Modelling, analysis and control design of a two-stage photovoltaic generation system

Photovoltaic (PV) generation systems with two-stage topology are recently emerged due to its flexibility of installation. However, most studies on dynamic stability of the PV generation system are based either on the first DC/DC stage or the second DC/AC stage in previous literature. A system-level modelling and stability has not been reported significantly, which is a crucial issue for the design of the PV system controllers. In this study, an integrated small-signal model for a two-stage PV generation system is derived to investigate the system stability and sensitivity. The proposed model takes into account the dynamics of the DC-link capacitor that was generally regarded as an ideal constant voltage source in previous researches. A v(2) feedback based DC-link voltage control scheme is presented to address the non-linear relationship between capacitor energy and its voltage and thus a high performance DC-link voltage regulation is achieved. Hardware-in-loop tests using real time digital simulator are presented to validate the feasibility of the proposed method.