: Define a reference voltage vector U with the same frequency as the three-phase voltage at PCC, but with arbitrary phase. ref ,like Figure 2 The three-phase voltage at PCC has a mid-vector AB. Before the phase jump, its terminal point is C0. After the jump, its phase jumps to C1. That is, the jump angle of the three-phase voltage at PCC is φ1-φ0, where φ0 and φ1 are the three-phase voltage vectors U and C0 at PCC before the jump, respectively. s0 and the three-phase voltage vector U at PCC after the transition s1 The angle between the vector AB and the phase θ of the jump compensation. c It can be calculated as follows:

[0031] Where d0 represents U s0 The component projected onto the d-axis, q0 represents U s0 The component projected onto the q-axis, d1, represents U. s1 The component projected onto the d-axis, q1 represents U s1 The component projected onto the q-axis has the vector AB in the positive direction of the d-axis, and the vector AB rotated 90° counterclockwise to become the positive direction of the q-axis.

[0032] like Figure 3As shown, the control equations of the active power-frequency compensation control module are as follows:

[0033] Among them, P ref For reference active power, P e This refers to the actual active power; J, D p These represent the moment of inertia and the active droop coefficient, respectively; θ is the internal potential phase reference, θ c For the phase jump compensation, θ0 is the generation phase of the virtual synchronous generator, and ω and ω n These represent the actual and rated values ​​of the angular frequency, respectively; k is the slope of the phase attenuation compensation during the linear attenuation phase (state=3), at which point the phase attenuation will result in a power of D due to phase changes. p The power increment of k, therefore the compensation power is -D p k.

[0034] Figure 3 In the diagram, switch S1 represents the power compensation start switch. During the linear decay phase of the compensation phase (state=3), switch S1 switches to position 1, and during other phases, switch S1 switches to position 0.

[0035] The actual active power P calculated in the power calculation module e and reactive power Q e The calculation formula is as follows:

[0036]

[0037] in, , , These are the three-phase voltages output from the main circuit of the three-phase grid-connected inverter; , , These are the three-phase currents output from the main circuit of the three-phase grid-connected inverter.

[0038] The control equation for the reactive power-voltage control module is:

[0039]

[0040] in, , U represents the voltage components of the three-phase voltage output from the main circuit of a three-phase grid-connected inverter in the αβ coordinate system. s This represents the voltage amplitude.

[0041] like Figure 4As shown, the formula for calculating the internal potential amplitude reference is as follows:

[0042] Among them, K q D is the reactive inertia coefficient. q U is the reactive power droop factor. N Q is the reference amplitude of the phase voltage output from the main circuit of the three-phase grid-connected inverter. ref For reference reactive power.

[0043] like Figure 5 As shown, the internal potential generation module obtains a three-phase sinusoidal internal potential modulation wave e abc The calculation expression is:

[0044] Where E is the internal potential amplitude reference and θ is the internal potential phase reference.

[0045] like Figure 6 The diagram shown is a state transition schematic of the method for improving the adaptability of the flexible loop-closing device to power grid phase jumps according to the present invention. The entire process consists of multiple discrete states, and orderly state transitions are achieved based on input conditions and internal state variables.

[0046] After system initialization, it is in an idle state, where the input phase φ represents the voltage vector at PCC and the reference voltage vector U. ref The real-time phase, when the voltage amplitude U at PCC is detected. s Signal T is triggered after the fall reaches a set threshold. trig When the edge change begins, the system enters the edge detection and judgment phase. If the current state is not latched (i.e., state ≠ 4), a latching operation is performed and the dynamic compensation process is initiated; otherwise, the system maintains the current state to avoid erroneous actions caused by repeated triggering.

[0047] Once successfully latched, the system sequentially undergoes a four-stage compensation process: dynamic compensation stage (state=1), fixed compensation stage (state=2), linear decay stage (state=3), and completion state (state=4). After entering the completion state, the latch is released, and the system enters the idle state.

