| Many kinds of UPFC devices exist in power grid currently, and the control systems are based on local information, for the limiting of extracting information. This will cause multiple SISO controller working well when running alone,while appearing negative interaction when joint operation for lacking of coordination. UPFC,as the most versatile FACTS device, contains a plurality of controllers. The control strategy,ignoring negative interaction effects,will affect its control effect and endanger the stability of the grid. Currently,the study on negative interaction and coordination controlling of UPFC, based on local measurements, which exist limitations.WAMS provides a new idea for the study of FACTS devices.With WAMS’s function of online real-time measurement,the paper studies the interaction analysis method and coordinated control program of UPFC controllers.Firstly,based on the working relationship between the controllers of UPFC, the mechanism of negative interaction is expanded,when power flow controller joint operating with other controllers.By choosing negative interaction indicator and defining active compensation degree,the relationship between the degree of negative interaction and active power flow control is analyzed with qualitative and quantitative method. It put forwards that negative interaction,existing between UPFC controllers,can’t be ignored.Therefore,the control strategy,considering the negative interaction between the controllers,is essential to ensure effective and stable operation.According to the mechanism of negative interaction,the control strategies of UPFC are ameliorated.Flow decoupling controller is designed with hierarchical structure, which can achieve the function of active and reactive decoupling. Additional controller is designed with the Lyapunov method and transient energy function,which can improve transient stability of the system.The dual-loop control system of UPFC series and parallel-side converter is ameliorated,which can improve the voltage unbalance of the DC capacitor caused by active control.In the electric power system with UPFC, depending on the operating conditions to select appropriate control model is the key to online real-time monitoring system.One kind of coordinated control program,under different operating conditions,is presented.The program can achieve flexible switching of UPFC control model,make sure the coordination between controllers,reduce the negative interaction,and better meet the requirements of security,stability and flexible running. |
