Doubly-fed fan low voltage ride through control method, system and equipment and medium

Abstract

The invention relates to the technical field of power grid regulation and control, and discloses a doubly-fed fan low voltage ride through control method, system and device and a medium. Based on the influence of a proportional error of a voltage acquisition device adopted by a target doubly-fed fan and a direct current drift error of the voltage acquisition device on a grid-connected point voltage. Modeling the grid-connected point voltage of the target doubly-fed fan to obtain a theoretical measured value of the grid-connected point voltage; synchronously demodulating the grid-connected point voltage theoretical measurement value to obtain a proportional error estimation value and a direct current drift error estimation value; according to the proportional error estimation value and the direct current drift error estimation value, error compensation is carried out on the grid-connected point voltage measurement value of the target doubly-fed fan, and a compensated grid-connected point voltage measurement value is obtained; and controlling the low voltage ride through of the target doubly-fed fan according to the compensated grid-connected point voltage measurement value. According to the method, the accuracy of grid-connected point voltage measurement is improved, and the low-voltage ride-through capability of the doubly-fed fan is improved.

Description

Technical Field

[0001] This invention relates to the field of power grid regulation and control technology, and in particular to a method, system, equipment and medium for low voltage ride-through control of doubly fed wind turbines. Background Technology

[0002] As a crucial component of renewable energy, wind power generation has seen continuous expansion in installed capacity and grid connection scale. Doubly fed induction generators (hereinafter referred to as "doubly fed turbines") have become one of the mainstream turbine models in wind farms due to their advantages such as variable speed constant frequency and flexible adjustment. The voltage control characteristics and low-voltage ride-through capability of doubly fed turbines are key technical indicators for ensuring the safety and stability of the power grid. When the grid voltage fluctuates or a short-circuit fault occurs, doubly fed turbines need to maintain stable grid connection voltage through precise voltage control and remain connected to the grid for a specified period to avoid cascading accidents such as grid frequency collapse and voltage instability caused by large-scale turbine disconnection. This characteristic makes the adjustment of grid connection voltage extremely sensitive to reactive power. According to the AC circuit voltage balance principle, the line voltage drop is mainly determined by the reactance voltage drop corresponding to reactive power. Therefore, doubly fed turbines need to achieve stable grid connection voltage through precise reactive power adjustment, which requires high-precision acquisition and status judgment of the grid connection voltage signal.

[0003] Currently, in the low voltage ride-through control of doubly-fed induction generator (DFIG) wind turbines, the existing grid connection point voltage measurement generally relies on phase-locked loop (PLL) dq-axis transformation technology to determine whether the grid connection point voltage is lower than the low voltage ride-through threshold. However, due to grid connection point voltage measurement errors, the phase tracking accuracy of the PLL decreases, and the calculation of the dq-axis voltage components deviates. This leads to a decrease in the controller's "state awareness" of the grid connection point voltage, which ultimately significantly reduces the low voltage ride-through capability of the DFIG wind turbine. In severe cases, it can lead to the disconnection of the wind turbine from the grid, affecting the safe and stable operation of the power grid.

[0004] Therefore, improving the low-voltage ride-through capability of doubly-fed wind turbines has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a low-voltage ride-through control method, system, device, and medium for doubly-fed induction generator (DFIG) wind turbines, to solve the technical problem of how to improve the low-voltage ride-through capability of DFIG wind turbines, and to improve the accuracy of grid connection point voltage measurement and enhance the low-voltage ride-through capability of DFIG wind turbines.

[0006] In a first aspect, the present invention provides a low-voltage ride-through control method for a doubly-fed induction generator (DFIG), the method comprising: Modeling is performed on the grid connection point voltage measurement value of the target doubly-fed wind turbine to obtain the theoretical grid connection point voltage measurement value. The theoretical grid connection point voltage measurement value is set to reflect the influence of the DC drift error of the voltage acquisition equipment used by the target doubly-fed wind turbine and the proportional error of the voltage acquisition equipment on the grid connection point voltage. The theoretical measured value of the grid connection point voltage output after phase-locked loop processing is sequentially converted into a fundamental frequency voltage component and a second harmonic voltage component. The converted fundamental frequency DC component and second harmonic DC component are then sequentially subjected to band-pass filtering and low-pass filtering, respectively, to obtain the DC drift error estimate and the proportional error estimate. In the low voltage ride-through control of the target doubly-fed wind turbine, the grid connection point voltage measurement value of the target doubly-fed wind turbine is compensated for error based on the proportional error estimate and the DC drift error estimate, so as to obtain the compensated grid connection point voltage measurement value. Based on the compensated grid connection point voltage measurement, the low voltage ride-through of the target doubly fed wind turbine is controlled.

[0007] Preferably, the step of modeling the measured grid connection point voltage of the target doubly-fed wind turbine to obtain the theoretical measured grid connection point voltage includes: Error analysis was performed on the voltage acquisition equipment used in the target doubly fed wind turbine to obtain the error terms of the voltage acquisition equipment, which include proportional error and DC drift error. Based on the proportional error and the DC drift error, the grid connection point voltage measurement value of the target doubly fed wind turbine is modeled to obtain the theoretical measurement value of the grid connection point voltage.

