An Overview of Power Quality Problems In Transportation and Isolated Power Systems

1. Power Quality on Transportation and Isolated Systems (Panel) An Overview of Power Quality Problems In Transportation and Isolated Power Systems Paulo F. Ribeiro Calvin College / BWX Technologies, Inc Grand Rapids, MI USA Vancouver July 18, 2001

2. General Considerations - Power Quality issues associated with isolated, transportation, stand alone, or decentralized power systems are becoming more complex and requiring additional consideration as more advanced generation and load-controlled techniques are utilized. - Due to the typically low inertia and short-circuit levels, frequency/voltage variations, unbalances and harmonics tend to be amplified. - These systems also provide an ideal environment for the investigation of both the nature of the generation and impact of power quality deviations.

3. Definition Isolated, transportation/dedicated, stand-alone or decentralized power systems are systems that by nature (operational necessity or design) have reduced or optimized generation and/or transmission-distribution topologies in order to maintain an adequate/compatible power quality performance / stable and an economically sustainable operation.

4. New Environment - From a utility perspective, the construction and maintenance of ever increasing interconnected grids are becoming both economically and environmentally less attractive. The operational and administrative costs associated with providing power from remote locations may not compensate the gains of bulk production. - Utilities may back away from grid expansion and large scale, centralized generating plants towards decentralized small-scale generation near the load centers. The opportunity to optimize resources and reduce costs can be significant. Moreover, deregulation of the power industry did not run the successful course of the telecommunication industry. These facts have created a new situation in which large scale centralized systems may become less prevalent even in developed countries. - From a utilization perspective (transportation, remote locations, or weak transmission systems), optimization is the objective. Thus, as more advanced generation and load controlled techniques are implemented in order to increase efficiency and reduce costs, the power quality issues isolated or decentralized power systems require more attention.

5. New Conditions and Problems - Relatively low inertia and short-circuit levels system and/or load variations tend to produce higher levels of power quality deviations. - These include harmonics, reactive power supply and voltage regulation, voltage unbalance, and frequency variations. - The current trend toward advanced power electronics (PWM, etc) in connection with renewable sources and electronically controlled loads and power factor correction devices add to the complexity of the system. - For example, isolated systems operating mainly on solar and or wind power plants may have difficulties in maintaining normal system frequency. Also weak or optimized power systems have low tolerance to load unbalance and or variations due to low short-circuit levels.

6. New Modeling and Simulation Requirements - In the past, performance of an isolated power system could be simply and effectively evaluated from simple expressions based on short-circuit levels and generation capacity / load variation parameters. - Presently, the sophistication of the generation and utilization techniques requires a much more detailed analysis. Voltage unbalance can no longer be determined simply by the ratio of the equivalent single-phase load over the short-circuit power, or similarly the voltage variation by the maximum load complex load step variation over the short-circuit power.

7. New Opportunities For Investigation 1 - Evaluating Power Quality Generation, Propagation Mechanisms and Interactions 2 – Evaluating the Impact of PQ Deviations on Sensitive Loads Power quality standards have been established mainly by empirical methods and based on utility systems. 3 - Evaluating Integration of New Technologies and Control Issues. 4 - Evaluating the Adequacy of Power Quality Standards for Isolated Systems.

8. Conclusions • Transportation or isolated power systems provide a unique and valuable way for engineers to better understand the behavior and determine better models for describing and predicting the performance of these common types of power systems. • This knowledge will enhance our understanding of control, interaction and power quality issues as new generation and utilization technologies make isolated, stand alone, decentralized, or better defined optimized systems, more and more complex. This knowledge could also be used to help better predict, analyze and control power quality issues in large utility systems. • Other papers on this panel session will develop some of the details related to the new problems encountered with isolated power systems and the integration of technologies, monitoring, modeling and simulation.