Robust repetitive controller for compensation of odd-harmonic components in PWM converters

In repetitive control systems, the period of the disturbance may not be integral multiple of sampling rate or may change with time slightly. This will affect the performance of RC controller seriously. In this paper, a robust repetitive control method is proposed to handle non-integral delay in RC control systems. Another feed-forward path is added to the conventional odd-harmonic controller to guarantee that the control gain for all odd-harmonics remain satisfied even when the period of the fundamental signal suffered from disturbance or is not integral multiple of the sample period. Stability and convergence of this approach are proved mathematically. Computer simulation results are provided to confirm its effectiveness further.