Position sensorless control method and system for doubly-fed induction wind driven generator

Abstract

The invention discloses a position-sensorless control method and system for a doubly-fed induction wind generator, and the method comprises the steps: collecting a three-phase stator current value and a three-phase rotor current value, obtaining a stator current vector and a rotor current vector under a static coordinate system, inputting the two vectors into a phase-locked loop, and obtaining a phase-locked loop; obtaining an included angle between the stator current vector and the rotor current vector; removing the power grid voltage from the closed-loop control loop, and only taking the power grid voltage as a feed-forward item to carry out feed-forward compensation on the included angle; the voltage of the direct current bus is kept stable through the grid-side PWM converter; giving an active instruction according to the rotor speed; and the active instruction and the reactive instruction are converted into an instruction of a rotor current quadrature-direct axis component through a rotor side PWM converter so as to realize decoupling control. The method is mainly used for position-sensorless control of a DFIG wind driven generator or a similar topological structure, does not need traditional position sensor structures such as an encoder and a rotary transformer, and has better power grid fault ride-through capability and robustness.

Description

Technical Field

[0001] This application relates to the technical field of wind turbines, and particularly to a sensorless control method and system for a doubly-fed induction wind turbine. Background Art

[0002] Compared with permanent magnet synchronous wind turbines, DFIG wind turbines have the advantages of a smaller converter capacity and lower cost, and are widely used in wind farms, accounting for more than 60% of the power generation in China's wind power. In the operation control of DFIG wind turbines, accurate rotor position information is essential. However, the precise mechanical structure of position sensors (such as encoders, resolvers, etc.) is relatively easy to damage, which is a weak link in wind turbine generators.

[0003] In order to improve the operation stability of DFIG wind power systems, different sensorless control strategies have been successively proposed, which can be mainly divided into the following three categories: The first category is the open-loop calculation method, which directly solves the rotor position angle through the mathematical and physical equations of DFIG wind turbines; the second category is the model reference adaptive control strategy, which subtracts the adjustable model from the reference model and realizes a closed-loop rotor position observer through a PI controller; the third category is the high-frequency signal injection method, which injects high-frequency signals on the rotor side or stator side and receives the response signals generated by electromagnetic induction on the other side, and uses the electromagnetic coupling characteristics of DFIG to solve the rotor position angle.

[0004] Although there has been some academic research on the sensorless technology of DFIG, there is no report on its use in mass-produced products. The main reason is that the existing DFIG rotor position estimation methods are usually only applicable to normal grid conditions. Once grid voltage dips, surges and other faults occur, the stator voltage and current of the motor will be directly and severely affected, which will in turn cause rotor position estimation errors and lead to failure of fault ride-through. Research has found that: the open-loop method relies heavily on motor parameters, and the lack of a closed-loop feedback mechanism results in large position estimation errors during transient processes, making it difficult to meet the requirements of low-voltage ride-through; although the high-frequency signal injection method is insensitive to motor parameters and can realize position observation during voltage dips, it seriously affects power generation quality and is difficult to be practically applied; the reference model of the model reference adaptive method is greatly disturbed during the transient process of drastic changes in electrical quantities, and it is impossible to effectively observe the rotor position during the fault process.

[0005] In summary, the existing DFIG sensorless control strategies are difficult to effectively observe the rotor position under grid fault conditions and difficult to meet the grid's fault ride-through ability indicators. Summary of the Invention

[0006] In view of the deficiencies of the above-mentioned background art, the embodiments of the present application provide a sensorless control method and system for a doubly-fed induction wind generator to solve the technical problems in the related art that it is difficult to effectively observe the rotor position under the condition of a grid fault and it is difficult to meet the grid's fault ride-through ability index.

[0007] The present invention adopts the following technical solutions to achieve the above-mentioned invention purpose: According to the first aspect of the embodiments of the present application, a sensorless control method for a doubly-fed induction wind generator is provided, including: Collect three-phase stator current values and rotor current values to obtain the stator current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system; Input the stator current vector and the rotor current vector into a phase-locked loop to obtain the angle between the stator current vector and the rotor current vector; Remove the grid voltage from the closed-loop control loop and use only the grid voltage as a feedforward term to perform feedforward compensation on the angle; Maintain the stability of the DC bus voltage through the grid-side PWM converter; give an active power command according to the rotor speed; convert the active power command and the reactive power command into commands for the direct and quadrature axis components of the rotor current through the rotor-side PWM converter to achieve decoupled control of active and reactive power.

