Capacity Allocation And Optimal Operation Strategy Of Photovoltaic-Storage Systems Based On Extended QV Bus-type Power Flow

The sustained growth in power demand, shortages of traditional sources and the opening of electricity market drive the large-scale development of photovoltaic(PV) generation rapidly. With the proposition of active management mode, distribution generation(DG) is required to participate in dispatch operation as a part of distribution networks. The uncertain output of DGs such as PV brings many challenges to the operation of power system. Accessing energy storage systems(ESS) at point of common coupling(PCC) of PV constitutes photovoltaic-storage system that can smooth the fluctuation of PV output and take part in the dispatch operation of distribution network actively. How to configure the capacity of ESS, build a reasonable operation strategy and realize the optimal operation of distribution network with photovoltaic-storage systems become an unavoidable problem of the operation of photovoltaic-storage system.According to characteristics of point of common coupling(PCC) of photovoltaic and energy storage access, this paper extending QV bus-type to describe PCC feature is more reasonable, the derivation and prototype in distribution network of QV bus-type is introduced in detail. Furthermore, solution of power flow calculation with QV bus-type is shown in this paper. and example verifying it effectively and accurately, which provides a theoretical basis for further attention voltage to achieve the power output coordinated control of photovoltaic-storage systems.A joint day-ahead scheduling of photovoltaic-storage system is put forward in core view of voltage control at PCC and at the aim of suppressing voltage fluctuation. And then two scenarios whether storage system output excesses its limit are considered. The result shows that the proposed strategy has a significant improvement on suppressing voltage fluctuation and improving power flow.On the basis of the previous research, a method for multi-period PCC voltage setting considering source-load peak-valley characteristics is proposed in order to make capacity of energy storage system more reasonable allocation and more effectively using. Considering system operational constraints, ESS operational constraints and capacity allocation constraints, a multi-objective optimization model of ESS capacity allocation was constructed based on two aspects of the whole day energy loss and capacity of ESS, solving Pareto optimal solution set to provide the decision-making basis for ESS capacity configuration and operation strategy. Comparative analysis shows that the method in this paper could achieve ESS optimal allocation flexibly, and ESS operation states are all in reasonable range under the corresponding operation strategy. The result comparison shows that the proposed operation strategy has a significant effect on improving voltage quality, decreasing ESS configuration capacity and reducing the whole day energy loss, the results fully demonstrate the rationality and validity of the optimal model and the method for multi-period PCC voltage setting.