[0008] Preferably, the theoretically measured grid-connected point voltage value output after phase-locked loop processing is sequentially converted to a fundamental frequency voltage component and then to a second harmonic voltage component. The resulting fundamental frequency DC component and second harmonic DC component are then sequentially subjected to bandpass filtering and low-pass filtering, respectively, to obtain DC drift error estimates and proportional error estimates, including: The theoretical measured value of the grid connection point voltage is sequentially subjected to phase-locked processing and minimization processing to obtain the theoretical measured value of the d-axis voltage of the theoretical measured value of the grid connection point voltage. The theoretical measured values ​​of the d-axis voltage are analyzed to determine the fundamental frequency voltage component introduced by the DC drift error and the second harmonic voltage component introduced by the proportional error in the theoretical measured values ​​of the d-axis voltage. Based on the fundamental frequency voltage component, a first voltage error processing factor for the fundamental frequency voltage component is determined, and based on the second harmonic voltage component, a second voltage error processing factor for the second harmonic voltage component is determined. The first voltage error processing factor is set to convert the fundamental frequency voltage component into a DC component, and the second voltage error processing factor is set to convert the second harmonic voltage component into a DC component. The fundamental frequency voltage component is preprocessed using the first voltage error processing factor to obtain the fundamental frequency voltage DC component of the theoretical measured value of the grid connection point voltage. The fundamental frequency voltage DC component is then subjected to a first bandpass filter and a first low-pass filter in sequence to obtain the DC drift error estimate. The second voltage error processing factor is used to preprocess the second harmonic voltage component to obtain the second harmonic voltage DC component of the theoretical measured value of the grid connection point voltage. The second harmonic voltage DC component is then subjected to a second bandpass filter and a second low-pass filter to obtain the proportional error estimate.

[0009] Preferably, the first voltage error processing factor includes and ; The second voltage error processing factor includes and .

[0010] Preferably, the step of sequentially performing a first bandpass filter and a first lowpass filter on the DC component of the fundamental frequency voltage to obtain a DC drift error estimate includes: The DC component of the fundamental frequency voltage is subjected to a first bandpass filter to obtain a first lowpass filter signal. The first low-pass filter processing is performed on the first signal to be low-pass filtered to obtain the phase-to-phase DC drift error difference; The DC drift error integral function is used to accumulate the interphase DC drift error difference to obtain an estimated value of the interphase DC drift error difference. The DC drift error integral function is used to make the interphase DC drift error difference approach zero when it converges. Based on the estimated value of the interphase DC drift error difference, the estimated value of the DC drift error is obtained.

[0011] Preferably, the step of sequentially performing a second bandpass filter and a second lowpass filter on the DC component of the second harmonic voltage to obtain the proportional error estimate includes: The DC component of the second harmonic voltage is subjected to a second bandpass filter to obtain a second lowpass filter signal. The second low-pass filter processing is performed on the second signal to be low-pass filtered to obtain the phase ratio error difference; The proportional error integral function is used to accumulate the interphase proportional error difference to obtain an estimated value of the interphase proportional error difference. The proportional error integral function is used to make the interphase proportional error difference tend to zero when it converges. Based on the estimated value of the phase ratio error difference, the estimated value of the ratio error is obtained.

[0012] Preferably, the center frequency of the first bandpass filter is the synchronization angular frequency of the distribution network; The center frequency of the second bandpass filter is twice the synchronization angular frequency of the power distribution network.

[0013] Secondly, the present invention also provides a doubly fed wind turbine low voltage ride-through control system to realize the doubly fed wind turbine low voltage ride-through control method described above. The system includes: a grid connection point voltage modeling module, a synchronization demodulation module, an error compensation module, and a low voltage ride-through control module. The grid connection point voltage modeling module is used to model the measured value of the grid connection point voltage of the target doubly fed wind turbine to obtain the theoretical measured value of the grid connection point voltage. The theoretical measured value of the grid connection point voltage is set to reflect the influence of the DC drift error of the voltage acquisition equipment used by the target doubly fed wind turbine and the proportional error of the voltage acquisition equipment on the grid connection point voltage. The synchronous demodulation module is used to sequentially convert the theoretical measured value of the grid connection point voltage after phase-locked loop processing into a fundamental frequency voltage component and a second harmonic voltage component, and sequentially perform band-pass filtering and low-pass filtering on the converted fundamental frequency voltage DC component and second harmonic voltage DC component, respectively, to obtain the DC drift error estimate and the proportional error estimate. The error compensation module is used to perform error compensation on the grid connection point voltage measurement value of the target doubly-fed wind turbine based on the proportional error estimate and the DC drift error estimate during low voltage ride-through control of the target doubly-fed wind turbine, so as to obtain the compensated grid connection point voltage measurement value. The low-voltage ride-through control module is used to control the low-voltage ride-through of the target doubly-fed wind turbine based on the compensated grid connection point voltage measurement value.

[0014] Thirdly, the present invention also provides a computer device, the computer device including a memory, a processor and a transceiver, which are connected to each other via a bus; the memory is used to store a set of computer program instructions and data, and to transmit the stored data to the processor, the processor executing the computer program instructions stored in the memory to execute the doubly fed wind turbine low voltage ride-through control method described above.

[0015] Fourthly, the present invention also provides a computer-readable storage medium storing a computer program that, when executed, implements the doubly-fed wind turbine low-voltage ride-through control method described above.