[0048] Dynamic compensation phase (state=1): The output compensation value is dynamically adjusted based on the real-time phase error. This phase is the core of phase jump compensation, its main goal being to respond quickly to instantaneous phase jumps and provide accurate phase compensation for the internal potential of the virtual synchronous generator. During this process, the system dynamically adjusts the output compensation value based on the real-time monitored phase error to quickly correct overcurrent problems caused by phase jumps and effectively eliminate power oscillations caused by phase mismatch. The efficient operation of this phase is crucial for maintaining system stability.

[0049] Fixed compensation phase (state=2): Maintains a constant compensation amount for a set time period to ensure stable response; the fixed compensation phase is designed to prevent a new round of power oscillations that may be caused by constantly changing phase compensation. In this phase, the system maintains a constant compensation amount for a set time period, which not only helps stabilize the system response but also lays the foundation for the subsequent linear decay phase.

[0050] Linear attenuation phase (state=3): The compensation value decreases linearly to zero over time, achieving a smooth transition. The main purpose of the linear attenuation phase is to smoothly exit phase compensation, specifically the phase jump compensation phase. Power compensation is performed in the active-frequency compensation control module to prevent power changes caused by the exit of the phase jump compensation phase, thus avoiding unnecessary impact on the system's active power. During this process, the compensation value gradually decreases linearly to zero over time, creating a natural transition effect. Notably, the corresponding compensation power can be calculated based on the slope of the linear attenuation of phase compensation during this phase stage to compensate for the power increment generated during the linear jump, thereby ensuring the continuity and accuracy of the entire compensation process.

[0051] Completion State (state=4): The compensation process is complete, and the system is ready to release the latch and return to the initial state. The completion state signifies the end of the current phase compensation cycle. In this state, the system has completed the entire process from phase detection to compensation and smooth exit, and is ready to release the latch mechanism to re-enter the idle state and wait for the next trigger signal. This state ensures that the system can recover to the initial state after undergoing a complete phase compensation process, ready to handle new phase transition events, guaranteeing the system's cyclic availability and long-term stability.

[0052] like Figure 7 The diagram shown is a flowchart illustrating the method for improving the adaptability of the flexible loop-closing device to grid phase transitions according to the present invention. This flowchart uses the state variable `state` as the core controller, and detects external trigger signals T. trig Edge changes to achieve phase jump compensation θ cThe process of dynamic compensation, fixed output, linear attenuation and reset of the signal.

[0053] The entire process is divided into five main states (0~4), each state corresponding to a specific compensation strategy and time control mechanism, as follows: State 0: Initial / Ready State (state=0) Condition: The system enters this state after startup or after completing a full compensation cycle.

[0054] Function: Input phase φ represents the voltage vector at PCC and the reference voltage vector U. ref Real-time phase; initialize all internal variables; continuously receive and buffer the voltage vector at PCC and the reference voltage vector U. ref The real-time phase φ = arctan(d / q) is transferred to the circular buffer φ. pre [m]; Output compensated phase θ c =0; Setting the variable trigger_latched to 0 allows subsequent triggered events to be responded to.

[0055] State transition condition: When a change in the edge of the trigger signal is detected and it is not latched, enter state 1; otherwise, maintain the current state and wait for a trigger.

[0056] State 1: Dynamic Compensation Phase (state=1) Core operations: Calculate the phase reference value φ0: take the average phase value of the set number of points within the window before triggering; prevent repeated triggering; set the latch variable trigger latched=1; start dynamic compensation output: θ c =φ-φ0; Record each output to θ c_init A buffer is used for subsequent averaging calculations.

[0057] State transition: If counter n <N initial Continue to implement dynamic compensation; reach N initial Then, it enters state 2.

[0058] State 2: Fixed Compensation Phase (state=2) Core operation: Calculate the fixed compensation value θ using the average of the most recent r historical data points. initial for mean(θ) c_init [r]), output fixed compensation θ c =θ initial .

[0059] State transition: If counter n <N hold Continue to perform dynamic compensation; reach N hold Then, it enters state 3.

