Unbalance control method and device for power grid side converter of wind turbine generator

Abstract

The invention provides an unbalance control method and device for a power grid side converter of a wind turbine generator, and the method comprises the steps: obtaining a positive sequence voltage adjustment signal, a negative sequence voltage adjustment signal, a positive sequence current adjustment signal and a negative sequence current adjustment signal at a power grid side, and reducing the negative effects, such as the increase of equipment loss and the reduction of operation efficiency, caused by voltage unbalance. The three-phase power grid AC-side current reference signal is determined according to the input power of the three-phase power grid and the positive-sequence and negative-sequence voltage regulation signals, so that the acquisition process of the three-phase power grid AC-side current reference signal is more accurate. The AC-side reference voltage is determined according to the positive-sequence and negative-sequence current adjusting signals and the AC-side current reference signal of the three-phase power grid, the working condition of unbalanced power grid voltage can be better adapted, and stable operation of the power grid is ensured. The bridge circuit AC input voltage control signal used for adjusting the unbalanced state is determined according to the AC side reference voltage, effective adjustment of the unbalanced state of the power grid voltage is achieved, and the stability and reliability of the power grid are improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to an unbalance control method and device for a grid-side converter of a wind turbine. Background Technology

[0002] When there is an imbalance in the grid voltage (asymmetry in the amplitude or phase of the three-phase voltage), if the converter still adopts a control strategy under balanced conditions (such as designing only for the positive sequence component), it will cause a negative sequence current to be generated on the AC side. The interaction between the negative sequence current and the unbalanced voltage will induce characteristic harmonics (harmonics related to the grid frequency) and non-characteristic harmonics (randomly distributed harmonics) on the DC side, polluting the DC bus voltage and current.

[0003] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0004] The purpose of this application is to at least partially solve one of the technical problems in the related art.

[0005] Therefore, the first objective of this application is to propose an unbalanced control method for the grid-side converter of a wind turbine.

[0006] The second objective of this application is to provide an unbalance control device for a grid-side converter of a wind turbine.

[0007] The third objective of this application is to propose an electronic device.

[0008] The fourth objective of this application is to provide a computer-readable storage medium.

[0009] The fifth objective of this application is to provide a computer program product.

[0010] To achieve the above objectives, the first aspect of this application proposes an unbalanced control method for a wind turbine grid-side converter, comprising: In response to the unbalanced state of the three-phase grid voltage, positive sequence voltage regulation signal, positive sequence current regulation signal and negative sequence current regulation signal are obtained from the grid side; The AC side current reference signal of the three-phase power grid is determined based on the input power of the three-phase power grid, the positive sequence voltage regulation signal, and the negative sequence voltage regulation signal. The AC side reference voltage is determined based on the positive sequence current adjustment signal, the negative sequence current adjustment signal, and the three-phase power grid AC side current reference signal. The bridge AC input voltage control signal for adjusting the unbalanced state is determined based on the AC side reference voltage.

[0011] To achieve the above objectives, a second aspect of this application provides an unbalanced control device for a wind turbine grid-side converter, wherein the unbalanced control device is configured to implement the steps of the unbalanced control method for a wind turbine grid-side converter proposed in the first aspect of this application.

[0012] To achieve the above objectives, a third aspect of this application provides an electronic device, comprising: a processor; and a memory for storing processor-executable instructions; wherein the processor is configured to execute the instructions to implement the steps of the unbalance control method for a wind turbine grid-side converter proposed in the first aspect of this application.

[0013] To achieve the above objectives, a fourth aspect of this application provides a computer-readable storage medium that, when the instructions in the storage medium are executed by a processor of an electronic device, enables the electronic device to perform the steps of implementing the unbalance control method for the grid-side converter of a wind turbine generator proposed in the first aspect of this application.

[0014] To achieve the above objectives, a fifth aspect of this application provides a computer program product, including a computer program that, when executed by a processor in a communication device, implements the steps of the unbalanced control method for the grid-side converter of a wind turbine generator proposed in the first aspect of this application.

