Static var generator reactive power compensation method and system

Abstract

The embodiment of the application provides a static reactive generator reactive power compensation method, comprising: collecting three-phase voltage signals and three-phase current signals at a grid-connected point of a power grid in real time, calculating a current system actual reactive power based on the three-phase voltage signals and the three-phase current signals; calculating a power difference value of the actual reactive power and a set reactive power value, determining a reactive current target value based on the power difference value; calculating a current difference value of the reactive current target value and an actually output reactive current value, performing inner loop adjustment operation on the current difference value to generate a modulation voltage signal, generating a switching control signal of an electric energy conversion device according to the modulation voltage signal, and controlling the electric energy conversion device to output a corresponding reactive current to the power grid according to the switching control signal; recalculating and updating the reactive current target value according to a voltage drop depth, and limiting an amplitude of the corresponding generated modulation voltage signal.

Description

Technical Field

[0001] This application relates to the field of reactive power compensation technology, and in particular to a method and system for reactive power compensation using a static var generator. Background Technology

[0002] With the widespread application of nonlinear and impulsive loads in power systems, the problem of reactive power fluctuations in power grids is becoming increasingly prominent. Reactive power imbalances can lead to voltage fluctuations, decreased power factor, increased line losses, and deterioration of power quality, seriously affecting the safe and stable operation of power systems and the normal operation of electrical equipment.

[0003] Static var generators (SVAs), as a novel reactive power compensation device, inject or absorb reactive current into the power grid through power electronic converters to achieve dynamic compensation of the grid's reactive power. In existing technologies, SVAs typically employ a dual closed-loop control structure with an outer voltage loop and an inner current loop. The outer voltage loop maintains DC-side voltage stability, while the inner current loop tracks reactive current commands. However, existing control schemes have the following shortcomings in practical applications: First, the generation process of the reactive current target value is relatively simple, failing to fully consider the dynamic characteristics of power differences and the coupling effect of DC-side voltage, resulting in room for improvement in the response speed and steady-state accuracy of reactive power compensation. Second, the inner current loop lacks effective suppression of grid voltage disturbances during regulation, making the modulated voltage signal prone to overshoot and oscillation. Third, when grid faults such as voltage dips occur, existing devices lack a robust low-voltage ride-through control strategy, potentially leading to shutdown and grid disconnection due to overcurrent or overvoltage, failing to meet the grid's reactive power support requirements.

[0004] Therefore, there is an urgent need for a static var generator reactive power compensation method and system that can improve the dynamic response speed and control accuracy of reactive power compensation, while also possessing low-voltage ride-through capability. Summary of the Invention

[0005] In a first aspect, embodiments of this application provide a static var generator reactive power compensation method, including: Three-phase voltage and three-phase current signals are collected in real time at the grid connection point, and the actual reactive power of the current system is calculated based on the three-phase voltage and three-phase current signals. Calculate the power difference between the actual reactive power and the set reactive power value, and determine the target value of reactive current based on the power difference; The current difference between the target reactive current value and the actual output reactive current value is calculated. An inner loop regulation operation is performed on the current difference to generate a modulation voltage signal. A switching control signal for the power conversion device is generated based on the modulation voltage signal, so as to control the power conversion device to output the corresponding reactive current to the grid according to the switching control signal. The voltage value at the grid connection point is monitored in real time. If a voltage drop occurs at the grid connection point based on the voltage value, the reactive current target value is recalculated and updated according to the voltage drop depth. The amplitude of the corresponding generated modulation voltage signal is limited so that the power conversion device outputs reactive current that meets the low-voltage ride-through requirements during the voltage drop period.

[0006] Secondly, embodiments of this application also provide a static var generator reactive power compensation system, comprising: The power calculation module is used to collect three-phase voltage signals and three-phase current signals in real time at the grid connection point, and calculate the actual reactive power of the current system based on the three-phase voltage signals and the three-phase current signals. The target value calculation module is used to calculate the power difference between the actual reactive power and the set reactive power value, and to determine the reactive current target value based on the power difference. The control signal determination module is used to calculate the current difference between the target value of reactive current and the actual output value of reactive current, perform inner loop regulation operation on the current difference to generate a modulation voltage signal, generate a switching control signal for the power conversion device based on the modulation voltage signal, and control the power conversion device to output the corresponding reactive current to the grid according to the switching control signal. The support module is used to monitor the voltage value of the grid connection point in real time. When it is determined that a voltage drop has occurred at the grid connection point based on the voltage value, the reactive current target value is recalculated and updated according to the voltage drop depth, and the amplitude of the corresponding generated modulation voltage signal is limited so that the power conversion device outputs reactive current that meets the low voltage ride-through requirements during the voltage drop period.

[0007] Thirdly, embodiments of this application also provide a static var generator reactive power compensation device, the device comprising: One or more processors; Storage device, configured to store one or more programs, When the one or more programs are executed by the one or more processors, the one or more processors implement the static var generator reactive power compensation method described in the embodiments of this application.

[0008] Fourthly, embodiments of this application also provide a non-volatile storage medium for storing computer-executable instructions, which, when executed by a computer processor, are configured to perform the static var generator reactive power compensation method described in embodiments of this application.

[0009] Fifthly, embodiments of this application also provide a computer program product, which includes a computer program stored in a computer-readable storage medium. At least one processor of the device reads from the computer-readable storage medium and executes the computer program, causing the device to perform the static var generator reactive power compensation method described in embodiments of this application. Attached Figure Description

[0010] Figure 1 A flowchart of a static var generator reactive power compensation method provided in this application embodiment; Figure 2 A flowchart illustrating a method for determining a target value of reactive current based on power difference, provided in an embodiment of this application; Figure 3 A flowchart of a proportional-integral adjustment calculation method provided in this application embodiment; Figure 4 A flowchart illustrating a method for generating a modulated voltage signal using inner-loop regulation operation, as provided in this application embodiment; Figure 5 A flowchart illustrating a method for generating a power conversion device switch control signal, provided in an embodiment of this application; Figure 6 A flowchart illustrating a method for reactive power support control during voltage dips, provided in an embodiment of this application; Figure 7 A structural block diagram of a static var generator reactive power compensation system provided in this application embodiment; Figure 8 This is a schematic diagram of a static var generator reactive power compensation device provided in an embodiment of this application. Detailed Implementation

[0011] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of this application and are not intended to limit the scope of the embodiments. Furthermore, it should be noted that, for ease of description, only the parts relevant to the embodiments of this application are shown in the accompanying drawings, not the entire structure.

