Model predictive control with a fixed switching frequency for a 5-level flying capacitor converter

This paper presents a novel finite-set model predictive control technique with a fixed switching frequency for a 5-level FCC converter. Standard implementations of finite-set model predictive control (FS-MPC) are typically characterised by a variable switching frequency, a high noise floor and a large voltage and current ripple. A method is proposed by selecting a fixed switching period and dividing it into smaller evaluation steps. The switching behaviour is obtained by using the analogy of PWM with triangular carriers to define regions during which only specific switching transitions are allowed. To account for the repetitive nature of the desired switching waveform, an average receding horizon prediction method is used. An anticipated prediction is made by calculating the average value for one switching period ahead, according to the position and state in the current switching period. The control method was practically implemented and evaluated, proved to be feasible and provided satisfactory results.