A control method, system, electronic device and medium for asymmetric fault ride-through

Abstract

The invention discloses a control method, system, electronic device and medium for asymmetric fault ride-through, which relate to the field of electric power system. The invention determines the reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, so that the reactive current command finally obtained can meet the output requirement of the grid guideline for negative sequence reactive current, and can also effectively suppress the double frequency fluctuation of active power. The active current command is determined under the premise of not damaging the converter. It is ensured that the wind power generation system can output reactive current that meets the requirements of the grid guideline during the fault period, suppress the double frequency fluctuation of active power of the grid connection point of the wind power generation system during the fault period, and proportion the active current according to the situation of the converter. On the basis of not adding hardware equipment, the stability of the wind power generation system during the asymmetric fault of the grid is enhanced, the double frequency fluctuation of active power of the grid connection point of the wind power generation system during the fault period is suppressed, and the grid-connected power quality of the wind power generation system is improved.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a control method, system, electronic equipment and medium for asymmetric fault ride-through. Background Art

[0002] With the continuous increase in my country's energy demand and the rapid development of wind power generation technology, my country's wind energy utilization has gradually shifted to the centralized development of large-scale wind power bases, and the fault ride-through capability of large-capacity grid-connected wind farms has become a key indicator of grid-connected wind power technology. In actual power grids, large voltage drops may occur due to reasons such as the start-up of large-power motors and short-circuit faults in the power grid, which may cause a large drop in the voltage at the common point of the wind farm at the end of the power grid. At this time, the wind farm often actively trips to protect its own safety, resulting in a larger power shortage in the power system. This situation will bring serious harm to the safety and stability of the wind farm and the entire power system. In addition, with the increase in the proportion of wind power capacity in the power grid, the fluctuation of large-scale grid-connected wind power during faults will have a significant impact on the voltage and frequency of the power grid, and will bring about a series of power quality problems such as voltage fluctuations, frequency fluctuations and flicker in the power system, which will undoubtedly deteriorate the operating characteristics of the power grid and increase the difficulty of power system operation and control. At the same time, as the requirements for wind farm grid connection become more and more stringent, the low voltage ride-through capability of wind turbines under asymmetric faults is also included in the assessment scope of the grid connection guidelines. Therefore, how to improve the fault ride-through capability of wind farms and improve the quality of grid-connected power in the event of a grid voltage fault is an important issue that must be addressed in wind power technology. There is no effective method in the prior art that can comprehensively consider various factors to solve this problem. Summary of the invention

[0003] The purpose of the present invention is to provide a control method, system, electronic device and medium for asymmetric fault ride-through, to ensure that during a fault, a wind power generation system can output reactive current that meets the requirements of the grid guidelines, to suppress the double frequency fluctuation of the active power of the wind power generation system grid connection point during the fault, and to proportion the active current according to the situation of the converter, so as to enhance the stability of the wind power generation system during an asymmetric fault of the grid without adding hardware equipment, to suppress the double frequency fluctuation of the active power of the wind power generation system grid connection point during the fault, and to improve the grid-connected power quality of the wind power generation system.

[0004] In order to solve the above technical problems, the present invention provides a control method for asymmetric fault ride-through, which is applied to a control system of a wind power generation system, wherein the wind power generation system is connected to a power grid, and the connection point with the power grid is a grid connection point, the wind power generation system also includes a wind turbine and a converter, one end of the converter is connected to the power grid through the grid connection point, and the other end is connected to the wind turbine, and the control system is connected to the converter and the power grid respectively; the control method for asymmetric fault ride-through includes:

[0005] Determining a reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, wherein the preset comparison coefficient is related to the reactive current required by the grid guidelines and the double frequency fluctuation of the active power output by the converter;

[0006] Determining an active current instruction of the converter based on a given active power of the wind turbine generator set and an active power limit value of the wind turbine generator set, wherein the active power limit value of the wind turbine generator set is a limit value of the active power that can be output without damaging the converter;

[0007] The reactive current command and the active current command are output to the converter to control the converter to achieve asymmetric fault ride-through of the wind power generation system.

[0008] Optionally, the preset comparison coefficient is a comparison coefficient of a voltage positive sequence component of the grid connection point, and determining the reactive current instruction of the converter based on the voltage of the grid connection point and the preset comparison coefficient includes:

[0009] Determining a voltage positive sequence component and a voltage negative sequence component at the grid connection point;

[0010] When the voltage positive sequence component of the grid connection point is greater than the comparison coefficient of the voltage positive sequence component of the grid connection point, determining the reactive current command of the converter based on the first relational expression;

[0011] When the voltage positive sequence component of the grid connection point is less than the comparison coefficient of the voltage positive sequence component of the grid connection point, determining the reactive current command of the converter based on a second relational expression;

[0012] The first relation is:

[0013]

[0014] The second relation is:

[0015]

[0016] in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, is the positive sequence reactive current command of the converter, It is the negative sequence reactive current instruction of the converter.

[0017] Optionally, before determining the active current instruction of the converter based on the given active power of the wind turbine generator set and the active power limit value of the wind turbine generator set, the method further includes:

[0018] The active power limit value of the wind turbine generator set is determined based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter.

[0019] Optionally, before determining the active power limit value of the wind turbine generator set based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter, the method further includes:

[0020] Determine a positive-sequence voltage component and a negative-sequence voltage component of the grid-connected point, and determine an asymmetry of the grid voltage based on the positive-sequence voltage component and the negative-sequence voltage component of the grid-connected point;

[0021] Correspondingly, the determining of the active power limit value of the wind turbine generator set based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter includes:

[0022] The active power limit value of the wind turbine generator set is determined based on the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter.

[0023] Optionally, the determining the active power limit value of the wind turbine generator set based on the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter includes:

[0024] Determine a relationship between the active power limit value of the wind turbine generator set and the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter, and determine the active power limit value of the wind turbine generator set based on the relationship;

[0025] The relationship between the active power limit value of the wind turbine generator set, the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter is:

[0026]

[0027] Among them, P limit is the active power limit value of the wind turbine generator set, is the positive sequence component of the voltage at the grid connection point, δ is the asymmetry of the grid voltage, I g_max is the maximum value of the allowable operating current of the converter.