[0008] According to the second aspect of the embodiments of the present application, a sensorless control system for a doubly-fed induction wind generator is provided, including: A collection module for collecting three-phase stator current values and rotor current values to obtain the stator current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system; A phase-locked loop control module for inputting the stator current vector and the rotor current vector into a phase-locked loop to obtain the angle between the stator current vector and the rotor current vector; A feedforward control module for removing the grid voltage from the closed-loop control loop and using only the grid voltage as a feedforward term to perform feedforward compensation on the angle; A DFIG control module for maintaining the stability of the DC bus voltage through the grid-side PWM converter; giving an active power command according to the rotor speed; converting the active power command and the reactive power command into commands for the direct and quadrature axis components of the rotor current through the rotor-side PWM converter to achieve decoupled control of active and reactive power.

[0009] According to the third aspect of the embodiments of the present application, an electronic device is provided, including: One or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in the first aspect.

[0010] According to a fourth aspect of the embodiments of the present application, there is provided a computer-readable storage medium, on which computer instructions are stored, and when the instructions are executed by a processor, the steps of the method as described in the first aspect are implemented.

[0011] The technical solutions provided by the embodiments of the present application may include the following beneficial effects: As can be seen from the above embodiments, the technical solution of the present application removes the grid voltage from the closed-loop control loop and uses the grid voltage as a feedforward term to perform feedforward compensation on the included angle, which overcomes the problem that it is difficult to effectively observe the rotor position under the condition of grid faults in the existing DFIG sensorless control strategy, and further improves the fault ride-through ability of the DFIG wind power generation system under the sensorless control strategy.

[0012] In addition, the present application does not use any motor parameters in the phase-locked loop link, and only uses the stator self-inductance in the phase-locked loop link , which overcomes the problem of parameter drift in the existing DFIG sensorless control strategy and improves the robustness of the control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0014] Figure 1 is a flowchart of a sensorless control method for a doubly-fed induction wind generator according to an exemplary embodiment.

[0015] FIG. 2 is a Π equivalent circuit diagram of a DFIG wind generator equivalent to the stator side according to an exemplary embodiment.

[0016] FIG. 3 is a spatial position relationship diagram of a stator, a rotor, a stator current, and a rotor current according to an exemplary embodiment.

[0017] Figure 4 shows the performance of a DFIG wind turbine system when the grid voltage drops to 0.2 p.u. from 1.5 s to 2.125 s under the condition of using the sensorless control method of the present invention; where (a) is the three-phase stator voltage waveform; (b) and (c) are respectively the compensation angle output by the voltage feed-forward link and the error between the observed value and the actual value of the rotor position angle; (d) and (e) are respectively the rotor current in the synchronous rotating coordinate system and the rotor current waveform in the abc three-phase stationary coordinate system; (f) and (g) are respectively the stator current in the synchronous rotating coordinate system and the rotor current in the abc three-phase stationary coordinate system.

[0018] Figure 5 is a complete control block diagram of a DFIG including a rotor position observer and a DFIG control system according to an exemplary embodiment.

[0019] Figure 6 is a block diagram of a sensorless control system for a doubly-fed induction wind turbine according to an exemplary embodiment. Detailed implementation manners

