New optimum modulation of three-phase ZVS triangular current mode GaN inverter ensuring limited switching frequency variation

In three-phase pulse width modulation inverters with an LC output filter, switching losses can be reduced by increasing the current ripple in the inductor until a current zero crossing occurs between the two switching instances of a bridge leg. A disadvantage of this triangular current mode (TCM) operation is the varying switching frequency. This paper presents new modulation methods where the current ripple amplitude is adjusted and a common-mode voltage is introduced in order to limit the switching frequency variation. Moreover, the possibility of increasing the efficiency and minimizing the filter volume are investigated. Numerical optimization results are presented for a 2.5 kW inverter with 400 V DC link voltage as a case study.