Converter system control method and device of wind generating set, controller and medium

Abstract

The invention discloses a converter system control method and device of a wind generating set, a controller and a medium, and belongs to the field of wind power generation. The method comprises the following steps: acquiring a d-axis voltage negative-sequence component and a q-axis voltage negative-sequence component of an alternating current output end voltage of an inverter in a converter system under a two-phase rotating coordinate system; based on the d-axis voltage negative-sequence component, the q-axis voltage negative-sequence component, a given d-axis voltage negative-sequence target value and a q-axis voltage negative-sequence target value, a d-axis voltage negative-sequence reference value and a q-axis voltage negative-sequence reference value are obtained, and the d-axis voltage negative-sequence target value and the q-axis voltage negative-sequence target value are 0; converting the d-axis voltage negative sequence reference value and the q-axis voltage negative sequence reference value into a three-phase voltage negative sequence component target value under a three-phase static coordinate system; and controlling the inverter according to the three-phase voltage negative-sequence component target value and the obtained three-phase voltage positive-sequence component target value. According to the embodiment of the invention, the safety of the weak system comprising the AC current collection circuit can be improved.

Description

Technical Field

[0001] This application belongs to the field of wind power generation, and particularly relates to a control method, device, controller and medium for a variable frequency conversion system of a wind turbine generator set. Background Art

[0002] Under the background of low-carbon environmental protection, renewable resources such as wind power generation have been vigorously promoted and used. Wind power generation technology can convert wind energy into electrical energy. Large-scale wind power can be transmitted through a high-voltage direct current transmission system or an alternating current power grid. As the source end, the wind turbine generator set is connected to the wind farm alternating current collector line, and the alternating current collector line is electrically connected to the collecting station. The alternating current electrical energy generated by the wind turbine generator set is sent out over a long distance through the collecting station. Since wind turbine generator sets are generally installed in areas with rich wind resources, and areas with rich wind resources are often remote, the variable frequency conversion system composed of the wind turbine generator set and the wind farm alternating current collector line is very far from the backbone grid of the power grid, and the impedance of the transmission line between the variable frequency conversion system and the power grid is also large. As a result, the wind power transmission system where the variable frequency conversion system is located has become a weak system with low strength and weak anti-interference ability.

[0003] When faults such as single-phase short circuit or two-phase short circuit occur, relay protection will be triggered, that is, the faulty single phase or two phases will be disconnected through a circuit breaker, resulting in the wind power transmission system where the variable frequency conversion system is located being in an unbalanced operation state. The unbalanced operation state will have greater safety risks, thus bringing potential safety hazards. Summary of the Invention

[0004] Embodiments of this application provide a control method, device, controller and medium for a variable frequency conversion system of a wind turbine generator set, which can improve the safety of a weak system including a wind farm alternating current collector line.

[0005] In a first aspect, embodiments of this application provide a control method for a variable frequency conversion system of a wind turbine generator set. The variable frequency conversion system includes a rectifier and an inverter electrically connected in the wind turbine generator set, and the inverter is connected to the alternating current collector line. The method includes: obtaining the d-axis voltage negative sequence component and the q-axis voltage negative sequence component of the alternating current output terminal voltage of the inverter in a two-phase rotating coordinate system; based on the d-axis voltage negative sequence component, the q-axis voltage negative sequence component, the given d-axis voltage negative sequence target value and the q-axis voltage negative sequence target value, obtaining a d-axis voltage negative sequence reference value and a q-axis voltage negative sequence reference value, where the d-axis voltage negative sequence target value and the q-axis voltage negative sequence target value are 0; transforming the d-axis voltage negative sequence reference value and the q-axis voltage negative sequence reference value into a three-phase voltage negative sequence component target value in a three-phase stationary coordinate system; and controlling the inverter according to the three-phase voltage negative sequence component target value and the obtained three-phase voltage positive sequence component target value.

[0006] In some possible embodiments, based on the negative sequence component of the d-axis voltage, the negative sequence component of the q-axis voltage, the given target value of the negative sequence component of the d-axis voltage, and the given target voltage of the negative sequence component of the q-axis voltage, obtaining the reference value of the negative sequence component of the d-axis voltage and the reference value of the negative sequence component of the q-axis voltage includes: obtaining a first difference between the target value of the negative sequence component of the d-axis voltage and the negative sequence component of the d-axis voltage, and a second difference between the target value of the negative sequence component of the q-axis voltage and the negative sequence component of the q-axis voltage; respectively inputting the first difference and the second difference into a proportional-integral controller to obtain the output reference value of the negative sequence component of the d-axis voltage and the reference value of the negative sequence component of the q-axis voltage.

[0007] In some possible embodiments, the method further includes: performing a clipping process on the reference value of the negative sequence component of the d-axis voltage and the reference value of the negative sequence component of the q-axis voltage.

[0008] In some possible embodiments, obtaining the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in a two-phase rotating coordinate system includes: obtaining the negative sequence components of the three-phase voltages of the AC output terminal voltage of the inverter; transforming the negative sequence components of the three-phase voltages into a first negative sequence component and a second negative sequence component in a two-phase plane rectangular coordinate system; transforming the first negative sequence component and the second negative sequence component into the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage in a two-phase rotating coordinate system.

[0009] In some possible embodiments, transforming the reference value of the negative sequence component of the d-axis voltage and the reference value of the negative sequence component of the q-axis voltage into the target values of the negative sequence components of the three-phase voltages in a three-phase stationary coordinate system includes: transforming the reference value of the negative sequence component of the d-axis voltage and the reference value of the negative sequence component of the q-axis voltage into a third negative sequence component and a fourth negative sequence component in a two-phase plane rectangular coordinate system; transforming the third negative sequence component and the fourth negative sequence component into the target values of the negative sequence components of the three-phase voltages in a three-phase stationary coordinate system.

[0010] In some possible embodiments, controlling the inverter according to the target values of the negative sequence components of the three-phase voltages and the obtained target values of the positive sequence components of the three-phase voltages includes: superimposing the target values of the negative sequence components of the three-phase voltages to the target values of the positive sequence components of the three-phase voltages to obtain a space vector voltage; generating a control signal according to the space vector voltage to control the inverter.