[0015] In this embodiment, by acquiring positive-sequence voltage regulation signals, negative-sequence voltage regulation signals, positive-sequence current regulation signals, and negative-sequence current regulation signals on the grid side, the system can specifically address situations where the three-phase grid voltage is unbalanced. This helps improve the grid's operational quality and reduces the negative impacts of increased equipment losses and reduced operating efficiency caused by voltage imbalance. The AC-side current reference signal of the three-phase grid is determined based on the input power of the three-phase grid and the positive-sequence and negative-sequence voltage regulation signals. This calculation method, which integrates multiple factors, makes the acquisition of the AC-side current reference signal more accurate, providing a reliable basis for subsequent regulation and control. The AC-side reference voltage is determined based on the positive-sequence and negative-sequence current regulation signals and the AC-side current reference signal of the three-phase grid, making the AC-side voltage control more reasonable and better adaptable to grid voltage imbalance conditions, ensuring stable grid operation. The bridge AC input voltage control signal, used to regulate the unbalanced state, is determined based on the AC-side reference voltage. This control signal precisely regulates the bridge AC input voltage, thereby achieving effective regulation of the grid voltage imbalance and improving the grid's stability and reliability.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the mathematical model of the grid-side converter under grid voltage balance conditions provided in the embodiments of this application; Figure 2 A flowchart illustrating an unbalanced control method for a grid-side converter of a wind turbine provided in an embodiment of this application; Figure 3 A flowchart illustrating another unbalanced control method for a wind turbine grid-side converter provided in an embodiment of this application; Figure 4 This is a schematic diagram of the unbalance control model of the grid-side converter of the wind turbine provided in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of an electronic device provided according to an embodiment of this application. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0019] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a” and “the” as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0020] It should be understood that although the terms first, second, third, etc., may be used to describe various information in the embodiments of this application, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words "if" and "suppose" as used herein can be interpreted as "when," "when," or "in response to a determination."

[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0022] Figure 1 This is a schematic diagram of the mathematical model of the grid-side converter under grid voltage balance conditions provided in the embodiments of this application. Figure 1 As shown, under voltage balance conditions, if the line-to-line impedance is neglected, the following relationship for the grid-side converter can be obtained according to Kirchhoff's voltage law:

[0023] in, , , For the three-phase bridge arm switching function, when When the upper arm is connected, The arm is currently conducting. ; The voltage between node O and node N; Based on P dc Obtain.

[0024] However, the actual operating environment of the power grid is complex and variable, and voltage imbalance often occurs, posing a severe challenge to the normal operation of the converter. When there is a voltage imbalance in the power grid, that is, when the amplitude or phase of the three-phase voltage is asymmetrical, if the converter still uses the control strategy under balanced conditions, it will cause a series of serious problems and negatively affect the stable operation of the power system and power quality.

[0025] In some scenarios, voltage imbalance in the power grid can have multiple causes. Regarding transmission lines, differences in the laying environment, uneven conductor materials, or varying degrees of aging can lead to deviations in parameters such as resistance and reactance of the three-phase lines, resulting in asymmetry in the amplitude or phase of the three-phase voltage. Furthermore, the unbalanced connection of large single-phase loads is also a significant factor. For example, in some industrial areas, a large number of single-phase welding machines, electric arc furnaces, and other equipment are concentrated on one or two phases, causing the load on that phase to be much greater than on the others, disrupting the balance of the three-phase load and causing voltage imbalance. Simultaneously, faults in the power system, such as single-phase grounding faults and phase-to-phase short-circuit faults, can also cause temporary or persistent voltage imbalances in the power grid during the fault occurrence and recovery process.

[0026] In some scenarios, grid voltage imbalance mainly manifests as unequal amplitudes or asymmetrical phases of the three-phase voltages. In cases of amplitude imbalance, the effective values ​​of the three-phase voltages differ significantly, potentially exhibiting a distribution pattern of one phase high and two phases low, or two phases high and one phase low. Phase imbalance, on the other hand, is characterized by a phase difference between the three-phase voltages deviating from the standard 120° electrical angle, resulting in an asymmetrical distribution of the voltage waveforms along the time axis. This unbalanced voltage state poses significant challenges to converter control.

[0027] Traditional converter control strategies are typically designed based on the assumption of grid voltage balance. Control methods designed solely for the positive-sequence component decompose the grid voltage into positive-sequence, negative-sequence, and zero-sequence components. Under balanced grid conditions, the negative-sequence and zero-sequence components are theoretically zero. Therefore, the control strategy only needs to consider the positive-sequence component, achieving precise control of active and reactive power by adjusting the converter's switching state, ensuring that the AC current is in phase with or has a specific phase relationship with the positive-sequence voltage, thus achieving efficient power conversion. However, when grid voltage imbalance occurs, the presence of negative-sequence and zero-sequence components in the actual grid, which the control strategy fails to effectively address, leads to a significant decrease in converter control performance. Specifically, the converter cannot accurately track changes in grid voltage, causing distortion in the AC current, which no longer maintains an ideal sinusoidal waveform. More seriously, this control strategy can induce negative-sequence current on the AC side.

[0028] In some scenarios, negative-sequence current is the result of the combined effects of grid voltage imbalance and converter imbalance control. When the grid voltage is unbalanced, positive-sequence, negative-sequence, and zero-sequence voltage components coexist. If the converter continues to operate according to the control strategy under balanced conditions, its control algorithm cannot adapt to the influence of negative-sequence voltage, leading to the appearance of a negative-sequence current component in the AC side current. The presence of negative-sequence current disrupts the symmetry of the AC side current, causing the amplitude and phase of the three-phase current to become unbalanced.