[0020] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0021] The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "the", and "said" used in the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0022] Figure 1 is a flowchart of a sensorless control method for a doubly-fed induction wind turbine according to an exemplary embodiment; Figure 5 is a complete control block diagram of a DFIG including a rotor position observer and a DFIG control system according to an exemplary embodiment. As Figure 1 and Figure 5 shown, the control method includes the following steps: S1: Collect the three-phase stator current values and rotor current values to obtain the stator current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system; Specifically, the three-phase stator currents of the doubly-fed induction generator are collected by a current sensor and the three-phase rotor currents . The collected three-phase stator and rotor currents are transformed to the two-phase stationary coordinate system through Clarke transformation: (1) (2) Thus, the stator current vector in the stator stationary coordinate system can be expressed as: (3) The rotor current vector in the rotor stationary coordinate system can be expressed as: (4) S2: Input the stator current vector and the rotor current vector into a phase-locked loop to obtain the angle between the stator current vector and the rotor current vector; this step includes the following sub-steps: S21: Perform an inversion process on the stator current vector in the stator stationary coordinate system to obtain , and perform a vector cross-product operation on it and the rotor current vector in the rotor stationary coordinate system that has undergone phase rotation, where represents the stator current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system, thereby generating an error signal characterizing the phase deviation; Figure 2 Specifically, according to the DFIG type equivalent circuit shown, the stator-side voltage equation in the stator stationary reference coordinate system can be given by equation (5): (5) The stator flux linkage expression is given by equation (6): (6) The coordinate transformation relationship between the rotor current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system is given by equation (7): (7) In equations (5)-(7), is the stator resistance of the motor, is the equivalent inductance of the power grid, is the self-inductance of the stator, is the mutual inductance between the stator and the rotor. , , , which are the grid voltage, stator current, and stator flux vector in the stator stationary reference frame respectively. is the rotor current vector in the stator stationary coordinate system. is the rotor current vector in the rotor stationary coordinate system. is the rotor position angle.

[0023] Substitute equation (6) into equation (5) and ignore the terms containing the stator resistance grid inductance : (8) Equations (7) and (8) show that there will be a phase difference between the inverted rotor current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system: (9) Utilize the said difference to perform a coordinate transformation, rotate to the same phase as the inverted rotor current vector in the stator stationary coordinate system, and then perform a cross product operation on the two to obtain the error signal : (10) S22: Input the said error signal into a proportional-integral (PI) controller for processing, and the output of the controller directly corresponds to the rotor angular velocity ; Specifically, specifically, the error signal ζ represents the phase deviation between the inverted stator current vector in the stator stationary coordinate system and the rotated rotor current vector. Input this error signal into the proportional-integral controller, and the mathematical expression of the controller is: (11) where is the proportional gain coefficient, is the integral gain coefficient. Through the action of the PI controller, when the error signal exists, the controller will generate a corresponding output to adjust the rotor angular velocity so that the error signal gradually decreases to zero, thereby achieving phase locking.

[0024] This design utilizes the phase relationship between the stator current vector and the rotor current vector, and can obtain the rotor angular velocity through a closed-loop PI controller without using any motor parameters.

[0025] S23: By integrating the angular velocity in the time domain, the inverse-phase stator current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system are obtained, and the included angle between them is calculated; S24: This included angle is sent back to the rotation transformation link of the rotor current vector to form a closed-loop control structure; specifically, the included angle obtained in step S23 is fed back to the coordinate transformation link of the rotor current vector to adjust the rotation angle of the rotor current vector . The rotation transformation aligns the phase of the rotor current vector with that of the inverse-phase stator current vector in the stator stationary coordinate system. When the two are completely aligned, the result of the cross-product operation (error signal ) will approach zero, indicating that the phase-locked loop has been locked.

[0026] Such a closed-loop control obtains an important intermediate variable . Using this intermediate variable, the final rotor position angle can be obtained through subsequent feed-forward compensation. In addition, the closed-loop of the entire phase-locked loop does not introduce the grid voltage, which provides guarantee for its stable operation under grid faults.

[0027] S3: Remove the grid voltage from the closed-loop control loop and use the grid voltage only as a feed-forward term for feed-forward compensation of the included angle; this step includes the following sub-steps: S31: According to the DFIG mathematical model, obtain the mathematical relationship in the stator stationary coordinate system regarding the stator current vector, rotor current vector, and grid voltage vector; Specifically, the mathematical relationship is given by Equation (8).

[0028] S32: By observing the three-phase stator current information and three-phase grid voltage information, deduce the phase difference between the inverse-phase stator current vector in the stator stationary coordinate system and the rotor current vector in the stator stationary coordinate system through Equation (8); (12) S33: Use the phase difference as a feed-forward compensation term to perform feed-forward compensation on the included angle.