[0012] Figure 1 This is a flowchart illustrating a static var generator reactive power compensation method provided in an embodiment of this application. Figure 1 As shown, it includes the following steps: Step S101: Collect three-phase voltage signals and three-phase current signals in real time at the grid connection point, and calculate the actual reactive power of the current system based on the three-phase voltage signals and the three-phase current signals.

[0013] In this context, the grid connection point refers to the point of common coupling where the static var generator (SVR) is connected to the power grid via a connecting reactor. The three-phase voltage signal refers to the instantaneous voltage values ​​of phases A, B, and C at the grid connection point. The three-phase current signal refers to the instantaneous current values ​​of phases A, B, and C injected into the power grid by the SVR. Actual reactive power refers to the reactive power actually consumed or generated by the power grid at the current moment.

[0014] In one embodiment, the three-phase voltage and three-phase current at the grid connection point are first synchronously sampled using voltage and current sensors at a preset sampling frequency, resulting in discrete voltage and current sampling sequences. The three-phase voltage and current signals are then transformed from a three-phase stationary coordinate system to a two-phase stationary coordinate system using a Clarke transform, yielding two-phase stationary voltage and current components. Next, they are transformed from the two-phase stationary coordinate system to a two-phase rotating coordinate system using a Park transform, obtaining d-axis voltage, q-axis voltage, d-axis current, and q-axis current components. According to instantaneous reactive power theory, the actual reactive power is calculated as Q = two-thirds multiplied by the product of the d-axis voltage and q-axis current components minus the product of the q-axis voltage and d-axis current components. The Q value calculated in the current sampling period is taken as the actual reactive power of the current system.

[0015] For example, suppose that at a certain moment the d-axis voltage component is 311 volts, the q-axis voltage component is 0 volts, the d-axis current component is 20 amps, and the q-axis current component is -50 amps, then the actual reactive power Q is equal to two-thirds multiplied by 311 multiplied by -50 minus 0 multiplied by 20, which is approximately equal to -10367 VAR. The negative sign indicates that the device sends capacitive reactive power to the grid.

[0016] Therefore, by calculating the actual reactive power through synchronous sampling and coordinate transformation, the reactive power status of the power grid can be obtained in real time and accurately, providing a reliable basis for the generation of subsequent reactive current target values.

[0017] Step S102: Calculate the power difference between the actual reactive power and the set reactive power value, and determine the target value of reactive current based on the power difference.

[0018] The set reactive power value refers to the target reactive power command value preset by the user according to the reactive power compensation requirements of the power grid. The power difference value refers to the difference between the set reactive power value and the actual reactive power value. The target reactive current value refers to the reactive current command value expected to be output by the static var generator.

[0019] In one embodiment, the set reactive power value Q_ref is subtracted from the actual reactive power Q_actual calculated in step S101 to obtain a power difference value delta_Q, which is equal to Q_ref minus Q_actual. delta_Q is then fed into the reactive power outer loop regulator for adjustment calculations to obtain the initial reactive current target value. The initial reactive current target value is then sequentially filtered and limited, and further corrected based on the stable state of the DC-side voltage to finally obtain the reactive current target value i_q_ref.

[0020] For example, if the set reactive power value Q_ref is 0 VAR and the actual reactive power Q_actual is -10367 VAR, then the power difference delta_Q equals 0 minus -10367, which is 10367 VAR. This indicates that the current reactive power of the power grid is lower than the set value, and the reactive current output needs to be increased to compensate for the reactive power deficit.

[0021] Therefore, by generating a reactive current target value through power difference closed-loop regulation, the actual reactive power can quickly track the set value, thus achieving precise control of reactive power.

[0022] Step S103: Calculate the current difference between the target reactive current value and the actual output reactive current value, perform inner loop regulation operation on the current difference to generate a modulation voltage signal, generate a switch control signal for the power conversion device based on the modulation voltage signal, and control the power conversion device to output the corresponding reactive current to the power grid according to the switch control signal.

[0023] The actual output reactive current value refers to the q-axis actual current component obtained by the current sensor and coordinate transformation. The current difference is the difference between the target reactive current value and the actual output reactive current value. The modulated voltage signal is the voltage command signal output by the inner current loop regulator used to control the power conversion device. The switching control signal is the pulse width modulation signal used to drive the switching of each power switch in the power conversion device.

[0024] In one embodiment, the reactive current target value i_q_ref is subtracted from the actual q-axis current i_q_actual to obtain the current difference delta_i_q, which is equal to i_q_ref minus i_q_actual. delta_i_q is then fed into the inner-loop current regulator for proportional-integral regulation, while simultaneously introducing grid voltage feedforward to generate a modulated voltage signal. This modulated voltage signal is processed by a space vector pulse width modulation algorithm to generate six switch control signals, which respectively drive the switching of the six insulated-gate bipolar transistors in the three-phase bridge power converter, thereby controlling the power converter to output reactive current to the grid that matches the target value.

[0025] For example, if the target reactive current i_q_ref is 60 amps and the actual output q-axis current i_q_actual is 55 amps, then the current difference delta_i_q is equal to 5 amps. The inner current loop regulator increases the q-axis component of the modulation voltage signal based on this difference, so that the output current gradually increases to 60 amps.

[0026] Therefore, by rapidly tracking the target value of reactive current through the inner current loop and generating a switching control signal through space vector pulse width modulation, high-precision and rapid tracking control of reactive current can be achieved.

[0027] Step S104: Monitor the voltage value of the grid connection point in real time. If a voltage drop occurs at the grid connection point based on the voltage value, recalculate and update the reactive current target value according to the voltage drop depth, and limit the amplitude of the corresponding generated modulation voltage signal so that the power conversion device outputs reactive current that meets the low-voltage ride-through requirements during the voltage drop.

[0028] Voltage sag refers to a transient phenomenon where the effective value of the grid connection point voltage is lower than 90% of the rated voltage for a duration exceeding a set threshold. Voltage sag depth refers to the percentage of the difference between the rated voltage and the sag voltage relative to the rated voltage. Low-voltage ride-through refers to the ability of the device to maintain continuous operation without disconnecting from the grid and to provide reactive power support to the grid during a grid voltage sag.

[0029] In one embodiment, the effective value of the three-phase voltage at the grid connection point is calculated in real time. When the effective voltage value is detected to be lower than 90% of the rated voltage for a duration exceeding 10 milliseconds, a voltage sag is determined to have occurred. Based on the voltage sag depth and a preset reactive current support curve, the required reactive current support value is calculated, and this support value replaces the target reactive current value during normal operation. Simultaneously, the amplitude of the modulated voltage signal output from the inner current loop is limited to the maximum linear output voltage range corresponding to the DC bus voltage to prevent over-modulation leading to overcurrent. During voltage recovery, the reactive current support value is gradually reduced according to a set rate of change until the voltage recovers to more than 90% of the rated range, at which point the system switches back to normal reactive power compensation mode.

