Research On Dual-Rotor Permanent Magnet Sychronous Wind Power Generator Control System

With the increasingly exhausted energy resources, wind power generation, as a renewableenergy, has caused more and more attention recently. Along with the development of windpower generation, improving the utilization rate of wind power has become a hot spot.Previous research always concerned the controlling methods to improve the utilization ratio,but there is an upper limit on wind energy utilization coefficient. In this paper, a novel windpower generator, the dual-rotor permanent-magnet wind generator, whose armature part andpermanent-magnet rotor rotate at the opposite directions, was proposed. In an ideal condition,the relative speed and power output of generator double, enhancing the output voltage andgreatly improving the wind energy utilization. Furthermore, the lowest working wind speed isjust the half of traditional permanent-magnet generators while the highest keeps the same,thus widening the range of the working wind speed. So there is a unique advantage in windpower field.However, the structure design of the dual-rotor permanent-magnet wind generator isvery different from that of the traditional permanent-magnet synchronous wind powergenerator. Thus the research of its maximum power point tracking and pitch control has animportant theoretical and practical significance. So aiming at the dual-rotorpermanent-magnet synchronous wind power generator, this paper comprehensively analysesthe control strategy of the whole wind conditions.Firstly, a brief introduction about the physical construction and working principle of thedual-rotor permanent-magnet synchronous wind power generator is presented, and themathematical model of the dual-rotor permanent-magnet synchronous wind power generatorunder the three-phase static and dq rotating coordinate is deduced according to the principleof the opposite movement. As the electromagnetic relation of the dual-rotorpermanent-magnet wind generator is the same as that of traditional permanent-magnetsynchronous wind power generator, the dual-rotor permanent-magnet synchronous windpower generator used vector control and space vector PWM control is simulated byMATLAB software, which verifies the validity of the mathematical model of the dual-rotorpermanent-magnet synchronous wind power generator. Aiming at the dual-rotor permanent-magnet synchronous wind power generator andtraditional permanent-magnet synchronous wind power generator having equal properties inmany principle, the mathematical model of the dual-rotor permanent-magnet synchronouswind power generator system, including the wind turbine, permanent-magnet synchronouswind power generator and grid-side converter, is analyzed firstly. Then all kinds of themaximum power point tracking control strategies of permanent-magnet synchronous windpower generator are summarized and the control method of the grid-side converter isintroduced. All in all, what have done above pave a solid way for finding a appropriatecontrol strategy of the dual-rotor permanent-magnet synchronous wind power generator.The dual-rotor permanent-magnet synchronous wind power generator as a novel motorwhose the greatest innovation is are that its outer and inner rotor can rotate freely and it canutilize wind energy secondly will improve wind utilization coefficient. Through analyzing themathematical model of the front and back wind turbine and mechanical motion equation ofgenerator, a design method about the rotor radius of the wind turbine is obtained. Accordingto the mechanical motion equation, combined with the maximum power tracking controlmethod of the traditional permanent-magnet synchronous wind power generator, themaximum power control method without detection wind speed is presented. Besides, theissues to be cared in the rotor radius design of the wind turbine, based on the research of allpossible work modes of the back wind turbine, is proposed.When dual-rotor permanent-magnet synchronous wind turbine at lower than the ratedwind speed operation, the relative movement between inside rotor and outside rotor improvethe output voltage and the power output of generator. Operating at the lower than the ratedwind speed, because the back wind turbine utilize wind energy twice, dual-rotorpermanent-magnet synchronous wind power generator will make the output power ofgenerator may be higher than the rated power. Aiming at the dual-rotor permanent-magnetsynchronous wind power generator of this special working mode, it propose a control strategywhich make output power of generator near the rated power. The front wind turbine still keepthe maximum power tracing control, thus it can get the given speed signal of back windturbine combining the rated power, the speed of generator, the winding copper loss and otherconditions. the signal and the real-time speed of back wind turbine forming closed loop control, it can adjust pitch angles of back wind turbine which can control the speed andrestrict the output power of the back wind turbine. It will restrict the power output near therated power. Higher than the rated wind speed operation, the back wind turbine must stop bymechanical control, thus dual-rotor permanent-magnet synchronous wind generator regard asordinary permanent-magnet synchronous wind generator. It take pitch control method toadjust front wind turbine to keep output power near the rated power of generator.Simulation model of dual-rotor permanent-magnet synchronous wind power generationsystem was built in Matlab/simulink software.The simulation results show that the correctnessof the maximum power tracing control and the pitch control strategy. It has certain theoreticalresearch significance because the back wind turbine can utilize wind energy twice and greatlyimprove wind energy utilization of the system.