Research On Power Quality And Fault Analysis Of Distributed Multi-access Generation System

Distributed generation mainly based on renewable energy technologies caneffectively alleviate the energy and environmental problems caused by rapideconomic development. Micro-grid contains several DGs, it can take full use ofprimary energy. Its high flexibility makes it possible to track load variation well,which is helpful for economical and effective operation of power grid. As distributedgeneration technology matures, micro-grid contains more DGs, and has larger DGcapacity. Research on protection and power quality of multi-acess access distributedgeneration system has great significance in both theory and practice.Most distributed generators are connected to power grid through power electronicdevices. The output of this kind of Inverter Based Distributed Generator is related tocontrol strategy, and the fault behavior is absolutely different from prefault state. Thiskind of nonlinear characteristic makes IBDG different from conventional generator.Thevenin equivalent model which replaces the generator with constant voltage andfixed impedance can not be used. Fault current provided by IBDG rises in severalcircles, and because of current limitation the fault current is relatively little, whichmay lead to malfunctioning of overcurrent protection. The current transient process iscaused by current loop of the controller; the duration is related to response speed ofthe controller. A protection strategy is proposed for muti-access generation system.The access of DGs poses great chanllenges for protection and power quality.Containing power electronic switches DG becomes a harmonic source in distributionnetwork. There can be harmonic resonance in muti-access generation system. Paralleland series resonance in a practical project is analysed and simulinked in Matlab.Power flow can be changed by the access of DGs, which in turn changes the voltagelevel of the distributed network. The access of DGs compensates voltage drop moreefficiently than reactive compensatin devices. But the voltage level is influenced byaccessing capacity, accessing position, fluctuate output. The analysis is validated bysimulation, and measures of improving voltage level by DGs are proposed.