The American Transmission Company (ATC) selected ABB to supply a 200 MW back-to-back HVDC Light 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 will be situated on Michigan's Upper Peninsula, near the existing Straits Substation and in line with an 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 now 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 or other stoppages of one converter, the other is designed to run as a STATCOM, continuing to provide dynamic voltage support to the network.
Voltage source converter (VSC) technology was selected over classical HVDC technology in this case because it supports all islanded operation, under certain operating conditions, and provides excellent voltage and reactive power control for wind generation. It also stabilize extremely weak power networks, and has black-start capability, ie, the ability to restart a grid after a black-out.
This is the world's first large-scale back-to-back HVDC system using multilevel VSC technology.