A permanent magnet direct drive wind turbine converter starting control method

Abstract

The application discloses a permanent magnet direct drive wind turbine converter starting control method, which comprises the following steps: detecting wind speed and wind direction; determining the starting condition of the machine side converter by detecting the generator speed and the direct current voltage through a speed measuring instrument and a direct current voltage detection unit respectively; starting the machine side converter, and the machine side converter executes an algorithm MA; starting the grid side converter, and when the direct current bus voltage is equal to the set value Udc_Ref, starting the grid side converter, and the grid side converter executes a control algorithm GA; switching the control strategy of the grid side converter, detecting the output voltage and the grid voltage of the grid side converter, closing the grid side circuit breaker QF2 when the amplitude and phase of the output voltage and the grid voltage of the grid side converter are consistent, and the grid side converter executes an algorithm GB; and the application can effectively realize the starting control of the permanent magnet direct drive wind turbine converter without a pre-charging circuit, effectively suppresses the grid-connected current, and effectively improves the efficiency and cost of the system.

Description

Technical Field

[0001] This invention relates to the field of wind turbine converter start-up control technology, and in particular to a method for start-up control of a permanent magnet direct-drive wind turbine converter. Background Technology

[0002] With the development of wind power generation technology, gearless direct-drive wind turbines using low-speed permanent magnet synchronous generators have gradually become the mainstream model in wind power generation systems due to their advantages such as simple structure, compact size, and convenient maintenance.

[0003] As is well known, the key equipment in a direct-drive wind turbine is the full-power wind power converter, which consists of a grid-side converter and a machine-side converter. The grid-side and machine-side converters are decoupled through a large-capacity capacitor. Wind power converters typically require a pre-charge circuit to charge the DC-side capacitor. The startup process involves first activating the pre-charge circuit to charge the DC bus capacitor. Once the capacitor voltage reaches a set value, the pre-charge circuit is closed. Then, the AC switch of the grid-side converter is closed, starting the grid-side converter to control the DC bus voltage to the set value. Finally, the AC switch of the machine-side converter is closed, starting the machine-side converter to control the wind turbine speed and achieve maximum wind speed tracking. The presence of the pre-charge circuit increases the complexity of the wind power converter's electrical system and control, while also increasing system cost and reducing system reliability.

[0004] Therefore, in view of the shortcomings of the existing technology, there is an urgent need in the field to propose a control method for a permanent magnet direct drive wind turbine converter that does not employ a pre-charging circuit. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract and title of the invention. Such simplifications or omissions shall not be used to limit the scope of the present invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the technical problem to be solved by this invention is that traditional permanent magnet direct-drive wind power converters require an additional pre-charging circuit and have large grid connection inrush currents.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a starting control method for a permanent magnet direct-drive wind turbine converter, comprising,

[0009] Wind speed and direction are detected using an anemometer;

[0010] The generator speed and DC voltage are detected by a speed measuring instrument and a DC voltage detection unit, respectively, to determine the starting conditions of the generator-side converter.

[0011] Start the machine-side converter, and the machine-side converter executes algorithm MA;

[0012] Start the grid-side converter. When the DC bus voltage equals the set value Udc_Ref, start the grid-side converter and execute the control algorithm GA.

[0013] The grid-side converter switching control strategy detects the output voltage of the grid-side converter and the grid voltage. When the amplitude and phase of the output voltage of the grid-side converter are consistent with those of the grid voltage, the grid-side circuit breaker QF2 is closed, and the grid-side converter executes algorithm GB.

[0014] The machine-side converter switching control strategy and the machine-side converter execution control algorithm MB.

[0015] As a preferred embodiment of the permanent magnet direct-drive wind turbine converter start-up control method of the present invention, wherein: the step of detecting wind speed and wind direction by an anemometer includes:

[0016] Sampling wind speed v w The average wind speed vw is obtained using a moving average filtering method, and the wind speed exceeds the cut-in wind speed V of the wind turbine. cut_in Close the circuit breaker on the machine side;

[0017] The pitch control device is activated to gradually reduce the pitch angle.

[0018] As a preferred embodiment of the permanent magnet direct-drive wind turbine converter start-up control method of the present invention, wherein: the determination of the start-up conditions of the turbine-side converter includes:

[0019] The generator speed ωm is detected in real time by a speed measuring instrument, and the DC bus voltage u is detected in real time by a voltage sensor. dc ;

[0020] Determine the threshold U for pre-charging the DC bus capacitor during startup. dc_pre ;

[0021] Determine the generator speed threshold ω during startup. m_pre ;

[0022] Determine the startup conditions for the converter to enter the pre-grid-connected operation mode.

[0023] As a preferred embodiment of the permanent magnet direct-drive wind turbine converter start-up control method of the present invention, wherein the generator-side converter execution algorithm MA includes:

[0024] When the generator speed exceeds ω m_pre Or the DC bus voltage exceeds Udc_pre Start the machine-side converter and enable the machine-side converter to execute algorithm MA;

[0025] Determine the control objectives for the machine-side converter;

[0026] Determine the limiting value i of the DC voltage PI regulator (PI-UDC) mq_lim1 .