[0028] Optionally, the determining the active current instruction of the converter based on the given active power of the wind turbine generator set and the active power limit value of the wind turbine generator set includes:

[0029] When the given active power of the wind turbine generator set is greater than the active power limit value of the wind turbine generator set, determining the active current command of the converter based on a third relational expression;

[0030] When the given active power of the wind turbine generator set is less than the active power limit value of the wind turbine generator set, determining the active current command of the converter based on a fourth relational expression;

[0031] The third relational expression is:

[0032]

[0033] The fourth relational expression is:

[0034]

[0035] in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, I g_max is the maximum value of the permissible operating current of the converter, P ref is the given active power of the wind turbine generator set, is the positive sequence active current command of the converter, is the negative-sequence active current instruction of the converter.

[0036] Optionally, the converter includes a machine-side converter and a grid-side converter, one end of the machine-side converter is connected to the wind turbine set, and the other end is connected to one end of the grid-side converter, and the other end of the grid-side converter is connected to the power grid through the grid connection point, and the reactive current instruction and the active current instruction are output to the converter to control the converter to realize asymmetric fault ride-through of the wind power generation system, including:

[0037] The reactive current command and the active current command are output to a current controller of the grid-side converter, so that the grid-side converter controls the wind turbine generator set based on the reactive current command and the active current command.

[0038] In order to solve the above technical problems, the present invention also provides a control system for asymmetric fault ride-through, which is applied to a control system of a wind power generation system, wherein the wind power generation system is connected to a power grid, and the connection point with the power grid is a grid connection point, the wind power generation system also includes a wind turbine and a converter, one end of the converter is connected to the power grid through the grid connection point, and the other end is connected to the wind turbine, and the control system is connected to the converter and the power grid respectively; the control system for asymmetric fault ride-through includes:

[0039] A reactive current command determination unit, configured to determine a reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, wherein the preset comparison coefficient is related to the reactive current required by the grid code and the double frequency fluctuation of the active power output by the converter;

[0040] An active current instruction determination unit, configured to determine an active current instruction of the converter based on a given active power of the wind turbine set and an active power limit value of the wind turbine set, wherein the active power limit value of the wind turbine set is a limit value of the active power that can be output without damaging the converter;

[0041] The command output unit is used to output the reactive current command and the active current command to the converter to control the converter to achieve asymmetric fault ride-through of the wind power generation system.

[0042] In order to solve the above technical problems, the present invention further provides an electronic device, comprising:

[0043] Memory for storing computer programs;

[0044] A processor is used to implement the steps of the control method for asymmetric fault ride-through as described above.

[0045] In order to solve the above technical problems, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the control method for asymmetric fault crossing as described above are implemented.

[0046] The present invention provides a control method for asymmetric fault crossing, first determining a preset comparison coefficient related to the reactive current required by the grid guideline and the double frequency fluctuation of the active power output by the converter, and then determining the reactive current command of the converter based on the voltage of the grid connection point and the preset comparison coefficient, so that the reactive current command finally obtained can meet the output requirement of the grid guideline for the negative sequence reactive current, and can also effectively suppress the double frequency fluctuation of the active power, and the active current command is determined without damaging the converter; ensuring that the wind power generation system can output the reactive current that meets the grid guideline during the fault, suppressing the double frequency fluctuation of the active power of the grid connection point of the wind power generation system during the fault, and matching the active current according to the situation of the converter, on the basis of not adding hardware equipment, enhancing the stability of the wind power generation system during the asymmetric grid fault, suppressing the double frequency fluctuation of the active power of the grid connection point of the wind power generation system during the fault, and improving the grid-connected power quality of the wind power generation system.

[0047] The present invention also provides a control system, electronic device and computer-readable storage medium for asymmetric fault ride-through, which have the same beneficial effects as the above-mentioned control method for asymmetric fault ride-through. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0049] Figure 1 A schematic flow chart of a control method for asymmetric fault ride-through provided by the present invention;

[0050] Figure 2 A schematic structural diagram of a wind power generation system provided by the present invention;

[0051] Figure 3 A schematic diagram of the structure of a wind power generation system and its control system provided by the present invention;

[0052] Figure 4 A schematic diagram of a first output signal waveform of a wind power generation system provided by the present invention;

[0053] Figure 5 A schematic diagram of a second output signal waveform of a wind power generation system provided by the present invention;

[0054] Figure 6 A schematic diagram of a third output signal waveform of a wind power generation system provided by the present invention;

[0055] Figure 7 A schematic diagram of a fourth output signal waveform of a wind power generation system provided by the present invention;

[0056] Figure 8 A schematic diagram of a fifth output signal waveform of a wind power generation system provided by the present invention;

[0057] Fig. 9 A schematic diagram of a sixth output signal waveform of a wind power generation system provided by the present invention;

[0058] Fig.10 A schematic diagram of the structure of a control system for asymmetric fault ride-through provided by the present invention;

[0059] Fig.11 The present invention provides a schematic structural diagram of an electronic device. DETAILED DESCRIPTION

[0060] The core of the present invention is to provide a control method, system, electronic device and medium for asymmetric fault ride-through, to ensure that the wind power generation system can output reactive current that meets the requirements of the grid guidelines during the fault, to suppress the double frequency fluctuation of the active power of the wind power generation system grid connection point during the fault, and to proportion the active current according to the situation of the converter, so as to enhance the stability of the wind power generation system during asymmetric grid faults without adding hardware equipment, to suppress the double frequency fluctuation of the active power of the wind power generation system grid connection point during the fault, and to improve the grid-connected power quality of the wind power generation system.

