Abstract:
DC to AC power converters/ voltage source inverters (VSI) have large number of applications including renewable energy conversion and electric vehicles. Design and performance assessment of these converters is important for Electromagnetic Compatibility (EMC) studies, conducted and radiated emission, efficiency, and hence, reliability considerations. Although the inverters are designed for a lower fundamental frequency output derived from the input DC voltage, but the semiconductor switches operate at higher frequency to achieve reduced size and cost of the filter elements. In three-phase inverters, high switching frequency reflects in terms of current ripple at the DC side as the DC bus bar experiences frequency approximately thrice the switching frequency. Therefore, it is important for any inverter to be designed in such a way that the DC bus bars has maximum current distribution and complies with EMC/EMI standards at the same time. In this work, DC bus bar design for a 20kVA three phase VSI operating at switching frequency of 10kHz is considered. In general, a high frequency VSI is designed with planar DC bus bar over the strip type busbar for higher current distribution. Further to improve the current distribution, this planar DC bus bar assembly is proposed with a ground plate sandwiched between positive and negative bus bar. The proposed DC bus bar assembly is modelled in the Solidworks and parasitics are extracted in ANSYS Q3D. Equivalent electrical circuit is built using these extracted parameters and the three-phase inverter is simulated in ANSYS Simplorer and HFSS for the conducted and radiated emissions. The analysis identifies that the proposed bus bar arrangement is superior in terms of enhanced current distribution, conducted and radiated emission minimization compared to conventional bus bar arrangement. The same is analyzed in hardware.
