Compare the Efficiency of the Active Filter and Active Rectifier to Reduce Harmonics and Compensate the Reactive Power in Frequency Controlled Electric Drive Systems

Currently, frequency converters using diode rectifiers generate a lot of harmonics, which adversely affect the quality of the grid and the durability of electrical equipment. On the other hand, asynchronous motors that consume a large amount of reactive power of the source cause losses on the grid and reduce the power factor at the input of the converter. Therefore, researching the method of using active filters at the input of frequency converters with diode rectifiers will reduce current harmonics and compensate reactive power for the grid. The active filter will produce harmonics with a phase angle inversely to the phase angle of the harmonics generated by the load, which will suppress most high-order harmonics. The frequency converters use active rectifiers with a direct power control method so that the reactive power q = 0 ensures the standard sine current at the input, the power factor equals 1, there is the stability of a DC voltage and the power is exchanged in two directions between the motor and the grid. The paper compares the effectiveness of the two methods when considering the load as three asynchronous motors that work in different modes such as motor mode and generator mode. The research results are verified by Matlab & Simulink software.