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Please refer to Figure 1 , Figure 1 A schematic diagram of a flow chart of a control method for asymmetric fault ride-through provided by the present invention; please refer to Figure 2 , Figure 2 A schematic diagram of the structure of a wind power generation system provided by the present invention; please refer to Figure 3 , Figure 3A schematic diagram of the structure of a wind power generation system and its control system provided by the present invention; To solve the above technical problems, the present invention provides a control method for asymmetric fault ride-through, which is applied to the control system of the wind power generation system. The wind power generation system is connected to a power grid, and the connection point with the power grid is a grid connection point. The wind power generation system also includes a wind turbine and a converter. One end of the converter is connected to the power grid through the grid connection point, and the other end is connected to the wind turbine. The control system is connected to the converter and the power grid respectively. The control method for asymmetric fault ride-through includes:

[0063] S11: determining a reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, wherein the preset comparison coefficient is related to the reactive current required by the grid guidelines and the double frequency fluctuation of the active power output by the converter;

[0064] Taking into account the stability and reliability of the entire power system, the grid guidelines have clear output requirements for the reactive current injected by the converter into the grid connection point, especially the negative sequence reactive current. Therefore, in the process of determining the reactive current command of the converter, it is necessary to take into account the reactive current required by the grid guidelines. At the same time, it is also considered that the double frequency fluctuation of the active power output of the converter will affect the safety and reliability of the entire power system. Therefore, when determining the preset comparison coefficient, the double frequency fluctuation of the active power output of the converter corresponding to different preset comparison coefficients can be determined. On the premise that the reactive current injected by the converter into the grid connection point meets the reactive current required by the grid guidelines, the double frequency fluctuation of the active power output of the converter is suppressed as much as possible, so as to determine a more appropriate value of the preset comparison coefficient. At the same time, the reactive current command of the converter is also related to the real-time voltage of the grid connection point. Therefore, it is necessary to determine the reactive current command of the converter according to the voltage of the grid connection point and the preset comparison coefficient. The present application does not make any special limitation on the method of determining the voltage of the grid connection point and the preset comparison coefficient. The voltage of the grid connection point can be detected in real time by the sampling module, and the preset comparison coefficient can be derived according to the actual situation of the wind power system when applied.

[0065] S12: determining an active current command of the converter based on a given active power of the wind turbine generator set and an active power limit value of the wind turbine generator set, wherein the active power limit value of the wind turbine generator set is a limit value of the active power that can be output without damaging the converter;

[0066] It is not difficult to understand that the active current command of the converter is not only related to the current working condition of the wind turbine set, but also to parameters such as the capacity of the converter itself. Parameters such as the capacity of the converter itself will affect the active power limit of the wind turbine set. Under different working conditions of the wind turbine set, the calculation method of the active current command of the converter is also different. Therefore, it is necessary to determine the active current command of the converter based on the given active power of the wind turbine set and the active power limit of the wind turbine set. This application does not make any special restrictions on the given active power of the wind turbine set and the method for determining the active power limit of the wind turbine set. The given power of the wind turbine set is related to the target power required by the actual application, and can be directly determined according to the setting value of the staff or the application requirements. The active power limit of the wind turbine set can be determined based on the actual situation of the converter and the entire wind power generation system.

[0067] S13: Outputting the reactive current command and the active current command to the converter to control the converter to achieve asymmetric fault ride-through of the wind power generation system.

[0068] It is understandable that the wind power generation system is connected to the power grid through the grid connection point and participates in the entire power system. When an asymmetric fault occurs in the entire power system, the control system of the wind power generation system needs to control the converter to inject reactive current into the grid connection point through reactive current instructions to support current recovery in the power system. At the same time, it is also necessary to match the reactive current instructions with the corresponding active current instructions to ensure the stability and reliability of the entire power system. Therefore, when an asymmetric fault occurs in the entire power system, the wind power generation system will determine the reactive current instructions and active current instructions output to the converter according to the current voltage conditions of the grid connection point and the specific conditions of the converter and wind turbine in the wind power generation system, thereby realizing the asymmetric fault crossing process of the entire wind power generation system and the entire power system.

[0069] It is not difficult to understand that the present application does not make any special limitations on the specific process of how the converter realizes the asymmetric fault ride-through of the wind power generation system. Considering that the asymmetric fault ride-through is mainly realized by injecting reactive current into the grid connection point through the converter, the control system of the MSC (machine-side converter) of the wind power generation system is usually kept unchanged during the fault. The GSC (grid-side converter) receives active current instructions and reactive current instructions, and the active current instructions are divided into positive-sequence active current instructions and negative-sequence active current instructions, and the reactive current instructions are divided into positive-sequence reactive current instructions and negative-sequence reactive current instructions.

[0070] It should be noted that there are many options for how to determine whether an asymmetric fault has occurred in the power system. Usually, it is possible to directly determine whether there is a fault in the power system based on the voltage condition at the grid connection point or any point in the power grid system. When a fault is detected at one point in the power grid, this point can be called the fault point. The present application does not make any special restrictions on the specific implementation methods of the wind power generation system and the entire power system. The wind power generation system can adopt a permanent magnet wind power system and other types of power generation systems. The point where the wind power generation system is connected to the power grid is the PCC (point of common connection), which is referred to as the grid connection point or the common connection point. The present application does not make any special restrictions on the specific types and implementation methods of the control system, converter and wind turbine in the wind power generation system.

[0071] The present invention provides an asymmetric fault ride-through method for improving the power quality of a wind power generation system, which can improve the safe and stable operation capability of the wind power generation system under an asymmetric fault in the power grid, and solve the problem of double frequency fluctuation of active power outputted from the grid connection point of the wind power generation system during an asymmetric fault. The asymmetric fault ride-through is mainly achieved by adjusting the command ratio of the positive and negative sequence active current and the positive and negative sequence reactive current outputted by the grid-side converter in the wind power generation system.

[0072] As a specific embodiment, Figure 2 and Figure 3 For example, Figure 2 This is a structural diagram of a permanent magnet wind power generation system with a total capacity of 50MW connected to the power system. The permanent magnet wind power generation system is connected to the large power grid through a public connection point. The PCC and the power grid can also be directly connected by a transformer T and an impedance Z. L (R L ,X L ), the wind turbine generator in the wind turbine unit adopts PMSG (permanent magnet synchronous generator); Figure 3 The control block diagram of a permanent magnet wind power generation system under a power grid fault is shown. The control objects of the entire control system mainly include GSC and MSC. The control system includes a grid-side converter current command calculation module, a grid-side positive and negative sequence current controller module, and a machine-side converter control module. Among them, the grid-side positive and negative sequence current controller module is used to control the grid-side positive and negative sequence current during an asymmetric fault of the power grid, and the machine-side converter control module is used to maintain the DC bus voltage unchanged; the control system first calculates the voltage U gabc_p And the current i gabc_pReal-time detection and collection are performed, and the PLL (Phase Locked Loop) composed of PLL+ and PLL- is used to extract the θ in the voltage of the power grid. g_P and ω g_P , in order to determine the frequency and phase of the grid voltage, and at the same time, the voltage U gabc_p And the current i gabc_p Perform coordinate transformation to obtain the transformed voltage u gαβ_P and current i gαβ_P , and then reuse and The converted current and voltage are further Fourier transformed and then further processed by a notch filter to obtain the positive sequence component of the voltage at the grid connection point. Negative sequence voltage component Current positive sequence component and the negative sequence component of the current The grid-side converter current command calculation module receives these parameters to determine the real-time status of the grid connection point and receives the given active power P of the wind turbine. ref After that, the grid-side converter current command calculation module can calculate the positive sequence active current command output to the grid-side converter based on the received quantities and the internal pre-set program. Negative sequence active current command Positive sequence reactive current command and negative sequence reactive current command After receiving these current commands, the grid-side positive and negative sequence current controller module outputs the corresponding voltage command U gα and U gβ At the same time, the grid-side positive and negative sequence current controller module is connected to the grid-side converter through SVPWM (Space Vector Pulse Width Modulation), and the control instructions corresponding to the active current instruction and the reactive current instruction are output to the grid-side converter, thereby controlling the grid-side converter to realize the asymmetric fault ride-through of the wind power generation system. The machine-side converter control module uses the voltage instruction U corresponding to the original control strategy sα and U sβ The SVPWM is connected to the machine-side converter to realize the control of the machine-side converter.

