Network-configuration type converter fault ride-through method and system based on dynamic virtual resistance control

Abstract

The present application relates to the technical field of grid-forming converter control, and particularly relates to a grid-forming converter fault ride-through method and system based on dynamic virtual resistance control, which comprises the following steps: adding a control link based on virtual impedance in a grid-forming converter control system; detecting the actual value of grid voltage to determine whether the grid voltage drops; detecting the current amplitude output by the grid-forming converter in real time to determine whether the current amplitude exceeds a set value; if one of the two conditions is met, starting the virtual impedance control link: performing stage-type current limiting control on the virtual resistance, and the size of the virtual resistance provided by the grid-forming converter to the power system is adjusted in real time according to the fault current amplitude; when the grid voltage recovers and the current amplitude is less than the set value, the stage-type current limiting control of the virtual resistance is exited. The present application can realize fault current limiting during grid-forming converter fault ride-through, thereby improving the fault ride-through capability and transient stability performance of the grid-forming converter.

Description

Technical Field

[0001] This invention relates to the field of grid-type converter control technology, and in particular to a fault ride-through method and system for grid-type converters based on dynamic virtual resistance control. Background Technology

[0002] Large-scale wind and solar renewable energy generation, connected to the grid via power electronic equipment, is gradually replacing traditional synchronous generators. Grid-type converters are particularly suitable for grids with low system strength, low physical inertia, and poor stability. Under short-circuit fault conditions, the rapid increase in short-circuit current poses a serious threat to the transient stability of the grid. Unlike synchronous generators, grid-type converters do not have an actual physical mechanical rotor and are limited by the overcurrent capacity of the semiconductor devices themselves. Therefore, they cannot utilize the fault response strategies of synchronous generators and face the risk of being disconnected from the grid due to overcurrent protection. Thus, during fault periods, grid-type converters must employ certain fault ride-through control methods to ensure continued stable operation when the grid encounters large disturbances.

[0003] Existing fault ride-through methods include direct current control strategies, which involve adding a limiting module to the converter's inner-loop current control to directly constrain the inner-loop current command value to control the short-circuit current. However, this method may lead to signal saturation or discontinuity, thus affecting the system's dynamic response and overall stability. Another approach employs a control mode switching strategy, which switches the control mode from grid-based control to grid-following control upon overcurrent detection, utilizing the current source characteristics of grid-following control to suppress fault current. However, this method loses the voltage / frequency support and advantages of grid-based control and requires precise fault timing detection. Therefore, there is an urgent need to propose a fault ride-through method based on grid-based control that does not affect the inner-loop current command.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a fault ride-through method and system for grid-type converters based on dynamic virtual resistance control, thereby effectively solving the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a fault ride-through method for grid-type converters based on dynamic virtual resistance control, comprising the following steps:

[0007] Add a control loop based on virtual impedance to the control system of the grid-type converter;

[0008] The actual value of the grid voltage is detected to determine whether the grid voltage has dropped; the current amplitude output by the grid-connected converter is detected in real time to determine whether the current amplitude exceeds the set value; if either of the two conditions is met, the virtual impedance control circuit is activated.

[0009] The virtual resistance is controlled in stages, and the magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude.

[0010] When the grid voltage recovers and the current amplitude is less than the set value, the virtual resistor staged current limiting control exits.

[0011] Furthermore, the criterion for initiating the dynamic current limiting circuit of the inner loop virtual resistor is:

[0012] ;

[0013] In the formula, The current amplitude output by the grid-connected converter. This refers to the maximum allowable current amplitude for a grid-type converter. This is the actual value of the grid voltage.

[0014] Furthermore, the virtual resistance provided to the power system by the grid-type converter is adjusted in real time according to the fault current amplitude, including:

[0015] ;

[0016] In the formula, This is the virtual resistance gain coefficient. This is the calculated value for the virtual resistance.

[0017] Furthermore, the virtual resistance gain coefficient is dynamically adjusted according to changes in the current amplitude. The dynamic adjustment control strategy is as follows:

[0018] ;

[0019] In the formula, For gain The value, , Gain coefficients for different oscillation levels Numerical parameters, , , ... represent the current amplitude output by the grid-connected converter. Threshold parameters.

[0020] Further, the step of "when the grid voltage recovers and the current amplitude is less than the set value" includes:

[0021] When the current amplitude is less than the maximum current amplitude allowed to flow through the grid-type converter And the grid voltage recovered to more than 0.9 pu.

