Linearisation of permanent magnet synchronous motor model

Linearisation of a nonlinear system allows a simple fixed controller to be applied for the control of the linearised system. In this paper, a method of linearisation of permanent magnet (PM) synchronous machine model is proposed. The proposed method, removes the dominant quadratic nonlinearity of the model without leaving behind higher order terms in the system as is common with the existing quadratic linearization techniques. Also, the proposed technique does not introduce any singularities in the system unlike in the case of conventional feedback linearization techniques. To illustrate the technique proposed, a numerical model, which is based on the actual parameters of a PM machine, is linearised. Also, a MATLAB simulation of the dynamic equations of the machine is carried out. Simulation results show that the proposed technique effectively linearises the machine model. Also, the linearised system exhibits a stable open loop response compared to the open loop system response before linearization. The proposed technique can also be applied to linearise induction motor and wound rotor synchronous machine models.