Switched-DC Inverter Based Variable Switching Frequency DPWM Technique for Spreading the Harmonic Energy With Reduced Current THD

Bus-clamping PWM (BCPWM) methods reduce the inverter switching loss compared to conventional space vector PWM. Conventional BCPWM techniques when employed in AC drives leads to concentrated frequency spectrum which can lead to vibration and acoustic noise. This paper proposes a variable switching frequency-based Discontinuous PWM (DPWM) technique combined with a modified inverter topology to achieve a spread in the harmonic energy spectrum, along with reduced stator current distortion in a Permanent Magnet Synchronous Motor drive. A comprehensive analysis of the current ripple patterns for conventional bus-clamping sequences is conducted to develop the switching logic. The proposed logic uses a trapezoidally varying sub-cycle sampling period to spread the stator current spectrum. This strategy results in a 32<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> reduction in stator current Total Harmonic Distortion (THD) and a 42<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> reduction in dominant harmonics compared to conventional bus-clamped PWM at low speeds, demonstrating its effectiveness as a promising variable switching frequency approach. The harmonic performance of the suggested technique is verified experimentally using a 1.07 kW PMSM drive operated under field-oriented control.