Improving Compensation of Turbo-expander starting by Modified DVR and STATCOM in Neka Power Plant under Fault Condition

In order to prevent energy waste by throttle valve in gas pressure reducing station of Neka thermal power plant, a turbo-expander with a capacity of 9.8 MW for the power plant was prepared and installed. Presence of turbo-expander in Neka power plant due to the absorption of 63 MVAr reactive power at the moment of starting, resulted in severe voltage drops in the auxiliary service system and outage of sensitive equipment to voltage level, which makes impossible the operation of the turbo-expander. In this paper, while pathology of turbo-expander and their performance Improvement using compensator, to review all topologies of dynamic voltage restorer compensator and improved topology will be presented. Then, for optimal performance of compensators the possible points presence of them on the auxiliary service system of Neka power plant in various scenarios under synchronization of fault occurring conditions and starting will be tested. The results of PSCAD / EMTDC software simulation show by using improved topology of dynamic voltage restorer, voltage sag of turbo-expander starting compensated in various scenarios and can be provide the total auxiliary service system power consumption of this power plant by turbo-expander instead of using the generation of power plant.