[0027] As a preferred embodiment of the permanent magnet direct-drive wind turbine converter start-up control method of the present invention, wherein:

[0028] Will U dc_ref with U dc The error is controlled by a DC voltage PI regulator (PI-UDC) to obtain the q-axis current reference value i of the machine-side converter. mq_ref The reference value of the d-axis current i md_ref Set to 0;

[0029] The current feedback value i is obtained by performing coordinate transformation on the three-phase current of the machine-side converter. md and i mq .

[0030] As a preferred embodiment of the permanent magnet direct-drive wind turbine converter start-up control method of the present invention, wherein:

[0031] Determine the integral and output limit value v of the D-axis current PI regulator (PI-IMD) of the machine-side converter. md_lim The integral and output limiting value v of the Q-axis current PI regulator (PI-IMQ) of the machine-side converter. mq_lim ;

[0032] will i md_ref with i md The error is controlled by the PI regulator (PI-IMD) of the D-axis current of the machine-side converter to obtain the d-axis voltage output value v of the machine-side converter. md , change i mq_ref with i mq The error is controlled by the Q-axis current PI regulator (PI-IMQ) of the machine-side converter to obtain the q-axis voltage output value v of the machine-side converter. mq ;

[0033] The d-axis voltage output value v of the machine-side converter md and q-axis voltage output value v mq After coordinate transformation, the modulated wave v is obtained. ma v mb and v mc ;

[0034] The modulation wave v of the grid-side converter ma v mb and vmc The space vector pulse generation unit of the grid-side converter generates the driving pulses of the grid-side converter to control its operation.

[0035] As a preferred embodiment of the permanent magnet direct drive wind turbine converter start-up control method of the present invention, wherein: the grid-side converter is enabled to execute the algorithm GA, and the amplitude Um and phase θ of the AC voltage at the PCC point are detected by the phase-locked loop to determine the control target of the grid-side converter;

[0036] The voltage feedback value u is obtained by performing coordinate transformation on the output voltage of the grid-side converter. gd and u gq ;

[0037] will u gd_ref with u gd The error is controlled by the D-axis voltage PI regulator (PI-UGD) to obtain the d-axis current reference value i of the grid-side converter. gd_ref , will u gq_ref with u gq The error is controlled by the Q-axis voltage PI regulator (PI-UGQ) to obtain the q-axis current reference value i of the grid-side converter. gq_ref ;

[0038] Determine the limiting value i of the D-axis voltage PI regulator (PI-UGD). gd_lim The limiting value i of the Q-axis voltage PI regulator (PI-UGQ) gq_lim .

[0039] As a preferred embodiment of the permanent magnet direct-drive wind turbine converter start-up control method of the present invention, wherein:

[0040] The current feedback value i is obtained by performing coordinate transformation on the output current of the grid-side converter. gd and i gq ;

[0041] Determine the integral and output limit value v of the D-axis current PI regulator (PI-IGD) of the grid-side converter. gd_lim The integral and output limiting value v of the Q-axis current PI regulator (PI-IGQ) of the grid-side converter. gq_lim ;

[0042] will i gd_ref with i gd The error is controlled by a D-axis current PI regulator (PI-IGD) to obtain the d-axis voltage output value v of the grid-side converter. gd , change i gq_ref with i gq The error is controlled by a Q-axis current PI regulator (PI-IGQ) to obtain the q-axis voltage output value v of the grid-side converter. gq ;

[0043] The d-axis voltage output value v of the grid-side converter gd and q-axis voltage output value v gq After coordinate transformation, the modulated wave v is obtained. ga v gb and v gc ;

[0044] The modulation wave v of the grid-side converter ga v gb and v gc The space vector pulse generation unit of the grid-side converter generates the driving pulses of the grid-side converter to control its operation.

[0045] As a preferred embodiment of the permanent magnet direct drive wind turbine converter start-up control method of the present invention, wherein: when the output voltage and phase of the grid-side converter meet the set conditions with the error of the PCC point, the grid-side circuit breaker is closed.

[0046] Enable the grid-side converter to execute algorithm GB and determine the control objective of the grid-side converter;

[0047] Calculate the output reactive power q of the grid-side converter. g ;

[0048] will u dc_ref with u dc The error is controlled by a DC voltage PI regulator (PI-UDC) to obtain the d-axis current reference value i of the grid-side converter. gd_ref ; q g_re f and q g The error is controlled by a reactive power PI regulator (PI-QWT) to obtain the q-axis current reference value i of the grid-side converter. gq_ref ;

[0049] Determine the limiting value i of the D-axis voltage PI regulator (PI-UGD). gd_lim The limiting value i of the Q-axis voltage PI regulator (PI-UGQ) gq_lim ;

[0050] Repeatedly obtain the current feedback value i gd and i gq Step to the modulation wave v of the grid-side converter ga v gb and v gc Change the work steps.

