Research On Optimal Selection For System Parameters In Hybrid Networked Renewable-Storage Islanding Microgrid

The optimal selections for inverters' control parameters and impedances in microgrid are very important with the expansion of microgrid and the diversification of network form.Inappropriate parameters in microgrid system will lead to power quality problems,and even bring about interactive stability problems among the inverters.Therefore,the optimal selections for system parameters of hybrid networked renewable-storage islanding microgrid are researched in this paper.Firstly,the composition of microgrid and the control method s based on characteristic of different generation units are composed in this paper.And the importance of the optimal selections for system parameters of microgrid is emphasized.The hybrid networked renewable-storage microgrid which consists of storage units based on droop control and photovoltaic power generation units based on constant current control is considerd in this part.Moreover,the control characteristic s and mathematical models of droop control inverter and constant current control inverter are researched for the foundation of the next study.Secondly,the voltage characteristic and the frequency characteristic based on droop control at the PCC are deduced in this part.And the effects of droop control parameters on the voltage characteristic at the PCC,the frequency characteristic at the PCC and the power stability are analyzed in the following.Moreover,a dual optimization control strategy which could calculate the optimal droop control parameters is proposed in this paper.The frequency deviation and the voltage deviation at the PCC could be reduced by adopting the optimal droop control parameters.Meanwhile,good stability margin and better stability performance are remained in the system.And the power quality and stability of the microgrid are improved effectively.Thirdly,interactive stability problems among the inverters would be caused by the fast interactions of inner loops and impedances when more and more own stable inverters connect to the microgrid.In order to analyze interactive stability problems among the inverters,an efficient impedance analysis theory applied in single-bus islanding microgrid is proposed in this paper.The proposed efficient impedance analysis theory could be used as theoretical foundation for the optimal selections of inner loop control parameters and impedances.Easy analysis procedure and efficient analysis are remained by using the efficient impedance analysis theory.Finally,the design principle,hardware design and software design of the hybrid networked renewable-storage microgrid experimental platform are introduced.And the experiments for single droop control inverter,single constant current control inverter and the whole experimental platform are carried out.Moreover,the optimal selection of droop control parameters based on the dual optimization control strategy is verified by this microgrid experimental platform.