Impedance reshaping control method and system for permanent magnet type wind turbine grid-side converter facing weak grid

Abstract

The application discloses an impedance remodeling control method and system for a permanent magnet type fan grid side converter of a weak grid, and belongs to the technical field of fan grid side converter control. The method comprises the following steps: after a synchronous error signal is constructed based on a q-axis voltage component of a point of common coupling, the synchronous error signal is input into a synchronous disturbance leakage reconstruction unit constructed by using a phase-locked angle frequency to obtain a bounded synchronous angle disturbance quantity; d-axis and q-axis current components of an output current of the grid side converter are subjected to low-pass filtering to obtain a quasi-steady-state current vector; a compensation gain is generated by using a power critical region; the bounded synchronous angle disturbance quantity, the quasi-steady-state current vector and the compensation gain are used to generate a compensation current reference, which is superimposed to original d-axis and q-axis current references to generate a fan grid side converter driving control signal through a current inner loop modulation link. While the traditional grid-following type control main structure is retained, the bounded and self-adaptive method can weaken the adverse coupling influence of a phase-locked loop.

Description

Technical Field

[0001] This invention belongs to the field of wind turbine grid-side converter control technology, specifically relating to an impedance reshaping control method and system for permanent magnet wind turbine grid-side converters in weak power grids. Background Technology

[0002] With the large-scale integration of permanent magnet wind power generation systems, the proportion of permanent magnet wind turbine grid-side converters in power systems continues to increase. Due to their mature structure, simple implementation, and fast power point tracking, permanent magnet wind turbine grid-side converters remain one of the most widely used interface types in new energy grid-connected systems. Typical permanent magnet wind turbine grid-side converters usually employ a synchronous rotating coordinate system phase-locked loop to obtain the grid phase angle, and at this phase angle, achieve active power, reactive power, or voltage amplitude control, as well as dq-axis current inner-loop control.

[0003] Under strong grid conditions, the point of common coupling (PCC) voltage is approximately rigid, and the coupling between the phase-locked loop (PLL) and the current loop is weak, allowing traditional vector current control to maintain good dynamic performance. However, under weak grid conditions, the grid's equivalent impedance increases, and the output current of the wind turbine grid-side converter significantly affects the PCC voltage. This PCC voltage then feeds back to the PLL and the control system, forming a dynamic coupling between the PLL, the current controller, and the grid impedance. This coupling may exhibit negative damping or negative resistance characteristics, causing the dynamic stability boundary of the wind turbine grid-side converter to fall below the static power transfer limit determined by the current limit.

[0004] Existing improvement methods include reducing the PLL bandwidth, redesigning the current controller, introducing virtual impedance, using dual PLL impedance reshaping, or converting to grid-based control. Reducing the PLL bandwidth may sacrifice synchronization speed and low voltage ride-through performance; grid-based or virtual synchronization control will change the original grid-following control architecture and current limiting logic; fixed-parameter impedance reshaping methods may result in unnecessary compensation or compensation drift under low power or grid frequency offset conditions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an impedance reshaping control method and system for grid-side converters of permanent magnet wind turbines in weak power grids. While retaining the main structure of traditional grid-connected control, it can limitlessly and adaptively reduce the adverse coupling effects of phase-locked loops.

[0006] This invention provides the following technical solution:

[0007] Firstly, an impedance reshaping control method for a permanent magnet wind turbine grid-side converter in a weak power grid is provided. The permanent magnet wind turbine grid-side converter uses a synchronous rotating coordinate system phase-locked loop for orientation and is connected to the weak power grid through vector current control cascaded with an outer power loop and an inner current loop. The control method includes: Obtain the phase-locked frequency, d-axis and q-axis voltage components at the common coupling point, and d-axis and q-axis current components of the grid-side converter output current of the permanent magnet wind turbine. A synchronization disturbance leakage reconstruction unit is constructed using the phase-locked loop angular frequency, and the synchronization error signal constructed based on the q-axis voltage component is input to obtain the bounded synchronization angle disturbance. Low-pass filtering is applied to the d-axis current component and the q-axis current component to obtain the quasi-steady-state current vector; The compensation gain is adaptively generated based on the pre-acquired static power limit per unit value, the compensation start-up power, and the current active power per unit value. By utilizing the bounded synchronization angle disturbance, the quasi-steady-state current vector, and the compensation gain, a compensation current reference that is opposite to the negative damping admittance of the phase-locked loop is generated. The compensation current reference is superimposed on the original d-axis current reference and q-axis current reference generated through the power outer loop, and then the wind turbine grid-side converter drive control signal is generated through current inner loop adjustment, coordinate transformation and PWM modulation.

