Study on mechanism and characteristics of HVDC system with the novel shunt capacitor commutated converters

摘要

The application of power electronics in HVDC systems inevitably lead to various power quality problems, such as harmonic pollution, reactive loss and commutation failure, etc. To solve these issues, this paper proposes a novel shunt capacitor commutated converters (SCCC) to figure them out. The topology can be described as follows, the shunt capacitors are installed at the altering current (ac) bus between the valve winding of converter transformers and the converters, it can replaces the conventional HVDC system with line commutated converters (LCC) where the harmonic filters and shunt capacitors are installed at the ac grid side. Firstly, the characteristics and operating mechanism of the new HVDC system with SCCC are analyzed, and then, the harmonic equivalent model is established. Moreover, the mathematical model for the SCCC-HVDC system is presented. The feasibility of the proposed new topology is validated by simulation results. It manifests that the shunt capacitors not only greatly absorbs the high-order harmonic but also eliminates the commutation angle μ absolutely, hence, the commutation ability can be enhanced greatly. Besides, it also presents good filtering and reactive power compensating performances to public networks.