A method for suppressing active circulating current of grid-side converter of grid-type wind turbine
Through the active circulation suppression method of the grid-type fan network-side converter, the virtual admission parameters and voltage limit value are adjusted by combining modules such as the power outer ring module and virtual admission module, which solves the problem of active circulation of the wind turbine under the uncontrolled rectified converter station, and improves the safety of the wind farm.
Patent Information
- Application Number
- CN202510088899.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-21
- Publication Date
- 2025-04-08
AI Technical Summary
Under the topology of uncontrolled rectified converter stations, when a short circuit failure occurs in the onshore power grid, the wind turbine may experience active circulation, affecting the safety of the wind farm.
The active circulation suppression method of the network-side converter of the network fan network is adopted. Through the combination of the power outer ring module, the virtual admission module, the current control module and the coordinate inverse conversion module, the parameters and voltage limit value of the virtual admission are adjusted to suppress the active circulation.
It effectively suppresses the active circulation phenomenon of the wind turbine during the failure period, and improves the safety and stability of the wind turbine.
Smart Images
Figure CN119787466A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of renewable energy power generation, and in particular to a method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine. Background Art
[0002] At present, the topology type selected by the sending-end station in the offshore new energy system is mainly based on modular multi-level converter stations. However, for offshore wind farms in the far sea, the sending-end station uses uncontrolled rectifier converter stations to convert to DC for long-distance transmission, which is currently the most cost-effective and competitive solution. However, due to the uncontrolled characteristics of uncontrolled rectifier converter stations, under this solution, wind turbines are usually required to have the ability to build a network.
[0003] Under the existing uncontrolled rectifier converter station topology, the grid-type control mode of the grid-side converter of a typical wind power system is the first layer power loop, the second layer is the voltage outer loop, and the third layer is the current inner loop. In recent years, virtual impedance has been widely used in the control system of grid-connected inverters. Virtual impedance realizes the control of grid-connected inverters by simulating interface impedance and has been widely used in the field of new energy. Therefore, the voltage outer loop can be replaced by a virtual impedance loop in the control of the grid-side converter of the wind power system.
[0004] Under the uncontrolled rectifier converter station topology, the method used to carry out fault ride-through under the onshore AC bus short-circuit fault is often to install energy-consuming devices between the sending station and the receiving station to absorb the unbalanced power, but the impact on the wind farm system when the energy-consuming devices are withdrawn is often ignored. Due to the grid-type control of wind turbines under the uncontrolled rectifier converter station topology, the power loop adopts the active voltage and reactive frequency method. Therefore, when the active power output of wind turbines is unequal, a short-circuit fault occurs in the onshore power grid and the energy-consuming devices are withdrawn, active circulation will be formed between the wind turbines, which is not conducive to the safety of the wind turbines. Summary of the invention
[0005] The purpose of the present invention is to provide a method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine, which can solve the phenomenon of active circulating current in a wind turbine during a fault and improve the safety of the wind turbine.
[0006] To achieve the above object, the present invention is implemented through the following technical solutions:
[0007] A method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine comprises:
[0008] S1, the power outer loop module gives P according to the active power of the grid-side converter of the grid-type wind turbine ref Signal, reactive power given Q ref Signal generation AC voltage given amplitude E peakThe signal and phase θ are transmitted to the virtual admittance module, and the AC voltage is given an amplitude E peak The amplitude is adjusted according to the active power of the wind turbine grid-side converter;
[0009] S2, the virtual admittance module is given an amplitude E according to the AC voltage generated by the previous power outer loop module peak signal and phase θ, generating the current given I of the dq axis dref ,I qref The signal is transmitted to the current control module, and the virtual resistance parameters are adjusted according to the active power;
[0010] S3, the current control module is based on the current given by the dq axis of the previous virtual admittance module I dref ,I qref Signal, generate modulation signals vd, vq in the rotating coordinate system, and transmit them to the coordinate inverse transformation module;
[0011] S4, the coordinate inverse transformation module is used to generate the three-phase modulation signal V of the wind turbine grid-side converter ref_abc , and transmitted to the wind turbine grid-side converter.