[0008] Optionally, the step of constructing a synchronization disturbance leakage reconstruction unit using the phase-locked loop angular frequency and inputting the synchronization error signal constructed based on the q-axis voltage component to obtain the bounded synchronization angle disturbance is as follows: The transfer function of the synchronous disturbance leakage reconfiguration unit is constructed using the phase-locked loop frequency. : ;in, This is the proportional gain of the phase-locked loop. The integral coefficients of the phase-locked loop are... For complex frequency domain operators, The phase-locked loop frequency; Construct a synchronization error signal and calculate the bounded synchronization angle disturbance using the following formula. : ; in, The synchronization error signal is obtained by normalizing the q-axis voltage disturbance at the common coupling point to the rated voltage. The value of the q-axis voltage disturbance at the common coupling point. This is the rated voltage at the common coupling point.

[0009] Optionally, the formula for calculating the quasi-steady-state current vector is: ; in, The quasi-steady-state current vector includes the d-axis quasi-steady-state current component. and q-axis quasi-steady-state current component , Let be the transfer function of the low-pass filter. and These are the d-axis and q-axis current components of the grid-side converter output current, respectively. For complex frequency domain operators, The filter bandwidth is measured to compensate for the current.

[0010] Optionally, the adaptive generation of compensation gain based on the pre-acquired static power limit per-unit value, the compensation start-up power, and the current active power per-unit value specifically involves: ; in, To compensate for the gain, To preset the maximum compensation gain, It is a saturation function in the range of 0 to 1. This is the current active power per unit value. This is the preset compensated starting power; It is the static power limit per unit value, obtained through the short-circuit ratio (SCR) and the resistance-inductance ratio or impedance angle parameter of the grid impedance; when Less than or equal to At that time, compensation gain =0 or close to 0; when Greater than and gradually approaching At that time, compensation gain Follow Increase and grow; when Reaching or exceeding Time-compensated gain Restricted to Within.

[0011] Optionally, the calculation formula for the compensation current reference is: ; in, and These are the d-axis and q-axis compensation current references, respectively. To compensate for the gain, The transfer function of the compensation command filter, Let be the bounded synchronization angle disturbance. and These are the d-axis quasi-steady-state current components and the q-axis quasi-steady-state current components, respectively. For complex frequency domain operators, To compensate for the cutoff angular frequency of the command filter.

[0012] Optionally, the formula for superimposing the compensation current reference onto the original d-axis current reference and q-axis current reference generated through the power outer loop is: ; in, and These are the reshaped d-axis and q-axis current references, respectively. and These are the original d-axis current reference and q-axis current reference generated through the power outer loop, respectively. and These are the d-axis and q-axis compensation current references, respectively. To preset the maximum compensation current, This represents the vector magnitude of the compensation current reference.

[0013] Secondly, an impedance reshaping control system for a permanent magnet wind turbine grid-side converter in a weak grid is provided. The permanent magnet wind turbine grid-side converter uses a synchronous rotating coordinate system phase-locked loop for orientation and is connected to the weak grid via vector current control cascaded with a power outer loop and a current inner loop. The system includes: The acquisition module is used to acquire the phase-locked angle frequency, d-axis and q-axis voltage components of the common coupling point of the grid-side converter of the permanent magnet wind turbine, and the d-axis and q-axis current components of the output current of the grid-side converter. The synchronization disturbance leakage reconstruction unit is used to construct the synchronization disturbance leakage reconstruction unit using the phase-locked angle frequency, and inputs the synchronization error signal constructed based on the q-axis voltage component to obtain the bounded synchronization angle disturbance amount; The quasi-steady-state current vector acquisition module is used to perform low-pass filtering on the d-axis current component and the q-axis current component to obtain the quasi-steady-state current vector. The adaptive gain module is used to adaptively generate compensation gain based on the pre-acquired static power limit per unit value, compensation start-up power, and current active power per unit value. The orthogonal anti-coupling admittance mapping module is used to generate a compensation current reference that is opposite to the negative damping admittance of the phase-locked loop by utilizing the bounded synchronization angle disturbance, the quasi-steady-state current vector, and the compensation gain. The current reference reshaping module is used to superimpose the compensated current reference onto the original d-axis current reference and q-axis current reference generated through the power outer loop to obtain the reshaped current reference. The inner loop modulation module is used to send the reshaped current reference into the inner current loop for adjustment, and generate the wind turbine grid-side converter drive control signal through coordinate transformation and PWM modulation.

[0014] Thirdly, a computer device is provided, including a processor and a memory; wherein, when the processor executes a computer program stored in the memory, it implements the steps of the impedance reshaping control method for a grid-side converter of a permanent magnet wind turbine for weak power grids as described in any one of the first aspects.

