Per-Phase Switching Frequency Control Method to Extend Lifespan of Three-Phase Voltage Source Inverters

This paper proposes a per-phase switching frequency control method to extend the lifespan of a three-phase voltage source inverter. The model predictive control that can intuitively deal with various control objectives is used in the proposed method. The cost function of the proposed technique consists of two terms. One is for current control, and another is for switching frequency control of each phase. Also, if necessary, a term for capacitor current RMS reduction can be added to the proposed cost function. The proposed technique reduces the switching loss of the most aged phase by reducing the number of switching operations. As a result, the reduced switching losses lower the junction temperature of the switching device. This extends the lifetime of the switching device. In addition, in the proposed technique, the capacitor current RMS, which can increase due to the per-phase switching frequency control, is effectively reduced by using the optional term for the capacitor current RMS reduction. The performances of the proposed method were verified through simulations and experiments.