[0012] In S1, the power outer loop module includes a limit value adjustment module, an active voltage module, a voltage limit module, and a reactive frequency module. The contents are as follows:
[0013] S11, active voltage module includes PI controller, the active power of wind turbine grid-side converter is given by P ref Signal and active power feedback P fbk The signal is subtracted and the PI controller generates the d-axis voltage set value E. dref The signal is transmitted to the voltage limiting module;
[0014] S12, voltage limit module includes limiter, d-axis voltage given value E dref The signal passes through the limiter to generate an AC voltage with a given amplitude E. peak The signal is transmitted to the virtual admittance module;
[0015] S13, reactive frequency module includes low-pass filter and integration module, the reactive power of wind turbine grid-side converter is given by Q ref Signal and reactive power feedback Q fbk The angular frequency ω of the wind turbine grid-side converter is generated through a low-pass filter. The angular frequency ω of the wind turbine grid-side converter is different from the rated angular frequency ω. 0 The phase θ of the wind turbine grid-side converter is generated after the addition passes through the integration module, and the phase θ of the wind turbine grid-side converter is transmitted to the virtual admittance module and the coordinate inverse transformation module respectively;
[0016] S14, the amplitude limit value adjustment module includes an amplitude limit adjustment circuit for setting the d-axis voltage given value E in the voltage amplitude limit module. dref Amplitude provides compensation ΔU dref value.
[0017] In S2, the input signal of the virtual admittance module is the given amplitude of the AC voltage E peak The signal and the phase θ of the wind turbine grid-side converter are transformed into a three-phase given voltage E A 、E B 、E C signal, and the three-phase feedback U a , U b , U c The signal is subtracted and a three-phase current given signal is generated through a first-order low-pass function. The three-phase current given signal is transformed into a dq axis current given signal I dref ,I qref Signal, dq axis current given I dref ,I qref The signal is sent to the current control module.
[0018] The virtual resistance parameters of the virtual admittance module are adjusted by the virtual resistance parameter adjustment module:
[0019] The virtual resistance parameter adjustment module uses the active power given signal P of the wind turbine grid-side converter ref signal and active power feedback signal P fbk The difference of the signal is used to adjust the virtual resistance parameter R vir The size of the virtual resistance parameter R vir The signal is transmitted to the virtual admittance module;
[0020] The virtual resistance parameter selects upper resistance.
[0021] In S14, the direction of the active power of the wind turbine grid-side converter is used to determine whether the d-axis voltage given value E in the voltage limiting module is set. dref Amplitude provides compensation ΔU dref value:
[0022] The positive direction of the active power output by the wind turbine grid-side converter is based on the current output;
[0023] When the active power direction of the wind turbine grid-side converter is in the positive direction, no compensation is performed;
[0024] When the active power of the wind turbine grid-side converter is in the negative direction, compensation is performed;
[0025] Among them, compensation ΔU dref The value is the absolute value of the active power of the wind turbine grid-side converter.
[0026] According to the active power feedback P of the wind turbine grid-side converter fbk To adjust the limit value in the voltage limit module, when the active power feedback P fbk When the direction is negative, by compensating ΔU dref The output voltage of the converter is raised by adjusting the current value to avoid the backflow of active power of the wind turbine grid-side converter.
[0027] The active circulating current suppression system of the grid-side converter of a grid-type wind turbine comprises a power outer loop module, a virtual admittance module, a current control module and a coordinate inverse transformation module. The output end of the power outer loop module is respectively connected to the virtual admittance module and the coordinate inverse transformation module, the output end of the virtual admittance module is connected to the input end of the current control module, the output end of the current control module is connected to the input end of the coordinate inverse transformation module, and the output signal of the coordinate inverse transformation module is sent to the grid-side converter of the wind turbine.
