Virtual impedance-based power decoupling control method and system for wind power converter

Abstract

The application discloses a wind power converter power decoupling control method and system based on virtual impedance, which realizes accurate decoupling of positive and negative sequence components by performing sequence component decomposition and double synchronous coordinate system transformation on grid voltage and converter current; further introduces independent adaptive virtual impedance voltage drop calculation, dynamically adjusts virtual impedance parameters according to grid unbalance degree, actively compensates phase shift caused by inherent delay of a digital control system, further avoids high-frequency instability, and provides accurate input for double-channel instruction voltage generation. In this way, the wind power converter can reliably operate under complex grid conditions, and the wind power grid connection performance and grid adaptability are improved.

Description

Technical Field

[0001] This application relates to the field of intelligent control, and more specifically, to a power decoupling control method and system for wind power converters based on virtual impedance. Background Technology

[0002] With the increasing global demand for renewable energy, wind power has become an important component of modern power systems. As a key device connecting wind turbine generators to the power grid, the performance of wind power converters directly affects the stable operation of the grid and power quality. However, the actual power grid environment is complex and variable, with frequent grid disturbances such as voltage imbalance and harmonic pollution. These non-ideal operating conditions cause fluctuations in the output power of wind power converters, severely impacting their grid connection performance and system stability. Currently, the power electronics field has proposed various power decoupling control schemes for wind power converters, aiming to optimize their performance under complex grid conditions. Among them, virtual impedance technology, due to its ability to flexibly modify the external characteristics of the converter and enhance the impedance matching capability between the system and the grid, is considered an effective solution, playing a positive role in suppressing grid resonance, improving power quality, and enhancing system stability.

[0003] However, applying virtual impedance-based control strategies to practical digital control systems faces significant technical challenges. The inherent delays in digital control systems, including processing delays in current acquisition, controller calculation delays, and PWM signal update delays, accumulate and severely impact the actual effectiveness of virtual impedance, introducing a non-negligible phase shift in the control loop. Particularly under high-frequency conditions, this phase shift can lead to system instability at high frequencies, or even trigger high-frequency oscillations. Traditional virtual impedance designs are often based on ideal continuous-time system models, failing to adequately consider or effectively compensate for the impact of these digital control delays on system dynamic performance, resulting in a significant gap between theoretical design and practical application. This interaction between the delay effect and virtual impedance greatly limits the configuration range of virtual impedance parameters and the improvement of overall system dynamic performance.

[0004] Therefore, an optimized power decoupling control method for wind power converters based on virtual impedance is desired. Summary of the Invention

[0005] To address the aforementioned technical problems, this application is proposed. Embodiments of this application provide a power decoupling control method and system for wind power converters based on virtual impedance. This method achieves precise decoupling of positive and negative sequence components by performing sequence component decomposition and dual-synchronous coordinate system transformation on the grid voltage and converter current. Furthermore, it introduces independent adaptive virtual impedance voltage drop calculation, dynamically adjusting the virtual impedance parameters according to the grid imbalance to actively compensate for the phase shift caused by the inherent delay of the digital control system, thereby avoiding high-frequency instability and providing accurate input for dual-channel command voltage generation. In this way, reliable operation of the wind power converter is ensured under complex grid conditions, improving wind power grid connection performance and grid adaptability.

[0006] According to one aspect of this application, a power decoupling control method for a wind power converter based on virtual impedance is provided, comprising: Sequence component decomposition is performed on the three-phase voltage of the power grid and the three-phase current of the converter to obtain the positive sequence. Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive sequence fundamental frequency and grid positive sequence fundamental phase angle; Based on the positive-sequence fundamental phase angle of the power grid, for the positive-sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current is transformed using a dual synchronous coordinate system to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. Based on the positive-sequence fundamental angular frequency of the power grid, independent adaptive virtual impedance voltage drop calculations are performed on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current to obtain the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop. Dual-channel command voltage generation is performed based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage; Based on the positive-sequence fundamental phase angle of the power grid, the command voltages of the positive-sequence dq converter and the negative-sequence dq converter are synthesized and PWM signals are generated to obtain the three-phase PWM drive signal. According to another aspect of this application, a wind power converter power decoupling control system based on virtual impedance is provided, comprising: The sequence component decomposition module is used to perform sequence component decomposition on the three-phase voltage of the power grid and the three-phase current of the converter to obtain the positive sequence. Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive sequence fundamental frequency and grid positive sequence fundamental phase angle; The dual-synchronous coordinate system transformation module is used to transform the positive-sequence fundamental phase angle of the power grid. Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current is transformed using a dual synchronous coordinate system to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. The independent adaptive virtual impedance voltage drop calculation module is used to perform independent adaptive virtual impedance voltage drop calculations on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current based on the positive-sequence fundamental frequency of the grid to obtain the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop. A dual-channel command voltage generation module is used to generate dual-channel command voltages based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage. The PWM signal generation module is used to synthesize the command voltage of the positive-sequence dq converter and the command voltage of the negative-sequence dq converter based on the positive-sequence fundamental phase angle of the power grid, and generate a PWM signal to obtain a three-phase PWM drive signal.