[0051] As a preferred embodiment of the permanent magnet direct drive wind turbine converter start-up control method of the present invention, wherein: the machine-side grid converter control algorithm MB is enabled to determine the control target of the machine-side converter;

[0052] Determine the output power p of the machine-side converter m ;

[0053] p m_ref With p m The error is controlled by a power PI regulator (PI-WPT) to obtain the q-axis current reference value i of the machine-side converter. mq_ref ; d-axis current reference value i md_ref Set to 0;

[0054] Determine the limiting value i of the power PI regulator (PI-PWT) mq_lim ;

[0055] Repeatedly obtain the current feedback value i md and i mq Step to the modulation wave v of the grid-side converter ma v mb and v mc Change the work steps.

[0056] The beneficial effects of this invention are as follows: This invention can effectively control the start-up of permanent magnet direct-drive wind turbine converters without the need for a pre-charging circuit. It not only effectively suppresses grid-connected current but also effectively improves system efficiency and cost. Attached Figure Description

[0057] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0058] Figure 1 This is a block diagram of the main circuit and control structure of a permanent magnet direct-drive wind turbine converter according to the present invention;

[0059] Figure 2 This is a control block diagram of the machine-side converter before the start-up and grid connection of the permanent magnet direct-drive wind turbine converter of the present invention;

[0060] Figure 3 This is a control block diagram of the grid-side converter before the start-up and grid connection of the permanent magnet direct-drive wind turbine converter of the present invention;

[0061] Figure 4 This is a control block diagram of the machine-side converter after the permanent magnet direct drive wind turbine converter of this invention is started and connected to the grid;

[0062] Figure 5 This is a control block diagram of the grid-side converter after the permanent magnet direct-drive wind turbine converter of the present invention is started and connected to the grid;

[0063] Figure 6This is a block diagram of the switching logic control for grid-connected control of the permanent magnet direct-drive wind turbine converter of the present invention. Detailed Implementation

[0064] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0065] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0066] Secondly, the present invention will be described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure will be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0067] Furthermore, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0068] Example 1

[0069] Reference Figures 1-6 This embodiment provides a starting control method for a permanent magnet direct-drive wind turbine converter. The method of this invention includes six steps, including:

[0070] 1. Start-up of the wind turbine and closing of the turbine-side converter;

[0071] 2. Determine the startup conditions for the machine-side converter;

[0072] 3. The machine-side converter starts to slowly charge the DC capacitor;

[0073] 4. The voltage amplitude and phase of the grid-connected port are controlled during the start-up of the grid-side converter;

[0074] 5. Switching of grid-side converter closing and grid connection control strategies;

[0075] 6. Switching of machine-side converter control strategy.

[0076] Specifically:

[0077] When the wind speed exceeds the wind turbine's cut-in wind speed V cut_inClose the circuit breaker on the machine side, start the pitch control device to gradually reduce the pitch angle so that the wind turbine captures wind energy and rotates;

[0078] Detect the DC bus voltage and generator speed. When the DC bus capacitor voltage Udc is greater than or equal to the set value Udc_pre or the generator speed is greater than or equal to the set value ω... m_tpre The starter-side converter executes algorithm MA, which is a DC voltage outer loop plus a current inner loop structure. Its control objective is to control the DC voltage to equal the set value U. dc_Ref ;

[0079] After time ta, when the DC bus voltage equals the set value U dc_Ref The grid-side converter is controlled to execute the algorithm GA. The algorithm GA is an AC voltage outer loop plus a current inner loop structure. Its control objective is to make the output voltage of the grid-side converter consistent with the amplitude and phase of the grid voltage.

[0080] The grid-side converter's output voltage and the grid voltage are monitored. When the output voltage of the grid-side converter matches the grid voltage in both amplitude and phase, the grid-side circuit breaker is closed. Simultaneously, the grid-side converter switches from executing algorithm GA to executing algorithm GB. Algorithm GB is a structure with an outer loop for DC voltage and an inner loop for current. Its control objective is to control the DC voltage to equal the set value U. dc_Ref ;

[0081] The generator-side converter is switched from executing algorithm MA to executing algorithm MB. Algorithm MB is a power outer loop plus current inner loop structure, and its goal is to control the generator output power to be equal to the set value.

[0082] S1: Wind speed is detected by an anemometer. When the wind speed exceeds the wind turbine's starting speed, the pitch controller controls the pitch angle of the wind turbine blades through the pitch device to capture wind energy. After the permanent magnet generator rotates, the machine-side circuit breaker is closed. Specifically, this includes:

[0083] S1.1: Sampling wind speed v w The average wind speed v is obtained using the moving average filtering method. w The filter expression used is:

[0084]

[0085] S1.2: Wind speed exceeds the wind turbine's cut-in wind speed V cut_in Close the circuit breaker on the machine side;

[0086] S1.3: Activate the pitch control device to gradually decrease the pitch angle, allowing the wind turbine to capture wind energy and rotate. The formula for setting the pitch angle is:

[0087]

[0088] In the formula, k β The rate at which the pitch angle decreases;

[0089] S2: Determine the startup conditions of the generator-side converter by detecting the generator speed and DC voltage using a generator speed measuring instrument and a DC voltage detection unit, respectively; specifically including:

[0090] S2.1: Real-time detection of generator speed ω using a generator speed measuring instrument. m The DC bus voltage value u is detected in real time by the DC voltage detection unit. dc ;

[0091] S2.2: Determine the threshold U for pre-charging the DC bus capacitor during startup. dc_pre Its value is calculated according to the following formula.

