New energy fault equivalent impedance remodeling control method and device for distance protection performance improvement

Abstract

The application relates to a new energy fault equivalent impedance remodeling control method and device for distance protection performance improvement. The method realizes new energy converter fault characteristic simulation and distance protection active support through the cooperative control of voltage memory parameter extraction, constant virtual internal potential construction, positive / negative sequence inductive impedance remodeling and current loop adaptive amplitude limiting, compensates phase jump based on pre-fault voltage memory, constructs constant virtual internal potential, and controls positive / negative sequence inductive impedance, so that the fault equivalent characteristics of the converter are consistent with the inductive impedance characteristics under the constant internal potential of a synchronous generator, the problems of distance protection misoperation and refusal caused by the capacitive nature of the fault impedance of the new energy converter and the phase mutation of the internal potential are solved from the root, the fault characteristic demand of the existing distance protection to the back power supply can be correctly matched, the protection algorithm does not need to be adjusted, the protection device does not need to be transformed, the distance protection equipment in operation can be directly compatible, and the dual consideration of protection support and equipment safe operation is realized.

Description

Technical Field

[0001] This application relates to the field of power electronic control support and protection technology, specifically to a new energy fault equivalent impedance reshaping control method and device for improving distance protection performance. Background Technology

[0002] With the large-scale integration of new energy power generation such as wind and solar power into the power grid, the fault ride-through control response of the converter, as the core interface equipment for new energy grid connection, directly determines the reliability of the grid relay protection. In particular, grid-connected new energy converters are widely used in the power system, and their fault ride-through control response time highly overlaps with the operating period of the power system distance protection. Since the fault ride-through control characteristics directly determine the reliability of the distance protection of new energy transmission lines, coordinated optimization of control and protection is an important factor in stabilizing the power system.

[0003] Existing technical solutions for improving distance protection performance in new energy grid-connected systems through control and protection coordination mainly fall into two categories:

[0004] One approach is to actively inject non-power frequency characteristic signals into the converter to form fault difference characteristics and achieve fault location, or to establish active boundaries to support fault identification across the entire line. However, while this method can improve fault identification performance, it does not fully consider secondary problems such as harmonics and system oscillations, and may easily deteriorate the system's power quality and operational stability.

[0005] Secondly, the existing protection identification logic is matched by adjusting the characteristics of the converter fault current phase and equivalent impedance. However, most solutions only optimize the negative sequence impedance angle, while not adequately considering the positive sequence impedance characteristics that distance protection depends on under symmetrical faults. Some solutions also require obtaining the current phase of the opposite system, which relies on communication upgrades to achieve current phase matching, but the engineering upgrade costs are high and the implementation complexity is large.

[0006] Meanwhile, traditional distance protection is designed based on the inherent characteristics of constant internal potential and inductive internal impedance after a synchronous generator fault. However, when a new energy converter fails, the equivalent impedance is prone to capacitive behavior and the internal potential phase changes abruptly. This directly leads to frequent failures and maloperations of distance protection for new energy transmission lines, making it difficult to ensure the stable operation of distance protection and the safe operation of power electronic equipment.

[0007] Therefore, there is an urgent need for a new energy fault equivalent impedance reshaping control method to solve the above problems and improve the distance protection performance of new energy transmission lines. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, this application provides a method and device for controlling the equivalent impedance reshaping of new energy faults to improve distance protection performance, specifically adopting the following technical solution: A fault equivalent impedance reshaping control method for new energy sources aimed at improving distance protection performance, the method comprising the following steps: Based on the output phase angle of the converter phase-locked loop and dq Positive sequence voltage in rotating coordinate system dq The electrical parameters of the terminal voltage are obtained by extracting the shaft component, and the electrical parameters include at least the positive sequence voltage amplitude before the fault and the phase change after the fault. When the positive sequence voltage of the converter drops below the threshold, the voltage phase jump variable after the fault is compensated based on the extracted electrical parameters of the terminal voltage, and a constant virtual internal potential is obtained. When the converter enters the fault ride-through control phase, calculations are performed based on a constant virtual internal potential using both positive-sequence inductive impedance control and negative-sequence inductive impedance control. dq The current reference value in the rotating coordinate system includes at least a positive sequence current reference value and a negative sequence current reference value. The current reference value exceeding the current withstand constraint is scaled proportionally using a current loop limiting method to obtain the current reference value after limiting. The control signal of the converter is output based on the current reference value after the current is limited, so as to support the distance protection action.

[0009] Optional: The phase angle of the converter phase-locked loop output is... dq Positive sequence voltage in rotating coordinate system dq The steps for extracting the electrical parameters of the machine terminal voltage after a fault by shaft component extraction include: Real-time acquisition of the converter's grid-connected voltage and phase angle of the phase-locked loop output; By combining the grid-connected voltage and the phase angle of the phase-locked loop output, and using a dual synchronous rotating coordinate system to achieve decoupled control of positive and negative sequence voltages, the positive sequence voltage at the generator terminal is obtained. dq Axial components; Based on the positive sequence voltage at the terminal after the fault dq The positive sequence voltage amplitude is obtained from the axis component, and the positive sequence voltage amplitude is delayed by a preset power frequency period and sent to the sample and hold circuit. When the sample-and-hold circuit receives a fault trigger signal, it latches the delayed positive sequence voltage amplitude to obtain the positive sequence voltage amplitude before the fault. The phase angle of the positive sequence voltage output from the phase-locked loop is delayed by a preset power frequency period and then sent to the sample-and-hold circuit. When the sample-and-hold circuit receives a fault trigger signal, it obtains the phase change after the fault based on the delayed positive sequence voltage phase angle and the positive sequence voltage phase angle output by the phase-locked loop in real time.

[0010] Furthermore, the sample-and-hold circuit uses an integer multiple of the power frequency cycle to delay the input of the positive sequence voltage phase angle, and uses the positive sequence voltage phase angle before the integer multiple of the power frequency cycle as the initial phase angle. Combined with the rated power frequency angular velocity rotation calculation, the phase angle reference value is obtained. The phase angle reference value is subtracted from the positive sequence voltage phase angle output by the phase-locked loop in real time to obtain the phase change after the fault.

