Cyclic Repetitive Control of CVCF PWM DC-AC Converters

In this paper, a cyclic repetitive control (CYRC) scheme is developed and applied to a constant-voltage constant-frequency (CVCF) pulse width modulation (PWM) converter to achieve high tracking accuracy with less consumption of memory space. In this scheme, a novel cyclic sampling strategy is adopted by a down-sampled repetitive controller. The cyclic sampling strategy, which shifts the sampling points every cycle, can provide fractional-order phase lead compensation and enlarge the stability margin. And the gain of the CYRC controller can be increased to decrease the tracking error. With much less memory space consumption, the steady-state tracking performance of CYRC is comparable to that of conventional repetitive control, and is much better than down-sampled repetitive control. The stability criterion, as well as the realization of the CYRC scheme are discussed in detail. Comparison experiments with different controllers are performed in different load situations, and the results demonstrate the effectiveness of the CYRC scheme.