[0011] In some possible embodiments, obtaining the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in a two-phase rotating coordinate system includes: in the case where a three-phase voltage imbalance occurs in the detected AC collector line, obtaining the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in a two-phase rotating coordinate system.

[0012] Second aspect, an embodiment of the present application provides a control device for a variable frequency conversion system of a wind turbine generator. The variable frequency conversion system includes a rectifier and an inverter electrically connected in the wind turbine generator, and the inverter is connected to an AC collector line. The device includes: an acquisition module configured to acquire the d-axis voltage negative sequence component and the q-axis voltage negative sequence component of the voltage at the AC output terminal of the inverter in a two-phase rotating coordinate system; a processing module configured to obtain a d-axis voltage negative sequence reference value and a q-axis voltage negative sequence reference value based on the d-axis voltage negative sequence component, the q-axis voltage negative sequence component, a given d-axis voltage negative sequence target value, and a q-axis voltage negative sequence target value, where the d-axis voltage negative sequence target value and the q-axis voltage negative sequence target value are 0; a transformation module configured to transform the d-axis voltage negative sequence reference value and the q-axis voltage negative sequence reference value into a three-phase voltage negative sequence component target value in a three-phase stationary coordinate system; and a control module configured to control the inverter according to the three-phase voltage negative sequence component target value and the acquired three-phase voltage positive sequence component target value.

[0013] In some possible embodiments, the processing module is configured to: acquire a first difference between the d-axis voltage negative sequence target value and the d-axis voltage negative sequence component, and a second difference between the q-axis voltage negative sequence target value and the q-axis voltage negative sequence component; input the first difference and the second difference into a proportional-integral controller respectively to obtain the output d-axis voltage negative sequence reference value and q-axis voltage negative sequence reference value.

[0014] In some possible embodiments, the processing module is further configured to: perform a clipping process on the d-axis voltage negative sequence reference value and the q-axis voltage negative sequence reference value.

[0015] In some possible embodiments, the acquisition module is configured to: acquire the three-phase voltage negative sequence component of the voltage at the AC output terminal of the inverter; transform the three-phase voltage negative sequence component into a first voltage negative sequence component and a second voltage negative sequence component in a two-phase plane rectangular coordinate system; and transform the first voltage negative sequence component and the second voltage negative sequence component into the d-axis voltage negative sequence component and the q-axis voltage negative sequence component in a two-phase rotating coordinate system.

[0016] In some possible embodiments, the transformation module is configured to: transform the d-axis voltage negative sequence reference value and the q-axis voltage negative sequence reference value into a third voltage negative sequence component and a fourth voltage negative sequence component in a two-phase plane rectangular coordinate system; and transform the third voltage negative sequence component and the fourth voltage negative sequence component into a three-phase voltage negative sequence component target value in a three-phase stationary coordinate system.

[0017] In some possible embodiments, the control module is configured to: superimpose the three-phase voltage negative sequence component target value on the three-phase voltage positive sequence component target value to obtain a space vector voltage; and generate a control signal according to the space vector voltage to control the inverter.

[0018] In some possible embodiments, the acquisition module is configured to: when detecting that the three-phase voltage of the AC collector line is unbalanced, acquire the negative-sequence component of the d-axis voltage and the negative-sequence component of the q-axis voltage of the voltage at the AC output terminal of the inverter in a two-phase rotating coordinate system.

[0019] In a third aspect, an embodiment of the present application provides a converter controller for a wind turbine generator, including: a processor and a memory storing computer program instructions; when the processor executes the computer program instructions, the control method for the converter system of the wind turbine generator in the first aspect is implemented.

[0020] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, on which computer program instructions are stored, and when the computer program instructions are executed by a processor, the control method for the converter system of the wind turbine generator in the first aspect is implemented.

[0021] The embodiment of the present application provides a control method, device, controller and medium for the converter system of a wind turbine generator, which can obtain the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage according to the negative-sequence component of the d-axis voltage and the negative-sequence component of the q-axis voltage of the voltage at the AC output terminal of the inverter in the wind turbine generator, as well as the negative-sequence target value of the d-axis voltage and the negative-sequence target value of the q-axis voltage that are 0. Convert the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage into the target value of the three-phase voltage negative-sequence component in the three-phase stationary coordinate system, and this target value of the three-phase voltage negative-sequence component can compensate for the unstable phenomenon caused by the three-phase voltage imbalance. Use this target value of the three-phase voltage negative-sequence component to compensate the target value of the three-phase voltage positive-sequence component, control the inverter in the wind turbine generator, reduce or even eliminate the three-phase voltage imbalance, so that the inverter outputs AC electric energy with a higher degree of three-phase voltage balance, making the three-phase voltage of the AC electric energy output by the AC collector line more stable, avoiding the phenomena of voltage oscillation and transient overvoltage, and thus improving the safety of the weak system including the AC collector line of the wind farm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0023] Figure 1 FIG. 18 is a schematic structural diagram of an example of a high-voltage DC power transmission system in the related art;

[0024] Figure 2 FIG. 22 is a schematic structural diagram of an example of a wind turbine generator provided by an embodiment of the present application;

[0025] Figure 3 Flow chart of a control method for a variable frequency conversion system of a wind turbine provided by an embodiment of the present application;

[0026] Figure 4 Flow chart of a control method for a variable frequency conversion system of a wind turbine provided by another embodiment of the present application;

[0027] Figure 5 Logic schematic diagram of an example of a control method for a variable frequency conversion system of a wind turbine provided by an embodiment of the present application;

[0028] Figure 6 Structural schematic diagram of a control device for a variable frequency conversion system of a wind turbine provided by an embodiment of the present application;

[0029] Figure 7 Structural schematic diagram of a variable frequency converter of a wind turbine provided by an embodiment of the present application. Detailed implementation manners

[0030] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0031] In the context of low-carbon environmental protection, renewable resources such as wind power have been vigorously promoted and used. Wind power generation technology can convert wind energy into electrical energy. Large-scale wind power can be transmitted through a high-voltage direct current transmission system or an alternating current power grid. For example, Figure 1 Structural schematic diagram of an example of a power transmission system of a wind farm in the prior art. The power transmission system of the wind farm includes at least one wind turbine 111, an alternating current collector line 11, a transformer 12, a collection station 13, and a transmission line 2. Among them, the transmission line 2 can be a high-voltage direct current transmission line or an alternating current transmission line. Among them, the wind turbine 111 feeds the alternating current electrical energy output by it into the alternating current collector line 11. The alternating current collector line 11 is connected to the transmission line 2 via the transformer 12 and the collection station 13, and then provides electrical energy to an electrical load or transmits it to the power grid.

