A discrete repetitive current controller for single-phase grid-connected inverters

This paper proposes a discrete repetitive controller to be applied to control the output current of a full-bridge single-phase grid-connected inverter. The current is synchronized with the voltage grid by a phase-locked loop algorithm. The control design procedure assures system stability, robustness to voltage harmonic distortions and a fast error convergence. It is based on a notch filter which compensates the resonant peak from a plant formed by a LC filter at the inverter output in parallel with a local resistive load. To increase the margin stability of the system, a low-pass filter is employed in the positive feedback of the repetitive controller. To verify the control technique, simulations employing the PSIM software are performed. Moreover, a DSP-based kit board from Texas Instruments (TMDSHV1PHINVKIT) containing a full-bridge inverter and a LC filter is used to experimentally test the controller. Results demonstrate the method robustness against harmonic distortions and also show the control efficacy to promptly track abrupt changes in the reference amplitude for the current.