An Improved Optimal Sizing Method for Wind-Solar-Battery Hybrid Power System

This paper proposes an improved optimal sizing method for wind-solar-battery hybrid power system (WSB-HPS), considering the system working in stand-alone and grid-connected modes. The proposed method is based on the following principles: a) high power supply reliability; b) full utilization of the complementary characteristics of wind and solar; c) small fluctuation of power injected into the grid; d) optimization of the battery's charge and discharge state; e) minimization of the total cost of system. Compared with the traditional methods, the proposed method can achieve a higher power supply reliability while require less battery capacity in stand-alone mode. And in grid-connected mode, the optimization strategy based on energy filter is further utilized to achieve the optimal battery capacity. Thus, the proposed method can achieve a much smaller fluctuation of power injected into the grid. In addition, the battery's charge and discharge state can be optimized thanks to the consideration of the battery's depth of discharge (DOD), the charge/discharge current, rate and cycles, which will prolong the battery's lifetime. A case study of WSB-HPS located in Hohhot, China is presented to verify the advantages of the proposed optimal sizing method.