[0032] Since wind turbines are generally installed in areas with rich wind resources, and such areas are often remote, the distance between the converter system composed of wind turbines and the AC collector line of the wind farm and the backbone grid of the power grid is very far, and the impedance of the transmission line between the converter system and the power grid is also large. As a result, the wind power transmission system where the converter system is located has become a weak system with low strength and weak anti-interference ability. When a single-phase short circuit or two-phase short circuit occurs in the AC collector line, it will trigger relay protection, that is, the faulty single phase or two phases will be disconnected through the circuit breaker, resulting in the wind power transmission system where the converter system is located being in an unbalanced three-phase operation state.

[0033] In this embodiment, a weak system is defined as a power grid scenario where the short-circuit ratio (SCR) is less than 2. In the embodiment of the present application, the line between the transformer 12 and the collection station 13 is a single-circuit AC line, usually 220 KV or 110 KV.

[0034] When the wind power transmission system where the converter system is located is in an unbalanced three-phase operation state, the output voltage of the AC collector line is unbalanced, and the impedance of the AC relay line is also unbalanced, which will cause severe voltage oscillation. When the voltage oscillation amplitude is too large, there will also be a problem of transient overvoltage, making the safety and stability of the weak system including the AC collector line relatively poor. In some cases, in the face of voltage oscillation in the unbalanced three-phase operation state, the wind turbine will perform high-voltage ride-through or low-voltage ride-through according to the voltage oscillation situation, and there will be a situation where high-voltage ride-through and low-voltage ride-through are executed alternately, which will further exacerbate the voltage oscillation and bring greater potential safety hazards.

[0035] The present application provides a control method, device, controller and medium for the converter system of a wind turbine, which can obtain the d-axis voltage negative-sequence component and q-axis voltage negative-sequence component of the AC output terminal voltage of the inverter in the two-phase rotating coordinate system of the wind turbine, as well as the d-axis voltage negative-sequence target value and q-axis voltage negative-sequence target value that are 0, to obtain the d-axis voltage negative-sequence reference value and q-axis voltage negative-sequence reference value. The d-axis voltage negative-sequence reference value and q-axis voltage negative-sequence reference value are converted into the three-phase voltage negative-sequence component target value in the three-phase static coordinate system. This three-phase voltage negative-sequence component target value can improve the unstable phenomenon caused by three-phase voltage imbalance, and jointly control the inverter in the wind turbine with the three-phase voltage positive-sequence component target value, so that the inverter outputs AC electric energy with a higher degree of three-phase voltage balance. When the inverter outputs AC electric energy with a higher degree of three-phase voltage balance, the three-phase voltage of the AC electric energy output by the AC collector line is relatively more stable, avoiding voltage oscillation and transient overvoltage phenomena, thereby improving the stability and safety of the weak system including the AC collection system.

[0036] The control method, device, controller and medium for the variable frequency conversion system of a wind turbine provided by this application can be applied to the variable frequency conversion system of a wind turbine. The variable frequency conversion system can include multiple wind turbines. The wind turbine can include a grid-forming wind turbine or a grid-following wind turbine. In some examples, the wind farm can also include other new energy power generation devices, such as photovoltaic power generation devices. For the convenience of understanding, the structure of the wind turbine will be briefly introduced here. Figure 2 It is a schematic structural diagram of an example of a wind turbine provided by an embodiment of this application, as Figure 2 shown, the wind turbine 20 can include a generator 21 and a converter 22. The generator 21 is electrically connected to the converter 22. The converter 22 can include a rectifier 221 and an inverter 222 that are electrically connected. The rectifier 221 and the inverter 222 are connected through a DC bus. The control method for the variable frequency conversion system of the wind turbine in the embodiment of this application mainly controls the inverter 222.

[0037] The control method, device, controller and medium for the variable frequency conversion system of the wind turbine provided by this application will be described separately below.

[0038] The first solution of this application provides a control method for the variable frequency conversion system of a wind turbine, which is applied to the variable frequency conversion system. The variable frequency conversion system includes a rectifier and an inverter that are electrically connected in the wind turbine. For the specific content of the rectifier and the inverter, please refer to the above content and will not be elaborated here. Figure 3 It is a flowchart of the control method for the variable frequency conversion system of a wind turbine provided by an embodiment of this application, as Figure 3 shown, the control method for the variable frequency conversion system of the wind turbine can include steps S301 to S304.

[0039] In step S301, obtain the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the voltage at the AC output terminal of the inverter in the two-phase rotating coordinate system.

[0040] The voltage at the AC output terminal of the inverter can be collected, and the AC output terminal voltage is decomposed into the positive sequence component of the three-phase voltage and the negative sequence component of the three-phase voltage. The negative sequence component of the three-phase voltage is transformed into the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage in the two-phase rotating coordinate system.

[0041] In some examples, the negative-sequence components of the three-phase voltages at the AC output terminal of the inverter can be obtained; the negative-sequence components of the three-phase voltages are transformed into a first voltage negative-sequence component and a second voltage negative-sequence component in a two-phase plane rectangular coordinate system; the first voltage negative-sequence component and the second voltage negative-sequence component are transformed into a d-axis voltage negative-sequence component and a q-axis voltage negative-sequence component in a two-phase rotating coordinate system. Specifically, through the Clark transformation, the negative-sequence components of the three-phase voltages can be transformed into a first voltage negative-sequence component and a second voltage negative-sequence component in a two-phase plane rectangular coordinate system. Among them, the first voltage negative-sequence component can be the negative-sequence component of the α-axis voltage obtained by transformation, and the second voltage negative-sequence component can be the negative-sequence component of the β-axis voltage obtained by transformation. Then, through the Park transformation, the first voltage negative-sequence component and the second voltage negative-sequence component are transformed into a d-axis voltage negative-sequence component and a q-axis voltage negative-sequence component in a two-phase rotating coordinate system.

