The Application On Power Quality Improvement Using APF And SVC In Micro Grid

Micro Grid is a new power grid mode of low voltage, organizing by separate sources of different type, different capacity with certain control strategy, and provides energy to local load or the distributed network. The distributed sources in Micro Grid, which usually are permitted to provide energy after current conversion by power electronic devices, are not stable because of external atmosphere. The electronic devices needed in Micro Grid introduce certain mount of current harmonics, and the voltage of distributed sources may also fluctuate sometimes, which debases the power quality of Micro Grid, more serious, makes the equipment abnormal in Micro Grid. In order to solve these problems, we must take some steps. APF and SVC are two effective equipments. APF is mainly used to mitigate current harmonics, and compensate low capacity reactive power. It has fast response and good harmonics mitigation performance, but needs complex current detection and tracing control method. However, it is more expensive, and has limited reactive power capacity. SVC, with high capacity, can compensate reactive power dynamically and smoothly, and be cheaper.In order to performance the utmost merit of APF and SVC, and evade their disadvantages, we present an APF and SVC combined system to improve power quality of Micro Grid in this article. The detail is introduced as follow: APF, with current detecting method and Deadbeat plus SVPWM current tracing control method, is set at the outlet of DG inverter, mitigating current harmonics and compensating low capacity reactive power; SVC, with voltage closed loop feedback, is set near the load, compensating reactive power and keeping voltage stable.We establish power devices and system models at Matlab-Simulink platform, and then compare the simulation results, including fundamental current value and its THD, fundamental voltage value and its THD, at the situation of no compensation, only APF compensation, APF and SVC system compensation, under stand-alone and grid-parallel mode separately. At last, the simulations show that APF and SVC combined system is satisfying on power quality improvement of Micro Grid.