Multi-level voltage reinjection-a new concept in high voltage source conversion

A voltage source converter is proposed, in which the multi-step output voltage waveform is achieved by the reinjection of different DC voltage levels via the common neutral point of the converter bridges. The number of clamping switches are substantially reduced, permitting the use of higher level numbers to achieve very low distortion without the assistance of PWM. The reinjection concept causes the voltage across the main bridges to vary in step waveforms and the commutations in the main valves to occur at zero voltage, with considerably reduced dynamic voltage stress and switching losses.