[0022] The present invention also includes a grid-type converter fault ride-through system based on dynamic virtual resistance control, using the method described above, wherein the system comprises:

[0023] Virtual impedance control unit, used to add a control loop based on virtual impedance to the control system of grid-type converter;

[0024] The judgment unit is used to detect the actual value of the grid voltage and determine whether the grid voltage has dropped; it also detects the current amplitude output by the grid-connected converter in real time and determines whether the current amplitude exceeds the set value; if either of these conditions is met, the virtual impedance control circuit is activated.

[0025] The limiting control unit is used to perform staged current limiting control on the virtual resistance. The magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude.

[0026] The fault ride-through unit is used to exit the virtual resistance staged current limiting control when the grid voltage recovers and the current amplitude is less than the set value.

[0027] The present invention also includes a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the method as described above.

[0028] The present invention also includes a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described above.

[0029] The beneficial effects of this invention are as follows: By adding a control loop based on virtual impedance to the grid-type converter control system, the grid-type converter can adjust the magnitude of its virtual resistance to the power system according to the change in the fault current amplitude. When the fault current rapidly enters the high range, the virtual resistance value increases, immediately improving the current limiting capability and avoiding response lag caused by dynamic delay under continuous control. Within a fixed range, the virtual resistance value remains unchanged, thus becoming insensitive to small fluctuations in current such as measurement noise and switching harmonics, reducing frequent adjustments to the virtual resistance, thereby avoiding oscillations generated during the control process, effectively suppressing the steady-state and transient components of the short-circuit current, achieving fault current limiting during fault ride-through of the grid-type converter, and thus improving the fault ride-through capability and transient stability performance of the grid-type converter. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of the method in Example 1;

[0032] Figure 2 This is a schematic diagram of the system structure in Example 1;

[0033] Figure 3 This is a topology diagram of the main circuit of the grid-type converter in Example 2;

[0034] Figure 4 This is a block diagram of the voltage and current inner loop control of the grid-type converter in Example 2;

[0035] Figure 5 This is the grid-connected equivalent circuit of the grid-type converter after introducing virtual impedance in Example 2;

[0036] Figure 6 This is a block diagram of the inner loop limiting control based on staged dynamic virtual resistance in Example 2;

[0037] Figure 7 This is a schematic diagram of the structure of the computer device of the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] Example 1:

[0040] like Figure 1 As shown: A fault ride-through method for a grid-type converter based on dynamic virtual resistance control includes the following steps:

[0041] Add a control loop based on virtual impedance to the control system of the grid-type converter;

[0042] The system detects the actual value of the grid voltage to determine if a voltage drop has occurred; it also monitors the output current amplitude of the grid-connected converter in real time to determine if the current amplitude exceeds the set value; if either condition is met, the virtual impedance control circuit is activated.

[0043] The virtual resistance is controlled in stages, and the magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude.

[0044] When the grid voltage recovers and the current amplitude is less than the set value, the virtual resistor staged current limiting control exits.

[0045] By incorporating a virtual impedance-based control loop into the grid-connected converter control system, the grid-connected converter can adjust the virtual resistance it provides to the power system based on changes in the fault current amplitude. When the fault current rapidly enters the high range, the virtual resistance value increases, immediately enhancing the current limiting capability and avoiding response lag caused by dynamic delays under continuous control. Within a fixed range, the virtual resistance value remains constant, thus becoming insensitive to small current fluctuations such as measurement noise and switching harmonics. This reduces frequent adjustments to the virtual resistance, thereby avoiding oscillations generated during the control process, effectively suppressing the steady-state and transient components of the short-circuit current, and achieving fault current limiting during fault ride-through of the grid-connected converter. Consequently, the fault ride-through capability and transient stability of the grid-connected converter are improved.

[0046] In this embodiment, the criterion for activating the dynamic current limiting circuit of the inner loop virtual resistor is:

[0047] ;

[0048] In the formula, The current amplitude output by the grid-connected converter. This refers to the maximum allowable current amplitude for a grid-type converter. This is the actual value of the grid voltage.

[0049] The virtual resistance provided to the power system by the grid-type converter is adjusted in real time according to the magnitude of the fault current, including:

[0050] ;

[0051] In the formula, This is the virtual resistance gain coefficient. This is the calculated value for the virtual resistance.

[0052] The virtual resistance gain coefficient is dynamically adjusted according to the change in current amplitude. The dynamic adjustment control strategy is as follows:

[0053] ;

[0054] In the formula, For gain The value, , Gain coefficients for different oscillation levels Numerical parameters, , , ... represent the current amplitude output by the grid-connected converter. Threshold parameters.

