The Research On VSC-HVDC System And Its Application In Isolated Power Supply Black Start

In recent years, experts and scholars both internal and abroad are mainly make a series ofresearch and discussion on VSC-HVDC converter topology, mathematical model, technicalcharacteristics, control strategy and system protection, and the entire process that using theVSC-HVDC as the power of the black start to complete island system from blackout torestore normal operation, less work have done both in internal and abroad. In the process ofblack start, the most main questions are the frequency, voltage and stability of the system; andat the beginning of the black start, it is essentially to use the VSC-HVDC supply power topassive network. Based on above and on the basis of previous studies, the VSC double-loopcontroller is designed. At the same time,in order to make the VSC-HVDC has good voltagefrequency characteristic in the process of black start, the VSC-HVDC inverter side in thispaper used to determine voltage/frequency control, and in the PSCAD software platform toverify the effectiveness of the control strategy. When the ac system have a serious fault andVSC should exit the running, the traditional method is to directly lockout of VSC, it willproduce transient process may damage to equipment. This paper proposes a kind of active/reactive power shut off slope control strategy, to smooth their exit VSC power transmission,to realize self-protection of VSC, and maintain a "hot standby". In addition, this paper alsostudied on the VSC start-up mode, to suppress the operation overvoltage in the process ofblack start start-up. On the basis of above work, this paper use of VSC-HVDC link activenetwork as the islands of the starting power of black start, according to the power of islandresources, load distribution, network frame structure characteristics, and fully consider theblack start plan formulation principle, designs the network recovery steps,and simulate thewhole process of black start. The simulation results verified the effectiveness of the adoptedcontrol strategy and the correctness of the black start scheme in the process of black start, alsoverified the VSC-HVDC has good black start capability, is an ideal black start power supply.