Study On Current Harmonics From AC Side Of SRD System

The SRD(Switched Reluctance Driver), developed in the 1980's, is a new type of speed control system. It has been applied to the field of industry speed control, servo, household electrical appliance and so on. SRD is supplied by AC-DC rectifier, and the current harmonics caused during the operation will affect the power quality of the power networks. In the paper, a SRD simulation model is constructed to analyze the regularity of the current harmonics varying with the operating parameter in the side of AC power supply. Experiment has been performed on a SRD and the results show that the conclusions obtained from the digital simulation is valid.The basic construction and working principle is introduced firstly, and the current expression of SRD in the side of AC power supply is deduced based on simplifying the SRD into a three phase rectifying circuit of resistance-capacitance filtering, finally the harmonic component of the power supply current is analyzed by using Fourier transform.The matlab/simulink is selected as simulation tool for SRD modeling, a 6/4 pole Matlab/simulink simulation model of SRD is constructed. Base on the analysis of the structure and working principle of SRM(Switched Reluctance Motor), a 12/8 pole SRM model rebuilt from 6/4 pole SRM model is presented. The validity of the model is verified in simulating and experimenting. The digital simulation of the current harmonics in the side of AC power supply is performed based on the simulation model. By analyzing the relationship between harmonic components and the rotating speed of electric machine, power and filtering capacitance, some conclusions have been obtained as follows: first, the harmonics is mainly related to the loads and is independent of the rotating speed of electric machines, but higher load leads to the lower total harmonics dis(THD),. Second, it is relatively complex when filter capacitance varying; the harmonics decrease when the capacitance increase at most circumstance.The filtering effect of reactor in series with the SRD DC busbar is simulated using SRD simulation model, conclusion obtained that the smoothing reactor is more effective in filtering the lower order harmonics than the higher order harmonics.Finally, the power supply harmonics of SRD, which is composed of a three phase 12/8 pole SRM with 37kW rated power and 1500r/min rated rotating speed and SRD10132 controller, is practically tested on the SRD testing platform designed by Shandong Kehui Electric Co. Ltd. Comparing with the simulation results, the relationship of the harmonic components varying with the power, rotating speed, filtering capacitance and smoothing reactor is almost the same. Accordingly, the validity of the simulation results is verified.