Linearly controllable boost voltages from tri-level PWM current-source inverter

The peak line-to-line inverter ac voltage, in general, cannot exceed the supply dc voltage and transformers have to be used when voltage step-up is required. This paper describes how the necessity of using a Tri-Level PWM strategy in the Current Source Inverter can be turned into an advantage by producing a voltage boost so that transformers are no longer required. During the frequent occurrence of the 'shoot-through' states, which is the characteristic of the Tri-Level PWM-controlled inverter, magnetic energy builds up in the dc link inductor. At the end of these periods, the [L.sub.dc]d[I.sub.dc]/dt voltage across the inductor augments the inverter output voltage in the same way as in the basic boost type dc/dc converter. The paper describes the circuitry required to ensure linear control. Analytical, simulation, and experimental results are given. Applications are found in all instances where the ac voltage is higher than the available supply dc voltage.