[0055] When the grid voltage recovers and the current amplitude is less than the set value, including:

[0056] When the current amplitude is less than And the grid voltage recovered to more than 0.9 pu.

[0057] like Figure 2 As shown, this embodiment also includes a grid-type converter fault ride-through system based on dynamic virtual resistance control. Using the method described above, the system includes:

[0058] Virtual impedance control unit, used to add a control loop based on virtual impedance to the control system of grid-type converter;

[0059] The judgment unit is used to detect the actual value of the grid voltage and determine whether the grid voltage has dropped; it also detects the current amplitude output by the grid-connected converter in real time and determines whether the current amplitude exceeds the set value; if either of these conditions is met, the inner loop virtual resistor dynamic current limiting circuit is activated.

[0060] The limiting control unit is used to initiate staged dynamic virtual resistance current limiting control. The magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude.

[0061] The fault ride-through unit is used to exit the virtual resistance current limiting control when the grid voltage recovers and the current amplitude is less than the set value.

[0062] Example 2:

[0063] The main circuit of a grid-type converter consists of a voltage source converter, a DC power supply, and a filter circuit. The main circuit topology is as follows: Figure 3 As shown. Voltage source converters, as the main component of grid-type converters, have various topologies. This patent selects a typical three-phase bridge voltage source converter topology for research. The DC-side power supply of a grid-type converter typically consists of DC power sources such as photovoltaic power generation systems, energy storage systems, wind power generation systems, or DC systems. Relying on the active power provided by the DC power supply, the grid-type converter can effectively simulate the primary frequency regulation characteristics of a synchronous generator. The grid-type converter is connected in parallel to the AC grid via a filter circuit, which uses an LC circuit to filter out high-frequency harmonics.

[0064] Figure 3 The grid-type converter is connected to the grid through the point of common coupling (PCC). For the DC-side capacitor of the grid-type converter; For filtering inductors in grid-type converters; The equivalent resistance of the filter inductor in a grid-type converter; For filtering capacitors in grid-type converters; The impedance of the power supply side line; This indicates the DC power supply voltage of the grid-type converter; This indicates the output voltage of the grid-connected converter. , , These represent the output voltages of the grid-type converter. The A, B, and C phase components; This indicates the terminal voltage of a grid-connected converter. , , These represent the terminal voltages of the grid-connected converter. The A, B, and C phase components; Indicates AC power supply voltage. , , These represent the AC power supply voltages respectively. The A, B, and C phase components; This indicates the output current of the grid-connected converter. , , These represent the output current of the grid-type converter. The A, B, and C phase components; This indicates the grid-side current of a grid-connected converter. , , These represent the grid-side currents of the grid-type converter. The A, B, and C phase components.

[0065] According to Kirchhoff's voltage law and current law, in the ABC three-phase stationary coordinate system, the voltage loop equation and current equation of the grid converter can be expressed as Equation (1) and Equation (2), respectively.

[0066] (1)

[0067] (2)

[0068] The terminal voltage of the grid converter As a reference phasor, the three-phase AC quantities are transformed into the dq synchronous rotating coordinate system through the Park transformation. The corresponding Park transformation matrix can be expressed as:

[0069] (3)

[0070] In the formula, Terminal voltage The phase angle.

[0071] After applying the Park transformation matrix shown in equation (3) to equations (1) and (2), the voltage loop equation and current equation of the grid-type converter in the dq coordinate system can be obtained as follows:

[0072] (4)

[0073] (5)

[0074] In the formula, and They are respectively d-axis components and q-axis components; and They are respectively d-axis components and q-axis components; and They are respectively d-axis components and q-axis components; and They are respectively The d-axis and q-axis components.

[0075] according to Figure 3 In the dq coordinate system, the output active power of the grid-type converter is... and reactive power It can be calculated using the following equation:

[0076] (6)

[0077] By designing reasonable voltage and current inner loops, the transient response characteristics of the converter can be optimized. The following is a mathematical model analysis of the voltage and current inner loop control of the grid-type converter.

[0078] because The effect on the overall dynamic characteristics of the converter is relatively weak, and therefore can be ignored under certain accuracy requirements. By performing a Laplace transform on equation (4), the frequency domain value can be derived. , , and The transfer function relationship between them is as follows:

[0079] (7)

[0080] Performing a Laplace transform on equation (5) yields the frequency domain value. , , and The transfer function expression between them is:

[0081] (8)

[0082] From equation (8), we can see that and Dynamic coupling exists. To eliminate this coupling effect, a feedforward decoupling control method is adopted, letting:

[0083] (9)

[0084] In the formula, , These are the command values ​​for the d-axis and q-axis components of the terminal voltage, respectively. and These represent the transfer functions of the d-axis and q-axis controllers, respectively.