[0011] Furthermore: when compensating for voltage phase jump variables after a fault based on the extracted terminal voltage electrical parameters, the following applies to the post-fault voltage phase jump variables: dq The voltage coordinate transformation of the axis components involves rotating the current positive-sequence voltage phasor in the opposite direction by a corresponding angle based on the phase change after the fault, so that the virtual internal potential reaches the phase of the positive-sequence voltage before the fault.

[0012] Optional: When calculated based on a constant virtual internal potential controlled by positive-sequence inductive impedance dq When the positive sequence current reference value is in a rotating coordinate system, where dq The calculation process for the positive sequence current reference value in the rotating coordinate system is as follows: ; In the above formula I d1 for d Off-axis positive sequence current control reference value I q1 for q Off-axis positive sequence current control reference value E d1 For virtual internal potential d Axial components, E q1 For virtual internal potential q Axial components, U d1 For the positive sequence voltage at the machine terminal d Axial components, U q1 For the positive sequence voltage at the machine terminal q Axial components, Z 1 represents the configurable positive-sequence fault equivalent impedance. This corresponds to the positive sequence impedance angle.

[0013] Optional: Calculation via negative sequence inductive impedance control dq When the negative sequence current reference value is in a rotating coordinate system, where dq The calculation process for the negative sequence current reference value in the rotating coordinate system is as follows: ; In the above formula I d2 for d Under-shaft negative sequence current control reference value I q2 forq Under-shaft negative sequence current control reference value U d2 For the negative sequence voltage at the machine terminal d Axial components, U q2 For the negative sequence voltage at the machine terminal q Axial components, Z 2 represents the configurable negative sequence fault equivalent impedance. This corresponds to the negative sequence impedance angle.

[0014] Optionally: The step of scaling the amplitude of the current reference value exceeding the current withstand constraint using a current loop limiting method includes: Get dq The positive sequence current reference value and negative sequence current reference value in the rotating coordinate system are determined, and the maximum allowable output phase current amplitude is determined. Will dq The positive-sequence current reference values ​​and negative-sequence current reference values ​​in the rotating coordinate system are converted to the three-phase coordinate system to obtain the current amplitude of each phase. When the amplitude of each phase current is less than or equal to the maximum allowable output phase current amplitude, no amplitude scaling is performed; When the amplitude of any phase current exceeds the maximum permissible output phase current amplitude, the current scaling factor is determined by the ratio of the maximum permissible output phase current amplitude to the maximum phase current amplitude, and the current scaling factor is applied to... dq The positive-sequence current reference value and the negative-sequence current reference value in the rotating coordinate system are limited and scaled.

[0015] Optional: Will dq When converting the positive-sequence current reference values ​​and negative-sequence current reference values ​​in the rotating coordinate system to the three-phase coordinate system, the calculation process for the current amplitude of each phase is as follows: ; In the above formula I d1 for d Off-axis positive sequence current control reference value I q1 for q Off-axis positive sequence current control reference value I d2 for d Under-shaft negative sequence current control reference value I q2 for q Under-shaft negative sequence current control reference value for dq The phase difference between positive-sequence current and negative-sequence current in a rotating coordinate system.

[0016] Optional: When the control signal of the converter is output based on the current reference value after current limiting, the equivalent sequence impedance of the converter after current loop limiting is expressed as: ; In the above formula Z 1 represents the set positive sequence fault equivalent impedance. Z 2 represents the set negative sequence fault equivalent impedance. Z 1.fix This is the equivalent positive-sequence impedance of the converter after current loop limiting. Z 2.fix This is the equivalent negative sequence impedance of the converter after current loop limiting. k fix This is the current scaling factor.

[0017] Furthermore, this application also discloses a fault equivalent impedance reshaping control device for new energy sources aimed at improving distance protection performance, the device comprising: The parameter extraction module is used to extract parameters based on the output phase angle of the converter phase-locked loop and... dq Positive sequence voltage in rotating coordinate system dq The electrical parameters of the terminal voltage are obtained by extracting the shaft component, and the electrical parameters include at least the positive sequence voltage amplitude before the fault and the phase change after the fault. The parameter compensation module is used to compensate for the voltage phase jump variable after the fault based on the extracted electrical parameters of the generator terminal voltage when the positive sequence voltage of the converter drops below the threshold, and to construct a constant virtual internal potential. The parameter calculation module is used to calculate the parameters based on a constant virtual internal potential through positive-sequence inductive impedance control and negative-sequence inductive impedance control when the converter enters the fault ride-through control phase. dq The current reference value in the rotating coordinate system includes at least a positive sequence current reference value and a negative sequence current reference value. The parameter limiting module is used to scale the current reference value that exceeds the current tolerance constraint by means of current ring limiting to obtain the current reference value after limiting. The protection action module is used to output control signals to the converter based on the current reference value after the limit is set, so as to support the distance protection action.

[0018] The technical solution of this application achieves the following beneficial effects: The new energy fault equivalent impedance reshaping control method of this application achieves fault characteristic simulation and active distance protection support for new energy converters through coordinated control of voltage memory parameter extraction, constant virtual internal potential construction, positive / negative sequence inductive impedance reshaping, and current loop adaptive limiting. This method constructs a constant virtual internal potential based on voltage memory compensation phase jump before the fault, and, in conjunction with positive / negative sequence inductive impedance control, ensures that the fault equivalent characteristics of the converter are consistent with the inductive impedance characteristics of a synchronous generator under constant internal potential. This fundamentally solves the distance protection issues caused by impedance bias and internal potential phase abrupt changes in new energy converter faults. This method addresses the issues of protection failure and maloperation. Furthermore, it proactively outputs inductive positive-sequence and negative-sequence impedances for both asymmetrical and symmetrical faults to accurately match the fault characteristics of the underlying power supply required by existing distance protection systems. This eliminates the need to adjust the protection algorithm or modify the protection device, ensuring direct compatibility with existing distance protection equipment. The method employs a current ring limiting mechanism to proportionally scale the amplitude of over-limit currents. Only the current amplitude needs adjustment, without altering the current phase. This ensures that the converter output current does not exceed the equipment's current tolerance while maintaining the equivalent inductive impedance characteristics, achieving a balance between protection support and safe equipment operation. Attached Figure Description

[0019] Figure 1 This application presents a method for improving the fault equivalent impedance reshaping control of new energy sources to enhance distance protection performance. The flowchart.

