New current source inverters with DC-side commutation and load-side energy recovery circuit

Two all-thyristor-type current source inverters (CSIs) with DC-side commutation and load-side energy recovery are proposed to reduce the device voltage stress and to eliminate the commutation failure problems. The inverter circuits are analyzed approximately to give guidelines for commutation circuit design and are compared with the autosequentially commutated inverter (ASCI). The inverters overcome most of the drawbacks of conventional CSIs-high device voltage stress, low operating frequency range, large commutation capacitance-by using a simultaneous recovery and commutation concept. The CSIs use only one commutation capacitor and can be built with considerably low cost. The commutation energies are temporarily stored in a large DC capacitor and recovered to the load side, which makes the device voltage stress low and the efficiency high. The operation of the proposed inverters is verified through computer simulation. Experimental results are shown for a 5-hp induction motor drive