[0085] By combining equations (8) and (9), the d-axis component of the terminal voltage can be obtained. and q-axis components The expression for the decoupling transfer function is:

[0086] (10)

[0087] when and When using a PI controller, equation (10) can be specifically expressed as:

[0088] (11)

[0089] In the formula, and These are the proportional and integral coefficients of the d-axis PI controller, respectively. and These are the proportional and integral coefficients of the q-axis PI controller, respectively.

[0090] Equation (11) adopts a second-order closed-loop transfer function structure, and the dynamic characteristics of the grid-type converter can be adjusted by changing the PI parameters. Therefore, the voltage inner-loop control strategy for the grid-type converter is designed as follows:

[0091] (12)

[0092] The d-axis component of the output current of the grid-type converter obtained in equation (11) and q-axis components The command value is used as the input of the inner current loop. Analysis of equation (7) shows that... and There is a coupling relationship; therefore, a feedforward decoupling control method is adopted, let:

[0093] (13)

[0094] In the formula, and These are the command values ​​for the d-axis and q-axis components of the output current, respectively. and These represent the transfer functions of the d-axis and q-axis controllers, respectively.

[0095] Combining equations (7) and (13), we get... and The transfer function relationship is expressed as:

[0096] (14)

[0097] If in equation (14) and Using a PI controller, it can be further expressed as:

[0098] (15)

[0099] In the formula, and These are the proportional and integral coefficients of the d-axis PI controller, respectively. and These are the proportional and integral coefficients of the q-axis PI controller, respectively.

[0100] In formula (15) and The transfer functions are all in second-order closed-loop form. Similarly, the inner-loop current control strategy for the grid-type converter is obtained as follows:

[0101] (16)

[0102] Combining equations (12) and (16), the voltage and current inner loop control block diagram of the grid converter is obtained as follows: Figure 4 As shown.

[0103] When a grid voltage dip occurs, the terminal voltage of the grid-connected converter also decreases, reducing its electromagnetic power output and causing a reduction in the deceleration area. If the deceleration area is insufficient to balance the previous acceleration area, the power angle of the grid-connected converter may continue to increase, potentially leading to transient instability. After a grid voltage dip, the converter will simultaneously face the dual risks of steady-state overcurrent and transient inrush current. Increased voltage dip depth and decreased grid impedance both exacerbate the severity of the current inrush effect. To reduce the fault inrush current generated by the grid-connected converter after a grid fault, the time constant can be shortened. This causes the transient component to decay to a smaller value before the steady-state component reaches its peak. The time constant... This is related to the equivalent impedance between the grid-connected converter and the power grid. Therefore, by adding a control element based on virtual impedance to the grid-connected converter control system, the equivalent impedance level of the system under fault conditions can be improved, thereby effectively suppressing overcurrent problems.

[0104] The grid-connected equivalent circuit of the grid-connected converter after introducing virtual impedance is as follows: Figure 5 As shown in the figure, For virtual impedance, For virtual resistance, This is a virtual reactance.

[0105] Introducing virtual impedance After the fault, the steady-state output current of the grid-type converter... The expression is:

[0106] (17)

[0107] Steady-state output current after fault amplitude The expression is:

[0108] (18)

[0109] Thus, the virtual impedance is obtained. Caused voltage drop for:

[0110] (19)

[0111] Assume the steady-state output current of the grid-type converter after a fault. The d-axis and q-axis components in the dq synchronous rotating coordinate system are respectively and Voltage drop caused by virtual impedance The d-axis and q-axis components in the dq synchronous rotating coordinate system are respectively and Therefore, the virtual impedance in the dq synchronous rotating coordinate system The voltage drop across is:

[0112] (20)

[0113] A virtual impedance element is embedded in the control of a grid-type converter to simulate the stator impedance characteristics of a synchronous generator. Its d-axis component... and q-axis components Subtract the virtual impedance respectively After the voltage drop, the modulated wave voltage of the grid converter considering virtual impedance in the dq synchronous rotating coordinate system can be obtained. and The expression is:

[0114] (twenty one)

[0115] In the formula, the virtual inductance is represented as .