[0060] State 3: Linear decay phase (state=3) Core functions and operations: Enables smooth exit of compensation values, avoiding abrupt changes that could affect system stability; the attenuation coefficient decreases linearly, and the linear attenuation time can be determined by the set number of counting points and the sampling frequency f. s Determined, represented as: T decay =(N decay -N hold ) / f s Output attenuation compensation phase θ c =θ initial (N) decay -n) / (N decay -N hold ).

[0061] State transition: If counter n <N decay Continue with linear decay; until N is reached. decay Then, it enters state 4.

[0062] State 4: Complete / Ready Phase (state=4) Core functions: Stop compensation output, clear the relevant counter n and clear the latch variable trigger_latched.

[0063] State transition: If a rising edge of the trigger signal is detected again, the system can re-enter state 1; otherwise, it will maintain the current state and wait for the next trigger.

[0064] Edge detection and reset mechanism: rising edge detection (T trig =0→1), at which point the first dynamic compensation is triggered; it only takes effect when trigger_latched=0 to prevent false triggering. Falling edge detection (T trig =1→0), which is effective when state=4, indicating that the fault has been cleared; the second dynamic compensation is started, and the new φ0 is calculated using the historical data before the trigger; this reflects the "two-stage compensation" characteristic, that is, the occurrence and clearing of the fault need to be compensated independently.

[0065] Simulation verification In the simulation, the grid connection condition is set to a given active power command P. ref =500kW, reactive power command Q ref= 0var. The main circuit parameters and control parameters of the three-phase grid-connected inverter are set as follows: DC voltage is 700V, and the rated phase voltage amplitude is referenced from U. N 256V, filter inductor L f =150μH, filter capacitor C f =600μF, equivalent inductance of the grid-side line L g =50μH, rated grid frequency is 50Hz. Active power droop factor Dp and reactive damping coefficient D q The values ​​are 79442 and 20000 respectively, and the virtual moment of inertia J is 0.3 kg. m 2 reactive inertia coefficient K q It is 318.

[0066] Under the above simulation parameters, the following results were obtained: Figures 8 to 11 The simulation waveform diagram of the phase jump compensation control of the virtual synchronous generator is shown. During the period from 0 to 0.2s, it is in normal grid-connected operation. At the time of 0.2s, a short circuit fault occurs, resulting in voltage drop and phase jump. During the period from 0.2 to 0.7s, it is in short circuit fault operation. At the time of 0.7s, fault recovery is performed. During the period from 0.7 to 2s, it is in normal grid-connected operation.

[0067] Figure 8 This is a simulation waveform diagram of the phase jump compensation for a virtual synchronous generator. The compensation phase occurs when a short-circuit fault occurs at 0.2s. From 0.2-0.21s, it is in the dynamic compensation phase (state=1), where real-time phase compensation occurs. From 0.21-0.31s, it is in the fixed compensation phase (state=2), where the fixed phase compensation is calculated to be -57.7 degrees. From 0.31-0.51s, it is in the linear decay phase (state=3), gradually decaying the fixed compensation phase value to 0 degrees. From 0.51-0.7s, it is in the completion / ready phase phase (state=4), where relevant variables are cleared to 0, preparing for the next phase jump. Fault recovery occurs at 0.7s, at which point the compensation phase is repeated, with a compensated phase of 57.5 degrees.

[0068] Figure 9 This is a simulation waveform of the output current amplitude of a virtual synchronous generator. Comparing the per-unit values ​​of the output current amplitude with and without phase compensation, the instantaneous per-unit value of the output current amplitude after phase compensation during the short-circuit fault at 0.2s decreases from 4.44 pu to 2.36 pu. During the fault recovery at 0.7s, the instantaneous per-unit value of the output current amplitude after phase compensation decreases from 4.18 pu to 2.27 pu.

