含VSC_HVDC的交直流混合系统稳定性研究

发布时间：2018-05-19 23:42

本文选题：电压源换流器 + 系统稳定性　；参考：《南京理工大学》2014年硕士论文

【摘要】：随着现代电力系统规模的逐渐增大,网络日趋复杂,远距离、大容量的输电与各个大区域之间的电网进行异步互联,城市配电网的发展与环境保护等问题将会日益严重。而采用电压源换流器的柔性直流输电技术,可以进行无源逆变,不存在换相失败,故在交直流混合输电系统中不存在因换相失败而引起输送功率中断威胁整个系统稳定性。VSC换流器能稳定独立控制线路传输的有功、无功功率,类似静止同步补偿器提供无功补偿,来向交流系统提供紧急无功支援。因此对VSC-HVDC的研究将对改善交直流混合配电网电能质量并提高其供电灵活性、可靠性等方面有着重要意义。针对传统直流输电的不足,采用了多重化、三层次的结构设计VSC-HVDC的控制体系。建立了含VSC-HVDC的交直流系统的数学模型,利用双环PI调节的控制策略设计了内环电流控制器与外环控制器,解耦后的dq轴电流可以控制系统的有功与无功分量,并利用电压斜率控制改进外环控制器。基于MATLAB平台搭建了柔性直流输电仿真模型,仿真研究了两端有源网络的功率传输和向无源网络供电的工程状况。结果表明：设计的系统可以对有功与无功功率进行准确、独立控制且两个换流站之间不需要通信。电网电压跌落过大时VSC阀的过电流保护能控制换流站传输功率降额运行,直流电压斜率控制器可以抑制故障下电压波动。在交直流混合网络中,对电力系统稳定器进行了参数优化,并利用VSC的无功补偿能力提高混合系统稳定性。结果表明：参数优化后发电机的转速与功角能迅速稳定,同时联络线上的功率摇摆对直流输电线路没有影响,VSC能稳定控制直流传输的功率,若利用柔性直流异步互联可以根除系统的低频振荡。
[Abstract]:With the increasing scale of modern power system, the network is becoming more and more complex, long-distance, large capacity of transmission and each large area of the power grid asynchronous interconnection, the development of urban distribution network and environmental protection will become increasingly serious. The flexible DC transmission technology using voltage source converter can carry out passive inverter, and there is no commutation failure. Therefore, in AC-DC hybrid transmission system, there is no transmission power interruption caused by commutation failure, which threatens the stability of the whole system. VSC converter can stabilize the active power and reactive power of independent control line transmission. A static synchronous compensator provides reactive power compensation to provide emergency reactive power support to AC systems. Therefore, the research on VSC-HVDC will be of great significance in improving the power quality of AC / DC hybrid distribution network and improving its power supply flexibility and reliability. Aiming at the deficiency of traditional DC transmission, the control system of VSC-HVDC is designed with multi-level and three-level structure. The mathematical model of AC / DC system with VSC-HVDC is established. The inner loop current controller and the outer loop controller are designed by using the control strategy of double loop Pi regulation. The decoupled dq axis current can control the active and reactive power components of the system. The outer loop controller is improved by voltage slope control. The simulation model of flexible direct current transmission is built based on MATLAB platform. The power transmission and power supply to passive network are simulated and studied. The results show that the designed system can control the active and reactive power accurately and independently and there is no need for communication between the two converter stations. The overcurrent protection of VSC valve can control the power drop operation of converter station when the voltage drop is too large. The DC voltage slope controller can restrain the voltage fluctuation under the fault. The parameters of power system stabilizer are optimized in AC / DC hybrid network, and the stability of hybrid system is improved by using the reactive power compensation ability of VSC. The results show that the rotation speed and power angle of the generator can be quickly stabilized after parameter optimization, and the power swing on the tie-line has no effect on the power of HVDC transmission line, and the VSC can control the power of DC transmission stably. If the flexible DC asynchronous interconnection is used, the low frequency oscillation of the system can be eliminated.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM721.3

【参考文献】