Flexible Transmission: A Comprehensive Review of Concepts, Technologies, and Market

As global concerns regarding climate change are increasing worldwide, the transition towards clean energy sources has accelerated. Accounting for a large share of energy consumption, the electricity sector is experiencing a significant shift towards renewable energy sources. To accommodate this rapid shift, the transmission system requires major upgrades. Although enhancing grid capacity through transmission system expansion is always a solution, this solution is very costly and requires a protracted permitting process. The concept of flexible transmission encompasses a broad range of technologies and market tools that enable effective reconfiguration and manipulation of the power grid for leveraged dispatch of renewable energy resources. The proliferation of such technologies allows for enhanced transfer capability over the current transmission network, thus reducing the need for grid expansion projects. This paper comprehensively reviews flexible transmission technologies and their role in achieving a net-zero carbon emission grid vision. Flexible transmission definitions from different viewpoints are discussed, and mathematical measures to quantify grid flexibility are reviewed. An extensive range of technologies enhancing flexibility across the grid is introduced and explored in detail. The environmental impacts of flexible transmission, including renewable energy utilization and carbon emission reduction, are presented. Finally, market models required for creating proper incentives for the deployment of flexible transmission and regulatory barriers and challenges are discussed

A Review of Economic Incentives for Efficient Operation of Flexible Transmission

The growing penetration of renewable energy requires upgrades to the transmission network to ensure the deliverability of renewable generation. As an efficient alternative to transmission expansion, flexible transmission technologies, whose benefits have been widely studied, can alleviate transmission system congestion and enhance renewable energy integration. However, under the current market structure, investments for these technologies only receive a regulated rate of return, providing little to no incentive for efficient operation. Additionally, a regulated rate of return creates an incentive for building more transmission lines rather than efficient utilization of the existing system. Therefore, investments in flexible transmission technologies remain rather limited. To facilitate the deployment of flexible transmission, improve system efficiency, and accommodate renewable energy integration, a proper incentive structure for flexible transmission technologies, compatible with the current market design, is vital. This paper reviews the current market-based mechanisms for various flexible transmission technologies, including impedance control, dynamic line rating, and transmission switching. This review pinpoints current challenges of the market-based operation of flexible transmission and provides insights for future endeavors in designing efficient price signals for flexible transmission operation.Comment: 2023 55th North American Power Symposium (NAPS

An aggregator-based dynamic pricing mechanism and optimal scheduling scheme for the electric vehicle charging

High penetration of electric vehicles (EVs) in an uncontrolled manner could have disruptive impacts on the power grid, however, such impacts could be mitigated through an EV demand response program. The successful implementation of an efficient, effective, and aggregated demand response from EV charging depends on the incentive pricing mechanism and the load shifting protocols. In this study, a genetic algorithm-based multi-objective optimization model is developed to generate hourly dynamic Time-of-Use electricity tariffs and facilitate the decision making in load scheduling. As an illustrative example, a case study was carried out to examine the effect of applying demand response for EVs in Beijing, China. With the assumptions made, the maximum peak load can be reduced by 9.8% and the maximum customer savings for the EVs owners can reach 11.85%, compared to the business-as-usual case

Impacts of Variable-Impedance-Based Power Flow Control on Renewable Energy Integration

The electric power grid has evolved significantly over the past two decades in response to climate change. Increased levels of renewable energy generation, as a prominent feature of this evolution, have led to new congestion patterns in the transmission network. The transmission system is originally designed for conventional energy sources, with predictable flow patterns. Insufficient transfer capability in congested transmission systems results in commitment of more expensive power plants and higher levels of renewable energy curtailment. One way to mitigate congestion is adoption of power flow control through variable-impedance flexible ac transmission system (FACTS) devices. In this paper the impacts of power flow control on generation cost, carbon emissions and renewable energy curtailment are studied under a wide range of scenarios, including generation mix from major US regional transmission organizations, and different load curves, representing seasonal variations. A two-stage stochastic unit commitment, including FACTS adjustment, is used to evaluate the impacts of FACTS devices on various types and penetration levels of renewable energy. The results show that FACTS installation effectively reduces generation cost, carbon emissions, and renewable energy curtailment. Location of renewable energy resources, peak-hour demand and the system's generation mix are among the influential factors