Network construction type converter, fault ride-through control method and system thereof, terminal and medium

Abstract

The invention provides a fault ride-through control method and a fault ride-through control system for a grid-forming converter, which are characterized in that the current of the grid-forming converter under an asymmetric fault is controlled by adopting a negative-sequence current reference generation strategy aiming at an inner ring of a controller, and negative-sequence reactive current is injected into a power grid; adopting a partial sequence current amplitude limiting strategy to control the maximum phase current amplitude of the injected asymmetric current not to exceed an amplitude limiting value; controlling the boundary of an active reference value by adopting an active reference value amplitude limiting strategy for an active synchronization ring; a synchronous damping link is adopted to enhance damping in power angle swing; for a reactive voltage loop, a reactive voltage variable coefficient control strategy is adopted to control the output of the maximum reactive current; and an internal potential locking strategy is adopted to suppress overvoltage. According to the invention, negative-sequence reactive power is provided, and overcurrent of each phase is avoided; the power angle characteristic is improved, and the transient stability is improved; stable transient voltage support is provided in a current output capability range; and after the fault is recovered, the voltage of the converter grid-connected point is smoothly recovered.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy access and grid-connected control technology, in particular, to a grid-forming converter and a fault ride-through control method, system, terminal and medium thereof. BACKGROUND

[0002] In recent years, new energy mainly including wind and light and electrochemical energy storage have experienced rapid development in China. However, the voltage and frequency characteristics of the power generated by wind power, photovoltaic and energy storage are not matched with the power grid, and thus cannot be directly connected with the power grid. Therefore, the voltage and frequency must be converted by grid-connected converters based on power electronics, so as to realize grid connection. At present, the number of new energy grid-connected is increasing, and the characteristics of grid-connected converters begin to gradually affect the characteristics of the power grid. Since the characteristics of grid-connected converters are mainly dominated by the control loop, the controller of grid-connected converters plays an increasingly important role in the high penetration area of new energy. In this regard, due to the good grid-friendly characteristics, the "grid-forming control" of grid-connected converters has attracted a lot of attention in recent years. This control method can enable new energy power sources with grid-connected converters to have functions such as frequency response and voltage support, and gradually gets popularized.

[0003] However, since the grid-connected converter adopting grid-forming control (referred to as "grid-forming converter") is a "voltage source" to the power grid, it is easy to cause overcurrent during short-circuit fault of the power grid, thereby causing harm to the fragile power electronic devices inside. Therefore, how to design an effective fault ride-through strategy has become a research hotspot in the field of grid-forming control.

[0004] In addition, since the grid-forming control is similar to the traditional synchronous generator in terms of power angle characteristics, it is easy to produce a large power angle acceleration during the short-circuit of the power grid, thereby increasing the risk of transient instability. Once transient instability occurs, not only the ride-through and support characteristics during the fault are affected, but also serious consequences such as power source out-of-step, power reverse flow, voltage swing and the like are easy to occur after the recovery of the power grid from fault, which endangers the safety of the power system. Therefore, transient stability is also a problem that needs to be concerned in the fault control of grid-forming converters.

[0005] In addition, under the premise that the above overcurrent problem and transient instability problem can be avoided, how to fully exert the transient voltage support potential of grid-forming control is also a problem that is concerned at present.

[0006] Through retrieval, it is found that most of the current technologies basically consider the steady-state operation and transient overcurrent problem of grid-forming control, but the characteristics during the transient period are not perfect, including:

[0007] Currently, only a few technologies focus on the operation of grid-forming converters under asymmetric faults; and considering the requirements of grid-connection guidelines and the limited current output capability of grid-connected converters, these disclosed technologies do not design corresponding technical solutions for the adaptability of grid-connection guidelines to negative sequence currents and the allocation of positive and negative sequence current capacity;

[0008] Currently, only a few technologies focus on the transient stability of grid-forming converters, and the solutions thereof are directly set according to the grid point voltage during the fault, without considering the power output capability of the power supply in front of the grid-connected converter;

[0009] Currently, only a few technologies focus on the transient voltage support function of grid-forming converters, which is very important for the transient safety of the power grid; in the existing technical solutions containing this function, the fault point information is obtained through detection to provide corresponding support capability, and due to the difficulty in accurate transient detection, this technical route undoubtedly increases the insecurity and risk of incorrect operation of control.

[0010] Currently, no similar technology to the present application has been found to be described or reported, and no similar domestic or foreign materials have been collected. SUMMARY

[0011] The present application provides a grid-forming converter and a fault ride-through control method, system, terminal and medium thereof to solve the above problems in the prior art.

[0012] According to one aspect of the present application, a grid-forming converter fault ride-through control method is provided, comprising:

[0013] For the inner loop of the controller, a negative sequence current reference generation strategy and a bias sequence current limiting strategy are provided respectively; wherein the negative sequence current reference generation strategy takes the negative sequence dq-axis voltage as the input and outputs the negative sequence dq-axis current pre-command to obtain the negative sequence dq-axis current command value, which is used to control the current of the grid-forming converter under asymmetric faults and inject negative sequence reactive current into the power grid; the bias sequence current limiting strategy takes the positive and negative sequence dq-axis current command values as the input and outputs the positive and negative sequence current reference values, which are used to control the maximum phase current amplitude of the injected asymmetric current to be less than the limiting value;

[0014] For the active synchronous loop, an active reference value limiting strategy and a synchronous damping link are provided respectively; wherein the active reference value limiting strategy takes the positive and negative sequence dq-axis voltage and current at the grid point and the active set value as the input and outputs the active reference value, which is used to control the upper and lower boundaries of the active reference value; the synchronous damping link takes the grid-forming converter frequency generated by the active synchronous loop and the detected grid point frequency as the input and outputs the damping power of the active synchronous loop, which is used to control the damping in the power angle swing;

[0015] For the reactive voltage loop, a reactive voltage variable coefficient control strategy and an internal potential locking strategy are provided respectively; wherein the reactive voltage variable coefficient control strategy takes the voltage amplitude as input and outputs the reactive voltage droop coefficient for controlling the maximum reactive current output; the internal potential locking strategy takes the voltage amplitude and the current instruction value as input and outputs the locking signal of the internal potential integrator for suppressing overvoltage.

