Gerald T. Heydt

The Next Generation of Power Distribution Systems

This paper summarizes diverse concepts for the next generation of power distribution system. The objective is to bring distribution engineering more closely aligned to smart grid philosophy. Issues of design, operation, and control are discussed with regard to new system theoretic as well as component/materials advances. In particular, two transmission engineering techniques are modified for use in distribution engineering: state estimation, and locational marginal pricing. The impact of electronic control in distribution systems is discussed. Because education and training have a great impact on distribution engineering, these topics are discussed as well.

Evaluation of time delay effects to wide-area power system stabilizer design

Centralized control using system-wide data has been suggested to enhance the dynamic performance of large interconnected power systems. Because of the distance involved in wide-area interconnections, communication delay cannot be ignored. Long time delay may be detrimental to system stability and may degrade system performance. The time delay tolerance of a centralized controller and the associated performance tradeoff is analyzed using a small gain criterion. Special attention is paid to the choice of weighting functions in a robust control design. As expected, it is found that time delay tolerance decreases when the system bandwidth increases, while the nominal system time-domain performance is concomitantly improved. Several approaches which can maintain a good system performance while increasing the time delay tolerance are suggested and compared. A modern controller design technique, like gain scheduling via linear matrix inequalities, is evaluated for the design of the supervisory power system stabilizer accounting for various time delays.

Impact of increased penetration of photovoltaic generation on power systems

Present renewable portfolio standards are changing power systems by replacing conventional generation with alternate energy resources such as photovoltaic (PV) systems. With the increase in penetration of PV resources, power systems are expected to experience a change in dynamic and operational characteristics. This paper studies the impact of increased penetration of PV systems on static performance as well as transient stability of a large power system, in particular the transmission system. Utility scale and residential rooftop PVs are added to the aforementioned system to replace a portion of conventional generation resources. While steady state voltages are observed under various PV penetration levels, the impact of reduced inertia on transient stability performance is also examined. The studied system is a large test system representing a portion of the Western U.S. interconnection. The simulation results obtained effectively identify both detrimental and beneficial impacts of increased PV penetration both for steady state stability and transient stability performance.

Transient power quality problems analyzed using wavelets

In the literature, wavelet techniques have been proposed for the identification of power system transient signals (e.g., lightning impulse, and capacitor switching transients). In this paper, the wavelet technique is proposed for the analysis of the propagation of transients in power systems. The advantages and disadvantages of the method are discussed and the way in which these analysis methods complement previously reported identification methods is described. An example based on the discretized solution of a differential equation is given.

Applications of the windowed FFT to electric power quality assessment

This paper discusses the application of the windowed fast Fourier transform to electric power quality assessment. The windowed FFT is a time windowed version of the discrete time Fourier transform. The window width may be adjusted and shifted to scan through large volumes of power quality data. Narrow window widths are used for detailed analyses, and wide window widths are used to move rapidly across archived power quality data measurements. The mathematics of the method are discussed and applications are illustrated.

Parallel processing in power systems computation

The availability of parallel processing hardware and software presents an opportunity and a challenge to apply this new computation technology to solve power system problems. The allure of parallel processing is that this technology has the potential to be cost effectively used on computationally intense problems. The objective of this paper is to define the state of the art and identify what the authors see to be the most fertile grounds for future research in parallel processing as applied to power system computation. As always, such projections are risky in a fast changing field, but the authors hope that this paper will be useful to the researchers and practitioners in this growing area.

A Distributed State Estimator Utilizing Synchronized Phasor Measurements

With the creation of balancing authorities by the North American Reliability Council that span large portions of the North American interconnection, and stringent requirements for real time monitoring of power system evolution, faster and more accurate state estimation algorithms that can efficiently handle systems of very large sizes are needed in the present environment. This paper presents a distributed state estimation algorithm suitable for large-scale power systems. Synchronized phasor measurements are applied to aggregate the voltage phase angles of each decomposed subsystem in the distributed state estimation solution. The aggregated state estimation solution is obtained from the distributed solution using a sensitivity analysis based update at chosen boundary buses. Placement of synchronized phasor measurements in the decomposed subsystems is also investigated in this paper. Test results on the IEEE 118-bus test bed are provided

The strategic power infrastructure defense (SPID) system. A conceptual design

A power system can become vulnerable for various reasons, these sources of vulnerability are either internal or external to the infrastructure that comprises the power system. Threats from vulnerability sources that are internal to the civil infrastructure may be reduced by decreasing the probability and severity of occurrence through the improved engineering of related systems. On the other hand, threats from vulnerability sources that are external to the infrastructure may be reduced by decreasing the severity of occurrence. To prevent or reduce catastrophic failures and cascading sequences of events caused by the various sources of vulnerability, the Advanced Power Technologies Consortium is researching ways to revolutionize defense strategies and technologies that will significantly reduce the vulnerability of the power infrastructure. Our vision is a wide-area, intelligent, adaptive protection and control system that empowers future grids by providing critical and extensive information in real time, assessing system vulnerability quickly, and performing timely self-healing and adaptive reconfiguration actions based on system-wide analysis. The proposed system is referred to as the strategic power infrastructure defense (SPID) system. The article discusses the conceptual design of the SPID system and the associated technical challenges. The fundamentally important concept is that the SPID system provides self-healing and adaptive reconfiguration capabilities for power grids based on wide-area system vulnerability assessment. Some experts believe that if 0.4% of the load had been shed for 30 minutes, the widespread power outage in the Western United States on 10 August 1996 could have been avoided. The SPID is intended to identify such load-shedding actions in real time based on proposed vulnerability assessment and protection/control systems.

Latency Viewed as a Stochastic Process and its Impact on Wide Area Power System Control Signals

A method of calculating the communication delay (latency) for measurements and control signals in a power system is shown. The basis of the calculation is a dedicated communication channel for control signals. The time delay calculation is examined using a dynamic equivalent of the Western Electricity Coordinating Council transmission system. The impact on control system response is discussed. The application given is a wide area control system for interarea mode damping. Results demonstrate that control signal latency can degrade the performance of controls in a wide area control system.

Slow-Coherency-Based Controlled Islanding—A Demonstration of the Approach on the August 14, 2003 Blackout Scenario

This paper demonstrates the use of a slow-coherency-based generator grouping algorithm and a graph theoretic approach to form controlled islands as a last resort to prevent cascading outages following large disturbances. The proposed technique is applied to a 30 000-bus, 5000-generator, 2004 summer peak load, Eastern Interconnection data and demonstrated on the August 14, 2003 blackout scenario. Adaptive rate of frequency decline-based load shedding schemes are used in the load rich islands to control frequency. The simulation results presented show the advantage of the proposed method in containing the impact of the disturbance within the islands formed and in preventing the impact of the disturbance from propagating to the rest of the system. This is demonstrated by the significant reduction in line flows in the rest of the system and by improved voltage and relative angle characteristics. Based on the suggestion in the joint U.S.-Canadian task force final report on the blackout, load shedding without any islanding is also performed, and results obtained are compared with the proposed controlled islanding method. The islanding method outperforms the load shedding-only method in reducing the transmission line flows, but both methods have similar effects on voltage and relative angle behavior