[0020] Figure 2 This is a structural diagram of the grid-connected new energy converter system in the embodiments of this application.

[0021] Figure 3 This is a control structure diagram of the positive sequence voltage change extraction module in the embodiments of this application.

[0022] Figure 4 This is a schematic diagram of virtual internal potential phase compensation in an embodiment of this application.

[0023] Figure 5 The equivalent circuit and phasor diagram of the positive-sequence inductive impedance control in the embodiments of this application are shown below. Figure 5 (a) is the equivalent circuit diagram using positive-sequence inductive impedance control. Figure 5 (b) is a phasor diagram of the virtual internal potential and terminal voltage.

[0024] Figure 6 The equivalent circuit and phasor diagram of the negative-sequence inductive impedance control in the embodiments of this application are shown below. Figure 6 (a) is the equivalent circuit diagram using negative sequence inductive impedance control. Figure 6 (b) is a phasor diagram of the virtual internal potential and terminal voltage.

[0025] Figure 7This is a structural diagram of the simulation model of the power grid system in the embodiments of this application.

[0026] Figure 8 This is a comparison diagram showing the effects of different control strategies on the short-circuit current and equivalent impedance angle of new energy sources under three-phase short-circuit faults in the embodiments of this application. Figure 8 (a) shows the effect of the traditional strategy on the short-circuit current of new energy sources. Figure 8 (b) shows the effect of the equivalent impedance angle under the traditional strategy. Figure 8 (c) is a graph showing the effect of the method on the short-circuit current of new energy sources in this embodiment. Figure 8 (d) is a diagram showing the effect of the equivalent impedance angle of the method in this embodiment.

[0027] Figure 9 This is a comparison diagram showing the effects of different control strategies on the short-circuit current and equivalent impedance angle of new energy sources under two-phase short-circuit faults in the embodiments of this application. Figure 9 (a) shows the effect of the traditional strategy on the short-circuit current of new energy sources. Figure 9 (b) shows the effect of the equivalent impedance angle under the traditional strategy. Figure 9 (c) is a graph showing the effect of the method on the short-circuit current of new energy sources in this embodiment. Figure 9 (d) is a diagram showing the effect of the equivalent impedance angle of the method in this embodiment.

[0028] Figure 10 This is a diagram showing the phase comparison results of different control strategies under a three-phase short-circuit fault in the embodiment of this application.

[0029] Figure 11 This is a diagram showing the phase comparison results of different control strategies under a two-phase three-phase short-circuit fault in the embodiments of this application.

[0030] Figure 12 This is a structural diagram of a new energy fault equivalent impedance reshaping control device for improving distance protection performance in the embodiments of this application.

[0031] Figure 13 This is a structural diagram of an electronic device according to an embodiment of this application. Detailed Implementation

[0032] The present application will now be further described with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application and should not be construed as limiting the scope of protection of the present application. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present application.

[0033] like Figure 1As shown, this embodiment specifically discloses a new energy fault equivalent impedance reshaping control method for improving distance protection performance. This method can utilize existing distance protection devices, making the new energy converter analogous to a synchronous machine with constant potential and inductive internal impedance. By optimizing the fault control strategy of the new energy converter, it treats the new energy converter as a voltage source with inductive internal reactance, thus meeting the requirements of distance protection for power supply fault characteristics and achieving active support for distance protection actions without requiring adjustments to the protection algorithm. The method includes the following steps: First, extract the amplitude and phase changes of the terminal voltage after the fault: This embodiment focuses on inductive impedance reshaping control for a grid-connected renewable energy converter. The topology of this grid-connected renewable energy converter is as follows: Figure 2 As shown. This grid-connected new energy converter adopts a grid voltage-oriented method and utilizes a Double Synchronous Reference Frame (DDSRF) to achieve positive and negative sequence decoupling control. Under the synchronous rotating coordinate system... d The axis coincides with the positive sequence component of the grid voltage, and the rotation direction of this coordinate system follows... q Axis Leading d The convention of 90° axis.

[0034] Specifically, this embodiment is based on the output phase angle of the converter phase-locked loop and... dq Positive sequence voltage in rotating coordinate system dq The electrical parameters of the terminal voltage are obtained by extracting the shaft components. These electrical parameters include at least the positive sequence voltage amplitude before the fault and the phase change after the fault.

[0035] The specific process for extracting the electrical parameters of the terminal voltage after the fault in this step includes: First, the grid-connected voltage and the phase angle of the phase-locked loop (PLL) output of the converter are acquired in real time. This embodiment considers the feasibility of extracting the voltage change at the generator terminals after a fault, and preferably utilizes the output phase angle of the converter's PLL and... dq Rotating coordinate system dq Axis components are used to construct a positive-sequence voltage extraction module, which is as follows: Figure 3 As shown, it consists of two parallel branches: an amplitude extraction branch and a phase extraction branch. The amplitude extraction branch includes a dual synchronous rotating coordinate transformation (DDSRF), an amplitude calculation unit, and a sample-and-hold circuit with a delay, which can extract and latch the positive sequence voltage amplitude before the fault. The phase extraction branch includes a phase-locked loop (PLL), a sample-and-hold circuit with a delay, an integrator, and a difference calculation unit, which can extract the reference phase angle trajectory before the fault and calculate the phase change before and after the fault.

[0036] Secondly, by combining the grid-connected voltage and the phase angle of the phase-locked loop output, positive-sequence and negative-sequence decoupling control is achieved using a dual synchronous rotating coordinate system to obtain the positive-sequence voltage at the generator terminal. dq Axial components.

[0037] Based on the positive sequence voltage at the terminal after the fault dq The positive sequence voltage amplitude is obtained from the shaft component and then sent to the sample-and-hold circuit after a preset power frequency period delay. Simultaneously, the positive sequence voltage phase angle output by the phase-locked loop is sent to the sample-and-hold circuit after a preset power frequency period delay. As a preferred embodiment, the sample-and-hold circuit in this example can memorize data using integer multiples of the power frequency period, such as 20, 40, or 60 ms, to avoid interference from fault transient fluctuations, stably extract the positive sequence voltage characteristics before the fault, and provide a reliable reference for subsequent control.

