环网式三端直流输电系统及直流断路器应用的分析与仿真

Analysis and Simulation of Ring-Shaped Three-Terminal HVDC Power Transmission System and Application of DC Circuit Breakers

分析了多端直流输电系统的基本原理,利用PSCAD/EMTDC软件建立了多端直流输电系统仿真模型,并建立了含直流断路器的多环网式多端直流输电系统模型,通过仿真研究了直流断路器开断直流输电线路的过程,分析直流断路器在环网式多端直流输电系统中的作用。对直流断路器切除环网式三端直流输电系统一条输电线路的过程及切除故障换流站分别进行了仿真分析。仿真结果表明,当利用直流断路器切除环网式多端直流输电系统的一条输电线路时,输电线路的电流重新分配,能保证功率输送的连续性。在这种情况下,对各个换流站输出或输入的功率影响不大,对与直流系统连接的交流输电网影响很小。当切除故障换流站后,该系统最大限度地保持功率传输及电流的有效分配,保持稳定运行。

Basic principles of multi-terminal direct current （MTDC） power transmission system are analyzed, and utilizing PSCAD/EMTDC software a model of MTDC power transmission system and a model of multi ring-shaped MTDC power transmission system containing DC circuit breakers are built. The process of switching off a DC transmission line by DC circuit breakers is simulated and researched, and the action of DC circuit breakers in multi ring-shaped MTDC transmission system is analyzed. The process of switching off one of transmission lines as well as the process of switching off a faulty converter station in three-terminal DC transmission system by DC circuit breakers are simulated respectively. Simulation results show that when one of DC transmission line in ring-shaped MTDC transmission system is switched off by DC circuit breakers, the currents in DC transmission lines are redistributed to ensure the continuity of power transmission. Under such a condition, the affection on input or output power of each converter station is not notable, and the affection on AC power transmission network connected to MTDC transmission system is slight too. After the faulty converter station is switched off, the three-terminal DC transmission system can sustain the power transmission to the hilt and effective distribution of currents, thus the stable operation of the DC system can be maintained.