Direct Power Control For Double-stator Brushless Doubly-fed Wind Power Generator

This paper is based on the key project of the National Natural Science Foundation of China(NSFC)“Research on the key fundamental issues of Caged Rotor Coupled Dual-stator Modular Brushless Doubly-fed Wind power Generation System”(project number: 51537007),this paper proposes an improved double stator brushless doubly-fed generation based on the brushless doubly-fed generation as the control object,it employs direct power control to control the active and reactive power of the system.The main research contents of this article are as follows:(1)The magnetic field modulation mechanism of a novel double stator brushless doubly-fed generator(DSBDFG)is analyzed.Based on the composite rotor,a stator and rotor subsystem is added inside the motor through the magnetic separation ring,and then the stator winding outside the rotor is connected in series(or in parallel)to form a double stator motor,forming two sets of motor units that can work independently,so as to effectively improve the space utilization and efficiency index of the motor.Because the DSBDFG has two sets of stator windings with different pole numbers,the back-to-back rotor must be used for pole number conversion in order to complete the electromechanical energy conversion.Therefore,it is necessary to analyze the magnetic field modulation mechanism of the back-to-back rotor.(2)The derivation and simulation analysis of DSBDFG mathematical model.According to the voltage,flux and current equations of DSBDFG the mathematical models are derived in a-b-c static coordinate system and d-q rotating coordinate system respectively,and the formulas of motor power and electromagnetic torque are obtained,Provides the necessary preparation for further research in direct power control(DPC).Through simulation and analysis of DSBDFG mathematical model under no load,we confirm that the power winding voltage does not change with the operating mode of the motor,and has good VSCF constant voltage power generation characteristics.(3)The traditional look-up table direct power control based on the variable sliding mode structure has been improved.optimized direct power control scheme based on look-up table,and the hysteresis control of the conventional direct power control method based on look-up table is optimized,and the hysteresis control in traditional direct power control is changed into the mode combining sliding mode variable structure and SVPWM,so as to effectively reduce the system power deviation,switch loss and harmonic content,and make the control system have better control performance.(4)Rotor speed identification and maximum power tracking without position sensor.In order to reduce mechanical faults and improve system stability,a speed identification and maximum power tracking control based on model reference adaptive(MRAS)is proposed.In this control winding,the expected value of current component is different from the actual value in d-q rotating coordinate system,and the error variable is corrected by adaptive rate,so that the difference between the two variables is close to 0.Then,according to the real-time comparison between the expected value of active and reactive power of the power winding and the observed value,The motor is corrected in real time,improving the control accuracy of the motor and improving its robustness and controllability.Simulated direct power control of traditional look-up tables,direct power control with improved sliding mode variable structure and maximum power tracking control based on MRAS,analyzed in MATLAB / Simulink.The results show that the sliding mode variable structure control and MRAS speed identification direct power control are correct and effective,which can be used for further study of direct power The control strategy provides a good reference and reference.