Damping Power System Oscillations Using an SSSC-Based Hybrid Series Capacitive Compensation Scheme

Abstract

Interconnection of electric power systems is becoming increasingly widespread as part of the power exchange between countries as well as regions within countries in many parts of the world. There are numerous examples of interconnection of remotely separated regions within one country. Such are found in the Nordic countries, Argentina, and Brazil. In cases of long distance AC transmission, as in interconnected power systems, care has to be taken for safeguarding of synchronism as well as stable system voltages, particularly in conjunction with system faults. With series compensation, bulk AC power transmission over very long distances (over 1000 km) is a reality today. These long distance power transfers cause, however, the system low-frequency oscillations to become more lightly damped. As a result, many power network operators are taking steps to add supplementary damping devices in their systems to improve the system security by damping these undesirable oscillations. With the advent of voltage sourced converter-based series compensation, AC power system interconnections can be brought to their fullest benefit by optimizing their power transmission capability, safeguarding system stability under various operating conditions and optimizing the load sharing between parallel circuits at all times. This thesis reports the results of digital time-domain simulation studies that are carried out to investigate the effectiveness of a phase imbalanced hybrid single-phase-Static Synchronous Series Compensator (SSSC) compensation scheme in damping power system oscillations in multi-machine power systems. This scheme, which is feasible, technically sound, and has an industrial application potential, is economically attractive when compared with the full three-phase-SSSC. Time-domain simulations are conducted on a benchmark model using the ElectroMagnetic Transients Program (EMTP-RV). The results of the investigations have demonstrated that the hybrid single-phase-SSSC compensation scheme is very effective in damping power system oscillations at different loading profiles.