Multi-rate predictive cascade speed control of synchronous machines in automotive electrical traction drives

Abstract

The speed control of electric machines employed in automotive electrical traction drives is a challenging problem. Indeed, these applications are subject to physical and computational constraints. This paper addresses this challenging problem by employing a multi-rate predictive cascade state-space control structure, focusing on the design of the outer loop controller. Firstly, the mathematical model for the outer loop control, including also the dynamics of the inner control loop, is obtained. Secondly, a model predictive control approach based on a flexible control Lyapunov function is employed to control the rotor speed. Thirdly, in order to obtain the unmeasured state and the torque load a state and disturbance observer is employed. As a consequence, offset-free operation of the control system is also obtained. A realistic simulation scenario using a previously validated model and comparison with a linear quadratic regulator scheme are considered in order to illustrate the effectiveness of the proposed method.