An all-in-one power electronic solution for the introduction of PV and storage for smart grids

Due to a growing green consciousness and the royal Belgian subsidy policy towards photovoltaic solar power, PV-installations are showing up all over the country. The distribution grid, once designed to deliver electric power, has to deal with a problem of overvoltage during high irradiation levels. This paper presents the first results of a research project that was funded by the Flemish government to investigate the influence of renewables on the power quality and vice versa. The first aim of the project was to come up with practical solutions for the overvoltage in distribution grids. The presented solution is the introduction of a limited battery pack at residentual PV production sites to buffer energy at overvoltage. Today´s household PV-inverters switch off at overvoltage resulting in the loss of green energy. The discussed all-in-one inverter avoids these losses. Firstly, a model of the distribution grid is given to quantify this green energy loss on a typical Belgian distribution feeder. Simulations on this model show that the local installation of a buffer size of only one third of the average daily PV yield of the PV-installation can already eliminate the overvoltage along the feeder. Secondly, a possible power electronic solution for limiting the active power injection by buffering is presented. This all-in-one power electronic solution offers battery charging, grid coupling possibilities as well as single phase solar energy inverting with MPP tracking from a single inverter platform. The platform is real-time controlled from Matlab/Simulink via a target PC. The paper concludes with a control algorithm for this all-in-one inverter.