Vizag II - Back-to-Back Converter Station

The Vizag 2 HVDC project is a back-to-back HVDC converter station located near Visakhapatnam, India. It was commissioned in 2005 as an expansion of the existing Vizag 1 station, increasing the total power transmission capacity between the eastern and southern power grids of India.

Technical Specifications

The Vizag 2 station has a rated power transmission capacity of 500 MW. It operates at a nominal DC voltage of 176 kV and has a current rating of 2,841 Amperes. The station uses air-insulated, water-cooled thyristor valves for power conversion.

Station Layout and Components

The Vizag 2 station occupies an area of approximately 450 x 150 meters. It consists of several key components:

Thyristor Valves: The station employs quadruple valve configuration. Each valve comprises six thyristor modules, with six thyristors per module. The total number of thyristors in the station is 864. The maximum voltage per thyristor is 7.2 kV.

Cooling System: The thyristor valves are cooled using a demineralized water cooling system.

Converter Transformers: The station uses single-phase, three-winding transformers. There are six units, each rated at 201 MVA.

AC Filters: On the eastern side, there are three banks of filters, each rated at 110 Mvar with a configuration of hp12/24. The southern side has an identical filter arrangement.

Smoothing Reactors: The station has two air-insulated smoothing reactors, each with an inductance of 30 mH.

Shunt Reactors: Each side of the station is equipped with an 80 Mvar shunt reactor.

Control and Operation

The maximum increase in firing angle for the thyristor valves is 63 degrees. This allows for precise control of power flow between the connected AC grids.

Purpose and Benefits

The Vizag 2 HVDC station plays an important role in the Indian power grid by enabling asynchronous interconnection between the eastern and southern regional grids. It provides voltage and frequency support for both grids during power disturbances. The station also allows controlled power flow between regions, enhancing grid stability and reliability.

Current Status

It's worth noting that since December 31, 2013, the Indian power grid has been synchronized into a single AC grid. While this reduced the need for asynchronous linking, the Vizag 2 station can still be utilized as an embedded power flow device to help control power flow within the AC system.