[0029] In some scenarios, the interaction between negative-sequence current and unbalanced voltage can induce a series of complex harmonic problems on the DC side. From the perspective of harmonic generation mechanisms, the interaction between negative-sequence current and positive-sequence and negative-sequence voltages generates power fluctuations. These power fluctuations are transmitted through the DC-side capacitors of the converter (such as...). Figure 1 The capacitor C shown is used for buffering and regulation, but due to the limited energy storage and release capacity of the capacitor, it cannot completely eliminate the influence of power fluctuations, resulting in harmonics in the DC bus voltage and current.

[0030] In some scenarios, harmonic pollution of DC bus voltage and current can have multiple negative impacts on the entire power system. First, harmonics cause increased fluctuations in DC bus voltage, making it difficult for downstream power electronic devices, such as inverters and DC motors, to obtain a stable DC power input. This affects the control accuracy and operational performance of these devices, leading to output waveform distortion, reduced efficiency, and potentially even equipment failure. For example, in renewable energy generation systems, fluctuations in DC bus voltage can affect the grid connection performance of inverters, causing excessive harmonics in the grid-connected current, impacting power quality, and possibly even resulting in grid rejection.

[0031] Secondly, harmonic currents generate additional losses in the DC-side circuit, reducing the overall system efficiency. Because harmonic currents have higher frequencies, their resistive losses in the circuit increase with frequency, leading to increased circuit heating and shortening the equipment's lifespan. Simultaneously, harmonics can cause electromagnetic interference, affecting the normal operation of surrounding electronic equipment and communication systems. For example, harmonics may interfere with nearby sensor signals, resulting in inaccurate measurement data; they may also interfere with communication lines, causing data transmission errors or interruptions.

[0032] In summary, when there is a voltage imbalance in the power grid, the converter's control strategy under balanced conditions can lead to negative sequence current on the AC side, which in turn induces characteristic and non-characteristic harmonics on the DC side, polluting the DC bus voltage and current. This problem not only affects the normal operation of power electronic equipment but also threatens the stability and power quality of the power system. Therefore, adopting effective countermeasures for voltage imbalance is of significant practical importance.

[0033] The following describes, with reference to the accompanying drawings, an embodiment of the unbalance control method and apparatus for the grid-side converter of a wind turbine generator set.

[0034] Figure 2 This is a flowchart illustrating an unbalanced control method for a wind turbine grid-side converter provided in an embodiment of this application.

[0035] like Figure 2 As shown, the method includes, but is not limited to, the following steps: S201, in response to the unbalanced state of the three-phase grid voltage, obtains positive sequence voltage regulation signal, negative sequence voltage regulation signal, positive sequence current regulation signal and negative sequence current regulation signal from the grid side.

[0036] In one feasible implementation, if the three-phase grid voltage is unbalanced and only the fundamental voltage is considered, then the three-phase grid voltage E can be described as a positive-sequence voltage. Negative sequence voltage and zero sequence voltage Thus obtain .

[0037] In one feasible implementation, based on the peak value of the positive sequence fundamental voltage... negative sequence fundamental voltage peak value Zero-sequence fundamental voltage peak value Initial phase angle of positive sequence fundamental voltage Initial phase angle of negative sequence fundamental voltage and the initial phase angle of the zero-sequence fundamental voltage The following relation is obtained:

[0038] in, For phase a in a three-phase power grid, For the b-phase component in a three-phase power grid, This represents the c-phase component in a three-phase power grid.

[0039] In one feasible implementation, the three-phase stationary coordinate system is transformed into a two-phase synchronous rotating coordinate system, yielding the following relationship:

[0040] in, This is the coordinate transformation matrix. ; This is the orthogonal rotation coordinate transformation matrix. ; This is a negative-order rotation coordinate transformation matrix; For positive-order d-axis components, These are the positive-sequence q-axis components. For negative d-axis components, These are the negative-order q-axis components.

[0041] In one feasible implementation, a two-phase stationary coordinate system is used. The complex vector of the three-phase grid voltage of the grid-side converter is obtained. for:

[0042] If the three-phase power grid voltage is unbalanced, then the three-phase power grid voltage complex vector... There are positive-order and negative-order components, resulting in the following relation:

[0043] in, The angular frequency of the three-phase grid voltage. Two-phase stationary coordinate system Three-phase power grid voltage complex vector The positive order components, Two-phase stationary coordinate system Three-phase power grid voltage complex vector The negative order components, , .

[0044] From the above expression, it can be seen that in the two-phase stationary coordinate system middle, It is a model In a counter-clockwise direction with angular frequency Rotating space vector, It is a model In a clockwise direction with angular frequency A rotating spatial vector.

[0045] In one feasible implementation, a two-phase stationary coordinate system is obtained based on the topology of the grid-side converter and the model in the three-phase stationary coordinate system. The following complex vector model equations:

[0046] in, , representing a two-phase stationary coordinate system The composite vector of the fundamental voltage at the AC input terminal of the converter on the grid side; , representing a two-phase stationary coordinate system The composite vector of AC current from the converter on the grid side.

[0047] In one feasible implementation, if the three-phase power grid voltage is unbalanced, and Both contain positive-order and negative-order components, which further leads to the following expression:

[0048] in, , , , .