[0016] Preferably, the negative sequence current reference generation strategy comprises:

[0017] Output negative sequence dq-axis current pre-instruction The expression is:

[0018]

[0019] Wherein, I sd,pre , I sq,pre are dq-axis current pre-instructions, K - is the negative sequence reactive current injection coefficient, T f1 is the voltage filter time constant, and s is the Laplace operator, Vd, Vq are dq-axis voltages, and · represents multiplication;

[0020] According to the negative sequence dq-axis current pre-instruction output by the negative sequence current reference generation strategy, the negative sequence dq-axis current instruction value I The expression is:

[0021]

[0022] Wherein, λ represents the negative sequence current limiting amplitude ratio, and I lim represents the current limiting amplitude.

[0023] Preferably, the negative sequence current limiting strategy comprises:

[0024] According to the negative sequence dq-axis current instruction value I and the positive sequence dq-axis current instruction value I The maximum phase voltage amplitude I cmd,max is calculated, and the expression is:

[0025]

[0026] Wherein, represents the positive / negative sequence current instruction value amplitude; and represent the positive sequence and negative sequence d-axis current instruction values and the positive sequence and negative sequence q-axis current instruction values, respectively; I cmd,Δ represents the maximum phase current instruction additional modulus, and the expression is:

[0027]

[0028] wherein γ ∈ [0, -4π / 3, 4π / 3] represents the phase of the three-phase current; represents the positive / negative sequence current command phase angle;

[0029] calculating the positive sequence current reference value obtained:

[0030]

[0031] calculating the negative sequence current reference value obtained:

[0032]

[0033] wherein I lim represents the current limiting value.

[0034] Preferably, the active set value P ref,0 obtaining the active reference value P ref through the active reference value limiting strategy.

[0035] Preferably, the active reference value limiting strategy comprises:

[0036] the active reference value P ref , the expression of which is:

[0037]

[0038] wherein P ref,0 represents the active set value, P lim+ and P lim- respectively represent the upper and lower limits of active transmission, the expressions of which are:

[0039] P lim+ = min{1, αP max}, P lim - = max{-1, αP min}

[0040] wherein α is the active limiting margin coefficient; P max and P min are respectively the upper and lower limits of active transmission, which are calculated by the following way:

[0041] calculating the positive sequence available current capacity

[0042]

[0043] wherein I lim represents the current limiting value; represents the negative sequence current amplitude; I s,Δdenotes the maximum phase current additional modulus, which is calculated by the following formula:

[0044]

[0045] wherein γ denotes the phase of the three-phase current; and denote the positive and negative sequence d-axis currents, respectively; and denote the positive and negative sequence q-axis currents, respectively;

[0046] The direct current components of the negative sequence active power and the positive sequence reactive power are calculated according to the following formula:

[0047]

[0048] wherein, and denote the positive and negative sequence q-axis voltages, respectively;

[0049] The positive sequence maximum active power that can be generated is obtained by the following formula:

[0050]

[0051] wherein, denotes the positive sequence voltage amplitude;

[0052] The upper and lower active power amplitude values P max and P min are obtained by the following formula:

[0053]

[0054] Preferably, the input-output relationship of the synchronous damping link is:

[0055] P d = D d ·(ω-ω g )

[0056] wherein P d denotes the damping power; ω denotes the frequency of the grid-forming converter; ω g denotes the detected grid point frequency; D d denotes the transient droop coefficient.

[0057] Preferably, the reactive voltage variable coefficient control strategy comprises:

[0058] When the voltage amplitude U s is in the range of 0.9-1.1, it is considered that the voltage is in the normal interval, at this time the reactive voltage droop coefficient adopts the size in the normal case, denoted as K q0and K u0 wherein K q represents; K u represents;

[0059] When the voltage amplitude U s is too large, i.e. U s <0.85 or U s >1.15, the reactive voltage droop coefficients are set as K q1 and K u1 , respectively.

[0060] When 0.85≤U s <0.90 or 1.10<U s ≤1.15, a linear transition is set, and K q and K u are expressed as a function of U s , and the expression is:

[0061]

[0062] wherein K q1 and K u1 satisfy the following relationship:

[0063] K q1 :K u1 =0~0.1.

[0064] Preferably, the inner potential locking strategy comprises:

[0065] When the current command value I cmd,max is greater than the current limit value I lim and the positive sequence voltage is less than 0.9pu, at this time the current is saturated, the reactive-voltage outer loop does not work, and the inner potential locking strategy outputs a locking signal Frz for locking the inner potential integrator, so that the integrator stops integration;

[0066] When the current exits saturation or the voltage recovers, the locking signal Frz is released, and a hysteresis comparator is used to determine the current desaturation; wherein:

[0067] When I cmd,max <I lim -Δ dz , it is determined that the current exits saturation; wherein Δ dz represents the dead zone of the hysteresis comparator.

[0068] According to another aspect of the present application, a network configuration type converter fault ride-through control system is provided, comprising:

[0069] The controller comprises an inner loop control module, which comprises a negative sequence current reference generation module and a deviation sequence current limiting module; wherein the negative sequence current reference generation module takes negative sequence dq-axis voltage as input and outputs negative sequence dq-axis current pre-command, thereby obtaining negative sequence dq-axis current command value, which is used to control the current of the grid-connected converter under asymmetric fault and inject negative sequence reactive current into the power grid; the deviation sequence current limiting module takes positive sequence and negative sequence dq-axis current command value as input and outputs positive sequence and negative sequence current reference value, which is used to control the maximum phase current amplitude of the injected asymmetric current to be less than the limiting value;

[0070] The controller comprises an inner loop control module, which comprises a negative sequence current reference generation module and a deviation sequence current limiting module; wherein the negative sequence current reference generation module takes negative sequence dq-axis voltage as input and outputs negative sequence dq-axis current pre-command, thereby obtaining negative sequence dq-axis current command value, which is used to control the current of the grid-connected converter under asymmetric fault and inject negative sequence reactive current into the power grid; the deviation sequence current limiting module takes positive sequence and negative sequence dq-axis current command value as input and outputs positive sequence and negative sequence current reference value, which is used to control the maximum phase current amplitude of the injected asymmetric current to be less than the limiting value;

[0071] The controller comprises an inner loop control module, which comprises a negative sequence current reference generation module and a deviation sequence current limiting module; wherein the negative sequence current reference generation module takes negative sequence dq-axis voltage as input and outputs negative sequence dq-axis current pre-command, thereby obtaining negative sequence dq-axis current command value, which is used to control the current of the grid-connected converter under asymmetric fault and inject negative sequence reactive current into the power grid; the deviation sequence current limiting module takes positive sequence and negative sequence dq-axis current command value as input and outputs positive sequence and negative sequence current reference value, which is used to control the maximum phase current amplitude of the injected asymmetric current to be less than the limiting value;

[0072] According to a third aspect of the present application, a grid-connected converter is provided, which adopts the fault ride-through control method according to any one of the above-mentioned aspects of the present application or the fault ride-through control system according to the above-mentioned aspects of the present application, to control fault ride-through.

