Discrete-time full-order sensorless control of high-speed interior permanent magnet synchronous motor in electric vehicle traction system

Abstract

A discrete-time full-order sensorless control strategy for high-speed interior permanent magnet synchronous motor (IPMSM) used in electric vehicle (EV) traction system is designed in this paper. While most speed and position observer (SPO) methods are developed in the continuous-time domain, the presence of a unit-time-delay block existed in feedback loop and discretisation of the algorithm can lead to performance degradation during digital implementation. In this work, speed and angle are observed using the discrete-time four-order IPMSM model. A quadrature phase-locked loop model with compensation is introduced, and its stability condition is established for the first time. Furthermore, to address the potential for sudden speed changes in vehicle applications, the parameter range is further refined to keep the estimation error within a specified range. The sliding mode observer is discretised and its stability is analysed using discrete Lyapunov theory. Additionally, the time sequence of interactive signals between SPO and field-oriented control is thoroughly examined to ensure accurate time cycle. Finally, the proposed control strategy is validated and demonstrated through bench tests and real EV (LS6 of IM Motors) tests with a 190 kW IPMSM, which can improve the accuracy by 0.3 radians at 8000 rpm compared to traditional methods, and achieve stable control at 15,000 rpm on the test bench and at 120 kph with the EV.