[0073] The asymmetric fault ride-through method provided by the present invention can be used to improve the power quality of a permanent magnet wind power system, and can also be used to improve the safe and stable operation capability of a permanent magnet wind power generation system under an asymmetric fault, and solves the problem of double frequency fluctuation of the total output active power at the grid connection point of a permanent magnet wind power generation system, and belongs to the technical field of wind power generation; the present invention provides an instruction ratio of positive and negative sequence active current and reactive current output by a grid-side converter of a permanent magnet wind power generation system on the basis of fully considering the converter capacity and the operating conditions of the unit, and effectively solves the problem of double frequency of the total output active power of a permanent magnet wind power generation system under an asymmetric fault of the power grid, and improves the stable operation capability of the permanent magnet wind power generation system and the grid-connected power quality of the system.

[0074] The present invention provides a control method for asymmetric fault crossing, first determining a preset comparison coefficient related to the reactive current required by the grid guideline and the double frequency fluctuation of the active power output by the converter, and then determining the reactive current command of the converter based on the voltage of the grid connection point and the preset comparison coefficient, so that the reactive current command finally obtained can meet the output requirement of the grid guideline for the negative sequence reactive current, and can also effectively suppress the double frequency fluctuation of the active power, and the active current command is determined without damaging the converter; ensuring that the wind power generation system can output the reactive current that meets the grid guideline during the fault, suppressing the double frequency fluctuation of the active power of the grid connection point of the wind power generation system during the fault, and matching the active current according to the situation of the converter, on the basis of not adding hardware equipment, enhancing the stability of the wind power generation system during the asymmetric grid fault, suppressing the double frequency fluctuation of the active power of the grid connection point of the wind power generation system during the fault, and improving the grid-connected power quality of the wind power generation system.

[0075] Based on the above embodiments:

[0076] As an optional embodiment, the preset comparison coefficient is the comparison coefficient of the voltage positive sequence component of the grid connection point, and the reactive current instruction of the converter is determined based on the voltage of the grid connection point and the preset comparison coefficient, including:

[0077] Determine the voltage positive sequence component and voltage negative sequence component at the grid connection point;

[0078] When the voltage positive sequence component of the grid connection point is greater than the comparison coefficient of the voltage positive sequence component of the grid connection point, determining the reactive current command of the converter based on the first relational expression;

[0079] When the voltage positive sequence component of the grid connection point is less than the comparison coefficient of the voltage positive sequence component of the grid connection point, determining the reactive current command of the converter based on the second relational expression;

[0080] The first relation is:

[0081]

[0082] The second relationship is:

[0083]

[0084] in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, is the positive sequence reactive current command of the converter, It is the negative sequence reactive current instruction of the converter.

[0085] It is not difficult to understand that under the conditions of meeting the reactive current required by the grid guidelines and suppressing the double frequency fluctuation of the active power output of the converter, the preset comparison coefficient that can be derived is the comparison coefficient of the voltage positive sequence component of the grid connection point, which is Figure 2 Taking the wind power generation system shown in the figure as an example, the comparison coefficient of the voltage positive sequence component of the grid connection point is derived to be 0.45. On this basis, the reactive current command of the converter can be calculated. The specific calculation steps are:

[0086] when hour,

[0087]

[0088] when hour,

[0089]

[0090] In the formula, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, is the calculated positive sequence reactive current command of the converter, is the calculated negative-sequence reactive current command of the converter.

[0091] It is understandable that after the positive-sequence reactive current command and the negative-sequence reactive current command of the converter are calculated, the converter can inject reactive current that meets the grid guidelines into the PCC during the fault period under the control of the obtained positive-sequence reactive current command and the negative-sequence reactive current command, and the injected reactive current can also suppress the double frequency fluctuation of the active power output by the grid-side converter. The specific implementation method of how to determine the positive-sequence component and the negative-sequence component of the voltage at the grid connection point is not particularly limited in this application. Usually, a sampling module connected to the grid connection point is directly set to detect and sample the voltage condition of the grid connection point in real time.

[0092] Specifically, the corresponding relationship formula for calculating the positive-sequence reactive current command and the negative-sequence reactive current command of the converter can be determined directly according to the relationship between the voltage conditions of the determined grid-connected point and the preset comparison coefficient, so that the calculated positive-sequence reactive current command and negative-sequence reactive current command of the converter can meet the reactive current requirements of the grid guidelines, and at the same time can also suppress the double-frequency fluctuation of the active power output of the grid-side converter, further clarifying the specific method for calculating the positive-sequence reactive current command and the negative-sequence reactive current command of the converter.

[0093] As an optional embodiment, before determining the active current instruction of the converter based on the given active power of the wind turbine generator set and the active power limit value of the wind turbine generator set, the method further includes:

[0094] The active power limit value of the wind turbine is determined based on the voltage at the grid connection point and the maximum value of the permissible operating current of the converter.