[0007] Compared with existing technologies, this application provides a power decoupling control method and system for wind power converters based on virtual impedance. It achieves precise decoupling of positive and negative sequence components by performing sequence component decomposition and dual-synchronous coordinate system transformation on the grid voltage and converter current. Furthermore, it introduces independent adaptive virtual impedance voltage drop calculation, dynamically adjusting the virtual impedance parameters according to the grid imbalance to actively compensate for the phase shift caused by the inherent delay of the digital control system, thereby avoiding high-frequency instability and providing accurate input for dual-channel command voltage generation. In this way, it ensures reliable operation of the wind power converter under complex grid conditions, improving wind power grid connection performance and grid adaptability. Attached Figure Description

[0008] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0009] Figure 1This is a flowchart of a wind power converter power decoupling control method based on virtual impedance according to an embodiment of this application; Figure 2 This is a data flow diagram of the power decoupling control method for wind power converter based on virtual impedance according to an embodiment of this application; Figure 3 This is a block diagram of a wind power converter power decoupling control system based on virtual impedance according to an embodiment of this application. Detailed Implementation

[0010] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0011] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0012] While this application makes various references to certain modules of the systems according to embodiments of this application, any number of different modules can be used and run on user terminals and / or servers. The modules described are merely illustrative, and different aspects of the systems and methods may use different modules.

[0013] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously as needed. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0014] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0015] In the technical solution of this application, a power decoupling control method for wind power converters based on virtual impedance is proposed. Figure 1 This is a flowchart of a wind power converter power decoupling control method based on virtual impedance according to an embodiment of this application. Figure 2 This is a schematic diagram of the data flow in a wind power converter power decoupling control method based on virtual impedance according to an embodiment of this application. Figure 1 and Figure 2 As shown, the wind power converter power decoupling control method based on virtual impedance according to an embodiment of this application includes the following steps: S1, performing sequence component decomposition on the three-phase voltage of the grid and the three-phase current of the converter to obtain positive sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive-sequence fundamental angular frequency, and grid positive-sequence fundamental phase angle; S2, based on the grid positive-sequence fundamental phase angle, for the positive-sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current; S3, based on the positive-sequence fundamental frequency of the grid, independent adaptive virtual impedance voltage drop calculations are performed on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current to obtain the positive-sequence dq virtual voltage drop and negative-sequence dq virtual voltage drop; S4, based on the positive-sequence dq virtual voltage drop and negative-sequence dq virtual voltage drop, dual-channel command voltage generation is performed to obtain the positive-sequence dq converter command voltage and negative-sequence dq converter command voltage; S5, based on the positive-sequence fundamental phase angle of the grid, command voltage synthesis and PWM signal generation are performed on the positive-sequence dq converter command voltage and negative-sequence dq converter command voltage to obtain the three-phase PWM drive signal.

[0016] Specifically, S1 involves performing sequence component decomposition on the three-phase voltage of the power grid and the three-phase current of the converter to obtain the positive sequence. Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence The converter current, the positive-sequence fundamental frequency of the power grid, and the positive-sequence fundamental phase angle of the power grid are all factors to consider. It is understandable that in modern power systems, especially in wind power grid-connected scenarios, grid voltage often exhibits asymmetry and imbalance. This imbalance causes pulsations in the converter's output power, affecting power quality and system stability. By decomposing the three-phase voltage and current into positive-sequence and negative-sequence components, the power flows corresponding to the balanced and unbalanced components can be effectively separated. The positive-sequence component represents the normal operating state of the power grid and is mainly used for controlling active and reactive power; while the negative-sequence component reflects the unbalanced characteristics of the power grid, and its presence leads to power pulsations at twice the power frequency. Therefore, sequence component decomposition is the foundation for achieving precise power decoupling control. It provides the necessary input signals for subsequent independent control, thereby ensuring that the wind power converter can operate stably and efficiently under non-ideal grid conditions and output high-quality power.

