静止无功发生器无功电流的滑模变结构控制

Sliding Mode Variable Structure Control of ASVG Reactive Current

为提高静止无功发生器(ASVG)的控制效果,针对ASVG无功电流内环控制系统,提出了一种无功电流滑模变结构控制方法。根据ASVG的装置级非线性数学模型,建立了系统无功补偿电流的控制模型,采用反馈线性化方法将系统线性化。在此基础上,应用极点配置法设计出滑动模态超平面,并在考虑外界扰动条件下完成了变结构控制规律的设计。数字仿真结果表明,设计的无功电流滑模变结构控制器较传统的PID控制器在无功电流的追踪能力上具有更快的响应速度,对系统摄动和外加干扰具有较强的鲁棒性。

Voltage-source-converter-based Flexible AC Transmission System （FACTS） plays an important role in modern high voltage transmission system. Advanced Static VAR Generator （ASVG） is classified as second generation FACTS, The fundamental principle of ASVG is the generation of a controllable ac voltage source by voltage source inverter connected to a dc capacitor. In this way, ASVG can provide smooth and rapid reactive power compensation to power system. Successful applications of ASVG equipment for voltage control and transient stability improvement have been reported in a lot of literature. Conventionally, the ASVG reactive current regulator is proportional to integral （PI） type controller. But the traditional controller is not very much effective for all operating conditions because of the inherent highly nonlinear of the set. This paper proposes a nonlinear controller for ASVG reactive current inner-loop control system using sliding mode variable structure control method to improve system stability and dynamic performance. The variable structure control system has the greatest advantage of its adaptiveness to external disturbance and internal model perturbation. It can maintain a desired response characteristic almost independent of the system structure and suits such ASVG control system very well. The article is organized as follows. Firstly, the reactive current control model is built up based on ASVG device level nonlinear mathematical model. The model is transformed into a linear system using feedback linearization technique. Then a pole-placement method is employed to select a suitable sliding mode hyperplane, from which the variable structure control scheme considering disturbance is constructed. The chattering in the control signal is suppressed by replacing the sign function with a smoothing function in the control function. Finally, the control logic is evaluated in Matlab/simulink, and the simulation results are compared with the traditional PID control design. It is shown that the proposed approach is superior to the traditional PID method in response performance, has stronger robustness against external disturbance.