[0069] Figure 10 This is a simulation waveform of the active power output of a virtual synchronous generator. Comparing the per-unit values ​​of the active power output with and without phase compensation, the instantaneous per-unit value of the active power output after phase compensation during the 0.2s short-circuit fault period decreases from 2.47 pu to 1.74 pu. During the 0.7s fault recovery period, the instantaneous per-unit value of the active power output after phase compensation decreases from -3.56 pu to -0.95 pu.

[0070] Figure 11 This is a simulation waveform of the reactive power output of a virtual synchronous generator. Comparing the per-unit values ​​of the reactive power output with and without phase compensation, the instantaneous per-unit value of the reactive power output after phase compensation during the 0.2s short-circuit fault period decreases from -1.70 pu to -0.85 pu. During the 0.7s fault recovery period, the instantaneous per-unit value of the reactive power output after phase compensation decreases from 3.66 pu to 2.32 pu.

[0071] Example 2 An electronic device includes a memory and a processor, the memory being used to store a program that supports the processor in executing the method for improving the adaptability of a flexible loop-closing device to grid phase transitions as described in Embodiment 1, the processor being configured to execute the program stored in the memory.

[0072] Example 3 A storage medium storing a computer program, which, when executed by a processor, performs the steps of the method for improving the ability of a flexible loop-closing device to adapt to grid phase jumps as described in Embodiment 1.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the adaptability of a flexible loop-closing device to power grid phase transitions, characterized in that, include: The three-phase voltage u at PCC s Output three-phase current i s The input is fed into the power calculation module for power calculation, thereby obtaining the actual active power P transmitted to the power grid. e and reactive power Q e ; Active power P e The signal is sent to the active-frequency compensation control module to obtain the generated phase θ0 of the virtual synchronous generator; The three-phase voltage u at PCC s The input is fed into the phase jump calculation module. When the voltage amplitude at the PCC drops to the threshold, the phase jump compensation θ is calculated. c The calculated jump compensation phase θ c The internal potential phase reference θ is obtained by superimposing the generated phase θ0 of the virtual synchronous generator; The voltage amplitude U at PCC is obtained by amplitude calculation. s Then the voltage amplitude U s With reactive power Q e The signal is transmitted to the reactive power-voltage control module to generate an internal potential amplitude reference E; The internal potential phase reference θ and internal potential amplitude reference E are input into the internal potential generation module to obtain a three-phase sinusoidal internal potential modulation wave e. abc ; The three-phase sinusoidal internal potential modulation wave e abc The pulse trigger signals for each switching transistor in the main circuit of the three-phase grid-connected inverter are sent to the SVPWM modulation module.

2. The method for improving the adaptability of a flexible loop-closing device to power grid phase jumps according to claim 1, characterized in that, The jump compensation phase θ c The calculation method is as follows: Define a reference voltage vector U with the same frequency as the three-phase voltage at PCC, but with arbitrary phase. ref Let AB be the vector. Before the phase jump, the terminal point of the three-phase voltage at PCC is C0. After the jump, its phase jumps to C1. That is, the jump angle of the three-phase voltage at PCC is φ1-φ0, where φ0 and φ1 are the three-phase voltage vectors U and U at PCC before the jump, respectively. s0 and the three-phase voltage vector U at PCC after the transition s1 The angle between the vector AB and the phase θ of the jump compensation. c The calculation is as follows: Where d0 represents U s0 The component projected onto the d-axis, q0 represents U s0 The component projected onto the q-axis, d1 represents U s1 The component projected onto the d-axis, q1 represents U s1 The component projected onto the q-axis has the vector AB in the positive direction of the d-axis, and the vector AB rotated 90° counterclockwise to become the positive direction of the q-axis.

3. The method for improving the adaptability of a flexible loop-closing device to power grid phase transitions according to claim 1, characterized in that, The control equations of the active power-frequency compensation control module are as follows: Among them, P ref For reference active power, P e This refers to the actual active power; J, D p These represent the moment of inertia and the active droop coefficient, respectively; θ is the internal potential phase reference, θ c For the phase jump compensation, θ0 is the generation phase of the virtual synchronous generator, and ω and ω n These represent the actual and rated values ​​of the angular frequency, respectively; k is the slope for compensating for phase attenuation during the linear attenuation phase.

