Multi-rate predictive cascade DC-link voltage control in hybrid electric vehicles

The DC-link voltage control of electric machines employed in hybrid electric vehicles is a challenging problem, subject to several physical and computational constraints. This paper answer to these challenges by employing a multi-rate predictive cascade state-space control structure with focus on the design of the outer loop voltage controller. Firstly, the mathematical model, including also the dynamics of the inner current control loop, is obtained and linearized. Secondly, a one-step ahead model predictive controller based on a flexible control Lyapunov function is employed to control the DC-link voltage. The load current and the unmeasured state are obtained by using a state and disturbance observer, helping to achieve also off-set-free operation. A simulation scenario, including a comparison with a linear quadratic regulator scheme, is employed to illustrate the effectiveness of the proposed method.