[0028] The power outer loop module includes a limit value adjustment module, an active voltage module, a voltage limit module, and a reactive frequency module. The output end of the limit value adjustment module is connected to the voltage limit module, the output end of the active voltage module is connected to the voltage limit module, and the voltage limit module outputs an AC voltage with a given amplitude E. peak signal, connected to the input terminal of the virtual admittance module;
[0029] The input end of the limit value adjustment module is connected to the active power feedback P of the wind turbine grid-side converter. fbk Signal connection;
[0030] The input terminal of the active voltage module is connected to the active power given by the wind turbine grid-side converter P ref Signal and active power feedback P fbk Signal connection;
[0031] The reactive power given by the reactive frequency module input terminal and the wind turbine grid-side converter is Q ref Signal and reactive power feedback Q fbk The reactive frequency module outputs the phase θ of the wind turbine grid-side converter, which is connected to the virtual admittance module and the coordinate inverse transformation module respectively.
[0032] It also includes a virtual resistance parameter adjustment module, which is connected to the virtual admittance module.
[0033] Compared with the prior art, the present invention has the following beneficial effects:
[0034] 1. In the hybrid DC transmission system composed of uncontrolled rectifier converter station and modular multi-point flat converter station used in offshore wind power, compared with the conventional power loop + voltage outer loop + current inner loop control method, replacing the voltage outer loop with a virtual admittance loop can simulate the impedance characteristics of the converter. By adjusting the parameters of the virtual admittance to adjust the port characteristics of the converter, it is beneficial to the stability of the wind turbine grid-side converter;
[0035] 2. Voltage limit value module: When active circulating current occurs in the wind turbine, the voltage amplitude of the wind turbine grid-side converter is adjusted to suppress active circulating current;
[0036] 3. The combination of active limiting module and virtual resistance parameter adjustment module can achieve excellent active circulating current suppression effect in both transient and steady states during the failure of the onshore circulating current station. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Figure 1 Schematic diagram of the structure of the active circulating current suppression system of the grid-side converter of the grid-type wind turbine.
[0038] Figure 2 Schematic diagram of the limit value adjustment module.
[0039] Figure 3 Schematic diagram of the virtual resistance parameter adjustment module.
[0040] Figure 4 Structural topology diagram of two wind turbines based on DRU-MMC topology.
[0041] Figure 5 This is a simulation result diagram without the limit value adjustment module and the virtual resistance parameter adjustment module.
[0042] Figure 6 This is a simulation result diagram with a limit value adjustment module.
[0043] Figure 7 This is a simulation result diagram with a virtual resistance parameter adjustment module.
[0044] Figure 8 It is a simulation result diagram with a limit value adjustment module and a virtual resistance parameter adjustment module. DETAILED DESCRIPTION
[0045] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.
[0046] A method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine comprises:
[0047] The power outer loop module gives P according to the active power of the grid-side converter of the grid-type wind turbine. refSignal and reactive power given Q ref Signal generation AC voltage given amplitude E peak The signal and phase θ are transmitted to the virtual admittance module, and the AC voltage is given an amplitude E peak The amplitude is adjusted according to the active power of the wind turbine grid-side converter; the power outer loop module includes the limit value adjustment module, active voltage module, voltage limit module, and reactive frequency module, the contents of which are as follows:
[0048] S11, active voltage module includes PI controller, the active power of wind turbine grid-side converter is given by P ref Signal and active power feedback P fbk The signal is subtracted and the PI controller generates the d-axis voltage set value E. dref The signal is transmitted to the voltage limiting module;
[0049] S12, voltage limit module includes limiter, d-axis voltage given value E dref The signal passes through the limiter to generate an AC voltage with a given amplitude E. peak The signal is transmitted to the virtual admittance module;
[0050] S13, reactive frequency module includes low-pass filter and integration module, the reactive power of wind turbine grid-side converter is given by Q ref Signal and reactive power feedback Q fbk The angular frequency ω of the wind turbine grid-side converter is generated through a low-pass filter. The angular frequency ω of the wind turbine grid-side converter is different from the rated angular frequency ω. 0 The phase θ of the wind turbine grid-side converter is generated after the addition passes through the integration module, and the phase θ of the wind turbine grid-side converter is transmitted to the virtual admittance module and the coordinate inverse transformation module respectively;
[0051] S14, the amplitude limit value adjustment module includes an amplitude limit adjustment circuit for setting the d-axis voltage given value E in the voltage amplitude limit module. dref Amplitude provides compensation ΔU dref value;
[0052] The direction of the active power of the wind turbine grid-side converter is used to determine whether the d-axis voltage setting value E in the voltage limiting module is set. dref Amplitude provides compensation ΔU dref value:
[0053] The positive direction of the active power of the wind turbine grid-side converter is based on the current output.