[0095] It is not difficult to understand that the active power limit value of the wind turbine set is the limit value of the active power that can be output without damaging the converter. This value is mainly related to the current voltage of the grid connection point and the maximum value of the allowable operating current of the converter, and will affect the active current instruction of the converter. Therefore, the active power limit value of the wind turbine set can be determined by the voltage of the grid connection point and the maximum value of the allowable operating current of the converter. It fully considers whether the converter can provide the active power corresponding to the active current instruction, and avoids the situation where the active current instruction is too large, resulting in the converter being unable to control the wind turbine set to output the corresponding active power or even damaging the converter. The specific method of obtaining the maximum value of the allowable operating current of the converter is not particularly limited in this application, and can be determined according to the specific settings such as the capacity of the converter.

[0096] Specifically, the voltage condition in the entire power system is first determined based on the voltage at the grid connection point, and the maximum allowable operating current of the converter is determined based on the specific settings of the converter, thereby determining the active power limit of the wind turbine corresponding to the current working condition of the entire power system and the active power output of the wind turbine that the converter can withstand, thereby avoiding damage to the converter or difficulty in controlling the wind turbine to output the active power that accurately corresponds to the output, thereby ensuring the accurate implementation of the entire control process.

[0097] As an optional embodiment, before determining the active power limit value of the wind turbine generator set based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter, the method further includes:

[0098] Determine a positive-sequence voltage component and a negative-sequence voltage component of a grid connection point, and determine asymmetry of a grid voltage based on the positive-sequence voltage component and the negative-sequence voltage component of the grid connection point;

[0099] Correspondingly, the active power limit value of the wind turbine generator set is determined based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter, including:

[0100] The active power limit of the wind turbine is determined based on the voltage at the grid connection point, the asymmetry of the grid voltage and the maximum allowable operating current of the converter.

[0101] It is not difficult to understand that the active power limit of the wind turbine will also be affected by the asymmetry of the grid voltage. The asymmetry of the grid voltage can reflect the asymmetric fault of the entire power system to a certain extent, and it also has a certain impact on the active power output of the wind turbine. Therefore, when determining the active power limit of the wind turbine, the asymmetry of the grid voltage can also be taken into consideration, and the asymmetry of the grid voltage δ can be expressed by the relationship Calculate, where is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, so the asymmetry of the grid voltage can be calculated by sampling the voltage at the grid connection point.

[0102] Specifically, when determining the active power limit of a wind turbine, the asymmetry of the grid voltage may also be taken into consideration, further improving the factors that may affect the active power limit of the wind turbine, ensuring the accuracy and reliability of the active power limit of the wind turbine, thereby improving the safety and reliability of the entire control process, and facilitating the subsequent calculation of the active current command of the converter.

[0103] As an optional embodiment, determining the active power limit value of the wind turbine generator system based on the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter includes:

[0104] Determine the relationship between the active power limit value of the wind turbine generator set and the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter, and determine the active power limit value of the wind turbine generator set based on the relationship;

[0105] The relationship between the active power limit of the wind turbine and the voltage at the grid connection point, the asymmetry of the grid voltage and the maximum allowable operating current of the converter is as follows:

[0106]

[0107] Among them, P limit is the active power limit of the wind turbine, is the positive sequence component of the voltage at the grid connection point, δ is the asymmetry of the grid voltage, I g_max It is the maximum allowable operating current of the converter.

[0108] It is not difficult to understand that the active power limit value can be calculated according to the drop depth and asymmetry of the grid voltage during a fault, and the relationship between the active power limit value of the wind turbine and the voltage at the grid connection point, the asymmetry of the grid voltage and the maximum allowable operating current of the converter; the active power limit value of the wind turbine is the output active power limit value set to avoid excessive grid-side output current of the generator in the wind turbine and damage to the converter, and the positive sequence component of the voltage at the grid connection point can reflect the drop depth of the grid voltage.

[0109] Specifically, the active power limit value of the wind turbine can be effectively calculated by utilizing the relationship between the active power limit value of the wind turbine and the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum allowable operating current of the converter, which facilitates the subsequent accurate implementation of the process of determining the active current command of the converter, and further improves the process of how to determine the active current command of the converter.

[0110] As an optional embodiment, determining the active current instruction of the converter based on the given active power of the wind turbine generator set and the active power limit value of the wind turbine generator set includes:

[0111] When the given active power of the wind turbine generator set is greater than the active power limit value of the wind turbine generator set, determining the active current command of the converter based on the third relational expression;

[0112] When the given active power of the wind turbine generator set is less than the active power limit value of the wind turbine generator set, determining the active current command of the converter based on the fourth relational expression;

[0113] The third relation is:

[0114]

[0115] The fourth relationship is:

[0116]

[0117] in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, I g_max is the maximum allowable operating current of the converter, P ref is the given active power of the wind turbine, is the positive sequence active current command of the converter, It is the negative sequence active current command of the converter.

[0118] It should be noted that when the given active power of the wind turbine set is greater than the active power limit value of the wind turbine set calculated previously, it is necessary to calculate the active current command of the converter according to the third relationship; when the given active power of the wind turbine set is less than the active power limit value of the wind turbine set calculated previously, it is necessary to calculate the active current command of the converter according to the fourth relationship. The given active power of the wind turbine set is the given active power value of the generator in the wind turbine set set by the staff according to the target power required by the application during the application process.

[0119] Specifically, when the given active power of the wind turbine set and the active power limit value of the wind turbine set calculated previously are different in size, the calculation method of the active current command of the converter is also different. The specific calculation method of the active current command of the converter is clarified, and the entire control process is further improved.

[0120] As an optional embodiment, the converter includes a machine-side converter and a grid-side converter, one end of the machine-side converter is connected to the wind turbine set, and the other end is connected to one end of the grid-side converter, and the other end of the grid-side converter is connected to the grid through a grid connection point, and a reactive current command and an active current command are output to the converter to control the converter to realize asymmetric fault ride-through of the wind power generation system, including:

[0121] The reactive current command and the active current command are output to the current controller of the grid-side converter, so that the grid-side converter controls the wind turbine generator set based on the reactive current command and the active current command.

