Interaction between phase shifting transformers installed in the tie-lines of interconnected power systems and automatic frequency controllers

FACTS devices like TCPAR can be used to regulate the power flow in tie-lines of interconnected power system. The transient state power flow occurring after power disturbances can be influenced by using TCPAR equipped with power regulator and frequency-based stabilizer. The analysis of a simple interconnected power system consisting of two power systems has shown that the control of TCPAR can force a good damping of both power swings and oscillations of local frequency. In the case of a larger interconnected power system consisting of more than two power systems, the influence of the control of TCPAR on damping can be more complicated. Strong damping of local frequency oscillations and power swings in one tie-line may cause larger oscillations in remote tie-lines and other systems. Hence the use of devices like TCPAR as tools for damping power swings and frequency oscillations in a large interconnected power system must be justified by detailed analysis of power system dynamics. In this paper, some results of time-domain simulations of a three-system area are presented. These results have proven that it is possible to obtain a good damping of tie-line power and frequency swings by optimizing the main parameters of TCPAR installed in tie-lines. The results have been confirmed by an eigenvalue analysis of linearized model of interconnected system consisting of three subsystems.

► Frequency and power angle modes are most sensitive to the TCPAR parameters. ► Larger is the number of TCPAR devices, more difficult is their coordination and setting. ► Sensitivity analysis of system eigenvalues helps in analyzing slow phenomena in a multi-area power system.