Virtual impedance-based sending end MMC fault ride-through method, system and device, and medium

Abstract

The invention relates to a sending end MMC fault ride-through method, system and device based on virtual impedance and a medium. The method comprises the following steps: generating modulation voltage correction of a three-phase bridge arm in a sending-end MMC by using virtual impedance based on an alternating current component of a bridge arm current in the sending-end MMC; determining the state of the AC side of the sending end MMC based on the AC voltage amplitude of the sending end MMC; when the state of the alternating current side of the sending end MMC is a fault state, the modulation voltage of the three-phase bridge arm is corrected based on the modulation voltage correction amount of the three-phase bridge arm in the sending end MMC, so that the corrected modulation voltage is obtained; and based on the corrected modulation voltage, controlling the sending end MMC to pass through the fault of the alternating current side. According to the invention, when the state of the AC side of the sending end MMC is the fault state, the low-voltage ride-through signal is generated, and the fault ride-through of the AC side of the sending end MMC can be effectively realized by detecting the low-voltage ride-through signal and inputting the virtual resistor, so that the fault low-voltage ride-through capability of the network side of the sending end is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current transmission, and in particular to a sending-end MMC fault ride-through method, system, equipment and medium based on virtual impedance. Background Art

[0002] Building a new power system based on wind and solar power generation has become a trend in future power grid development. Flexible DC transmission technology based on modular multilevel converters (MMCs) offers advantages such as flexible control, diverse operating modes, and high power supply reliability. It is an effective means of integrating renewable energy for long-distance transmission. For wind power, photovoltaic power and other systems transmitted through flexible direct current interconnection, the faults can be divided into receiving-end AC system faults and sending-end AC system faults according to the fault location; when the receiving-end grid fault causes the output power to be blocked, the collection station continues to inject power through the flexible direct current, and the surplus power will not be able to be transmitted, which will cause DC overvoltage. The receiving-end AC fault ride-through can be achieved by quickly reducing the wind farm power or configuring energy-consuming devices; when the sending-end AC system fails, in order to control the AC voltage at the grid connection point, the output current of the sending-end converter station increases rapidly, but due to capacity limitations, the current will reach the limit under severe faults, and the sending-end converter station loses control of the grid connection point voltage. In order to ensure that the wind farm can continue to operate without disconnecting from the grid when an asymmetric fault occurs at the grid connection point between the interconnected system and the AC system, it is urgent to study the corresponding sending-end MMC low-ride-through strategy. Summary of the Invention

[0003] In order to solve the technical defects of the prior art in the low voltage ride-through fault of the sending-end MMC, the first aspect of the present invention provides a sending-end MMC fault ride-through method based on virtual impedance, the method comprising:

[0004] Based on the AC component of the bridge arm current in the sending-end MMC, a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC is generated using a virtual impedance;

[0005] Determining the state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC;

[0006] When the state of the AC side of the sending-end MMC is a fault state, the modulation voltage of the three-phase bridge arm is corrected based on the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC to obtain a corrected modulation voltage;

[0007] Based on the corrected modulation voltage, the sending-end MMC is controlled to ride through the fault on the AC side.

[0008] Optionally, the generating of the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC by using virtual impedance based on the AC component of the bridge arm current in the sending-end MMC includes:

[0009] Perform Park transformation on the AC component of the bridge arm current in the sending-end MMC to obtain the direct-axis current component and the quadrature-axis current component;

[0010] Based on the direct-axis current component, the quadrature-axis current component and the virtual impedance coefficient, respectively calculating a direct-axis voltage component and a quadrature-axis voltage component;

[0011] Performing an inverse Pike transformation on the direct-axis voltage component and the quadrature-axis voltage component to obtain a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC.

[0012] Optionally, the virtual impedance coefficient includes a virtual resistance coefficient and a virtual reactance coefficient;

[0013] The calculating of the direct-axis voltage component and the quadrature-axis voltage component based on the direct-axis current component, the quadrature-axis current component, and the virtual impedance coefficient respectively includes:

[0014] Filter the product of the direct axis current component and the virtual resistance coefficient to obtain the voltage corresponding to the virtual resistance;

[0015] Filter the product of the quadrature-axis current component and the virtual reactance coefficient to obtain the voltage corresponding to the virtual reactance;

[0016] The difference between the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the direct-axis voltage component, and the sum of the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the quadrature-axis voltage component.

[0017] Optionally, determining the state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC includes:

[0018] When the AC voltage amplitude is less than a preset voltage threshold, it is determined that the state of the AC side of the sending-end MMC is a fault state.

[0019] Optionally, controlling the sending-end MMC to ride through an AC-side fault based on the corrected modulation voltage includes:

[0020] Based on the corrected modulation voltage, a modulation wave algorithm is used to generate a modulation wave of the three-phase bridge arm in the sending-end MMC;

[0021] Based on the modulation wave of the three-phase bridge arm in the sending-end MMC, each phase bridge arm in the sending-end MMC is controlled respectively, so that the sending-end MMC can cross the fault on the AC side.

[0022] Optionally, the method for determining the modulation voltage of the three-phase bridge arm includes:

[0023] Based on the actual value and reference value of the bridge arm current in the sending-end MMC, a standby direct-axis voltage reference value, an actual direct-axis voltage value, a standby quadrature-axis voltage reference value, and an actual quadrature-axis voltage value are obtained;

[0024] Calculating a direct-axis voltage reference value based on the standby direct-axis voltage reference value, the direct-axis voltage actual value, and a feedforward amount of the direct-axis voltage actual value;

[0025] Calculating a quadrature-axis voltage reference value based on the standby quadrature-axis voltage reference value, the quadrature-axis voltage actual value, and a feedforward amount of the quadrature-axis voltage actual value;

[0026] Performing an inverse Peek transformation on the direct-axis voltage reference value and the quadrature-axis voltage reference value to obtain a modulation voltage of the three-phase bridge arm.