[0016] This application provides a low-voltage ride-through control method, system, device, and medium for doubly-fed wind turbines. Compared with the prior art, the beneficial effects of the embodiments of this application are as follows: The low-voltage ride-through control method for doubly-fed induction generator (DFIG) wind turbines disclosed in this application considers the DC drift and proportional error caused by the nonlinear characteristics of the voltage sensor, and establishes a three-phase voltage measurement error model for the DFIG wind turbine as an error term. Based on this, signal preprocessing, bandpass filtering, and low-pass filtering are performed on the theoretical measured values ​​of the d-axis voltage output by the phase-locked loop (PLL) to obtain the difference between the proportional error and DC drift in each phase. Finally, the voltage measurement error term is estimated through an integral function, achieving accurate assessment and compensation of the voltage measurement error. This effectively improves the low-voltage ride-through capability of the DFIG wind turbine, reduces the risk of wind power disconnection from the grid, and increases the safety margin for stable operation of the distribution network. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the steps of a doubly fed wind turbine low voltage ride-through control method according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the DC drift error estimate obtained by using the doubly fed wind turbine low voltage ride-through control method of this application, provided in a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the proportional error estimate obtained by the doubly fed wind turbine low voltage ride-through control method of this application, provided in a preferred embodiment of the present invention; Figure 4 This is a schematic diagram showing the comparison results between the grid connection point voltage measurement value with voltage measurement error compensation and the grid connection point voltage measurement value without voltage measurement error compensation, according to a preferred embodiment of the present invention. Figure 5 This is a schematic diagram comparing the simulation results of the doubly fed wind turbine low voltage ride-through control method of this application provided in a preferred embodiment of the present invention with the simulation results of the low voltage ride-through control method without voltage measurement error compensation. Figure 6 This is a schematic diagram of a low-voltage ride-through control system for a doubly-fed wind turbine provided in a preferred embodiment of the present invention; Figure 7 This is an internal structural diagram of the computer device in an embodiment of the present invention; Figure label: 1-Grid connection point voltage modeling module, 2-Synchronous demodulation module, 3-Error compensation module, 4-Low voltage ride-through control module. Detailed Implementation

[0018] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are provided for illustrative purposes only and should not be construed as limiting the scope of the invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of protection of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of this invention.

[0019] In the description of this invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] Please see Figure 1 The diagram illustrates the steps of a doubly-fed induction generator (DFIG) low-voltage ride-through control method. In an embodiment of the present invention, a DFIG low-voltage ride-through control method is provided, the method comprising: S1. Model the grid connection point voltage measurement value of the target doubly-fed induction generator (DFIG) to obtain the theoretical grid connection point voltage measurement value. This theoretical value is set to reflect the influence of the DC drift error and proportional error of the voltage acquisition equipment used by the DFIG on the grid connection point voltage. For DFIGs, since their stator side is directly connected to the grid, they are more susceptible to grid connection point voltage measurement errors. The low-voltage ride-through control method for DFIGs disclosed in this application addresses the voltage control deviation problem caused by the decreased perception of the grid voltage state after the DFIG is affected by grid connection point voltage measurement errors during low-voltage ride-through. Therefore, in a preferred embodiment of this application, a model of the theoretical grid connection point voltage measurement value considering the nonlinear characteristics of the voltage acquisition equipment used by the target DFIG is established. In typical converter control strategies for DFIGs, the dq voltage detection value of the phase-locked loop (PLL) is typically used as the grid connection point voltage measurement value for threshold judgment, and different control responses are made based on the grid connection point voltage measurement value sensed by the controller. When the voltage acquisition equipment detects that the grid connection point voltage is within a certain range... During this period, the doubly-fed induction generator (DFIG) adjusts the active current command based on the voltage on the DC bus. Its primary function is to output active power. Due to the principle of active power priority, the reactive power reference value is typically set to 0. The d-axis and q-axis current reference values ​​are then expressed as follows: in, This represents the d-axis current reference value, i.e., the active current command. This represents the q-axis current reference value, i.e., the reactive current command. This represents the proportional coefficient of the d-axis PI controller. Indicates the integral coefficient of the d-axis PI controller. This represents the proportional gain of the q-axis PI controller. This represents the integral coefficient of the q-axis PI controller. This indicates the reference value for the DC bus voltage. This represents the measured value of the DC bus voltage. This represents the reference value for reactive power. This indicates the measured value of reactive power.

[0021] The voltage acquisition device detected that the grid connection point voltage was at... When the voltage is within a certain range, it indicates a low-voltage fault in the distribution network. To maintain voltage stability at the grid connection point, the doubly-fed induction generator (DFIG) switches to reactive power priority mode, supplying reactive power to the distribution network through the converter until the distribution network voltage returns to normal. This is the low-voltage ride-through control process of the DFIG. At this time, the q-axis current reference value is expressed as: in, This represents the reactive current proportionality coefficient, which is usually taken as 1.5.

[0022] The d-axis current reference value is controlled by the converter capacity, and is expressed as: in, This indicates the maximum constraint current, which is the rated current capacity of the converter.

[0023] As can be seen from the expressions for the q-axis current reference value and d-axis current reference value in the low voltage ride-through control process of the doubly-fed induction generator (DFIG) above, they are related to the grid connection point voltage measurement value. Specifically, the lower the voltage of the grid connection point voltage measurement value sensed by the voltage sensor, the larger the reactive current command value, which is at most the maximum converter capacity output. When the grid connection point voltage measurement value is at 0.2 pu, the DFIG will input reactive current to the distribution network to the maximum extent to support the recovery of the grid connection point voltage.

