Mackinac

The American Transmission Company (ATC) selected Hitachi Energy to supply a 200 MW back-to-back HVDC Light^® converter station to help control power flow, enhance grid stability, and allow for the integration of additional renewable energy sources in the state of Michigan, U.S.A.

The station is situated on Michigan's Upper Peninsula, near the Straits Substation and in line with a pre-existing 138 kV AC cable double circuit across the Straits of Mackinac, a narrow waterway that separates Michigan's upper and lower peninsulas, and connects two of the Great Lakes, Michigan and Huron.

Energy sources in the region include renewables such as wind farms west of the Great Lakes, while some sources of traditional generation like coal power plants are shutting down or reducing output. The rugged landscape also creates difficulties for electrical transmission, preventing power lines from equally sharing the electrical load, as electricity inputs increase.

The Mackinac back-to-back HVDC Light installation provides a buffer that can slow down and redirect large amounts of electrical power, so the regional network isn't overwhelmed. During maintenance of one converter, the other converter is designed to run as a STATCOM, continuing to provide dynamic voltage support to the network.

The HVDC solution boosts power capacity and enhances grid stability and reliability through power flow control. It also supports integration of more wind power into the energy mix.

Voltage source converter (VSC) technology was selected over classic HVDC technology as it supports all islanded operation, under certain operating conditions, and provides excellent voltage and reactive power control for wind generation. It also stabilizes extremely weak power networks, and has black-start capability, i.e., the ability to restart a grid after a black-out.

This was the world's first large-scale back-to-back HVDC system using multilevel VSC technology.