[0038] When the sample-and-hold circuit receives a fault trigger signal, it obtains the phase change after the fault based on the delayed positive-sequence voltage phase angle and the positive-sequence voltage phase angle output by the phase-locked loop in real time. Furthermore, in this embodiment, the sample-and-hold circuit uses an integer multiple of the power frequency cycle to delay the input of the positive-sequence voltage phase angle, and uses the positive-sequence voltage phase angle before the integer multiple of the power frequency cycle as the initial phase angle. A phase angle reference value is obtained by combining this with the rotation at the rated power frequency angular velocity. The difference between the phase angle reference value and the positive-sequence voltage phase angle output by the phase-locked loop in real time is used to obtain the phase change after the fault.

[0039] When the sample-and-hold circuit receives a fault trigger signal, it latches the delayed positive-sequence voltage amplitude to obtain the positive-sequence voltage amplitude before the fault. The sample-and-hold circuit is affected by the fault signal. F The control system can latch the voltage and phase angle values ​​before the fault occurs, and resume the follow mode after the fault disappears. It is the core of the module's memory. When a fault signal occurs... F When the input value changes from "0" to "1", indicating a fault condition, the current input value is memorized and output. The sample-and-hold circuit immediately latches the positive-sequence voltage amplitude just before the fault, ensuring the positive-sequence voltage is unaffected by voltage drops after the fault and providing a stable reference for constructing the virtual internal potential. Simultaneously, the sample-and-hold circuit latches the initial phase angle value before the fault, and the integrator uses this as a starting point, operating at the rated power frequency angular velocity. ω A reference phase angle is continuously generated to simulate the phase angle trajectory when there is no fault. After a fault, the voltage phase jumps, and the phase output of the phase-locked loop will track the new phase. The phase offset is obtained by calculating the difference between the two, which reflects the phase angle change before and after the fault.

[0040] When fault signal FWhen the value changes from "1" to "0", indicating a return to normal operation, the output value equals the current input value. This means the dq-axis component of the positive-sequence voltage at the generator terminal output by the DDSRF is used to calculate the positive-sequence voltage amplitude in real time. At this point, the sample-and-hold circuit is in follower mode, tracking the current voltage amplitude in real time. Furthermore, the phase angle of the voltage output tracked in real time by the phase-locked loop is also followed by the sample-and-hold circuit, and the phase angle generated by the integrator is almost synchronized with the phase-locked loop output. Considering the phase jump in the positive-sequence voltage at the generator terminal during the fault, the above-mentioned positive-sequence voltage change can be used to compensate for the phase change in the converter after the fault. dq The change in the position of the reference axis ensures that subsequent coordinate transformations are not affected by the dynamic process of the phase-locked loop, thus guaranteeing control accuracy.

[0041] Secondly, a constant virtual internal potential is constructed using voltage memory: In this embodiment, when the positive sequence voltage of the converter drops below the threshold, the converter's low-voltage-through control circuit will be triggered. The fault will cause a drop in the amplitude and a phase jump in the terminal voltage. Under traditional control, the port characteristics of the converter will deviate from the synchronous machine characteristics, which is not conducive to grid support and transient stability during the low-voltage-through period. At this time, it is necessary to compensate for the voltage phase jump after the fault based on the extracted terminal voltage electrical parameters and construct a constant virtual internal potential.

[0042] Specifically, in this embodiment, when compensating for the voltage phase jump variable after a fault based on the extracted electrical parameters of the terminal voltage, the following will be applied: dq The voltage coordinate transformation of the axis components involves rotating the current positive-sequence voltage phasor in the opposite direction by a corresponding angle based on the phase change after the fault, so that the virtual internal potential reaches the phase of the positive-sequence voltage before the fault.

[0043] Among them, virtual internal potential It can be represented as: ; In the above formula E d1 For virtual internal potential d Axial components, E q1 For virtual internal potential q Axial components, U d1 、U q1 For the positive sequence voltage at the machine terminal dq Axial components, U t1 This represents the positive sequence voltage amplitude at the generator terminal. U STO The positive sequence voltage amplitude before the fault is stored in the positive sequence voltage change extraction module. This represents the extracted positive-sequence voltage phase change.

[0044] As can be seen from the above expression for virtual internal potential, this embodiment aims to obtain a constant virtual internal potential. It is necessary to compensate for the voltage phase jump after the fault, that is, as follows Figure 4 The virtual internal potential phase compensation diagram shown reverses the rotation of the current positive-sequence voltage phasor through coordinate transformation. The angle is such that the virtual internal potential reaches the phase of the pre-fault positive sequence voltage. It should be noted that in the above expression for the virtual internal potential: ; It is dq The standard rotation matrix in the coordinate system, with the direction being counterclockwise.

[0045] When the above matrix is ​​transformed onto a two-dimensional column vector, such as [ U d1 ,U q1 ] T When this happens, the vector will be rotated counterclockwise around the origin (leading). Radius, to achieve phase compensation. Furthermore, The ratio of the positive sequence voltage amplitude at the machine terminal before and after the fault is used. Based on this ratio, the amplitude of the virtual internal potential is set to be the same as the voltage at the machine terminal before the fault, so that the amplitude of the virtual internal potential remains basically unchanged.

[0046] Based on the above steps, this embodiment can construct a virtual constant potential analogous to a synchronous machine, providing a reference value for the virtual constant internal potential to shape the equivalent inductive internal impedance of the converter. This allows the converter ports to be represented by a virtual constant potential and an equivalent internal inductive impedance, consistent with the classic model of a synchronous machine. This enables the power electronic converter to exhibit external characteristics similar to a synchronous machine, solving the problems of traditional converters lacking internal potential and having weak transient characteristics. It facilitates the design of strategies such as low-voltage control and virtual synchronization control, provides a stable control reference for the low-voltage control stage, and improves the robustness of transient control.

