Converter fault ride-through method and system based on dynamic virtual impedance parameters

Abstract

The embodiment of the invention discloses a converter fault ride-through method and system based on a dynamic virtual impedance parameter, and relates to the technical field of power electronics, and the method comprises the steps: latching the virtual internal potential amplitude of a converter and the angular velocity of a system before a fault when the voltage amplitude of a grid-connected point is detected to be lower than a preset voltage threshold value; calculating d-axis and q-axis fault current components which are expected to flow through the converter by using latch data, a current grid-connected point voltage amplitude, a virtual impedance initial value before a fault and controller output delay, calculating to obtain a three-phase fault current maximum peak value, comparing the three-phase fault current maximum peak value with a maximum current which can be borne by the converter, and determining the current value of the converter. And according to a comparison result, an adjustment coefficient and an impedance proportionality coefficient, a virtual resistor and a virtual inductor are dynamically calculated and updated, new d-axis and q-axis current reference values are calculated together with a latched virtual internal potential amplitude and d-axis and q-axis voltages of the current grid-connected point, and the new d-axis and q-axis current reference values are input into a current inner loop controller to control the output of the converter.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a converter fault ride-through method and system based on dynamic virtual impedance parameters. Background Art

[0002] With the rapid development of renewable energy, grid-connected converters are increasingly being used in new power systems. Grid-connected converters are prone to overcurrent in the event of a grid short-circuit fault, and virtual impedance is often used to limit the short-circuit current. Maximizing the reactive power support of grid-connected converters while ensuring safe operation, maintaining the safety of the converter's internal power electronic components, and ensuring the fault ride-through capability of renewable energy grid-connected systems remain key challenges in converter applications. Summary of the Invention

[0003] The main purpose of the present invention is to provide a converter fault ride-through method and system based on dynamic virtual impedance parameters to achieve stable control of the grid-type converter during fault ride-through.

[0004] To achieve the above objectives, the present application provides, in a first aspect, a converter fault ride-through method based on dynamic virtual impedance parameters, the method comprising:

[0005] When it is detected that the voltage amplitude of the grid connection point is lower than the preset voltage threshold, it is determined that a grid fault has occurred, and the converter virtual internal potential amplitude and system angular velocity before the fault are latched;

[0006] Calculating a d-axis fault current component and a q-axis fault current component expected to flow through the converter using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay;

[0007] Calculating a maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, comparing the maximum peak value of the three-phase fault current with a maximum current that the converter can withstand, and dynamically calculating and updating a virtual resistance and a virtual inductance based on the comparison result and a preset adjustment coefficient and an impedance proportional coefficient;

[0008] The dynamically updated virtual resistance and virtual inductance, together with the latched virtual internal potential amplitude and the d-axis voltage and q-axis voltage of the current grid-connected point, are used to calculate new d-axis current reference values ​​and q-axis current reference values, and the new d-axis current reference values ​​and q-axis current reference values ​​are input into the current inner loop controller of the converter to control the output of the converter during a fault.

[0009] Optionally, the preset voltage threshold is ninety percent of the rated voltage of the converter.

[0010] Optionally, the controller output delay is equal to twice pi divided by the controller frequency.

[0011] Optionally, the adjustment coefficient is determined as follows:

[0012] When the maximum peak value of the three-phase fault current is less than the maximum current that the converter can withstand, the adjustment coefficient takes a value of one;

[0013] When the maximum peak value of the three-phase fault current is greater than or equal to the maximum current that the converter can withstand, the adjustment coefficient is equal to the maximum peak value of the three-phase fault current divided by the maximum current that the converter can withstand.

[0014] Optionally, the virtual resistance is equal to the difference between the virtual internal potential amplitude and the voltage amplitude measured at the current grid connection point, divided by the product of the adjustment coefficient, the maximum current that the converter can withstand, and the square root of the sum of one and the square of the impedance proportionality coefficient;

[0015] The virtual inductance is equal to the impedance proportionality coefficient multiplied by the virtual resistance.