[0049] In one feasible implementation, the expression in a two-phase synchronous rotating coordinate system is further obtained:

[0050] in, = + , , ; = + , , ; and This is the positive sequence current adjustment signal; and This is a negative sequence current regulation signal.

[0051] In one feasible implementation, the positive-sequence voltage is the component of the three-phase voltage that is in phase with the fundamental voltage. When the three-phase grid voltage is unbalanced, the positive-sequence voltage regulation signal is obtained based on the symmetrical component analysis of the three-phase voltage. Through Fourier transform or the symmetrical component method, the unbalanced three-phase voltage is decomposed into positive-sequence, negative-sequence, and zero-sequence components. The positive-sequence voltage regulation signal reflects the amplitude and phase changes of the positive-sequence voltage. When the positive-sequence voltage deviates from its rated value, the positive-sequence voltage regulation signal triggers a corresponding control mechanism, such as adjusting the generator's excitation current or the transformer's tap changer, to restore the positive-sequence voltage to the normal range.

[0052] In one feasible implementation, negative sequence voltage is the component of the three-phase voltage that is 180 degrees out of phase with the fundamental voltage. Under voltage imbalance conditions, the presence of negative sequence voltage can lead to abnormal operation of power equipment. The acquisition of the negative sequence voltage regulation signal is based on the analysis of the symmetrical components of the three-phase voltage. The negative sequence voltage regulation signal is mainly used to detect and handle asymmetrical faults in the power grid. When the negative sequence voltage exceeds a certain threshold, the regulation signal will activate protective devices, such as negative sequence overcurrent protection, to disconnect the faulty component and prevent equipment damage. Simultaneously, the negative sequence voltage regulation signal can also be used to adjust reactive power compensation devices to reduce the impact of negative sequence voltage on the power grid.

[0053] In one feasible implementation, the positive sequence current is the component of the three-phase current that is in phase with the fundamental current. The positive sequence current regulation signal is obtained based on the measurement and analysis of the three-phase currents. The three-phase current signals are acquired through current transformers and processed to obtain the amplitude and phase information of the positive sequence current. The positive sequence current regulation signal is mainly used to control the generator's output power and the power flow distribution of the power grid. When the grid load changes, the positive sequence current regulation signal adjusts the active and reactive power output of the generator to maintain the frequency and voltage stability of the power grid.

[0054] In one feasible implementation, negative sequence current is the component of the three-phase current that is 180 degrees out of phase with the fundamental current. The presence of negative sequence current can lead to problems such as generator rotor overheating and increased vibration, affecting the generator's service life. The negative sequence current regulation signal is obtained based on the symmetrical component analysis of the three-phase current. The negative sequence current regulation signal is mainly used to limit the magnitude of the negative sequence current and protect power equipment. When the negative sequence current exceeds the allowable value, the regulation signal will take measures, such as adjusting the generator's phase sequence or activating a negative sequence current filter, to reduce the impact of the negative sequence current on the generator.

[0055] S202, determine the AC side current reference signal of the three-phase power grid based on the input power, positive sequence voltage regulation signal and negative sequence voltage regulation signal of the three-phase power grid.

[0056] In one feasible implementation, the input power of a three-phase power grid is obtained based on the product of the three-phase voltages and currents. The input power is then distributed to each of the three phases according to the required input power. In some scenarios, the input power of a three-phase power grid includes active power P, reactive power Q, and apparent power S. Active power P is the power that actually does work and is related to the in-phase components of the voltage and current; reactive power Q is used to establish and maintain the magnetic field and is related to the quadrature components of the voltage and current; apparent power is the vector sum of active and reactive power. According to the power formula... , (in Let V be the voltage between any two phase lines. Let be the current between any two phase lines. (Power factor angle) Given the input power and line voltage, the magnitude of the line current can be preliminarily estimated.

[0057] In one feasible implementation, the positive-sequence voltage regulation signal is used to maintain the stability of the positive-sequence voltage in a three-phase power grid. In a symmetrical three-phase power grid, the positive-sequence voltage is the dominant voltage component, and its magnitude and phase determine the normal operating state of the grid. By adjusting the positive-sequence voltage regulation signal, the magnitude and phase of the positive-sequence voltage can be changed, thereby affecting the current distribution. According to the symmetrical component method, the positive-sequence voltage and positive-sequence current satisfy the following relationship: Positive-sequence voltage = Positive-sequence current × Positive-sequence impedance. When the positive-sequence voltage regulation signal changes, the positive-sequence voltage changes, and to maintain the voltage-impedance relationship, the positive-sequence current also changes accordingly. Therefore, the positive-sequence voltage regulation signal can serve as an important basis for determining the positive-sequence current reference signal.