[0073] According to a fourth aspect of the present application, a power supply system is provided, the grid-connected converter of which adopts the fault ride-through control method according to any one of the above-mentioned aspects of the present application or the fault ride-through control system according to the above-mentioned aspects of the present application, to control fault ride-through.

[0074] According to a fifth aspect of the present application, a computer terminal is provided, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, the computer program can be used to execute the method according to any one of the above-mentioned aspects of the present application or run the system according to the above-mentioned aspects of the present application.

[0075] According to a sixth aspect of the present application, a computer readable storage medium is provided, having stored thereon a computer program which, when executed by a processor, is adapted to perform the method of any one of the preceding aspects of the present application, or to operate the system of the preceding aspects of the present application.

[0076] Thanks to the technical solutions described above, the present application has at least one of the following beneficial effects compared with the prior art:

[0077] The grid-connected converter and the fault ride-through control method, system, terminal and medium provided by the present application can realize injection of the required negative sequence reactive current during asymmetric fault of the power grid according to the current grid-connected guide for new energy, while avoiding that the current of each phase exceeds the maximum value that the converter can tolerate, by adopting the negative sequence current reference generation module and the off-sequence current limiting strategy.

[0078] The grid-connected converter and the fault ride-through control method, system, terminal and medium provided by the present application can avoid continuous power angle acceleration of the grid-connected converter during the fault due to lack of static operating point of the active loop, thereby further causing transient power angle instability after the fault is cleared, while also being capable of increasing the damping of power angle swing, so as to stabilize the power angle swing in a relatively short time, and further improve the power angle stability, by adopting the active reference value limiting strategy and the synchronous damping link.

[0079] The grid-connected converter and the fault ride-through control method, system, terminal and medium provided by the present application can enable the grid-connected converter to emit the maximum short-circuit current within the current limiting range of the grid-connected converter during the fault to support the voltage amplitude during the transient state, while avoiding continuous accumulation of the internal potential due to temporary failure of the reactive voltage control during the fault, so as to ensure smooth transition of the voltage after the fault is recovered, without overvoltage problem. BRIEF DESCRIPTION OF DRAWINGS

[0080] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, with reference to the following drawings:

[0081] Figure 1 A typical grid-connected control block diagram in the prior art.

[0082] Figure 2 A schematic diagram of the improved control measures of the grid-connected converter fault ride-through control method in a preferred embodiment of the present application; wherein the deepening module represents the modification and / or supplement made on the basis of the scheme shown in FIG. 6. Figure 1

[0083] Figure 3 A power generation unit topology schematic diagram with a grid-connected converter as an interface in a preferred embodiment of the present application.​

[0084] Figure 4 Simulation waveform diagram of a preferred embodiment of the present application under unsymmetrical fault, dark area represents fault period; where (a) is three-phase current, (b) is three-phase voltage, (c) is positive and negative sequence voltage amplitude, (d) is active power, (e) is internal frequency.

[0085] Figure 5 Simulation waveform diagram of a preferred embodiment of the present application under unsymmetrical fault, dark area represents fault period; where (a) is positive and negative sequence voltage amplitude, (b) is active power, (c) is internal frequency.

[0086] Figure 6 Effect diagram of negative sequence current reference generation module of a preferred embodiment of the present application.

[0087] Figure 7 Effect diagram of ring current limiter of a preferred embodiment of the present application; where (a) is using ring current limiter, (b) is not using ring current limiter.

[0088] Figure 8 Effect diagram of active reference limiter of a preferred embodiment of the present application; where Us represents voltage amplitude, Ps represents active power.

[0089] Figure 9 Effect diagram of transient droop control of a preferred embodiment of the present application.

[0090] Figure 10 Effect diagram of reactive voltage variable coefficient control of a preferred embodiment of the present application.

[0091] Figure 11 Effect diagram of internal potential lockout of a preferred embodiment of the present application; where Us represents voltage amplitude, Qs represents reactive power, E represents internal potential. DETAILED DESCRIPTION

[0092] The embodiments of the present application are described in detail as follows: the embodiments are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

[0093] An embodiment of the present application provides a grid-connected converter fault ride-through control method, which aims at the deficiencies in the prior art, meets the requirements of the existing power grid, provides negative sequence reactive power, avoids overcurrent in each phase, improves power angle characteristics, improves the transient stability of the system after the fault, and makes the swing quickly stabilize; within the current output capability range, it provides smooth transient voltage support and autonomous reactive response; after the fault is recovered, the voltage at the grid-connected point of the converter should be smoothly recovered, and overvoltage is not prone to occur.

[0094] Specifically, as shown in the figure, Figure 2 the grid-connected converter fault ride-through control method provided by the embodiment can include:

[0095] For the inner loop of the controller, a negative sequence current reference generation strategy and a bias sequence current limiting strategy are provided; wherein the negative sequence current reference generation strategy takes the negative sequence dq-axis voltage as input and outputs the negative sequence dq-axis current pre-command, to obtain the negative sequence dq current instruction value, which is used to control the current of the grid-connected converter under asymmetric fault and inject negative sequence reactive current into the power grid; the bias sequence current limiting strategy takes the positive sequence and negative sequence dq-axis current instruction value as input and outputs the positive sequence and negative sequence current reference value, which is used to control the maximum phase current amplitude of the injected asymmetric current to not exceed the limiting value;

[0096] For the active synchronous loop, an active reference value limiting strategy and a synchronous damping link are provided; wherein the active reference value limiting strategy takes the positive and negative sequence dq-axis voltage and current at the grid-connected point and the active set value as input and outputs the active reference value, which is used to control the upper and lower boundaries of the active reference value; the synchronous damping link takes the grid-connected converter frequency generated by the active synchronous loop and the detected grid-connected point frequency as input and outputs the damping power of the active synchronous loop, which is used to control the damping in the power angle swing;

[0097] For the reactive voltage loop, a reactive voltage variable coefficient control strategy and an internal potential locking strategy are provided; wherein the reactive voltage variable coefficient control strategy takes the voltage amplitude as input and outputs the reactive voltage droop coefficient, which is used to control the maximum output reactive current; the internal potential locking strategy takes the voltage amplitude and current instruction value as input and outputs the locking signal of the internal potential integrator, which is used to suppress overvoltage.

