Optimal Design Of Energy Storage Box For Mechanical Elastic Energy Storage Unit Served By Permanent Magnet Synchronous Motor And Its Grid-connected Control

In recent years, Renewable energy power generation has gotten a lot of attention and rapid improvement, but its intermittence and volatility bring great challenge to safe operation of power system so that large-scale energy storage technologies are needed urgently. At the time, power system are striding forward smart grid and are confronted with traditional problems such as peak load shifting, safe and stable operation and so on, which also promote the development of energy storage technology. Only pumped-storage satisfies the demand of large-scale storage capacity among existing energy storage technologies owing to the limitation of material and operation principle, but it requires special geographical position. Therefore, our team proposed a mechanical elastic energy storage scheme served by permanent magnet motor based on spiral torsion spring energy storage. Energy storage box with spiral torsion spring inside is one of the key elements in mechanical energy unit and play an important role on the performance of energy unit. In this paper, a new hybrid biogeography based optimization(HBBO) is proposed by blending biogeography based optimization(BBO) with genetic algorithm and differential evolution algorithm(DE), and is applied to optimize energy storage box, and a direct current grid-connection control strategy with feed-forward compensation is presented at the same time.Firstly, operation principle of mechanical elastic energy storage served by permanent magnet motor and composition of energy storage box are introduced, and the energy storage capacity, energy storage density and efficiency of mechanical energy storage prototype are deduced and calculated, the linkage type of energy storage box is demonstrated in detail. Then, a new hybrid mutation operator is presented by mixing GA and DE, and a new hybrid strategy is proposed to blend BBO and DE, chaotic search and feasibility based constraint handling mechanism are also introduced into BBO, which are the improvement strategy adopted by HBBO, and the developed BBO is verified by simulation on numerical benchmark functions and engineering optimization functions in contrast with other advanced optimization technologies. Next, three optimization functions including maximize volume energy density, mass energy density and minimizing comprehensive volume are determined, optimization model of energy storage box is proposed considering relevant constraints in actual operation which is solved by HBBO. At the end, a new grid-connection control strategy is proposed by introducing voltage feed-forward compensation and improved strategy is testified by simulation on Matlab/simulink.Through search, this paper comes some conclusion as the following. First, hybrid strategy improves global search ability of BBO greatly, and HBBO is efficient and effective in both numerical optimization field and engineering optimization field. Second, the target parameters of energy storage box scheme gotten by HHBO are improved greatly in contrast with traditional design method. Third, the direct current control strategy with voltage feed-forward compensation can restrain grid voltage disturbance effectively and realizes unit grid-connection desirably.