[0029] Specifically, the spatial position relationships of the aforementioned stator current, rotor current, stator, and rotor are as Figure 3As shown in the figure. The rotor position angle can be calculated by means of feedforward compensation through formula (9): (13) It should be noted that the feedforward compensation term is directly calculated through the information of the grid voltage and the stator current. The advantage of this design is that the grid voltage information is separated from the control closed-loop, avoiding the direct impact of the severely fluctuating grid voltage information during grid faults on the control closed-loop, and improving the system's ability to ride through faults.

[0030] S4: Maintain the stability of the DC bus voltage through the grid-side PWM converter; give the active power command according to the rotor speed; convert the active power command and the reactive power command into the commands of the direct-axis and quadrature-axis components of the rotor current through the rotor-side PWM converter to achieve the decoupled control of active and reactive power.

[0031] Among them, maintaining the stability of the DC bus voltage through the grid-side PWM converter includes the following sub-steps: A1: Collect the DC bus voltage value and compare it with the set DC bus voltage reference value to generate a voltage error signal; Specifically, use a voltage sensor to collect the voltage value at both ends of the DC bus and compare it with the preset DC bus voltage reference value to calculate the voltage error signal .

[0032] A2: Input the voltage error signal into a proportional-integral (PI) controller for processing to obtain the command of the d-axis component of the grid-side converter current; Specifically, input the voltage error signal into a proportional-integral (PI) controller, and the output of the PI controller is the command of the d-axis component of the grid-side converter current :

[0033] (14) A3: Collect the three-phase current of the grid-side converter and convert it to the synchronous rotating coordinate system to obtain the d-axis and q-axis current components; Specifically, use a current sensor to collect the three-phase current of the grid-side converter , , . First, convert the three-phase current to the two-phase synchronous rotating coordinate system through Clarke transformation and Park transformation: (15) (16) Where is the grid voltage vector angle, usually obtained through a grid voltage phase-locked loop (PLL). The d-axis of the synchronous rotating coordinate system is aligned with the grid voltage vector, facilitating subsequent independent decoupling control of the d-axis and q-axis currents.

[0034] A4: Subtract the actual d-axis and q-axis current values from the d-axis and q-axis current command values respectively and send them into their respective PI controllers. After decoupling compensation for the outputs of the PI controllers, d-axis and q-axis voltage control signals are generated; Specifically, subtract the actual d-axis current value from the d-axis current command value and send the difference into the PI controller to obtain the output . Subtract the actual q-axis current value from the q-axis current command value and send the difference into the PI controller to obtain the output .

[0035] By performing decoupling compensation on the above PI controller outputs through equations (17) and (18), d-axis and q-axis voltage control signals can be obtained.

[0036] (17) (18) where L is the inductive reactance of each phase incoming line reactor, is the grid voltage angular frequency.

[0037] A5: Obtain three-phase modulation waveforms by performing an inverse coordinate transformation on the d-axis and q-axis voltage control signals, and generate switching signals for the grid-side PWM converter through space vector modulation technology (SVM), thereby achieving stable control of the DC bus voltage Specifically, first convert the voltage control signals in the synchronous rotating coordinate system back to the two-phase stationary coordinate system through an inverse Park transformation: (19) Then generate PWM switching signals through space vector modulation technology (SVM) to achieve control of the DC bus voltage.

[0038] Among them, giving the active power command according to the rotor speed includes the following sub-steps: B1: Based on the maximum power point tracking (MPPT) principle, establish a mapping relationship curve between the rotor speed and the optimal active power ; Specifically, the relationship between the optimal active power of the wind turbine and the rotor speed can be expressed as: (20) Among them, is a constant related to the wind turbine, is the number of pole pairs of the motor, is the gearbox transmission ratio.

[0039] During the actual operation of the wind turbine generator set, it is difficult to accurately detect the wind speed and it is impossible to directly give the corresponding optimal speed command. Establish the mapping relationship curve between the rotor speed and the maximum output power, not aiming at speed control, but aiming at the wind turbine operating on the optimal power curve, and finally making the wind turbine operate at the optimal speed.

