Power Control And Flexible Connect Strategy Of HVDC Light

HVDC Light is a kind of new DC transmission technology developed from the traditional HVDC, with Voltage Source Converter based on turn-off power electronic components as main components. Different from conventional HVDC, PWM control is adopted by HVDC Light. With PWM it is possible to create any phase or amplitude (up to a certain limit) by changing the PWM pattern, which can be done almost instantaneous. Here by it is able to regulate the power flow conveniently. Presently, converter stations of HVDC Light are available for powers up 400MW. With the development of power electronics, the transmission capacity of HVDC Light will be increased, and HVDC Light must have widely application space. In this paper, the operation principle and technological characteristic of HVDC light are analysed. The steady state model of HVDC Light is set up for the cases of supplying power to active and passive systems respectively. The correlations between control variables and controlled variables are figured out according to this model, then a PID controller to HVDC Light system is designed based on dying oscillation technique. The feasibility of PID controller is verified by the simulation results of a HVDC Light. The problems of HVDC applied in connecting and the feasibility of HVDC Light applied in connecting is analysised. The protection strategy of HVDC Light has been proposed when the AC network have faults. The control strategy of HVDC Light has been proposed too when the no-load long line is started up. Corresponding controllers have been designed based on PID control principle. The self-protection is carried on and DC voltage is keeped on. The system is started up and it avoids the severe operation overvoltage of switching on the no-load long line. At last, the simulations of self-protection and started up of HVDC Light have been carried on by the PSCAD/EMTDC software.