Online Optimal Pulsewidth Modulation (OPWM)

Online Optimal Pulsewidth Modulation (OPWM) for a Multilevel Inverter explains a control scheme in controlling a 5-level Cascaded H-bridge Multilevel Inverter (CHMI) output voltage based on the OPWM switching strategies. For better CHMI output voltage magnitude control resolution, a curve fitting technique (CFT) for online computation of the OPWM switching angles is presented. Focus is given on the CFT and the multilevel control design aspect of the control scheme for the CHMI. This control scheme is generally suitable for AC power supply applications that do not involve variations in the multilevel inverter operating frequency. In addition, its suitability is also identified for applications that require high quality output voltage but at the same time do not allow increase in the multilevel inverter power devices switching frequency. This may be due to the technological limits of the power devices employed for high voltage applications or certain environmental condition. To show the feasibility of the control scheme, results of a simulation study and experimental work on a 5-level CHMI operation are presented.