[0092] Among them, U gn is the effective value of the grid line voltage; k is the DC voltage coefficient, taken as 0.8 to 0.9.

[0093] Step 2.3: Determine the generator speed threshold ω during startup. m_pre Its value is calculated according to the following formula.

[0094]

[0095] Where, m tb The total mass of the wind turbine-generator drivetrain system is r; the length of the wind turbine blade is r; C dc This is the DC bus capacitance value.

[0096] S2.4: Determine the startup conditions for the converter to enter the pre-grid-connected operation mode. Either one of the two conditions needs to be met. The specific conditions are as follows:

[0097]

[0098] S3: Start the machine-side converter. The machine-side converter executes algorithm MA, which adopts a DC voltage outer loop plus a current inner loop structure, controlling the current voltage to equal the set value U. dc_Ref Specifically, this includes:

[0099] S3.1: When the generator speed exceeds ω m_pre Or the DC bus voltage exceeds U dc_pre Start the machine-side converter and enable the machine-side converter to execute algorithm MA;

[0100] S3.2: Determine the control objective of the machine-side converter as follows:

[0101]

[0102] Where, np ψ is the number of pole pairs of a permanent magnet synchronous generator; f The rated flux linkage of a permanent magnet synchronous generator; U n_g U is the rated value of the mains voltage; n_m k is the rated value of the generator stator voltage. b This is the voltage proportionality coefficient, ranging from 1.07 to 1.23.

[0103] S3.3: Determine the limiting value i of the DC voltage PI regulator (PI-UDC) mq_lim1 Its value is calculated according to the following formula.

[0104]

[0105] Among them, t pre Set the pre-charge time for the DC bus.

[0106] S3.4: Put u dc_ref with u dc The error is controlled by a DC voltage PI regulator (PI-UDC) to obtain the q-axis current reference value i of the machine-side converter. mq_ref The reference value of the d-axis current i md_ref Set to 0, that is

[0107]

[0108] S3.5: Perform coordinate transformation on the three-phase current of the machine-side converter to obtain the current feedback values ​​imd and imq;

[0109] S3.6: Determine the integral and output limiting values ​​vmd_lim of the D-axis current PI regulator (PI-IMD) and vmq_lim of the Q-axis current PI regulator (PI-IMQ) of the machine-side converter, respectively, according to the following formula.

[0110]

[0111] S3.7: The error between imd_ref and imd is controlled by the D-axis current PI regulator (PI-IMD) of the machine-side converter to obtain the d-axis voltage output value vmd of the machine-side converter; the error between imq_ref and imq is controlled by the Q-axis current PI regulator (PI-IMQ) of the machine-side converter to obtain the q-axis voltage output value vmq of the machine-side converter.

[0112] S3.8: Convert the d-axis voltage output value v of the machine-side converter md and q-axis voltage output value v mq After coordinate transformation, the modulated wave v is obtained. ma v mb and v mc ;

[0113] S3.9: Modulate the waveform v of the grid-side converter ma v mb and v mc The space vector pulse generation unit of the grid-side converter generates the driving pulses of the grid-side converter to control its operation.

[0114] S4: Start the grid-side converter when the DC bus voltage equals the set value U. dc_Re f. Start the grid-side converter. The grid-side converter executes the control algorithm GA, which adopts an AC voltage outer loop plus a current inner loop structure to ensure that the output voltage of the grid-side converter is consistent with the amplitude and phase of the grid voltage; specifically including:

[0115] S4.1: Enable the grid-side converter to execute algorithm GA, and detect the amplitude U of the AC voltage at point PCC through a phase-locked loop. m And phase θ, determine the control objective of the grid-side converter as

[0116]

[0117] S4.2: Perform coordinate transformation on the output voltage of the grid-side converter to obtain the voltage feedback value u. gd and u gq ;

[0118] S4.3: Put u gd_ref with u gd The error is controlled by the D-axis voltage PI regulator (PI-UGD) to obtain the d-axis current reference value i of the grid-side converter. gd_ref , will u gq_ref with u gq The error is controlled by the Q-axis voltage PI regulator (PI-UGQ) to obtain the q-axis current reference value i of the grid-side converter. gq_ref ;

[0119] S4.4: Determine the limit value i of the D-axis voltage PI regulator (PI-UGD) gd_lim The limiting value i of the Q-axis voltage PI regulator (PI-UGQ) gq_lim Its value is calculated according to the following formula.

[0120]

[0121] Among them, P wt This refers to the rated active power of the generator unit.

[0122] S4.5: Perform coordinate transformation on the output current of the grid-side converter to obtain the current feedback value i. gd and i gq ;

[0123] S4.6: Determine the integral and output limit value v of the D-axis current PI regulator (PI-IGD) of the grid-side converter. gd_lim The integral and output limiting value v of the Q-axis current PI regulator (PI-IGQ) of the grid-side converter. gq_lim Its value is calculated according to the following formula.

