Research On Control Method For Disc Contra-rotating Permanent Magnet Synchronous Motor

Disc Contra-rotating permanent magnet synchronous motor(Contra-rotating PMSM)has one stator and two rotors.There is one winding cross surrounded on the stator.There is Air-gap magnetic field in bilateral Air-gap,when Three-phase current flow in winding.It is at advantage of little volume,large power density,symmetrical mechanical parameters and electrical parameters of rotors.So it is easy to control and have broad application prospects in rotating propellers driver of underwater vehicle,wind power and electric aircraft.It can effectively use wind power and Water-flow power.Disc Contra-rotating PMSM is equivalent to two PMSM connected in series.It requires to control and keep the speed of two rotors in the same.The vector control strategy proposed by now papers is based on only one rotor field oriented,thus that rotor is Closed-loop controlled and the other one is of freedom to follow state.Traditional Direct Torque Control strategy(DTC)proposed by now papers is invalid,because it is easy to select stator voltage vector incorrectly for two rotor share one stator flux and affect each other through it.Under two control strategy proposed by now papers,two rotor will loss of synchronism when load of them change asymmetrically.The main purpose of this paper is to control and keep speed of two rotors in synchronism,when loads of them change asymmetrically.This paper proposed a strategy based on two rotors field oriented and a DTC based on Space Vector Modulation(SVM).Under these two strategies,it can build a control system containing two Closed-loop control systems with a module of choosing object to be Closed-loop controlled.It chooses object timely according to actual situation.By means of Closed-loop controlling rotors in turn,two rotors can be Closed-loop controlled.At first,according to the structure of Contra-rotating PMSM and a theory that it is equivalent to two PMSM connected in series,it build a mathematical model of Contra-rotating PMSM and a simulation model of it.Under strategy of vector control based on only one rotor field oriented,it builds a simulation module of Contra-rotating PMSM control system.The simulation results prove effectiveness of the simulation module of Contra-rotating PMSM and the control strategy when loads of two rotors equal or change symmetrically.But two rotors will loss of synchronism when loads of them change asymmetrically.So method proposed by now papers is of limitation.And then,this paper build vector diagram for two situations respectively that rotors keep in synchronism and loss of synchronism.This paper gives the reason of why two rotors loss of synchronism under strategy based on only one rotor filed oriented when loads of them change asymmetrically.This paper propose a vector control strategy based on two rotors field oriented and build simulation module for control system with result proving the effectiveness of it.Traditional DTC is not effective for Contra-rotating PMSM.This paper gives the reason why rotors will loss of synchronism when loads of two rotors change asymmetrically.And then,this paper proposes a DTC based on SVM.Under this strategy,it can build two control systems which choose the rotor needed to be Closed-loop controlled and build Closed-loop control system for it.By means of Closed-loop controlling rotors in turn,it can effectively lifted interaction between the two rotors by stator flux.Two rotors are controlled independently.Simulation results show the effectiveness of the method when loads of bilateral rotors change asymmetrically.At last,it builds a hardware test platform for Contra-rotating PMSM and prepares software for the controlling of it.Experiment results prove the effectiveness of the control method and this method has a reference value for a control system that an inverter drives two motors.