[0015] Fourthly, a computer-readable storage medium is provided for storing a computer program; when the computer program is executed by a processor, it implements the steps of the impedance reshaping control method for a grid-side converter of a permanent magnet wind turbine for a weak power grid as described in any one of the first aspects.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) The impedance reshaping control method proposed in this invention, without replacing the traditional synchronous rotating coordinate system phase-locked loop and without changing the original power outer loop and current inner loop main structure, achieves directional weakening of the unfavorable coupling admittance of the phase-locked loop under weak grid conditions by adding adaptive leakage impedance reshaping compensation, thereby improving the small signal stability margin of the permanent magnet wind turbine grid-side converter under high power weak grid operation conditions. It can be applied to direct-drive permanent magnet wind turbine grid-side converters, semi-direct-drive permanent magnet wind turbine grid-side converters, offshore permanent magnet wind turbine grid-side converters, and other permanent magnet wind turbine grid-connected devices that adopt grid-following vector current control.

[0017] (2) The present invention proposes a synchronization disturbance leakage reconstruction mechanism, which maps the q-axis voltage disturbance at the common coupling point to a bounded synchronization angle disturbance. While retaining the phase-locked loop disturbance compensation information, the leakage link limits the DC gain, thus avoiding compensation drift or long-term accumulation when the traditional pure integral compensation deviates from the grid frequency.

[0018] (3) The present invention proposes a quasi-steady-state current vector mechanism, which extracts the slow-changing operating point component of the output current through low-pass filtering, so that the compensation branch mainly uses the steady-state current vector direction for impedance reshaping, reducing the additional nonlinear coupling caused by the multiplication of instantaneous current disturbance and phase-locked loop disturbance, while suppressing sampling noise and switching ripple from entering the compensation channel.

[0019] (4) The present invention proposes an adaptive gain scheduling mechanism, which dynamically adjusts the compensation intensity according to the relationship between the active power operating point and the static power limit, so as to achieve low intervention under light load conditions and strong compensation under high power weak network critical conditions, and avoid unnecessary coupling or overcompensation risk in the low power range by fixed compensation parameters.

[0020] (5) The orthogonal anti-coupling admittance mapping and compensation current safety envelope mechanism proposed in this invention generates a compensation current reference that is opposite to the negative damping effect of the phase-locked loop by orthogonally mapping the quasi-steady-state current vector with the bounded synchronization angle disturbance. At the same time, the compensation current is compensated by using compensation command filtering, vector limiting and input logic constraint, so that the stability improvement process is compatible with the original current protection logic. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the impedance reshaping control method for grid-side converters of permanent magnet wind turbines in weak power grids according to the present invention. Figure 2This is a flowchart of the impedance reshaping control method for grid-side converters of permanent magnet wind turbines in weak power grids according to the present invention. Figure 3 This is a generalized Nyquist stability analysis diagram of different active power operating points after adopting the method of this invention; Figure 4 The experimental waveforms are obtained using the traditional VCC method under the equivalent operating condition of a 600 W wind turbine with a step increase in active power in a weak power grid. Figure 5 The experimental waveforms of the method of the present invention are shown under the equivalent operating condition of a 600 W wind turbine with a step increase in active power in the same weak power grid. Figure 6 The traditional VCC method is used to evaluate the dq-axis current and current amplitude response under the equivalent operating condition of a 600 W wind turbine with a step increase in active power in the same weak power grid. Figure 7 The present invention relates to the dq-axis current and current amplitude response under the equivalent operating condition of a 600 W wind turbine active power step jump in the same weak power grid. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention. It should be noted that the term "comprising" and any variations thereof in the specification, claims and the above-mentioned drawings of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0023] Example 1: like Figure 1 and Figure 2 As shown, an impedance reshaping control method for a permanent magnet wind turbine grid-side converter for weak power grids is proposed. The permanent magnet wind turbine grid-side converter is connected to the weak power grid using a synchronous rotating coordinate system phase-locked loop and vector current control. The weak power grid is a grid with a low short-circuit ratio and a large equivalent impedance. The permanent magnet wind turbine grid-side converter includes a permanent magnet synchronous generator, a generator-side converter, a DC bus, a two-level or multi-level grid-side inverter bridge, an output filter, a common coupling point capacitor, and the equivalent impedance of the power grid.

[0024] The impedance reshaping control method includes the following steps: Step S1: Obtain the phase-locked angle frequency, d-axis and q-axis voltage components of the common coupling point, and d-axis and q-axis current components of the grid-side converter output current of the permanent magnet wind turbine.

[0025] The voltage at the common coupling point of the grid-side converter of the three-phase permanent magnet wind turbine and the output current of the grid-side converter are collected. The phase-locked loop angular frequency, the d-axis and q-axis voltage components of the common coupling point, and the d-axis and q-axis current components of the grid-side converter output current are obtained through phase-locked loop synchronization orientation and coordinate transformation.