[0024] Therefore, during the low-voltage ride-through process of the doubly-fed induction generator (DFIG), the accuracy of the current command depends on the accurate measurement of the grid connection voltage by the voltage acquisition equipment. Due to the existence of grid connection voltage measurement errors, the reactive current command is not in the maximum reactive power support mode at the beginning of the voltage drop in the distribution network. This causes the DFIG voltage to drop rapidly to below 0.2 pu after the low-voltage fault occurs, triggering the DFIG disconnection condition. At this time, the DFIG is disconnected from the distribution network. In a weak grid environment, large-scale disconnection of DFIGs will exacerbate the stability and safety of the distribution network operation.

[0025] Considering the non-ideal characteristics of voltage acquisition equipment, the actual measured value of the grid connection point voltage often contains proportional errors caused by gain deviation, temperature drift, aging, etc., and DC drift caused by zero-point drift, core remanence, circuit bias, etc. These non-linear errors caused by the non-ideal characteristics of the voltage acquisition equipment can be simplified into a combination of DC drift error and proportional error, as verified by factory calibration and benchmarking experiments. Therefore, this application models the grid connection point voltage measurement value of the target doubly-fed induction generator (DFIG) based on the influence of the proportional error and DC drift error of the voltage acquisition equipment on the measured value of the grid connection point voltage, obtaining the theoretical measured value of the grid connection point voltage, as specifically expressed below: in, express Theoretical measured value of phase-parallel grid point voltage. express Theoretical measured value of phase-parallel grid point voltage. express Theoretical measured value of phase-parallel grid point voltage. Indicates voltage acquisition equipment Phase ratio error, Indicates voltage acquisition equipment Phase ratio error, Indicates voltage acquisition equipment Phase ratio error, Indicates the amplitude of the fundamental phase voltage in the distribution network. Indicates voltage acquisition equipment Phase DC drift error, Indicates voltage acquisition equipment Phase DC drift error, Indicates voltage acquisition equipment Phase DC drift error.

[0026] S2. The theoretical measured value of the grid connection point voltage output after phase-locked loop processing is sequentially converted into a fundamental frequency voltage component and a second harmonic voltage component. The resulting fundamental frequency DC component and second harmonic DC component are then sequentially subjected to band-pass filtering and low-pass filtering, respectively, to obtain the DC drift error estimate and proportional error estimate. In a preferred embodiment of this application, a simulation of low-voltage ride-through control of a doubly-fed induction generator (DFIG) is performed. After the theoretical measured value of the grid connection point voltage is transformed by the phase-locked loop (PLL), the d-axis output voltage of the theoretical measured value of the grid connection point voltage is expressed as follows: in, Indicates the phase of the phase-locked loop. Indicates the phase of the distribution network.

[0027] When the phase-locked loop is stable, the d-axis output voltage of the theoretically measured grid connection point voltage can be minimized. The minimization formula is as follows: in, This indicates the phase error of the phase-locked loop.

[0028] The expression for the d-axis voltage theoretical measurement value of the grid connection point voltage after minimization is: From the expression of the d-axis voltage theoretical measurement value after minimization, it can be seen that the fundamental frequency voltage component and the second harmonic voltage component introduced by the proportional error and DC drift error in the d-axis voltage theoretical measurement value are expressed as follows: in, This represents the DC voltage component of the theoretically measured d-axis voltage. This represents the fundamental voltage component of the theoretically measured d-axis voltage. Indicates the synchronization angular frequency of the distribution network. This represents the error component introduced by the phase error of the phase-locked loop.

[0029] In a preferred embodiment of this application, the influence of the proportional error and DC drift error of the voltage acquisition equipment used by the target doubly-fed wind turbine on the grid connection point voltage measurement value of the target doubly-fed wind turbine is modeled, which fully considers the influence of the grid connection point voltage measurement error on the control command and improves the accuracy of the subsequent low voltage ride-through control of the doubly-fed wind turbine.

[0030] In a preferred embodiment of this application, since the error component introduced by the phase-locked loop (PLL) error is very small and can be ignored, the theoretically measured value of the grid connection point voltage is synchronously demodulated. The purpose is to convert the fundamental frequency voltage component into a DC component or a low-frequency component, and to convert the second harmonic voltage component into a DC component or a low-frequency component. Specifically, based on the fundamental frequency voltage component and the second harmonic voltage component, a first voltage error processing factor for the fundamental frequency voltage component and a second voltage error processing factor for the second harmonic voltage component are determined. Multiplying the first voltage error processing factor by the fundamental frequency voltage component converts the fundamental frequency voltage component into a DC component or a low-frequency component. Multiplying the second voltage error processing factor by the second harmonic voltage component converts the second harmonic voltage component into a DC component or a low-frequency component. The first voltage error processing factor includes... and The second voltage error processing factor includes and The theoretical measured values ​​of the grid connection point voltage are preprocessed using the first voltage error processing factor to obtain the DC component of the fundamental frequency voltage of the theoretical measured values ​​of the grid connection point voltage. The DC component of the fundamental frequency voltage is expressed as follows: From the expression for the DC component of the fundamental frequency voltage, it can be seen that the DC component mainly includes a DC term and a high-frequency oscillation term, where the DC term is... The high-frequency oscillation term is a second harmonic component. For the high-frequency oscillation term, a low-pass filter can be used to filter it out.