[0030] For example, assuming a rated voltage of 380 volts, when the grid connection point voltage drops to 266 volts, the drop depth is 30%. According to the reactive power support curve, for every 1% increase in the drop depth, a 2% increase in rated current reactive power support is required. Therefore, the required reactive current support value is 100 amps multiplied by 60%, which is 60 amps. At this point, the target reactive current value is updated to 60 amps, and the modulation voltage amplitude is limited to within approximately 404 volts, corresponding to a DC bus voltage of 700 volts.

[0031] Therefore, by using voltage dip detection and reactive power support control, the device can continue to operate and provide dynamic reactive power support during grid faults, meet the low-voltage ride-through requirements of the grid, and improve the fault recovery capability of the power system.

[0032] In one embodiment, Figure 2 A flowchart illustrating a method for determining a target value of reactive current based on power difference, as provided in this application embodiment, is shown below. Figure 2 As shown, it includes: Step S201: Perform proportional-integral adjustment calculations based on the magnitude and sign of the power difference to obtain the initial reactive current target value, and then filter the initial reactive current target value.

[0033] Proportional-integral (PI) control refers to a method of adjusting the input error signal by passing it through both proportional and integral elements, and then superimposing the output to achieve zero steady-state error control. Filtering refers to applying a low-pass filter to the adjusted output signal to suppress high-frequency noise and fluctuations.

[0034] In one embodiment, the power difference delta_Q is used as the input to the proportional-integral (PI) regulator. The output of the proportional stage is Kp multiplied by delta_Q, and the output of the integral stage is Ki multiplied by the integral of delta_Q over time. The sum of these two values ​​yields the initial reactive current target value i_q_init. i_q_init is then subjected to a first-order low-pass filter with a filtering time constant of 5 milliseconds. The filtered signal, i_q_filtered, is equal to the previous filtered value plus the filter coefficient multiplied by the difference between the current initial value and the previous filtered value. The filter coefficient is equal to the sampling period divided by the sum of the sampling period and the filtering time constant.

[0035] For example, suppose the proportional gain Kp is 0.005 A / V, the integral gain Ki is 0.02 A / V / s, and the power difference delta_Q is 10367 V / s for 0.1 seconds. Then the proportional gain is 0.005 multiplied by 10367, which is approximately 51.8 A, and the integral gain is 0.02 multiplied by 10367 multiplied by 0.1, which is approximately 20.7 A. The initial reactive current target value is approximately 72.5 A. After a first-order low-pass filter, if the sampling period is 0.1 milliseconds and the filter coefficient is 0.02, the filtered value gradually approaches 72.5 A, effectively suppressing signal jumps.

[0036] Therefore, reactive power control with zero steady-state error is achieved through proportional-integral regulation, and high-frequency noise is suppressed by low-pass filtering, which improves the smoothness and stability of the reactive current target value.

[0037] Step S202: Limit the initial reactive current target value after filtering to the maximum allowable output current range of the power conversion device to obtain the limited reactive current target value.

[0038] The maximum output current refers to the maximum effective value of the current that the power switching transistors and connecting reactors in the power conversion device can withstand over a long period of time, which is usually 1.1 to 1.5 times the rated current of the device.

[0039] In one embodiment, the filtered initial reactive current target value i_q_filtered is compared with a preset maximum output current limit I_max. If i_q_filtered is greater than I_max, it is limited to I_max; if i_q_filtered is less than negative I_max, it is limited to negative I_max; otherwise, the original value remains unchanged. After limiting processing, the limited reactive current target value i_q_limited is obtained.

[0040] For example, if the rated current of the device is 100 amps and the maximum output current limit I_max is set to 120 amps, and the target value of the initial reactive current after filtering is 135 amps, then the target value of the limited reactive current after limiting is 120 amps, to prevent the device from damaging the power devices due to excessive output current.

[0041] Therefore, by limiting the target value of reactive current, it can be ensured that the output current of the device does not exceed the allowable range of the device, thus ensuring the safe operation of the device.

[0042] Step S203: Correct the target value of the limited reactive current according to the stable state of the DC side voltage, and use the corrected value as the target value of reactive current.

[0043] Among them, DC side voltage refers to the voltage across the DC bus capacitor of the power conversion device, and the stable state of DC side voltage refers to the magnitude of the deviation between the actual DC voltage and the set DC voltage and its trend of change.

[0044] In one embodiment, the DC bus voltage U_dc is acquired in real time, and the difference between this and the set DC voltage U_dc_ref is used to obtain the DC voltage deviation delta_Udc. delta_Udc is then fed into a DC voltage regulator for proportional-integral (PI) regulation to obtain the active current correction amount i_d_adj. Since the total output current of the device is limited by the maximum current, when it is necessary to increase the active current to maintain DC voltage stability, the reactive current target value is correspondingly reduced. The correction formula is i_q_ref equal to the limited reactive current target value i_q_limited multiplied by the square root of 1 minus the square of the ratio of i_d_adj to I_max, where the absolute value of i_d_adj does not exceed I_max. The corrected i_q_ref is used as the final reactive current target value.

[0045] For example, suppose the target value of the limited reactive current i_q_limited is 120 amps and the maximum current I_max is 120 amps. When the DC voltage drops and active current is needed to support it, the DC voltage regulator output i_d_adj is 36 amps. Then the correction factor is the square root of 1 minus the square of the ratio of 36 to 120, which is the square root of 1 minus 0.09 equals approximately 0.954. The corrected target value of reactive current is 120 multiplied by 0.954, which is approximately 114.5 amps. This maximizes reactive output while ensuring DC voltage stability.

[0046] Therefore, by correcting the target value of reactive current through the DC side voltage stability state, the distribution of active and reactive current can be coordinated, maximizing the reactive compensation capability while maintaining DC voltage stability.

[0047] In one embodiment, Figure 3 A flowchart of a proportional-integral adjustment calculation method provided in this application embodiment is shown below. Figure 3 As shown, it includes: Step S301: When the reactive power difference is positive, determine the reactive current command direction as the first reactive direction; when the reactive power difference is negative, determine the reactive current command direction as the first reactive direction; and simultaneously determine the absolute value of the reactive power difference as the adjustment amplitude.

