Large blackouts are typically caused by cascading failure propagating through a power system by means of a variety of processes. Because of the wide range of time scales, multiple interacting processes, and the huge number of possible interactions, the simulation and analysis of cascading blackouts is extremely complicated. This paper defines cascading failure for blackouts and gives an initial review of the current understanding, industrial tools, and the challenges and emerging methods of analysis and simulation.

Uploaded: February 22, 2008. 2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, Task Force on Understanding, Prediction, Mitigation and Restoration of Cascading Failures, Pittsburgh, Pennsylvania, July 20-24, 2008.

Abstract— The use of distributed generation is growing steadily, motivating a need for flexible interconnection strategies. The resulting microgrid concept allows sub-networks of sources and loads to maintain reliable operation when disconnected from the main grid. The paper presents a control strategy for inverter-based sources that supports transitioning between grid connection and autonomous operation. The controller regulates the inverter terminal voltage and the active power delivered to the AC system, and takes into account the phase-locked loop (PLL) dynamics. An example, in which two SOFC plants provide power to a microgrid, explores controller behaviour. The investigation considers disconnection from the main grid, autonomous operation, and re-synchronization with the main grid.

2008 American Control Conference, Seattle, WA, June 11-13, 2008. Uploaded: April 17, 2008. (program agenda)

Abstract— In this paper, we continue to analyze optimal dispatch of generation and transmission topology to meet load as a mixed integer program (MIP) with binary variables representing the state of the transmission element (line or transformer). Previous research showed a 25% savings by dispatching the IEEE 118-bus test case with a DCOPF. This paper is an extension of that work by examining the effects of transmission switching with an N-1 DCOPF on the IEEE 118-bus and the IEEE 73-bus test case, also known as the RTS 96 system. We demonstrate that these networks can be operated to satisfy N-1 standards while cutting costs by incorporating transmission switching into the dispatch. In some cases, the percent savings from transmission switching was higher with an N-1 DCOPF formulation than with a DCOPF formulation. We also analyze both IEEE test cases at varying load levels.

Uploaded: April 17, 2008. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 24, NO. 3, AUGUST 2009.

Abstract— In this paper, we continue to analyze optimal dispatch of generation and transmission topology to meet load as a mixed integer program (MIP) with binary variables representing the state of the transmission element (line or transformer). Previous research showed a 25% savings by dispatching the IEEE 118-bus test case. This paper is an extension of that work. It presents how changing the topology affects nodal prices, load payment, generation revenues, cost, and rents, congestion rents, and flowgate prices. Results indicate that changing the topology to cut costs typically results in lower load payments and higher generation rents for this network. Computational issues are also discussed.

Uploaded: April 17, 2008. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 3, AUGUST 2008.

Abstract— Load serving entities providing electricity to regulated customers have an obligation to serve load that is subject to systematic and random fluctuations at fixed prices. In some jurisdictions like New Jersey, such obligations are auctioned off annually to third parties that commit to serve a fixed percentage of the fluctuating load at a fixed energy price. In either case the entity holding the load following obligation is exposed to the load variation and to a volatile wholesale spot market price which is correlated with the load level. Such double exposure to price and volume results in a net revenue exposure that is quadratic in price and cannot be adequately hedged with simple forward contracts whose payoff is linear in price. A fixed quantity forward contract cover, is likely to be short when the spot price is high and long when the spot price is low.

In this paper we develop a self-financed hedging portfolio consisting of a risk free bond, a forward contract, and a spectrum of call and put options with different strike prices. A popular portfolio design criterion is the maximization of expected hedged profits subject to a value at risk (VaR) constraint. Unfortunately, that criteria is difficult to implement directly due to the complicated form of the VaR constraint. We show, however, that under plausible distributional assumptions, the optimal VaR contrained portfolio is on the efficient Mean-Variance frontier. Hence, we propose an approximation method that restricts the search for the optimal VaR constrained portfolio to that efficient frontier. The proposed approach is particularly attractive when the Mean-Variance efficient frontier can be represented analytically, as is the case, when the load and logarithm of price follow a bivariate normal distribution. We illustrate the results with a numerical example.

