Operation and Control Design of New Three-phase Inverters with Reduced Number of Switches

DC/AC inverter topologies having reduced numbers of switches to reduce costs, total inverter size and switching losses have previously been proposed. In addition, these topologies reduce the likelihood of semiconductor switch damage, and have lower common-mode currents. This paper proposes new designs for inverters with reduced switch numbers. For three-phase systems, the proposed inverters use four switches instead of the six used in the traditional three-phase Voltage Source Inverter (VSI). Compared to the traditional Four-Switch Three-Phase (FSTP) inverter, the proposed FSTP inverters improve the voltage utilisation factor of the input dc supply, without the need for triplen injection. Sliding-mode control is used to demonstrate the dynamic response and robustness of the inverters. Also the paper presents new single-phase inverters with two switches instead of the four used in the traditional VSI. The capability of suppressing the 2nd order current harmonic from the input dc side is discussed. The basic structures of the proposed inverters and their operation, switch ratings, controller design with supporting mathematical equations, and MATLAB/SIMULINK results are presented. Practical results, based on laboratory prototype circuitry controlled using a Texas Instruments TMSF280335 DSP, are presented to demonstrate the design flexibility and operation of the proposed topologies.