[0058] In one feasible implementation, the negative-sequence voltage regulation signal is mainly used to suppress negative-sequence components in a three-phase power grid. The presence of negative-sequence components leads to grid imbalance, affects the normal operation of electrical equipment, and increases grid losses. The negative-sequence voltage and negative-sequence current satisfy the following relationship: negative-sequence voltage = negative-sequence current × negative-sequence impedance. By adjusting the negative-sequence voltage regulation signal, the phase and magnitude of the negative-sequence voltage can be changed, thereby suppressing the generation of negative-sequence current. In some scenarios, when a large negative-sequence current is detected in the grid, the phase difference between the negative-sequence voltage and negative-sequence current can be changed by adjusting the negative-sequence voltage regulation signal, thus reducing the amplitude of the negative-sequence current. When determining the AC side current reference signal, the influence of the negative-sequence voltage regulation signal on the negative-sequence current must be considered, and the limitation of the negative-sequence current should be incorporated into the determination process of the current reference signal to ensure the balanced operation of the power grid.

[0059] In one feasible implementation, a positive-sequence current reference signal can be determined based on the positive-sequence voltage regulation signal and the positive-sequence impedance, wherein the positive-sequence current reference signal = positive-sequence voltage regulation signal / positive-sequence impedance. Similarly, a negative-sequence current reference signal can be determined based on the negative-sequence voltage regulation signal and the negative-sequence impedance, wherein the negative-sequence current reference signal = negative-sequence voltage regulation signal / negative-sequence impedance. The positive-sequence current reference signals and the negative-sequence current reference signals are then vector-synthesized to obtain the AC side current reference signal of the three-phase power grid.

[0060] S203 determines the AC side reference voltage based on the positive sequence current regulation signal, the negative sequence current regulation signal, and the AC side current reference signal of the three-phase power grid.

[0061] In one feasible implementation, the positive sequence voltage reference signal is determined based on the positive sequence current regulation signal and the three-phase power grid AC side current reference signal.

[0062] In some embodiments, the proportional gain and integral gain of the grid-side d-axis current loop are determined based on the input power of the three-phase grid. The positive-sequence voltage reference signal is determined based on the positive-sequence voltage regulation signal, the AC-side current reference signal of the three-phase grid, the proportional gain of the d-axis current loop, and the integral gain of the d-axis current loop.

[0063] As an example, the positive-sequence voltage reference signal is determined based on the following relationship:

[0064] in, , This is the positive sequence voltage reference signal. , This is a positive sequence voltage regulation signal. This is the proportional gain of the d-axis current loop. Let be the integral gain of the d-axis current loop. , This refers to the positive-sequence component of the AC-side current reference signal in a three-phase power grid. , This is the positive sequence current adjustment signal. Let be the inductive reactance of the inductor in a three-phase power grid, and s represent a complex variable in the complex frequency domain (also known as the s-domain or Laplace domain).

[0065] In one feasible implementation, the negative sequence voltage reference signal is determined based on the negative sequence current adjustment signal and the three-phase power grid AC side current reference signal.

[0066] In some embodiments, the negative sequence voltage reference signal is determined based on the negative sequence voltage regulation signal, the three-phase power grid AC side current reference signal, the negative sequence current regulation signal, the proportional gain of the d-axis current loop, and the integral gain of the d-axis current loop.

[0067] As an example, the negative sequence voltage reference signal is determined based on the following relationship:

[0068] in, , This is a negative sequence voltage reference signal. , It is a negative sequence voltage regulation signal. This is the proportional gain of the d-axis current loop. Let be the integral gain of the d-axis current loop. , This refers to the negative sequence component in the AC side current reference signal of a three-phase power grid. , This is a negative sequence current regulation signal.

[0069] It should be noted that the positive sequence voltage reference signal is obtained based on the positive sequence current inner loop feedforward interface control algorithm of the grid-side converter, and the negative sequence voltage reference signal is obtained based on the negative sequence current inner loop feedforward interface control algorithm of the grid-side converter.

[0070] In one feasible implementation, the positive-sequence voltage reference signal and the negative-sequence voltage reference signal are vector-synthesized to obtain the AC side reference voltage.

[0071] In some embodiments, the AC side reference voltage is determined based on the following relationship:

[0072] in, This is the AC side reference voltage.

[0073] S204 determines the bridge AC input voltage control signal used to regulate the unbalanced state based on the AC side reference voltage.

[0074] In one feasible implementation, the instantaneous DC-side voltage is determined based on the input power of the three-phase power grid. A bridge AC input voltage control signal for adjusting the imbalance is then determined based on the instantaneous DC-side voltage and the AC-side reference voltage.

[0075] In some embodiments, the input power of the three-phase power grid is typically equal to the output power on the DC side, and the instantaneous DC voltage is determined by the DC output power. The instantaneous DC voltage and the AC reference voltage are vector-synthesized to obtain a voltage control signal. This voltage control signal is used for space vector PWM modulation (SPPWM), and a corresponding switching signal is obtained based on the SPPWM modulation. This switching signal controls the on / off switching of devices in the three-phase power grid, enabling the converters in the three-phase power grid to operate based on a preset power factor, thereby suppressing the negative sequence current on the AC side.