[0047] Reconstructing the equivalent inductive internal impedance of the converter during faults: In this embodiment, when the converter enters the fault ride-through control stage, the positive sequence current reference value and the negative sequence current reference value will be switched from steady-state power control to fault ride-through control. At this time, the positive sequence current reference value and the negative sequence current reference value are determined by the corresponding inductive impedance reshaping module.

[0048] Specifically, in this embodiment, the constant virtual internal potential is calculated using both positive-sequence inductive impedance control and negative-sequence inductive impedance control. dq The current reference value in the rotating coordinate system includes at least the positive sequence current reference value and the negative sequence current reference value.

[0049] Among them, such as Figure 5As shown in (a), it is an equivalent circuit using positive-sequence inductive impedance control. In this embodiment, by analogy with the circuit relationship between the internal potential and terminal voltage of a traditional synchronous generator, it can be equivalent to the existence of a series impedance Z1 between the virtual internal potential and the terminal voltage. At this time, the phasor relationship between the virtual internal potential and the terminal voltage is as follows: Figure 5 As shown in (b).

[0050] When calculated based on a constant virtual internal potential through positive sequence inductive impedance control dq When the positive sequence current reference value is in a rotating coordinate system, where dq The calculation process for the positive sequence current reference value in the rotating coordinate system is as follows: ; In the above formula I d1 for d Off-axis positive sequence current control reference value I q1 for q Off-axis positive sequence current control reference value E d1 For virtual internal potential d Axial components, E q1 For virtual internal potential q Axial components, U d1 For the positive sequence voltage at the machine terminal d Axial components, U q1 For the positive sequence voltage at the machine terminal q Axial components, Z 1 represents the configurable positive-sequence fault equivalent impedance. This corresponds to the positive sequence impedance angle.

[0051] As can be seen from the above calculation process of the positive sequence current reference value, the positive sequence current can be changed by giving different positive sequence impedances. dq The shaft component, in turn, changes the current phase. Therefore, by analogy with the physical characteristics of the internal subtransient / transient reactance after a synchronous machine fault, the positive sequence impedance angle can be designed as resistive-inductive to ensure that the converter output current, virtual internal potential, and terminal voltage phase are similar to the synchronous machine fault characteristics.

[0052] like Figure 6 As shown in (a), it is the equivalent circuit using negative-sequence inductive impedance control, which simulates the negative-sequence circuit of a synchronous machine. At this time, the negative-sequence electromotive force is 0, and the phasor relationship between the virtual internal potential and the terminal voltage is as follows. Figure 6 As shown in (b).

[0053] Calculations based on negative sequence inductive impedance control dq When the negative sequence current reference value is in a rotating coordinate system, where dqThe calculation process for the negative sequence current reference value in the rotating coordinate system is as follows: ; In the above formula I d2 for d Under-shaft negative sequence current control reference value I q2 for q Under-shaft negative sequence current control reference value U d2 For the negative sequence voltage at the machine terminal d Axial components, U q2 For the negative sequence voltage at the machine terminal q Axial components, Z 2 represents the configurable negative sequence fault equivalent impedance. This corresponds to the negative sequence impedance angle.

[0054] in ; The above formula is expressed as dq A standard rotation matrix in a coordinate system, with a clockwise direction. When this matrix transforms a two-dimensional column vector, such as […] U d ,U q ] T When this happens, the vector will be rotated clockwise around the origin (lagging). α 1 radian.

[0055] Then, current adaptive ring limiting control is performed: This embodiment addresses the issue of current exceeding limits during converter fault ride-through by utilizing a ring limiter for adaptive limiting. Specifically, this embodiment uses a current limiting circle as the limiting boundary. When the instantaneous value or vector amplitude of any phase current exceeds the equipment limiting boundary, the current reference value exceeding the current withstand constraint is scaled proportionally using a ring current limiting method to obtain a limited current reference value.

[0056] Specifically, the process of scaling the amplitude of the current reference value exceeding the current withstand constraint using a current loop limiting method in this embodiment includes: Get dq The positive sequence current reference value and negative sequence current reference value in the rotating coordinate system are determined, and the maximum allowable output phase current amplitude is determined.

[0057] Will dq The positive-sequence and negative-sequence current reference values ​​in the rotating coordinate system are transformed to the three-phase coordinate system to obtain the current amplitude of each phase. The calculation process for the current amplitude of each phase during the transformation is as follows: ; In the above formula I d1 for d Off-axis positive sequence current control reference value I q1 for q Off-axis positive sequence current control reference value I d2 for d Under-shaft negative sequence current control reference value I q2 for q Under-shaft negative sequence current control reference value for dq Positive sequence current in rotating coordinate system I d1 +jI q1 With negative sequence current I d2 +jI q2 phase difference, j It is the imaginary unit.

[0058] When the amplitude of each phase current is less than or equal to the maximum allowable output phase current amplitude, no amplitude scaling is performed.

[0059] When the amplitude of any phase current exceeds the maximum permissible output phase current amplitude, the current scaling factor is determined by the ratio of the maximum permissible output phase current amplitude to the maximum phase current amplitude, and the current scaling factor is applied to... dq The positive-sequence current reference value and the negative-sequence current reference value in the rotating coordinate system are limited and scaled.

[0060] This embodiment illustrates two scenarios: asymmetric faults and symmetric faults. For asymmetrical faults, the superposition of positive and negative sequence components will cause the peak current of one phase to be significantly higher than that of other phases, making it more prone to overcurrent risk. Therefore, amplitude limiting control needs to be implemented in the positive and negative sequence control loops to achieve current limiting. Under asymmetrical fault conditions... dq By converting the positive and negative sequence currents in the coordinate system to the three-phase coordinate system, the amplitudes of the three-phase currents in new energy sources can be calculated separately. I a , I b , I c .

[0061] This embodiment incorporates a current loop limiting control circuit to ensure that the maximum phase current amplitude does not exceed the allowable value: ; In the above formula Ik,fix This is the reference value for the subsequent current after the limiting. I max The maximum permissible output phase current amplitude is indicated by the subscript. k express d1 , q1 , d2 , q2 subscript fix This is represented as the output value under amplitude limiting control. k fix This indicates the current scaling factor.

