摘要
针对多端柔性直流输电系统(voltage source converter multi-terminal DC,VSC-MTDC)具有强非线性和不确定性的特点,提出了一种新型基于指数趋近律的滑模电流控制策略。直流输电系统换流站采用直接电流控制时的内环电流PI控制环节用滑模电流控制代替,与传统双闭环PI控制相比减少了一个内环PI控制环节,简化了系统的参数调节过程。在旋转坐标系下构造了以内环d轴电流、q轴电流误差为滑模面的滑模变结构控制器,并结合李雅普诺夫函数对控制系统的全局稳定性进行了分析,实现了在换流站因故障退出运行时,系统能保证功率的快速调节,在交流系统等效阻抗发生变化时,系统仍能维持直流电压的稳定。最后在PSCAD/EMTDC中搭建了大规模海上风电场多端直流输电系统模型,将所提控制策略与传统PI控制策略进行了对比,仿真结果表明所提控制策略具有良好的动态性能和稳态性能。
In view of strong nonlinearity and uncertainty of VSC-MTDC systems, a novel sliding-mode current control strategy based on exponential reaching law is proposed. The inner loop current proportional integral （PI） control is replaced by a sliding mode current control when the direct current control is used in HVDC converter stations, which reduces a PI controller compared to traditional double loop PI control and simplifies the parameter adjustment process of the system. A sliding-mode variable structure controller is estab- lished in which the errors of the d-axis current and q-axis current in inner loop are selected as a hyperplane in the rotating coordinate system, and the global stability of the control system is analyzed via Lyapunov function, the fast adjustment of power can be ensured when the converter station switches off because of fault, the stability of DC voltage can be maintained when the equivalent impedance of AC system changes. Finally, a multi-terminal HVDC transmission system connected to large offshore wind farms is built in PSCAD/EMTDC, the proposed control strategy is compared with traditional PI control strategy, and simulation results indicate that the proposed control strategy possesses good dynamic and steady state performances.
出处
《南方电网技术》
北大核心
2017年第7期19-25,共7页
Southern Power System Technology
基金
广东电网公司科技项目(GDKJQQ20161198)~~