[0124]

[0125] S4.7: i gd_ref with i gd The error is controlled by a D-axis current PI regulator (PI-IGD) to obtain the d-axis voltage output value v of the grid-side converter. gd , change i gq_ref with i gq The error is controlled by a Q-axis current PI regulator (PI-IGQ) to obtain the q-axis voltage output value v of the grid-side converter. gq ;

[0126] S4.8: Convert the d-axis voltage output value v of the grid-side converter gd and q-axis voltage output value v gq After coordinate transformation, the modulated wave v is obtained. ga v gb and v gc ;

[0127] S4.9: Modulate the waveform v of the grid-side converter. ga v gb and v gc The space vector pulse generation unit of the grid-side converter generates the driving pulses of the grid-side converter to control its operation.

[0128] S5: Grid-side converter switching control strategy. It detects the output voltage of the grid-side converter and the grid voltage. When the amplitude and phase of the grid-side converter's output voltage match the grid voltage, it closes the grid-side circuit breaker QF2, and the grid-side converter executes algorithm GB. Algorithm GB is a structure with an outer DC voltage loop and an inner current loop. Its control objective is to control the DC voltage to equal the set value U. dc_Re f; specifically includes:

[0129] S5.1: When the output voltage and phase of the grid-side converter meet the set error conditions with respect to the PCC point, the grid-side circuit breaker is closed. The set error conditions are:

[0130]

[0131] Where λ is 0.02 and Δθ is 0.1.

[0132] S5.2: Enable the grid-side converter to execute algorithm GB, and determine the control objective of the grid-side converter as follows:

[0133]

[0134] Wherein, qg_wt is the reactive power command output by the wind turbine.

[0135] S5.3: Calculate the output reactive power q of the grid-side converter. g The corresponding calculation formula is:

[0136] q g =1.5(u gq i gd -u gd i gq )

[0137] S5.4: Will u dc_ref with u dc The error is controlled by a DC voltage PI regulator (PI-UDC) to obtain the d-axis current reference value i of the grid-side converter. gd_ref ; q g_ref With q g The error is controlled by a reactive power PI regulator (PI-QWT) to obtain the q-axis current reference value i of the grid-side converter. gq_ref ;

[0138] S5.5: Determine the limit value i of the D-axis voltage PI regulator (PI-UGD). gd_lim The limiting value i of the Q-axis voltage PI regulator (PI-UGQ) gq_lim Its value is calculated according to the following formula.

[0139]

[0140] S5.6: Execute S4.5 to S4.9;

[0141] S6: Generator-side converter switching control strategy; the generator-side converter executes control algorithm MB; algorithm MB is a power outer loop plus a current inner loop structure, and its goal is to control the generator output power to equal the set value. Specifically, it includes:

[0142] S6.1: Enable the machine-side grid converter control algorithm MB, and determine the control objective of the machine-side converter as follows:

[0143] p m_ref =p m_mppt

[0144] Among them, P m_mppt This represents the maximum capture power that the wind turbine is expected to output.

[0145] S6.2: Determine the output power p of the machine-side converter m The corresponding calculation formula is:

[0146] p m =1.5(u md i md +u mq i mq )

[0147] S6.3: P m_ref With p m The error is controlled by a power PI regulator (PI-WPT) to obtain the q-axis current reference value i of the machine-side converter. mq_ref ; d-axis current reference value i md_ref Set to 0;

[0148] S6.4: Determine the limiting value i of the power PI regulator (PI-PWT) mq_lim Its value is calculated according to the following formula.

[0149]

[0150] Among them, U mn This is the rated voltage of the permanent magnet synchronous generator.

[0151] S6.5: Execute S3.5 to S3.9.