[0042] In step S302, based on the d-axis voltage negative-sequence component, the q-axis voltage negative-sequence component, the given d-axis voltage negative-sequence target value, and the q-axis voltage negative-sequence target value, a d-axis voltage negative-sequence reference value and a q-axis voltage negative-sequence reference value are obtained.

[0043] The d-axis voltage negative-sequence target value is the negative-sequence component of the voltage on the d-axis in the desired two-phase rotating coordinate system, and the q-axis voltage negative-sequence target value is the negative-sequence component of the voltage on the q-axis in the desired two-phase rotating coordinate system. To solve the problem of three-phase voltage imbalance, it is desired that the negative-sequence components of the voltage on the d-axis and the q-axis in the two-phase rotating coordinate system are 0. Correspondingly, the d-axis voltage negative-sequence target value and the q-axis voltage negative-sequence target value are preset to 0. The d-axis voltage negative-sequence reference value can be obtained based on the d-axis voltage negative-sequence component and the d-axis voltage negative-sequence target value of 0; the q-axis voltage negative-sequence reference value can be obtained based on the q-axis voltage negative-sequence component and the q-axis voltage negative-sequence target value of 0. The d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value are the reference values of the negative-sequence voltages corresponding to the d-axis and the q-axis in the two-phase rotating coordinate system required for inverter control.

[0044] In step S303, the d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value are transformed into the target values of the negative-sequence components of the three-phase voltages in a three-phase stationary coordinate system.

[0045] The d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value are the reference values of the negative-sequence voltages on the d-axis and the q-axis in the negative-sequence coordinate system. For the convenience of subsequent control, the d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value can be transformed into the target values of the negative-sequence components of the three-phase voltages in a three-phase stationary coordinate system. The target values of the negative-sequence components of the three-phase voltages can be the negative-sequence components of the three-phase voltages for compensating the three-phase voltage imbalance situation in a three-phase stationary coordinate system.

[0046] In step S304, the inverter is controlled according to the target value of the negative-sequence component of the three-phase voltage and the obtained target value of the positive-sequence component of the three-phase voltage.

[0047] The target value of the positive-sequence component of the three-phase voltage is the desired positive-sequence component value of the voltage in the three-phase stationary coordinate system. The target value of the positive-sequence component of the three-phase voltage can be compensated by using the compensation effect of the target value of the negative-sequence component of the three-phase voltage on the unbalance of the three-phase voltage, so as to generate a control signal, and the inverter is controlled by using the control signal. The inverter includes a plurality of switching devices, and the switching devices in the inverter can be controlled by the control signal, so as to realize the control of the inverter and improve the balance degree of the three-phase voltage at the AC output end of the inverter.

[0048] In some examples, the target value of the negative-sequence component of the three-phase voltage can be superimposed on the target value of the positive-sequence component of the three-phase voltage to obtain a space vector voltage; a control signal is generated according to the space vector voltage to control the inverter. The target of the negative-sequence component of the three-phase voltage may include the target value of the negative-sequence component of the first-phase voltage, the target value of the negative-sequence of the second-phase voltage, and the target value of the negative-sequence component of the third-phase voltage. The target of the positive-sequence component of the three-phase voltage may include the target value of the positive-sequence component of the first phase, the target value of the positive-sequence component of the second-phase voltage, and the target value of the negative-sequence component of the third-phase voltage. The target value of the negative-sequence component of the first-phase voltage is superimposed on the target value of the positive-sequence component of the first-phase voltage, the target value of the negative-sequence component of the second-phase voltage is superimposed on the target value of the positive-sequence component of the second-phase voltage, and the target value of the negative-sequence component of the third-phase voltage is superimposed on the target value of the positive-sequence component of the third-phase voltage, so as to obtain a space vector voltage. A control signal such as a Pulse Width Modulation (PWM) signal is generated according to the space vector voltage to control the inverter. Superimposing the target value of the negative-sequence component of the three-phase voltage on the target value of the positive-sequence component of the three-phase voltage can compensate for the unbalanced voltage originally output by the inverter, improve the balance degree of the three-phase voltage at the AC output end of the inverter, and reduce or even eliminate the unbalance of the three-phase voltage at the AC output end of the inverter.

[0049] In the embodiments of the present application, based on the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in the wind turbine generator set in the two-phase rotating coordinate system, as well as the negative sequence target value of the d-axis voltage and the negative sequence target value of the q-axis voltage which are both 0, the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage can be obtained. The negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage are converted into the target value of the three-phase voltage negative sequence component in the three-phase stationary coordinate system. This target value of the three-phase voltage negative sequence component can improve the unstable phenomenon caused by the three-phase voltage imbalance. Using this target value of the three-phase voltage negative sequence component to compensate the target value of the three-phase voltage positive sequence component, the inverter in the wind turbine generator set is controlled to reduce or even eliminate the three-phase voltage imbalance, so that the inverter outputs AC electrical energy with a higher degree of three-phase voltage balance. In the case where the inverter outputs AC electrical energy with a higher degree of three-phase voltage balance, the electrical phases of the AC electrical energy output by the AC collector line are relatively more stable, and voltage oscillation and transient overvoltage can be reduced or even avoided, thereby improving the stability and safety of the weak system including the AC collector line.

[0050] In some embodiments, processing methods such as proportional-integral control and amplitude limiting can be used to obtain the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage. Figure 4 The flowchart of the control method for the variable frequency system of the wind turbine generator set provided by another embodiment of the present application Figure 4 is different from Figure 3 in that Figure 3 step S302 in Figure 4 can be specifically refined into Figure 3 steps S3021 to S3023 in Figure 4 and step S303 in

[0051] can be specifically refined into

[0052] In step S3021, obtain the first difference between the negative sequence target value of the d-axis voltage and the negative sequence component of the d-axis voltage, and the second difference between the negative sequence target value of the q-axis voltage and the negative sequence component of the q-axis voltage.

[0053] The first difference is the difference between the negative sequence target value of the d-axis voltage and the negative sequence component of the d-axis voltage. Since the negative sequence target value of the d-axis voltage is 0, the first difference can be the negative of the negative sequence component of the d-axis voltage. The second difference is the difference between the negative sequence target value of the q-axis voltage and the negative sequence component of the q-axis voltage. Since the negative sequence target value of the q-axis voltage is 0, the second difference can be the negative of the negative sequence component of the q-axis voltage.

