Multirate Repetitive Control for PWM DC/AC Converters

In this paper, a multirate repetitive control (RC) scheme is developed and applied to constant-voltage constant-frequency pulsewidth modulation converter systems. In this scheme, the converter has a fast sampling rate, while the repetitive controller has a reduced sampling rate. The learning is based on the downsampled input and error signals in previous periods. The multirate RC synthesis method, as well as its convergence and stability conditions, is discussed in detail. Systematic experiments are also carried out to illustrate the effectiveness of multirate RC. Experimental results show that, with a well-designed multirate RC, the total harmonic distortion can be very low. This approach can reduce the computation delay caused by the plug-in RC in each switching control period and will enhance the system stability. Consequently, the switching control frequency of the converter can be increased to compensate the control performance loss. This approach is suitable for design of cost-effective and flexible converter control systems.