Consider Converting to HVDC, Part 4
Rachana Gururaj and M. Granger Morgan are with the Department of Engineering and Public Policy, Carnegie Mellon University. Liza Reed is with the Niskanen Center in Washington, D.C.
As the country gets serious about decarbonizing the economy, we will need to move more power through the high voltage transmission system. In the third article in this four-part series, we described two strategies to move more power through an existing HVAC line: reconductoring and increasing the operating voltage.
We also explained that it may sometimes be possible to increase the amount of power that can be moved through a transmission corridor by as much as two hundred and fifty percent by converting an existing HVAC line to HVDC.
In this final article of our series, we introduce one other strategy that uses modern power electronics in ways that can both control power flow in an HVAC line and increase a line's operational capacity.
In an ordinary AC power grid, the direction and amount of power that flows through the lines is determined by the electrical properties of the lines that are governed by the laws of physics, including Kirchhoff's Law.
Because grid operators have limited control over the flows of power, in many cases the amount of power that system operators can move through longer HVAC lines is much less than their "thermal limit" — the level of current at which the line heats up, expands and sags too much to be safe.