[0122] It is not difficult to understand that the converter in the wind power generation system includes the machine-side converter and the grid-side converter. The grid-side converter is the module in the converter close to the grid side, and the machine-side converter is the module in the converter close to the wind turbine side. The machine-side converter controls the frequency conversion speed regulation of the generator in the wind turbine, so that the power generation system can obtain the best power generation efficiency, and the grid-side converter is connected to the grid to provide high-quality power output; in the process of asymmetric fault riding, the grid-side converter mainly outputs current to the grid connection point to support the power recovery of the grid. Therefore, after determining the reactive current command and active current command of the converter, the reactive current command and active current command will be output to the current controller of the grid-side converter, such as Figure 3 As shown, the grid-side positive and negative sequence current controller module is the current controller of the grid-side converter. At this time, the current controller of the grid-side converter will control the current corresponding to the grid-side converter output according to the received reactive current command and active current command, thereby realizing asymmetric fault ride-through. At the same time, the control system of the machine-side converter is kept unchanged, which can suppress the double frequency fluctuation of the total output active power of the permanent magnet wind power generation system during the asymmetric fault process. Figure 3 As shown, the machine-side converter control module is the control system of the machine-side converter. Figure 3 The grid-side converter current command calculation module is a calculation module used to calculate the reactive current command and active current command of the converter. The specific setting methods of the machine-side converter and its control system and the grid-side converter and its current controller are not particularly limited in this application, and the control module of the original converter in the wind power generation system can be directly reused.

[0123] Specifically, the process of controlling the converter based on reactive current instructions and active current instructions to complete asymmetric fault riding is mainly a process in which the current controller of the grid-side converter controls the grid-side converter to provide current to the grid to achieve power recovery of the grid according to the received reactive current instructions and active current instructions, further improving the specific implementation of the entire asymmetric fault riding process.

[0124] As a specific embodiment, please refer to Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 and Fig. 9 , Figure 4 A schematic diagram of a first output signal waveform of a wind power generation system provided by the present invention; Figure 5 A schematic diagram of a second output signal waveform of a wind power generation system provided by the present invention; Figure 6 A schematic diagram of a third output signal waveform of a wind power generation system provided by the present invention; Figure 7 A schematic diagram of a fourth output signal waveform of a wind power generation system provided by the present invention; Figure 8 A schematic diagram of a fifth output signal waveform of a wind power generation system provided by the present invention; Fig. 9 A schematic diagram of a sixth output signal waveform of a wind power generation system provided by the present invention; Figure 4 , Figure 5 and Figure 6 The simulation waveform of the permanent magnet wind power generation system using the traditional control strategy is given when the voltage unbalance degree of the grid connection point is 36% and the voltage positive sequence component drops to 0.73pu after a two-phase short circuit fault. Figure 7 , Figure 8 and Fig. 9 The simulation waveform diagram of the permanent magnet wind power generation system when the control method provided by the present invention is adopted is given when the voltage unbalance degree of the grid connection point is 36% and the voltage positive sequence component drops to 0.73pu after a two-phase short circuit fault. The traditional control strategy directly outputs only positive and negative sequence reactive currents that meet the grid guidelines when an asymmetric fault occurs. Figure 4 and Figure 7 The waveform diagram shows the change of Pg over time. Pg is the total output active power of the grid-side converter of the wind power generation system. Figure 5 and Figure 8 Indicates i+ gd+ and i + gq+ Waveform graph changing over time, i + gd+ and i + gq+ is the positive sequence dq axis component of the current of the grid-side converter of the wind power generation system, Figure 6 and Fig. 9 Indicates i - gd- and i - gq- Waveform graph changing over time, i - gd- and i - gq- is the negative sequence dq axis component of the current of the grid-side converter of the wind power generation system. The time period of 1.5s-2.5s in the figure is the time when the grid fault occurs. By comparing the waveforms in the two cases, it is not difficult to find that Figure 4 , Figure 5 and Figure 6 This is the simulation waveform diagram when using the traditional control strategy. When an asymmetric fault occurs in the power grid, the total output active power of the grid-side converter exhibits severe double-frequency fluctuations, which seriously affects the grid-connected power quality of the system. Figure 7 , Figure 8 and Fig. 9 The simulation waveform diagram when the control strategy provided by the present invention is adopted, in the case of asymmetric fault of the grid voltage, while ensuring the output reactive current that meets the requirements of the grid guidelines, the double frequency fluctuation of the active power output of the grid-side converter is effectively suppressed by reasonably matching the positive and negative sequence dq axis current components of the grid-side converter, wherein the positive sequence reactive current is greater than the reactive current required by the grid guidelines, providing more reactive support and improving the transient level of the grid voltage during the fault. Obviously Figure 8 The double frequency fluctuation of the total output active power of the grid-side converter is effectively suppressed. In addition, on the basis of fully considering the converter capacity and the operating conditions of the unit, a certain active power is also provided to the power grid.

[0125] Therefore, the control strategy provided by the present application can effectively suppress the double frequency fluctuation of the total output active power of the permanent magnet wind power generation system, and improve the fault ride-through capability of the wind farm and the grid-connected power quality of the system. The asymmetric fault ride-through method for improving the power quality of the permanent magnet wind power system provided by the present invention can ensure the stable operation of the permanent magnet wind power generation system when an asymmetric fault occurs in the power grid. In the case of an asymmetric fault in the power grid, while ensuring the output of the reactive current that meets the requirements of the power grid guidelines, it effectively solves the problem of double frequency fluctuation of the active power output of the grid-side converter during the fault, and improves the grid-connected power quality of the system; the output positive sequence reactive current is greater than the reactive current required by the power grid guidelines, which improves the transient level of the grid voltage during the fault. On the basis of fully considering the converter capacity and the operating conditions of the unit, it also provides a certain active power support for the power grid during the fault.

[0126] Please refer to Fig.10 , Fig.10 A schematic diagram of the structure of a control system for asymmetric fault ride-through provided by the present invention; To solve the above technical problems, the present invention further provides a control system for asymmetric fault ride-through, which is applied to a control system of a wind power generation system, wherein the wind power generation system is connected to a power grid, and the connection point with the power grid is a grid connection point, the wind power generation system further comprises a wind turbine and a converter, one end of the converter is connected to the power grid through the grid connection point, and the other end is connected to the wind turbine, and the control system is connected to the converter and the power grid respectively; the control system for asymmetric fault ride-through comprises:

[0127] A reactive current command determination unit 11, used to determine the reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, wherein the preset comparison coefficient is related to the reactive current required by the grid guidelines and the double frequency fluctuation of the active power output by the converter;

[0128] An active current command determination unit 12 is used to determine an active current command of the converter based on a given active power of the wind turbine and an active power limit value of the wind turbine, wherein the active power limit value of the wind turbine is a limit value of the active power that can be output without damaging the converter;

[0129] The command output unit 13 is used to output the reactive current command and the active current command to the converter, so as to control the converter to achieve asymmetric fault ride-through of the wind power generation system.

