Power reversal strategy through DC current reversal using a new bidirectional LCC HVDC system

This paper presents a new Line-Commutated Converter (LCC) High-Voltage Direct Current (HVDC) topology with bidirectional current capability. Based on the proposed topology, this paper further develops a control strategy that achieves power reversal without reversing the DC voltage polarity, different from the power reversal strategy in conventional LCC HVDC that is based on reversing the DC voltage polarity. This distinguished feature of the proposed method significantly improves the applicability of LCC HVDC for projects where DC voltage polarity reversal is undesirable. Simulation results of the proposed method using the CIGRE benchmark system and a modified 39-bus system are presented to validate the performance of the proposed method. All simulations are carried out using the Real-Time Digital Simulator (RTDS). Comparison with conventional power reversal method is made. Cost implications and various aspects of practical implementation of the proposed method are also discussed. The proposed solution utilizing antiparallel thyristor pairs can achieve power reversal by reversing the direction of DC current. It removes the fundamental operational constraint of conventional LCC HVDC.