Oklaunion - Back-to-Back Converter Station

The Oklaunion HVDC system is an important power transmission link connecting the Texas (ERCOT) and Oklahoma (SPP) power grids. It serves as an asynchronous interconnection between these two grids, enabling efficient power exchange and enhanced grid reliability.

Technical Specifications

The current Oklaunion HVDC system, commissioned in 2014, replaced a 30-year-old converter station originally built by General Electric in 1984. The new system, engineered and installed by ABB (now Hitachi Energy), is a back-to-back HVDC transmission system with a power rating of 220 MW, capable of delivering power in either direction.

The system operates at a higher capacity and lower voltage than its predecessor, which had a voltage of 82 kV and a transfer rate of 200 MW. The new installation includes several key components: converter valves, converter transformers, and MACH advanced control and protection system.

Black-Start Capability

An important feature of the new Oklaunion HVDC system is its black-start capability. This functionality allows for fast grid restoration in the event of a power outage by enabling power to be used from the other end of the link. This capability is particularly valuable for maintaining grid stability and reliability.

Construction and Implementation

The replacement project was completed in just 22 months, with the new station becoming operational in 2014. To minimize the impact on customers during the replacement process, the old HVDC tie remained in operation while the new station was being constructed.

System Benefits

The Oklaunion HVDC link provides several advantages to the power grids it connects. These include enhanced grid reliability, improved power stability, more efficient power exchanges, and better power flow control. The system's ability to transmit power in both directions and its advanced control mechanisms contribute to these benefits, making it an integral part of the interconnection between the Texas and Oklahoma power grids.

Historical Context

The use of HVDC technology in this application is not new. The original Oklaunion HVDC link was part of a longstanding trend of using direct current for high-voltage connections. HVDC is known for its efficiency in transmitting power over long distances, with approximately half the line losses of comparable AC systems.