[0152] like Figure 1As shown, the system structure of the permanent magnet direct-drive wind turbine includes a wind turbine 101, a wind speed detector 102, a pitch driver 103, a pitch controller 104, a permanent magnet generator 105, a motor speed detector 106, a machine-side circuit breaker 107, a machine-side reactor 108, a machine-side three-phase fully controlled bridge 109, a machine-side current detection unit 110, a DC filter capacitor 111, a DC voltage detection unit 112, a grid-side three-phase fully controlled bridge 113, an LCL filter 114, a converter output voltage detection unit 115, a grid-side current detection unit 116, a grid-side circuit breaker 117, a grid power supply 118, a grid voltage detection unit 119, a wind power converter controller 120, a machine-side PWM generator 121, and a grid-side PWM generator 122. The wind turbine 101 directly drives the permanent magnet generator 105. The output terminal of the permanent magnet generator 105 is connected to the input terminal of the turbine-side circuit breaker 107. The output terminal of the turbine-side circuit breaker 107 is connected to the input terminal of the turbine-side reactor 108. The output terminal of the turbine-side reactor 108 is connected to the AC terminal of the turbine-side three-phase fully controlled bridge 109. The DC terminal of the turbine-side three-phase fully controlled bridge 109 is connected to the DC filter capacitor 111. The DC filter capacitor 111 is connected to the DC terminal of the grid-side three-phase fully controlled bridge 113. The AC terminal of the grid-side three-phase fully controlled bridge 113 is connected to the input terminal of the grid-side LCL filter 114. The output terminal of the grid-side LCL filter 114 is connected to the input terminal of the grid-side circuit breaker 117. The output terminal of the grid-side circuit breaker 117 is connected to the grid power supply 118. The output terminals of the wind speed detector 102 and the motor speed detector 106 are connected to the pitch controller 104. The output terminal of 104 is connected to the pitch driver 103, which controls the pitch angle of the wind turbine 101. The output terminals of the motor speed detector 106, the machine-side current detection unit 110, the DC voltage detection unit 112, the converter output voltage detection unit 115, the grid-side current detection unit 116, and the grid voltage detection unit 119 are connected to the input terminal of the wind power converter controller 120. The output terminals of the wind power converter controller 120 and the DC voltage detection unit 112 are respectively connected to the input terminals of the machine-side PWM generator 121 and the grid-side PWM generator 122. The output of the machine-side PWM generator 121 is connected to the pulse input terminal of the machine-side three-phase fully controlled bridge 109, and the output of the grid-side PWM generator 122 is connected to the pulse input terminal of the grid-side three-phase fully controlled bridge 116.

[0153] like Figure 1 As shown, before the DC voltage of the permanent magnet direct-drive wind turbine converter is pre-charged and connected to the grid, the system is in operating mode A, with switches S1 and S2 in position 2 and switch S3 in position 1. At this time, the control strategy of the turbine-side converter is as follows: Figure 2 As shown, the grid-side converter control strategy is as follows: Figure 3As shown; after the permanent magnet direct-drive wind turbine converter meets the grid connection conditions, the system is in operating mode B, with switches S1 and S2 in position 1 and switch S3 in position 2. At this time, the control strategy of the machine-side converter is as follows: Figure 4 As shown, the grid-side converter control strategy is as follows: Figure 5 As shown;

[0154] like Figure 2 As shown, before grid connection of the permanent magnet direct-drive wind turbine converter, the machine-side converter is described as follows: The difference between the DC capacitor voltage setpoint and the actual DC capacitor voltage is input to the PI-DUC controller, and after limiting, the machine-side q-axis current setpoint is obtained; the difference between the machine-side q-axis current setpoint and the machine-side q-axis current feedback value is input to the PI-IMQ controller, and after limiting, the machine-side converter q-axis voltage output value is obtained; the difference between the machine-side d-axis current setpoint and the machine-side d-axis current feedback value is input to the PI-IMD controller, and after limiting, the machine-side converter d-axis voltage output value is obtained; the machine-side converter d-axis voltage and q-axis voltage are transformed by coordinate transformation and machine-side space vector modulation to obtain the PWM drive signal of the machine-side converter;

[0155] like Figure 3 As shown, before the permanent magnet direct-drive wind turbine converter is connected to the grid, the grid-side converter is described as follows: The difference between the d-axis setpoint of the grid-connected converter AC voltage and the d-axis value of the grid-connected converter AC voltage is input to the PI-UGD controller, and after limiting processing, the grid-side d-axis current setpoint is obtained; The difference between the q-axis setpoint of the grid-connected converter AC voltage and the q-axis value of the grid-connected converter AC voltage is input to the PI-UGQ controller, and after limiting processing, the grid-side q-axis current setpoint is obtained; The difference between the grid-side d-axis current setpoint and the grid-side d-axis current feedback value is input to the PI-IGD controller, and after limiting processing, the grid-side converter d-axis voltage output value is obtained; The difference between the grid-side q-axis current setpoint and the grid-side q-axis current feedback value is input to the PI-IGQ controller, and after limiting processing, the grid-side converter q-axis voltage output value is obtained; The d-axis voltage and q-axis voltage of the grid-side converter are transformed by coordinate transformation and the grid-side space vector modulation stage to obtain the PWM drive signal of the grid-side converter.

[0156] like Figure 4 As shown, after the permanent magnet direct-drive wind turbine converter is connected to the grid, the generator-side converter is described as follows: The difference between the generator power output setpoint and the actual generator power output is input to the PI-PWT controller, and after limiting, the generator-side q-axis current setpoint is obtained; the difference between the generator-side q-axis current setpoint and the generator-side q-axis current feedback value is input to the PI-IMQ controller, and after limiting, the generator-side converter q-axis voltage output value is obtained; the difference between the generator-side d-axis current setpoint and the generator-side d-axis current feedback value is input to the PI-IMD controller, and after limiting, the generator-side converter d-axis voltage output value is obtained; the generator-side converter d-axis voltage and q-axis voltage are transformed by coordinate transformation and generator-side space vector modulation to obtain the generator-side converter PWM drive signal;