[0054] When the active power direction of the wind turbine grid-side converter is in the positive direction, no compensation is performed;
[0055] When the active power direction of the wind turbine grid-side converter is negative, compensation is performed; according to the active power feedback P of the wind turbine grid-side converterfbk To adjust the limit value in the voltage limit module, when the active power feedback P fbk When the direction is negative, by compensating ΔU dref The value is used to raise the output voltage of the converter to avoid the backflow of active power of the wind turbine grid-side converter;
[0056] Among them, compensation ΔU dref The value is the absolute value of the active power of the wind turbine grid-side converter.
[0057] S2, the virtual admittance module is given an amplitude E according to the AC voltage generated by the previous power outer loop module peak The signal and the phase θ of the wind turbine grid-side converter generate the current given by the dq axis I dref ,I qref The signal is transmitted to the current control module, and the virtual resistance parameters are adjusted according to the active power;
[0058] The input signal of the virtual admittance module is the given amplitude of the AC voltage E peak The signal and the phase θ of the wind turbine grid-side converter are transformed into a three-phase given voltage E A 、E B 、E C signal, and the three-phase feedback U a , U b , U c The signal is subtracted and a three-phase current given signal is generated through a first-order low-pass function. The three-phase current given signal is transformed into a dq axis current given signal I dref ,I qref Signal, dq axis current given I dref ,I qref The signal is transmitted to the current control module; the virtual resistance parameter of the virtual admittance module is adjusted by the virtual resistance parameter adjustment module:
[0059] The virtual resistance parameter adjustment module uses the active power given signal P of the wind turbine grid-side converter ref Signal and active power feedback signal P fbk The difference of the signal is used to adjust the virtual resistance parameter R vir The size of the virtual resistance parameter R vir The signal is transmitted to the virtual admittance module;
[0060] The virtual resistance parameter selects upper resistance.
[0061] S3, the current control module is based on the current given by the dq axis of the previous virtual admittance module I dref ,I qref Signal, generate modulation signals vd, vq in the rotating coordinate system, and transmit them to the coordinate inverse transformation module;
[0062] S4, the coordinate inverse transformation module is used to generate the three-phase modulation signal V of the wind turbine grid-side converter ref_abc , and transmitted to the wind turbine grid-side converter.
[0063] An active circulating current suppression system for a grid-type wind turbine grid-side converter comprises an amplitude limit value adjustment module, an active voltage module, a voltage amplitude limit module, a reactive frequency module, a virtual admittance module, a current control module, a coordinate inverse transformation module, and a virtual resistance parameter adjustment module. The virtual resistance parameter adjustment module is connected to the virtual admittance module, the output end of the amplitude limit value adjustment module is connected to the voltage amplitude limit module, the output end of the active voltage module is connected to the voltage amplitude limit module, and the voltage amplitude limit module outputs an AC voltage given amplitude E peak signal, connected to the input terminal of the virtual admittance module;
[0064] The input end of the limit value adjustment module is connected to the active power feedback P of the wind turbine grid-side converter. fbk Signal connection;
[0065] The input terminal of the active voltage module is connected to the active power given by the wind turbine grid-side converter P ref Signal and active power feedback P fbk Signal connection;
[0066] The reactive power given by the reactive frequency module input terminal and the wind turbine grid-side converter is Q ref Signal and reactive power feedback Q fbk The reactive frequency module outputs the phase θ of the wind turbine grid-side converter, which is connected to the virtual admittance module and the coordinate inverse transformation module respectively.
[0067] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.
[0068] Example 1
[0069] A method for suppressing active circulating current of grid-side converter of grid-type wind turbine, see Figure 1 , including active voltage module, voltage limit module, limit value adjustment module, reactive frequency module, virtual admittance module, virtual resistance parameter adjustment module, current control module, coordinate inverse transformation module; specifically including:
[0070] S1, active voltage module
[0071] The input quantity of the active voltage module includes the active power given P ref and active power feedback P fbkThe difference between the two is passed through the PI controller to generate an AC voltage given signal U dref .