[0116] From equation (17), the relationship between grid voltage, grid-type converter terminal voltage, and fault current in the dq synchronous rotating coordinate system can be obtained as follows:

[0117] (twenty two)

[0118] Thus, the virtual resistance is obtained. and virtual reactance The calculation expression and They are respectively:

[0119] (twenty three)

[0120] (twenty four)

[0121] After introducing virtual impedance, the equivalent virtual impedance between the converter and the grid is... Represented as:

[0122] (25)

[0123] In the formula, This is the equivalent resistance between the converter and the grid after introducing virtual impedance; This is to introduce virtual impedance to achieve the equivalent reactance between the converter and the power grid.

[0124] Attenuation component time constant The effect of virtual impedance becomes:

[0125] (26)

[0126] In the formula, .

[0127] The above analysis shows that the larger the virtual impedance applied after a fault, the greater the fault current. The smaller the virtual impedance, the better. This means the virtual impedance can limit the steady-state component of the current after a fault, but the transient component of the fault current may still exceed the current limit. Under the influence of the virtual impedance, the transient impact current and the time constant of the decay component... Related, by and The effect of the ratio is that, since the inherent impedance of the line remains constant, if it is necessary to accelerate the attenuation of the transient current component, the virtual resistance needs to be increased. Or reduce virtual reactance Increasing the equivalent reactance of the line will reduce the dynamic response performance of the converter, which is detrimental to the transient stability of the converter. Therefore, to prevent the steady-state and transient components of the current from exceeding the current limit value during a fault, a current-limiting control method that increases the virtual resistance can be adopted. After a short-circuit fault occurs, the virtual reactance remains unchanged. By increasing the virtual resistance, the virtual impedance magnitude of the grid-type converter increases, thereby limiting the steady-state component of the short-circuit current. The increase in virtual resistance can also accelerate the decay rate of the transient inrush current, thus achieving dual limiting of the steady-state and transient components of the current after the fault.

[0128] While increasing the virtual resistance can reduce overcurrent during grid faults, existing current-limiting methods using virtual resistance typically employ a fixed value. When power system parameters or structures are disturbed, the equivalent impedance between the converter and the grid changes in real time, and a fixed virtual resistance value cannot achieve accurate current limiting during converter fault ride-through. Therefore, this paper proposes a current-limiting method based on a staged dynamic virtual resistance, with the control flow as follows:

[0129] (1) Fault detection. First, detect the difference between the actual value and the rated value of the grid voltage to determine whether the grid voltage has dropped. According to the fault ride-through technical requirements of grid-connected converters, when the actual value of the grid voltage is detected... When the voltage drops between 0.2 and 0.9 pu, the converter should enter fault ride-through mode. The output current amplitude of the grid-connected converter should be monitored in real time, and the maximum allowable current amplitude for the grid-connected converter should be set. (Generally taken as 1.1~1.5 pu), when the actual value of the output current of the grid-connected converter exceeds... Then the converter should enter fault ride-through mode. Therefore, the condition for activating the inner loop virtual resistor dynamic current limiting circuit is:

[0130] (27)

[0131] (2) Dynamic current limiting of the inner loop virtual resistance. After the grid-type converter enters the fault ride-through state, the staged dynamic virtual resistance current limiting control is quickly activated. The magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude. The dynamic mathematical model of the virtual resistance is as follows:

[0132] (28)

[0133] In the formula, This is the virtual resistance gain coefficient. This is the calculated value for the virtual resistance.

[0134] Since the virtual resistance provided by a grid-type converter to the power system depends on its gain... Increase the gain of the control system This will increase the virtual resistance, but excessive gain... This will also prolong the time for the grid-type converter to reach stability. In order to balance fault current limiting and converter dynamic response speed, the gain of the virtual resistance dynamic current limiting strategy of the grid-type converter can be adjusted according to the change in current amplitude. Adaptive adjustment, The dynamic adjustment control strategy is as follows:

[0135] (29)

[0136] In the formula, For gain The value, , Gain under different oscillation levels Numerical parameters, , , ,……for Threshold parameters.

[0137] Equations (28) and (29) constitute the proposed inner-loop limiting strategy based on staged dynamic virtual resistance. Through this control strategy, the grid-connected converter can adjust the virtual resistance it provides to the power system according to changes in the fault current amplitude. When the fault current rapidly enters the high range, the virtual resistance value increases dramatically, immediately enhancing the current limiting capability and avoiding response lag caused by dynamic delay under continuous control. Within a fixed range, the virtual resistance value remains constant, thus becoming insensitive to small fluctuations in current such as measurement noise and switching harmonics, reducing frequent adjustments to the virtual resistance, and thereby avoiding oscillations generated during the control process.

