Inter-area oscillation minimization in power system

Abstract

Inter-area oscillations result from system events coupled with a poorly damped electric power system. These oscillations are observed in large power systems, encompassing groups of generators or generating plants connected by relatively weak tie lines. The low-frequency modes (0.1 to 0.8 Hz) often involve groups of generators or generating plants on one side of the tie oscillating against groups of generators on the other side of the tie bus. These oscillations are undesirable as they lead to suboptimal power flows, inefficient grid operation, and, consequently, grid instability. Mitigating these oscillations is of vital concern. To address inter-area oscillations, equipment such as Static Var Compensators (SVCs) and various Flexible AC Transmission System (FACTS) devices are increasingly employed. The feasibility of these techniques has been made possible by recent advancements in power electronic technology. The involvement of SVCs and FACTS devices in the transmission network is referred to as Variable Series Compensation (VSC). In addition to FACTS devices, the application of Superconducting Magnetic Energy Storage (SMES) to enhance inter-area oscillation damping has been reported. Although Power System Stabilizers (PSS) are present in many generators, their effect is limited to the local area and does not effectively damp out inter-area oscillations. In this research work, it has been demonstrated that inter-area oscillations can be detected using phasor measurement units (PMUs) installed in the power system. In a typical implementation, one or more generators in a system are selected as Remote Feedback Controllers (RFCs). These RFCs receive synchronized phasor measurements from one or more remote phasor measurement units. Analyzing the phase angles provided from multiple sites enables the detection of inter-area oscillations. If an oscillation is detected, a control signal is sent to the generator's voltage regulator, effectively modulating the voltage and damping out the oscillation