| Summary: | Switch mode auxiliary circuits have been used to balance the de-link capacitor voltages of a diode-clamped five-level inverter. The use of the smps has been extended to charge- lip and discharge the four de-link capacitors. Complete diode-clamped five-level inverter operation has been implemented from inverter start-up, to link charge-up, to balanced pwm operation, to de-link discharge, and shut-down. The diode-clamped smps is used to charge and boost the two lower de-link capacitors simultaneously. Auxiliary circuit and boost converter duty cycles are used to control the de-link charge-up and discharge times. Ramped start of a controlled rectifier is used 'to limit the lowest link capacitor inrush current. Matlab and PSpice models are developed for the proposed auxiliary circuit capacitor voltage balancing and de-link charge-up and discharge techniques. Effective practical techniques are presented to bring the diode-clamped multilevel inverter on-line, ensure de-link capacitor balanced voltage operation, and take the inverter off-line to a discharged state.
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