[0130] As an optional embodiment, the preset comparison coefficient is the comparison coefficient of the voltage positive sequence component of the grid connection point, and the reactive current instruction determination unit 11 includes:

[0131] A voltage determination unit, used for determining a voltage positive sequence component and a voltage negative sequence component at a grid connection point;

[0132] A first calculation unit, configured to determine a reactive current command of the converter based on a first relational expression when a voltage positive sequence component of the grid connection point is greater than a comparison coefficient of the voltage positive sequence component of the grid connection point;

[0133] The second calculation unit is used to determine the reactive current instruction of the converter based on the second relationship when the voltage positive sequence component of the grid-connected point is less than the comparison coefficient of the voltage positive sequence component of the grid-connected point.

[0134] As an optional embodiment, it also includes:

[0135] The active power limit value determination unit is used to determine the active power limit value of the wind turbine generator set based on the voltage of the grid connection point and the maximum value of the allowed operating current of the converter.

[0136] As an optional embodiment, it also includes:

[0137] an asymmetry determination unit, used to determine a voltage positive sequence component and a voltage negative sequence component at a grid connection point, and determine an asymmetry of a grid voltage based on the voltage positive sequence component and the voltage negative sequence component at the grid connection point;

[0138] Correspondingly, the active power limit value determining unit includes:

[0139] The active power limit value determination subunit is used to determine the active power limit value of the wind turbine generator set based on the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter.

[0140] As an optional embodiment, the active power limit value determination subunit includes:

[0141] The relationship determination unit is used to determine the relationship between the active power limit value of the wind turbine set and the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum allowable operating current of the converter, and determine the active power limit value of the wind turbine set based on the relationship.

[0142] As an optional embodiment, the active current command determining unit 12 includes:

[0143] A third calculation unit, configured to determine an active current command of the converter based on a third relationship when the given active power of the wind turbine generator set is greater than the active power limit value of the wind turbine generator set;

[0144] The fourth calculation unit is used to determine the active current command of the converter based on a fourth relationship when the given active power of the wind turbine generator set is less than the active power limit value of the wind turbine generator set.

[0145] As an optional embodiment, the converter includes a machine-side converter and a grid-side converter, one end of the machine-side converter is connected to the wind turbine generator set, and the other end is connected to one end of the grid-side converter, and the other end of the grid-side converter is connected to the grid through a grid connection point, and the instruction output unit 13 includes:

[0146] The command output subunit is used to output the reactive current command and the active current command to the current controller of the grid-side converter, so that the grid-side converter controls the wind turbine generator set based on the reactive current command and the active current command.

[0147] For an introduction to a control system for asymmetric fault ride-through provided by the present invention, please refer to the above-mentioned embodiment of the control method for asymmetric fault ride-through, and the present invention will not be described in detail here.

[0148] Please refer to Fig.11 , Fig.11 The present invention provides a schematic diagram of the structure of an electronic device. To solve the above technical problems, the present invention also provides an electronic device, including:

[0149] A memory 21, used for storing computer programs;

[0150] The processor 22 is used to implement the steps of the control method for asymmetric fault ride-through as described above.

[0151] Among them, the processor 22 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 22 can be implemented in at least one hardware form of DSP (Digital Signal Processor), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array). The processor 22 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the awake state, also known as a central processing unit; the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 22 may integrate a GPU (graphics processing unit), which is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 22 may also include an AI (Artificial Intelligence) processor, which is used to process computing operations related to machine learning.

[0152] The memory 21 may include one or more computer-readable storage media, which may be non-transitory. The memory 21 may also include a high-speed random access memory, and a non-volatile memory, such as one or more disk storage devices, flash memory storage devices. In this embodiment, the memory 21 is at least used to store the following computer program, wherein, after the computer program is loaded and executed by the processor 22, the relevant steps of the control method for asymmetric fault crossing disclosed in any of the aforementioned embodiments can be implemented. In addition, the resources stored in the memory 21 may also include an operating system and data, etc., and the storage method may be temporary storage or permanent storage. Among them, the operating system may include Windows, Unix, Linux, etc. The data may include, but is not limited to, data of the control method for asymmetric fault crossing, etc.

[0153] In some embodiments, the electronic device may further include a display screen, an input and output interface, a communication interface, a power supply, and a communication bus.

[0154] It can be understood by those skilled in the art that Fig.11 The structure shown in the figure does not constitute a limitation on the electronic device, and may include more or fewer components than shown in the figure.

[0155] For an introduction to an electronic device provided by the present invention, please refer to the above-mentioned embodiment of the control method for asymmetric fault ride-through, and the present invention will not be described in detail here.

[0156] In order to solve the above technical problems, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the control method for asymmetric fault crossing as described above are implemented.

[0157] It is understandable that if the method in the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium to execute all or part of the steps of the method described in each embodiment of the present application. Specifically, the computer-readable storage medium may include but is not limited to any type of disk, including a floppy disk, an optical disk, and a mobile hard disk, or any type of medium or device suitable for storing instructions, data, etc., and the present application does not make any special restrictions here.

[0158] For an introduction to a computer-readable storage medium provided by the present invention, please refer to the above-mentioned embodiment of the control method for asymmetric fault ride-through, and the present invention will not be described in detail here.