[0054] Input the first difference into a proportional-integral controller, i.e., a PI controller, and the proportional-integral controller outputs the corresponding negative-sequence reference value of the d-axis voltage. Input the second difference into the proportional-integral controller, and the proportional-integral controller outputs the corresponding negative-sequence reference value of the q-axis voltage. The negative-sequence reference value of the d-axis voltage output by the proportional-integral controller based on the first difference can reduce the deviation between the negative-sequence target value of the d-axis voltage and the negative-sequence component of the d-axis voltage. The negative-sequence reference value of the q-axis voltage output by the proportional-integral controller based on the second difference can reduce the deviation between the negative-sequence target value of the q-axis voltage and the negative-sequence component of the q-axis voltage.

[0055] In step S3023, perform amplitude limiting processing on the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage.

[0056] The upper limit value of the voltage amplitude and the lower limit value of the voltage amplitude can be set. The negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage are respectively subjected to amplitude limiting processing through the upper limit value of the voltage amplitude and the lower limit value of the voltage amplitude, so that the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage after amplitude limiting processing are less than or equal to the upper limit value of the voltage amplitude and greater than or equal to the lower limit value of the voltage amplitude, avoiding overvoltage and undervoltage conditions.

[0057] In step S303 of the above embodiment, the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage after amplitude limiting processing can be transformed into the target values of the three-phase voltage negative-sequence components in the three-phase stationary coordinate system.

[0058] In step S3031, transform the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage into the third voltage negative-sequence component and the fourth voltage negative-sequence component in the two-phase plane rectangular coordinate system.

[0059] The negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage are the negative-sequence voltage reference values in the two-phase rotating coordinate system. The third voltage negative-sequence component and the fourth voltage negative-sequence component can be obtained through the inverse transformation of park. The third negative-sequence component can be the negative-sequence component of the α-axis voltage obtained by the inverse transformation, and the fourth negative-sequence component can be the negative-sequence component of the β-axis voltage obtained by the inverse transformation.

[0060] In step S3032, transform the third voltage negative-sequence component and the fourth voltage negative-sequence component into the target values of the three-phase voltage negative-sequence components in the three-phase stationary coordinate system.

[0061] To facilitate the compensation of the target values of the three-phase voltage negative-sequence components for the target values of the three-phase voltage positive-sequence components in the subsequent steps, the third voltage negative-sequence component and the fourth voltage negative-sequence component can be transformed into the target values of the three-phase voltage negative-sequence components in the three-phase stationary coordinate system through the inverse transformation of clark, so as to facilitate the superposition of the target values of the three-phase voltage negative-sequence components and the three-phase voltage positive-sequence components in the three-phase stationary coordinate system.

[0062] Through the transformation of the two-phase plane rectangular coordinate system and the three-phase stationary coordinate system, the d-axis negative-sequence reference value that can reduce the deviation between the d-axis voltage negative-sequence target value and the d-axis voltage negative-sequence component, and the q-axis negative-sequence reference value that can reduce the deviation between the q-axis voltage negative-sequence target value and the q-axis voltage negative-sequence component are converted to the three-phase stationary coordinate system, so as to realize the compensation of the three-phase voltage positive-sequence component and improve the balance degree of the three-phase voltage at the AC output end of the inverter.

[0063] The control method of the converter system of the wind turbine generator set in the embodiment of the present application can be executed in the normal operation state of the wind turbine generator set, or can be executed only when it is detected that the three-phase voltage of the AC collector line is unbalanced.

[0064] Executing the above control method of the converter system of the wind turbine generator set in the normal operation state of the wind turbine generator set will not cause adverse effects on the normal operation of the wind turbine generator set, and can quickly respond when the three-phase voltage of the wind turbine generator set is unbalanced, directly perform compensation, reduce the degree of three-phase voltage imbalance or even eliminate the three-phase voltage imbalance.

[0065] The three-phase voltage imbalance can be caused by the non-full-phase operation of the wind power transmission system where the converter system is located and other situations. For example, the non-full-phase operation of the wind power transmission system where the converter system is located may include single-phase disconnection and two-phase disconnection. When a high-probability fault condition such as single-phase instantaneous grounding occurs, it is necessary to control the corresponding circuit breaker of the fault phase to disconnect to cut out the fault phase, which is equivalent to single-phase disconnection. Before the circuit breaker recloses, the wind power transmission system where the converter system is located is in the non-full-phase operation process. During the non-full-phase operation, overvoltage and voltage oscillation will occur in the converter system. On the one hand, it affects the stability of the converter system, and on the other hand, in this case, in order to ensure the safety of the converter system, the voltage output limit of the converter system will be restricted. Another example is that during low-voltage ride-through, the wind turbine generator set will provide capacitive reactive power support. When the low-voltage ride-through ends, the voltage of the converter system recovers. However, if the capacitive reactive power provided by the wind turbine generator set is not recovered in time, reactive power redundancy will occur and overvoltage will occur. When it is detected that the three-phase voltage of the AC collector line is unbalanced, the d-axis voltage negative-sequence component and the q-axis voltage negative-sequence component of the voltage at the AC output end of the inverter are obtained, and subsequent steps are executed to control the inverter, which can control the wind turbine generator set more flexibly. When the wind turbine generator set is operating normally, a converter system control method more suitable for the normal operation scenario is adopted to achieve the balance of high-efficiency operation of the wind turbine generator set and improve the stability and safety of the wind turbine generator set.