[0072] S2, voltage limiting module
[0073] To ensure that the converter meets the safe operation requirements of the wind farm, the voltage limit value in the voltage limit module is selected as 1.15pu, and the input of the voltage limit module is the AC voltage given signal U dref , after limiting, the output is the amplitude of the reference voltage.
[0074] S3, reactive frequency module
[0075] The input quantity of the reactive frequency module includes the reactive power given Q ref and reactive power feedback Q fbk The difference between the two is passed through a low-pass filter to generate a frequency difference Δω, which is equal to the rated frequency value ω of the grid voltage. 0 Add and integrator The input terminals are connected, and the integrator output θ is the phase of the inverter.
[0076] S4, limit adjustment module
[0077] The input of the limit regulation module is the active power feedback P fbk , the output is the compensation signal ΔU of the limit value dref ,See Figure 2 Specifically, the direction of the output active power of the wind turbine converter is used to determine whether to compensate for the voltage limit value. The size of the compensation value is determined by the absolute value of the active power. Specifically, when the active power output is positive, no compensation is performed, and when the active power is negative, compensation is performed. The compensation signal ΔU dref The size of -P fbk *k p_u , k p_u is the adjustment coefficient of the compensation signal.
[0078] S5, Virtual Admittance Module
[0079] The input of the virtual admittance module is the given amplitude of the AC voltage E peak , the phase θ of the converter and the three-phase feedback voltage U A , U B , U C , where the three-phase given voltage signal E is constructed by the given amplitude of the AC voltage and the phase of the converter A 、E B 、E C The difference between the three-phase given voltage signal and the three-phase feedback voltage is converted into a three-phase current given signal I through a first-order low-pass function. virA ,I virB ,IvirC The three-phase current is given by coordinate transformation to generate the current given signal I of the dq axis dref ,I qref ; Through a first-order low-pass function, the formula is as follows:
[0080]
[0081] In formula ①, the adjustable parameters are: virtual resistance R v , virtual reactance L v , parameter selection is biased towards resistive.
[0082] S6, virtual resistance parameter adjustment module
[0083] The input of the virtual resistance parameter adjustment module is the active power feedback P fbk , the output is the virtual resistance parameter R vir ,See Figure 3 , the deviation between active power feedback and rated power passes through the limiter, where k minlim To ensure that the virtual resistance parameter will not be negative, k maxmin To ensure that the system can output active power normally, the output of the limiter passes through the initial virtual resistance parameter R vir0 , generate real-time adjusted virtual resistance parameter R vir , virtual resistance parameter R vir Assign to R v .
[0084] S7, current control module
[0085] The input of the current control module is the current given signal I dref ,I qref and the current feedback signal I dfbk ,I qfbk ,(I dfbk ,I qfbk The output three-phase current is obtained through coordinate transformation), the current given signal (I dref ,I qref ) and the current feedback signal (I dfbk ,I qfbk ) passes through the PI controller, and the coupling component of the inductance ωL also needs to be considered F I dfbk and ωL F I qfbk The influence of dq axis finally generates the reference voltage value E dref 、E qref .
[0086] S8, coordinate inverse transformation module
[0087] Reference voltage value E under dq axisdref 、E qref Generate a three-phase reference voltage modulation signal V under the reverse coordinate change module refa 、V refb 、V refc ;
[0088] The coordinate change module refers to the transformation of the three-phase stationary coordinate system to the synchronous rotating coordinate system, and the coordinate inverse transformation module refers to the transformation of the synchronous rotating coordinate system to the three-phase stationary coordinate system. The specific expressions of the two are as follows: the coordinate change module is as shown in formula (1), and the coordinate inverse transformation module is as shown in formula (2);
[0089]
[0090]
[0091] Example 2
[0092] Both the amplitude limit module and the virtual resistance parameter adjustment module can suppress active circulating current, but the combination of the two has a better suppression effect. Figure 4 , a simulation model of the topology was built in PSCAD, which mainly includes two wind turbines, a sending-end converter station with an uncontrolled rectifier bridge and a receiving-end MMC converter station; a simulation verification was carried out using a three-phase short-circuit fault on the AC side of the receiving-end converter station as an example.