[0016] Optionally, the impedance proportionality coefficient ranges from 5 to 10.

[0017] A second aspect of the present application provides a converter fault ride-through system based on dynamic virtual impedance parameters, comprising:

[0018] A fault detection module is used to determine that a grid fault has occurred when it detects that the voltage amplitude at the grid connection point is lower than a preset voltage threshold;

[0019] A parameter latching module is used to latch the converter virtual internal potential amplitude and system angular velocity before the fault occurs when a fault occurs;

[0020] a fault current prediction module, configured to calculate a d-axis fault current component and a q-axis fault current component expected to flow through the converter by using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay;

[0021] a virtual impedance dynamic calculation module, configured to calculate a maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, compare the maximum peak value of the three-phase fault current with the maximum current that the converter can withstand, and dynamically calculate and update the virtual resistance and virtual inductance based on the comparison result and a preset adjustment coefficient and impedance proportional coefficient;

[0022] a current reference generation module, configured to calculate a new d-axis current reference value and a q-axis current reference value using the dynamically updated virtual resistance and virtual inductance, the latched virtual internal potential amplitude, and the d-axis voltage and q-axis voltage of the current grid connection point;

[0023] The current controller is configured to receive the new d-axis current reference value and the q-axis current reference value and control the output of the converter during a fault.

[0024] The present application provides a method and system for fault riding of a converter based on dynamic virtual impedance parameters. The method determines that a fault has occurred in the power grid when it is detected that the voltage amplitude of the grid connection point is lower than a preset voltage threshold, and latches the converter virtual internal potential amplitude and system angular velocity before the fault; calculates the d-axis fault current component and q-axis fault current component expected to flow through the converter by using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay; calculates the maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, compares the maximum peak value of the three-phase fault current with the maximum current that the converter can withstand, and calculates the maximum peak value of the three-phase fault current based on the comparison. The virtual resistance and virtual inductance are dynamically calculated and updated based on the comparison results and the preset adjustment coefficient and impedance proportional coefficient; the dynamically updated virtual resistance and virtual inductance, together with the latched virtual internal potential amplitude and the d-axis voltage and q-axis voltage of the current grid-connected point, are calculated to obtain new d-axis current reference values ​​and q-axis current reference values, and the new d-axis current reference values ​​and q-axis current reference values ​​are input into the current inner loop controller of the converter to control the output of the converter during the fault period; stable control of the grid-type converter during the fault ride-through period can be achieved, the virtual impedance can be dynamically adjusted at the moment of the fault, and the output current during the fault period can be limited while providing reactive support to the greatest extent, thereby avoiding the problem of converter overcurrent. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] in:

[0027] Figure 1 A schematic structural diagram of a converter fault ride-through system based on dynamic virtual impedance parameters provided by an embodiment of the present application;

[0028] Figure 2A schematic diagram of a circuit topology of a grid-type converter provided in an embodiment of the present application;

[0029] Figure 3 A control block diagram of a meshed VSG provided in an embodiment of the present application;

[0030] Figure 4 A flow chart of a converter fault ride-through method based on dynamic virtual impedance parameters provided in an embodiment of the present application;

[0031] Figure 5 A flow chart of another converter fault ride-through method based on dynamic virtual impedance parameters provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0033] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0034] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0035] The VSC-HVDC (Voltage Source Converter High Voltage Direct Current) mentioned in the embodiments of the present application is a high-voltage direct current transmission technology implemented using a voltage source converter. Compared with traditional direct current transmission technology, flexible direct current transmission has the advantages of flexible regulation, high control accuracy, and small impact on the power grid. It is particularly suitable for scenarios such as renewable energy grid connection, urban power grid power supply, and submarine cable transmission. With the transformation of the global energy structure and the intelligent upgrade of the power system, flexible direct current transmission technology is gradually becoming the new favorite of the power industry. Flexible direct current transmission (VSC-HVDC) is based on high-voltage direct current transmission of current source converters. It is a third-generation direct current transmission technology with fully controlled devices such as IGBT as core power devices. Compared with conventional direct current transmission (LCC-HVDC), flexible direct current transmission has strong advantages in reactive power compensation capability, no need for supporting power supply, no commutation failure, and flexible power control.