[0027] Optionally, obtaining a standby direct-axis voltage reference value, a direct-axis voltage actual value, a standby quadrature-axis voltage reference value, and a quadrature-axis voltage actual value based on the actual value and reference value of the bridge arm current in the sending-end MMC includes:

[0028] Based on the direct-axis actual value and the direct-axis reference value of the bridge arm current in the sending-end MMC, the direct-axis voltage actual value is output using a proportional-integral algorithm;

[0029] Based on the quadrature-axis actual value and the quadrature-axis reference value of the bridge arm current in the sending-end MMC, the quadrature-axis voltage actual value is output using a proportional-integral algorithm;

[0030] The direct-axis actual value and the quadrature-axis actual value are subjected to current inner loop decoupling to obtain a standby direct-axis voltage reference value and a standby quadrature-axis voltage reference value, respectively.

[0031] Based on the same inventive concept, a second aspect of the present invention provides a sending-end MMC fault ride-through system based on virtual impedance, the system comprising:

[0032] A correction value generating unit, configured to generate a modulation voltage correction value of the three-phase bridge arm in the sending-end MMC using a virtual impedance based on an AC component of the bridge arm current in the sending-end MMC;

[0033] A state determining unit, configured to determine a state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC;

[0034] A voltage adjustment correction unit is configured to correct the modulation voltage of the three-phase bridge arm based on the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC when the state of the AC side of the sending-end MMC is a fault state, so as to obtain a corrected modulation voltage;

[0035] A fault ride-through unit is used to control the sending-end MMC to ride through a fault on the AC side based on the corrected modulation voltage.

[0036] Optionally, the correction value generating unit includes:

[0037] A current component determination module is used to perform Park transformation on the AC component of the bridge arm current in the sending-end MMC to obtain the direct-axis current component and the quadrature-axis current component;

[0038] a voltage component determination module, configured to calculate a direct-axis voltage component and a quadrature-axis voltage component based on the direct-axis current component, the quadrature-axis current component, and a virtual impedance coefficient;

[0039] The correction amount determination module is used to perform an inverse Peek transformation on the direct-axis voltage component and the quadrature-axis voltage component to obtain the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC.

[0040] Optionally, the virtual impedance coefficient includes a virtual resistance coefficient and a virtual reactance coefficient;

[0041] The voltage component determination module is specifically configured to:

[0042] Filter the product of the direct axis current component and the virtual resistance coefficient to obtain the voltage corresponding to the virtual resistance;

[0043] Filter the product of the quadrature-axis current component and the virtual reactance coefficient to obtain the voltage corresponding to the virtual reactance;

[0044] The difference between the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the direct-axis voltage component, and the sum of the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the quadrature-axis voltage component.

[0045] Optionally, the state determination unit is specifically configured to:

[0046] When the AC voltage amplitude is less than a preset voltage threshold, it is determined that the state of the AC side of the sending-end MMC is a fault state.

[0047] Optionally, the fault ride-through unit is specifically configured to:

[0048] Based on the corrected modulation voltage, a modulation wave algorithm is used to generate a modulation wave of the three-phase bridge arm in the sending-end MMC;

[0049] Based on the modulation wave of the three-phase bridge arm in the sending-end MMC, each phase bridge arm in the sending-end MMC is controlled respectively, so that the sending-end MMC can cross the fault on the AC side.

[0050] Optionally, the system further includes: a modulation voltage determination unit; the modulation voltage determination unit includes:

[0051] A voltage parameter determination module is used to obtain a standby direct-axis voltage reference value, a direct-axis voltage actual value, a standby quadrature-axis voltage reference value, and a quadrature-axis voltage actual value based on the actual value and reference value of the bridge arm current in the sending-end MMC;

[0052] a direct-axis voltage reference value determining module, configured to calculate a direct-axis voltage reference value based on the standby direct-axis voltage reference value, the direct-axis voltage actual value, and a feedforward amount of the direct-axis voltage actual value;

[0053] a quadrature-axis voltage reference value determination module, configured to calculate a quadrature-axis voltage reference value based on the standby quadrature-axis voltage reference value, the quadrature-axis voltage actual value, and a feedforward amount of the quadrature-axis voltage actual value;

[0054] The modulation voltage determination module is used to perform an inverse Pike transformation on the direct-axis voltage reference value and the quadrature-axis voltage reference value to obtain the modulation voltage of the three-phase bridge arm.

[0055] Optionally, the voltage parameter determination module is specifically configured to:

[0056] Based on the direct-axis actual value and the direct-axis reference value of the bridge arm current in the sending-end MMC, the direct-axis voltage actual value is output using a proportional-integral algorithm;

[0057] Based on the quadrature-axis actual value and the quadrature-axis reference value of the bridge arm current in the sending-end MMC, the quadrature-axis voltage actual value is output using a proportional-integral algorithm;

[0058] The direct-axis actual value and the quadrature-axis actual value are subjected to current inner loop decoupling to obtain a standby direct-axis voltage reference value and a standby quadrature-axis voltage reference value, respectively.

[0059] Based on the same inventive concept, a third aspect of the present invention further provides a computing device, including: one or more processors;

[0060] a processor for executing one or more programs;

[0061] When the one or more programs are executed by the one or more processors, the sending-end MMC fault ride-through method based on virtual impedance as described in any one of the first aspects above is implemented.

