On the Use of Pulse Height Modulation for Harmonic Cancellation in a Six-Level Inverter Topology

This paper deals with harmonics cancellation using pulse height modulation (PHM). This technique allows simultaneous optimization of the total harmonic distortion (THD) rate and the number of power switches. This leads to substantial reduction of the power switching losses as compared with PWM. A novel six-level inverter model is presented with three-phase output voltages having similar symmetry properties to a pure three-phase sinusoidal system. The proposed method allows canceling all even-order harmonics and integer multiples of the thirdorder harmonic. Switching angles and input dc voltage levels are determined so as to cancel most of the successive low-order harmonics (the most harmful to the network) starting from rank 2, allowing to shift the first nonzero harmonic far away from the fundamental. For 12 switching states per period, PHM allows to cancel harmonics from rank 2 to 10 with lower THD. A comparative study of the obtained output voltage and current shows their compliance with IEEE 519-1992 and IEC 61000-3-12 standards.