HVDC Systems - enabling long distance bulk power transmission to meet India´s growing energy needs
During the last 10 years, we have seen a remarkable growth in the transmission of power through High Voltage Direct Current (HVDC) systems. This growth has been fuelled by the need for transmitting bulk power over long distances with high efficiency and connection of renewable energy sources to the grid. The scenario is no different in India, where rising land costs and right-of-way (ROW) problems are driving the requirement of HVDC systems to meet the power transmission requirements, as ROW requirements of HVDC transmission system is much lower than alternative current (AC) system for the same amount of power transfer. The first long distance HVDC transmission system in India was commissioned in 1990 and the installed HVDC capacity till March, 2015 is 13,500 MW. Currently Power Grid Corporation of India is implementing a 800 kV (some numeral missing here) MW HVDC transmission system in India which will connect hydro generation in the North Eastern region with load centres in the northern region. This system is part of a HVDC high capacity corridor which would facilitate bulk hydro power transfer from the upcoming generation projects in the north-eastern states and Bhutan to load centres in the northern and western parts of India. More such HVDC corridors are expected to be completed in the next few years, including Champa-Kurukshetra 800 kV/6,000 MW (1,350 km) and Raigarh-Pugalur-New Trichur (1,600 km). With rapid expansion in the Indian grid and the resultant complexity in grid operations, the role of HVDC systems gains more prominence due to the inherent advantages in HVDC technology over conventional AC transmission systems.
HVDC transmission systems offer the optimum techno-economical solution for long distance power transmission (more than 700 km in the Indian context), integrating renewable generation, and stabilising existing AC power networks. The improved energy transmission possibilities also contribute to a more efficient utilisation of existing power plants, thereby helping in meeting the ever increasing electricity demand.
Furthermore, power flow on HVDC links is fully controllable unlike AC power systems where power flow direction and magnitude depends on grid configurations. Since HVDC transmission has lower losses than AC transmission, HVDC transmission has been recognized as a green technology by the United Nations Framework Convention on Climate Change (UNFCCC). Besides, HVDC system can be used to connect two asynchronous AC systems, enabling interconnection of grids of neighbouring countries and regions.
Given India´s firm focus on renewable energy, including those from solar and wind, HVDC is bound to play an even bigger role in the country´s transmission set up in the coming years. The government is aiming at a renewable energy capacity of 175,000 MW by 2022. This includes solar power at 100,000 MW followed by 60,000 MW from wind energy, 10,000 MW biomass energy and 5,000 MW of small hydro projects. The Indian government recently approved offshore wind power generation and this will only add to the demand for HVDC networks as the only technical solution for connecting off-shore wind farms (more than 20 km away) to the grid is using HVDC submarine cables.
Across the globe, growth in electricity demand, congestion in transmission networks and grid instability are firing up demand for HVDC systems. It is estimated that approximately, 110 HVDC transmission lines will be built world-wide by 2020 and approximately 333 gigawatts (GW) of new HVDC transmission capacity will be added between 2013 and 2020. This includes nearly 200 GW in China alone. Globally, a chunk of HVDC demand is being driven by the increasing need for integration of new and renewable energy resources, particularly offshore wind power. Several governments in Europe have stipulated offshore wind targets. As a result, power utilities are executing plans for offshore wind development, thereby creating a market demand for offshore HVDC solutions.
Clearly, in HVDC technology, power companies have found a panacea to multiple challenges, including need to transmit bulk power efficiently over long distances in existing network, renewable energy resource integration and earning carbon credits.
Author: Rathin Basu, Country President & Managing Director, Alstom India & South Asia.