A novel dead time compensation circuit for improved PWM inverter operation in brushless motor drive systems for electric vehicles

In this paper, a novel circuit design for elimination of the effects of PWM inverter blanking in three phase brushless motor drive (BLMD) operation for electric vehicle propulsion is presented. This simplified circuit implements two-way clamping of the carrier-switching signal, during PWM inverter operation, which counter balances the presence of power transistor turn-on delay necessary for the prevention of current `shoot-through´ faults. This method is effective on all three phases simultaneously and avoids the need for separate PWM dead time balance on each phase. A theoretical analysis based on the modulated Fourier series representation for PWM is provided for validation purposes which justifies the effectiveness of the method in counteracting transistor blanking. BLMD simulation waveforms of the stator winding current flow and torque delivery are presented for concept validation and accuracy when compared with similar traces for ideal PWM inverter behaviour without turn-on delay.