[0017] In practice, firstly, the measured three-phase grid voltage and converter three-phase current are transformed from a three-phase (abc) coordinate system to a two-phase stationary system. Coordinate system. This transformation can be accomplished using the Clarke transformation, decoupling the three-phase signals into... shaft and Two orthogonal components on the axis; Next, regarding The voltage and current components in the coordinate system are extracted using advanced signal processing techniques (such as methods based on generalized integrator SOGI or delayed signal cancellation DSC) to obtain their positive and negative sequence components. This allows the original... The signal is decomposed into two components with opposite rotation directions, i.e., the forward sequence. Components and Negative Order Components. These components are in The coordinate system still contains alternating current quantities. For example, for a voltage signal, its positive sequence... The extraction of components can be achieved conceptually by using a combination of orthogonal component generators and filters to ensure accurate separation of the positive and negative order components of the fundamental frequency; Furthermore, in obtaining the forward order After component analysis, in order to perform coordinate transformation and control, it is also necessary to accurately estimate the angular frequency and instantaneous phase angle of the positive-sequence fundamental frequency of the power grid. This is typically achieved using phase-locked loop (PLL) technology. A PLL can track the positive-sequence fundamental frequency. The voltage phasor is output in real time, providing its instantaneous angular frequency and phase, thus providing a precise reference for subsequent synchronous coordinate system transformations. Through the above steps, all the necessary input signals for power decoupling control are finally obtained, i.e., the positive sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive sequence fundamental frequency and grid positive sequence fundamental phase angle.

[0018] Specifically, S2, based on the positive-sequence fundamental phase angle of the power grid, performs a positive-sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current undergoes a dual-synchronous coordinate system transformation to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. It should be understood that although sequence component decomposition has separated the grid imbalance components into positive and negative sequences, these components are still AC quantities in the αβ stationary coordinate system, and their instantaneous values ​​change periodically with time, introducing significant complexity to controller design. The introduction of synchronous rotating dq coordinate system transformation can further convert these AC quantities into DC quantities, thereby greatly simplifying controller design. In the dq coordinate system, the active and reactive power of the wind power converter can achieve complete or near-complete decoupling control, allowing the controller to independently adjust them, improving control accuracy and response speed. For the negative-sequence component, it is also converted into a DC quantity through a specific dual-synchronous coordinate system transformation, which can conveniently detect and suppress double-frequency power pulsations caused by grid voltage imbalance, thereby eliminating wind power converter power fluctuations at the source and significantly improving grid-connected power quality.

[0019] In practice, the dual-synchronous coordinate system transformation is performed based on the fact that the positive-sequence fundamental phase angle pairs of the power grid belong to the positive and negative sequences, respectively. The components are converted. Specifically, based on the positive-sequence fundamental phase angle of the power grid, the positive-sequence phase is converted using the following formula. Grid voltage or positive sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain either the positive-sequence dq grid voltage or the positive-sequence dq converter current, wherein the formula is:

[0020] in, The positive sequence fundamental phase angle of the power grid. Forward order Grid voltage or positive sequence Converter current, The positive-sequence dq grid voltage or the positive-sequence dq converter current; Based on the positive-sequence fundamental phase angle of the power grid, the negative-sequence phase angle is calculated using the following formula. Grid voltage or negative sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain the negative-sequence dq grid voltage or the negative-sequence dq converter current, as shown in the formula:

[0021] in, negative order Grid voltage or negative sequence Converter current, The negative sequence dq is the grid voltage or the negative sequence dq is the converter current.

[0022] Specifically, S3, based on the positive-sequence fundamental angular frequency of the power grid, performs independent adaptive virtual impedance voltage drop calculations on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current to obtain the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop. It should be understood that traditional converter control typically assumes ideal grid conditions, but in actual grid-connected operation, the complexity and uncertainties of the grid, such as voltage imbalance and high-frequency resonance, can threaten the stability and power quality of the converter. Virtual impedance technology can effectively change the output impedance characteristics of the converter by introducing virtual resistance and inductance effects into the control algorithm, thereby enhancing its ability to suppress grid disturbances and improving the voltage and current quality at the grid connection point. More importantly, through an independent adaptive mechanism, the virtual impedance parameters can be dynamically adjusted according to the real-time grid imbalance, enabling it to perform optimally under different operating conditions. It provides a key compensation method, particularly in suppressing high-frequency instability and mitigating the negative impact of inherent delays in digital control, to achieve more robust and stable power control.

[0023] In practical implementation, firstly, the grid imbalance is assessed and the virtual impedance parameters are dynamically determined for both the positive-sequence (dq) and negative-sequence (dq) grid voltages to obtain the currently effective positive-sequence and negative-sequence virtual impedance parameters. It should be understood that grid voltage imbalance in actual power systems is not static but dynamically changes with load variations, fault modes, and other factors. Using fixed virtual impedance parameters may not achieve optimal control performance under all operating conditions. For example, when the grid imbalance is high, a larger virtual impedance is needed to provide stronger suppression to limit negative-sequence current and power ripple; while when the grid is relatively balanced, an excessively large virtual impedance may introduce unnecessary voltage drops, affecting power transmission efficiency and even causing new stability problems. Furthermore, considering the inherent delay effect of digital control systems, traditional fixed virtual impedance may lead to high-frequency instability at high frequencies. By assessing the grid imbalance in real time and dynamically adjusting the virtual impedance parameters, it can be ensured that the virtual impedance strategy always matches the current grid conditions, thereby achieving optimal performance in suppressing power ripple, enhancing system stability, dynamically compensating for the delay effects of digital control, and improving power quality.