[0062] Based on the same inventive concept, the fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the sending-end MMC fault ride-through method based on virtual impedance as described in any one of the above-mentioned first aspects is implemented.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] The present invention provides a sending-end MMC fault ride-through method based on virtual impedance. When the state of the AC side of the sending-end MMC is a fault state, the method inputs a virtual resistor by means of a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC to correct the modulation voltage of the three-phase bridge arm. This can effectively realize the system grid-side fault ride-through, improve the sending-end grid-side fault low voltage ride-through capability, and effectively suppress the bridge arm current when the sending-end low voltage ride-through residual margin is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is a flow chart of a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention;

[0066] Figure 2 This is a topology diagram of a double-terminal flexible DC system using a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention;

[0067] Figure 3 This is a schematic diagram of the fault location of a double-terminal flexible DC system using a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention;

[0068] Figure 4 This is a schematic diagram of a three-phase short-circuit grounding fault path on the AC side of an MMC based on virtual impedance provided by the present invention;

[0069] Figure 5 This is a schematic diagram of an equivalent circuit of a three-phase short-circuit grounding fault on the AC side of an MMC based on virtual impedance provided by the present invention;

[0070] Figure 6 This is a flow chart of another sending-end MMC fault ride-through method based on virtual impedance provided by the present invention;

[0071] Figure 7 A schematic diagram of a method provided by the present invention for generating a modulation voltage correction value of a three-phase bridge arm in a sending-end MMC by using a virtual impedance;

[0072] Figure 8 This is a schematic diagram of a virtual impedance equivalent circuit provided by the present invention;

[0073] Figure 9 A schematic diagram of a virtual impedance control principle provided by the present invention;

[0074] Figure 10 This is a flow chart of a method for determining the modulation voltage of a three-phase bridge arm provided by the present invention;

[0075] Figure 11 A schematic diagram of a virtual impedance inner loop current control method for a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention;

[0076] Figure 12 A block diagram of a sending-end MMC fault ride-through system based on virtual impedance provided by the present invention;

[0077] Figure 13 A block diagram of a correction value generating unit provided by the present invention;

[0078] Figure 14 A block diagram of a computer device provided by the present invention. DETAILED DESCRIPTION

[0079] At present, fault analysis and fault ride-through are mostly focused on cooperating with energy-consuming devices at the receiving end to achieve receiving-end fault ride-through, and there is limited research on fault mechanism analysis and fault MMC ride-through strategy at the sending end. Especially when the low-voltage ride-through residual margin at the sending end is small, it is difficult to effectively suppress the bridge arm current by relying solely on traditional low-voltage current limiting control.

[0080] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for fault ride-through of a sending-end MMC based on virtual impedance, comprising: generating a modulation voltage correction value for the three-phase bridge arm in the sending-end MMC based on the AC component of the bridge arm current in the sending-end MMC using virtual impedance; determining the state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC; when the state of the AC side of the sending-end MMC is a fault state, correcting the modulation voltage of the three-phase bridge arm based on the modulation voltage correction value of the three-phase bridge arm in the sending-end MMC to obtain a corrected modulation voltage; and controlling the sending-end MMC to ride through the fault on the AC side based on the corrected modulation voltage. This method generates a low-voltage ride-through signal when the AC side of the sending-end MMC is a fault state. By detecting the low-voltage ride-through signal and applying a virtual resistor, the method can effectively achieve fault ride-through on the system grid side (the AC side of the sending-end MMC), thereby improving the low-voltage ride-through capability of the sending-end grid side fault.

[0081] Example 1:

[0082] Figure 1 This is a flow chart of a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention, such as Figure 1 As shown, the method may include the following steps:

[0083] In step 110, based on the AC component of the bridge arm current in the sending-end MMC, a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC is generated using virtual impedance.

[0084] In this step, the AC component of the bridge arm current can be obtained by collecting the bridge arm current using a current sensor (eg, a Hall sensor, a shunt, etc.) provided on the three-phase bridge arm in the sending-end MMC (Modular Multilevel Converter).

[0085] A specific implementation method for obtaining the AC component of the bridge arm current is as follows: the acquired bridge arm current may be subjected to signal processing, and the DC pole current / 3 may be subtracted to extract the AC component of the bridge arm current.

[0086] It should be noted that Figure 2 This is a topology diagram of a double-terminal flexible DC system based on a sending-end MMC fault ride-through method provided by the present invention. Figure 2 As shown, the double-terminal flexible DC system may include a sending station, a receiving station and a DC transmission line. The sending station may be connected to an AC system (for example, an AC power grid system, etc.) or a new energy station (for example, a wind power station, a photovoltaic power station, etc.) through a receiving transformer. The receiving station may be connected to a passive power grid or an AC system through a receiving transformer. The sending station may include a sending MMC. The AC side of the sending MMC is connected to the sending transformer. The DC side of the sending MMC is connected to the DC side of the converter in the receiving station through a positive DC transmission line, a negative DC transmission line and a metal return line. The AC side of the converter in the receiving station is connected to the receiving transformer.

[0087] In step 120, the state of the AC side of the sending-end MMC is determined based on the AC voltage amplitude of the sending-end MMC.

[0088] The AC voltage amplitude may be the voltage amplitude on the AC side of the sending-end MMC.

[0089] A possible implementation of this step is to determine that the state of the AC side of the sending-end MMC is a fault state when the AC voltage amplitude is less than a preset voltage threshold.

[0090] Another possible implementation of this step is to determine that the state of the AC side of the sending-end MMC is normal when the AC voltage amplitude is greater than or equal to a preset voltage threshold.

[0091] For example, Figure 3 This is a schematic diagram of the fault location of a double-terminal flexible DC system using a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention. Figure 3 As shown, when the PCC (Point of Common Coupling) of the double-terminal flexible DC system fails (for example, a three-phase short circuit grounding fault occurs on the MMC AC side), the AC voltage amplitude of the sending-end MMC is less than the preset voltage threshold, and it can be determined that the state of the sending-end MMC AC side is a fault state.