[0036] The present invention aims to provide a method for dynamically adjusting virtual impedance to achieve stable control of a grid-type converter during fault ride-through. By calculating the fault current at the moment of the fault and dynamically adjusting the virtual impedance based on the comparison result between the fault current and the maximum current that the converter can withstand, the output current during the fault period is limited while providing reactive power support to the greatest extent, thereby avoiding the problem of converter overcurrent.

[0037] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0038] Figure 1 This is a schematic diagram of a converter fault ride-through system based on dynamic virtual impedance parameters provided by an embodiment of the present application. Figure 1 As shown, the system 100 includes:

[0039] The fault detection module 110 is configured to determine that a grid fault has occurred when it detects that the voltage amplitude at the grid connection point is lower than a preset voltage threshold;

[0040] The parameter latch module 120 is used to latch the virtual internal potential amplitude and system angular velocity of the converter before the fault occurs when the fault occurs;

[0041] a fault current prediction module 130 for calculating a d-axis fault current component and a q-axis fault current component expected to flow through the converter using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay;

[0042] A virtual impedance dynamic calculation module 140 is configured to calculate a maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, compare the maximum peak value of the three-phase fault current with the maximum current that the converter can withstand, and dynamically calculate and update the virtual resistance and virtual inductance based on the comparison result and a preset adjustment coefficient and impedance proportional coefficient;

[0043] The current reference generation module 150 is configured to calculate a new d-axis current reference value and a new q-axis current reference value by using the dynamically updated virtual resistance and virtual inductance, the latched virtual internal potential amplitude, and the d-axis voltage and q-axis voltage of the current grid connection point;

[0044] The current controller 160 is configured to receive the new d-axis current reference value and the q-axis current reference value, and control the output of the converter during a fault.

[0045] The system 100 in the embodiment of the present application can be applied to an offshore wind power flexible DC grid-connected system.

[0046] Optionally, the current controller 160 is a proportional-integral controller.

[0047] Optionally, the system 100 further includes:

[0048] A voltage and current sensor 170 is used to monitor the voltage of the grid connection point and the current of the converter;

[0049] The signal processing unit 180 is used to process the signals collected by the voltage and current sensors for use by the fault detection module, the fault current prediction module and the current reference generation module.

[0050] Optionally, the virtual impedance dynamic calculation module 140 includes an impedance limiter, which is used to ensure that the updated virtual resistance and virtual inductance do not exceed the design limit of the converter.

[0051] The converter in the embodiment of the present application may be a meshed converter. In order to more clearly illustrate the system structure and related solutions, the system structure and method steps are further explained below in conjunction with a topology diagram and a control block diagram.

[0052] See also Figure 2 , is a circuit topology diagram of a grid-type converter provided in an embodiment of the present application.

[0053] like Figure 2 As shown in the figure, the circuit structure specifically includes the following main parts:

[0054] Grid-type converter:

[0055] lie in Figure 2The left side consists of power electronic switching devices, which are used to control the conversion and transmission of electrical energy;

[0056] The converter contains an inductor L f and capacitor C f , these components are used for filtering to smooth the output current and voltage waveforms.

[0057] PCC:

[0058] lie in Figure 2 The center is the point where the converter output is connected to the grid;

[0059] At PCC, the voltage V abc These measurements are used for power calculations and fault detection.

[0060] Power calculation module:

[0061] Located after the PCC, it is used to calculate the active power and reactive power at the grid connection point;

[0062] The power calculation results can be used to guide the virtual synchronous generator (VSG) control strategy to achieve precise control of the converter output.

[0063] Power grid:

[0064] lie in Figure 2 The right side of the , consists of multiple parallel loads, each load is composed of Z g , Z load express;

[0065] V g_a 、V g_b 、V g_c Represents the three-phase voltage in the power grid.