[0048] The first reactive power direction refers to the positive direction of the q-axis current, corresponding to the direction of inductive reactive current; the second reactive power direction refers to the negative direction of the q-axis current, corresponding to the direction of capacitive reactive current. The adjustment amplitude refers to the absolute value of the reactive power difference used in proportional-integral calculations.

[0049] In one embodiment, the sign of the power difference delta_Q is determined. When delta_Q is greater than zero, it indicates that the actual reactive power is less than the set value, requiring the device to absorb inductive reactive power and determine the reactive current command direction as the positive direction of the q-axis. When delta_Q is less than zero, it indicates that the actual reactive power is greater than the set value, requiring the device to issue capacitive reactive power and determining the reactive current command direction as the negative direction of the q-axis. Simultaneously, the absolute value of delta_Q, abs_delta_Q, is taken as the input to the proportional-integral controller to adjust the amplitude.

[0050] For example, when delta_Q is 10367 V, the command direction is the positive direction of the q-axis, and the adjustment amplitude is 10367 V; when delta_Q is -8000 V, the command direction is the negative direction of the q-axis, and the adjustment amplitude is 8000 V.

[0051] Therefore, by determining the sign of the power difference, the direction of the reactive current is determined, and the absolute value is taken as the adjustment amplitude, so that the proportional-integral regulator always works in the positive input state, avoiding the influence of sign change on the integral element and improving the regulation stability.

[0052] Step S302: Multiply the adjustment amplitude by a preset proportional coefficient to obtain the proportional adjustment amount, and multiply the adjustment amplitude by a preset integral coefficient after time integration to obtain the integral adjustment amount.

[0053] Among them, the preset proportional coefficient refers to the gain of the proportional element, which determines the regulator's response speed to instantaneous errors; the preset integral coefficient refers to the gain of the integral element, which determines the regulator's ability to eliminate steady-state errors.

[0054] In one embodiment, the proportional adjustment P_out equals Kp multiplied by abs_delta_Q, where Kp is a preset proportional coefficient. The integral adjustment I_out equals Ki multiplied by the integral of abs_delta_Q over time. The integration operation uses a discrete accumulation method, and the integral increment for each sampling period is Ki multiplied by abs_delta_Q multiplied by the sampling period Ts. The integral increment is accumulated in the integrator, and the integrator is simultaneously subjected to anti-saturation limiting to the range corresponding to the maximum output current.

[0055] For example, if Kp is 0.005 amps per valence, Ki is 0.02 amps per valence per second, the sampling period Ts is 0.1 milliseconds, and the adjustment amplitude abs_delta_Q is 10367 valences, then the proportional adjustment P_out is 0.005 multiplied by 10367, which is approximately 51.8 amps. The integral increment of the first sampling period is 0.02 multiplied by 10367 multiplied by 0.0001, which is approximately 0.0207 amps. If this error persists for 50 sampling periods, or 5 milliseconds, then the integral adjustment I_out is approximately 1.035 amps.

[0056] Therefore, by rapidly responding to error changes through the proportional element and eliminating steady-state errors through the integral element, the combination of the two achieves rapid and error-free regulation of reactive power.

[0057] Step S303: The proportional adjustment amount and the integral adjustment amount are summed together, and the initial reactive current target value containing direction and amplitude information is generated according to the command direction of the reactive current.

[0058] Among them, superposition and summation refers to adding the proportional regulation and integral regulation to obtain the total regulation output, the direction information refers to the positive or negative sign of the reactive current, and the amplitude information refers to the magnitude of the reactive current.

[0059] In one embodiment, the proportional regulation P_out and the integral regulation I_out are added together to obtain the total regulation PI_out, which is equal to P_out plus I_out. According to the command direction determined in step S301, if it is the positive direction of the q-axis, the initial reactive current target value i_q_init is equal to the positive PI_out; if it is the negative direction of the q-axis, i_q_init is equal to the negative PI_out.

[0060] For example, when P_out is 51.8 amps and I_out is 1.035 amps, the total regulation is 52.835 amps. If the command direction is the positive q-axis direction, then i_q_init is positive 52.835 amps, indicating that the device absorbs 52.835 amps of inductive reactive current; if the command direction is the negative q-axis direction, then i_q_init is negative 52.835 amps, indicating that the device outputs 52.835 amps of capacitive reactive current.

[0061] Therefore, by superimposing proportional and integral adjustment quantities and assigning directional information, a complete reactive current command is generated, thereby achieving precise control over the magnitude and direction of reactive power.

[0062] Figure 4 A flowchart illustrating a method for generating a modulated voltage signal using inner-loop regulation operation, as provided in this application embodiment, is shown below. Figure 4 As shown, it includes: Step S401: Use the current difference as the input of the current inner loop regulator, and perform amplitude limiting processing on the current difference to limit its amplitude from not exceeding the preset maximum tracking error allowable value.

[0063] The maximum tracking error allowable value refers to the maximum current difference allowed by the current inner loop regulator, which is used to prevent the regulator output from saturating due to sudden changes in the target value.

[0064] In one embodiment, the current difference delta_i_q is compared with a preset maximum tracking error allowable value delta_i_max. If the absolute value of delta_i_q is greater than delta_i_max, then delta_i_q is restricted to delta_i_max multiplied by its sign function; otherwise, the original value is retained. delta_i_max is typically set to 20% to 30% of the rated current.

[0065] For example, if the rated current is 100 amps and the maximum tracking error allowable value delta_i_max is set to 25 amps, when the reactive current target value suddenly changes and the current difference reaches 40 amps, the current difference input to the regulator after limiting is 25 amps, thus avoiding integral saturation of the regulator due to excessive input.

[0066] Therefore, by limiting the input current difference, the regulator output can be prevented from saturating when the target current value changes abruptly, thus improving the dynamic stability of the inner current loop.

[0067] Step S402: The current difference after limiting is sent to the current inner loop regulator for proportional-integral regulation calculation to generate an initial modulation voltage signal. During the regulation process, the grid voltage feedforward is introduced and superimposed on the initial modulation voltage signal.

[0068] Among them, the grid voltage feedforward refers to the compensation amount that is directly superimposed on the modulated voltage signal after the collected grid voltage is transformed by coordinate transformation, and is used to offset the influence of grid voltage disturbance on current control.

