Droop Control Strategy Of Microgrid

Microgrid can not only integrate the transmission characteristics of the electricity producing system of new energy but also make full use of those ones, so it is a very important research subject in the areas of the energy usage and environment protection in our future, when the microgrid is at mode transition and islanding operation mode, which would lead to the load power lower than the standards and the decline of voltage quality. To resolve this issue, accorde the characteristics of wind/photovoltaic hybrid microgrid and low voltage (Low Voltage, LV) microgrid and LV wind/photovoltaic hybrid microgrid, proposed control strategies applicable to characteristics of respective microgrid. All control strategy proposed in this paper based on droop control strategy rationale, droop control strategy is not depend on communication systems, better reliable and flexible using ways. The research content is as follows:In the paper, elaborate on the microgrid and microgrid structure basic concepts, analysis of the domestic and foreign research status and research focus, points out the importance of the development of China’s microgrid, description the paper has valid of theoretical and ideals for practical significance.Elaborated the working principle and the mathematical model of the generation system in microgrid; In the PSCAD/EMTDC simulation software, build the simulation model. Integrated the advantages and disadvantages of battery energy storage system and super capacitor energy storage system, discusses the important role of two energy storage system at mode transition and islanding operation mode in microgrid, lay theoretical foundation for the following.For wind/photovoltaic hybrid microgrid structural characteristics, proposed two energy storage system droop coordinated control strateg. With this control strategy, can increase the stability active power of the load while improving the voltage quality of the load in microgrid. To build microgrid and control strategies simulation model, simulation the proposed control strategy. The simulation results to verify feasibility of the proposed control strategy based on the theoretical analysis validate droop factor role played with the control strategy. Because LV microgrid line impedance characteristics different high voltage microgrid line impedance characteristics, LV microgrid is difficult to adopt traditional droop control strategy. For LV microgrid propose the virtual frame transformation droop control strategy. To distributed generation system of LV microgrid output active power and reactive power control is more precise. LV microgrid with this control strategy can realize seamless transition, stable power supply to the load at islanding operation mode at the same time to optimize the power quality.A coordinated droop control strategy of dual-source energy storage system with virtual coordinate transformation is proposed by researching on the operation characteristics of low voltage (LV) wind/photovoltaic hybrid microgrid. Using virtual coordinate transformation-based droop control not only solves the coupling problem between active and reactive power of LV microgrid, but also enables a coordinated control on BESS and SCESS to achieve the smooth handoff from grid-connected mode to isolated mode of LV microgrid for wind, photovoltaic and energy storage.