Study On The Mitigation Method Of Harmonic Current In Building Electric System

With the development of building automation system, the electronic equipments used in building are increasing with years. These equipments generate a large amount of harmonic current in the building electric system, and the largest component is the triple harmonic current with zero-sequence characteristic. The triple harmonic currents in three-phase will add together in the neutral line, this will cause incipient fault and economy losses.The tuned harmonic filter in series with the neutral line is an effective method for zero-sequence harmonic mitigation. However, the series tuned filter not only has the de-tuning problem but also inject fundamental impedance into the neutral line. In order to mitigate those negative effects, a continuous auto-tuning zero-sequence harmonic filter based on an active reactor was presented in this paperThe independent control method of fundamental reactance and third harmonic reactance of the active reactor based on magnetic flux compensation was presented, and the simulation system for the active reactor was established. Simulation results show the feasibility of the active reactor. The simulation system of the triple-harmonic filter with continuous auto-tuning function was further designed, and the simulation results show that this filter can suppress triple-harmonic current, compensate fundamental reactance, and adapt variation of filter parameter.The experimental system of the triple-harmonic tuning filter based on DSP controller and also a new detection method of single-order harmonic current was developed. The experiment at three different load conditions was carried out, and the experiment results show that the auto-tuning control system can effectively improve the filtering performance of the tuned filter.