[0069] In one embodiment, the current difference delta_i_q_lim after limiting is fed into the q-axis current inner loop proportional-integral regulator. The proportional loop output is Kip multiplied by delta_i_q_lim, and the integral loop output is Kii multiplied by the integral of delta_i_q_lim over time. The two are superimposed to obtain the q-axis component u_q_init of the initial modulation voltage. Simultaneously, the q-axis grid voltage component u_q_grid obtained by Parker transformation of the grid voltage is used as a feedforward and superimposed with u_q_init to obtain u_q, which is equal to u_q_init plus u_q_grid. Similarly, for the d-axis, the d-axis current difference, after proportional-integral adjustment, is superimposed with the d-axis grid voltage feedforward u_d_grid to obtain u_d. u_d and u_q together constitute the initial modulation voltage signal.

[0070] For example, suppose the proportional gain Kip of the inner current loop is 2 volts per ampere (Kip), the integral gain Kii is 50 volts per ampere per second (Kii), and the current difference after limiting is 5 amperes for 0.02 seconds. Then the proportional gain output is 10 volts, the integral gain output is 5 volts, and the initial modulation voltage q-axis component is 15 volts. If the current q-axis grid voltage feedforward is 0 volts (the q-axis voltage is zero when the grid voltage is oriented towards the d-axis), then the summed u_q is 15 volts; if the d-axis grid voltage is 311 volts, then u_d contains a 311-volt feedforward.

[0071] Therefore, current tracking without steady-state error is achieved through proportional-integral regulation, and the introduction of grid voltage feedforward can effectively offset the disturbance of grid voltage fluctuations on the output current, significantly improving the anti-interference performance of the inner current loop.

[0072] Step S403: The superimposed modulation voltage signal is subjected to amplitude limiting processing to limit its amplitude within the maximum output voltage range corresponding to the linear modulation zone of the inverter, and an output change rate limit is set to smooth the change slope of the modulation voltage signal to obtain the final modulation voltage signal.

[0073] The linear modulation region refers to the area in space vector pulse width modulation where the modulation ratio does not exceed 1, and the output voltage is linearly related to the modulation signal. The maximum output voltage refers to the maximum phase voltage amplitude that the inverter can output within the linear modulation region, which is equal to the DC bus voltage divided by the square root of 3. The output rate of change limit refers to the maximum allowable change in the modulation voltage per unit time.

[0074] In one embodiment, the magnitude U_m of the superimposed modulation voltage vector is calculated as the square root of u_d squared plus the square root of u_q, and the maximum output voltage U_max in the linear modulation region is equal to U_dc divided by the square root of 3. If U_m is greater than U_max, u_d and u_q are proportionally reduced to make the magnitude equal to U_max. The rate of change is limited as follows: the difference delta_u between the current modulation voltage and the previous cycle modulation voltage is calculated. If the absolute value of delta_u is greater than the rate of change limit du_max multiplied by the sampling period Ts, the current value is limited to the previous cycle value plus du_max multiplied by Ts multiplied by the sign of the difference.

[0075] For example, if the DC bus voltage U_dc is 700 volts, then the maximum output voltage U_max is approximately 404 volts (700 divided by the square root of 3). If the amplitude of the modulated voltage after superposition is 450 volts, then each component is reduced by a scaling factor of 404 divided by 450, which is approximately 0.898. If the rate of change limit du_max is 500 volts per millisecond and the sampling period is 0.1 milliseconds, then the maximum allowable change per period is 50 volts. If u_q was 10 volts in the previous period and the current calculated value is 80 volts, then after the rate of change limit, the current u_q is 60 volts.

[0076] Therefore, by limiting the modulation voltage, the inverter is ensured to operate in the linear modulation region, avoiding the increase of harmonics and control distortion caused by overmodulation; by limiting the rate of change, the modulation voltage change is smoothed, reducing current surges and switching stress.

[0077] In one embodiment, the switching control signal for the power conversion device is generated based on the modulated voltage signal. Specifically: Figure 5 A flowchart illustrating a method for generating a switching control signal for a power conversion device, as provided in this application embodiment, is shown below. Figure 5 As shown, it includes: Step S501: Transform the modulated voltage signal from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the two-phase stationary voltage components, and determine the sector number corresponding to the two-phase stationary voltage components.

[0078] The two-phase rotating coordinate system refers to the dq coordinate system oriented with respect to the grid voltage vector, while the two-phase stationary coordinate system refers to the alpha-beta coordinate system fixed to the stator side. The sector number refers to the numbering of the six 60-degree sector regions on the complex plane where the two-phase stationary voltage vectors lie.

[0079] In one embodiment, based on the current grid voltage phase angle theta, the modulation voltages u_d and u_q in the dq coordinate system are transformed using an inverse Park transformation to obtain the components u_alpha and u_beta in the alpha-beta coordinate system. The transformation formula is: u_alpha equals u_d multiplied by cos theta minus u_q multiplied by sin theta, and u_beta equals u_d multiplied by sin theta plus u_q multiplied by cos theta. The sector is determined based on the sign and magnitude relationship of u_alpha and u_beta: if u_beta is greater than 0, u_alpha is greater than 0, and u_beta is less than the square root of 3 multiplied by u_alpha, then it is the first sector. This process is repeated to divide the complex plane into six equal sectors, numbered 1 to 6.

[0080] For example, let theta be 30 degrees, u_d be 311 volts, and u_q be 50 volts. Then u_alpha equals 311 multiplied by 0.866 minus 50 multiplied by 0.5, approximately 244.3 volts. u_beta equals 311 multiplied by 0.5 plus 50 multiplied by 0.866, approximately 198.8 volts. Since u_alpha is greater than 0, u_beta is greater than 0, and u_beta is greater than the square root of 3 multiplied by u_alpha (approximately 423 volts, which is not true), it is determined to be the second sector.

[0081] Therefore, coordinate transformation and sector determination provide the basis for selecting the basic voltage vector for space vector pulse width modulation.

[0082] Step S502: Select two adjacent basic voltage vectors according to the sector number, and calculate the first and second action times of the two adjacent basic voltage vectors according to the two-phase static voltage components and the DC bus voltage.

[0083] The basic voltage vector refers to the eight spatial voltage vectors corresponding to the eight switching states of a two-level three-phase inverter, including six non-zero vectors and two zero vectors. The first action time and the second action time refer to the duration of action of two adjacent non-zero basic voltage vectors within one switching cycle.

[0084] In one embodiment, two adjacent non-zero basic voltage vectors on either side of the sector are selected according to the sector number. Taking the first sector as an example, the adjacent vectors are U4 (100) and U6 (110). According to the volt-second balance principle, the action time of the two vectors is calculated: X equals √3 multiplied by Ts multiplied by u_beta divided by U_dc, Y equals √3 multiplied by Ts multiplied by (√3 multiplied by u_alpha minus u_beta) divided by 2 divided by U_dc, where Ts is the switching period. The first action time T1 equals X, the second action time T2 equals Y, and the zero vector action time T0 equals Ts minus T1 minus T2. If T1 plus T2 is greater than Ts, then T1 and T2 are reduced proportionally.

