A Hybrid Cross Coupling - Master Slave Technique for Speed Synchronization of Multi PMSMs System Using PID Controller and On-Line Master Selector

Abstract

Some speed synchronization techniques of multiple electric motors system are well known such as master reference, master slave and cross coupling. The cross coupling technique is only applicable for two motors system whereas the master slave technique can be applied to more than two motors but it provides a poor synchronization performance. This paper offers a hybrid cross coupling master slave (CC-MS) technique with master selector for angular speed synchronization which can be applied to more than two motors. In order to evaluate performance, this paper also proposes two performance indexes i.e. regulation performance index PI1 and synchronization performance index PI2. A proportional integral derivative (PID) controller is equipped at each motor for speed feedback, and the speed coupling between motors is facilitated by a coupling constant. An on-line master selector automatically selects the motor with the largest load as the master when the system is working. Values of the PID controller gains and the coupling constant are determined using the pole placement method. The proposed hybrid CCMS technique has been evaluated through computer simulations using a vehicle with four permanent magnet synchronous motors (PMSMs) in Matlab-Simulink environment. The vehicle is simulated moving at a downhill track where the load of four PMSMs drops one by one in sequence. Performance comparison was carried out between the proposed technique and the previously published techniques: master reference and CC-MS without master selector. Simulation results show that the proposed technique gives smaller PI1 and PI2 than the other two techniques.