[0076] In summary, the unbalanced control method for the grid-side converter of the wind turbine provided in this application, by acquiring positive-sequence voltage regulation signals, negative-sequence voltage regulation signals, positive-sequence current regulation signals, and negative-sequence current regulation signals on the grid side, can specifically address situations where the three-phase grid voltage is unbalanced. This helps improve the operational quality of the grid and reduce the negative impacts of increased equipment losses and reduced operating efficiency caused by voltage imbalance. The three-phase grid AC-side current reference signal is determined based on the input power of the three-phase grid and the positive-sequence and negative-sequence voltage regulation signals. This calculation method, which integrates multiple factors, makes the acquisition of the three-phase grid AC-side current reference signal more accurate, providing a reliable basis for subsequent regulation and control. The AC-side reference voltage is determined based on the positive-sequence and negative-sequence current regulation signals and the three-phase grid AC-side current reference signal, making the AC-side voltage control more reasonable, better adaptable to grid voltage imbalance conditions, and ensuring stable grid operation. The bridge AC input voltage control signal for regulating the unbalanced state is determined based on the AC side reference voltage. The bridge AC input voltage is precisely regulated by this control signal, thereby effectively regulating the voltage imbalance state of the power grid and improving the stability and reliability of the power grid.

[0077] Figure 3 This is a flowchart illustrating another unbalanced control method for a wind turbine grid-side converter provided in an embodiment of this application.

[0078] like Figure 3 As shown, the method includes, but is not limited to, the following steps: S301, in response to the unbalanced state of the three-phase grid voltage, obtains the positive sequence voltage, negative sequence voltage, positive sequence current and negative sequence current based on the grid side.

[0079] In one feasible implementation, Figure 4 This is a schematic diagram of the unbalanced control model of the grid-side converter of a wind turbine generator according to an embodiment of this application. Figure 4 As shown, the voltages (including Ua, Ub, and Uc) in a three-phase power grid are separated into positive-sequence and negative-sequence voltages through a voltage positive-negative-sequence separation operation. The currents (including Ia, Ib, and Ic) in a three-phase power grid are separated into positive-sequence and negative-sequence currents through a current positive-negative-sequence separation operation.

[0080] It should be noted that, since the three-phase power grid voltage is unbalanced, the current component is obtained based on the input power of the three-phase power grid (input power = voltage × current).

[0081] S302 performs coordinate transformation on the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current to obtain the positive-sequence voltage adjustment signal, negative-sequence voltage adjustment signal, positive-sequence current adjustment signal, and negative-sequence current adjustment signal.

[0082] In one feasible implementation, such as Figure 4 As shown, a 3s / 2r coordinate transformation is performed on the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current to obtain the positive-sequence voltage regulation signal. and Negative sequence voltage regulation signal and Positive sequence current regulation signal and Negative sequence current regulation signal and .

[0083] It should be noted that, as Figure 4 As shown, during the 3s / 2r coordinate transformation, the positive sequence voltage regulation signal... After passing through a phase-locked loop, its phase θ is thus achieved. + It maintains phase consistency with the three-phase power grid.

[0084] S303 determines the reference average value of active power, the reference average value of reactive power, the reference peak value of the second active cosine harmonic, and the reference peak value of the second active sine harmonic based on the input power of the three-phase power grid.

[0085] In one feasible implementation, when the three-phase grid voltage is in an unbalanced state, its input apparent complex power S can be described as:

[0086] The derivation of the input apparent complex power S is as follows:

[0087] Based on the above expression, we get and The expression:

[0088] in, This represents the average value of active power. This represents the average value of reactive power. The peak value of the second active cosine harmonic. The peak value of the second active sinusoidal harmonic is... The peak value of the second reactive cosine harmonic. It represents the peak value of the second reactive sinusoidal harmonic.

[0089] right , , , , , Further elaboration yields:

[0090] In one feasible implementation, since the coefficients of the active cosine and reactive cosine are the same, and the coefficients of the active sine and reactive sine are the same, in the process of determining the reference signal for the AC side current of the three-phase power grid, the following will be used: , , , , , The power equation is transformed into the following relationship:

[0091] in, This is the reference average value of active power. This is the reference average value for reactive power. For the second active cosine harmonic reference peak value, This is the reference peak value for the second active sinusoidal harmonic.

[0092] S304 determines the AC side current reference signal of the three-phase power grid based on the positive sequence voltage regulation signal, negative sequence voltage regulation signal, active power reference average value, reactive power reference average value, second active cosine harmonic reference peak value, and second active sine harmonic reference peak value.

[0093] In one feasible implementation, the product obtained in step S303 , , and By inverting the relation, we obtain the AC side current reference signal of the three-phase power grid. The expression for the AC side current reference signal of the three-phase power grid is as follows:

[0094] in, and This refers to the positive-sequence component of the AC-side current reference signal in a three-phase power grid. and It is the negative sequence component in the AC side current reference signal of a three-phase power grid.

