A Simple Carrier-Based Implementation for a General 3-level Inverter Using Nearest Three Space Vector PWM Approach

This paper proposes a novel carrier-based implementation strategy of a standard space-vector pulse-width modulation (SVPWM) technique of three-phase (3ϕ) three-level inverter (TLI). To synthesize the reference voltage vector, the selected SVPWM technique uses nearest three voltage space-vectors in order to reduce output voltage THD and partially balance the neutral point voltage. The implementation complexity of this SVPWM technique is reduced by introducing the concept of common-mode signal in duty-ratio calculation of 3ϕ-TLI. Following the modulation strategy of the selected SVPWM technique, general expression of common-mode signal has been derived in terms of maximum, middle and minimum values of input 3ϕ modulation signals. It is shown in the paper that six duty ratios of 3ϕ-TLI can be directly calculated from the input 3ϕ modulation signals and the derived common-mode signal. Thus, calculation-intensive steps of SVPWM technique, like, identification of reference voltage vector location, calculation of dwell-times of individual vectors, are avoided. The proposed algorithm is validated through simulation in MATLAB and experiment on 1.5 kW hardware prototype.