Digital Implementation Issues for a Three-Phase Power Converter Development Using a Repetitive Control Scheme

In this paper the digital implementation of the repetitive control scheme for the three-phase two-level power converter is investigated. The proposed controller has an outer control loop to regulate the output capacitor voltage and an inner control loop for the current tracking process, which is composed of a damping term plus a repetitive control scheme, with the aim to achieve unity power factor and low THD content at the input currents. The repetitive control scheme consists on a negative feedback array of a single delay line plus a feedforward path. The implementation in a digital signal processor of the repetitive term has some issues that are pointed out in this paper. An adaptation rule to the delay parameter of the repetitive controller is proposed in order to improve the system behavior. The experimental results have been carried out in a 30 kVA three- phase power converter prototype to illustrate the good performance of the digital implementation of the controller, including a comparative study of the system behavior under the repetitive controller with the theoretical and the modified delay parameter.