Modelling and Stability Study of a Single Stage Buck-Boost Inverter for PV Application

The paper presents a control methodology for a recently proposed single stage buck-boost inverter in photovoltaic (PV) application. With the use of the recently proposed topology, wide output range characteristic of PV panel is able to be covered and a high efficient and low common-mode noise inverter system is able to be guaranteed. Targeting on PV application, an integrated control methodology is presented in this paper. A double current loop control is applied to convert the PV solar power into a high quality AC grid power and to avoid the influence from the CL resonant characteristic in the buck-boost inverter. In addition, a maximum power point tracking (MPPT) unit is integrated into the system to track the maximum power point of PV panel without the need of any additional current sensors. In this paper, a detail system analysis is presented which includes small signal analysis model and stability evaluation among the whole system. Performance of the presented control methodology is experimentally verified in a 600W PV inverter platform. Both steady state and the dynamic characteristic are shown with a good agreement with the theoretical knowledge.