[0092] In step 130, when the state of the AC side of the sending-end MMC is a fault state, the modulation voltage of the three-phase bridge arm is corrected based on the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC to obtain a corrected modulation voltage.

[0093] It should be noted that when the AC voltage amplitude is less than the preset voltage threshold, the state of the AC side of the sending-end MMC is determined to be a fault state, and a low-through signal can be generated (that is, by judging the grid-side AC voltage amplitude, when the grid-side voltage amplitude drops to the low-through set value, the low-through signal changes from 0 to 1). When the low-through signal is detected, the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC is used to correct the modulation voltage of the three-phase bridge arm (for example, after detecting that the system low-through flag signal changes from 0 to 1, the corresponding virtual impedance is input to superimpose the original modulation wave with the corresponding virtual impedance correction component, and the corresponding virtual impedance is cut off after the fault crossing is completed).

[0094] For example, Figure 4 This is a schematic diagram of a three-phase short-circuit grounding fault path on the MMC AC side based on virtual impedance provided by the present invention, as shown in FIG. Figure 4 As shown in the figure, taking the case of a three-phase ground short circuit fault in the AC system at the sending end of the offshore wind power transmission system via flexible direct current as an example, the fault loop is formed between the short circuit point and the grounding point on the converter transformer valve side of the receiving end AC system through the upper and lower bridge arms of the sending and receiving end converter stations. Figure 5 As shown, Figure 5 This is a schematic diagram of an equivalent circuit of a three-phase short-circuit grounding fault on the MMC AC side based on virtual impedance provided by the present invention. The voltage at the offshore PCC point is established by the MMC. The wind farm adopts a maximum power tracking strategy. The wind farm can be equivalent to a controlled current source, and the sending-end MMC station can be equivalent to a voltage source. After a three-phase short-circuit fault, the grid-side voltage drops rapidly, the wind farm continuously injects energy into the short-circuit point, and the MMC capacitor discharges and injects energy into the short-circuit point. The fault circuit includes the equivalent resistance and leakage reactance of the converter transformer, the equivalent resistance and bridge reactance of the MMC, and the virtual impedance. In order to suppress the rise of the bridge arm fault current, the system inputs the corresponding virtual impedance after detecting the low-through signal (the virtual impedance includes the virtual resistor R v and virtual inductance L v ), which can effectively ride through AC side faults.

[0095] In step 140, based on the corrected modulation voltage, the sending-end MMC is controlled to ride through the fault on the AC side.

[0096] A possible implementation method of this step is to generate a modulation wave of the three-phase bridge arm in the sending-end MMC based on the corrected modulation voltage using a modulation wave algorithm; based on the modulation wave of the three-phase bridge arm in the sending-end MMC, control each phase bridge arm in the sending-end MMC separately to enable the sending-end MMC to cross the fault on the AC side.

[0097] The modulation wave algorithm may be a PWM (Pulse Width Modulation) modulation wave algorithm, an NLM (Non-Local Means) modulation wave algorithm, or a phase generation carrier modulation algorithm.

[0098] It should be noted that the corrected modulation voltage is input into the modulation wave algorithm, and the modulation wave algorithm outputs the modulation wave of the three-phase bridge arm in the sending-end MMC based on the input modulation voltage. The modulation wave of the three-phase bridge arm in the sending-end MMC is used to control the input or removal of the sub-module in each phase bridge arm, thereby achieving the purpose of controlling the voltage or current of each phase bridge arm in the sending-end MMC, so that the sending-end MMC can cross the fault on the AC side.

[0099] Optionally, after step 140 (i.e., the sending-end MMC crosses the fault on the AC side), the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC is multiplied by the slope threshold (or the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC is adjusted by a ramp function) to obtain a standby modulation voltage correction amount, and based on the standby modulation voltage correction amount, the modulation voltage of the three-phase bridge arm is corrected to obtain a corrected modulation voltage.

[0100] For example, a possible implementation of the above-mentioned method for fault ride-through of a sending-end MMC based on virtual impedance may include generating a system low-through signal, inputting a virtual impedance, and a ramp link. The system low-through signal is generated by judging the AC voltage amplitude on the grid side (i.e., the AC side of the sending-end MMC). When the grid-side voltage amplitude drops to the low-through set value, the low-through signal changes from 0 to 1 (i.e., a system low-through signal is generated). After detecting that the system low-through flag signal changes from 0 to 1, the corresponding virtual impedance is input, i.e., the original modulation wave is superimposed with the corresponding virtual impedance correction component (i.e., the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC). After the fault ride-through is completed, the corresponding virtual impedance is removed. When the corresponding virtual impedance is removed, a ramp link (i.e., the virtual impedance correction component is multiplied by the slope threshold to slowly exit the virtual impedance) is used to reduce the step effect on the system modulation wave after the virtual impedance is input or removed.

[0101] The present invention can, after detecting the system low-crossing flag signal, input the corresponding virtual impedance, that is, the original modulated wave superimposed with the corresponding virtual impedance correction component; the sending-end AC grid-side fault is not limited to a three-phase short-circuit fault. Under an asymmetric fault, under different degrees of grid-side voltage drop, the wind turbine can also be operated without being disconnected from the grid and power can be transmitted to the AC system as much as possible by inputting the virtual impedance control; and the application scenario is not limited to weak AC systems such as new energy at the sending end, but it is more difficult for such systems to cross the sending-end fault. This method can also be applied to strong AC systems at the receiving end; the application scenario is not limited to the sending-end fault crossing. This strategy can also be used in conjunction with energy-consuming devices to achieve the receiving-end fault crossing.

