A simple DC-link pre-charging method for three-phase voltage source inverters

How to start a voltage source inverter (VSI) is an often overlooked topic. Many papers focus on control algorithms, assuming the inverter is already in operation. Besides inrush current, pre-charging of the DC-link capacitor is one of the most important, since too low voltage may cause the control algorithm to fail during startup. This paper presents a DC-link pre-charge method without any additional pre-charge components. The method can easily be integrated in an existing space vector modulated control system with minimal modifications. The method can also be applied for startup of sensorless control VSI. Simulations and experimental results are presented.