[0093] The simulation verification is divided into four cases, namely, without the amplitude limit value adjustment module and the virtual resistance parameter adjustment module, with only the amplitude limit value adjustment module, with only the virtual resistance parameter adjustment module, and with the amplitude limit value adjustment module and the virtual resistance parameter adjustment module.
[0094] A three-phase short circuit fault occurs in the AC side power grid of the receiving converter station. The simulation results of the four cases are shown in Figure 5-Figure 8 .
[0095] See Figure 5 ,Without the control of the amplitude limit adjustment module and the virtual resistance parameter adjustment module, active ,circulation current phenomenon occurred in the two wind turbines during the fault period.
[0096] See Figure 6 , only the limit value adjustment module has the phenomenon that the rectifier bridge is not controlled to transmit active power again during the fault period, which will cause the DC voltage of the receiving end converter station to increase;
[0097] See Figure 7 ,With only the virtual resistance parameter adjustment module, in the early stage of the fault, the two wind turbines will still have active circulation phenomenon;
[0098] See Figure 8 It is equipped with a limit value adjustment module and a virtual resistance parameter adjustment module. No active circulating current phenomenon occurs at the initial stage of the fault and during the fault period.
[0099] In the hybrid DC transmission system composed of an uncontrolled rectifier converter station and a modular multi-point flat converter station, the present invention replaces the voltage outer loop with a virtual admittance loop, compared with the conventional power loop + voltage outer loop + current inner loop control method, which can simulate the impedance characteristics of the converter. By adjusting the parameters of the virtual admittance to adjust the port characteristics of the converter, it is beneficial to the stability of the wind turbine grid-side converter; the voltage limit value module can suppress the active circulating current by adjusting the voltage amplitude of the wind turbine grid-side converter during the period when active circulating current appears in the wind turbine set; the active limiting module is combined with the virtual resistance parameter adjustment module, which can achieve excellent active circulating current suppression effect both in transient and steady states during the period when a fault occurs in the onshore circulating station.
Claims
1. A method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine, characterized in that: include: S1, the power outer loop module gives P according to the active power of the grid-side converter of the grid-type wind turbine ref Signal, reactive power given Q ref Signal generation AC voltage given amplitude E peak The signal and phase θ are transmitted to the virtual admittance module, and the AC voltage is given an amplitude E peak The amplitude is adjusted according to the active power of the wind turbine grid-side converter; S2, the virtual admittance module is given an amplitude E according to the AC voltage generated by the previous power outer loop module peak signal and phase θ, generating the current given I of the dq axis dref ,I qref The signal is transmitted to the current control module, and the virtual resistance parameters are adjusted according to the active power; S3, the current control module is based on the current given by the dq axis of the previous virtual admittance module I dref ,I qref Signal, generate modulation signals vd, vq in the rotating coordinate system, and transmit them to the coordinate inverse transformation module; S4, the coordinate inverse transformation module is used to generate the three-phase modulation signal V of the wind turbine grid-side converter ref_abc , and transmitted to the wind turbine grid-side converter.
2. The method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine according to claim 1, characterized in that: In S1, the power outer loop module includes a limit value adjustment module, an active voltage module, a voltage limit module, and a reactive frequency module, and the contents are as follows: S11, active voltage module includes PI controller, the active power of wind turbine grid-side converter is given by P ref Signal and active power feedback P fbk The signal is subtracted and the PI controller generates the d-axis voltage set value E. dref The signal is transmitted to the voltage limiting module; S12, voltage limit module includes limiter, d-axis voltage given value E dref The signal passes through the limiter to generate an AC voltage with a given amplitude E. peak The signal is transmitted to the virtual admittance module; S13, reactive frequency module includes low-pass filter and integration module, the reactive power of wind turbine grid-side converter is given by Q ref Signal and reactive power feedback Q fbk Make a difference, and generate the angular frequency ω of the wind turbine grid-side converter through a low-pass filter. The angular frequency ω of the wind turbine grid-side converter is added to the rated angular frequency ω0 and then passed through the integration module to generate the phase θ of the wind turbine grid-side converter. The phase θ of the wind turbine grid-side converter is transmitted to the virtual admittance module and the coordinate inverse transformation module respectively. S14, the amplitude limit value adjustment module includes an amplitude limit adjustment circuit for setting the d-axis voltage given value E in the voltage amplitude limit module. dref Amplitude provides compensation ΔU dref value.