[0066] See also Figure 3 , which is a meshed VSG control block diagram provided in an embodiment of the present application.

[0067] like Figure 3 As shown in the figure, the inverter power synchronization control loop uses VSG (virtual synchronous machine) control to generate virtual voltage amplitude and phase, where P n , Q n is the active power and reactive power measured at the grid connection point, P n *, Q n * is the active and reactive power setting value, V n * is the voltage setting value, Dp is the damping coefficient, ω0 is the system angular velocity; θ n is the virtual internal potential phase angle, E n is the virtual internal potential amplitude, and s represents the differential operator.

[0068] The virtual impedance control part simulates the stator resistance and synchronous reactance of the synchronous machine by controlling the output voltage of the VSG. Its control equation is:

[0069]

[0070] in and is the voltage reference value of the d-axis and q-axis, and is the current reference value of the d-axis and q-axis, R v and L v Indicates virtual impedance.

[0071] The method in the embodiment of the present application is mainly to adjust the internal potential control strategy according to the voltage measured at the grid connection point during the fault period, and when it is detected that the voltage amplitude of the grid connection point (PCC) is less than the preset voltage threshold, the current internal potential amplitude E is latched. n and frequency (angular velocity), and dynamically update the virtual impedance. Figure 5 The processing flow shown dynamically updates the virtual impedance.

[0072] The above-mentioned preset voltage threshold, i.e., the PCC voltage drop judgment threshold, can be adjusted according to the rated values ​​of different grid voltage levels, for example, it can be set to 90% of the rated voltage.

[0073] See also Figure 4 , is a flow chart of a converter fault ride-through method based on dynamic virtual impedance parameters provided by an embodiment of the present application, such as Figure 4 As shown, the method includes:

[0074] 401. When it is detected that the voltage amplitude of the grid connection point is lower than the preset voltage threshold, it is determined that a grid fault occurs, and the converter virtual internal potential amplitude and system angular velocity before the fault are latched.

[0075] Specifically, the voltage at the grid connection point can be detected in real time to determine whether the grid is faulty, and the internal potential control strategy can be adjusted according to the voltage measured at the grid connection point during the fault period.

[0076] The above-mentioned preset voltage threshold can be adjusted according to the rated value of different grid voltage levels, for example, it can be set to 90% of the rated voltage of the converter. That is, when the voltage amplitude of the grid connection point (PCC) is detected to be less than 90% of the rated value, the current internal potential amplitude E is latched. n and frequency, where the frequency can be understood as the angular velocity of the system.

[0077] 402. Calculate the d-axis fault current component and the q-axis fault current component expected to flow through the converter using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay.

[0078] 403. Calculate the maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, compare the maximum peak value of the three-phase fault current with the maximum current that the converter can withstand, and dynamically calculate and update the virtual resistance and virtual inductance based on the comparison result and the preset adjustment coefficient and impedance proportional coefficient.

[0079] In an optional implementation, the adjustment coefficient is determined as follows:

[0080] When the maximum peak value of the three-phase fault current is less than the maximum current that the converter can withstand, the adjustment coefficient takes a value of one;

[0081] When the maximum peak value of the three-phase fault current is greater than or equal to the maximum current that the converter can withstand, the adjustment coefficient is equal to the maximum peak value of the three-phase fault current divided by the maximum current that the converter can withstand.

[0082] The above impedance proportional coefficient can be set as needed.

[0083] 404. Calculate the new d-axis current reference value and q-axis current reference value using the dynamically updated virtual resistance and virtual inductance, together with the latched virtual internal potential amplitude and the d-axis voltage and q-axis voltage of the current grid-connected point, and input the new d-axis current reference value and q-axis current reference value into the current inner loop controller of the converter to control the output of the converter during the fault period.

[0084] The method in the embodiment of the present application can be executed based on the system in the embodiment of the present application, for example Figure 1 or Figure 2 The system shown in Figure 1. The specific processing steps involved can be referred to Figure 4 The specific steps in the illustrated embodiment will not be repeated here.

