Stability Analysis And Optimal Dispatch Of DC Microgrid

As an effective way for distributed generation to connect to power grid,microgrid has been widely concerned by scholars at home and abroad.There are a large number of distributed power sources,such as photovoltaic cells,supercapacitors and so on,which output direct current in microgrid.There are also a large number of direct current loads in user’s negative terminals,such as mobile phone chargers,LED lighting equipment,etc.These loads also need direct current in essence.Therefore,compared with AC system,DC microgrid can accept distribution more efficiently.The power supply can supply the DC load,reduce the intermediate links of energy conversion,and improve the efficiency of energy utilization.Based on the stability analysis of DC microgrid,this paper makes reasonable power allocation and capacity allocation for hybrid energy storage system,and puts forward reasonable dispatching strategies for distributed generation,energy storage system and load to realize the safe and stable operation of DC microgrid system.The specific research contents are as follows:Firstly,this paper built the DC microgrid and determine the topology of the system.The mathematical models of wind turbine,photovoltaic cell,battery and supercapacitor in DC microgrid are analyzed.The output characteristics of wind turbine and photovoltaic cell when the wind speed changes and the illumination intensity changes are studied.The Boost circuit is simulated and analyzed.Secondly,the small signal model of DC micro-grid is established.Through eigenvalue analysis,the influence of distributed generation output and load power on the stability of DC micro-grid is studied.The stability analysis method of DC microgrid based on wind-solar load multi-disturbance is proposed.The stochastic dynamic model of DC microgrid is established and its stochastic disturbance is analyzed.Then aiming at the influence of power fluctuation and load fluctuation of distributed generation on DC micro-grid system,a hybrid energy storage system control strategy is proposed to suppress bus voltage fluctuation.On this basis,the cost,energy loss,uncertainty of distributed generation and load access,and operating range of SOC are considered.The multi-objective capacity optimization of combined energy storage system is carried out.Finally,the multi-time scale dispatching model of DC micro-grid is established,and the dispatching plan for the day after the day is formulated,and the short-time optimal dispatching is carried out within the day to maximize the reliability and economy of the micro-grid operation.