Multilevel inverter structures have been developed to overcome shortcomings in solid-state switching device ratings so that they can be applied to high-voltage electrical systems. The general function of the multilevel inverter is to synthesize a desired AC voltage from several levels of DC voltages. For this reason, multilevel inverters are ideal for connecting either in series or in parallel an AC grid with renewable energy sources such as photovoltaics or fuel cells or with energy storage devices such as capacitors or batteries. In this paper the cascaded H-bridges multilevel inverter is described.

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Multilevel converters as a utility interface for renewable energy systems

The creation of electricity markets has raised the fundamental question as to whether markets provide the right incentives for the provision of the reserves needed to maintain system reliability, or whether some form of regulation is needed. In some states in the US, electricity retailers have been made responsible for providing such reserves by contracting capacity in excess of their forecasted peak demand. The so-called Installed Capacity Markets (ICAP) provide one means for contracting reserves, and are the subject of this paper. In particular, for given productive and transmission capacities, we identify firms' opportunty costs of committing reserves in the capacity market, and hence, the costs of inducing full capacity commitment. Regulatory issues such as the optimal choice of the reserve margin and the capacity deficiency rate (which serves as a price-cap) are analyzed. From a welfare view-point, we also compare the desirability of providing reserves either through capacity markets or through the demand side (i.e., power curtailments).

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Capacity Markets for Electricity

Price caps and investment : Long-run effects in the electric generation industry

The Oak Ridge Competitive electricity Dispatch (ORCED) model has been used for multiple analyses of the impacts of different technologies and policies on the electricity grid. The model was developed over ten years ago and has been greatly enhanced since the initial documentation from June 1998 (ORNL/CON-464). The report gives guidance on the workflow and methodologies used, but does not provide a complete user's manual detailing steps necessary to operate the model. It lists the major resources used, shows the main inputs and outputs of the model, and describes how it can be used for a variety of analyses.

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The Oak Ridge Competitive Electricity Dispatch (ORCED) Model

ELECTRIC POWER MARKET MODELING WITH MULTI-AGENT REINFORCEMENT LEARNING SEPTEMBER 2010 NATHANAEL K. MIKSIS, M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Erin Baker Agent-based modeling (ABM) is a relatively new tool for use in electric power market research. At heart are software agents representing real-world stakeholders in the industry: utilities, power producers, system operators, and regulators. Agents interact in an environment modeled after the real-world market and underlying physical infrastructure of modern power systems. Robust simulation laboratories will allow interested parties to stress test regulatory changes with agents motivated and able to exploit any weaknesses, before making these changes in the real world. Eventually ABM may help develop better understandings of electric market economic dynamics, clarifying both delineations and practical implications of market power. The research presented here builds upon work done in collateral fields of machine learning and computational economics, as well as academic and industry literature on electric power systems. We build a simplified transmission model with agents having learning capabilities, in order to explore agent performance under several plausible scenarios. The model omits significant features of modern electric power markets, but is able to demonstrate successful convergence to stable profit-maximizing equilibria of adaptive agents competing in a quantitybased, available capacity model.

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Electric Power Market Modeling with Multi-Agent Reinforcement Learning

Historically, decisions on the amounts, locations, types, and timing of investments in new generation have been made by vertically integrated utilities with approval from state public utility commissions. As the U.S. electricity industry is restructured, these decisions are being fragmented and dispersed among a variety of organizations. As generation is deregulated and becomes increasingly competitive, decisions on whether to build new generators and to retire, maintain, or repower existing units will increasingly be made by unregulated for-profit corporations. These decisions will be based largely on investor assessments of future profitability and only secondarily on regional reliability requirements. In addition, some customers will choose to face real-time (spot) prices and will respond to the occasionally very high prices by reducing electricity use at those times. Market-determined generation levels will, relative to centrally mandated reserve margins, lead to: (1) more volatile energy prices; (2) lower electricity costs and prices; and (3) a generation mix with more baseload, and less peaking, capacity. During the transition from a vertically integrated, regulated industry to a deintegrated, competitive industry, government regulators and system operators may continue to impose minimum-installed-capacity requirements on load-serving entities. As the industry gains experience with customer responses to real-time pricing and with operation of competitive intrahour energy markets, these requirements will likely disappear. We quantitatively analyzed these issues with the Oak Ridge Competitive Electricity Dispatch model (ORCED). Model results show that the optimal reserve margin depends on various factors, including fuel prices, initial mix of generation capacity, and customer response to electricity prices (load shapes and system load factor). Because the correct reserve margin depends on these generally unpredictable factors, mandated reserve margins might be too high, leading to higher electricity costs and prices. Absent mandated reserve margins, electricity prices and costs decline with increasing customer response to prices during high-demand periods. The issues discussed here are primarily transitional rather than enduring. However, the transition from a highly regulated, vertically integrated industry to one dominated by competition is likely to take another five to ten years.

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E. Hirst

Papers

Maintaining Generation Adequacy in a Restructuring U.S. Electricity Industry