Indian Power System Operation Utilizing Multiple HVDCs and WAMS

Abstract

The Indian power system involves integrated operation of AC and DC transmission system in one synchronous system. Earlier HVDC back-to-back stations were used to transfer power between regional grids when the five regions in Indian grid were not synchronized. EHVAC and HVDC-based high power corridors helped regions deficit in power to obtain power from regions with surplus generation. The skewed distribution of natural resources like coal, hydro, and customer load gave an impetus for better connectivity across the grid. Now Indian power system also has international power transfer with Bhutan, Bangladesh, and Nepal in a step forward toward SAARC grid. The interconnection of the grids is basically an amalgamation of HVDC links (500 and 800 kV) and EHVAC (400 and 765 kV) lines for both inter-regional/national as well as intra-regional power transfer. Synchrophasors at transmission level were first introduced in India in the year 2010 in northern region quickly followed by other regions as well as wide area visibility at the National control centre. By the year 2017, the number of PMUs had ramped up to 77 and with the better visualization tools, and the usage of Synchrophasors for real-time operation by the system operator has increased. The enhanced visibility in grid operation with the use of synchrophasors has helped operator in identifying various aspects of integrated operation and take actions in real time. This chapter discusses the utilization of synchrophasors in control room application for both real-time despatch and post-despatch analysis. Various case scenarios have been discussed whereby one or the other parameter at nearby AC bus gave an indication of some HVDC-related phenomenon. As HVDC system is embedded in existing large-scale HVAC network, any phenomenon happening at HVDC station impacts the power flow of network as a whole. Apart from easily identifying HVDC restarts, reduced voltage operation (RVO) mode, HVDC islanding the synchrophasors helped in understanding voltage changes associated with filter bank switching. Several mathematical functionalities related to optimized power order across all HVDCs are under nascent stage.