DC power interconnection using series capacitors and thyristor-based phase controllers

The objective of this work is to discuss the feasibility of diode rectifiers using series capacitors and thyristor-based phase controllers such as triacs for the application to the DC power interconnection of the variable-speed wind turbine generators. In this work, the authors use a wound-rotor induction generator excited by the constant direct current to simulate a permanent magnet synchronous generator. Since the series capacitor compensates the synchronous reactance, the DC voltage of the diode rectifier can keep higher voltage even when the direct current is increased. Using the firing angle control of the triac, the DC voltage can be controlled by both leading and lagging power factors of the synchronous generator and keep a constant voltage even when the generator speed randomly varies. The required voltage capacities of the triac and the series capacitor can be reduced to almost 30% of the rated DC voltage for the variable-speed synchronous generator operation. Therefore the diode rectifier using the series capacitors and the triac becomes one of the feasible converter topologies for the DC power interconnection of the variable-speed wind turbine generators.