[0031] In actual grid-connected voltage measurement operations, many higher-frequency harmonics are involved. The combination of proportional error and voltage harmonics caused by other electronic components will generate in the synchronous dq reference coordinate system. The AC component, therefore a center frequency of is used. The first bandpass filter removes higher harmonics from the DC component of the fundamental frequency voltage. The first bandpass filter in... The transfer function over the domain is: in, Indicates that the first bandpass filter is in Transfer function on a domain Represents the Laplace variable. This indicates the bandwidth of the first bandpass filter.

[0032] Furthermore, a first low-pass filter is used to perform low-pass filtering on the output of the first band-pass filter to filter out high-frequency oscillation terms. The first low-pass filter... The transfer function over the domain is: in, Indicates the first low-pass filter in Transfer function on a domain This indicates the cutoff frequency of the first low-pass filter.

[0033] The output of the first low-pass filter is shown below: Ultimately, we can obtain Harmony The difference in DC drift error between phases. Harmony The difference in DC drift error between phases.

[0034] For the second harmonic voltage component, a second voltage error processing factor is used to preprocess the data of the second harmonic voltage component. After repeating this process several times, the second harmonic voltage DC component of the theoretically measured grid connection point voltage is obtained. The second harmonic voltage DC component is expressed as: in, , .

[0035] At this time, the center frequency is used. The second bandpass filter removes higher harmonics from the DC component of the second harmonic voltage. The transfer function over the domain is: in, Indicates the second bandpass filter in Transfer function on a domain This indicates the bandwidth of the second bandpass filter.

[0036] Furthermore, a second low-pass filter is used to perform low-pass filtering on the output of the second band-pass filter to filter out high-frequency oscillation terms. The second low-pass filter... The transfer function over the domain is: in, Indicates the second low-pass filter in Transfer function on a domain This indicates the cutoff frequency of the second low-pass filter.

[0037] The output of the second low-pass filter is shown below: The output result after processing by the second low-pass filter shows that... and If there is a 4:1 ratio, then it can be used in the error estimation loop. and The DC component of the double-frequency voltage is compensated, and the compensated output result is: Ultimately, we can obtain Harmony Interphase ratio error Harmony The phase ratio error between phases.

[0038] To accurately estimate the proportional error and DC drift error, a proportional-integral function is used. Harmony The difference in phase ratio error between phases, and Harmony The interphase proportional error differences between phases are accumulated until they converge to zero, thus obtaining the corresponding... Harmony Estimated value of the interphase proportional error difference between phases. Harmony Estimate the phase-to-phase proportional error difference; using the DC drift error integral function, for Harmony The difference in DC drift error between phases, and Harmony The phase-to-phase DC drift error difference is accumulated to obtain the corresponding result. Harmony Estimated value of the interphase DC drift error difference between phases. Harmony Estimated value of the interphase DC drift error difference. In the factory calibration of voltage acquisition equipment, one phase is used as the reference, for example... Phase as a reference, that is, setting , Then, based on the estimated values ​​of the phase-to-phase proportional error and the phase-to-phase DC drift error difference, the estimated values ​​of the proportional error and DC drift error for each phase are obtained.

[0039] S3. In the low-voltage ride-through control of the target doubly-fed induction generator (DFIG), the grid connection point voltage measurement of the target DFIG is compensated for error based on the proportional error estimate and the DC drift error estimate to obtain the compensated grid connection point voltage measurement. In the actual low-voltage ride-through control of the target DFIG, the proportional error estimate and the DC drift error estimate are compensated to the measurement port of the voltage controller to compensate for the error of the grid connection point voltage measurement of the target DFIG, thereby improving the accuracy of the grid connection point voltage measurement and obtaining the compensated grid connection point voltage measurement.

[0040] S4. Based on the compensated grid connection point voltage measurement value, control the low voltage ride-through of the target doubly-fed wind turbine; in a preferred embodiment of this application, determine the range of the compensated grid connection point voltage measurement value, if the compensated grid connection point voltage measurement value is within... The range indicates that a low-voltage fault has occurred in the distribution network. The doubly-fed induction generator (DFIG) switches to reactive power priority mode and provides reactive power to the distribution network through the converter until the distribution network voltage returns to normal. This ensures the accuracy and reliability of the DFIG low-voltage ride-through control under the influence of voltage measurement errors and guarantees the stability of the distribution network.

[0041] In a preferred embodiment of this application, the low voltage ride-through control method for doubly fed wind turbines disclosed in this application is simulated, and the simulation parameters are shown in Table 1.

[0042] Table 1 Simulation Parameters The calculated proportional error estimates and DC drift error estimates are shown in Table 2.

[0043] Table 2 Error Parameters like Figure 2 The figure shown is a schematic diagram of the DC drift error estimate obtained using the doubly-fed wind turbine low-voltage ride-through control method of this application. Figure 3 The diagram shows the proportional error estimate obtained using the doubly-fed wind turbine low-voltage ride-through control method of this application. Figure 2 and Figure 3 It can be seen that the doubly fed wind turbine low voltage ride-through control method of this application accurately achieves the estimation of error after a certain period of adjustment.