[0159] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0160] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0161] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for asymmetric fault ride-through, characterized in that: A control system applied to a wind power generation system, wherein the wind power generation system is connected to a power grid, and the connection point with the power grid is a grid connection point, the wind power generation system further comprises a wind turbine and a converter, one end of the converter is connected to the power grid via the grid connection point, and the other end is connected to the wind turbine, and the control system is connected to the converter and the power grid respectively; The control method of asymmetric fault ride-through includes: Determining a reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, wherein the preset comparison coefficient is related to the reactive current required by the grid guidelines and the double frequency fluctuation of the active power output by the converter; Determining an active current instruction of the converter based on a given active power of the wind turbine generator set and an active power limit value of the wind turbine generator set, wherein the active power limit value of the wind turbine generator set is a limit value of the active power that can be output without damaging the converter; Outputting the reactive current command and the active current command to the converter to control the converter to achieve asymmetric fault ride-through of the wind power generation system; The preset comparison coefficient is a comparison coefficient of the voltage positive sequence component of the grid connection point, and the step of determining the reactive current instruction of the converter based on the voltage of the grid connection point and the preset comparison coefficient includes: Determining a voltage positive sequence component and a voltage negative sequence component at the grid connection point; When the voltage positive sequence component of the grid connection point is greater than the comparison coefficient of the voltage positive sequence component of the grid connection point, determining the reactive current command of the converter based on the first relational expression; When the voltage positive sequence component of the grid connection point is less than the comparison coefficient of the voltage positive sequence component of the grid connection point, determining the reactive current command of the converter based on a second relational expression; The first relation is: The second relation is: in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, is the positive sequence reactive current command of the converter, is the negative sequence reactive current command of the converter; The determining the active current instruction of the converter based on the given active power of the wind turbine generator set and the active power limit value of the wind turbine generator set comprises: When the given active power of the wind turbine generator set is greater than the active power limit value of the wind turbine generator set, determining the active current command of the converter based on a third relational expression; When the given active power of the wind turbine generator set is less than the active power limit value of the wind turbine generator set, determining the active current command of the converter based on a fourth relational expression; The third relational expression is: The fourth relational expression is: in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, I g_max is the maximum value of the permissible operating current of the converter, P ref is the given active power of the wind turbine generator set, is the positive sequence active current command of the converter, is the negative-sequence active current instruction of the converter.

2. The control method for asymmetric fault ride-through according to claim 1, characterized in that: Before determining the active current instruction of the converter based on the given active power of the wind turbine generator set and the active power limit value of the wind turbine generator set, the method further includes: The active power limit value of the wind turbine generator set is determined based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter.

3. The control method for asymmetric fault ride-through according to claim 2, characterized in that: Before determining the active power limit value of the wind turbine generator set based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter, the method further includes: Determine the voltage positive sequence component and the voltage negative sequence component of the grid connection point, and determine the asymmetry of the grid voltage based on the voltage positive sequence component and the voltage negative sequence component of the grid connection point; Correspondingly, the determining of the active power limit value of the wind turbine generator set based on the voltage of the grid connection point and the maximum value of the allowable operating current of the converter includes: The active power limit value of the wind turbine generator set is determined based on the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter.

4. The control method for asymmetric fault ride-through according to claim 3, characterized in that: The determining of the active power limit value of the wind turbine generator set based on the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter comprises: Determine a relationship between the active power limit value of the wind turbine generator set and the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter, and determine the active power limit value of the wind turbine generator set based on the relationship; The relationship between the active power limit value of the wind turbine generator set, the voltage of the grid connection point, the asymmetry of the grid voltage and the maximum value of the allowable operating current of the converter is: Among them, P limit is the active power limit value of the wind turbine generator set, is the positive sequence component of the voltage at the grid connection point, δ is the asymmetry of the grid voltage, I g_max is the maximum value of the allowable operating current of the converter.

5. The control method for asymmetric fault ride-through according to any one of claims 1 to 4, characterized in that: The converter includes a machine-side converter and a grid-side converter, one end of the machine-side converter is connected to the wind turbine set, and the other end is connected to one end of the grid-side converter, and the other end of the grid-side converter is connected to the power grid through the grid connection point, and the reactive current instruction and the active current instruction are output to the converter to control the converter to realize the asymmetric fault ride-through of the wind power generation system, including: The reactive current command and the active current command are output to a current controller of the grid-side converter, so that the grid-side converter controls the wind turbine generator set based on the reactive current command and the active current command.

6. A control system for asymmetric fault ride-through, characterized in that: A control system applied to a wind power generation system, wherein the wind power generation system is connected to a power grid, and the connection point with the power grid is a grid connection point, the wind power generation system further comprises a wind turbine and a converter, one end of the converter is connected to the power grid via the grid connection point, and the other end is connected to the wind turbine, and the control system is connected to the converter and the power grid respectively; The control system of the asymmetric fault ride-through includes: A reactive current command determination unit, configured to determine a reactive current command of the converter based on the voltage of the grid connection point and a preset comparison coefficient, wherein the preset comparison coefficient is related to the reactive current required by the grid code and the double frequency fluctuation of the active power output by the converter; An active current instruction determination unit, configured to determine an active current instruction of the converter based on a given active power of the wind turbine set and an active power limit value of the wind turbine set, wherein the active power limit value of the wind turbine set is a limit value of the active power that can be output without damaging the converter; An instruction output unit, used for outputting the reactive current instruction and the active current instruction to the converter, so as to control the converter to realize asymmetric fault ride-through of the wind power generation system; The preset comparison coefficient is a comparison coefficient of the voltage positive sequence component of the grid connection point, and the reactive current instruction determination unit includes: A voltage determination unit, used to determine a voltage positive sequence component and a voltage negative sequence component of the grid connection point; A first calculation unit, configured to determine a reactive current command of the converter based on a first relational expression when a voltage positive sequence component of the grid-connected point is greater than a comparison coefficient of a voltage positive sequence component of the grid-connected point; a second calculation unit, configured to determine a reactive current command of the converter based on a second relational expression when the voltage positive sequence component of the grid-connected point is less than a comparison coefficient of the voltage positive sequence component of the grid-connected point; The first relation is: The second relation is: in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, is the positive sequence reactive current command of the converter, is the negative sequence reactive current command of the converter; The active current instruction determining unit comprises: a third calculation unit, configured to determine an active current command of the converter based on a third relationship when the given active power of the wind turbine generator set is greater than the active power limit value of the wind turbine generator set; a fourth calculation unit, configured to determine an active current command of the converter based on a fourth relationship when the given active power of the wind turbine generator set is less than the active power limit value of the wind turbine generator set; The third relational expression is: The fourth relational expression is: in, is the positive sequence component of the voltage at the grid connection point, is the negative sequence component of the voltage at the grid connection point, I g_max is the maximum value of the permissible operating current of the converter, P ref is the given active power of the wind turbine generator set, is the positive sequence active current command of the converter, is the negative-sequence active current instruction of the converter.

7. An electronic device, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the asymmetric fault ride-through control method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the control method for asymmetric fault ride-through according to any one of claims 1 to 5 are implemented.

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