Advantages for embedding DC-link decoupling capacitance in high capacity power electronic converters

In large capacity power electronic equipment, large di/dt at turn-off transient will cause great voltage overshoot. Laminated busbars are used to reduce the voltage overshoot. However, the linkage between the capacitance module and the converter module has significant stray inductance, so additional decoupling capacitance will be required to absorb the energy stored in connect copper bar. Due to equipment size restriction, decoupling capacitance cannot be oversized. A suitable decoupling capacitance can help reducing the voltage overshoot and improving EMI performance. In order to find the minimum required decoupling capacitance, a design methodology for placing decoupling capacitors is presented in this paper. The impedance change at the DC-link after arranging decoupling capacitance is analyzed. Finally, simulation and experimental results are given to verify the analysis.