Research On The Power Quality Improvement Program Of The Microgrid

With the rapid development of the power industry, traditional large-scale power grid hasbecome the main power supply channel with its unique advantages. However, along with theincreasing energy depletion and environmental pressure, distributed generation of renewableenergy rises rapidly. Distributed generation can solve the vulnerability of the large-scale grid, butit is usually limited and isolated in order to reduce the impact on the grid. The microgridcoordinates effectively the contradiction between distributed generation and large-scale grid. Asan important part of smart grids, the microgrid has become gradually a focus of concern fordomestic and overseas experts, and China also continues to increase the support. This paperfocuses on the study of the power quality improvement in the microgrid.Firstly, for the three control methods of a single distributed generation (DG), thefundamentals and the structures are analyzed and the control models are established. Thecommon control strategies of the microgrid containing multiple microsources are researched,including master-slave and peer-to-peer control strategy. Meanwhile their advantages anddisadvantages are compared and their applicable conditions and analyzed. All above lays thefoundation for the study of microgrid power quality.Secondly, with regard to the harmonic pollution and voltage fluctuations in the microgrid,the synthetic system of active power filter(APF) and static var compensator(SVC) is used as thepower quality improvement program. After the study of the shunt active power filterfundamentals and harmonic detection methods based on instantaneous reactive power theory, thesimulation models are established. Two current tracking technologies of APF are analyzed, andthe hysteresis comparison control is choosed. The fundamentals of SVC are analyzed and thecontrol model is established. APF is installed in the microsource exports to filter harmonic andcarries out small reactive power compensation. SVC in the load side is used for large capacityreactive power compensation on the spot. APF can achieve fast tracking compensation andovercome the SVC shortcoming of slow response to rapid-changing power, while SVC can makeup for the weakness of APF inadequate compensation capacity.They complement each other andcan effectively solve the harmonic pollution and voltage fluctuations in the microgrid.Finally, according to the established control models, the simulations are built byMATLAB/Simulink and the power quality improvement method is verified. Simulation resultsshow the correctness and feasibility of the synthetic systemof APF and SVC in improving powerquality of the microgrid.