Impacts of Grid Voltage Harmonics Amplitude and Phase Angle Values on Power Converters in Distribution Networks

Motor drive systems based on diode-rectifier are utilised in many industrial and commercial applications due to their cost-effectiveness and simple topology. However, these diode rectifier-based systems can be affected by power quality and harmonics in distribution networks. Thus, this paper investigates the impact of grid voltage harmonics on the operation of power converters with three-phase diode rectifier using mathematical formulation of the drive voltage and current harmonics based on grid voltage harmonics. Simulation analysis and practical tests have been then carried out to validate the mathematical equations and the impact of grid voltage harmonics on the power converter harmonics. The results illustrate that even a small amount of grid voltage harmonics (around 4%) could significantly impact the input current harmonic contents of the three-phase diode rectifier. It is also shown that the phase-angle of grid voltage harmonics plays a crucial role to improve or deteriorate the input current harmonics of the power converters. In the next step, the optimum condition of grid voltage harmonics to minimise the input current harmonics has been evaluated and verified based on different grid codes. Finally, a harmonic mitigation technique in multi-drive systems using Electronic Inductor is proposed to mitigate the current harmonics at the PCC.