[0098] In some preferred embodiments, the negative sequence current reference generation strategy can further include the following operations:

[0099] outputting the negative sequence dq-axis current pre-command The expression is:

[0100]

[0101] wherein, I sd,pre , Isq,pre These are the dq-axis current pre-commands, K - T is the negative sequence reactive current injection coefficient. f1 Here, s is the voltage filtering time constant (typically 2ms), and s is the Laplace operator. These are the voltages along the d and q axes, respectively, and · indicates multiplication.

[0102] Based on the negative sequence dq axis current pre-command output by the negative sequence current reference generation strategy, the negative sequence dq current command value is obtained. Its expression is:

[0103]

[0104] Where λ represents the negative sequence current limiting ratio, I lim This indicates the current limit value.

[0105] In some preferred embodiments, the negative sequence reactive current may further include:

[0106] According to the national standard GB / T 19963.1-2021 Technical Specifications for Wind Farm Connection to Power Systems Part 1: Onshore Wind Power, the expression for negative sequence reactive current is:

[0107]

[0108] Among them, U - For the negative sequence voltage amplitude, K - The negative sequence reactive current injection coefficient. This is a negative sequence reactive current command.

[0109] In some preferred embodiments, the off-sequence current limiting strategy may further include the following operations:

[0110] Based on the negative sequence dq axis current command value and positive sequence dq axis current command values Calculate the maximum phase voltage amplitude I cmd,max Its expression is:

[0111]

[0112] in, Indicates the magnitude of the positive / negative sequence current command value; and These represent the positive and negative sequence d-axis current command values ​​and the positive and negative sequence q-axis current command values, respectively; I cmd,Δ The maximum phase current command additional modulus is expressed as follows:

[0113]

[0114] wherein, γ∈[0, -4π / 3, 4π / 3] represents the phase of the three-phase current; represents the positive / negative sequence current command value phase angle;

[0115] Calculating the positive sequence current reference value Obtained:

[0116]

[0117] Calculating the negative sequence current reference value Obtained:

[0118]

[0119] wherein, I lim represents the current limiting value.

[0120] In the above preferred embodiment, the positive sequence dq-axis current command value can be generated by the positive sequence virtual admittance control, and the control process is similar to the negative sequence, which is not described here.

[0121] In some preferred embodiments, the active set value P ref,0 The active reference value P ref is obtained through the active reference value limiting strategy.

[0122] In some preferred embodiments, the active reference value limiting strategy can further include the following operations:

[0123] The active reference value P ref , whose expression is:

[0124]

[0125] wherein, P ref,0 represents the active set value, P lim+ and P lim- respectively represent the upper and lower limits of active transmission, whose expressions are:

[0126] P lim+ = min{1, αP max}, P lim - = max{-1, αP min}

[0127] wherein, α is the active limiting margin coefficient, preferably in the range of 0.95-0.98; P max and P min are respectively the upper and lower limits of active transmission, which are calculated by the following method:

[0128] Calculating the positive sequence available current capacity

[0129]

[0130] where I lim represents the current limit value; represents the negative sequence current amplitude; I s,Δ represents the maximum phase current additional modulus, which is calculated by the following formula:

[0131]

[0132] where γ represents the phase of the three-phase current; and respectively represent the positive sequence and negative sequence d-axis currents; and respectively represent the positive sequence and negative sequence q-axis currents;

[0133] The direct current components of the negative sequence active power and the positive sequence reactive power are calculated according to the following formula:

[0134]

[0135] where, and respectively represent the positive sequence and negative sequence q-axis voltages;

[0136] The positive sequence maximum active power that can be generated is obtained by the following formula:

[0137]

[0138] where, represents the positive sequence voltage amplitude;

[0139] The active power upper and lower limit amplitudes P max and P min are:

[0140]

[0141] In some preferred embodiments, the synchronous damping link can further include the following operations:

[0142] The input-output relationship of the synchronous damping link is:

[0143] P d = D d · (ω-ω g )

[0144] where P d represents the damping power; ω represents the frequency of the grid-connected converter; ω g represents the detected grid point frequency; D d represents the transient droop coefficient.

[0145] In some preferred embodiments, D d = 20~40.

[0146] In some preferred embodiments, the reactive voltage variable coefficient control strategy can further include the following operations:

[0147] When the voltage amplitude U s In the range of 0.9~1.1, the voltage is considered to be in the normal range, and the reactive voltage droop coefficient in this case is the size in normal condition, denoted as K q0 and K u0 , wherein K q represents; K u represents;

[0148] When the voltage amplitude U s is large, i.e. U s <0.85 or U s >1.15, the reactive voltage droop coefficient is set as K q1 and K u1 , respectively.

[0149] When 0.85≤U s <0.90 or 1.10<U s ≤1.15, a linear transition is set, and K q and K u are expressed as a function of U s , and the expression is:

[0150]

[0151] wherein K q0 and K u0 are generally designed according to the reactive voltage control target of the virtual synchronous machine in normal condition; K q1 and K u1 should satisfy the following relationship:

[0152] K q1 :K u1 =0~0.1.

[0153] In some preferred embodiments, the internal potential locking strategy can further include:

[0154] When the current command value I cmd,max is greater than the current limiting value I lim and the positive sequence voltage is less than 0.9pu, the current is saturated, the reactive-voltage outer ring does not work, and the internal potential locking strategy outputs a locking signal Frz of the locked internal potential integrator to make the integrator pause integration;

[0155] When the current exits saturation or the voltage recovers, the blocking signal Frz is released, and the hysteresis comparator is used to determine the current exiting saturation.

[0156] In some preferred embodiments, determining the current exiting saturation can further include the following operations:

[0157] When I cmd,max <I lim -Δ dz , it is determined that the current exits saturation; wherein Δ dz represents the dead zone of the hysteresis comparator.

[0158] In some preferred embodiments, Δ dz may be set to 0.03pu.