[0138] (3) Virtual resistor exits operation. When the short-circuit current is less than Furthermore, the virtual resistor is deactivated when the grid voltage recovers to above 0.9 pu. Thus, the inner-loop limiting control strategy based on the staged dynamic virtual resistor effectively suppresses the steady-state and transient components of the short-circuit current, achieving fault current limiting during fault ride-through of the grid-connected converter, thereby improving the fault ride-through capability and transient stability of the grid-connected converter.

[0139] Based on the above analysis, the inner-loop limiting control block diagram based on staged dynamic virtual resistance is as follows: Figure 6 As shown.

[0140] This embodiment studies the typical three-phase bridge voltage source converter topology, presents a mathematical model of the grid-type converter, and proposes a model for the inner-loop voltage and current control of the grid-type converter based on this mathematical model. Through a hierarchical adjustment mechanism, a PI controller is used to ensure the stability of the output voltage and current. At the same time, a decoupling link is introduced to reduce the coupling relationship between voltage and current to improve the dynamic response performance of the system. In the fault ride-through method of the grid-type converter, an inner-loop limiting control based on a staged dynamic virtual resistor is designed in the outer loop. The existence of a stable operating point after a fault occurs is judged, and dynamic current limiting of the inner-loop virtual resistor is implemented. When the fault is cleared, the fault ride-through mode can be exited in time.

[0141] Please see Figure 7 The diagram shows a structural schematic of a computer device provided in an embodiment of this application. An embodiment of this application provides a computer device 400, including a processor 410 and a memory 420. The memory 420 stores a computer program executable by the processor 410. When the computer program is executed by the processor 410, it performs the method described above.

[0142] This application embodiment also provides a storage medium 430, on which a computer program is stored, and the computer program is executed by a processor 410 to perform the above method.

[0143] The storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0144] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0145] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0146] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0147] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0148] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0149] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0150] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0151] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A fault ride-through method for a grid-type converter based on dynamic virtual resistance control, characterized in that, Includes the following steps: Add a virtual impedance-based control element to the control system of the grid-type converter; The system detects the actual value of the grid voltage to determine if a voltage drop has occurred; it also monitors the current amplitude output by the grid-connected converter in real time to determine if the current amplitude exceeds a set value; if either condition is met, the virtual impedance control circuit is activated. The virtual resistance is controlled in stages, and the magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude. When the grid voltage recovers and the current amplitude is less than the set value, the virtual resistor phased current limiting control exits. The criterion for activating the virtual impedance control circuit is: ； In the formula, The current amplitude output by the grid-connected converter. This refers to the maximum allowable current amplitude for a grid-type converter. This is the actual value of the grid voltage; The virtual resistance provided to the power system by the grid-type converter is adjusted in real time according to the fault current amplitude, including: ； In the formula, This is the virtual resistance gain coefficient. Calculated value for virtual resistance; The virtual resistance gain coefficient is dynamically adjusted according to changes in the current amplitude. The dynamic adjustment control strategy is as follows: ； In the formula, For gain The value, , Gain coefficients for different oscillation levels Numerical parameters, , , ... represent the current amplitude output by the grid-connected converter. Threshold parameters.

2. The fault ride-through method for grid-type converters based on dynamic virtual resistance control according to claim 1, characterized in that, When the grid voltage recovers and the current amplitude is less than the set value, the following applies: When the current amplitude is less than the maximum current amplitude allowed to flow through the grid-type converter And the grid voltage recovered to more than 0.9 pu.

3. A grid-type converter fault ride-through system based on dynamic virtual resistance control, characterized in that, Using the method of claim 1 or 2, the system comprises: Virtual impedance control unit, used to add a control loop based on virtual impedance to the control system of grid-type converter; The judgment unit is used to detect the actual value of the grid voltage and determine whether the grid voltage has dropped; it also detects the current amplitude output by the grid-connected converter in real time and determines whether the current amplitude exceeds the set value; if either of these conditions is met, the virtual impedance control circuit is activated. The limiting control unit is used to perform staged current limiting control on the virtual resistance. The magnitude of the virtual resistance provided by the grid-type converter to the power system is adjusted in real time according to the fault current amplitude. The fault ride-through unit is used to exit the virtual resistance staged current limiting control when the grid voltage recovers and the current amplitude is less than the set value.

4. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in claim 1 or 2.

5. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method as described in claim 1 or 2.

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