[0024] Specifically, firstly, the voltage component amplitudes of the positive-sequence dq grid voltage and the negative-sequence dq grid voltage are calculated to obtain the positive-sequence dq grid voltage vector amplitude and the negative-sequence dq grid voltage vector amplitude. It should be understood that accurately quantifying the degree of grid voltage imbalance is a prerequisite for achieving adaptive adjustment of the virtual impedance parameters. In the dq synchronous rotating coordinate system, both the positive-sequence dq grid voltage and the negative-sequence dq grid voltage are represented as DC quantities, and their amplitudes are key indicators for measuring their magnitude. By calculating these voltage vector amplitudes, the actual strength of the balanced and unbalanced components in the grid can be directly determined. These amplitudes are then used to calculate the voltage imbalance factor, which serves as input to the parameter decision engine, thereby dynamically adjusting the virtual impedance parameters. Therefore, accurately obtaining these two amplitudes is the starting point of the entire adaptive control strategy and directly relates to the system's adaptability to grid imbalance and the quality of its control effect.

[0025] Specifically, firstly, for the positive-sequence dq grid voltage, the principle for calculating its vector magnitude is as follows: Square the component of the positive-sequence dq grid voltage along the d-axis of the synchronously rotating dq coordinate system, and simultaneously square its component along the q-axis of the synchronously rotating dq coordinate system; then add these two squared values, and finally perform a square root operation on the sum to obtain the vector magnitude of the positive-sequence dq grid voltage. Secondly, for the negative-sequence dq grid voltage, the principle for calculating its vector magnitude is similar to that of the positive-sequence voltage: Square the component of the negative-sequence dq grid voltage along the d-axis of the synchronously rotating dq coordinate system, and simultaneously square its component along the q-axis of the synchronously rotating dq coordinate system; then add these two squared values, and finally perform a square root operation on the sum to obtain the vector magnitude of the negative-sequence dq grid voltage. In the dq coordinate system, the voltage vector can be regarded as a complex number or a two-dimensional vector, and its magnitude is the magnitude of the vector. This process is usually implemented in a digital signal processor (DSP) or field-programmable gate array (FPGA) through mathematical operations such as squaring, summing, and square root operations. Next, based on the magnitudes of the positive-sequence dq grid voltage vector and the negative-sequence dq grid voltage vector, the voltage imbalance factor is calculated. It should be understood that the voltage imbalance factor is a direct and effective indicator for quantifying the degree of grid voltage imbalance. The operating conditions of the power grid are constantly changing, and the degree of voltage imbalance changes in real time with factors such as load access, distributed power generation output fluctuations, and short-circuit faults. If the control system cannot accurately sense and quantify this change, it may be unable to effectively adjust the virtual impedance parameters, resulting in insufficient or excessive virtual impedance. By calculating the voltage imbalance factor, a clear value representing the current grid voltage symmetry can be obtained. This value will serve as the direct basis for subsequent adaptive decisions regarding virtual impedance parameters. It enables the converter control strategy to respond intelligently to changes in grid conditions, thereby effectively suppressing power ripples and optimizing power output quality while maintaining system stability.

[0026] Specifically, the voltage imbalance factor is calculated using the following formula:

[0027] in, The magnitude of the negative-sequence dq grid voltage vector. The magnitude of the positive-sequence dq grid voltage vector; Furthermore, the voltage imbalance factor is input into the parameter decision engine to obtain the currently effective positive-sequence virtual impedance parameter and the currently effective negative-sequence virtual impedance parameter. The degree of grid voltage imbalance is not static but constantly adjusts with the dynamic changes in grid operating conditions. If the virtual impedance parameter uses a fixed value, it will not be able to adapt to grid changes, potentially leading to overcompensation when the grid imbalance is mild, thus affecting converter efficiency and control response; while when the grid imbalance is severe, insufficient compensation may fail to effectively suppress power ripples, and may even cause system instability. Therefore, by introducing a parameter decision engine and using the real-time calculated voltage imbalance factor as input, adaptive dynamic adjustment of the virtual impedance parameter can be achieved, ensuring that the virtual impedance compensation strategy always matches the current grid conditions, thereby providing optimal control performance throughout the entire operating range, including enhanced suppression of grid imbalance, improved system stability, and optimized power quality. This adaptive mechanism is also a key guarantee for addressing the inherent delay of digital control and avoiding high-frequency instability.