[0066] For ease of understanding, the control method of the converter system of the wind turbine generator in the above embodiments will be described below through a logic diagram. When a non-full-phase condition occurs in the outgoing line of the wind farm, the grid voltage will become asymmetric, and at the same time, the grid impedance will also be asymmetric. The current output by the wind turbine generator will act on the unbalanced grid impedance, resulting in an unbalanced voltage at the wind turbine generator terminal, that is, a three-phase voltage unbalance occurs. In a weak system, it is easy to trigger the switching of the fault ride-through mode of the wind turbine generator, resulting in voltage oscillation and overvoltage. At this time, if the method of injecting negative-sequence current into the grid is adopted, it is easy to produce a counter-effect, further aggravating the voltage oscillation and overvoltage. The logic of the converter system control method in the embodiments of the present application is as Figure 5 shown. The negative-sequence components Ea-, Eb-, and Ec- of the three-phase voltage of the output voltage of the converter system obtained can be subjected to Clark transformation to obtain the first voltage negative-sequence component Eα- and the second voltage negative-sequence component Eβ- in the two-phase plane rectangular coordinate system; according to the phase angle θ of the negative-sequence component, the first voltage negative-sequence component Eα- and the second voltage negative-sequence component Eβ- are subjected to Park transformation to obtain the d-axis voltage negative-sequence component Ed- and the q-axis voltage negative-sequence component Eq-; set the d-axis voltage negative-sequence target value and the q-axis voltage negative-sequence target value to 0, input the first difference between 0 and the d-axis voltage negative-sequence component Ed- into the first PI controller, and limit the output of the first PI controller through the voltage amplitude upper limit value Emax and the voltage amplitude lower limit value Emin to obtain the limited d-axis voltage negative-sequence reference value E * d-; input the second difference between 0 and the q-axis voltage negative-sequence component Eq- into the second PI controller, and limit the output of the second PI controller through the voltage amplitude upper limit value Emax and the voltage amplitude lower limit value Emin to obtain the limited q-axis voltage negative-sequence reference value E * q-; according to the phase angle θ of the negative-sequence component, the limited d-axis voltage negative-sequence reference value E * d- and the limited q-axis voltage negative-sequence reference value E * q- are subjected to inverse Park transformation to obtain the third voltage negative-sequence component E * α- and the fourth voltage negative-sequence component E * β- in the two-phase plane rectangular coordinate system; the third voltage negative-sequence component E * α- and the fourth voltage negative-sequence component E * β- are subjected to inverse Clark transformation to obtain the three-phase voltage negative-sequence component target values E * a-, E * b-, and E * c- in the three-phase stationary coordinate system; the three-phase voltage negative-sequence component target values E * a-, E * b-, E * c- and the three-phase voltage positive-sequence component target values E* a+, E * b+, E * c+ are respectively superimposed to obtain the space vector voltage E * a, E * b and E * c; The inverter in the wind turbine generator set can be controlled according to the space vector voltage E * a, E * b and E * c. An embodiment of the present application proposes a transient voltage control technology to solve the problems of voltage oscillation and overvoltage. By controlling the negative sequence voltage, the three-phase voltage balance degree of the AC output end of the inverter in the wind power generation unit can be improved, the switching of the fault ride-through mode of the wind turbine generator set can be avoided, and voltage oscillation and overvoltage can be suppressed.

[0067] In some embodiments, the three-phase voltage imbalance generated in the converter system is sometimes difficult to be compensated to balance by a single wind turbine generator set. The converter system control method of the wind turbine generator set in the above embodiments can be executed by controlling multiple wind turbine generator sets in the converter system, so that the multiple wind turbine generator sets cooperate together to compensate and compensate the three-phase voltage imbalance generated in the converter system to balance.

[0068] In some embodiments, a distributed synchronous condenser can also be set on the output side of the converter system. By adjusting the electric phase of the synchronous condenser, the unbalanced three-phase voltage can be adjusted to balance.

[0069] The second aspect of the present application provides a converter system control device for a wind turbine generator set. The converter system includes a rectifier and an inverter electrically connected in the wind turbine generator set. The inverter is connected to the AC collector line. For specific content, reference can be made to the relevant descriptions in the above embodiments and will not be elaborated here. Figure 6 It is a schematic structural diagram of a converter system control device for a wind turbine generator set provided by an embodiment of the present application. As Figure 6 shown, the converter system control device 400 of the wind turbine generator set may include an acquisition module 401, a processing module 402, a transformation module 403, and a control module 404.

[0070] The acquisition module 401 can be used to acquire the d-axis voltage negative sequence component and the q-axis voltage negative sequence component of the voltage at the AC output end of the inverter in the two-phase rotating coordinate system.

[0071] The processing module 402 can be used to obtain the d-axis voltage negative sequence reference value and the q-axis voltage negative sequence reference value based on the d-axis voltage negative sequence component, the q-axis voltage negative sequence component, the given d-axis voltage negative sequence target value, and the q-axis voltage negative sequence target value.

[0072] The d-axis voltage negative sequence target value and the q-axis voltage negative sequence target value are 0.

[0073] The transformation module 403 can be used to transform the d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value into the target values of the three-phase voltage negative-sequence components in the three-phase stationary coordinate system.

[0074] The control module 404 can be used to control the inverter according to the target values of the three-phase voltage negative-sequence components and the obtained target values of the three-phase voltage positive-sequence components.

[0075] In the embodiment of the present application, the d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value can be obtained based on the d-axis voltage negative-sequence component and the q-axis voltage negative-sequence component of the AC output terminal voltage of the inverter in the two-phase rotating coordinate system of the wind turbine generator set, and the d-axis voltage negative-sequence target value and the q-axis voltage negative-sequence target value that are 0. The d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value are converted into the target values of the three-phase voltage negative-sequence components in the three-phase stationary coordinate system. The target values of the three-phase voltage negative-sequence components can improve the unstable phenomenon caused by the three-phase voltage imbalance. The target values of the three-phase voltage negative-sequence components are used to compensate the target values of the three-phase voltage positive-sequence components, and the inverter in the wind turbine generator set is controlled to reduce or even eliminate the three-phase voltage imbalance, so that the inverter outputs AC electric energy with a higher degree of three-phase voltage balance. In the case where the inverter outputs AC electric energy with a higher degree of three-phase voltage balance, the electric phases of the AC electric energy output by the AC collector line are relatively more stable, and the voltage oscillation and transient overvoltage conditions are reduced or even avoided, thereby improving the stability and safety of the weak system including the AC collector line of the wind farm.

[0076] In some embodiments, the processing module 402 may specifically be used to: obtain the first difference between the d-axis voltage negative-sequence target value and the d-axis voltage negative-sequence component, and the second difference between the q-axis voltage negative-sequence target value and the q-axis voltage negative-sequence component; input the first difference and the second difference into a proportional-integral controller respectively to obtain the output d-axis voltage negative-sequence reference value and q-axis voltage negative-sequence reference value.

