Research On Economic Operation Optimization Of Photovoltaic Storage Micro-Grid

The instability and high-cost always restrict the development of PV-storage micro-grid. Besides, the increasing requirements of high-quality power and widespread enforcement of time-of-use power policy bring new challenges in power distribution of PV-storage micro-grid. Therefore, the operation optimization of PV-storage micro-grid gradually becomes a hot issue in current research ereas.In this paper, PV-storage micro-grid was taken as the research object, which consists of photovoltaic, batteries, grid-connected inverter, bi-directional inverter and electric load. Based on time-of-use power policy, the randomness of PV output power and load were taken into consideration and a lot of research work was done in modeling, model solving and robustness. The main research work is as follows:Firstly, the structure and composition of PV-storage micro-grid system are introduced, and this article analyzes the properties of the photovoltaic, batteries and inverters as well as the calculation method of batteries depreciation cost, which is based on "rainflow method". On this basis, with the unequal-interval time dividing method, taking minimizing operation cost as optimization objective, and considering power balance constraints, grid exchange power constraints, batteries power constraints and batteries state of charge constraints, the PV-storage micro-grid operation optimization model under certain conditions was established.Secondly, according to the operation optimization model, sample generation method and an updating method of probability distribution was improved based on traditional cross-entropy algorithm, and the steps of solving PV-storage micro-grid operation optimization model which uses cross-entropy algorithm was presented. With operating data from lOkW hybrid PV-storage micro-grid system of Shandong University, the optimization model and its solving strategies were simulated and tested. The results show that the optimal strategies can effectively reduce operation cost, especially with lower replacement cost of batteries. The effectiveness of optimization model and solving strategies are verified.Finally, this article considers the uncertainty of PV output power and load and takes them as interval numbers. Based on certain optimization model, robust operation optimization model for PV-storage micro-grid was established with min-max regret degree method. Then a two-stage relaxation method based on cross-entropy algorithm is used to solve the robust model. What’s more, combined with the operating data from thereal system, the robust model and its solving strategies was simulated and tested. Meanwhile, those results were analyzed and compared with the strategies of certain models. The results show that the strategies of the robust model performs little inferiorly than certain models under expectation, but it has a better adaptability on various values of uncertain parameters. The advantages of the robust model are more significant especially when the replacement cost of batteries is lower.