Power System Stability Enhancement using Static Synchronous Series Compensator

Abstract

The electricity demand is increasing with the rapidly increasing population. The utility companies are not only obliged to fulfill this demand, but, to also take care of the power system repercussions that can take place in achieving this goal. The revolution of power electronics devices has certainly helped the utilities in performing these tasks. These power electronics devices offer fast and reliable switching which provide an opportunity to enhance the value of electric energy. Nowadays renewable generation is finding great attention and integrating this renewable energy to the conventional grid requires the utilization of power electronics converters. The variable speed drives based on power electronics devices also serve in saving energy up to a great extent. The generation is not the sole part controlling the power system repercussions. The transmission and the distribution systems are also having a great role to play in maintaining the power system stability. Both these systems ensure that the generated power reaches to the customer as per requirements. This end-use energy must be within the permissible standard range free from distortions. With the evolution of power electronics based FACTS (Flexible AC Transmission System) controllers, the power transfer capability and controllability of electrical network is greatly enhanced. These FACTS controllers installed at the transmission level can provide series as well as shunt compensation to the lines depending on the topology of the controller. This project depicts the effectiveness of FACTS controller in regard to series compensation. The FACTS controller considered for achieving this goal is termed as SSSC (Static Synchronous Series Compensator). The important aspect lies in enhancement of power system stability using SSSC. Through series compensation SSSC can provide various benefits such as improvement of transient stability limit, control of power flow in the line, fast control to minimize the effect of disturbances, minimize receiving end voltage variation, damping of power oscillations, etc. In this project the damping of power oscillations in the power system with the help of SSSC integration is demonstrated. The reference voltage signal for voltage injection in the line is provided by a POD (Power Oscillation Damping) controller. The damping controller consists of a controller gain, low-pass filter, washout high-pass filter, lead compensator and output limiter. The two test systems analyzed in the MATLAB Simulink software are namely, 2-machine system and 9-bus system. In both these test systems the dynamic response of SSSC in effectively damping out the low frequency power oscillations is depicted through various MATLAB figure waveforms. The results show that with the help of POD controller the SSSC easily damps out the power oscillations in the system. Thus, SSSC helps in enhancement of power system stability. In future the more complex systems like 14-bus, 30-bus, 33-bus, 57-bus, can be analyzed in a similar manner. This work provides useful foundation for exploring other complex test systems.