[0157] like Figure 5 As shown, after the permanent magnet direct-drive wind turbine converter is connected to the grid, the grid-side converter is described as follows: The difference between the DC capacitor voltage setpoint and the actual DC capacitor voltage is input to the PI-UDC controller, and after limiting, the grid-side d-axis current setpoint is obtained; the difference between the grid-side converter reactive power setpoint and the actual reactive power is input to the PI-QWT controller, and after limiting, the grid-side q-axis current setpoint is obtained; the difference between the grid-side d-axis current setpoint and the grid-side d-axis current feedback value is input to the PI-IGD controller, and after limiting, the grid-side converter d-axis voltage output value is obtained; the difference between the grid-side q-axis current setpoint and the grid-side q-axis current feedback value is input to the PI-IGQ controller, and after limiting, the grid-side converter q-axis voltage output value is obtained; the grid-side converter d-axis voltage and q-axis voltage are transformed by coordinate transformation and the grid-side space vector modulation stage to obtain the PWM drive signal of the grid-side converter.

[0158] like Figure 6 As shown, the switching logic of the grid-connected control of the wind power converter is described as follows: When the absolute value of the difference between the output voltage amplitude of the grid-side converter and the grid voltage amplitude is less than a set proportion of the voltage amplitude, the comparator CMPA outputs a high level; when the absolute value of the difference between the phase of the output voltage of the grid-side converter and the phase of the grid voltage is less than a set angle value, the comparator CMPB outputs a high level; after performing an AND operation on the outputs of comparators CMPA and CMPB, the control strategy switching switch S3 is used; after performing an AND-NOT operation on the outputs of comparators CMPA and CMPB, the control strategy switching switches S1 and S2 are used.

[0159] The wind turbine 101 captures wind energy and the generator speed is controlled by the pitch system. Taking advantage of the slow increase in generator speed, the generator-side converter is controlled to slowly charge the DC capacitor and achieve stability. The DC capacitor can be pre-charged without the need for a pre-charging circuit, which simplifies the hardware structure of the converter.

[0160] Flexible grid connection of wind power converters is achieved by controlling the amplitude and phase of the voltage at the grid-side converter port, effectively suppressing grid connection inrush current;

[0161] By fully utilizing the flexible switching characteristics of the control algorithms of the machine-side converter and the grid-side converter, the integral values ​​of the current controllers of the machine-side converter and the grid-side converter at the switching time are modified by direct setting method, so as to realize the flexible switching from the wind power converter startup strategy to the normal operation strategy.

[0162] The present invention enables effective start-up control of permanent magnet direct-drive wind turbine converters without the need for a pre-charging circuit, effectively suppressing grid-connected current and improving system efficiency and cost.

[0163] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0164] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the currently considered best mode for carrying out the invention, or those features that are not relevant to implementing the invention) may be omitted.

[0165] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0166] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A starting control method for a permanent magnet direct-drive wind turbine converter, characterized in that: include, Wind speed and direction are detected using an anemometer; The generator speed and DC voltage are detected by a speed measuring instrument and a DC voltage detection unit, respectively, to determine the starting conditions of the generator-side converter. Start the machine-side converter, and the machine-side converter executes algorithm MA; Start the grid-side converter when the DC bus voltage equals the set value. u dc_ref Start the grid-side converter, and the grid-side converter executes the GA algorithm; The grid-side converter switching control strategy detects the output voltage of the grid-side converter and the grid voltage. When the amplitude and phase of the output voltage of the grid-side converter are consistent with those of the grid voltage, the grid-side circuit breaker QF2 is closed, and the grid-side converter executes algorithm GB. Machine-side converter switching control strategy, machine-side converter execution algorithm MB; The machine-side converter execution algorithm MA includes: When the generator speed exceeds ω m_pre Or the DC bus voltage exceeds U dc_pre Start the machine-side converter and enable it to execute algorithm MA; where ω m_pre U is the generator speed threshold during startup. dc_pre The threshold for pre-charging the DC bus capacitor during startup; Determine the control objectives for the machine-side converter; Determine the limiting value i of the DC voltage PI regulator (PI-UDC). mq_lim1 ; When the DC bus voltage equals the set value u dc_ref Start the grid-side converter, enable the grid-side converter to execute algorithm GA, and determine the control target of the grid-side converter by detecting the amplitude Um and phase θ of the AC voltage at the PCC point through the phase-locked loop. The voltage feedback value u is obtained by performing coordinate transformation on the output voltage of the grid-side converter. gd and u gq ; will u gd_ref with u gd The error is controlled by the D-axis voltage PI regulator (PI-UGD) to obtain the d-axis current reference value i of the grid-side converter. gd_ref , will u gq_ref with u gq The error is controlled by the Q-axis voltage PI regulator (PI-UGQ) to obtain the q-axis current reference value i of the grid-side converter. gq_ref ; Determine the limiting value i of the D-axis voltage PI regulator (PI-UGD) gd_lim1 The limiting value i of the Q-axis voltage PI regulator (PI-UGQ) gq_lim1 ; When the output voltage and phase of the grid-side converter meet the set conditions with the error at the PCC point, the grid-side circuit breaker is closed. Enable the grid-side converter to execute algorithm GB and determine the control objective of the grid-side converter; Calculate the output reactive power q of the grid-side converter. g ; Will u dc_ref With DC bus voltage u dc The error is controlled by a DC voltage PI regulator (PI-UDC) to obtain the d-axis current reference value of the grid-side converter. i gd_ref ; q g_ref With q g The error is controlled by a reactive power PI regulator (PI-QWT) to obtain the q-axis current reference value i of the grid-side converter. gq_ref ; Determine the limiting value i of the DC voltage PI regulator (PI-UDC). gd_lim2 The limiting value i of the reactive power PI regulator (PI-QWT) gq_lim2； Repeatedly obtain the current feedback value i gd and i gq Step to the modulation wave v of the grid-side converter ga v gb and v gc The transformation process involves several steps; where the current feedback value i gd and i gq The coordinate transformation is performed on the output current of the grid-side converter. Enable the machine-side grid converter control algorithm MB to determine the control objective of the machine-side converter; Determine the output power p of the machine-side converter m ; p m_ref With p m The error is controlled by a power PI regulator (PI-WPT) to obtain the q-axis current reference value i of the machine-side converter. mq_ref The reference value of the d-axis current i md_ref Set to 0; Determine the limiting value i of the power PI regulator (PI-PWT) mq_lim2 ; Repeatedly obtain the current feedback value i md and i mq Step to the modulation wave v of the machine-side converter ma v mb and v mc The transformation process involves several steps; where the current feedback value i md and i mq The coordinate transformation is performed on the three-phase current of the machine-side converter.

