Simulation Of The Control Strategy Of Current Source Supply PM Motor

Permanent magnet (PM) motor has smaller sizes, lighter weight, and better reliability compared with DC motor and is becoming one of the study focuses of marine electric propulsion. It can be foresaw that the study on PM motor will promote the development of marine electric propulsion in recent ten or twenty years. The most popular control strategy of PM motor is to apply the phase current according to the rotor position properly. The rotor position detector also gives speed signal for adjusting phase current, which is often realized by PWM chopper. This kind of control system can achieve such a good performance as the DC motor does and is often called self-controlled varying frequency system.There are two kinds of power supply for PM motors: one is current source supply and the other is voltage source supply. For the voltage source supply, the control system has a simpler main circuit. However, the waveforms of motor currents are difficult to control. The harmonic components of the current will produce torque pulsation, additional losses and some EMI problems. For the current source supply, the current waveforms are much easy to control though it has more complicated main circuit and more voltage harmonics. From the point of view of having smooth torque and better EMC for electric propulsion application, the current source supply is preferred.This paper will study the self-controlled varying frequency system with current supply, including control strategy, parameter optimization and commutation process. As the Simulink in MATLAB has strong point in model building, solution and result analyzing, it is chosen as the tool for simulation study.As a new attempt, study such complex system with Simulink is rather unfrequented. The simulation demands excellent hardware because of the computational complexity. General-use computer can hardly work. So, this paper offers two models for study. The simple model is for study of control strategy and performance, and the complex model for study of commutation process.The study of control strategy and performance include the performance of starting, acceleration and deceleration. Study of commutation process includes the study of voltage and current of each phase and the converter capacitance. A example with a too small converter capacitance is shown to explain that inappropriate parameter may cause commutation failure.The simulation has value in offering help for choosing control strategy, control parameters and other system parameter.