PSERC unpublished working paper. Uploaded: April 17, 2008.

Abstract— Numerous models have been proposed for representing variable-speed wind turbines in grid stability studies. Often the values for model parameters are poorly known though. The paper initially uses trajectory sensitivities to quantify the effects of individual parameters on the dynamic behavior of wind turbine generators. A parameter estimating process is then used to deduce parameter values from disturbance measurements. Issues of estimation bias arising from non-identifiable parameters are considered. The paper explores the connection between the type of disturbance and the parameters that can be identified from corresponding measurements. This information is valuable in determining the measurements that are required from testing procedures and disturbances in order to build a trustworthy model.

Uploaded: June 9, 2008. 2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, Task Force on Understanding, Prediction, Mitigation and Restoration of Cascading Failures, Pittsburgh, Pennsylvania, July 20-24, 2008

Abstract— The first part of the paper summarizes how “ co-optimization” can be used to determine the correct nodal prices for an optimum AC dispatch that meets industry standards of operating reliability. The co-optimization criterion minimizes the expected cost of meeting load over an explicit set of credible contingencies. The corresponding nodal prices reflect the patterns of dispatch for the intact system as well as for the contingencies. Due to the computational limitations of solving large AC Optimal Power Flows (OPF) for real networks, system operators typically use proxy limits to approximate the non-linear constraints caused, for example, by limits on voltage. Even if the resulting dispatch using these proxy limits corresponds closely to the optimum AC dispatch, the corresponding nodal prices are highly misleading, particularly when the system is stressed.

Uploaded: September 9, 2008. Paper delivered at 21st Annual Western Conference, Advanced Workshop in Regulation and Competition, Center for Research in Regulated Industries, Hyatt Regency, Monterey, California, June 18-20, 2008.

Abstract— The two basic criteria used by the North-American Electric Reliability Council (NERC) to measure reliability are:

1) “ Adequacy” (to ensure that the installed capacity of the supply system is sufficient to meet projected future loads and limit the Loss of Load Expectation (LOLE) to one day in ten years), and
2) “ Operating Reliability” (to commit generating units with sufficient reserve capacity to withstand sudden disturbances such as equipment failures).

Assuming that the transmission system meets the adequacy criterion, adopting a specific LOLE standard makes it feasible to determine the corresponding reserve margins for generating capacity that are needed to maintain operating reliability in real time.

Uploaded: September 9, 2008. Paper delivered at 21st Annual Western Conference, Advanced Workshop in Regulation and Competition, Center for Research in Regulated Industries, Hyatt Regency, Monterey, California, June 18-20, 2008.

We study cascading transmission line outages recorded over nine years in an electric power system with approximately 200 lines. The average amount of propagation of the line outages is estimated from the data. The distribution of the total number of line outages is predicted from the propagation and the initial outages using a Galton– Watson branching process model of cascading failure.

Uploaded: September 24, 2008. IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS— II: EXPRESS BRIEFS, VOL. 55, NO. 9, SEPTEMBER 2008.

Abstract— Cascading transmission line outages contribute to widespread blackouts. Engineers respond to the risk of cascading line outages by applying policies such as the n-1 criterion and upgrading lines involved in recent cascading outages. The transmission grid slowly evolves as these policies are applied to maintain reliability while the load grows. We suggest how to assess the long-term effect of these policies on the risk of cascading line outages by simulating both the cascading and the slow evolution of the transmission grid. The long-term effects of these policies on the probability distribution of outage size and the grid utilization are computed for the IEEE 118-bus test system. The results show complex system self-organization of an evolving transmission grid.

Uploaded October 10, 2008. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 3, AUGUST 2008.