[0077] In some examples, the processing module 402 may also specifically be used to: perform clipping processing on the d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value.

[0078] In some embodiments, the acquisition module 401 may specifically be used to: acquire the three-phase voltage negative-sequence components of the AC output terminal voltage of the inverter; transform the three-phase voltage negative-sequence components into the first voltage negative-sequence component and the second voltage negative-sequence component in the two-phase plane rectangular coordinate system; transform the first voltage negative-sequence component and the second voltage negative-sequence component into the d-axis voltage negative-sequence component and the q-axis voltage negative-sequence component in the two-phase rotating coordinate system.

[0079] In some embodiments, the transformation module 403 may be specifically configured to: transform the d-axis voltage negative-sequence reference value and the q-axis voltage negative-sequence reference value into a third voltage negative-sequence component and a fourth voltage negative-sequence component in a two-phase plane rectangular coordinate system; and transform the third voltage negative-sequence component and the fourth voltage negative-sequence component into a target value of the three-phase voltage negative-sequence component in a three-phase stationary coordinate system.

[0080] In some embodiments, the control module 404 may be specifically configured to: superimpose the target value of the three-phase voltage negative-sequence component onto the target value of the three-phase voltage positive-sequence component to obtain a space vector voltage; and generate a control signal according to the space vector voltage to control the inverter.

[0081] In some embodiments, the acquisition module 401 may be specifically configured to: when detecting that the three-phase voltage of the AC collector line is unbalanced, acquire the d-axis voltage negative-sequence component and the q-axis voltage negative-sequence component of the voltage at the AC output terminal of the inverter in a two-phase rotating coordinate system.

[0082] The third aspect of the present application provides a converter controller for a wind turbine generator. Figure 7 It is a schematic structural diagram of a converter controller for a wind turbine generator provided in an embodiment of the present application. As Figure 7 shown, the converter controller 500 of the wind turbine generator includes a memory 501, a processor 502, and a computer program stored on the memory 501 and executable on the processor 502.

[0083] In some examples, the above-mentioned processor 502 may include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0084] The memory 501 may include a read-only memory (ROM), a random access memory (RAM), a magnetic disk storage medium device, an optical storage medium device, a flash memory device, an electrical, optical, or other physical / tangible memory storage device. Thus, generally, the memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the control method of the converter system of the wind turbine generator according to the embodiments of the present application.

[0085] The processor 502 runs a computer program corresponding to the executable program code by reading the executable program code stored in the memory 501, so as to implement the control method of the variable frequency conversion system of the wind turbine in the above embodiments.

[0086] In some examples, the variable frequency conversion controller 500 of the wind turbine may further include a communication interface 503 and a bus 504. Among them, as Figure 7 shown, the memory 501, the processor 502, and the communication interface 503 are connected through the bus 504 and complete communication with each other.

[0087] The communication interface 503 is mainly used to implement communication between various modules, devices, units, and / or devices in the embodiments of the present application. The input device and / or output device may also be accessed through the communication interface 503.

[0088] The bus 504 includes hardware, software, or both, and couples the components of the variable frequency conversion controller 500 of the wind turbine to each other. By way of example and not limitation, the bus 504 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a Hyper Transport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an InfiniBand interconnect, a Low Pin Count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-E) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local Bus (VLB) bus, or other suitable buses or a combination of two or more of these. In a suitable case, the bus 504 may include one or more buses. Although the embodiments of the present application describe and illustrate specific buses, the present application contemplates any suitable bus or interconnect.

[0089] In a fourth aspect of the present application, a computer-readable storage medium is further provided. Computer program instructions are stored on the computer-readable storage medium. When the computer program instructions are executed by a processor, the control method of the converter system of the wind turbine generator set in the above embodiments can be implemented, and the same technical effects can be achieved. To avoid repetition, details are not described herein again. Among them, the above computer-readable storage medium may include a non-transitory computer-readable storage medium, such as a read-only memory (ROM for short), a random access memory (RAM for short), a magnetic disk, or an optical disc, etc., which is not limited herein.

[0090] An embodiment of the present application provides a computer program product. When the instructions in the computer program product are executed by a processor of an electronic device, the electronic device is enabled to execute the control method of the converter system of the wind turbine generator set in the above embodiments, and the same technical effects can be achieved. To avoid repetition, details are not described herein again.

[0091] It should be clear that the various embodiments in this specification are described in a progressive manner. For the parts that are the same or similar among the various embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. For the device embodiments, equipment embodiments, controller embodiments, computer-readable storage medium embodiments, and computer program product embodiments, the relevant parts can refer to the description part of the method embodiments. The present application is not limited to the specific steps and structures described above and shown in the figures. Those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present application. And, for the sake of brevity, the detailed description of known method technologies is omitted here.

[0092] The above has described various aspects of the present application with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present application. It should be understood that each block in the flowchart and / or block diagram, and the combination of blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing devices to generate a machine, such that these instructions executed by the processor of the computer or other programmable data processing devices enable the implementation of the functions / actions specified in one or more blocks of the flowchart and / or block diagram. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field programmable logic circuit. It is also understood that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can also be implemented by dedicated hardware that performs the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0093] Those skilled in the art should understand that the above embodiments are all exemplary rather than restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on the study of the drawings, the description and the claims, those skilled in the art should be able to understand and implement other variations of the disclosed embodiments. In the claims, the term "comprising" does not exclude other devices or steps; the quantifier "a" does not exclude a plurality; the terms "first" and "second" are used to label names rather than to indicate any particular order. Any reference signs in the claims should not be construed as limiting the scope of protection. The functions of multiple parts appearing in the claims can be implemented by a single hardware or software module. The fact that certain technical features appear in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.

Claims

1. A control method for a variable frequency converter system of a wind turbine generator, characterized in that, The converter system includes a rectifier and an inverter electrically connected in the wind turbine generator set, and the inverter is connected to the AC collector line; The method includes: Obtaining the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in a two-phase rotating coordinate system; Based on the negative sequence component of the d-axis voltage, the negative sequence component of the q-axis voltage, the given negative sequence target value of the d-axis voltage, and the negative sequence target value of the q-axis voltage, obtaining the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage, where the negative sequence target value of the d-axis voltage and the negative sequence target value of the q-axis voltage are 0; Converting the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage into the target value of the three-phase voltage negative sequence component in a three-phase stationary coordinate system; Controlling the inverter according to the target value of the three-phase voltage negative sequence component and the obtained target value of the three-phase voltage positive sequence component.

