随着大功率可关断电力电子器件和PWM调制技术的发展，基于电压源换流器VSC的高压直流输电(简称VSC-HVDC)技术在世界范围内已经得到了成功的应用，较传统HVDC有明显优势。VSC-HVDC系统保证有功功率平衡传输的同时，还能独立调节无功功率，可向弱交流系统及无源网络供电，由于VSC采用了全控器件，使得VSC-HVDC技术具有广阔的应用前景。 在文章中，首先介绍了以二极管箝位型三电平VSC为基础的高压直流输电系统工作原理和数学模型，以及二极管箝位型三电平VSC-HVDC有功及无功独立控制原理。其次在传统换流站级控制系统基础上，介绍了两端二极管箝位型三电平VSC-HVDC换流站级控制的改进方法，最后详细列出了向有源网络供电系统在采用改进后换流站级控制方法时受到不同扰动下的MATLAB仿真结果图。仿真结果表明，改进后换流站级控制器具有良好的控制效果，对各种扰动都具有很快的响应速度和很好的稳定性。

With the development of high power turn-off power electronic components and PWM technique，Voltage Source Converter based High Voltage Direct Current(VSC-HVDC) has been realized successfully in the world, and it is superior to the traditional HVDC. Because of using full controlled components，the VSC-HVDC system not only can ensure the balancing of active power transmission，but also adjust reactive power independently. It also can supply power to weak AC system and passive network，which made it have the broad application prospects. The mathematical model and working principle for diode Neutral-Point-Clamped (NPC) three-level VSC based HVDC system is presented in this thesis. Based on this model，the fundamental principles of the active and reactive power control has been also presented，and the method of a improvement control system based on traditional double closed loop control system has been stated. MATLAB simulation result plots and the analysis are given. This practical operation shows that this improvement controller has good control effect and the system gets high response speed and quite good stability.