[0159] An embodiment of the present application provides a grid-forming converter fault ride-through control system, which can include the following modules:

[0160] A controller inner loop control module, which includes a negative sequence current reference generation module and a bias sequence current limiting module; wherein the negative sequence current reference generation module takes the negative sequence dq-axis voltage as input and outputs the negative sequence dq-axis current pre-command to obtain the negative sequence dq-axis current command value, which is used to control the current of the grid-forming converter under asymmetric fault and inject negative sequence reactive current into the grid; the bias sequence current limiting module takes the positive and negative sequence dq-axis current command values as input and outputs the positive and negative sequence current reference values, which are used to control the maximum phase current amplitude of the injected asymmetric current to not exceed the limiting value;

[0161] An active synchronous loop control module, which includes an active reference value limiting module and a synchronous damping link module; wherein the active reference value limiting module takes the positive and negative sequence dq-axis voltage and current at the grid connection point and the active set value as input and outputs the active reference value, which is used to control the upper and lower boundaries of the active reference value; the synchronous damping link module takes the grid-forming converter frequency generated by the active synchronous loop and the detected grid connection point frequency as input and outputs the damping power of the active synchronous loop, which is used to control the damping in power angle swing;

[0162] A reactive voltage loop control module, which includes a reactive voltage variable coefficient control module and an inner potential blocking module; wherein the reactive voltage variable coefficient control module takes the voltage amplitude as input and outputs the reactive voltage droop coefficient, which is used to control the maximum output reactive current; the inner potential blocking module takes the voltage amplitude and the current command value as input and outputs the blocking signal of the inner potential integrator, which is used to suppress overvoltage.

[0163] It should be noted that the steps in the method provided by the application can be realized by corresponding modules, devices, units, etc. in the system. Those skilled in the art can refer to the technical solutions of the method to realize the composition of the system, that is, the embodiments in the method can be understood as preferred examples of constructing the system, which will not be described here.

[0164] The technical solutions provided by the above embodiments of the application will be further described in detail below with reference to a specific application example and the accompanying drawings.

[0165] In order to facilitate understanding of the network configuration type control method proposed by the application, the following explains through a classical single-machine infinite system.

[0166] As shown in Figure 1 , a typical network configuration type converter for new energy and energy storage devices is shown, and the control block diagram is shown in the dashed box in Figure 1 , which mainly includes three modules: active synchronous ring, reactive voltage ring and controller inner ring.

[0167] As shown in Figure 2 , the improvement measures for the current network configuration type control to improve the fault ride-through capability are shown, and there are two improvements for each module in Figure 1 , so there are six improvements in total. The improvement method and the effect after implementation are described in detail below.

[0168] I. Improvement scheme for controller inner ring (two points):

[0169] Improvement 1: Negative sequence current reference generation strategy, corresponding to Figure 2 Module 1 in

[0170] Module input: negative sequence dq axis voltage

[0171] Module output: negative sequence dq axis current pre-command value Note that it is not a current reference value.

[0172] Module function: improve the current control capability of the network configuration type converter under asymmetric fault, and inject appropriate negative sequence reactive current into the grid according to the grid connection guide.

[0173] Implementation scheme:

[0174] A negative sequence current reference generation module is used to simulate the inductive impedance in the negative sequence loop, and the simulated equivalent inductive impedance value is equal to j(K - ) -1 . First, output the negative sequence dq axis current pre-command Its expression is:

[0175]

[0176] where I sd,pre , I sq,pre are the dq-axis current pre-commands, K - is the negative sequence reactive current injection coefficient, T f1 is the voltage filter time constant, s is the Laplace operator, are the dq-axis voltages, · denotes multiplication.

[0177] The negative sequence dq-axis current pre-commands output by the negative sequence current reference generation strategy are used to obtain the negative sequence dq-axis current command values The expression is:

[0178]

[0179] where λ represents the negative sequence current limiting ratio, I lim represents the current limiting value.

[0180] Improvement 2: Sequence current limiting strategy, corresponding to Figure 2 Module 2 in the above figure:

[0181] Module input: positive sequence current command value, negative sequence current pre-command value;

[0182] Strategy output: positive and negative sequence current reference values;

[0183] Strategy function: ensure that the maximum phase current amplitude of the injected asymmetric current does not exceed the limiting value I lim .

[0184] Implementation scheme:

[0185] According to the negative sequence dq-axis current command value and the positive sequence dq-axis current command value , the maximum phase voltage amplitude I cmd,max is calculated, and the expression is:

[0186]

[0187] where, represents the positive / negative sequence current command value amplitude; and represent the positive and negative sequence d-axis current command values and the positive and negative sequence q-axis current command values, respectively; I cmd,Δ represents the maximum phase current command additional modulus, and the expression is:

[0188]

[0189] where γ ∈ [0, -4π / 3, 4π / 3] represents the phase of the three-phase current; represents the positive / negative sequence current command value phase angle;

[0190] Calculate positive sequence current reference value Get:

[0191]

[0192] Calculate negative sequence current reference value Get:

[0193]

[0194] Where, I lim Indicates the current limiting value.

[0195] II. Improvement for active synchronous loop (two points)

[0196] Improvement 3: Active reference value limiting strategy, corresponding Figure 2 Module 3:

[0197] This strategy only affects the boundary of the active reference value, and does not change its reference value size when unnecessary. In this way, the active limiter can realize seamless transition between normal mode and fault ride-through mode.

[0198] Module input: positive and negative sequence dq axis voltage and current of grid connection point, active set value P ref,0 ;

[0199] Module output: active reference value P ref .

[0200] Module function: the active reference value limiter calculates the upper and lower limits of the active power that can be generated in real time, thereby constraining the active reference value, ensuring that the active reference value of the grid-connected converter is within a reasonable range. Especially when the active power that can be generated is small during a fault, this strategy can also ensure that the active reference value does not exceed the active power that can be generated. In this way, the active synchronous loop of the grid-connected converter will not always accelerate during a fault, but only change a very small phase angle, so that the risk of transient synchronous instability after a fault will be greatly reduced.

[0201] Implementation scheme:

[0202] The calculation expression of the active reference value P ref is:

[0203]

[0204] Where P ref,0 represents the active set value, P lim+ and P lim- represent the upper and lower limits of active power transmission, respectively, and their expressions are:

[0205] P lim+ = min{1, αPmax},P lim- = max{-1, aP min}

[0206] where a is the active limiter margin coefficient; P max and P min are the active transmission upper and lower limits, respectively, calculated by:

[0207] Calculate positive sequence available current capacity

[0208]

[0209] where I lim represents the current limiter value; represents the negative sequence current amplitude; I s,Δ represents the maximum phase current additional modulus, which is calculated by:

[0210]

[0211] where γ represents the phase of the three-phase current; and represent the positive and negative sequence d-axis currents, respectively; and represent the positive and negative sequence q-axis currents, respectively;

[0212] The direct current components of the negative sequence active power and the positive sequence reactive power are calculated according to:

[0213]

[0214] where, and represent the positive and negative sequence q-axis voltages, respectively;

[0215] The maximum active power that can be generated by the positive sequence is obtained by:

[0216]

[0217] where, represents the positive sequence voltage amplitude;

[0218] The active upper and lower limit amplitudes P max and P min are calculated by:

[0219] .