[0062] Similarly, the superposition of positive and negative sequence components in a symmetrical fault will cause the current in one phase to exceed the limit. Therefore, current limiting control needs to be implemented in the positive and negative sequence control loops to achieve current limiting. However, since the three-phase currents are symmetrical under a symmetrical fault, the current limiting control will scale each phase current proportionally, i.e.: ; In the above formula I k,fix This is the reference value for the subsequent current after the limiting, with the subscript... k express d1 , q1 , d2 , q2 subscript fix This is represented as the output value under amplitude limiting control. k fix This indicates the current scaling factor.

[0063] Furthermore, in this embodiment, when the control signal of the converter is output based on the current reference value after current limiting, the equivalent sequence impedance of the converter after current loop limiting can be expressed as: ; In the above formula Z 1 represents the set positive sequence fault equivalent impedance. Z 2 represents the set negative sequence fault equivalent impedance. Z 1.fix This is the equivalent positive-sequence impedance of the converter after current loop limiting. Z 2.fix This is the equivalent negative sequence impedance of the converter after current loop limiting. k fix This is the current scaling factor.

[0064] The above steps directly limit the output current amplitude during fault ride-through, preventing overcurrent damage to power devices caused by excessive current and meeting the current withstand limit requirements of the equipment. This is the core protection element of fault ride-through control. Furthermore, based on the fault equivalent impedance control, the converter's internal equivalent impedance is already controlled to be inductive. The ring-type limiting control only reduces the current amplitude without changing the current ratio of each phase, i.e., it does not change the current phase and does not introduce additional phase disturbances. This avoids transient impacts caused by control strategy switching and maintains the grid's support capability. In this embodiment, the ring-type limiting device can be equivalently used to change the magnitude of the positive and negative sequence impedances. By changing the current amplitude through limiting control, the smooth adjustment of the converter's external equivalent impedance is indirectly achieved without additional strategy switching, improving control robustness.

[0065] Finally, distance protection is supported by limiting current: This embodiment outputs the converter's control signal based on the current reference value after amplitude limiting to support distance protection operation. Currently, existing distance protection operation logic determines the fault location by measuring the voltage-to-current ratio at the protection installation point and comparing it with the line's set impedance. This logic requires the power supply side to exhibit a constant potential and inductive impedance, while the phase relationship of the fault current must be stable. This embodiment, through the above process, enables the converter to exhibit fault external characteristics consistent with a synchronous machine. Even after amplitude limiting, the measured impedance still changes linearly with the fault distance, allowing the protection to correctly identify the fault location and operate. This ensures that the fault current amplitude is limited, preventing overcurrent damage to the converter's power devices, while fully preserving the current phase relationship and equivalent inductive impedance characteristics. The direction and impedance elements of the distance protection are not affected by amplitude limiting, and it can still operate correctly.

[0066] Furthermore, this embodiment uses a power grid system as an example for verification, wherein the square model of the power grid system is as follows: Figure 7 As shown in the diagram. This system is configured with 100 renewable energy converters, each with a capacity of 1MW, connected to a 35kV collection line and then to the grid via a 35kV / 220kV step-up transformer. The system's control parameters are as follows: the positive and negative sequence impedance angles in the inductive impedance control module are controlled at 81°, and the current limit is 1.2. pu The system's base power is selected as a rated capacity of 100MVA, with a leakage reactance of 0.05pu for the 220kV main transformer. The step-up transformer adopts a YN / d connection, and the impedance of the new energy transmission line is z. L1 =0.076+ j 0.338Ω / km, z L0 =0.228+ j 1.014Ω / km, line length is 80km. System-side power supply impedance is 9.458+. j69.716Ω. The protection range is defined as 85% of the total line length, where the positive sequence impedance of 85% of the line is 5.1680Ω. j 22.984Ω.

[0067] like Figure 8 and Figure 9 The figures show waveforms of the short-circuit current and equivalent impedance angle of new energy sources under three-phase and two-phase short-circuit faults, respectively. The traditional fault ride-through strategies used in the figures are increasing positive-sequence reactive current generation and absorbing negative-sequence reactive current. Combined with... Figure 8 and Figure 9 As shown, the equivalent impedance fluctuates significantly under traditional control strategies, even exhibiting capacitive characteristics, and the positive and negative sequence impedances are unequal. However, the equivalent impedance angles for both positive and negative sequences after a fault, achieved using the method in this embodiment, are close to 90°, exhibiting inductive characteristics, consistent with the impedance characteristics of a synchronous machine. Furthermore, in comparison... Figure 9 As can be seen in (a) and (c), the method in this embodiment achieves adaptive current limiting during asymmetrical faults, and the current amplitude of each phase is constrained to 1.2 times.

[0068] Furthermore, this embodiment verifies the improvement effect on distance protection performance using polarized voltage by setting different operating conditions.

[0069] Operating Condition 1: F1 metallic fault, m Side-direction protection. Its distance protection operating equation based on polarization voltage is: ; In the formula: To compensate for voltage, Polarization voltage, To protect the measuring current, Z m To measure impedance, Z set The setting impedance is used. The polarization voltage can be taken as the positive sequence voltage after the fault, the voltage of the healthy phase, and the memory voltage. For a three-phase short circuit at the outlet, the memory voltage is introduced as the polarization voltage to ensure directionality.

[0070] Combination Figure 10 As shown, this is a diagram illustrating the phase ratio between the compensation voltage and polarization voltage of the distance protection during a forward short circuit in a new energy transmission line. The operating range of the distance protection using the phase ratio of polarization voltage and compensation voltage is [-180, -90] and [90, 180], in degrees. It can be seen that under a three-phase short circuit, the existing reactive power priority strategy results in protection failure. However, the method in this embodiment operates correctly, and the voltage phase ratio results are all closer to 180 degrees, indicating sensitive and correct distance protection operation.

[0071] Operating Condition 2: F4 Metallic Fault n Side-reverse protection. For example... Figure 11 As shown, it is F4 Troubleshooting n The voltage phase ratio result diagram of the side protection shows that, compared with the existing control strategy, there is a reverse protection maloperation under two-phase short circuit. The protection phase ratio result of the method proposed in this embodiment is closer to 0 degrees, thus avoiding the reverse protection maloperation.