[0095] In one feasible implementation, in order to suppress the negative sequence AC current of the grid-side converter under three-phase grid imbalance conditions, it is typically set that... and Since both are 0, the following relationship is obtained:

[0096] Among them, satisfying .

[0097] In one feasible implementation, such as Figure 4 As shown, This represents the reference average value of active power, if the DC voltage of the grid-side converter... When using PI control (proportional-integral control), the reference value of the DC current of the grid-side converter is obtained. DC current reference value The expression is:

[0098] in, It is the proportional control coefficient of PI regulation. It is the integral control coefficient of PI regulation. It is the preset DC voltage reference value.

[0099] Furthermore, the reference average value of active power is obtained. The expression:

[0100] S305 determines the positive sequence voltage reference signal based on the positive sequence current adjustment signal and the AC side current reference signal of the three-phase power grid.

[0101] S306, determine the negative sequence voltage reference signal based on the negative sequence current adjustment signal and the three-phase power grid AC side current reference signal.

[0102] S307 determines the AC side reference voltage based on the positive sequence voltage reference signal and the negative sequence voltage reference signal.

[0103] S308 determines the bridge AC input voltage control signal used to regulate the unbalanced state based on the AC side reference voltage.

[0104] In one feasible implementation, such as Figure 4 As shown, in the positive sequence controller, the positive sequence voltage reference signal and After a 2s / 2r coordinate transformation, the parameter values ​​in the two-phase stationary coordinate system are obtained. In the negative sequence controller, the negative sequence voltage reference signal... and After a 2s / 2r coordinate transformation, the parameter values ​​in the two-phase stationary coordinate system are obtained. These two parameter values ​​are then summed before space vector PWM modulation is performed.

[0105] For further details on steps S305 to S308, please refer to the relevant descriptions in the above embodiments, which will not be repeated here.

[0106] In summary, the unbalanced control method for the grid-side converter of the wind turbine provided in this application, by acquiring positive-sequence voltage regulation signals, negative-sequence voltage regulation signals, positive-sequence current regulation signals, and negative-sequence current regulation signals on the grid side, can specifically address situations where the three-phase grid voltage is unbalanced. This helps improve the operational quality of the grid and reduce the negative impacts of increased equipment losses and reduced operating efficiency caused by voltage imbalance. The three-phase grid AC-side current reference signal is determined based on the input power of the three-phase grid and the positive-sequence and negative-sequence voltage regulation signals. This calculation method, which integrates multiple factors, makes the acquisition of the three-phase grid AC-side current reference signal more accurate, providing a reliable basis for subsequent regulation and control. The AC-side reference voltage is determined based on the positive-sequence and negative-sequence current regulation signals and the three-phase grid AC-side current reference signal, making the AC-side voltage control more reasonable, better adaptable to grid voltage imbalance conditions, and ensuring stable grid operation. The bridge AC input voltage control signal for regulating the unbalanced state is determined based on the AC side reference voltage. The bridge AC input voltage is precisely regulated by this control signal, thereby effectively regulating the voltage imbalance state of the power grid and improving the stability and reliability of the power grid.

[0107] Corresponding to the unbalance control method for the grid-side converter of a wind turbine, this application also provides an unbalance control device for the grid-side converter of a wind turbine. Since the embodiments of the unbalance control device for the grid-side converter of a wind turbine correspond to the embodiments of the unbalance control method for the grid-side converter of a wind turbine, details not disclosed in the embodiments of the unbalance control device for the grid-side converter of a wind turbine can be referred to the embodiments of the unbalance control method for the grid-side converter of a wind turbine, and will not be repeated in this application.

[0108] In one feasible implementation, the unbalance control device of the wind turbine grid-side converter is configured to execute the steps of the unbalance control method for the wind turbine grid-side converter as provided in the embodiments of this application. This unbalance control device has specific functional modules, algorithms, or logic, and is capable of determining the bridge AC input voltage control signal for adjusting the unbalanced state based on a series of steps, rules, and strategies of the unbalance control method for the wind turbine grid-side converter described in the embodiments of this application.

[0109] In one feasible implementation, by writing specific program code, the unbalanced control method of the wind turbine grid-side converter is transformed into instructions that the unbalanced control device of the wind turbine grid-side converter can understand and execute. These program codes may include logic such as condition judgment, loop control, and data processing to determine the bridge AC input voltage control signal used to regulate the unbalanced state.

[0110] Figure 5 This is a schematic diagram of the structure of an electronic device provided according to an embodiment of this application. Figure 5 The electronic device shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0111] like Figure 5 As shown, the electronic device 500 includes a processor 501, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 502 or a program loaded from memory 506 into a random access memory (RAM) 503. The RAM 503 also stores various programs and data required for the operation of the electronic device 500. The processor 501, ROM 502, and RAM 503 are interconnected via a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0112] The following components are connected to I / O interface 505: memory 506 including hard disks, etc.; and communication section 507 including network interface cards such as LAN (Local Area Network) cards, modems, etc., which performs communication processing via a network such as the Internet; and driver 508 is also connected to I / O interface 505 as needed.

