A Method of Solving Three-Phase Power Unbalance Problem with PV Inverters Connected to the Grid in Series

Abstract

Due to the continuous advancement of photovoltaic (PV) poverty alleviation policy, large-scale household PV arrays are connected to rural power grid. However, most of the distributed PV arrays are single-phase, so there are lots of differences between the output power of each phase, which exacerbates the three-phase power unbalance problem in rural power grid. In order to solve this problem, this paper proposes a new topology in which the grid-current is controlled by an DC-AC converter of each phase and PV inverters are connected to the grid in series. After adopting series connection, the adjustment is more flexible and effective and the three-phase power unbalance problem can be solved more pertinently because the single-phase line is controlled separately. Finally, a simulation model is built in MATLAB and the simulation results fully prove the effectiveness of this topology.