2. The method according to claim 1, wherein The obtaining the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage based on the negative sequence component of the d-axis voltage, the negative sequence component of the q-axis voltage, the given negative sequence target value of the d-axis voltage, and the given negative sequence target voltage of the q-axis voltage includes: Obtaining a first difference between the negative sequence target value of the d-axis voltage and the negative sequence component of the d-axis voltage, and a second difference between the negative sequence target value of the q-axis voltage and the negative sequence component of the q-axis voltage; Inputting the first difference and the second difference into a proportional-integral controller respectively to obtain the output negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage.

3. The method according to claim 2, wherein It further includes: Performing a clipping process on the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage.

4. The method according to claim 1, wherein The obtaining the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in a two-phase rotating coordinate system includes: Obtaining the three-phase voltage negative sequence component of the AC output terminal voltage of the inverter; Converting the three-phase voltage negative sequence component into a first voltage negative sequence component and a second voltage negative sequence component in a two-phase plane rectangular coordinate system; Converting the first voltage negative sequence component and the second voltage negative sequence component into the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage in a two-phase rotating coordinate system.

5. The method according to claim 1, characterized in that, The converting the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage into the target value of the three-phase voltage negative sequence component in a three-phase stationary coordinate system includes: Converting the negative sequence reference value of the d-axis voltage and the negative sequence reference value of the q-axis voltage into a third voltage negative sequence component and a fourth voltage negative sequence component in a two-phase plane rectangular coordinate system; Converting the third voltage negative sequence component and the fourth voltage negative sequence component into the target value of the three-phase voltage negative sequence component in a three-phase stationary coordinate system.

6. The method according to claim 1, wherein The controlling the inverter according to the target value of the three-phase voltage negative sequence component and the obtained target value of the three-phase voltage positive sequence component includes: Superposing the three-phase voltage negative sequence component target with the target value of the three-phase voltage positive sequence component to obtain a space vector voltage; Generating a control signal according to the space vector voltage to control the inverter.

7. The method according to claim 1, wherein The obtaining the negative sequence component of the d-axis voltage and the negative sequence component of the q-axis voltage of the AC output terminal voltage of the inverter in a two-phase rotating coordinate system includes: When it is detected that there is a three-phase voltage imbalance in the AC collector line, obtain the negative-sequence component of the d-axis voltage and the negative-sequence component of the q-axis voltage of the voltage at the AC output terminal of the inverter in a two-phase rotating coordinate system.

8. A control device for a variable frequency converter system of a wind turbine generator, characterized in that, The converter system includes a rectifier and an inverter electrically connected in the wind turbine generator set, and the inverter is connected to the AC collector line; The device includes: An acquisition module, configured to acquire the negative-sequence component of the d-axis voltage and the negative-sequence component of the q-axis voltage of the voltage at the AC output terminal of the inverter in a two-phase rotating coordinate system; A processing module, configured to obtain a negative-sequence reference value of the d-axis voltage and a negative-sequence reference value of the q-axis voltage based on the negative-sequence component of the d-axis voltage, the negative-sequence component of the q-axis voltage, a given negative-sequence target value of the d-axis voltage, and a negative-sequence target value of the q-axis voltage, where the negative-sequence target value of the d-axis voltage and the negative-sequence target value of the q-axis voltage are 0; A transformation module, configured to transform the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage into a target value of the three-phase voltage negative-sequence component in a three-phase stationary coordinate system; A control module, configured to control the inverter according to the target value of the three-phase voltage negative-sequence component and the acquired target value of the three-phase voltage positive-sequence component.

9. The device according to claim 8, characterized in that, The processing module is configured to: Obtain a first difference between the negative-sequence target value of the d-axis voltage and the negative-sequence component of the d-axis voltage, and a second difference between the negative-sequence target value of the q-axis voltage and the negative-sequence component of the q-axis voltage; Input the first difference and the second difference into a proportional-integral controller respectively to obtain the output negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage.

10. The device according to claim 9, characterized in that, The processing module is further configured to: Perform a clipping process on the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage.

11. The device according to claim 8, characterized in that, The acquisition module is configured to: Obtain the three-phase voltage negative-sequence component of the voltage at the AC output terminal of the inverter; Transform the three-phase voltage negative-sequence component into a first voltage negative-sequence component and a second voltage negative-sequence component in a two-phase plane rectangular coordinate system; Transform the first voltage negative-sequence component and the second voltage negative-sequence component into the negative-sequence component of the d-axis voltage and the negative-sequence component of the q-axis voltage in a two-phase rotating coordinate system.

12. The device according to claim 8, wherein The transformation module is configured to: Transform the negative-sequence reference value of the d-axis voltage and the negative-sequence reference value of the q-axis voltage into a third voltage negative-sequence component and a fourth voltage negative-sequence component in a two-phase plane rectangular coordinate system; Transform the third voltage negative-sequence component and the fourth voltage negative-sequence component into the target value of the three-phase voltage negative-sequence component in a three-phase stationary coordinate system.

13. The device according to claim 8, characterized in that, The control module is configured to: Superimpose the target value of the three-phase voltage negative-sequence component and the target value of the three-phase voltage positive-sequence component to obtain a space vector voltage; Generate a control signal according to the space vector voltage to control the inverter.

14. The device according to claim 8, characterized in that, The acquisition module is configured to: When it is detected that there is a three-phase voltage imbalance in the AC collector line, obtain the negative-sequence component of the d-axis voltage and the negative-sequence component of the q-axis voltage of the voltage at the AC output terminal of the inverter in a two-phase rotating coordinate system.

15. A converter system controller for a wind turbine generator, characterized in that, Includes: A processor and a memory storing computer program instructions; When the processor executes the computer program instructions, the control method for the converter system of the wind turbine generator set as described in any one of claims 1 to 7 is implemented.

16. A computer-readable storage medium, characterized in that, Computer program instructions are stored on the computer-readable storage medium, and when the computer program instructions are executed by the processor, the control method for the converter system of the wind turbine generator set as described in any one of claims 1 to 7 is implemented.

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