[0026] The voltage at the common coupling point is transformed into d-axis and q-axis voltage components in the dq rotating coordinate system using Clark and Park transformations. Similarly, the grid-side converter output current (inverter output current) is transformed into d-axis and q-axis current components in the dq rotating coordinate system using Clark and Park transformations. The transformed q-axis voltage component is then fed into the PI controller within the phase-locked loop for closed-loop calculation to obtain the phase-locked frequency.

[0027] In this embodiment, active power also needs to be collected for use in step S4, and grid-connected current also needs to be collected for use in step S6 to generate the original d-axis current reference and q-axis current reference through the power outer loop.

[0028] Step S2: Construct a synchronization disturbance leakage reconstruction unit using the phase-locked loop angular frequency, and input the synchronization error signal constructed based on the q-axis voltage component to obtain the bounded synchronization angle disturbance.

[0029] Step S2 specifically includes: Step S21: Construct the transfer function of the synchronization disturbance leakage reconstruction unit using the phase-locked loop frequency. : ;in, This is the proportional gain of the phase-locked loop. The integral coefficients of the phase-locked loop are... For complex frequency domain operators, The phase-locked loop frequency; Step S22: Construct a synchronization error signal and calculate the bounded synchronization angle disturbance using the following formula. : ; in, The synchronization error signal is obtained by normalizing the q-axis voltage disturbance at the common coupling point to the rated voltage. This signal is used to characterize the synchronization coupling strength between the main phase-locked loop and the weak grid voltage disturbance. The value of the q-axis voltage disturbance at the common coupling point. This is the rated voltage at the common coupling point.

[0030] By utilizing the transfer function of the synchronous disturbance leakage reconfiguration unit and the synchronous error signal for angle compensation, the infinite accumulation of compensation can be avoided when the grid frequency deviates.

[0031] Step S3: Perform low-pass filtering on the d-axis current component and the q-axis current component to obtain the quasi-steady-state current vector.

[0032] A first-order low-pass filter is used to extract the slowly changing component of the output current. This is to avoid the multiplication of current disturbances and PLL (Phase-Locked Loop) disturbances, which would introduce additional coupling. The formula for calculating the quasi-steady-state current vector is: ; in, The quasi-steady-state current vector includes the d-axis quasi-steady-state current component. and q-axis quasi-steady-state current component , Let be the transfer function of the low-pass filter. and These are the d-axis and q-axis current components of the grid-side converter output current, respectively. For complex frequency domain operators, To compensate for the current measurement filter bandwidth, it is used to reduce the second-order coupling term generated by the multiplication of current disturbance and phase-locked loop disturbance, and to suppress sampling noise, switching ripple and current oscillation components from entering the compensation.

[0033] Step S4: Adaptively generate compensation gain based on the pre-acquired static power limit per unit value, compensation start-up power, and current active power per unit value.

[0034] The specific formula is as follows: ; in, To compensate for the gain, To preset the maximum compensation gain, It is a saturation function in the range of 0 to 1. This is the current active power per unit value. The preset compensated starting power, This is the per-unit value of the static power limit.

[0035] when Less than or equal to At that time, compensation gain =0 or close to 0; when Greater than and gradually approaching At that time, compensation gain Follow Increase and grow; when Reaching or exceeding Time-compensated gain Restricted to Within.

[0036] The static power limit per unit value is obtained based on the short-circuit ratio (SCR) and the resistance-inductance ratio or impedance angle parameter of the grid impedance. This value is then used to define the critical power domain of the weak grid, so that the compensation branch is enhanced in the high-power operating range of the weak grid and weakened or withdrawn in the light-load range.

[0037] Step S5: Using the bounded synchronization angle disturbance, quasi-steady-state current vector, and compensation gain, generate a compensation current reference that is opposite to the negative damping admittance of the phase-locked loop.

[0038] The formula for calculating the compensation current reference is: ; in, and These are the d-axis and q-axis compensation current references, respectively. To compensate for the gain, The transfer function of the compensation command filter is used to prevent abrupt changes in the compensation current reference during power jumps, phase-locked loop disturbances, or compensation gain changes. Let be the bounded synchronization angle disturbance. and These are the d-axis quasi-steady-state current components and the q-axis quasi-steady-state current components, respectively. For complex frequency domain operators, To compensate for the cutoff angular frequency of the command filter.

[0039] By multiplying the quasi-steady-state current vector with the bounded synchronization angle disturbance, an initial compensation current reference is formed that is opposite in direction to the negative damping admittance component caused by the phase-locked loop. Then, after multiplying with the compensation gain, compensation command filtering is performed to achieve phase-locked coupling reverse admittance injection.

[0040] Step S6: The compensation current reference is superimposed on the original d-axis current reference and q-axis current reference generated through the power outer loop, and the wind turbine grid-side converter drive control signal is generated through current inner loop adjustment, coordinate transformation and PWM modulation.