[0028] Here, the parameter decision engine is an intelligent module that dynamically adjusts the positive-sequence and negative-sequence virtual impedance parameters based on the magnitude of the voltage imbalance factor, using preset control strategies, lookup tables, or fuzzy logic rules. For example, when an increase in the voltage imbalance factor is detected (i.e., increased grid imbalance), the parameter decision engine may increase the value of the negative-sequence virtual impedance to provide stronger negative-sequence current suppression capability. Simultaneously, to enhance suppression capability without affecting normal active power transmission, the positive-sequence virtual impedance may also need to be adjusted accordingly to maintain system stability. The virtual impedance parameters generated in this way can maximize the role of virtual impedance and maintain optimal control performance under different grid operating conditions. Next, based on the currently effective positive-sequence virtual impedance parameters, the grid's positive-sequence fundamental angular frequency, and the positive-sequence dq converter current, the positive-sequence virtual voltage drop is calculated to obtain the positive-sequence dq virtual voltage drop. It should be understood that when a wind power converter is connected to the grid, its output impedance characteristics directly affect its interaction with the grid. When grid disturbances occur (such as voltage dips or harmonic pollution) or when there is a digital control delay within the system, the converter may struggle to maintain stable operation, and may even experience oscillations or power fluctuations. The introduction of positive-sequence virtual impedance aims to actively change the converter's output characteristics by adding an equivalent voltage drop to the control loop. This voltage drop is not an actual voltage loss, but a voltage component simulated by the control algorithm. It can enhance the converter's stability under normal operating conditions and improve its adaptability to the grid. Especially when inherent phase shifts are caused by digital control delays, the positive-sequence virtual impedance can be adjusted to toughen the system, ensuring high-quality positive-sequence power output at the grid connection point.

[0029] Specifically, the positive-sequence virtual voltage drop is calculated using the following formula:

[0030] in, For positive-order dq virtual voltage drop, The positive sequence fundamental angular frequency of the power grid. This represents the positive-sequence dq converter current. and The currently active positive-sequence virtual impedance parameter; Furthermore, based on the currently effective negative-sequence virtual impedance parameters, the positive-sequence fundamental angular frequency of the power grid, and the negative-sequence dq converter current, the negative-sequence virtual voltage drop is calculated to obtain the negative-sequence dq virtual voltage drop. It should be understood that under unbalanced grid conditions, in addition to providing stable active and reactive power, wind power converters also face the challenge of suppressing power ripples originating from negative-sequence voltage and the resulting system oscillation risks. Negative-sequence current and negative-sequence power are the main factors leading to deterioration of power quality at the grid connection point, increased equipment losses, and system instability. By strategically introducing negative-sequence virtual impedance in the control loop, an equivalent negative-sequence system impedance can be effectively created, thereby affecting the converter's response to negative-sequence voltage and current. This virtual voltage drop is equivalent to actively applying a voltage compensation related to the negative-sequence current at the converter output. Its purpose is to limit the flow of negative-sequence current by changing the converter's output characteristics in the negative-sequence loop, thereby suppressing power ripples at double the power frequency. By combining an adaptive parameter adjustment mechanism, the negative sequence virtual impedance can be ensured to perform at its best under different degrees of grid imbalance, thereby significantly improving the stability and power quality of the wind power grid-connected system.

[0031] Specifically, the negative-sequence virtual voltage drop is calculated using the following formula:

[0032] in, This represents the negative-sequence dq converter current. The positive sequence fundamental angular frequency of the power grid. and The currently active negative-sequence virtual impedance parameter. For negative-order dq virtual voltage drop.

[0033] Specifically, in step S4, a dual-channel command voltage generation is performed based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage. It should be understood that the power transmission performance of a wind power converter directly depends on its ability to precisely control the output voltage. In complex grid environments, especially with voltage imbalances, harmonics, and inherent delays in digital controllers, the converter needs to issue precise command voltages to effectively achieve independent control of active and reactive power, while suppressing power pulsations caused by grid imbalances. By integrating the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop calculated in the previous step into their respective control channels, the effects of grid disturbances can be actively offset, and the non-ideal characteristics within the system can be compensated. This dual-channel command voltage generation mechanism ensures that the converter can finely regulate the balanced and unbalanced components of the grid, thereby enhancing its grid adaptability, ensuring the stable and reliable operation of the power generation system, and outputting high-quality power.