4. The method for improving the adaptability of a flexible loop-closing device to power grid phase jumps according to claim 1, characterized in that, The actual active power P calculated in the power calculation module. e and reactive power Q e The calculation formula is as follows: in, , , These are the three-phase voltages output from the main circuit of the three-phase grid-connected inverter; , , These are the three-phase currents output from the main circuit of the three-phase grid-connected inverter.

5. The method for improving the adaptability of a flexible loop-closing device to power grid phase jumps according to claim 4, characterized in that, The control equation for the reactive power-voltage control module is: in, , U represents the voltage components of the three-phase voltage output from the main circuit of a three-phase grid-connected inverter in the αβ coordinate system. s This represents the voltage amplitude.

6. The method for improving the adaptability of a flexible loop-closing device to power grid phase jumps according to claim 5, characterized in that, The formula for calculating the internal potential amplitude reference is as follows: Where E is the reference value for the internal potential amplitude, and K q D is the reactive inertia coefficient. q U is the reactive power droop factor. N Q is the reference amplitude of the phase voltage output from the main circuit of the three-phase grid-connected inverter. ref For reference reactive power.

7. The method for improving the adaptability of a flexible loop-closing device to power grid phase transitions according to claim 6, characterized in that, The internal potential generation module obtains a three-phase sinusoidal internal potential modulation wave e abc The calculation expression is: Where θ is the internal potential phase reference.

8. A three-phase grid-connected inverter control system, comprising: Three-phase grid-connected inverter main circuit and virtual synchronous generator control unit; The main circuit of the three-phase grid-connected inverter includes: a DC power supply U dc Three-phase inverter, three-phase LC filter (L f C f DC power supply U dc The DC input of the three-phase inverter is connected to one end of the three-phase LC filter, and the other end of the three-phase LC filter is connected to the equivalent line reactance L. g One end is connected, and the equivalent line reactance L g The other end is connected to the power grid u g Connected; The virtual synchronous generator control unit is characterized by comprising: a power calculation module, an active power-frequency compensation control module, a reactive power-voltage control module, an internal potential generation module, an SVPWM modulation module, and a phase jump calculation module; The three-phase voltage u at sampling point PCC s Output three-phase current i s The input is fed into the power calculation module for power calculation, thereby obtaining the actual active power P transmitted to the power grid. e and reactive power Q e ; active power P e The signal is transmitted to the active-frequency compensation control module to obtain the generated phase θ0 of the virtual synchronous generator; the three-phase voltage u at the PCC is then converted. s The input is sent to the phase jump calculation module. When the voltage amplitude at the PCC drops to a set threshold, the phase jump compensation θ is calculated. c The calculated jump compensation phase θ c The internal potential phase reference θ is obtained by superimposing the generated phase θ0 of the virtual synchronous generator; the voltage amplitude U is obtained by calculating the amplitude of the three-phase voltage at PCC. s Then the voltage amplitude U s With reactive power Q e The data is fed into the reactive power-voltage control module to generate the internal potential amplitude reference E; the internal potential phase reference θ and the internal potential amplitude reference E are then input into the internal potential generation module to obtain the three-phase sinusoidal internal potential modulation wave e. abc ; modulate the three-phase sinusoidal internal potential wave e abc The pulse trigger signals for each switching transistor in the main circuit of the three-phase grid-connected inverter are sent to the SVPWM modulation module.

9. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor in executing the method for improving the adaptability of the flexible loop-closing device to grid phase transitions as described in any one of claims 1 to 7, and the processor is configured to execute the program stored in the memory.

10. A storage medium storing a computer program, characterized in that, When a computer program is run by a processor, it executes the steps of the method for improving the ability of a flexible loop-closing device to adapt to grid phase transitions as described in any one of claims 1 to 7.

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