[0041] In this embodiment, the compensation current reference generated in step S5 is first vector-limited, and then superimposed on the original d-axis current reference and the original q-axis current reference generated through the power outer loop to reshape the original d-axis current reference and the original q-axis current reference, resulting in the reshaped current reference. The specific formula is as follows: ; in, and These are the reshaped d-axis and q-axis current references, respectively. and These are the original d-axis current reference and q-axis current reference generated through the power outer loop, respectively. and These are the d-axis and q-axis compensation current references, respectively. To preset the maximum compensation current, This represents the vector magnitude of the compensation current reference.

[0042] The reshaped d-axis and q-axis currents are referenced to the inner loop of the input current, and the wind turbine grid-side converter drive signal is generated through coordinate transformation and PWM modulation to weaken the unfavorable coupling between the phase-locked loop and the weak grid impedance.

[0043] like Figure 1 As shown, the traditional control method for a permanent magnet wind turbine grid-side converter, which includes a synchronous rotating coordinate system phase-locked loop, a power outer loop (including a power control loop and a voltage control loop), and a current inner loop, is as follows: The power control loop sets the active power setpoint. With feedback power In comparison, the original d-axis current reference generated by PI regulation is... The voltage control loop sets the PCC voltage amplitude setpoint. With feedback value In comparison, the original q-axis current reference is generated after PI regulation. .

[0044] Original d-axis current reference and the original q-axis current reference With actual d-axis current and actual q-axis current After comparison, the PI controller through the inner current loop and The cross-coupling decoupling stage generates a voltage command, which is then transformed into a switching drive signal via coordinate transformation and SPWM. For the converter-side filter inductor, The rated grid angular frequency. The phase-locked loop (PLL) uses the q-axis PCC (point of common coupling) voltage. To compensate for synchronization errors, a frequency correction amount is generated. And obtain the synchronization angle ; and These represent the PCC voltage vector and the grid-side converter output current vector in the dq coordinate system, respectively. The grid-side converter output current vector includes the d-axis and q-axis current components of the grid-side converter output current. and .

[0045] This invention adds an adaptive leakage compensation branch without replacing the traditional synchronous rotating coordinate system phase-locked loop, or changing the main structure of the original power outer loop (including the power control loop and voltage control loop) and current inner loop. through Quasi-steady-state current vector generated after filtering with by Reconstructed bounded synchronization angle perturbation Combined, and through Filtering and compensating gain Create a compensation current reference, and compare the compensation current reference with the original d-axis current reference. and the original q-axis current reference Superposition completes impedance reshaping and gain compensation. It increases with the increase of operating active power, avoids overcompensation at low power and enhances impedance reshaping effect under high power and weak grid conditions, thereby improving small signal stability.

[0046] The following specific embodiments are used to verify the beneficial effects of the present invention: Figure 3 In Figure (a), the generalized Nyquist trajectories are shown for active power of 0.60 pu, 0.70 pu, 0.90 pu, and 0.95 pu. Figure 3 In Figure (b), the curves representing the changes in the generalized Nyquist minimum distance and the maximum real part of the state-space eigenvalues ​​are shown. Figure 3 As shown in (a), as the active power gradually increases, the generalized Nyquist trajectory gradually moves towards the critical point. The trajectory approaches, but at the high-power operating point of 0.95 pu, still does not encircle or cross the critical point, indicating that the impedance reshaping control method of this application can still maintain small-signal stability under weak grid conditions close to the static power limit. According to Figure 3 As shown in (b), when the active power increases from 0.60 pu to 0.95 pu, the critical point is reached. The minimum distance decreased from about 0.1425 to about 0.0565, indicating that the stability margin gradually decreased with increasing power, but always maintained a positive margin; at the same time, the maximum real part of the state space eigenvalue was always less than 0, indicating that the dominant eigenvalues ​​of the control system were all located in the left half of the complex plane, and no small-signal instability occurred.

[0047] Figure 4 , Figure 5 , Figure 6 and Figure 7 The experimental conditions were as follows: the permanent magnet wind turbine grid-side converter was connected to a weak power grid and the active power reference value gradually increased from 0 W to 600 W at 0.2 s, 0.7 s and 1.2 s respectively.