[0072] Furthermore, this embodiment verifies the performance improvement effect of the directional element by setting different operating conditions.

[0073] This embodiment is set F 1. Metallic faults, investigation m The directional discrimination of the side-positive directional protection is shown in Table 1, which presents the operation of the directional element under different fault ride-through control methods. To compare the impact of different low-passage control strategies on the protection, verification is performed under the following scenarios: Strategy 1 - No increase in positive-sequence reactive power and suppression of negative-sequence current; Strategy 2 - Increase in positive-sequence reactive power and suppression of negative-sequence current; Strategy 3 - Increase in positive-sequence reactive power and absorption of negative-sequence reactive power; Strategy 4 - The control method proposed in this embodiment.

[0074] Table 1 shows the voltage / current phase ratio results, representing the phase difference between zero-sequence voltage and zero-sequence current under single-phase grounding, the phase difference between negative-sequence voltage and negative-sequence current under two-phase short circuit, and the phase difference between the memory phase voltage and the phase current with zero-sequence compensation under three-phase short circuit. The operating region sensitivity angle for the voltage / current phase ratio results is set to 81 degrees, using the memory voltage directional element [-9, 171] and the zero-sequence and negative-sequence directional elements [171, -9], with units in degrees.

[0075] As shown in Table 1, the directional elements fail to operate when using strategies 2 and 3 for three-phase short circuits, and the directional elements using zero-sequence components operate correctly when using a single-phase ground fault. The directional elements may fail when using a strategy to suppress negative sequence for two-phase short circuits, while the directional elements operate correctly under the method proposed in this embodiment.

[0076]

[0077] In addition, such as Figure 11 As shown, this application also discloses a fault equivalent impedance reshaping control device for new energy sources aimed at improving distance protection performance, the device comprising: The parameter extraction module is used to extract parameters based on the output phase angle of the converter phase-locked loop and... dq Positive sequence voltage in rotating coordinate system dq The electrical parameters of the terminal voltage are obtained by extracting the shaft component, and the electrical parameters include at least the positive sequence voltage amplitude before the fault and the phase change after the fault. The parameter compensation module is used to compensate for the voltage phase jump variable after the fault based on the extracted electrical parameters of the generator terminal voltage when the positive sequence voltage of the converter drops below the threshold, and to construct a constant virtual internal potential. The parameter calculation module is used to calculate the parameters based on a constant virtual internal potential through positive-sequence inductive impedance control and negative-sequence inductive impedance control when the converter enters the fault ride-through control phase. dq The current reference value in the rotating coordinate system includes at least a positive sequence current reference value and a negative sequence current reference value. The parameter limiting module is used to scale the current reference value that exceeds the current tolerance constraint by means of current ring limiting to obtain the current reference value after limiting. The protection action module is used to output control signals to the converter based on the current reference value after the limit is set, so as to support the distance protection action.

[0078] The apparatus provided in this application embodiment can achieve... Figure 1 To avoid repetition, the various processes implemented in the method embodiments will not be described again here.

[0079] like Figure 12 As shown in the illustration, this application also provides an electronic device, including a processor and a memory, and a program or instructions stored in the memory and executable on the processor, which, when executed by the processor, implement as follows: Figure 1 The various processes of the method embodiments shown are all capable of achieving the same technical effect, and will not be described again here to avoid repetition.

[0080] This application embodiment also provides a readable storage medium storing a program or instructions that, when executed by a processor, implement the above-described functionality. Figure 1 The various processes described in the embodiments of the method described herein can achieve the same technical effect, and will not be repeated here to avoid repetition.

[0081] This application also provides a computer program product, including computer instructions, which, when executed by a processor, implement the above-described... Figure 1 The various processes described in the embodiments of the method described herein can achieve the same technical effect, and will not be repeated here to avoid repetition.

[0082] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. The sequence numbers of the above-described embodiments are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0083] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0084] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another device, or some features may be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0085] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units. They may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0086] In addition, each functional unit in the various embodiments of this application can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0087] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0088] Alternatively, if the integrated units described above are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a device (which may be a terminal or platform, etc.) to execute all or part of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0089] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for reshaping equivalent impedance during faults in new energy sources to improve distance protection performance, characterized in that, The method includes the following steps: Based on the output phase angle of the converter phase-locked loop and dq Positive sequence voltage in rotating coordinate system dq The electrical parameters of the terminal voltage are obtained by extracting the shaft component, and the electrical parameters include at least the positive sequence voltage amplitude before the fault and the phase change after the fault. When the positive sequence voltage of the converter drops below the threshold, the voltage phase jump variable after the fault is compensated based on the extracted electrical parameters of the terminal voltage, and a constant virtual internal potential is obtained. When the converter enters the fault ride-through control phase, calculations are performed based on a constant virtual internal potential using both positive-sequence inductive impedance control and negative-sequence inductive impedance control. dq The current reference value in the rotating coordinate system includes at least a positive sequence current reference value and a negative sequence current reference value. The current reference value exceeding the current withstand constraint is scaled proportionally using a current loop limiting method to obtain the current reference value after limiting. The control signal of the converter is output based on the current reference value after the current is limited, so as to support the distance protection action.

2. The new energy fault equivalent impedance reshaping control method according to claim 1, characterized in that, The output phase angle based on the converter phase-locked loop and dq Positive sequence voltage in rotating coordinate system dq The steps for extracting the electrical parameters of the machine terminal voltage after a fault by shaft component extraction include: Real-time acquisition of the converter's grid-connected voltage and phase angle of the phase-locked loop output; By combining the grid-connected voltage and the phase angle of the phase-locked loop output, and using a dual synchronous rotating coordinate system to achieve decoupled control of positive and negative sequence voltages, the positive sequence voltage at the generator terminal is obtained. dq Axial components; Based on the positive sequence voltage at the terminal after the fault dq The positive sequence voltage amplitude is obtained from the axis component, and the positive sequence voltage amplitude is delayed by a preset power frequency period and sent to the sample and hold circuit. When the sample-and-hold circuit receives a fault trigger signal, it latches the delayed positive sequence voltage amplitude to obtain the positive sequence voltage amplitude before the fault. The phase angle of the positive sequence voltage output from the phase-locked loop is delayed by a preset power frequency period and then sent to the sample-and-hold circuit. When the sample-and-hold circuit receives a fault trigger signal, it obtains the phase change after the fault based on the delayed positive sequence voltage phase angle and the positive sequence voltage phase angle output by the phase-locked loop in real time.