[0220] Improvement 4: Synchronous damping link, corresponding to Figure 2 Module 4 in​

[0221] Module input: differential frequency of grid-forming converter generated by active synchronous loop ω δ ;

[0222] Module output: rated damping power of active synchronous loop P d ;

[0223] Module function: this control loop is similar to transient droop compensator in hydro-turbine governor, which functions to increase damping in power angle swing and avoid under-damped swing of grid-forming converter;

[0224] Implementation scheme:

[0225] The input-output relationship of synchronous damping link is:

[0226] P d = D d ·(ω-ω g )

[0227] Wherein, P d represents damping power; ω represents frequency of grid-forming converter; ω g represents detected grid point frequency; D d represents transient droop coefficient.

[0228] In the formula: transient droop coefficient D d The specific value can be designed according to the method introduced in the literature

[24] , which can generally be selected as D d = 20-40.

[0229] Three, improvement for reactive voltage loop (two points)

[0230] Improvement 5: reactive voltage variable coefficient control strategy, corresponding to Figure 2 Module 5 in

[0231] Module input: (positive sequence) voltage amplitude U s ;

[0232] Module output: reactive-voltage droop coefficient;

[0233] Module function: ensure high internal potential during fault and ensure maximum reactive current output, so as to support voltage amplitude during transient state to the greatest extent;

[0234] Implementation scheme:

[0235] When U s is in the range of 0.9-1.1, it is considered that the voltage is in the normal range, at this time the reactive-voltage droop coefficient adopts the size in normal condition (i.e. K q0 and K u0 ); when Us large, i.e. U s <0.85 or U s >1.15, the reactive voltage droop coefficients are set as K q1 and K u1 ; in addition, when 0.85 s <U s <1.10 and U q >1.15, linear transitions are set to prevent voltage chattering problem caused by discontinuous Q-U characteristics. K u and K s are expressed as functions of U

[0236]

[0237] where K q0 and K u0 are generally designed according to the reactive voltage control target of the virtual synchronous machine in normal state, while to obtain better transient voltage support effect, K q1 and K u1 should satisfy the following relationship:

[0238] K q1 :K u1 =0~0.1

[0239] Improvement 6: Internal voltage lockout strategy, corresponding to Figure 2 Module 6 in Fig. 6:

[0240] Module input: (positive sequence) voltage amplitude U s , current command value I cmd,max , whose calculation formula is (1-1);

[0241] Module output: lockout signal Frz of internal voltage integrator;

[0242] Module function: when the current saturates during fault, in order to avoid the internal voltage integrator always accumulates and causes overvoltage triggered in long recovery process after fault clearing.

[0243] Implementation scheme:

[0244] When the current command value is greater than the current limit value (i.e. I cmd,max >I lim , at this time the current saturates, the reactive-voltage outer loop will not work) and the positive sequence voltage is less than 0.9pu, the strategy will lock out the integrator of the internal voltage, so that it pauses integration; when the current exits saturation or the voltage recovers, the lockout signal is released. In order to eliminate the chattering in actual process, hysteresis comparator is used to determine the current exit saturation, i.e. when I cmd,max <I lim -Δdz The current is determined to exit saturation only when dz is the dead zone of the hysteresis comparator, which can be set to 0.03pu, for example.

[0245] The above-mentioned embodiments of the present application can realize the required negative sequence reactive current injection during the asymmetric fault of the power grid according to the current new energy grid-connected guide, while avoiding the current of each phase exceeding the maximum value that the converter can tolerate, by adopting the combination of the negative sequence current reference generation module and the sequence current limiting strategy in the above-mentioned technology.

[0246] The above-mentioned embodiments of the present application can avoid the persistent power angle acceleration of the grid-forming converter during the fault due to the lack of static operating point of the active loop, thereby further causing the transient power angle instability after the fault is cleared, and can also increase the damping of the power angle swing, so that the power angle swing is stabilized in a relatively short time, thereby further improving the power angle stability, by adopting the combination of the active reference value limiting strategy and the synchronous damping link in the above-mentioned technology.

[0247] The above-mentioned embodiments of the present application can enable the grid-forming converter to emit the maximum short-circuit current within the current limiting range during the fault to support the voltage amplitude during the transient state, while avoiding the persistent accumulation of the internal potential due to the temporary failure of the reactive voltage control during the fault, thereby ensuring that the voltage after the fault recovery can be smoothly transitioned without overvoltage problems, by adopting the combination of the reactive voltage variable coefficient control strategy and the internal potential locking strategy in the above-mentioned technology.

[0248] As shown in Figure 3 , the topology of the power generation unit with the grid-connected converter as the interface is shown, the voltage and current sensors collect the three-phase voltage and current of the measurement point and transmit them to the grid-forming control module of the converter; the output of the control module is the modulation wave of the grid-connected converter, which is used to control the switching on and off of the grid-connected converter.

[0249] As shown in Figure 4 (a)-(e), the superiority of the method provided in the above-mentioned embodiments of the present application is shown, in Figure 4 , a two-phase ground fault occurs at the location of the power grid, and from the simulation results, it can be seen that the control strategy can ensure that the short-circuit current is within the limiting value during the fault, reduce the unbalance degree of the three-phase voltage, and maintain the transient voltage stable during the fault; after the fault of the power grid is cleared, the active power, voltage and frequency are quickly restored to be stable.

[0250] As shown in Figure 5 (a)-(c), in contrast, if the control strategy is not adopted, the grid-forming converter cannot realize stable voltage support during the fault, and transient instability occurs after the fault is cleared.

[0251] To further show the effect of each module, the following comparison is made.

[0252] As Figure 6 shown in (a) and (b), the effect of the negative sequence current reference generation module is shown. It can be seen that if the negative sequence current reference generation module is adopted, the grid-connected converter can automatically generate negative sequence reactive current during two-phase ground (asymmetric) short circuit; compared with not adopting the negative sequence current reference generation module, the negative sequence voltage amplitude is significantly reduced, indicating that the degree of asymmetry of the voltage is improved.

[0253] As Figure 7 shown in (a) and (b), the effect of the negative sequence current reference generation module is shown. It can be seen that if the negative sequence current reference generation module is adopted, the grid-connected converter can automatically generate negative sequence reactive current during two-phase ground (asymmetric) short circuit; compared with not adopting the negative sequence current reference generation module, the negative sequence voltage amplitude is significantly reduced, indicating that the degree of asymmetry of the voltage is improved.