[0102] The above scheme, through a sending-end MMC fault ride-through method based on virtual impedance provided by the present invention, can reduce the stringent requirements of low-through on the PI (Proportional Integral) parameters of the internal and external loops when the low-through current margin is small. By inserting a virtual resistor, the sending-end low-through can be effectively achieved, and the sending-end fault ride-through can be achieved without adding corresponding electrical components. The virtual impedance control introduced also enhances the system circulating current suppression effect. Moreover, it can be applied to fault ride-through in multiple scenarios such as the sending and receiving ends according to actual needs.

[0103] Figure 6 FIG. 1 is a flow chart of another method for fault riding through a sending-end MMC based on virtual impedance provided by the present invention. Figure 6 As shown above Figure 1 The specific implementation of step 110 may include the following steps:

[0104] In step 111, a Park transformation is performed on the AC component of the bridge arm current in the sending-end MMC to obtain a direct-axis current component and a quadrature-axis current component.

[0105] It should be noted that the bridge arm current in the sending-end MMC may include the a-phase bridge arm current, the b-phase bridge arm current and the c-phase bridge arm current, and the Park transformation is used to transform the AC component of the a-phase bridge arm current, the AC component of the b-phase bridge arm current and the AC component of the c-phase bridge arm current to obtain the direct-axis current component and the quadrature-axis current component.

[0106] For example, Figure 7 As shown, Figure 7 The present invention provides a schematic diagram of a modulation voltage correction amount of a three-phase bridge arm in a sending-end MMC using a virtual impedance, and uses Park transformation (abc→dq) to convert the AC component i of the a-phase bridge arm current into za , the AC component of the b-phase bridge arm current i zb and the AC component of the c-phase bridge arm current i zc Transformation to obtain the direct axis current component i zd and the quadrature-axis current component i zq (i.e. i zj is the AC component of the current between the bridge arms, j can be a, b or c, i zd 、i zq are the d-axis and q-axis components after dq change).

[0107] In step 112 , a direct-axis voltage component and a quadrature-axis voltage component are calculated based on the direct-axis current component, the quadrature-axis current component, and a virtual impedance coefficient.

[0108] Wherein, the virtual impedance coefficient includes a virtual resistance coefficient and a virtual reactance coefficient;

[0109] Possible implementations of this step may include the following steps:

[0110] The product of the direct-axis current component and the virtual resistance coefficient is filtered to obtain the voltage corresponding to the virtual resistance; the product of the quadrature-axis current component and the virtual reactance coefficient is filtered to obtain the voltage corresponding to the virtual reactance; the difference between the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the direct-axis voltage component, and the sum of the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the quadrature-axis voltage component.

[0111] For example, still Figure 7 For example, the direct axis current component i zd Multiply by K R (K R is the virtual resistance coefficient), the direct axis current component i can be filtered by a first-order low-pass filter. zd and virtual resistance coefficient K R The product of is filtered to obtain the voltage corresponding to the virtual resistance, and the quadrature axis current component i zq Multiply by K X (K X is the virtual reactance coefficient), the direct axis current component i can be filtered by a first-order low-pass filter. zq and virtual reactance coefficient K X The product of the virtual resistance and the virtual reactance is filtered to obtain the voltage corresponding to the virtual reactance, and the difference between the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is taken as the direct axis voltage component U vird , the sum of the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is taken as the quadrature axis voltage component U virq (i.e. K R is the virtual resistance coefficient, K X is the virtual reactance coefficient, the virtual resistance and the virtual reactance are subtracted to obtain the additional modulation wave d-axis component, and the virtual resistance and the virtual reactance are added to obtain the additional modulation wave q-axis component). The transfer function of the first-order low-pass filter can be G is the gain coefficient, T is the inertia time constant, and s is the complex frequency domain variable. Figure 8 This is a schematic diagram of a virtual impedance equivalent circuit provided by the present invention, such as Figure 8 As shown, i zj is the AC component of the bridge arm current (i.e. the AC component of the current between the bridge arms), u zj is the modulation voltage correction of the three-phase bridge arm (i.e. the modulation wave correction after the virtual impedance), j can be a, b or c, and the AC component of the bridge arm current passes through the virtual resistor R v and virtual inductance L v To obtain the modulation voltage correction value u of the three-phase bridge arm zj .like Figure 9 As shown, Figure 9This is a virtual impedance control principle diagram provided by the present invention, where K is the virtual impedance coefficient, and the virtual impedance coefficient is followed by a ramp function (i.e., the virtual impedance is directly input, and the modulation voltage correction amount of the three-phase bridge arm corrects the modulation voltage of the three-phase bridge arm to obtain the corrected modulation voltage. When the virtual impedance is exited, the modulation voltage correction amount of the three-phase bridge arm is adjusted by the ramp function (i.e., d / dt) so that the modulation voltage correction amount of the three-phase bridge arm does not directly become zero) to reduce the step effect on the system modulation wave after the virtual impedance is input or removed.

[0112] In step 113, an inverse Peek transform is performed on the direct-axis voltage component and the quadrature-axis voltage component to obtain a modulation voltage correction value of the three-phase bridge arm in the sending-end MMC.

[0113] For example, still Figure 7 As an example, the direct axis voltage component U is transformed using the inverse Pike transform (dq→abc) vird and the quadrature axis voltage component U virq The modulation voltage correction value of the three-phase bridge arm in the sending-end MMC is obtained by transformation, that is, the modulation voltage correction value u of the a-phase bridge arm za , the modulation voltage correction value u of the b-phase bridge arm zb and the modulation voltage correction value u of the c-phase bridge arm zc The modulation voltage correction amount of the three-phase bridge arm is subsequently adjusted through a set function link (i.e., a ramp function), which can achieve rapid input when a grid-side low-voltage breakover is detected, stable output during a fault, and slow output during a fault exit, thereby reducing the step effect on the system modulation wave caused by the input or removal of the virtual impedance.