3. The new energy fault equivalent impedance reshaping control method according to claim 2, characterized in that, The sample-and-hold circuit uses an integer multiple of the power frequency cycle to delay the input of the positive sequence voltage phase angle, and uses the positive sequence voltage phase angle before the integer multiple of the power frequency cycle as the initial phase angle. It calculates the phase angle reference value by combining the rated power frequency angular velocity rotation, and obtains the phase change amount after the fault by subtracting the phase angle reference value from the positive sequence voltage phase angle output by the phase-locked loop in real time.

4. The new energy fault equivalent impedance reshaping control method according to claim 1, characterized in that, When compensating for voltage phase jump variables after a fault based on the extracted terminal voltage electrical parameters, the following applies to the post-fault voltage phase jump variables: dq The voltage coordinate transformation of the axis components involves rotating the current positive-sequence voltage phasor in the opposite direction by a corresponding angle based on the phase change after the fault, so that the virtual internal potential reaches the phase of the positive-sequence voltage before the fault.

5. The new energy fault equivalent impedance reshaping control method according to claim 1, characterized in that, When calculated based on a constant virtual internal potential through positive sequence inductive impedance control dq When the positive sequence current reference value is in a rotating coordinate system, where dq The calculation process for the positive sequence current reference value in the rotating coordinate system is as follows: ； In the above formula I d1 for d Off-axis positive sequence current control reference value I q1 for q Off-axis positive sequence current control reference value E d1 For virtual internal potential d Axial components, E q1 For virtual internal potential q Axial components, U d1 For the positive sequence voltage at the machine terminal d Axial components, U q1 For the positive sequence voltage at the machine terminal q Axial components, Z 1 represents the configurable positive-sequence fault equivalent impedance. This corresponds to the positive sequence impedance angle.

6. The new energy fault equivalent impedance reshaping control method according to claim 1, characterized in that, Calculations based on negative sequence inductive impedance control dq When the negative sequence current reference value is in a rotating coordinate system, where dq The calculation process for the negative sequence current reference value in the rotating coordinate system is as follows: ； In the above formula I d2 for d Under-shaft negative sequence current control reference value I q2 for q Under-shaft negative sequence current control reference value U d2 For the negative sequence voltage at the machine terminal d Axial components, U q2 For the negative sequence voltage at the machine terminal q Axial components, Z 2 represents the configurable negative sequence fault equivalent impedance. This corresponds to the negative sequence impedance angle.

7. The new energy fault equivalent impedance reshaping control method according to claim 1, characterized in that, The step of scaling the amplitude of the current reference value exceeding the current withstand constraint using a current loop limiting method includes: Get dq The positive sequence current reference value and negative sequence current reference value in the rotating coordinate system are determined, and the maximum allowable output phase current amplitude is determined. Will dq The positive-sequence current reference values ​​and negative-sequence current reference values ​​in the rotating coordinate system are converted to the three-phase coordinate system to obtain the current amplitude of each phase. When the amplitude of each phase current is less than or equal to the maximum allowable output phase current amplitude, no amplitude scaling is performed; When the amplitude of any phase current exceeds the maximum permissible output phase current amplitude, the current scaling factor is determined by the ratio of the maximum permissible output phase current amplitude to the maximum phase current amplitude, and the current scaling factor is applied to... dq The positive-sequence current reference value and the negative-sequence current reference value in the rotating coordinate system are limited and scaled.

8. The new energy fault equivalent impedance reshaping control method according to claim 7, characterized in that, Will dq When converting the positive-sequence current reference values ​​and negative-sequence current reference values ​​in the rotating coordinate system to the three-phase coordinate system, the calculation process for the current amplitude of each phase is as follows: ； In the above formula I d1 for d Off-axis positive sequence current control reference value I q1 for q Off-axis positive sequence current control reference value I d2 for d Under-shaft negative sequence current control reference value I q2 for q Under-shaft negative sequence current control reference value for dq The phase difference between positive-sequence current and negative-sequence current in a rotating coordinate system.

9. The new energy fault equivalent impedance reshaping control method according to claim 1, characterized in that, When the control signal of the converter is output based on the current reference value after current limiting, the equivalent sequence impedance of the converter after current loop limiting is expressed as: ； In the above formula Z 1 represents the set positive sequence fault equivalent impedance. Z 2 represents the set negative sequence fault equivalent impedance. Z 1.fix This is the equivalent positive-sequence impedance of the converter after current loop limiting. Z 2.fix This is the equivalent negative sequence impedance of the converter after current loop limiting. k fix This is the current scaling factor.

10. A new energy fault equivalent impedance reshaping control device for improving distance protection performance, characterized in that, The device includes: The parameter extraction module is used to extract parameters based on the output phase angle of the converter phase-locked loop and... dq Positive sequence voltage in rotating coordinate system dq The electrical parameters of the terminal voltage are obtained by extracting the shaft component, and the electrical parameters include at least the positive sequence voltage amplitude before the fault and the phase change after the fault. The parameter compensation module is used to compensate for the voltage phase jump variable after the fault based on the extracted electrical parameters of the generator terminal voltage when the positive sequence voltage of the converter drops below the threshold, and to construct a constant virtual internal potential. The parameter calculation module is used to calculate the parameters based on a constant virtual internal potential through positive-sequence inductive impedance control and negative-sequence inductive impedance control when the converter enters the fault ride-through control phase. dq The current reference value in the rotating coordinate system includes at least a positive sequence current reference value and a negative sequence current reference value. The parameter limiting module is used to scale the current reference value that exceeds the current tolerance constraint by means of current ring limiting to obtain the current reference value after limiting. The protection action module is used to output control signals to the converter based on the current reference value after the limit is set, so as to support the distance protection action.

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