[0034] In practical implementation, for the positive-sequence dq converter command voltage, the positive-sequence current reference value is first calculated based on the positive-sequence active power reference value and the positive-sequence reactive power reference value. This means that the controller will calculate the required positive-sequence d-axis current reference value and positive-sequence q-axis current reference value through the inverse power equation according to the active power reference value and reactive power reference value set by the system requirements. Then, the positive-sequence current reference value and the positive-sequence dq converter current are input into the positive-sequence current loop PI controller to obtain the positive-sequence voltage PI control term. In this process, the positive-sequence current loop PI controller receives the error between the calculated positive-sequence current reference value and the actual measured positive-sequence dq converter current. The PI controller generates a preliminary voltage control quantity, namely the positive-sequence dq voltage PI control term, through proportional and integral actions. Then, based on the positive-sequence voltage PI control term, the positive-sequence dq virtual voltage drop, and the positive-sequence dq grid voltage, the positive-sequence dq converter command voltage is determined. In the embodiments of this application, the positive sequence dq converter command voltage is obtained by calculating the sum of the positive sequence voltage PI control term, the positive sequence dq virtual voltage drop, and the positive sequence dq grid voltage. For the negative-sequence dq converter command voltage, firstly, the negative-sequence dq current reference value and the negative-sequence dq converter current are input to the output of the negative-sequence current loop PI controller to obtain the negative-sequence current PI control term. In typical power decoupling control, to suppress negative-sequence current and eliminate power ripple, the negative-sequence current reference value is usually set to zero. The negative-sequence current loop PI controller receives these reference values ​​and the error between them and the actual measured negative-sequence dq converter current, and similarly generates the negative-sequence dq voltage PI control term through proportional and integral actions; then, based on the negative-sequence current PI control term, the negative-sequence dq virtual voltage drop, and the negative-sequence dq grid voltage, the negative-sequence dq converter command voltage is determined. Similarly, the negative-sequence dq converter command voltage is obtained by calculating the sum of the negative-sequence current PI control term, the negative-sequence dq virtual voltage drop, and the negative-sequence dq grid voltage.

[0035] Specifically, in step S5, based on the positive-sequence fundamental phase angle of the power grid, the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage are synthesized into a command voltage and a PWM signal is generated to obtain a three-phase PWM drive signal. It should be understood that all previous control operations, including power decoupling, virtual impedance voltage drop calculation, and adjustment of each current loop, are performed in an abstract dq synchronous rotating coordinate system. These dq component voltage commands represent the voltage characteristics that the converter should output under balanced and unbalanced grid conditions. However, actual wind power converters are three-phase voltage source inverters composed of semiconductor devices such as IGBTs. The physical quantities they directly operate on are three-phase voltage and current, and the required output voltage is formed by controlling the on / off state of the switching devices. Therefore, in the technical solution of this application, the voltage command in the dq coordinate system is converted back to the actual three-phase AC voltage command, and further encoded into a pulse width modulation (PWM) signal to drive the switching devices, thereby generating an actual output voltage waveform that conforms to the control objective. This conversion process must not only ensure the accuracy of power transmission, but also consider how to generate electrical energy efficiently and with low loss, and effectively compensate for the digital control delay within the system to ensure the quality of the final output power and the stability of the system.

[0036] In practical implementation, firstly, command voltage synthesis is performed. Since both the positive-sequence and negative-sequence dq converter command voltages are represented in the same grid positive-sequence fundamental synchronous rotating coordinate system, the total dq converter command voltage can be obtained by simply superimposing the positive-sequence and negative-sequence components on their respective axes. Next, based on the grid positive-sequence fundamental phase angle, these total dq command voltages are converted back to voltage commands in the stationary two-phase coordinate system through inverse Park transformation. Then, PWM signal generation is performed. The obtained αβ-axis voltage commands are used as input signals for pulse width modulation (PWM). Typically, space vector pulse width modulation (SVPWM) technology is used to improve voltage utilization and reduce harmonic content. The SVPWM controller receives these two-phase command voltages, calculates the effective vector and zero vector duration (i.e., duty cycle) that the inverter should conduct in one switching cycle, and decomposes it into the switching time of each bridge arm. After logical processing, these switching times are finally output as three-phase PWM drive signals. These three-phase PWM drive signals directly control the on / off state of the converter power switching devices (such as IGBTs or MOSFETs), thereby forming an equivalent three-phase AC voltage waveform at the output, which can accurately follow the amplitude and phase set by the command voltage in the dq coordinate system, and contain the desired positive and negative sequence components to meet the requirements of active / reactive power control and negative sequence current suppression.

[0037] In summary, the wind power converter power decoupling control method based on virtual impedance according to the embodiments of this application is explained. It achieves precise decoupling of positive and negative sequence components by performing sequence component decomposition and dual-synchronous coordinate system transformation on the grid voltage and converter current. Furthermore, it introduces independent adaptive virtual impedance voltage drop calculation, dynamically adjusting the virtual impedance parameters according to the grid imbalance to actively compensate for the phase shift caused by the inherent delay of the digital control system, thereby avoiding high-frequency instability and providing accurate input for dual-channel command voltage generation. In this way, reliable operation of the wind power converter is ensured under complex grid conditions, improving wind power grid connection performance and grid adaptability.

[0038] Furthermore, a power decoupling control system for wind power converters based on virtual impedance is also provided.

