Inner phase angle control of voltage source converter in high power applications

Voltage source converters for high-power applications like HVDC and SVC will encourage the use of low commutation frequency which restricts the attainable control performance. In spite of the low switching frequency the control system must be fast-acting in order to handle start-up and different fault conditions. A control strategy that brings the converter into stationary state as fast as possible is required. A control method for a voltage source converter based on measured converter flux and DC voltage is outlined and exemplified in a six-pulse unit. The time-to-next-commutation is calculated in real time so that the converter flux is guided in minimum time from an arbitrary point in the flux plane toward the stationary orbit