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.