Coordinated Control Of DC Micro-grid Based On The DC Bus Voltage Signal

With the deteriorating of living conditions and increasing depletion of fossilresources, distributed generation technology using of renewable energy has attracted awidely attention. But a large number of distributed power directly connect to the gridwill cause adverse impacts to the security and stability of the power grid, and theconcept of micro-grid proposed effectively solve the problem of large-scaledistributed power access. DC micro-grid due to strong controllability, high efficiency,lower line losses advantages is becoming a hot research, but because of the limitedcapacity of micro-grid system, anti-disturbance ability, when changing the micro-gridoperation mode, the DC bus voltage prone to violent fluctuations and power quality isreduced. Therefore, in order to improve the stability of DC micro-grid operation, thehybrid energy storage based on supercapacitor and coordinated control strategy of DCmicro-grid based on the DC bus voltage signals were studied in this paper.This paper describes the structure and topology of DC micro-grid, workingprinciple and the mathematical model of the wind power generation unit, photovoltaiccells and micro-turbines and other distributed power in the micro-grid were studied,with an emphasis on the model analysis of grid converter, studied the networktopology of converters and decoupling control, lay the foundation for coordinatedcontrol strategy of DC micro-grid.Secondly, according to the working principle of the battery and supercapacitor,established mathematical model, deeply studied of the structure of the three parallelhybrid energy storage system, and constructs topology hybrid energy storage system,the battery charge and discharge process was optimized using multi-stage constantcurrent charge and discharge control strategy, extended battery operating time andusing life. Through the simulation analysis of hybrid energy storage system, theresults demonstrate the effectiveness of hybrid energy storage system control strategy.Finally, using the based on the DC bus voltage signal of DC micro grid coordinated control strategy, designed threshold voltage of each converter and priority,each converter using the droop control, by the threshold voltage and the priority levelof fit, to ensure power balance of each unit in the micro-grid, so that the bus voltageis maintained within the allowable range. Simulation results show the effectiveness ofthe coordinated control strategy.