A black start scheme based on modular multilevel control-high voltage direct current

Abstract

Modern society's need for power and its dependence on power sources is increasing with its development. As a result the consequences of blackout accidents have become more serious. At present, only three sources can be regarded as black-start power sources, namely Line Commutate Converter-High Voltage Direct Current (LCC-HVDC), Voltage Source Converter-High Voltage Direct Current (VSC-HVDC), and microgrids. The potential of these three sources has already been demonstrated. Lately, VSC-HVDC primarily uses the Modular Multilevel Converter (MMC) topology structure, also known as MMC-HVDC. Some domestic and foreign papers have also proposed using VSC-HVDC as a black-start power source for large power failures. However, most of these studies have analyzed only 2-level or 3-level VSC-HVDC topologies and there is no MMC topology for VSC-HVDC analysis. Therefore, the conclusion that VSC-HVDC can be used as black-start power source cannot be held true for a MMC-HVDC structures. To understand the characteristics of MMC-HVDC as a black-start power source, it is necessary to analyze the MMC-HVDC converter and do a comprehensive assessment of its performance as a black-start power source. This study analyzes the feasibility of MMC-HVDC as a start power source for black start from with regards to three aspects, namely the working principle, control strategy, and implementation scheme. We designed a corresponding MMC-HVDC control strategy depending upon the analysis result. Moreover, a complete power grid restoration process is also designed according to the black-start scheme principle, which is based on the theory of MMC-HVDC as a black start power source. Finally, the whole black start process is performed in PSCAD/EMTDC. The simulation results show that the voltage and frequency of system are maintained in a steady range during the black start realization process and the validity of MMC-HVDC as a black start power source is also verified.