[0085] In order to more clearly illustrate the method in the embodiment of the present application, the calculation method involved in the method flow is specifically introduced below.

[0086] See also Figure 5 , which is a flow chart of another converter fault ride-through method based on dynamic virtual impedance parameters provided by an embodiment of the present application, such as Figure 5 As shown, specific methods may include:

[0087] 1. is the three-phase instantaneous voltage reference value, according to the internal potential amplitude E after latching n and the virtual internal potential phase angle θ n Generate, the expression is:

[0088]

[0089] Three-phase instantaneous voltage reference value After dq transformation, the voltage reference values ​​of d-axis and q-axis can be obtained, which are the corresponding values ​​in the control equation. and

[0090] 2. The fault current I of the converter d-axis and q-axis during the fault period can be calculated according to the following equations: d ′ and I q ′, which is used to calculate the subsequent virtual impedance update value:

[0091]

[0092] Among them, E n is the internal potential amplitude after latching, V m is the voltage amplitude measured at the grid connection point (PCC), θ n is the virtual internal potential phase angle, R v and L v It represents the initial value of the virtual impedance before the fault occurs, and γ is the controller output delay, which is determined by the control delay of the controller.

[0093] In the embodiment of the present application, the virtual impedance under steady-state working conditions is determined in the initial design stage according to the load characteristics of the access system. The controller output delay γ can be calculated according to the controller frequency, γ=2pi / controller frequency.

[0094] 3. The calculated d and q axis fault currents I d ′ and I q ' Perform reverse Pike transformation to obtain the three-phase fault current, and record the maximum peak value of the three-phase fault current as I abcmax , I max The maximum current that the converter can withstand (for example, 1.2 times the rated current) is used. The virtual impedance is updated according to the following formula:

[0095]

[0096] Wherein k1 is the impedance proportional coefficient, which is usually a value given in the early stage of grid-type converter control design, for example, it can be set between 5 and 10.

[0097] 4. Substitute the updated virtual impedance parameters into the control equation and solve it with the following formula:

[0098]

[0099] in and is the current reference value of the d-axis and q-axis, s represents the differential operator, I d (0) and I q (0) represents the d-axis and q-axis currents measured by PCC at the time of fault, E n is the internal potential amplitude after latching, R v and L v In the above formula, the calculated current reference value is input into the current inner loop to obtain the output voltage u of the d-axis and q-axis. d and u q ; A PI controller can be used, and the specific control equation can be as follows:

[0100]

[0101] After the Park inverse transformation, the three-phase reference voltage is obtained, which is used to control the output of the converter during the fault period.

[0102] The main innovations of the methods and systems in the embodiments of the present application are:

[0103] 1) Determine the internal potential control strategy based on the measured voltage at the grid connection point, and lock the internal potential when the voltage drops to avoid voltage fluctuations during the fault period;

[0104] 2) According to the aforementioned calculation formula, the fault current is calculated using the virtual impedance parameters before the fault, and the virtual impedance parameters are dynamically updated based on the relationship between the fault current and the maximum current that the converter can withstand;

[0105] 3) The current reference values ​​of the d-axis and q-axis are solved by the updated virtual impedance parameters to achieve stable control of the converter fault ride-through and limit the fault current.

[0106] The method and system in the embodiments of the present application propose a virtual impedance parameter update strategy during a fault, improve the control stability of the grid-type converter during fault ride-through, realize the dynamic update of the virtual impedance parameters, and achieve effective limitation of the output current during the fault while providing reactive support to the greatest extent.

[0107] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A converter fault ride-through method based on dynamic virtual impedance parameters, characterized in that: The method comprises: When it is detected that the voltage amplitude of the grid connection point is lower than the preset voltage threshold, it is determined that a grid fault has occurred, and the converter virtual internal potential amplitude and system angular velocity before the fault are latched; Calculating a d-axis fault current component and a q-axis fault current component expected to flow through the converter using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay; Calculating a maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, comparing the maximum peak value of the three-phase fault current with a maximum current that the converter can withstand, and dynamically calculating and updating a virtual resistance and a virtual inductance based on the comparison result and a preset adjustment coefficient and an impedance proportional coefficient; The dynamically updated virtual resistance and virtual inductance, together with the latched virtual internal potential amplitude and the d-axis voltage and q-axis voltage of the current grid-connected point, are used to calculate new d-axis current reference values ​​and q-axis current reference values, and the new d-axis current reference values ​​and q-axis current reference values ​​are input into the current inner loop controller of the converter to control the output of the converter during a fault.

