Comparison of Proportional+Integral Control and Variable Structure Control of Interior Permanent Magnet Synchronous Motor Drives

A comparison of the performance of an interior permanent synchronous motor drive, when driven by two different types of direct torque controllers, is presented in this paper. Both these controllers utilize space vector modulation (SVM) to generate switching signals for the inverter. The first of these control strategies uses a Proportional and Integral (PI) controller and reference flux vector calculator (RFVC) to determine the reference stator flux linkage vector, instead of a switching table and hysteresis controllers employed by the basic DTC. The other control strategy, namely variable structure control scheme, is based on the design of discontinuous control signal that drives the system states towards special manifolds in the state-space. The switching surfaces are chosen in a way that the system will have the desired behaviour as the states converge to the manifolds. Both these control strategies have had positive impacts on improving the performance of the interior permanent magnet (IPM) synchronous motor drive during transient, steady state and dynamic operations. However, they each have their own drawbacks.