Harmonic mitigation technique for the power quality improvement of DC motor drives

A three phase six pulse controlled bridge rectifier with adjustable value of injection third harmonic current is used to control DC drive. In order to improve the power quality of both AC and DC sides of the system the injection circuit parameters have to be varied according to drive loading operating conditions. Therefore the values of injection circuit parameters depend on the firing angle (alpha). In order to reduce the complicity of the injection circuit technique, it is proposed to choose an optimum value of injection circuit parameters to fulfill the range of (0⁰lesalphales180). The injection capacitor (C_j) value is adjusted to obtain minimum current distortion (THD) and to improve the effective input power factor (PF) on the ac side of the converter, for both rectification and inversion modes. A neural network (NN) technique is used to control speed of the dc motor in the rectification mode and to control DC power flow from DC side of the rectifier to the AC side in the inversion mode. Simulation results shows that the current injection circuit are active and reliable in the rectification and inversion modes which are verified experimentally at sample value of the injection circuit parameters.