[0254] As Figure 8 shown in (a) and (b), the effect of the negative sequence current reference generation module is shown. It can be seen that if the negative sequence current reference generation module is adopted, the grid-connected converter can automatically generate negative sequence reactive current during two-phase ground (asymmetric) short circuit; compared with not adopting the negative sequence current reference generation module, the negative sequence voltage amplitude is significantly reduced, indicating that the degree of asymmetry of the voltage is improved.

[0255] As Figure 9 shown in (a) and (b), the effect of the negative sequence current reference generation module is shown. It can be seen that if the negative sequence current reference generation module is adopted, the grid-connected converter can automatically generate negative sequence reactive current during two-phase ground (asymmetric) short circuit; compared with not adopting the negative sequence current reference generation module, the negative sequence voltage amplitude is significantly reduced, indicating that the degree of asymmetry of the voltage is improved.

[0256] As Figure 10 shown in (a) and (b), the effect of the negative sequence current reference generation module is shown. It can be seen that if the negative sequence current reference generation module is adopted, the grid-connected converter can automatically generate negative sequence reactive current during two-phase ground (asymmetric) short circuit; compared with not adopting the negative sequence current reference generation module, the negative sequence voltage amplitude is significantly reduced, indicating that the degree of asymmetry of the voltage is improved.

[0257] As Figure 11As shown, the effect of internal potential blocking is shown. It can be seen that if the internal potential is timely blocked during the fault, the internal potential does not rise very high during the fault, and thus can be quickly recovered after the fault, so that the voltage amplitude has a relatively smooth transition, and the same size of reactive power as when not blocked can be issued; if the internal potential is not blocked, the internal potential rises very high during the fault (the maximum value is limited to 2.5pu in the simulation), and at the fault clearance moment, since the internal potential is still very high, a very high overvoltage and reactive power overshoot occur, which may cause harm to the safety of the equipment.

[0258] An embodiment of the present application provides a computer terminal, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor is configured to execute the computer program to implement the method of any one of the above-mentioned embodiments of the present application, or run the system of any one of the above-mentioned embodiments of the present application.

[0259] Optionally, the memory is configured to store programs; the memory can comprise volatile memory (English: volatile memory), such as random access memory (English: random-access memory, abbreviation: RAM), for example, static random access memory (English: static random-access memory, abbreviation: SRAM), double data rate synchronous dynamic random access memory (English: Double Data Rate Synchronous Dynamic Random Access Memory, abbreviation: DDR SDRAM) and the like; the memory can also comprise non-volatile memory (English: non-volatile memory), such as flash memory (English: flash memory). The memory is configured to store computer programs (such as application programs, functional modules and the like for implementing the above-mentioned method), computer instructions and the like, and the above-mentioned computer programs, computer instructions and the like can be stored in one or more memories in a partitioned manner. And the above-mentioned computer programs, computer instructions, data and the like can be called by the processor.

[0260] The above-mentioned computer programs, computer instructions and the like can be stored in one or more memories in a partitioned manner. And the above-mentioned computer programs, computer instructions, data and the like can be called by the processor.

[0261] The processor is configured to execute the computer program stored in the memory to implement each step in the method or each module of the system involved in the above-mentioned embodiments. For details, please refer to the related description in the above-mentioned method and system embodiments.

[0262] The processor and the memory can be independent structures or integrated structures.

[0263] An embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is used for executing the method of any one of the above-mentioned embodiments of the present application or running the system of any one of the above-mentioned embodiments of the present application when executed by a processor.

[0264] Those skilled in the art know that, in addition to implementing the system and each device thereof provided by the present application in the form of pure computer readable program code, the system and each device thereof provided by the present application can also be implemented in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps to achieve the same functions. Therefore, the system and each device thereof provided by the present application can be considered as a hardware component, and the devices included therein for achieving various functions can also be considered as structures in the hardware component; the devices for achieving various functions can also be considered as both software modules for implementing the method and structures in the hardware component.

[0265] An embodiment of the present application further provides a grid-forming converter, which adopts the fault ride-through control method of any one of the above-mentioned embodiments of the present application or the fault ride-through control system of any one of the above-mentioned embodiments of the present application to control fault ride-through.

[0266] An embodiment of the present application further provides a power supply system, and a grid-forming converter of the power supply system adopts the fault ride-through control method of any one of the above-mentioned embodiments of the present application or the fault ride-through control system of any one of the above-mentioned embodiments of the present application to control fault ride-through.

[0267] The above-mentioned embodiments of the present application are described. It should be understood that the present application is not limited to the above-mentioned specific embodiments, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application.

[0268] The above-mentioned embodiments of the present application are described. It should be understood that the present application is not limited to the above-mentioned specific embodiments, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. A method for grid-forming converter fault ride-through control, the method comprising: determining a fault condition; and in response to the fault condition, controlling a plurality of power converters to operate in a grid-forming mode. Comprise: For the controller inner loop, a negative sequence current reference generation strategy and a bias sequence current limiting strategy are provided respectively; wherein, the negative sequence current reference generation strategy takes negative sequence dq axis voltage as input, outputs negative sequence dq axis current pre-command, obtains negative sequence dq current instruction value, is used for controlling the current of grid-connected converter under asymmetric fault, and injects negative sequence reactive current to power grid; the bias sequence current limiting strategy takes positive sequence and negative sequence dq axis current instruction value as input, outputs positive sequence and negative sequence current reference value, and is used for controlling the maximum phase current amplitude of injected asymmetric current to not exceed limiting value; For the active synchronous loop, an active reference value limiting strategy and a synchronous damping link are provided respectively; wherein, the active reference value limiting strategy takes grid point positive and negative sequence dq axis voltage and current and active set value as input, outputs active reference value, and is used for controlling upper and lower boundaries of active reference value; the synchronous damping link takes the grid-connected converter frequency generated by active synchronous loop and the detected grid point frequency as input, outputs the damping power of active synchronous loop, and is used for controlling damping in power angle swing; For the reactive voltage loop, a reactive voltage variable coefficient control strategy and an internal potential locking strategy are provided respectively; wherein, the reactive voltage variable coefficient control strategy takes voltage amplitude as input, outputs reactive voltage droop coefficient, and is used for controlling the maximum output reactive current; the internal potential locking strategy takes voltage amplitude and current instruction value as input, outputs the locking signal of internal potential integrator, and is used for inhibiting overvoltage.

