Vindhyachal - Back-to-Back Converter Station

The Vindhyachal Back-to-Back HVDC project is a high voltage direct current transmission system in India. Located in the central state of Madhya Pradesh, it was commissioned in 1989 to interconnect the asynchronous 400 kV AC networks of India's Northern and Western regions.

Technical Specifications

The Vindhyachal HVDC link is a 500 MW back-to-back system, meaning it has no transmission line and directly connects two AC grids at a single point. It consists of two poles, each rated at 250 MW. The system operates at an AC voltage of 400 kV and a DC voltage of ±70 kV.

There are 8 converter transformers, each rated at 156 MVA.

Project Timeline and Upgrades

The project was completed in April 1989. In 2019, Siemens was contracted to upgrade and modernize the Vindhyachal HVDC link, as it was the oldest HVDC link in India. The upgrade project was completed in 2022 and included the installation of new thyristor valves, a converter cooling system, an HVDC control and protection system, DC measuring devices, and surge arrestors.

Technology and Components

The Vindhyachal HVDC system uses thyristor-based technology for AC/DC conversion. The upgrade replaced the old electrically-triggered thyristors with new light-triggered thyristors that have a higher voltage blocking capability. This change halved the number of thyristors, resulting in reduced power losses.

Importance and Function

The Vindhyachal Back-to-Back HVDC link serves several important functions. It enables power transfer between the Northern and Western grids of India, which operate asynchronously. This interconnection allows for better load management and improved grid stability. The HVDC technology also provides rapid control of power flow, which is beneficial for grid operations.