[0114] Figure 10 This is a flow chart of a method for determining the modulation voltage of a three-phase bridge arm provided by the present invention, such as Figure 10 As shown above Figure 1 The method for determining the modulation voltage of the three-phase bridge arm in step 130 may include the following steps:

[0115] In S1 , based on the actual value and reference value of the bridge arm current in the sending-end MMC, a standby direct-axis voltage reference value, a direct-axis voltage actual value, a standby quadrature-axis voltage reference value, and a quadrature-axis voltage actual value are obtained.

[0116] A possible implementation method of this step is to output the direct-axis voltage actual value using a proportional-integral algorithm based on the direct-axis actual value and the direct-axis reference value of the bridge arm current in the sending-end MMC; output the quadrature-axis voltage actual value using a proportional-integral algorithm based on the quadrature-axis actual value and the quadrature-axis reference value of the bridge arm current in the sending-end MMC; and perform current inner-loop decoupling on the direct-axis actual value and the quadrature-axis actual value to obtain a standby direct-axis voltage reference value and a standby quadrature-axis voltage reference value, respectively.

[0117] For example, Figure 11 As shown, Figure 11 The present invention provides a method for fault riding through the sending-end MMC based on virtual impedance. The schematic diagram of the inner loop current control of the virtual impedance is shown. The actual value i of the direct axis current of the bridge arm in the sending-end MMC is nd and the direct axis reference value i nd_ref The difference is input into the proportional integral algorithm, and the proportional integral algorithm outputs the actual value of the direct axis voltage; the actual value of the quadrature axis current i nq and quadrature axis reference value i nq_ref The difference is input into the proportional integral algorithm, and the proportional integral algorithm outputs the actual value of the quadrature axis voltage. nd Multiply by ωL, (i.e., decouple the direct axis actual value from the current inner loop) to obtain the standby quadrature axis voltage reference value, and then use the quadrature axis actual value i nq Multiply by ωL, (i.e. the actual value of the quadrature axis i nq Perform current inner loop decoupling) to obtain the direct-axis voltage reference value to be used.

[0118] In S2 , a direct-axis voltage reference value is calculated based on the standby direct-axis voltage reference value, the direct-axis voltage actual value, and a feedforward amount of the direct-axis voltage actual value.

[0119] For example, still Figure 11 As an example, by obtaining the standby direct-axis voltage reference value, the direct-axis voltage actual value and the feedforward value u of the direct-axis voltage actual value cnd The difference between the direct axis voltage reference value u nd_ref .

[0120] In S3 , a quadrature-axis voltage reference value is calculated based on the standby quadrature-axis voltage reference value, the quadrature-axis voltage actual value, and a feedforward amount of the quadrature-axis voltage actual value.

[0121] For example, still Figure 11 As an example, by obtaining the standby quadrature axis voltage reference value, the quadrature axis voltage actual value and the feedforward value u of the quadrature axis voltage actual value cnq The difference between the two values ​​is used to obtain the quadrature axis voltage reference value u nq_ref .

[0122] In S4, an inverse Peek transform is performed on the direct-axis voltage reference value and the quadrature-axis voltage reference value to obtain the modulation voltage of the three-phase bridge arm.

[0123] It should be noted that by performing an inverse Pike transform on the direct-axis voltage reference value and the quadrature-axis voltage reference value, the modulation voltage reference value of the three-phase bridge arm is obtained, and the modulation voltage of the three-phase bridge arm is obtained by subtracting the modulation voltage reference value of the three-phase bridge arm from the DC voltage of the sending-end MMC.

[0124] For example, still Figure 11For example, the direct axis voltage reference value u is obtained by using the inverse Pike transformation (dq→abc). nd_ref and the quadrature axis voltage reference value u nq_ref Transform to obtain the modulation voltage reference value u of the a-phase bridge arm na_ref , the modulation voltage reference value u of the b-phase bridge arm nb_ref and the modulation voltage reference value u of the c-phase bridge arm nc_ref , the modulation voltage reference value u of the a-phase bridge arm na_ref The DC voltage U of the sending end MMC dc / 2 The difference between the two is used as the modulation voltage of the a-phase bridge arm and the modulation voltage reference value u of the b-phase bridge arm. nb_ref The DC voltage U of the sending end MMC dc / 2 The difference between the two is used as the modulation voltage of the b-phase bridge arm and the modulation voltage reference value u of the c-phase bridge arm. nc_ref The DC voltage U of the sending end MMC dc / 2 The difference is used as the modulation voltage of the c-phase bridge arm to obtain the modulation voltage of the three-phase bridge arm. After detecting that the low-through signal flag changes from 0 to 1, the corresponding virtual impedance is input, that is, the modulation wave is superimposed with the corresponding virtual impedance correction component (that is, the modulation voltage correction value u of the a-phase bridge arm). za , the modulation voltage correction value u of the b-phase bridge arm zb and the modulation voltage correction value u of the c-phase bridge arm zc ), the flag signal is generated by judging the voltage amplitude of the grid side. When the voltage amplitude drops to the set value, the flag signal is 1 and the virtual impedance (i.e. the modulation voltage correction value u of the a-phase bridge arm) is input. za , the modulation voltage correction value u of the b-phase bridge arm zb and the modulation voltage correction value u of the c-phase bridge arm zc ), through the modulation voltage correction value u of the a-phase bridge arm za The modulation voltage of the phase a bridge arm is corrected to obtain the corrected modulation voltage of the phase a bridge arm, and the modulation voltage correction value u of the phase b bridge arm is obtained. zb The modulation voltage of the b-phase bridge arm is corrected to obtain the corrected modulation voltage of the b-phase bridge arm, and the modulation voltage correction value u of the c-phase bridge arm is obtained. zc The modulation voltage of the phase C bridge arm is corrected to obtain the corrected modulation voltage of the phase C bridge arm. The corrected modulation voltages of the phase A bridge arm, the corrected modulation voltages of the phase B bridge arm, and the corrected modulation voltages of the phase C bridge arm are modulated using a modulation strategy (i.e., a modulation wave algorithm) to obtain a trigger signal. This trigger signal triggers the submodule in the transmitting MMC, causing the transmitting MMC to undervoltage ride-through fault. When the undervoltage ride-through ends, the flag signal is 0, and the corresponding virtual impedance is exited.

