We estimate with a branching process model the propagation of load shed and the probability distribution of load shed in simulated blackouts of an electric power system. The average propagation of the simulated load shed data is estimated and then the initial load shed is discretized and propagated with a Galton-Watson branching process model of cascading failure to estimate the probability distribution of total load shed. We initially test the estimated distribution of total load shed using load shed data generated by the OPA simulation of cascading transmission line outages on the 300 bus IEEE test system. We discuss the effectiveness of the estimator in terms of how many cascades need to be simulated to predict the distribution of load shed accurately.

Uploaded March 1, 2010. Complexity in Engineering (COMPENG 2010), Rome, Italy, February 22-24, 2010.

Power systems under stress can show large voltage angle differences between areas that can be monitored by wide area phasor measurements. One way to make this idea more specific is to choose a cutset of transmission lines that separates two power system areas and then define an angle difference across the cutset that is a suitable combination of the angle differences across lines of the cutset. We suggest that monitoring this cutset angle yields useful and specific information about power system stress.

Uploaded: March 1, 2010. 43rd Hawaii International Conference on System Sciences (HICSS 2010), Honolulu, Hawaii, January 5-8, 2010. (best paper award)

We show how to combine together voltage angle phasor measurements at several buses to measure the angle stress across an area of the power system that is called a cutset area. The angle across the cutset area is a weighted average of the angles measured at buses at the borders of the cutset area. The angle across the cutset area is based on circuit theory and it responds to power flow through the area and to line trips inside the cutset area. The angle across the cutset area gives stress information that is specific to the cutset area and is a generalization of the angle difference between two buses. The concepts are illustrated with several choices of cutset areas in a 225 bus model of the Western North American power system.

Uploaded March 1, 2010. 2010 IEEE Power and Energy Society General Meeting (2010 PES-GM), Minneapolis, Minnesota, July 25-29, 2010.

This paper is motivated by the need to automate adjustments of deviations in key output variables from their scheduled values. In particular, it is important to maintain load voltages within their pre-specified limits in response to many disturbances, for example load power factor deviations. Similarly, it is important to regulate real power line flows to within their pre-specified limits as disturbances around scheduled real power generation dispatch take place. Such automation is a feasible goal since the PMUs could provide accurate and fast sensing of key output variables of interest. Given the number of PMUs, the selection of best locations of PMUs and the control design based on these measurements becomes an engineering design problem.

In this paper we provide a problem formulation for a robust Automated Voltage Control (AVC) and Automated Flow Control (AFC) design based on selecting the best locations for placing the PMUs. The AVC and AFC designs are illustrated using a small 5-bus example first. This is followed by illustrating potential performance of such design on an equivalent NPCC 36-bus system. The results indicate that the (N-1) reliability criteria can be met by combining the economic dispatch for scheduling resources given demand forecast, and by relying on an automated feedback to ensure that voltage and line flow deviations remain within the pre-specified limits in between scheduling intervals. This is done without having to know the exact location and magnitude of disturbances.

Uploaded: March 9, 2010. 2010 IEEE Power and Energy Society General Meeting (2010 PES-GM), Minneapolis, Minnesota, July 25-29, 2010.

The U.S. is not well positioned to handle high penetrations of renewable generation technologies due to the state of the current electric delivery grid along with its associated planning and operation criteria. This shortcoming also applies to the power engineering workforce which is only now beginning to see topics related to integration of renewable resources being introduced in the curriculum. Certainly there are challenges in developing renewable generation technologies, such as reducing the capital costs and improving energy efficiencies of the various types of renewable resources, such as wind, solar PV, solar thermal, and wave. Breakthroughs are also needed in large-scale energy storage technologies. To seamlessly integrate renewable resources in the grid, research and development must address challenges that high penetration levels will have in power system planning and operation, and in grid connection. Finally, the existing workforce and the students going into power and energy engineering careers need to be educated so that they can envision and develop the new approaches and technologies to maintain grid reliability and economy.

A PSERC White Paper. Uploaded: April 30, 2010.

CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a “ microgrid” . The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system can disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts were demonstrated at a full-scale test bed built near Columbus, Ohio and operated by American Electric Power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resynchronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults.

Uploaded: May 7, 2010. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 26, NO. 1, PP. 325-332, JANUARY 2011.
2009 CIGRE / IEEE Power & Energy Society Joint Symposium: Integration of Wide-Scale Renewable Resources Into the Power Delivery System, Calgary, Canada, July 29-31, 2009.

We define the voltage angle across an area of a power system to measure the area stress. The voltage angle across the area is a weighted combination of the voltage angles at all the buses along the border of an area. The area angle can be divided into two parts; one part is internal stress caused by power injections inside the area and the other part is external stress caused by power flows from other areas. The area angle can be monitored using voltage synchrophasor measurements at the border buses. If the currents or powers flowing into the area at the border buses are also measured, then the internal stress angle can also be monitored. The internal stress angle changes when lines inside the area outage or when there is redispatch of power within the area. The internal stress angle does not change when lines outage outside the area or power is redispatched outside the area. This makes the internal stress angle useful for detecting and monitoring changes inside the area. If it is known which line inside the area is outaged, the an gle across the line after the outage can be computed from the change in the internal stress angle. The analysis uses a DC load flow model of the power system and exploits the recently discovered cutset angle.

Uploaded: September 2, 2010. Proceedings of IREP 2010, Bulk Power System Dynamics and Control - VIII, Buzios, Rio de Janeiro, Brazil, August 1-6, 2010.

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 26, NO. 1, PP. 325-332, JANUARY 2011.