2. The start-up control method for the converter of a permanent magnet direct-drive wind turbine generator according to claim 1, characterized in that: The process of detecting wind speed and direction using an anemometer includes: Sampling wind speed v w The average wind speed vw is obtained using a moving average filtering method, and the wind speed exceeds the cut-in wind speed V of the wind turbine. cut_in Close the circuit breaker on the machine side; The pitch control device is activated to gradually reduce the pitch angle.

3. The start-up control method for the converter of a permanent magnet direct-drive wind turbine generator according to claim 1 or 2, characterized in that: The conditions for determining the start-up of the machine-side converter include: The generator speed ωm is detected in real time by a speed measuring instrument, and the DC bus voltage u is detected in real time by a voltage sensor. dc ; Determine the threshold U for pre-charging the DC bus capacitor during startup. dc_pre ; Determine the generator speed threshold ω during startup. m_pre ; Determine the startup conditions for the converter to enter the pre-grid-connected operation mode.

4. The start-up control method for the converter of a permanent magnet direct-drive wind turbine generator according to claim 3, characterized in that: The execution algorithm MA includes: Will U dc_ref with U dc The error is controlled by a DC voltage PI regulator (PI-UDC) to obtain the q-axis current reference value i of the machine-side converter. mq_ref The reference value of the d-axis current i md_ref Set to 0; The current feedback value i is obtained by performing coordinate transformation on the three-phase current of the machine-side converter. md and i mq .

5. The start-up control method for the converter of a permanent magnet direct-drive wind turbine generator according to claim 4, characterized in that: The execution algorithm MA also includes: Determine the integral and output limit value v of the D-axis current PI regulator (PI-IMD) of the machine-side converter. md_lim The integral and output limiting value v of the Q-axis current PI regulator (PI-IMQ) of the machine-side converter. mq_lim ; will i md_ref with i md The error is controlled by the PI regulator (PI-IMD) of the D-axis current of the machine-side converter to obtain the d-axis voltage output value v of the machine-side converter. md , change i mq_ref with i mq The error is controlled by the Q-axis current PI regulator (PI-IMQ) of the machine-side converter to obtain the q-axis voltage output value v of the machine-side converter. mq ; The d-axis voltage output value v of the machine-side converter md and q-axis voltage output value v mq After coordinate transformation, the modulated wave v is obtained. ma v mb and v mc ; The modulation wave v of the machine-side converter ma v mb and v mc The space vector pulse generation unit of the machine-side converter generates the drive pulses to control the operation of the machine-side converter.

6. The start-up control method for the converter of a permanent magnet direct-drive wind turbine generator according to claim 5, characterized in that: Enabling the network-side converter execution algorithm GA also includes: The current feedback value i is obtained by performing coordinate transformation on the output current of the grid-side converter. gd and i gq ; Determine the integral and output limit value v of the D-axis current PI regulator (PI-IGD) of the grid-side converter. gd_lim The integral and output limiting value v of the Q-axis current PI regulator (PI-IGQ) of the grid-side converter. gq_lim ; will i gd_ref with i gd The error is controlled by a D-axis current PI regulator (PI-IGD) to obtain the d-axis voltage output value v of the grid-side converter. gd , change i gq_ref with i gq The error is controlled by a Q-axis current PI regulator (PI-IGQ) to obtain the q-axis voltage output value v of the grid-side converter. gq ; The d-axis voltage output value v of the grid-side converter gd and q-axis voltage output value v gq After coordinate transformation, the modulated wave v is obtained. ga v gb and v gc ; The modulation wave v of the grid-side converter ga v gb and v gc The space vector pulse generation unit of the grid-side converter generates the driving pulses of the grid-side converter to control its operation.

Images