应用直流调制改善水电能源基地交流电网运行特性

Application of DC Modulation to Improving Operation Characteristics of Hydropower Base Grid

直流输电具有远距离、大容量、无稳定问题等特点,适用于大型能源基地电力集中开发和外送场景。随着我国能源基地的开发建设,直流工程数量以及送电规模不断提高,直流系统的调制功能对系统稳定运行的影响日益凸显。西南地区水电资源丰富,目前通过多回特高压直流工程送电至华东地区。水电基地电网独立运行时系统阻尼特性相对较差,故障时交流系统易发生超低频振荡现象。频率控制器是直流系统附加控制之一,能够根据交流系统频率变化快速调整直流输送功率,进而改善交流系统的频率特性和阻尼特性。西南电网仿真结果表明,利用直流频率控制器能够有效改善西南电网阻尼特性,提高系统频率稳定水平。

DC transmission can transmit huge electric power over long distance without any system stability problem,thus suitable for power transmission for centralized energy base.With development of energy bases in China,number of DC transmission projects and scale of transmission capacity continuously grows,and modulation function of DC system is of greater importance for system stability.Southwest China has abundant hydro-power resources.The generated power there is transmitted to East China through several UHV DC projects.Their system damping characteristics are relatively poor when the hydro-based power grid operates in isolated manner,and the AC system is vulnerable and prone to ultra-low frequency oscillation.Frequency controller is one of additional controls in DC system,able to quickly adjust DC transmission power according to frequency disturbance of the AC system,thus improving the frequency and damping characteristics of the AC system.Simulation results of Southwest Power Grid show that frequency controller can effectively improve damping characteristics and frequency stability level of Southwest AC system.