Dynamic Stability Improvement of Power System with VSC-HVDC Transmission

Abstract

Presently power system operates under a high stress level which was neglected at the moment they were designed. The operating conditions of power system is being threatened form the reliability, controllability and security point of view. HVDC transmission brings a solution to have secure and improve the stability margins of power system. The characteristic like independent control of real and reactive power improves the power system stability and ensures an efficient power transfer. This thesis presents the control strategy used for VSC-HVDC transmission to improve the transient and voltage stability of power system. Transient instability caused by a system faults overcome due to the fast power run back capability of the VSC-HVDC transmission. VSC-HVDC prevents the system from transient instability by its instant power reversal ability. The voltage support capability of VSC system helps to protect the system from voltage collapse, hence losing of synchronism can be avoided. A grid connected back to back VSC-HVDC modeled in MATLAB/ Simulink environment and a current mode control strategy was implemented. The simulation was done to have an observation of a faster and independent control of real and reactive power.