[0048] Figure 4 (a) shows the active power response curve of a 600 W wind turbine under a step test of active power in a weak power grid using the traditional VCC method. Figure 4(b) shows the PCC voltage amplitude curve under the active power step test of a 600 W wind turbine in a weak power grid using the traditional VCC method. Figure 4 (c) in the figure shows the PLL frequency curve under the active power step test of a 600 W wind turbine in a weak power grid using the traditional VCC method. Figure 4 In the figure (d), the curve is the locally amplified response curve after the last step in the active power step test of a 600 W wind turbine in a weak power grid using the traditional VCC method; according to Figure 4 As shown in (a), after the first two power step jumps (0.2 s and 0.7 s), the traditional VCC control method can still maintain a certain tracking capability; however, when the active power reference value rises to 600 W, according to Figure 4 (b) Figure 4 (c) and Figure 4 As shown in (d), the stability margin is significantly insufficient, with both active power and the point of common coupling voltage exhibiting continuous oscillations. Furthermore, the oscillation amplitude increases over time, and the waveform exceeds the normal display range after approximately 1.84 s. Simultaneously, the phase-locked loop (PLL) frequency also shows a significant shift. This result indicates that the traditional permanent magnet wind turbine grid-side converter control method (traditional VCC control method) is easily affected by the coupling between the PLL and grid impedance under high-power operation conditions in a weak power grid, leading to reduced dynamic stability.

[0049] Figure 5 (a) shows the active power response curve of the method of the present invention under the active power step test of a 600 W wind turbine in a weak power grid. Figure 5 (b) in the figure shows the PCC voltage amplitude curve under the active power step test of a 600 W wind turbine in a weak power grid using the method of the present invention. Figure 5 (c) in the figure represents the PLL frequency curve under the active power step test of a 600 W wind turbine in a weak power grid using the method of the present invention. Figure 5 (d) in the figure represents the locally amplified response curve after the last step in the active power step test of a 600 W wind turbine in a weak power grid using the method of the present invention; according to Figure 5 (a) Figure 5 (b) Figure 5 (c) and Figure 5As shown in (d), after the last power step (1.2s), the method of this application can still maintain stable operation. The active power can stably track the 600 W reference value, the common coupling point voltage remains near the rated value, and the phase-locked loop frequency remains within the range of 49.5 Hz to 50.5 Hz. In the steady-state range after the test, the average active power is approximately 601.3 W, the average common coupling point voltage is approximately 49.88 V, and the average phase-locked loop frequency is approximately 50.0015 Hz. This result shows that the method of this application can effectively suppress divergent oscillations caused by power steps under weak grid conditions and improve the dynamic stability margin of the permanent magnet wind turbine grid-side converter near the high-power operating point.

[0050] Figure 6 (a) shows the dq-axis current curves of a 600 W wind turbine operating under the same weak power grid step equivalent condition using the traditional VCC method. Figure 6 (b) in the figure shows the current vector amplitude curve under the equivalent operating condition of a 600 W wind turbine with a step increase in active power in the same weak power grid, using the traditional VCC method. Figure 6 (c) in the figure is a locally magnified curve of the dq-axis current after the last step change under the equivalent operating condition of a 600 W wind turbine active power step change in the same weak power grid, using the traditional VCC method. Figure 6 (d) in the figure is a locally magnified curve of the current vector amplitude after the last step in the equivalent operating condition of a 600 W wind turbine active power step jump under the same weak power grid, using the traditional VCC method; Figure 6 (a) Figure 6 (b) Figure 6 (c) and Figure 6 As shown in (d), after the last active power step, the d-axis and q-axis currents of the traditional VCC method gradually exhibit significant oscillations, with the current vector amplitude continuously increasing and exceeding the normal display range after approximately 1.91 s. Especially in the latter part of the test, the q-axis current and current amplitude rise rapidly, indicating that the instability caused by the weak power grid is not only reflected in the active power and the voltage at the point of common coupling, but also further transmitted to the inner current loop, causing deterioration of current control performance and even leading to overcurrent risks.

[0051] Figure 7 In Figure (a), the dq-axis current curves of the present invention are shown under the equivalent operating condition of a 600 W wind turbine with a step increase in active power in the same weak power grid. Figure 7 (b) in the figure shows the current vector amplitude curve under the equivalent operating condition of a 600 W wind turbine active power step jump in the same weak power grid, as described in this invention. Figure 7 (c) in the figure is a locally magnified curve of the dq-axis current after the last step change under the equivalent operating condition of a 600 W wind turbine active power step change in the same weak power grid. Figure 7(d) in the figure is a locally magnified curve of the current vector amplitude after the last step change under the equivalent operating condition of a 600 W wind turbine active power step change in the same weak power grid; Figure 7 (a) Figure 7 (b) Figure 7 (c) and Figure 7 As shown in (d) above, even after multiple steps in active power, especially the final step to 600 W, the d-axis and q-axis currents of the proposed method remain bounded, with the current vector amplitude consistently below the rated peak current of 10.7 A. In the steady-state range after the test, the average current vector amplitude is approximately 8.79 A, ​​with a peak-to-peak fluctuation of approximately 0.89 A, and no continuous amplification oscillation phenomenon observed in traditional VCC control methods is observed. These results demonstrate that the proposed method can effectively suppress current oscillations, prevent current loop instability, and improve system operational safety under high-power conditions in weak power grids.