[0085] For example, assuming the switching period Ts is 0.1 milliseconds, the DC bus voltage U_dc is 700 volts, u_alpha is 244.3 volts, and u_beta is 198.8 volts, then X equals 1.732 multiplied by 0.0001 multiplied by 198.8 divided by 700, which is approximately 0.0492 milliseconds. Y equals 1.732 multiplied by 0.0001 multiplied by (1.732 multiplied by 244.3 minus 198.8) divided by 2 divided by 700, which is approximately 0.0278 milliseconds. T1 is 0.0492 milliseconds, T2 is 0.0278 milliseconds, and T0 is 0.023 milliseconds.

[0086] Therefore, by calculating the duration of the basic voltage vector through volt-second balance, the required reference voltage vector can be accurately synthesized, achieving low-harmonic pulse width modulation output.

[0087] Step S503: Allocate the first action time and the second action time to the three-phase bridge arm according to the sector number to output the initial switching timing. After dead-time insertion and compensation, the switching control signal of the power conversion device is generated.

[0088] In this context, a three-phase bridge arm refers to a bridge arm structure in an inverter where each of phases A, B, and C is composed of two upper and two lower switching transistors. Dead-time insertion refers to inserting a period of time during which both transistors on the same bridge arm are turned off when switching, to prevent shoot-through short circuits.

[0089] In one embodiment, a seven-segment space vector pulse width modulation method is used, and T1 and T2 are assigned to the corresponding bridge arms according to the sector number. Taking the first sector as an example, the switching sequence is zero vector (000), U4 (100), U6 (110), zero vector (111), U6 (110), U4 (100), zero vector (000), and the duration of each segment is T0 divided by 4, T1 divided by 2, T2 divided by 2, T0 divided by 2, T2 divided by 2, T1 divided by 2, and T0 divided by 4. This timing sequence is converted into a three-phase comparison value and compared with a triangular carrier wave to generate an initial pulse signal. A dead time of 2 to 5 microseconds is inserted before the turn-on signal of each switch, and dead time compensation is performed according to the current direction to finally generate six-channel switch control signals.

[0090] For example, in the first sector, the comparison value for phase A corresponds to T0 divided by 4, the comparison value for phase B corresponds to T0 divided by 4 plus T1 divided by 2, and the comparison value for phase C corresponds to T0 divided by 4 plus T1 divided by 2 plus T2 divided by 2. Let T0 be 0.023 milliseconds, T1 be 0.0492 milliseconds, and T2 be 0.0278 milliseconds. Then the comparison value for phase A is 0.00575 milliseconds, phase B is 0.03035 milliseconds, and phase C is 0.04425 milliseconds. These values ​​are compared with the triangular carrier wave with a peak value of 0.05 milliseconds to obtain the pulses for each phase.

[0091] Therefore, by using seven-segment SVPWM allocation and dead-time insertion compensation, high-quality switching control signals can be generated, output current harmonics can be reduced, and bridge arm shoot-through can be prevented.

[0092] In one embodiment, the reactive current target value is recalculated and updated based on the voltage sag depth, and the amplitude of the corresponding generated modulated voltage signal is limited. Specifically: Figure 6 A flowchart illustrating a method for reactive power support control during voltage dips, as provided in this application embodiment, is shown below. Figure 6 As shown, it includes: Step S601: Calculate the effective voltage value at the grid connection point in real time, compare the effective voltage value with the rated voltage to determine the voltage drop depth, calculate the reactive current support value according to the preset reactive current support curve based on the voltage drop depth, and replace the reactive current target value with the reactive current support value to generate a corresponding updated modulation voltage signal.

[0093] The effective voltage value refers to the root mean square value of the phase voltage or line voltage at the grid connection point. The voltage drop depth is equal to the rated voltage minus the actual voltage, divided by the rated voltage, and multiplied by 100%. The reactive power support curve is a functional relationship curve between the pre-set voltage drop depth and the required reactive current support value.

[0094] In one embodiment, the three-phase voltage sampling values ​​are calculated using a sliding window root mean square (RMS) calculation, with a window length of one power frequency cycle (20 milliseconds) to obtain the effective voltage value U_rms at the grid connection point. The drop depth D is equal to (U_n minus U_rms) divided by U_n multiplied by 100%, where U_n is the rated voltage. When D is greater than 10%, the low-voltage ride-through mode is triggered. The reactive power support curve adopts a piecewise linear approach: when D is between 10% and 50%, the reactive current support value I_support is equal to I_n multiplied by (D minus 10%) multiplied by a coefficient k, where k is 2, meaning that 2% of the rated current is provided for reactive power support for every 1% drop depth; when D is greater than 50%, I_support is 1.2 times the rated current. I_support is used as the new reactive current target value and fed into the inner current loop to generate an updated modulation voltage signal.

[0095] For example, suppose the rated voltage U_n is 380 volts and the rated current I_n is 100 amps. When U_rms is 266 volts, D equals (380 minus 266) divided by 380 multiplied by 100%, which equals 30%. I_support equals 100 multiplied by (30 minus 10) multiplied by 0.02, which equals 40 amps. At this time, the reactive current target value is updated from 20 amps during normal operation to 40 amps, and the inner current loop generates an increased modulation voltage signal accordingly.

[0096] Therefore, by detecting voltage dips and calculating reactive power support curves, it is possible to rapidly increase reactive current output during grid faults, providing dynamic reactive power support for grid voltage recovery.

[0097] Step S602: The amplitude of the updated modulation voltage signal is limited to the maximum output voltage range allowed by the DC bus voltage. During the voltage recovery process, the reactive current support value is gradually reduced according to the set rate of change until the voltage recovers to the rated range.

[0098] The maximum allowable output voltage of the DC bus voltage refers to the maximum phase voltage amplitude that the inverter can output after considering safety margins. The set rate of change refers to the allowable decrease per second in the reactive current support value during voltage recovery.