2. The converter fault ride-through method based on dynamic virtual impedance parameters according to claim 1, characterized in that: The preset voltage threshold is ninety percent of the rated voltage of the converter.

3. The converter fault ride-through method based on dynamic virtual impedance parameters according to claim 1, characterized in that: The controller output delay is equal to twice pi divided by the controller frequency.

4. The converter fault ride-through method based on dynamic virtual impedance parameters according to claim 1, characterized in that: The adjustment coefficient is determined as follows: When the maximum peak value of the three-phase fault current is less than the maximum current that the converter can withstand, the adjustment coefficient takes a value of one; When the maximum peak value of the three-phase fault current is greater than or equal to the maximum current that the converter can withstand, the adjustment coefficient is equal to the maximum peak value of the three-phase fault current divided by the maximum current that the converter can withstand.

5. The converter fault ride-through method based on dynamic virtual impedance parameters according to claim 1 or 4, characterized in that: The virtual resistance is equal to the difference between the virtual internal potential amplitude and the voltage amplitude measured at the current grid connection point, divided by the product of the adjustment coefficient, the maximum current that the converter can withstand, and the square root of the sum of one and the square of the impedance proportionality coefficient; The virtual inductance is equal to the impedance proportionality coefficient multiplied by the virtual resistance.

6. The converter fault ride-through method based on dynamic virtual impedance parameters according to claim 1, characterized in that: The impedance proportionality coefficient ranges from 5 to 10.

7. A converter fault ride-through system based on dynamic virtual impedance parameters, characterized in that: include: A fault detection module is used to determine that a grid fault has occurred when it detects that the voltage amplitude at the grid connection point is lower than a preset voltage threshold; A parameter latching module is used to latch the converter virtual internal potential amplitude and system angular velocity before the fault occurs when a fault occurs; a fault current prediction module, configured to calculate a d-axis fault current component and a q-axis fault current component expected to flow through the converter by using the latched virtual internal potential amplitude, the voltage amplitude measured at the current grid connection point, the initial value of the virtual impedance before the fault occurs, and the controller output delay; a virtual impedance dynamic calculation module, configured to calculate a maximum peak value of the three-phase fault current based on the d-axis fault current component and the q-axis fault current component, compare the maximum peak value of the three-phase fault current with the maximum current that the converter can withstand, and dynamically calculate and update the virtual resistance and virtual inductance based on the comparison result and a preset adjustment coefficient and impedance proportional coefficient; a current reference generation module, configured to calculate a new d-axis current reference value and a q-axis current reference value using the dynamically updated virtual resistance and virtual inductance, the latched virtual internal potential amplitude, and the d-axis voltage and q-axis voltage of the current grid connection point; The current controller is configured to receive the new d-axis current reference value and the q-axis current reference value and control the output of the converter during a fault.

8. The converter fault ride-through system based on dynamic virtual impedance parameters according to claim 7, characterized in that: The current controller is a proportional-integral controller.

9. The converter fault ride-through system based on dynamic virtual impedance parameters according to claim 7, characterized in that: The system further comprises: A voltage and current sensor, used to monitor the voltage of the grid connection point and the current of the converter; A signal processing unit is used to process the signals collected by the voltage and current sensors for use by the fault detection module, the fault current prediction module and the current reference generation module.

10. The converter fault ride-through system based on dynamic virtual impedance parameters according to claim 7, characterized in that: The virtual impedance dynamic calculation module includes an impedance limiter for ensuring that the updated virtual resistance and virtual inductance do not exceed the limitations of the converter design.

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