Current status of the Indian power system and dynamic performance enhancement of hydro power systems with asynchronous tie lines

The present research article is devoted to discussing the dynamic performance of a two-area interconnected power system consisting of hydropower plants. It tries to establish that using an HVDC transmission system in parallel with an EHVAC transmission line as an interconnection between two areas has a favorable effect on system dynamic performance in the wake of a small load disturbance in the system. At the outset of the article, the current status of the Indian Power System is summarized, and the challenges ahead for power engineers are discussed in length. The future prospects of hydropower due to environmental considerations, merits of using HVDC transmission systems, and the upcoming interconnected structure of power systems with parallel EHVAC/HVDC transmission systems is presented. The system dynamic performance has been studied with the implementation of optimal AGC regulators in the wake of load disturbance in one of the areas. The investigations carried out justify the application of an HVDC transmission link in parallel with an EHVAC transmission line as a system interconnection. The HVDC transmission link is considered to be operating in constant current control mode. The power flow deviation through the HVDC link is modeled based on frequency deviation at the rectifier end. Two modes of an HVDC link dynamic model-as an additional control variable with turbine controllers and as an additional state variable-have been investigated. Both modes of the HVDC link dynamic model offer the better system dynamic performance as compared to that obtained without considering an HVDC link in system dynamic modeling.