Study On Microgrid Power Quality Conditioner Based On Energy Storage Of Super-capacitor

Microgrid is a small scale power generation system which is constituted by a large number of renewable energy and loads, and it has the ability to withstand the big volatility of renewable energy power generation so as to make full use of renewable energy power generation's efficiency. In the dissertation, the super-capacitor energy storage system is introduced into microgrid, and the power quality problems which are caused by harmonic pollution, lack of active and reactive power in microgrid has been researched, finally, the dissertation proposes a microgrid power quality device to eliminate these power quality problems. The main contents are as follows:Firstly, the dissertation summarizes the power quality problems which exist in microgrid, and researches the compensation and governance method for every power quality problems in microgrid. On this basis, proposing a power quality conditioner which based on super-capacitor energy storage system to improve the power quality problems of microgrid.Secondly, the dissertation analyses the main circuit structure of microgrid power quality conditioner based on super-capacitor energy storage system, establishes the power quality conditioner's mathematical model and studies its working principle. Meanwhile, according to different power quality problems may appear in microgrid, a power quality compensation flow chart is designed, and the power quality conditioner could follow the flow chart to compensate the power quality problems when it appeared in the microgrid, so as to ensure the microgrid work more stable.Thirdly, in order to accurately compensate the harmonics, reactive and active currents, the key is to detect these power quality problems. When the power quality conditioner's detection point and compensation point are inconsistent, the compensative effect of power quality conditioner is also not effectively, so an improved ip-iq current detecting method of harmonics, active and reactive power is proposed. The improved ip-iq current detecting method of harmonics, reactive power can accurately detect the currents fluctuations of harmonics, reactive and active power in microgrid, and when the power quality of microgrid exceeds a certain threshold, the power quality conditioner could work in a timely manner to compensate these power quality problems. There are many power control devices in power quality conditioner, such as static var compensator, dynamic voltage restorer, active power filter and so on, but they can only compensate some single power quality problem, and the compensate effect is ineffective when the power quality problems is complex. The microgrid power quality conditioner based on energy storage of super-capacitor proposed by dissertation could compensate various power quality problems, such as harmonics, voltage fluctuations and reactive power problems. Combined with the super-capacitor energy storage system, the power quality conditioner could accurately compensate the active power inadequate of microgrid simultaneously.Finally, a small microgrid simulation model and microgrid power quality conditioner's simulation model is set up based on the analysis and design above. With the combination of theoretical analysis and simulation experiment, the correctness and reliability of topology and control strategy are verified.