[0039] Figure 3 This is a block diagram of a wind power converter power decoupling control system based on virtual impedance according to an embodiment of this application. Figure 3 As shown, the wind power converter power decoupling control system 300 based on virtual impedance according to an embodiment of this application includes: a sequence component decomposition module 310, used to perform sequence component decomposition on the three-phase voltage of the power grid and the three-phase current of the converter to obtain positive sequence voltage. Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive-sequence fundamental angular frequency, and grid positive-sequence fundamental phase angle; dual synchronous coordinate system transformation module 320, used to transform the positive-sequence coordinate system based on the grid positive-sequence fundamental phase angle. Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. An independent adaptive virtual impedance voltage drop calculation module 330 calculates the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current based on the positive-sequence fundamental angular frequency of the grid to obtain the positive-sequence dq virtual voltage drop and negative-sequence dq virtual voltage drop. A dual-channel command voltage generation module 340 generates dual-channel command voltages based on the positive-sequence dq virtual voltage drop and negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and negative-sequence dq converter command voltage. A PWM signal generation module 350 synthesizes the positive-sequence dq converter command voltage and generates a PWM signal based on the positive-sequence fundamental phase angle of the grid to obtain a three-phase PWM drive signal.

[0040] As described above, the wind power decoupling control system 300 based on virtual impedance according to the embodiments of this application can be implemented in various wireless terminals, such as servers with a wind power decoupling control algorithm based on virtual impedance. In one possible implementation, the wind power decoupling control system 300 based on virtual impedance according to the embodiments of this application can be integrated into the wireless terminal as a software module and / or a hardware module. For example, the wind power decoupling control system 300 based on virtual impedance can be a software module in the operating system of the wireless terminal, or it can be an application developed for the wireless terminal; of course, the wind power decoupling control system 300 based on virtual impedance can also be one of many hardware modules of the wireless terminal.

[0041] Alternatively, in another example, the virtual impedance-based wind power converter power decoupling control system 300 and the wireless terminal can also be separate devices, and the virtual impedance-based wind power converter power decoupling control system 300 can be connected to the wireless terminal via wired and / or wireless networks, and transmit interactive information in accordance with an agreed data format.

[0042] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A power decoupling control method for wind power converters based on virtual impedance, characterized in that, include: Sequence component decomposition is performed on the three-phase voltage of the power grid and the three-phase current of the converter to obtain the positive sequence. Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive sequence fundamental frequency and grid positive sequence fundamental phase angle; Based on the positive-sequence fundamental phase angle of the power grid, for the positive-sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current is transformed using a dual synchronous coordinate system to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. Based on the positive-sequence fundamental angular frequency of the power grid, independent adaptive virtual impedance voltage drop calculations are performed on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current to obtain the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop. Dual-channel command voltage generation is performed based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage; Based on the positive sequence fundamental phase angle of the power grid, the command voltage of the positive sequence dq converter and the command voltage of the negative sequence dq converter are synthesized and PWM signal is generated to obtain the three-phase PWM drive signal.

2. The wind power converter power decoupling control method based on virtual impedance according to claim 1, characterized in that, Based on the positive-sequence fundamental phase angle of the power grid, for the positive-sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. This includes: based on the positive-sequence fundamental phase angle of the grid, the positive-sequence dq converter current is transformed using the following formula. Grid voltage or positive sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain either the positive-sequence dq grid voltage or the positive-sequence dq converter current, wherein the formula is: in, The positive sequence fundamental phase angle of the power grid. Forward order Grid voltage or positive sequence Converter current, dq represents the positive-sequence grid voltage or the positive-sequence converter current.

3. The wind power converter power decoupling control method based on virtual impedance according to claim 2, characterized in that, Based on the positive-sequence fundamental phase angle of the power grid, for the positive-sequence... Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. This includes: based on the positive-sequence fundamental phase angle of the grid, the negative-sequence dq converter current is transformed using the following formula. Grid voltage or negative sequence The converter current undergoes a dual synchronous coordinate system transformation to obtain the negative-sequence dq grid voltage or the negative-sequence dq converter current, as shown in the formula: in, negative order Grid voltage or negative sequence Converter current, The negative sequence dq is the grid voltage or the negative sequence dq is the converter current.

4. The wind power converter power decoupling control method based on virtual impedance according to claim 1, characterized in that, Based on the positive-sequence fundamental angular frequency of the power grid, independent adaptive virtual impedance voltage drop calculations are performed on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current to obtain the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop, including: The grid imbalance is assessed and the virtual impedance parameters are dynamically decided based on the positive-sequence dq grid voltage and the negative-sequence dq grid voltage to obtain the currently effective positive-sequence virtual impedance parameters and the currently effective negative-sequence virtual impedance parameters. The positive sequence virtual voltage drop is calculated based on the currently effective positive sequence virtual impedance parameters, the grid positive sequence fundamental frequency, and the positive sequence dq converter current to obtain the positive sequence dq virtual voltage drop; The negative-sequence virtual voltage drop is calculated based on the currently effective negative-sequence virtual impedance parameters, the positive-sequence fundamental frequency of the power grid, and the negative-sequence dq converter current to obtain the negative-sequence dq virtual voltage drop.