2. The method of claim 1, wherein, The negative sequence current reference generation strategy comprises: Output negative sequence dq-axis current pre-command The expression is: where I sd,pre , I sq,pre are the dq-axis current pre-commands, K - is the negative sequence reactive current injection coefficient, T f1 is the voltage filter time constant, s is the Laplace operator, are the dq-axis voltages, · denotes multiplication; The negative sequence dq-axis current pre-command output according to the negative sequence current reference generation strategy is obtained as a negative sequence dq-axis current command value The expression is: where λ represents a negative sequence current clipping ratio, I lim represents a current clipping value. 3.The network configuration transformer fault ride-through control method of claim 1, wherein, The bias sequence current limiting strategy comprises: According to the negative sequence dq-axis current command value and the positive sequence dq-axis current command value The maximum phase voltage amplitude I cmd,max is calculated, and its expression is: wherein, denotes the positive / negative sequence current command value amplitude; and denote the positive and negative sequence d-axis current command values and the positive and negative sequence q-axis current command values, respectively; cmd,Δ denotes the maximum phase current command additional modulus, the expression of which is: wherein γ ∈ [0, -4π / 3, 4π / 3] represents the phase of the three-phase current; denotes the positive / negative sequence current command phase angle; Computing positive sequence current reference values Resulting in: Computing a negative sequence current reference value Obtained: where I lim represents the current limiting value.

4. The method of claim 1, wherein the active power Setpoint P ref,0 The active reference value P is obtained by the active reference value limiting strategy ref .

5. The method of claim 4, wherein, The active reference value limiting strategy comprises: said active reference value P ref whose expression is: where P ref,0 represents the active setpoint, P lim+ and P lim- represent the active transmission upper and lower limits, respectively, and are expressed as: P lim+ = min{1, aP max}, P lim = max{-1, aP min} wherein a is an active clipping margin coefficient; P max and P min are the upper and lower active transmission limits, respectively, calculated by: Pmax = Pmax,0 + a · (Pmax,0 - Pmin,0) Calculating positive sequence available current capacity where I lim represents the current limit value; represents the negative sequence current amplitude; I s,Δ represents the maximum phase current additional modulus, which is calculated by the following formula: where γ represents the phase of the three-phase current; and represent the positive and negative sequence d-axis currents, respectively; and represent the positive and negative sequence q-axis currents, respectively; The direct components of the negative sequence active power and the positive sequence reactive power are calculated according to the following formulae: wherein and Vd and Vq represent positive and negative sequence q-axis voltages, respectively; The positive sequence maximum active power is obtained by the following equation is: wherein denotes the positive sequence voltage magnitude; The active upper and lower limit amplitudes P are obtained by the following formula max and P min are given by: 6.The network configuration transformer fault ride-through control method of claim 1, wherein, The input and output relationship of the synchronous damping link is: P d = D d ·(ω-ω g ) where P d represents the damping power; ω represents the frequency of the grid-forming converter; ω g represents the detected grid point frequency; D d represents the transient droop coefficient.

7. The method of claim 1, wherein, The reactive voltage variable coefficient control strategy comprises: When the voltage amplitude U s In the range of 0.9-1.1, the voltage is considered to be in the normal interval, at which time the reactive voltage droop coefficient adopts the size in the normal case, recorded as K q0 And K u0 , wherein K q represents; K u represents; When the voltage amplitude U s is large, i.e. U s < 0.85 or U s > 1.15, the reactive voltage droop coefficients are set respectively as K q1 and K u1 ; When 0.85 ≤ U s <0.90 or 1.10 < U s ≤ 1.15, a linear transition is provided, setting K q and K u as a function of U s with the expression: where K q1 and K u1 the following relationship should be satisfied: K q1 :K u1 = 0-0.

1.

8. The method of claim 1, wherein, The internal potential locking strategy comprises: When the current command value I cmd,max is greater than the current limit value I lim and the positive sequence voltage is less than 0.9 pu, at this time the current is saturated, the reactive-voltage outer loop does not work, the inner potential locking strategy outputs the locking signal Frz of locking the inner potential integrator, so that the integrator pauses integration; When the current exits saturation or the voltage recovers, the locking signal Frz is released, and the hysteresis comparator is used for judging current desaturation; wherein: When I cmd,max < I lim - Δ dz the current is determined to exit saturation; where Δ dz represents a dead zone of the hysteresis comparator.

9. A meshed transformer fault ride-through control system, characterized by, Comprise: The controller inner loop control module comprises a negative sequence current reference generation module and a bias sequence current limiting module; wherein, the negative sequence current reference generation module takes negative sequence dq axis voltage as input, outputs negative sequence dq axis current pre-command, obtains negative sequence dq current instruction value, and is used for controlling the current of grid-connected converter under asymmetric fault and injecting negative sequence reactive current to power grid; the bias sequence current limiting module takes positive sequence and negative sequence dq axis current instruction value as input, outputs positive sequence and negative sequence current reference value, and is used for controlling the maximum phase current amplitude of injected asymmetric current to not exceed limiting value; The active synchronous loop control module comprises an active reference value limiting module and a synchronous damping link module; wherein, the active reference value limiting module takes grid point positive and negative sequence dq axis voltage and current and active set value as input, outputs active reference value, and is used for controlling upper and lower boundaries of active reference value; the synchronous damping link module takes the grid-connected converter frequency generated by active synchronous loop and the detected grid point frequency as input, outputs the damping power of active synchronous loop, and is used for controlling damping in power angle swing; A reactive voltage loop control module, which comprises a reactive voltage variable coefficient control module and an internal potential blocking module; wherein the reactive voltage variable coefficient control module takes the voltage amplitude as input and outputs the reactive voltage droop coefficient for controlling the maximum reactive current output; the internal potential blocking module takes the voltage amplitude and the current instruction value as input and outputs the blocking signal of the internal potential integrator for suppressing overvoltage.

10. A meshed transformer, characterized by The grid-forming converter adopts the fault ride-through control method in any one of claims 1-8 or the fault ride-through control system in claim 9 to control fault ride-through.

11. A power supply system characterized by comprising: The grid-forming converter of the power supply system adopts the fault ride-through control method in any one of claims 1-8 or the fault ride-through control system in claim 9 to control fault ride-through.

12. A computer terminal comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to execute the method in any one of claims 1-8 or run the system in claim 9.

13. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to execute the method in any one of claims 1-8 or run the system in claim 9.

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