[0044] like Figure 4 The diagram shown is a comparison of the grid connection point voltage measurement values ​​with and without voltage measurement error compensation, as described in this application. Figure 5The diagram shows a comparison between the simulation results of the doubly-fed induction generator (DFIG) low-voltage ride-through control method and the simulation results of the low-voltage ride-through control method without voltage measurement error compensation. Figure 4 As can be seen, when the doubly-fed induction generator (DFIG) low-voltage ride-through control method of this application is initiated at 0.4s, after a certain delay, compared with the method without voltage measurement error compensation, the high-frequency oscillation amplitude of the grid connection point voltage measurement value of this application gradually narrows, and significantly reduces the oscillation amplitude after stabilization. From Figure 5 As can be seen, when the doubly-fed induction generator (DFIG) experiences a low-voltage ride-through fault at 1 second, the grid connection voltage drops rapidly. Without voltage measurement error compensation, the grid connection voltage would quickly drop below 0.2 pu, triggering the turbine disconnection mechanism. However, with the DFIG low-voltage ride-through control method of this application, the reactive current command can respond promptly to changes in the distribution network voltage and quickly switch to the maximum reactive power support strategy for low-voltage ride-through. The voltage drop is suppressed, and the voltage rise is significant, reaching 0.21 pu. The DFIG successfully overcomes the low-voltage ride-through fault process, significantly enhancing the DFIG's low-voltage ride-through capability.

[0045] In a preferred embodiment of the present invention, the grid connection point voltage measurement value of the target doubly-fed induction generator (DFIG) is modeled to obtain the theoretical grid connection point voltage measurement value. The theoretical grid connection point voltage measurement value is set to reflect the influence of the DC drift error of the voltage acquisition equipment used by the target DFIG and the proportional gain temperature difference of the voltage acquisition equipment on the grid connection point voltage. The theoretical grid connection point voltage measurement value output after phase-locked loop processing is sequentially converted to the fundamental frequency voltage component and then to the second harmonic voltage component. The converted fundamental frequency DC component and the second harmonic DC component are then sequentially subjected to bandpass filtering and low-pass filtering, respectively, to obtain the DC drift error estimate and the proportional gain estimate. In the low-voltage ride-through control of the target DFIG, the grid connection point voltage measurement value of the target DFIG is error-compensated based on the proportional gain estimate and the DC drift error estimate to obtain the compensated grid connection point voltage measurement value. Based on the compensated grid connection point voltage measurement value, the operating mode of the target DFIG is determined to perform low-voltage ride-through control on the target DFIG. The low-voltage ride-through control method for doubly-fed induction generator (DFIG) wind turbines disclosed in this application considers the DC drift and proportional error caused by the nonlinear characteristics of the voltage sensor, and establishes a three-phase voltage measurement error model for the DFIG wind turbine as an error term. Based on this, signal preprocessing, bandpass filtering, and low-pass filtering are performed on the theoretical measured values ​​of the d-axis voltage output by the phase-locked loop (PLL) to obtain the difference between the proportional error and DC drift in each phase. Finally, the voltage measurement error term is estimated through an integral function, achieving accurate assessment and compensation of the voltage measurement error. This effectively improves the low-voltage ride-through capability of the DFIG wind turbine, reduces the risk of wind power disconnection from the grid, and increases the safety margin for stable operation of the distribution network.

[0046] Accordingly, such as Figure 6 The diagram shown is a structural schematic of a doubly-fed induction generator (DFIG) low-voltage ride-through control system. Based on a DFIG low-voltage ride-through control method, this embodiment of the invention also provides a DFIG low-voltage ride-through control system to implement the DFIG low-voltage ride-through control method disclosed in this embodiment. The system includes: a grid connection point voltage modeling module 1, a synchronization demodulation module 2, an error compensation module 3, and a low-voltage ride-through control module 4. The grid connection point voltage modeling module 1 is used to model the measured value of the grid connection point voltage of the target doubly fed wind turbine to obtain the theoretical measured value of the grid connection point voltage. The theoretical measured value of the grid connection point voltage is set to reflect the influence of the DC drift error of the voltage acquisition equipment used by the target doubly fed wind turbine and the proportional error of the voltage acquisition equipment on the grid connection point voltage. The synchronous demodulation module 2 is used to sequentially convert the theoretical measured value of the grid connection point voltage after phase-locked loop processing into a fundamental frequency voltage component and a second harmonic voltage component, and sequentially perform band-pass filtering and low-pass filtering on the converted fundamental frequency voltage DC component and second harmonic voltage DC component, respectively, to obtain the DC drift error estimate and the proportional error estimate. The error compensation module 3 is used to perform error compensation on the grid connection point voltage measurement value of the target doubly-fed wind turbine based on the proportional error estimate and the DC drift error estimate during low voltage ride-through control of the target doubly-fed wind turbine, so as to obtain the compensated grid connection point voltage measurement value. The low voltage ride-through control module 4 is used to control the low voltage ride-through of the target doubly fed wind turbine based on the compensated grid connection point voltage measurement value.

[0047] Specific limitations regarding a doubly-fed induction generator (DFIG) low-voltage ride-through control system can be found in the above-described limitations regarding a DFIG low-voltage ride-through control method, and will not be repeated here. Those skilled in the art will recognize that the various modules and steps described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention.

