With the increasing demand of users for power sources and quality, how to provide high-quality renewable clean energy has become a key issue of power electronics. The main idea of this paper is to develop a composite control including a PI control and repetitive control for a single-phase grid-connected inverter to eliminate the effects of harmonics, which can obtain better steady-state and dynamic responses of the single-phase inverter system and reduce the net current harmonics. The modelling of a single-phase inverter is first introduced; then a first-order repetitive control is developed for the proposed grid-connected inverter. Moreover, a high-order repetitive controller is adopted to further improve the robustness against the uncertainties in the period of signals. The stability and performance analysis are given for the first-order repetitive control and high-order repetitive control. Finally, comparative simulations are conducted in a circuit-level inverter model, which show the effectiveness of the proposed method.

In this paper, a single-phase reactive power compensation control for static compensator (STATCOM) is developed. The primary novelty lies in that the reactive power compensation of STATCOM is reformulated as an equivalent tracking control for the reactive current, and a novel unknown system dynamics estimator (USDE) is also investigated to address the unknown system dynamics. A modeling phase based on a basic structure of single-phase STATCOM and the principle of STATCOM is first carried out to describe its behavior. To address the unknown dynamics and external disturbances, a new USDE is then developed, so that the modeling uncertainties and external disturbances can be accommodated without using a function approximator, where the demanding computational costs and tedious parameter tuning in the other control schemes are remedied. Finally, based on the proposed estimator, we design a composite control with a proportional integral (PI) feedback controller and the proposed estimator to achieve precise current tracking. The convergence analysis of both the estimation error and the control error is also given. Simulation results using a realistic simulator are presented to show the efficiency of the suggested strategy.

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