The Fundamental Research On Digital Simulation Of HVDC Light Technology

HVDC Light is a new-type HVDC based on Voltage Sourced Converters (VSC) Technology. As using IGBT in VSC, the current will be cut off easily; Also the pulse width-modulation (PWM) technology can be used for passive inversion. As a result, supplying to passive load with HVDC Light has being come true. Different from conventional HVDC, PWM control is adopted by VSC HVDC. 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. Hereby it is able to regulate the power flow conveniently.On the other hand, with the development of renewable generation and distributed generation, there is a need to feed these renewable generations to network by proper conversion and transmission, and VSC HVDC is the one exactly.In this paper, the control method of HVDC Light and its application with wind farm will be mostly studied. Firstly, the steady and simple physical model of VSC HVDC system are established. Then the structure of control system and the basic control method are introduced for designing VSC controllers. The VSC controller is based on PI control strategy. For validating the VSC controller, the PSCAD/EMTDC simulation models are established. It is demonstrated by simulation results that the controller is convenient, flexible and efficient; moreover, the power flow and the stability of HVDC Light system can be controlled easily, all the basic control method can be achieved by this controller. At last, wind farm connecting with power system grid based on VSC HVDC technology is introduced,and then the paper analyses the influence of wind farm on the stability of power system.