[0048] like Figure 7The diagram shows the internal structure of a computer device. An embodiment of the present invention provides a computer device including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the steps described in the embodiment of the doubly-fed wind turbine low-voltage ride-through control method as described above. Figure 1 Steps S1 to S4 as described above.

[0049] Those skilled in the art will understand that the illustrations Figure 7 This is merely an example of a computer device and does not constitute a limitation on the computer device. It may include more or fewer components than shown, or combine certain components, or different components. For example, the computer device may also include input / output devices, network access devices, buses, etc.

[0050] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the computer device, connecting various parts of the computer device via various interfaces and lines.

[0051] The memory can be used to store the computer programs and / or modules. The processor implements various functions of the computer device by running or executing the computer programs and / or modules stored in the memory and by calling data stored in the memory. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, phonebook, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0052] If the modules integrated into the computer device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0053] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0054] Accordingly, embodiments of the present invention provide a computer-readable storage medium, the computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform the steps described in the embodiments of the doubly-fed wind turbine low-voltage ride-through control method as described above, for example... Figure 1 Steps S1 to S4 as described above.

[0055] In summary, the present application provides a low-voltage ride-through control method, system, device, and medium for doubly-fed induction generator (DFIG) wind turbines, addressing the technical problem of improving the low-voltage ride-through capability of DFIG wind turbines. The method includes: modeling the grid connection point voltage measurement value of the target DFIG wind turbine to obtain a theoretical grid connection point voltage measurement value, which is set to reflect the influence of the DC drift error of the voltage acquisition equipment used in the target DFIG wind turbine and the proportional temperature difference of the voltage acquisition equipment on the grid connection point voltage; and sequentially performing fundamental frequency voltage component conversion and two-phase-locked loop (PLL) processing on the theoretical grid connection point voltage measurement value output. The voltage components are converted using a frequency multiplication method. The resulting DC component of the fundamental frequency voltage and the DC component of the second frequency multiplication method are then subjected to bandpass filtering and low-pass filtering, respectively, to obtain the DC drift error estimate and the proportional error estimate. In the low-voltage ride-through control of the target doubly-fed induction generator (DFIG), the grid connection point voltage measurement of the target DFIG is compensated based on the proportional error estimate and the DC drift error estimate to obtain the compensated grid connection point voltage measurement. Based on the compensated grid connection point voltage measurement, the operating mode of the target DFIG is determined to perform low-voltage ride-through control on the target DFIG. The low-voltage ride-through control method for doubly-fed induction generator (DFIG) wind turbines disclosed in this application considers the DC drift and proportional error caused by the nonlinear characteristics of the voltage sensor, and establishes a three-phase voltage measurement error model for the DFIG wind turbine as an error term. Based on this, signal preprocessing, bandpass filtering, and low-pass filtering are performed on the theoretical measured values ​​of the d-axis voltage output by the phase-locked loop (PLL) to obtain the difference between the proportional error and DC drift in each phase. Finally, the voltage measurement error term is estimated through an integral function, achieving accurate assessment and compensation of the voltage measurement error. This effectively improves the low-voltage ride-through capability of the DFIG wind turbine, reduces the risk of wind power disconnection from the grid, and increases the safety margin for stable operation of the distribution network.

[0056] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts of the embodiments, refer to each other. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0057] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A low-voltage ride-through control method for a doubly-fed induction generator (DFIG), characterized in that, The method includes: Modeling is performed on the grid connection point voltage measurement value of the target doubly-fed wind turbine to obtain the theoretical grid connection point voltage measurement value. The theoretical grid connection point voltage measurement value is set to reflect the influence of the DC drift error of the voltage acquisition equipment used by the target doubly-fed wind turbine and the proportional error of the voltage acquisition equipment on the grid connection point voltage. The theoretical measured value of the grid connection point voltage output after phase-locked loop processing is sequentially converted into a fundamental frequency voltage component and a second harmonic voltage component. The converted fundamental frequency DC component and second harmonic DC component are then sequentially subjected to band-pass filtering and low-pass filtering, respectively, to obtain the DC drift error estimate and the proportional error estimate. In the low voltage ride-through control of the target doubly-fed wind turbine, the grid connection point voltage measurement value of the target doubly-fed wind turbine is compensated for error based on the proportional error estimate and the DC drift error estimate, so as to obtain the compensated grid connection point voltage measurement value. Based on the compensated grid connection point voltage measurement, the low voltage ride-through of the target doubly fed wind turbine is controlled.

2. The doubly-fed induction generator (DFIG) low-voltage ride-through control method as described in claim 1, characterized in that, The process of modeling the grid connection point voltage measurement value of the target doubly-fed wind turbine to obtain the theoretical measurement value of the grid connection point voltage includes: Error analysis was performed on the voltage acquisition equipment used in the target doubly fed wind turbine to obtain the error terms of the voltage acquisition equipment, which include proportional error and DC drift error. Based on the proportional error and the DC drift error, the grid connection point voltage measurement value of the target doubly fed wind turbine is modeled to obtain the theoretical measurement value of the grid connection point voltage.