[0052] In summary, compared to traditional control methods for permanent magnet wind turbine grid-side converters, the impedance reshaping control method of this application, without altering the original main phase-locked loop and vector current control structure, effectively weakens the unfavorable coupling between the phase-locked loop and the weak grid impedance through adaptive leakage impedance reshaping compensation. This allows the wind turbine grid-side converter to maintain stable operation of active power, common-point voltage, phase-locked loop frequency, and dq-axis current even under active power step and high-power operation conditions. Therefore, the impedance reshaping control method of this application has beneficial effects such as high dynamic stability, strong adaptability to weak grids, significant current oscillation suppression effect, and minimal engineering implementation modifications.

[0053] Example 2: An impedance reshaping control system for a permanent magnet wind turbine grid-side converter in a weak power grid is disclosed. The permanent magnet wind turbine grid-side converter employs a synchronous rotating coordinate system phase-locked loop for orientation and is connected to the weak power grid via vector current control cascaded through a power outer loop and a current inner loop. The control system includes: The acquisition module is used to acquire the phase-locked angle frequency, d-axis and q-axis voltage components of the common coupling point of the grid-side converter of the permanent magnet wind turbine, and the d-axis and q-axis current components of the output current of the grid-side converter. The synchronization disturbance leakage reconstruction unit is used to construct the synchronization disturbance leakage reconstruction unit using the phase-locked angle frequency, and inputs the synchronization error signal constructed based on the q-axis voltage component to obtain the bounded synchronization angle disturbance amount; The quasi-steady-state current vector acquisition module is used to perform low-pass filtering on the d-axis current component and the q-axis current component to obtain the quasi-steady-state current vector. The adaptive gain module is used to adaptively generate compensation gain based on the pre-acquired static power limit per unit value, compensation start-up power, and current active power per unit value. The orthogonal anti-coupling admittance mapping module is used to generate a compensation current reference that is opposite to the negative damping admittance of the phase-locked loop by utilizing the bounded synchronization angle disturbance, the quasi-steady-state current vector, and the compensation gain. The current reference reshaping module is used to superimpose the compensated current reference onto the original d-axis current reference and q-axis current reference generated through the power outer loop to obtain the reshaped current reference. The inner loop modulation module is used to send the reshaped current reference into the inner current loop for adjustment, and generate the wind turbine grid-side converter drive control signal through coordinate transformation and PWM modulation.

[0054] For more detailed information on the above modules, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.

[0055] Example 3: The present invention provides a computer device, including a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the above-described impedance reshaping control method for the grid-side converter of a permanent magnet wind turbine for weak power grids.

[0056] For more detailed information on the above methods, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.

[0057] Example 4: The present invention provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, it implements the steps of the above-described impedance reshaping control method for grid-side converters of permanent magnet wind turbines in weak power grids.

[0058] For more detailed information on the above methods, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.

[0059] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The systems, devices, and storage media disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments; relevant details can be found in the method section.

[0060] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0061] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An impedance reshaping control method for a permanent magnet wind turbine grid-side converter in a weak power grid, wherein the permanent magnet wind turbine grid-side converter adopts synchronous rotating coordinate system phase-locked loop orientation and is connected to the weak power grid through vector current control cascaded with power outer loop and current inner loop, characterized in that... include: Obtain the phase-locked frequency, d-axis and q-axis voltage components at the common coupling point, and d-axis and q-axis current components of the grid-side converter output current of the permanent magnet wind turbine. A synchronization disturbance leakage reconstruction unit is constructed using the phase-locked loop angular frequency, and the synchronization error signal constructed based on the q-axis voltage component is input to obtain the bounded synchronization angle disturbance. Low-pass filtering is applied to the d-axis current component and the q-axis current component to obtain the quasi-steady-state current vector; The compensation gain is adaptively generated based on the pre-acquired static power limit per unit value, the compensation start-up power, and the current active power per unit value. By utilizing the bounded synchronization angle disturbance, the quasi-steady-state current vector, and the compensation gain, a compensation current reference that is opposite to the negative damping admittance of the phase-locked loop is generated. The compensation current reference is superimposed on the original d-axis current reference and q-axis current reference generated through the power outer loop, and then the wind turbine grid-side converter drive control signal is generated through current inner loop adjustment, coordinate transformation and PWM modulation.

2. The impedance reshaping control method for permanent magnet wind turbine grid-side converters in weak power grids according to claim 1, characterized in that, The synchronization disturbance leakage reconstruction unit is constructed using the phase-locked loop angular frequency, and the synchronization error signal constructed based on the q-axis voltage component is input to obtain the bounded synchronization angle disturbance, specifically: The transfer function of the synchronous disturbance leakage reconfiguration unit is constructed using the phase-locked loop frequency. : ;in, This is the proportional gain of the phase-locked loop. The integral coefficients of the phase-locked loop are... For complex frequency domain operators, The phase-locked loop frequency; Construct a synchronization error signal and calculate the bounded synchronization angle disturbance using the following formula. : ； in, The synchronization error signal is obtained by normalizing the q-axis voltage disturbance at the common coupling point to the rated voltage. The value of the q-axis voltage disturbance at the common coupling point. This is the rated voltage at the common coupling point.

