A flexible online coordinated voltage control algorithm for SVCs and slow-time-scale devices in transmission systems

After determining the optimal control variables in the offline stage of a coordinated voltage control scheme, an online stage is necessary to modify the control device parameters to face voltage and other indices violations under uncertain real-time conditions. This paper proposes an online coordinated voltage control for static VAr compensators (SVCs) as fast-time-scale control devices and capacitor banks (CBs) and load tap changers (LTCs) as slow-time-scale control devices in the transmission system. The aim of the control is attaining the desired SVCs’ reactive power reserve and keeping the voltages in an acceptable range when unpredicted variations of load or generation occur in the network. he SVCs, as the master agents, send the required commands to the LTCs and the capacitor banks in the voltage control area. The control commands are sent considering priorities and reactive power limits of the voltage control devices to limit the number of capacitors switching and LTCs tap changing. The proposed algorithm controls the SVC reactive power reserve and the bus voltage using local measurements and controllers, and simple communication is only required to send commands from the SVCs to nearby voltage control devices. The proposed method is a generalized scheme to control SVCs operating in voltage control mode (VCM) or reactive power control mode (RPCM). The ability to change the operation mode of SVCs from RPCM to VCM and vice versa and to adjust or correct the SVC parameters is another capability of the proposed algorithm that increases the flexibility of the algorithm for attaining the concerned objectives.