[0125] Example 2:

[0126] Based on the same inventive concept, Figure 12A block diagram of a sending-end MMC fault ride-through system based on virtual impedance provided by the present invention is shown in FIG. Figure 12 As shown, the system may include:

[0127] The correction value generating unit 1210 is configured to generate a modulation voltage correction value of the three-phase bridge arm in the sending-end MMC using a virtual impedance based on the AC component of the bridge arm current in the sending-end MMC;

[0128] A state determining unit 1202 is configured to determine a state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC;

[0129] The voltage adjustment correction unit 1230 is configured to correct the modulation voltage of the three-phase bridge arm based on the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC when the state of the AC side of the sending-end MMC is a fault state, so as to obtain a corrected modulation voltage;

[0130] The fault ride-through unit 1240 is configured to control the sending-end MMC to ride through a fault on the AC side based on the corrected modulation voltage.

[0131] Optionally, Figure 13 A block diagram of a correction amount generating unit provided by the present invention, such as Figure 13 As shown, the correction value generating unit 1210 may include:

[0132] The current component determination module 1211 is used to perform Park transformation on the AC component of the bridge arm current in the sending-end MMC to obtain a direct-axis current component and a quadrature-axis current component;

[0133] a voltage component determination module 1212, configured to calculate a direct-axis voltage component and a quadrature-axis voltage component based on the direct-axis current component, the quadrature-axis current component, and a virtual impedance coefficient;

[0134] The correction amount determination module 1213 is used to perform an inverse Peek transform on the direct-axis voltage component and the quadrature-axis voltage component to obtain the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC.

[0135] Optionally, the virtual impedance coefficient includes a virtual resistance coefficient and a virtual reactance coefficient;

[0136] The voltage component determination module 1212 is specifically configured to:

[0137] Filter the product of the direct axis current component and the virtual resistance coefficient to obtain the voltage corresponding to the virtual resistance;

[0138] Filter the product of the quadrature-axis current component and the virtual reactance coefficient to obtain the voltage corresponding to the virtual reactance;

[0139] The difference between the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the direct-axis voltage component, and the sum of the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is used as the quadrature-axis voltage component.

[0140] Optionally, the state determining unit 1220 is specifically configured to:

[0141] When the AC voltage amplitude is less than a preset voltage threshold, it is determined that the state of the AC side of the sending-end MMC is a fault state.

[0142] Optionally, the fault ride-through unit 1240 is specifically configured to:

[0143] Based on the corrected modulation voltage, a modulation wave algorithm is used to generate a modulation wave of the three-phase bridge arm in the sending-end MMC;

[0144] Based on the modulation wave of the three-phase bridge arm in the sending-end MMC, each phase bridge arm in the sending-end MMC is controlled respectively, so that the sending-end MMC can cross the fault on the AC side.

[0145] Optionally, the system further includes: a modulation voltage determination unit; the modulation voltage determination unit includes:

[0146] A voltage parameter determination module is used to obtain a standby direct-axis voltage reference value, a direct-axis voltage actual value, a standby quadrature-axis voltage reference value, and a quadrature-axis voltage actual value based on the actual value and reference value of the bridge arm current in the sending-end MMC;

[0147] a direct-axis voltage reference value determining module, configured to calculate a direct-axis voltage reference value based on the standby direct-axis voltage reference value, the direct-axis voltage actual value, and a feedforward amount of the direct-axis voltage actual value;

[0148] a quadrature-axis voltage reference value determination module, configured to calculate a quadrature-axis voltage reference value based on the standby quadrature-axis voltage reference value, the quadrature-axis voltage actual value, and a feedforward amount of the quadrature-axis voltage actual value;

[0149] The modulation voltage determination module is used to perform an inverse Pike transformation on the direct-axis voltage reference value and the quadrature-axis voltage reference value to obtain the modulation voltage of the three-phase bridge arm.

[0150] Optionally, the voltage parameter determination module is specifically configured to:

[0151] Based on the direct-axis actual value and the direct-axis reference value of the bridge arm current in the sending-end MMC, the direct-axis voltage actual value is output using a proportional-integral algorithm;

[0152] Based on the quadrature-axis actual value and the quadrature-axis reference value of the bridge arm current in the sending-end MMC, the quadrature-axis voltage actual value is output using a proportional-integral algorithm;

[0153] The direct-axis actual value and the quadrature-axis actual value are subjected to current inner loop decoupling to obtain a standby direct-axis voltage reference value and a standby quadrature-axis voltage reference value, respectively.

[0154] Example 3:

[0155] Based on the same inventive concept, the present invention also provides a computer device, such as Figure 14 As shown, the computer device includes a processor and a memory, wherein the memory is used to store a computer program, wherein the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits, or a processor.