[0040] B2: According to the current observed value of the rotor speed, find the corresponding optimal active power point on the mapping relationship curve (MPPT curve), and use the obtained optimal active power value as the active power command; Specifically, during actual operation, the speed obtained by the speed observer, obtain the optimal active power point on the MPPT curve by means such as looking up a table, and use it as the active power command value: (21) Among them, the active command and the reactive command are converted into the command of the direct and quadrature axis components of the rotor current through the rotor side PWM converter to realize the decoupling control of the active and reactive power, including: C1: Based on the principle of field-oriented control, establish the mathematical model of the doubly-fed induction generator, and determine the corresponding relationship between the active power output by the stator and the d-axis component of the rotor current, and the reactive power output by the stator and the q-axis component of the rotor current; Specifically, under the stator voltage-oriented control strategy, the active power and reactive power output by the stator can be expressed by equations (22) and (23): (22) (23) C2: Convert the total electromagnetic power command from the MPPT control into the command value of the active power output by the stator; Specifically, according to the relationship between the active power output by the DFIG stator and the total electromagnetic power, the total electromagnetic power command value can be converted into the stator output power command value

[0041] (24) Among them, is the stator copper loss, ; slip ratio .

[0042] C3: Convert the reactive power command into the command value of the q-axis component of the rotor current according to the corresponding relationship; Specifically, the command value of the reactive power output from the DFIG stator to the power grid has nothing to do with the maximum wind energy tracking, and its command is given by the designer according to the needs of the power grid or the needs of DFIG operation optimization.

[0043] C4: Compare the actual active power and reactive power output from the stator with the command values to obtain an error signal: Specifically, the actual active power output from the stator is expressed as: (25) Subtract the command value of the active power output from the stator from the actual active power output from the stator to obtain an error signal : (26) Similarly, the actual reactive power output from the stator is: (27) Subtract the command value of the reactive power output from the stator from the actual reactive power output from the stator to obtain an error signal : (28) C5: Input the error signal into their respective PI controllers for processing to obtain the command values of the d-axis and q-axis components of the rotor current.

[0044] Specifically, input the error signal into the PI controller to obtain the command value of the d-axis component of the rotor current ; input the error signal into the PI controller to obtain the command value of the q-axis component of the rotor current .

[0045] C6: Subtract the command values from the actual d-axis and q-axis components of the rotor current respectively and then input them into their respective PI controllers; after decoupling compensation of the output of the PI controller, obtain the command values of the d-axis and q-axis components of the rotor voltage; generate the switching signals of the rotor-side PWM converter through space vector modulation technology, and then the decoupled control of the active and reactive powers can be realized.

[0046] Specifically, subtract the difference between the d-axis component of the rotor current and the command value of the d-axis component of the rotor current and input it into the PI controller to obtain the output ; The q-axis component of the rotor current The q-axis component command value of the rotor current The difference is sent to the PI controller to get the output .

[0047] Through formula (29) and formula (30) , After decoupling compensation, the rotor voltage d-axis component command value is obtained The rotor voltage q-axis component command value .

[0048] (29) (30) in, is the magnetic flux leakage coefficient, is the rotor self-inductance, For mutual induction, is the stator flux, slip angular velocity , is the grid angular frequency.

[0049] By utilizing space vector modulation technology, a switching signal of a rotor-side PWM converter is generated according to the rotor voltage d-axis and q-axis component command values, thereby realizing decoupling control of the DFIG active power and reactive power.

[0050] The specific operation effect of the present invention can be Figure 4 Grid voltage Fall to ,Keep Later Restore to ,like Figure 4 As shown in (a) in Figure 2. Before the voltage drops, the DFIG wind power generation system is in a stable state, the grid voltage feedforward compensation link outputs a stable compensation value, and the static observation error of the rotor position angle is zero. At this moment, the grid voltage drops to .like Figure 4 As shown in (b), the feedforward compensation link can quickly respond to changes in the grid voltage; and the phase-locked loop link can still effectively observe the angle between the measured and rotor current vectors because it does not contain the grid voltage component. Figure 4 As shown in (c) in the figure, during the entire grid voltage drop process and the grid voltage recovery process, the maximum error of the angle estimation of the position sensorless control method proposed in the present invention is only 0.1 radian. Figure 4 (d) and (e) are the rotor current waveforms in the synchronous rotating coordinate system and the three-phase stationary coordinate system respectively. The system can effectively control the rotor AC and DC axis current before, during and after voltage drop. , indicating that the DFIG wind power generation system is not unstable during the fault ride-through process, and the sensorless control method proposed by the present invention has strong robustness and fault ride-through ability.