3. The low-voltage ride-through control method for a doubly-fed wind turbine as described in claim 1, characterized in that, The theoretically measured grid-connected voltage value output after phase-locked loop processing is sequentially converted to its fundamental frequency voltage component and then to its second harmonic voltage component. The resulting fundamental frequency DC component and second harmonic DC component are then sequentially subjected to bandpass filtering and low-pass filtering, respectively, to obtain DC drift error estimates and proportional error estimates, including: The theoretical measured value of the grid connection point voltage is sequentially subjected to phase-locked processing and minimization processing to obtain the theoretical measured value of the d-axis voltage of the theoretical measured value of the grid connection point voltage. The theoretical measured values ​​of the d-axis voltage are analyzed to determine the fundamental frequency voltage component introduced by the DC drift error and the second harmonic voltage component introduced by the proportional error in the theoretical measured values ​​of the d-axis voltage. Based on the fundamental frequency voltage component, a first voltage error processing factor for the fundamental frequency voltage component is determined, and based on the second harmonic voltage component, a second voltage error processing factor for the second harmonic voltage component is determined. The first voltage error processing factor is set to convert the fundamental frequency voltage component into a DC component, and the second voltage error processing factor is set to convert the second harmonic voltage component into a DC component. The fundamental frequency voltage component is preprocessed using the first voltage error processing factor to obtain the fundamental frequency voltage DC component of the theoretical measured value of the grid connection point voltage. The fundamental frequency voltage DC component is then subjected to a first bandpass filter and a first low-pass filter in sequence to obtain the DC drift error estimate. The second voltage error processing factor is used to preprocess the second harmonic voltage component to obtain the second harmonic voltage DC component of the theoretical measured value of the grid connection point voltage. The second harmonic voltage DC component is then subjected to a second bandpass filter and a second low-pass filter to obtain the proportional error estimate.

4. The doubly-fed induction generator (DFIG) low-voltage ride-through control method as described in claim 3, characterized in that, The first voltage error processing factor includes and ; The second voltage error processing factor includes and .

5. The doubly-fed induction generator (DFIG) low-voltage ride-through control method as described in claim 3, characterized in that, The step of sequentially performing a first bandpass filter and a first lowpass filter on the DC component of the fundamental frequency voltage to obtain a DC drift error estimate includes: The DC component of the fundamental frequency voltage is subjected to a first bandpass filter to obtain a first lowpass filter signal. The first low-pass filter processing is performed on the first signal to be low-pass filtered to obtain the phase-to-phase DC drift error difference; The DC drift error integral function is used to accumulate the interphase DC drift error difference to obtain an estimated value of the interphase DC drift error difference. The DC drift error integral function is used to make the interphase DC drift error difference approach zero when it converges. Based on the estimated value of the interphase DC drift error difference, the estimated value of the DC drift error is obtained.

6. The doubly-fed induction generator (DFIG) low-voltage ride-through control method as described in claim 3, characterized in that, The step of sequentially performing a second bandpass filter and a second lowpass filter on the DC component of the second harmonic voltage to obtain a proportional error estimate includes: The DC component of the second harmonic voltage is subjected to a second bandpass filter to obtain a second lowpass filter signal. The second low-pass filter processing is performed on the second signal to be low-pass filtered to obtain the phase ratio error difference; The proportional error integral function is used to accumulate the interphase proportional error difference to obtain an estimated value of the interphase proportional error difference. The proportional error integral function is used to make the interphase proportional error difference tend to zero when it converges. Based on the estimated value of the phase ratio error difference, the estimated value of the ratio error is obtained.

7. The doubly-fed induction generator (DFIG) low-voltage ride-through control method as described in claim 5 or claim 6, characterized in that, The center frequency of the first bandpass filter is the synchronization angular frequency of the distribution network; The center frequency of the second bandpass filter is twice the synchronization angular frequency of the power distribution network.

8. A doubly-fed induction generator (DFIG) low-voltage ride-through control system, used to implement the DFIG low-voltage ride-through control method according to any one of claims 1-7, characterized in that, The system includes: a grid connection point voltage modeling module, a synchronous demodulation module, an error compensation module, and a low voltage ride-through control module; The grid connection point voltage modeling module is used to model the measured value of the grid connection point voltage of the target doubly fed wind turbine to obtain the theoretical measured value of the grid connection point voltage. The theoretical measured value of the grid connection point voltage is set to reflect the influence of the DC drift error of the voltage acquisition equipment used by the target doubly fed wind turbine and the proportional error of the voltage acquisition equipment on the grid connection point voltage. The synchronous demodulation module is used to sequentially convert the theoretical measured value of the grid connection point voltage after phase-locked loop processing into a fundamental frequency voltage component and a second harmonic voltage component, and sequentially perform band-pass filtering and low-pass filtering on the converted fundamental frequency voltage DC component and second harmonic voltage DC component, respectively, to obtain the DC drift error estimate and the proportional error estimate. The error compensation module is used to perform error compensation on the grid connection point voltage measurement value of the target doubly-fed wind turbine based on the proportional error estimate and the DC drift error estimate during low voltage ride-through control of the target doubly-fed wind turbine, so as to obtain the compensated grid connection point voltage measurement value. The low-voltage ride-through control module is used to control the low-voltage ride-through of the target doubly-fed wind turbine based on the compensated grid connection point voltage measurement value.

9. A computer device, characterized in that: The computer device includes a memory, a processor, and a transceiver connected to each other via a bus; the memory stores a set of computer program instructions and data, and transmits the stored data to the processor, which executes the computer program instructions stored in the memory to perform the doubly-fed wind turbine low-voltage ride-through control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program that, when executed, implements the doubly-fed wind turbine low-voltage ride-through control method as described in any one of claims 1 to 7.

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