[0113] Specifically, according to embodiments of this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this application include a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 507. When the computer program is executed by processor 501, it performs the functions defined in the methods of this application.

[0114] In an exemplary embodiment, a storage medium including instructions is also provided, such as a memory including instructions, which can be executed by the processor 501 of the electronic device 500 to perform the above-described method. Optionally, the storage medium may be a non-transitory computer-readable storage medium, such as a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device.

[0115] In this application, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium, which can transmit, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wireline, optical fiber, RF, etc., or any suitable combination thereof.

[0116] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0117] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. An unbalanced control method for a grid-side converter of a wind turbine generator, characterized in that, include: In response to the unbalanced state of the three-phase grid voltage, positive sequence voltage regulation signal, positive sequence current regulation signal and negative sequence current regulation signal are obtained from the grid side; The AC side current reference signal of the three-phase power grid is determined based on the input power of the three-phase power grid, the positive sequence voltage regulation signal, and the negative sequence voltage regulation signal. The AC side reference voltage is determined based on the positive sequence current adjustment signal, the negative sequence current adjustment signal, and the three-phase power grid AC side current reference signal. The bridge AC input voltage control signal for adjusting the unbalanced state is determined based on the AC side reference voltage.

2. The method according to claim 1, characterized in that, The response to the three-phase grid voltage being in an unbalanced state, based on positive-sequence voltage regulation signals, negative-sequence voltage regulation signals, positive-sequence current regulation signals, and negative-sequence current regulation signals obtained from the grid side, includes: In response to the unbalanced state of the three-phase grid voltage, positive sequence voltage, negative sequence voltage, positive sequence current, and negative sequence current are obtained from the grid side; The positive-sequence voltage, the negative-sequence voltage, the positive-sequence current, and the negative-sequence current are subjected to coordinate transformation to obtain the positive-sequence voltage adjustment signal, the negative-sequence voltage adjustment signal, the positive-sequence current adjustment signal, and the negative-sequence current adjustment signal.

3. The method according to claim 1, characterized in that, The step of determining the AC side current reference signal of the three-phase power grid based on the input power of the three-phase power grid, the positive sequence voltage regulation signal, and the negative sequence voltage regulation signal includes: The reference average value of active power, the reference average value of reactive power, the reference peak value of second active cosine harmonic, and the reference peak value of second active sine harmonic are determined based on the input power of the three-phase power grid. The reference signal for the AC side current of the three-phase power grid is determined based on the positive sequence voltage regulation signal, the negative sequence voltage regulation signal, the reference average value of active power, the reference average value of reactive power, the reference peak value of the second active cosine harmonic, and the reference peak value of the second active sine harmonic.

4. The method according to claim 1, characterized in that, The step of determining the AC side reference voltage based on the positive sequence current adjustment signal, the negative sequence current adjustment signal, and the three-phase power grid AC side current reference signal includes: The positive sequence voltage reference signal is determined based on the positive sequence current adjustment signal and the three-phase power grid AC side current reference signal. The negative sequence voltage reference signal is determined based on the negative sequence current adjustment signal and the three-phase power grid AC side current reference signal. The AC side reference voltage is determined based on the positive sequence voltage reference signal and the negative sequence voltage reference signal.

5. The method according to claim 4, characterized in that, The step of determining the positive sequence voltage reference signal based on the positive sequence current adjustment signal and the three-phase power grid AC side current reference signal includes: The proportional gain and integral gain of the d-axis current loop on the grid side are determined based on the input power of the three-phase power grid. The positive sequence voltage reference signal is determined based on the positive sequence voltage adjustment signal, the AC side current reference signal of the three-phase power grid, the positive sequence current adjustment signal, the proportional gain of the d-axis current loop, and the integral gain of the d-axis current loop.

6. The method according to claim 5, characterized in that, Determining the negative sequence voltage reference signal based on the negative sequence current regulation signal and the three-phase power grid AC side current reference signal includes: The negative sequence voltage reference signal is determined based on the negative sequence voltage adjustment signal, the AC side current reference signal of the three-phase power grid, the negative sequence current adjustment signal, the proportional gain of the d-axis current loop, and the integral gain of the d-axis current loop.

7. The method according to claim 1, characterized in that, The step of determining the bridge AC input voltage control signal for adjusting the unbalanced state based on the AC side reference voltage includes: The instantaneous DC voltage is determined based on the input power of the three-phase power grid; The bridge AC input voltage control signal for adjusting the unbalanced state is determined based on the instantaneous DC side voltage and the AC side reference voltage.

8. An unbalance control device for a grid-side converter of a wind turbine generator, characterized in that, The steps are configured to implement the method of any one of claims 1 to 7.

9. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having computer program instructions stored thereon, characterized in that, When executed by a processor, the program instructions implement the steps of the method according to any one of claims 1 to 7.

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