[0051] As can be seen from the above embodiments, in the present application, by removing the grid voltage information from the phase-locked loop closed-loop control system and introducing a feed-forward compensation term of the grid voltage to compensate the angle output by the phase-locked loop, the rotor position angle observation value is obtained. and the rotor speed . During a grid fault, since the grid voltage information of the faulty grid does not directly enter the closed-loop control system, the rotor position observer proposed in the present application can still effectively observe the rotor position. Substituting the obtained rotor position angle observation value and the rotor speed into the subsequent maximum wind power tracking link and the active and reactive power decoupling control link, effective control of the motor can be achieved under normal operating conditions and grid fault conditions.

[0052] Corresponding to the foregoing embodiments of the sensorless control method for a doubly-fed induction wind generator, the present application also provides an embodiment of a sensorless control system for a doubly-fed induction wind generator.

[0053] Figure 6 is a block diagram of a sensorless control system for a doubly-fed induction wind generator shown according to an exemplary embodiment. Referring to Figure 6 , the device includes: Acquisition module 1, configured to acquire three-phase stator current values and rotor current values to obtain a stator current vector in the stator stationary coordinate system and a rotor current vector in the rotor stationary coordinate system; Phase-locked loop control module 2, configured to input the stator current vector and the rotor current vector into a phase-locked loop to obtain an angle between the stator current vector and the rotor current vector; Feed-forward control module 3, configured to remove the grid voltage from the closed-loop control loop and use only the grid voltage as a feed-forward term to perform feed-forward compensation on the angle; DFIG control module 4, configured to maintain the stability of the DC bus voltage through the grid-side PWM converter; give an active power command according to the rotor speed; convert the active power command and the reactive power command into commands for the direct and quadrature axis components of the rotor current through the rotor-side PWM converter to achieve decoupled control of active and reactive power.

[0054] Regarding the device in the above embodiments, the specific manners in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0055] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to the descriptions of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this application. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0056] Correspondingly, this application also provides an electronic device, including: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the sensorless control method for a doubly-fed induction wind generator as described above.

[0057] Correspondingly, this application also provides a computer-readable storage medium, on which computer instructions are stored, and when the instructions are executed by a processor, the sensorless control method for a doubly-fed induction wind generator as described above is implemented.

[0058] After considering the specification and practicing the content disclosed herein, those skilled in the art will readily think of other implementation schemes of this application. This application is intended to cover any variations, uses, or adaptive changes of this application, which follow the general principles of this application and include the common general knowledge or conventional technical means in the technical field not disclosed in this application. The specification and embodiments are only regarded as exemplary, and the true scope and spirit of this application are pointed out by the claims.

[0059] It should be understood that this application is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is only limited by the appended claims.

Claims

1. A position sensorless control method for a doubly-fed induction wind generator, characterized in that: include: Collect three-phase stator current values ​​and rotor current values ​​to obtain a stator current vector in a stator stationary coordinate system and a rotor current vector in a rotor stationary coordinate system; Inputting the stator current vector and the rotor current vector into a phase-locked loop to obtain an angle between the stator current vector and the rotor current vector; The grid voltage is removed from the closed-loop control loop, and only the grid voltage is used as a feedforward item to perform feedforward compensation on the angle; The DC bus voltage is maintained stable through the grid-side PWM converter; an active power instruction is given according to the rotor speed; the active power instruction and reactive power instruction are converted into instructions of the rotor current AC and DC axis components through the rotor-side PWM converter to achieve decoupling control of active and reactive power.