[0099] In one embodiment, the amplitude of the updated modulation voltage vector is calculated. If it exceeds the DC bus voltage multiplied by 0.9 divided by the square root of 3 (with a 10% margin), it is reduced proportionally. When the grid connection point voltage is detected to be rising, the reactive power support value recovery program is started. I_support is gradually reduced according to the set change rate r (usually 0.5 times the rated current per second), that is, I_support is reduced by r multiplied by Ts in each sampling period. At the same time, the actual voltage is detected. When the voltage recovers to more than 90% of the rated voltage and lasts for 100 milliseconds, I_support is reduced to zero, and the system switches back to the normal reactive power compensation control mode.

[0100] For example, assuming the DC bus voltage is 700 volts, the maximum allowable output voltage is 700 multiplied by 0.9 divided by the square root of 3, which is approximately 363.7 volts. If the updated modulation voltage amplitude is 390 volts, it is reduced by a ratio of 363.7 divided by 390, which is approximately 0.933. During voltage recovery, assuming the rate of change r is 50 amps per second and the sampling period is 0.1 milliseconds, I_support decreases by 0.005 amps per period, and it takes 8 seconds to drop from 40 amps to 0, achieving a smooth transition.

[0101] Therefore, by modulating voltage limiting to prevent overcurrent damage to the device during voltage drop, and by using a gradual recovery strategy to avoid current surges and power oscillations during voltage recovery, a smooth transition during low-voltage ride-through is achieved.

[0102] Figure 7 This application provides a structural block diagram of a static var generator (SVM) reactive power compensation system. This system is configured to execute the SVM reactive power compensation method provided in the above embodiments, and possesses the corresponding functional modules and beneficial effects of the method. Figure 7 As shown, the system includes: The power calculation module 701 is used to acquire three-phase voltage and three-phase current signals in real time at the grid connection point, and calculate the actual reactive power of the current system based on the three-phase voltage and current signals. This module acquires signals through voltage and current sensors, converts them from analog to digital, and sends them to a digital signal processor. The dq-axis components are obtained through Clarke and Parker transforms, and the actual reactive power is then calculated based on instantaneous reactive power theory.

[0103] The target value calculation module 702 is used to calculate the power difference between the actual reactive power and the set reactive power value, and determine the target reactive current value based on the power difference. This module includes a reactive power outer loop proportional-integral regulator, a low-pass filter, a limiter, and a DC voltage correction unit, which sequentially complete proportional-integral regulation, filtering, limiting, and DC-side voltage coordination correction to output the final target reactive current value.

[0104] The control signal determination module 703 is used to calculate the current difference between the target reactive current value and the actual output reactive current value, perform inner-loop regulation calculation on the current difference to generate a modulation voltage signal, and generate a switching control signal for the power conversion device based on the modulation voltage signal, so as to control the power conversion device to output the corresponding reactive current to the grid according to the switching control signal. This module includes a current inner-loop proportional-integral regulator, a grid voltage feedforward unit, a modulation voltage limiting and rate of change limiting unit, and a space vector pulse width modulation unit, and outputs six switching drive signals.

[0105] The support module 704 is used to monitor the voltage value at the grid connection point in real time. If a voltage dip is detected at the grid connection point based on the voltage value, the module recalculates and updates the reactive current target value according to the voltage dip depth, and limits the amplitude of the corresponding generated modulation voltage signal, ensuring that the power conversion device outputs reactive current that meets the low-voltage ride-through requirements during the voltage dip. This module includes a voltage RMS calculation unit, a dip detection unit, a reactive power support curve calculation unit, and a modulation voltage limiting unit, and takes over the generation of the reactive current target value during the voltage dip.

[0106] Optionally, the target value calculation module 702 is specifically used for: performing proportional-integral adjustment calculations based on the magnitude and sign of the power difference to obtain an initial reactive current target value, and filtering the initial reactive current target value; limiting the filtered initial reactive current target value to the maximum allowable output current range of the power conversion device to obtain a limited reactive current target value; and correcting the limited reactive current target value based on the stable state of the DC side voltage, using the corrected value as the reactive current target value.

[0107] Thus, through the coordinated operation of the above four functional modules, precise closed-loop control of reactive power and low-voltage ride-through function are achieved, improving the compensation performance and grid adaptability of the static var generator.

[0108] Figure 8 A schematic diagram of a static var generator reactive power compensation device provided in this application embodiment is shown below. Figure 8 As shown, the device includes a processor 801, a memory 802, an input device 803, and an output device 804; the number of processors in the device can be one or more. Figure 8 Taking a processor 801 as an example; the processor 801, memory 802, input device 803, and output device 804 in the device can be connected via a bus or other means. Figure 8 Taking the example of a connection between China and Israel via a bus.

[0109] The memory 802, as a computer-readable storage medium, can be used to store software programs, computer-executable programs, and modules, such as the program instructions or modules corresponding to the static var generator reactive power compensation method in this embodiment. The processor 801 executes various functional applications and data processing of the device by running the software programs, instructions, and modules stored in the memory 802, thereby implementing the aforementioned static var generator reactive power compensation method.

[0110] The memory 802 may primarily include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a given function; the data storage area may store data created based on terminal usage. Furthermore, the memory 802 may include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some instances, the memory 802 may further include memory remotely located relative to the processor 801, which can be connected to the device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0111] Input device 803 can be used to receive input digital or character information, and to generate key signal inputs related to user settings and function control of the device, such as receiving set reactive power values, DC voltage setpoints, low-voltage ride-through parameters, etc. Output device 804 may include display devices such as a display screen for displaying information such as device operating status, voltage and current waveforms, and reactive power values, and may also include a switch drive signal output interface for sending switch control signals to the power conversion device.

[0112] This application embodiment also provides a storage medium for storing computer-executable instructions. When executed by a computer processor, the computer-executable instructions are used to execute the static var generator reactive power compensation method provided in the above embodiment. The method includes: real-time acquisition of three-phase voltage signals and three-phase current signals at the grid connection point; calculation of the actual reactive power of the current system based on the three-phase voltage signals and the three-phase current signals; calculation of the power difference between the actual reactive power and a set reactive power value; determination of a reactive current target value based on the power difference; calculation of the current difference between the reactive current target value and the actual output reactive current value; generation of a modulation voltage signal by performing an inner-loop adjustment operation on the current difference; generation of a switching control signal for a power conversion device based on the modulation voltage signal; real-time monitoring of the voltage value at the grid connection point; recalculation and updating of the reactive current target value based on the voltage drop depth when a voltage drop occurs; and limitation of the amplitude of the modulation voltage signal.

[0113] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the static var generator reactive power compensation method provided in the above embodiments.

[0114] Based on the above description of the implementation methods, those skilled in the art can clearly understand that this application can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory, random access memory, flash memory, programmable read-only memory, electrically erasable programmable read-only memory, register, hard disk, removable disk, read-only optical disk, or any other form of storage medium, including several instructions to cause a computer device to execute the methods described in the various embodiments of this application.