3. The impedance reshaping control method for permanent magnet wind turbine grid-side converters in weak power grids according to claim 1, characterized in that, The formula for calculating the quasi-steady-state current vector is: ； in, The quasi-steady-state current vector includes the d-axis quasi-steady-state current component. and q-axis quasi-steady-state current component , Let be the transfer function of the low-pass filter. and These are the d-axis and q-axis current components of the grid-side converter output current, respectively. For complex frequency domain operators, The filter bandwidth is measured to compensate for the current.

4. The impedance reshaping control method for permanent magnet wind turbine grid-side converters in weak power grids according to claim 1, characterized in that, The adaptive generation of compensation gain based on the pre-acquired static power limit per-unit value, compensation start-up power, and current active power per-unit value is specifically as follows: ； in, To compensate for the gain, To preset the maximum compensation gain, It is a saturation function in the range of 0 to 1. This is the current active power per unit value. This is the preset compensated starting power; It is the static power limit per unit value, obtained through the short-circuit ratio (SCR) and the resistance-inductance ratio or impedance angle parameter of the grid impedance; when Less than or equal to At that time, compensation gain =0 or close to 0; when Greater than and gradually approaching At that time, compensation gain Follow Increase and grow; when Reaching or exceeding Time-compensated gain Restricted to Within.

5. The impedance reshaping control method for permanent magnet wind turbine grid-side converters in weak power grids according to claim 1, characterized in that, The calculation formula for the compensation current reference is as follows: ； in, and These are the d-axis and q-axis compensation current references, respectively. To compensate for the gain, The transfer function of the compensation command filter, Let be the bounded synchronization angle disturbance. and These are the d-axis quasi-steady-state current components and the q-axis quasi-steady-state current components, respectively. For complex frequency domain operators, To compensate for the cutoff angular frequency of the command filter.

6. The impedance reshaping control method for permanent magnet wind turbine grid-side converters in weak power grids according to claim 1, characterized in that, The formula for superimposing the compensation current reference onto the original d-axis current reference and q-axis current reference generated through the power outer loop is as follows: ； in, and These are the reshaped d-axis and q-axis current references, respectively. and These are the original d-axis current reference and q-axis current reference generated through the power outer loop, respectively. and These are the d-axis and q-axis compensation current references, respectively. To preset the maximum compensation current, This represents the vector magnitude of the compensation current reference.

7. An impedance reshaping control system for a permanent magnet wind turbine grid-side converter in a weak power grid, wherein the permanent magnet wind turbine grid-side converter adopts synchronous rotating coordinate system phase-locked loop orientation and is connected to the weak power grid through vector current control cascaded with power outer loop and current inner loop, characterized in that... include: The acquisition module is used to acquire the phase-locked angle frequency, d-axis and q-axis voltage components of the common coupling point of the grid-side converter of the permanent magnet wind turbine, and the d-axis and q-axis current components of the output current of the grid-side converter. The synchronization disturbance leakage reconstruction unit is used to construct the synchronization disturbance leakage reconstruction unit using the phase-locked angle frequency, and inputs the synchronization error signal constructed based on the q-axis voltage component to obtain the bounded synchronization angle disturbance amount; The quasi-steady-state current vector acquisition module is used to perform low-pass filtering on the d-axis current component and the q-axis current component to obtain the quasi-steady-state current vector. The adaptive gain module is used to adaptively generate compensation gain based on the pre-acquired static power limit per unit value, compensation start-up power, and current active power per unit value. The orthogonal anti-coupling admittance mapping module is used to generate a compensation current reference that is opposite to the negative damping admittance of the phase-locked loop by utilizing the bounded synchronization angle disturbance, the quasi-steady-state current vector, and the compensation gain. The current reference reshaping module is used to superimpose the compensated current reference onto the original d-axis current reference and q-axis current reference generated through the power outer loop to obtain the reshaped current reference. The inner loop modulation module is used to send the reshaped current reference into the inner current loop for adjustment, and generate the wind turbine grid-side converter drive control signal through coordinate transformation and PWM modulation.

8. A computer device, characterized in that, It includes a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the impedance reshaping control method for the grid-side converter of a permanent magnet wind turbine for weak power grids as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, Used to store computer programs; when the computer programs are executed by a processor, they implement the steps of the impedance reshaping control method for grid-side converters of permanent magnet wind turbines for weak power grids as described in any one of claims 1-6.

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