2. The method according to claim 1, characterized in that Inputting the stator current vector and the rotor current vector into a phase-locked loop to obtain an angle between the stator current vector and the rotor current vector includes: The stator current vector in the stator stationary coordinate system is After inversion treatment, , and compare it with the phase-rotated rotor current vector in the rotor stationary coordinate system Perform a vector cross multiplication operation, where Represents the stator current vector in the stator stationary coordinate system The rotor current vector in the rotor stationary coordinate system The angle between them is used to generate an error signal representing the phase deviation. ; The error signal The input is processed by a proportional-integral (PI) controller, whose output directly corresponds to the rotor angular velocity. ; By the angular velocity Perform time domain integration to obtain the anti-phase stator current vector in the stator stationary coordinate system The rotor current vector in the rotor stationary coordinate system The angle between ; This angle It is sent back to the rotation transformation link of the rotor current vector to form a closed-loop control structure.

3. The method according to claim 1, characterized in that The grid voltage is removed from the closed-loop control loop, and only the grid voltage is used as a feedforward item to perform feedforward compensation on the angle, including: According to the DFIG mathematical model, the mathematical relationship between the stator current vector, the rotor current vector and the grid voltage vector equivalent to the stator stationary coordinate system is obtained; By observing the three-phase stator current information and the three-phase grid voltage information, the phase difference between the anti-phase stator current vector and the rotor current vector is calculated using the mathematical relationship; The phase difference is used as a feedforward compensation term for the angle Perform feed-forward compensation.

4. The method according to claim 1, characterized in that: Maintaining DC bus voltage stability through grid-side PWM converter, including: Collect the DC bus voltage value and compare it with the set DC bus voltage reference value to generate a voltage error signal; Inputting the voltage error signal into a proportional-integral (PI) controller for processing to obtain a d-axis component instruction of the grid-side converter current; Collect the three-phase current of the grid-side converter and convert it to a synchronous rotating coordinate system to obtain the d-axis and q-axis current components; The actual value of the d-axis current is compared with the d-axis current command value, and a d-axis voltage control signal is generated through a PI controller; the actual value of the q-axis current is compared with the q-axis current command value, and a q-axis voltage control signal is generated through a PI controller; The d-axis and q-axis voltage control signals are transformed into three-phase modulation waveforms through inverse coordinate transformation, and the switching signals of the grid-side PWM converter are generated through space vector modulation technology, thereby achieving stable control of the DC bus voltage.

5. The method according to claim 1, characterized in that Give active power instructions according to the rotor speed, including: Based on the maximum power point tracking principle, a mapping relationship curve between rotor speed and optimal active power is established; According to the current rotor speed observation value, the corresponding optimal active power point is searched on the mapping relationship curve, and the optimal active power value found is used as the active power instruction.

6. The method according to claim 1, characterized in that The active power command and the reactive power command are converted into the command of the rotor current AC and DC axis components by the rotor side PWM converter to realize the decoupling control of active power and reactive power, including: Based on the principle of field-oriented control, a mathematical model of the doubly-fed induction generator is established to determine the corresponding relationship between active power and the d-axis component of the rotor current, and between reactive power and the q-axis component of the rotor current. Converting the active power command from the MPPT control into a rotor current d-axis component command value through the corresponding relationship; Converting the reactive power command into a rotor current q-axis component command value through the corresponding relationship; The actual values ​​of the d-axis and q-axis components of the rotor current are compared with the command value to generate a current error signal; The current error signal is input into respective PI controllers for processing to obtain control signals of the d-axis and q-axis components of the rotor voltage; the switching signal of the rotor-side PWM converter is generated by space vector modulation technology, thereby realizing decoupling control of active and reactive power.

7. A position sensorless control system for a doubly-fed induction wind turbine, characterized in that: include: The acquisition module is used to acquire three-phase stator current values ​​and rotor current values ​​to obtain the stator current vector in the stator stationary coordinate system and the rotor current vector in the rotor stationary coordinate system; A phase-locked loop control module, used for inputting the stator current vector and the rotor current vector into the phase-locked loop to obtain an angle between the stator current vector and the rotor current vector; A feedforward control module, used for removing the grid voltage from the closed-loop control loop, and using only the grid voltage as a feedforward item to perform feedforward compensation on the angle; The DFIG control module is used to maintain the DC bus voltage stability through the grid-side PWM converter; give active power instructions according to the rotor speed; and convert the active power instructions and reactive power instructions into instructions for the AC and DC axis components of the rotor current through the rotor-side PWM converter to achieve decoupling control of active and reactive power.

8. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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