3. The method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine according to claim 1, characterized in that: In S2, the input signal of the virtual admittance module is the given amplitude E of the AC voltage. peak The signal and the phase θ of the wind turbine grid-side converter are transformed into a three-phase given voltage E A 、E B 、E C signal, and the three-phase feedback U a , U b , U c The signal is subtracted and a three-phase current given signal is generated through a first-order low-pass function. The three-phase current given signal is transformed into a dq axis current given signal I dref ,I qref Signal, dq axis current given I dref ,I qref The signal is sent to the current control module.
4. The method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine according to claim 3 is characterized in that: The virtual resistance parameter of the virtual admittance module is adjusted by the virtual resistance parameter adjustment module: The virtual resistance parameter adjustment module uses the active power given signal P of the wind turbine grid-side converter ref signal and active power feedback signal P fbk The difference of the signal is used to adjust the virtual resistance parameter R vir The size of the virtual resistance parameter R vir The signal is transmitted to the virtual admittance module; The virtual resistance parameter selects upper resistance.
5. The method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine according to claim 2, characterized in that: In S14, the direction of the active power of the wind turbine grid-side converter is used to determine whether the d-axis voltage given value E in the voltage limiting module is set. dref Amplitude provides compensation ΔU dref value: The positive direction of the active power output by the wind turbine grid-side converter is based on the current output; When the active power direction of the wind turbine grid-side converter is in the positive direction, no compensation is performed; When the active power of the wind turbine grid-side converter is in the negative direction, compensation is performed; Among them, compensation ΔU dref The value is the absolute value of the active power of the wind turbine grid-side converter.
6. A method for suppressing active circulating current of a grid-side converter of a grid-type wind turbine according to claim 5, characterized in that: According to the active power feedback P of the wind turbine grid-side converter fbk To adjust the limit value in the voltage limit module, when the active power feedback P fbk When the direction is negative, by compensating ΔU dref The output voltage of the converter is raised by adjusting the current value to avoid the backflow of active power of the wind turbine grid-side converter.
7. An active circulating current suppression system for a grid-type wind turbine grid-side converter for implementing the method according to claims 1-6, characterized in that: It includes a power outer loop module, a virtual admittance module, a current control module, and a coordinate inverse transformation module. The output end of the power outer loop module is connected to the virtual admittance module and the coordinate inverse transformation module respectively, the output end of the virtual admittance module is connected to the input end of the current control module, the output end of the current control module is connected to the input end of the coordinate inverse transformation module, and the output signal of the coordinate inverse transformation module is sent to the wind turbine grid-side converter.
8. The active circulating current suppression system of the grid-side converter of a grid-type wind turbine according to claim 7 is characterized in that: The power outer ring module includes a limit value adjustment module, an active voltage module, a voltage limit module, and a reactive frequency module. The output end of the limit value adjustment module is connected to the voltage limit module, the output end of the active voltage module is connected to the voltage limit module, and the voltage limit module outputs an AC voltage with a given amplitude E. peak signal, connected to the input terminal of the virtual admittance module; The input end of the limit value adjustment module is connected to the active power feedback P of the wind turbine grid-side converter. fbk Signal connection; The input terminal of the active voltage module is connected to the active power given by the wind turbine grid-side converter P ref Signal and active power feedback P fbk Signal connection; The reactive power given by the reactive frequency module input terminal and the wind turbine grid-side converter is Q ref Signal and reactive power feedback Q fbk The reactive frequency module outputs the phase θ of the wind turbine grid-side converter, which is connected to the virtual admittance module and the coordinate inverse transformation module respectively.
9. The active circulating current suppression system of the grid-side converter of a grid-type wind turbine according to claim 1 is characterized in that: It also includes a virtual resistance parameter adjustment module, which is connected to the virtual admittance module.