Study Of VSC Based Stabilizer To Damp Power System Low-Frequency Oscillations

The voltage source converters(VSCs)are the most important dynamic components in a VSC-based DC/AC power system.The integration of VSC to the conventional power grid may impose low-frequency oscillations(LFOs)problem and can degrade the power system stability and reliability.It is well known that the main cause of LFOs is lack of sufficient damping in the power system.Poor damping could be brought about by the(1)large amount of long-distance power transmission,(2)weak interconnection of large power sub-networks,and/or(3)negative damping due to the fast-acting high-gain AVRs.In addition,these low-frequency oscillations are also a major barrier to improve the dynamic performance of the power system.If adequate damping is not provided,then these oscillations may not only trigger severe faults but also may cause power system collapse.To cope with this problem and increase the damping of the power system,a VSC based stabilizer needs to be introduced in the power system.In this study,the integration of VSC based stabilizer to the conventional grid has been investigated through modal analysis(MA).The proposed scheme adopted in single machine infinite bus(SMIB)power system.Based on eigenvalue computation from modal analysis,a supplementary controller i.e.PSS added in power system that provides positive damping by suppressing these LFOs.In order to gain better performance,the optimal location and parameter tuning of the supplementary controller is also very important.In this study,the optimal location of PSS is found based on the participation factor while the optimal parameters of PSS are found using particle swarm optimization(PSO)technique by selecting a suitable objective function.The suitable objective function is the damping ratio of eigenvalues corresponding to system critical modes obtained from the analysis of the linearized model of the system around the operating point.The time domain non-linear simulation results showed that the optimal tuning of PSS parameters and its optimal location significantly improves the damping and stability of power system.