Modulation Strategy Comprising TCM with Frequency Limit and DPWM for Fast Switching GaN-Inverters

Wide bandgap devices in combination with TCM (for soft switching) are typically applied in inverters to achieve high power density and efficiency. This has the disadvantage of a huge current ripple during sinusoidal peak. DPWM counteracts this problem by avoiding switching actions in this section. Due to the rapidly changing voltage across the output capacitors, oscillations within the filter may occur when entering DPWM interval. This current peak can saturate the inductor and the output voltage is distorted as well. This paper proposes a method to mitigate these oscillations by bringing the capacitor voltages to the required voltage prior DPWM interval. Compared to conventional TCM modulation, lower losses result. By damping the oscillations induced by DPWM it is suitable for grid and motor applications.