Claims

1. A method for reactive power compensation using a static var generator, characterized in that, include: Three-phase voltage and three-phase current signals are collected in real time at the grid connection point, and the actual reactive power of the current system is calculated based on the three-phase voltage and three-phase current signals. Calculate the power difference between the actual reactive power and the set reactive power value, and determine the target value of reactive current based on the power difference; The current difference between the target reactive current value and the actual output reactive current value is calculated. An inner loop regulation operation is performed on the current difference to generate a modulation voltage signal. A switching control signal for the power conversion device is generated based on the modulation voltage signal, so as to control the power conversion device to output the corresponding reactive current to the grid according to the switching control signal. The voltage value at the grid connection point is monitored in real time. If a voltage drop occurs at the grid connection point based on the voltage value, the reactive current target value is recalculated and updated according to the voltage drop depth. The amplitude of the corresponding generated modulation voltage signal is limited so that the power conversion device outputs reactive current that meets the low-voltage ride-through requirements during the voltage drop period.

2. The static var generator reactive power compensation method according to claim 1, characterized in that, Determining the target reactive current value based on the power difference includes: Based on the magnitude and sign of the power difference, a proportional-integral adjustment calculation is performed to obtain the initial reactive current target value, and the initial reactive current target value is then filtered. The initial reactive current target value after filtering is limited to the maximum allowable output current range of the power conversion device to obtain the limited reactive current target value. The target value of the limited reactive current is corrected according to the steady state of the DC side voltage, and the corrected value is used as the target value of reactive current.

3. The static var generator reactive power compensation method according to claim 2, characterized in that, The step of performing proportional-integral adjustment calculations based on the magnitude and sign of the power difference to obtain the initial reactive current target value includes: When the reactive power difference is positive, the reactive current command direction is determined as the first reactive direction; when the reactive power difference is negative, the reactive current command direction is determined as the first reactive direction; and the absolute value of the reactive power difference is determined as the adjustment amplitude. The proportional adjustment amount is obtained by multiplying the adjustment amplitude by a preset proportional coefficient, and the integral adjustment amount is obtained by integrating the adjustment amplitude over time and then multiplying it by a preset integral coefficient. The proportional adjustment and the integral adjustment are summed together, and the initial reactive current target value containing direction and amplitude information is generated according to the command direction of the reactive current.

4. The static var generator reactive power compensation method according to claim 1, characterized in that, The step of performing inner-loop adjustment on the current difference to generate a modulated voltage signal includes: The current difference is used as the input of the inner current loop regulator, and the current difference is limited to limit its amplitude to not exceed the preset maximum tracking error allowable value. The current difference after limiting is sent to the current inner loop regulator for proportional-integral regulation to generate an initial modulation voltage signal. During the regulation process, the grid voltage feedforward is introduced and superimposed on the initial modulation voltage signal. The superimposed modulated voltage signal is subjected to amplitude limiting processing to limit its amplitude within the maximum output voltage range corresponding to the linear modulation zone of the inverter, and an output change rate limit is set to smooth the change slope of the modulated voltage signal to obtain the final modulated voltage signal.

5. The static var generator reactive power compensation method according to claim 1, characterized in that, The step of generating the switching control signal for the power conversion device based on the modulated voltage signal includes: The modulation voltage signal is transformed from a two-phase rotating coordinate system to a two-phase stationary coordinate system to obtain two-phase stationary voltage components, and the sector number corresponding to the two-phase stationary voltage components is determined. Select two adjacent basic voltage vectors according to the sector number, and calculate the first and second action times of the two adjacent basic voltage vectors according to the two-phase static voltage components and the DC bus voltage. The first and second action times are allocated to the three-phase bridge arms according to the sector number to output the initial switching timing. After dead-time insertion and compensation, the switching control signal of the power conversion device is generated.

6. The reactive power compensation method for a static var generator according to any one of claims 1-5, characterized in that, The step of recalculating and updating the reactive current target value based on the voltage drop depth, and limiting the amplitude of the corresponding generated modulation voltage signal, includes: The effective voltage value at the grid connection point is calculated in real time. The effective voltage value is compared with the rated voltage to determine the voltage drop depth. The reactive current support value is calculated according to the preset reactive current support curve based on the voltage drop depth. The reactive current support value replaces the reactive current target value to generate a corresponding updated modulation voltage signal. The amplitude of the updated modulation voltage signal is limited to the maximum output voltage range allowed by the DC bus voltage. During the voltage recovery process, the reactive current support value is gradually reduced according to the set rate of change until the voltage recovers to the rated range.

7. A static var generator reactive power compensation system, characterized in that, include: The power calculation module is used to collect three-phase voltage signals and three-phase current signals in real time at the grid connection point, and calculate the actual reactive power of the current system based on the three-phase voltage signals and the three-phase current signals. The target value calculation module is used to calculate the power difference between the actual reactive power and the set reactive power value, and to determine the reactive current target value based on the power difference. The control signal determination module is used to calculate the current difference between the target value of reactive current and the actual output value of reactive current, perform inner loop regulation operation on the current difference to generate a modulation voltage signal, generate a switching control signal for the power conversion device based on the modulation voltage signal, and control the power conversion device to output the corresponding reactive current to the grid according to the switching control signal. The support module is used to monitor the voltage value of the grid connection point in real time. When it is determined that a voltage drop has occurred at the grid connection point based on the voltage value, the reactive current target value is recalculated and updated according to the voltage drop depth, and the amplitude of the corresponding generated modulation voltage signal is limited so that the power conversion device outputs reactive current that meets the low voltage ride-through requirements during the voltage drop period.

8. The static var generator reactive power compensation system according to claim 7, characterized in that, The target value calculation module is specifically used for: Based on the magnitude and sign of the power difference, a proportional-integral adjustment calculation is performed to obtain the initial reactive current target value, and the initial reactive current target value is then filtered. The initial reactive current target value after filtering is limited to the maximum allowable output current range of the power conversion device to obtain the limited reactive current target value. The target value of the limited reactive current is corrected according to the steady state of the DC side voltage, and the corrected value is used as the target value of reactive current.

9. A static var generator reactive power compensation device, the device comprising: One or more processors; A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the static var generator reactive power compensation method as described in any one of claims 1-6.

10. A storage medium storing computer-executable instructions, which, when executed by a computer processor, are used to perform the static var generator reactive power compensation method as described in any one of claims 1-6.

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