[0156] An application-specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, etc., which is the computing core and control core of the terminal, is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a computer storage medium to implement a corresponding method flow or corresponding function, so as to implement the steps of a sending-end MMC fault ride-through method based on virtual impedance in the above-mentioned embodiment.

[0157] Example 4:

[0158] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium herein can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides storage space, which stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium herein can be a high-speed RAM memory or a non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of a sending-end MMC fault ride-through method based on virtual impedance in the above-mentioned embodiment.

[0159] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0160] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0161] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0162] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0163] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A sending-end MMC fault ride-through method based on virtual impedance, characterized in that: The method comprises: Based on the AC component of the bridge arm current in the sending-end MMC, a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC is generated by using virtual impedance; Determining the state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC; When the state of the AC side of the sending-end MMC is a fault state, based on the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC, the modulation voltage of the three-phase bridge arm is corrected to obtain a corrected modulation voltage; Based on the corrected modulation voltage, the sending-end MMC is controlled to cross the fault on the AC side.

2. The method according to claim 1, characterized in that The method of generating a modulation voltage correction amount of a three-phase bridge arm in the sending-end MMC by using a virtual impedance based on an AC component of a bridge arm current in the sending-end MMC comprises: Perform Park transformation on the AC component of the bridge arm current in the sending-end MMC to obtain the direct-axis current component and the quadrature-axis current component; Based on the direct-axis current component, the quadrature-axis current component and the virtual impedance coefficient, a direct-axis voltage component and a quadrature-axis voltage component are calculated respectively; The direct-axis voltage component and the quadrature-axis voltage component are subjected to an inverse Park transformation to obtain a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC.

3. The method according to claim 2, characterized in that The virtual impedance coefficient includes a virtual resistance coefficient and a virtual reactance coefficient; The method of calculating the direct-axis voltage component and the quadrature-axis voltage component based on the direct-axis current component, the quadrature-axis current component and the virtual impedance coefficient comprises: The product of the direct axis current component and the virtual resistance coefficient is filtered to obtain the voltage corresponding to the virtual resistance; Filter the product of the quadrature-axis current component and the virtual reactance coefficient to obtain the voltage corresponding to the virtual reactance; The difference between the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is taken as the direct-axis voltage component, and the sum of the voltage corresponding to the virtual resistance and the voltage corresponding to the virtual reactance is taken as the quadrature-axis voltage component.

4. The method according to claim 1, characterized in that: The determining the state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC includes: When the AC voltage amplitude is less than a preset voltage threshold, it is determined that the state of the AC side of the sending-end MMC is a fault state.

5. The method according to claim 1, characterized in that The controlling the sending-end MMC to cross the fault on the AC side based on the corrected modulation voltage includes: Based on the corrected modulation voltage, a modulation wave algorithm is used to generate a modulation wave of a three-phase bridge arm in the sending-end MMC; Based on the modulation wave of the three-phase bridge arm in the sending-end MMC, each phase bridge arm in the sending-end MMC is controlled respectively, so that the sending-end MMC can cross the fault on the AC side.

6. The method according to claim 1, characterized in that The method for determining the modulation voltage of the three-phase bridge arm includes: Based on the actual value and reference value of the bridge arm current in the sending-end MMC, a standby direct-axis voltage reference value, a direct-axis voltage actual value, a standby quadrature-axis voltage reference value, and a quadrature-axis voltage actual value are obtained; Calculating a direct-axis voltage reference value based on the standby direct-axis voltage reference value, the direct-axis voltage actual value, and a feedforward amount of the direct-axis voltage actual value; Calculating a quadrature-axis voltage reference value based on the standby quadrature-axis voltage reference value, the quadrature-axis voltage actual value, and a feedforward amount of the quadrature-axis voltage actual value; An inverse Parker transformation is performed on the direct-axis voltage reference value and the quadrature-axis voltage reference value to obtain a modulation voltage of the three-phase bridge arm.

7. The method according to claim 6, characterized in that The method of obtaining a standby direct-axis voltage reference value, a direct-axis voltage actual value, a standby quadrature-axis voltage reference value, and a quadrature-axis voltage actual value based on the actual value and reference value of the bridge arm current in the sending-end MMC comprises: Based on the direct-axis actual value and the direct-axis reference value of the bridge arm current in the sending-end MMC, the direct-axis voltage actual value is outputted using a proportional-integral algorithm; Based on the quadrature-axis actual value and the quadrature-axis reference value of the bridge arm current in the sending-end MMC, the quadrature-axis voltage actual value is outputted using a proportional-integral algorithm; The direct-axis actual value and the quadrature-axis actual value are subjected to current inner loop decoupling to obtain a standby direct-axis voltage reference value and a standby quadrature-axis voltage reference value, respectively.

8. A sending-end MMC fault ride-through system based on virtual impedance, characterized in that: The system comprises: A correction amount generating unit, used for generating a modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC by using a virtual impedance based on an AC component of the bridge arm current in the sending-end MMC; A state determination unit, configured to determine the state of the AC side of the sending-end MMC based on the AC voltage amplitude of the sending-end MMC; The voltage adjustment correction unit is used to correct the modulation voltage of the three-phase bridge arm based on the modulation voltage correction amount and the modulation voltage correction amount of the three-phase bridge arm in the sending-end MMC when the state of the AC side of the sending-end MMC is a fault state, so as to obtain a corrected modulation voltage; A fault ride-through unit is used to control the sending-end MMC to ride through the fault on the AC side based on the corrected modulation voltage.

9. A computer device, characterized in that: include: one or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the sending-end MMC fault ride-through method based on virtual impedance as described in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the sending-end MMC fault ride-through method based on virtual impedance as described in any one of claims 1 to 7 is implemented.

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