Passivity-based control of multi-functional single-phase capacitive-coupling grid-connected inverter for renewable energy integration and reactive power compensation

In this paper, a single-phase capacitive-coupling grid-connected inverter (CGCI) is used as an interface between power distribution grid and renewable energy source. The operational principle of the CGCI is expounded, which shows that the dc-link voltage of the CGCI can be significantly reduced compared with the conventional method adopting inductance-coupling grid-connected inverter (IGCI) when active power and reactive power are injected into the utility grid simultaneously. Therefore, it can decrease not only the initial investment cost but also the operational losses. In order to reduce steady-state error in current tracking and achieve fast dynamic response for the CGCI, a nonlinear controller based on Passivity-Based Control (PBC) that ensures global asymptotic stability is proposed. Firstly, the comprehensive dynamic mathematic model and EL mathematic model are established under two-phase Direct-Quadrature (DQ) rotating frame. And then, the design process of the controller is elaborated in detail. A series of simulations is carried out using MATLAB/simulink. The results demonstrate almost zero steady-state error in current tracking and fast transient response of the proposed control strategy.