5. The wind power converter power decoupling control method based on virtual impedance according to claim 4, characterized in that, The grid imbalance is assessed and virtual impedance parameters are dynamically determined for both positive-sequence dq grid voltage and negative-sequence dq grid voltage to obtain the currently effective positive-sequence virtual impedance parameters and the currently effective negative-sequence virtual impedance parameters, including: The voltage component amplitudes of the positive-sequence dq grid voltage and the negative-sequence dq grid voltage are calculated to obtain the vector amplitudes of the positive-sequence dq grid voltage and the negative-sequence dq grid voltage. Calculate the voltage imbalance factor based on the positive-sequence dq grid voltage vector magnitude and the negative-sequence dq grid voltage vector magnitude; Input the voltage imbalance factor into the parameter decision engine to obtain the currently effective positive-sequence virtual impedance parameter and the currently effective negative-sequence virtual impedance parameter.

6. The wind power converter power decoupling control method based on virtual impedance according to claim 5, characterized in that, Based on the positive-sequence dq grid voltage vector magnitude and the negative-sequence dq grid voltage vector magnitude, the voltage imbalance factor is calculated, including: calculating the voltage imbalance factor using the following formula, wherein the formula is: in, The magnitude of the negative-sequence dq grid voltage vector. dq represents the magnitude of the grid voltage vector in positive sequence.

7. The wind power converter power decoupling control method based on virtual impedance according to claim 4, characterized in that, The positive-sequence virtual voltage drop is calculated based on the currently effective positive-sequence virtual impedance parameters, the grid positive-sequence fundamental angular frequency, and the positive-sequence dq converter current to obtain the positive-sequence dq virtual voltage drop. This includes calculating the positive-sequence virtual voltage drop using the following formula: in, For positive-order dq virtual voltage drop, The positive sequence fundamental angular frequency of the power grid. This represents the positive-sequence dq converter current. and This is the currently active positive-sequence virtual impedance parameter.

8. The power decoupling control method for wind power converters based on virtual impedance according to claim 1, characterized in that, Dual-channel command voltage generation is performed based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage, including: Calculate the positive sequence current reference value based on the positive sequence active power reference value and the positive sequence reactive power reference value. The positive sequence current reference value and the positive sequence dq converter current are input into the positive sequence current loop PI controller to obtain the positive sequence voltage PI control term; The positive sequence dq converter command voltage is determined based on the positive sequence voltage PI control term, the positive sequence dq virtual voltage drop, and the positive sequence dq grid voltage.

9. The power decoupling control method for wind power converters based on virtual impedance according to claim 8, characterized in that, Dual-channel command voltage generation is performed based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage, including: The negative sequence dq current reference value and the negative sequence dq converter current are input to the output of the negative sequence current loop PI controller to obtain the negative sequence current PI control term. The negative-sequence dq converter command voltage is determined based on the negative-sequence current PI control term, the negative-sequence dq virtual voltage drop, and the negative-sequence dq grid voltage.

10. A power decoupling control system for wind power converters based on virtual impedance, characterized in that, include: The sequence component decomposition module is used to perform sequence component decomposition on the three-phase voltage of the power grid and the three-phase current of the converter to obtain the positive sequence. Grid voltage, negative sequence Grid voltage, positive sequence Converter current, negative sequence Converter current, grid positive sequence fundamental frequency and grid positive sequence fundamental phase angle; The dual-synchronous coordinate system transformation module is used to transform the positive-sequence fundamental phase angle of the power grid. Grid voltage, negative sequence Grid voltage, positive sequence Converter current and negative sequence The converter current is transformed using a dual synchronous coordinate system to obtain the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current. The independent adaptive virtual impedance voltage drop calculation module is used to perform independent adaptive virtual impedance voltage drop calculations on the positive-sequence dq grid voltage, negative-sequence dq grid voltage, positive-sequence dq converter current, and negative-sequence dq converter current based on the positive-sequence fundamental frequency of the grid to obtain the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop. A dual-channel command voltage generation module is used to generate dual-channel command voltages based on the positive-sequence dq virtual voltage drop and the negative-sequence dq virtual voltage drop to obtain the positive-sequence dq converter command voltage and the negative-sequence dq converter command voltage. The PWM signal generation module is used to synthesize the command voltage of the positive-sequence dq converter and the command voltage of the negative-sequence dq converter based on the positive-sequence fundamental phase angle of the power grid, and generate a PWM signal to obtain a three-phase PWM drive signal.

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