EMI Reduction Method for a Single-Phase PWM Inverter by Suppressing Common-Mode Currents with Complementary Switching

With advancement of recent high-speed switching devices, PWM inverters are operated in high frequencies and often generate EMI noises due to common-mode leakage currents. There are mainly two types of leakage currents. One is inverter leakage currents due to parasitic capacitances between switching devices and heat sinks. The other is load leakage currents due to parasitic capacitances between the load and the earth. This paper proposes an elimination method which is effective both to the leakage currents in a single-phase full-bridge PWM inverter. The principle is so simple that the inverter is operated only complementarily between two arms. This eliminates neutral voltage drifts of the load by keeping the common-mode voltage zero. Furthermore parasitic capacitor currents circulate only inside the inverter body because the switching times are synchronous between the two arms. This is valid even when there are dead-times in arm switching. These effects are validated through simulation by Saber and experiment by a DSP-based system with switching frequency of 10 kHz