Dissertation/Thesis Abstract

HVDC: New Opportunities to Expand Transmission Capacity
by Reed, Liza B., Ph.D., Carnegie Mellon University, 2020, 126; 28149379
Abstract (Summary)

Decarbonizing the electricity sector, which today accounts for 27% of the US carbon footprint, will require connecting low and no carbon resources to the grid while still meeting growing demand. To successfully meet these two challenges of more and different power the US transmission, infrastructure will need to adapt. Historically, the US has responded to growth in the need for transmission capacity by building new transmission lines. However, this approach requires siting approval and land acquisition, which is increasingly difficult in the face of conflicting federal, state and local regulations, and public and environmental pushback.

High Voltage Direct Current (HVDC) electricity transmission allows for lower loss and more controllable power flow, including a higher power density per mile compared to High Voltage Alternating Current (HVAC). HVDC has more capacity per mile due to narrower right-of-way requirements, and more power transfer over time due to the ability to load the lines near thermal limits without creating a reliability issue in the grid. National studies of future grid needs find that HVDC is a necessary part of meeting the challenge of no carbon electricity. However, the path to realize HVDC grid integration is blocked by technical, economic, and regulatory barriers. It is also often not given due consideration because of long-standing assumptions about cost and capability that ignore progress on both fronts.

Utilities and regulators need to identify new ways to address the transmission needs of the electricity grid that do not saddle future generations with cost or environmental impacts. There is a long history of delays and cancelations of projects to build new transmission. Converting existing HVAC transmission corridors to HVDC could provide 3.5X capacity increases without requiring the acquisition of land for a right-of-way (ROW) but the cost of HVDC stations is often cited as a barrier. The regulatory framework an HVDC project, new build or HVAC conversion, would face in the US is not well known due to the limited number of projects that have reached planning or construction stages. This uncertainty may be a barrier to further consideration of such projects.

There is also a new generation of power electronic devices that has the potential to shift the relative attractiveness of HVAC to HVDC in a variety of contexts using a method called Voltage Source Conversion (VSC). VSC-HVDC stations can control power flow, restart a grid after a blackout, and provide power through tap-off stations along a transmission line. These capabilities could put VSC-HVDC on par with or superior to HVAC solutions for new lines.

The research objectives of this work are as follows:

1. Develop an economic model to compare converting an HVAC line to HVDC with existing HVAC transmission options, and compare the technical and physical constraints of these solutions;

2. Assess the regulatory barriers for different kinds of transmission projects, based on outcomes of proposed projects, and determine what barriers an HVDC project could face;

3. Evaluate the benefits of multi-terminal VSC-HVDC under existing and future cost conditions compared to HVAC alternatives for new transmission line construction.

Transmission projects take 8 – 10 years on average from initial concept to project completion. Siting approval for new lines is already a well-known barrier for transmission expansion. Addressing the specific barriers revealed in this thesis—a systematic bias against HVDC in transmission planning, evaluation and cost estimation—are critical for the future grid.

Indexing (document details)
Advisor: Morgan, M. Granger, Vaishnav, Parth
Commitee: Tierney, Susan, Pan, Jiuping, Armanios, Daniel, Abramson, Alexis
School: Carnegie Mellon University
Department: Engineering and Public Policy
School Location: United States -- Pennsylvania
Source: DAI-A 82/4(E), Dissertation Abstracts International
Subjects: Electrical engineering, Sustainability, Public policy, Economics, Public administration
Keywords: Electricity infrastructure, Electricity transmission, High Voltage Direct Current, HVDC, Transmission capacity, Power electronic devices
Publication Number: 28149379
ISBN: 9798678182890
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