The understanding of the word “phase” has changed over the years, and power engineers in particul... more The understanding of the word “phase” has changed over the years, and power engineers in particular have a different understanding than some others. The matter was examined in a 1946 paper by the Dutch engineer Balth. van der Pol. In the paper, he highlighted a problem with the ordinary definition, but he did not explain it in detail. In our work with phasor measurement units, we have encountered the problem. This paper explains what is going on, and examines ways around it. We examine the question of testing devices such as phasor measurement units, and show that some workers have failed to observe the effects of what we call the “van der Pol problem.” It is suggested that the PMU standard be amended to allow PMUs to show that they can perform well under changing conditions.
The power grid is a large and complex system. The system becomes larger and more complex daily. D... more The power grid is a large and complex system. The system becomes larger and more complex daily. Distributed energy resources and a more active customer role are factors adding to the complexity. This complicated system is operated by a combination of human operators and automation. Effective control of the power grid requires an increasing amount of automation to support system operators. The need for more support from automation can only increase as operational complexity increases.Actions in controlling the system are entirely dependent on the results of measurements. Measurements inform decisions at all scales. How much trust can be placed in the measurements is essentially an unknown factor. North American Electric Reliability Corporation has generated reports showing that procedures and models have not always worked as expected. Part of the problem lies in the fact that system events can distort signal waveforms. Another part of the problem is that events taking place outside the control area of an operator can affect measured results. The companies involved, and their regulators, have had to change their requirements and guidelines.High “accuracy” measurements are available for most quantities of interest, but the problems are related to trustworthiness, rather than “accuracy.” Accuracy is established for a device within a controlled environment, where a “true value” can be estimated. Real-world conditions can be vastly different. The instrument may provide accurate output according to its specifications, but the measurement might not represent reality because what is happening in the real world is outside the bounds of these specifications. That is a problem that demands a solution. The crux of the matter is this: a real-world measurement’s usefulness as a decision-making aid is related to how believable the measurement is, and not to how accurate the owner’s manual says the instrument is. The concept of “uncertainty” that metrologists have refined over the last few decades is a statistical process that predicts the dispersion of future results. Such a measure is virtually meaningless for real-time power system use. The properties of the power system are not stationary for long periods. A low-quality result can lead to a bad decision, because power system measurements presently lack any kind of real-time “trustworthiness connection.”The signal model generally used in the electric power industry is that the voltages and currents are well-represented by mathematical sinusoids. Given that starting point, we describe two trust metrics that provide verifiable links to the real-time system being measured. The metrics capture any mismatch between the instrument measurement model and the actual signal. Our trust-awareness metrics can lead to ways to develop more robust operating models in the power system environment. Every measurement result is reported with an associated real-time trust (or no-trust) metric, allowing the user (whether human or not) to assess the usefulness of the result. It is, of course, up to the user to determine how a low-quality result should be used in decision-making. Examples of real-time trust metric calculations during real power system events are provided, with evaluation for application in utility user scenarios.
The success of digital instruments seems sometimes to founder when it comes to frequency measurem... more The success of digital instruments seems sometimes to founder when it comes to frequency measurement. Measurement science has developed certain broad principles over the centuries. They are so deep-rooted they are sometimes overlooked. The paper defines measurement largely by elucidating some of these broad principles, and defines frequency, a word subject to much interpretation, as a mathematical entity. Methods of measuring frequency are discussed. An example of the behavior of frequency during a fault, measured in accordance with all the basic principles, is given. The results are not particularly useful. Methods of improving the usefulness are discussed, but may violate some of the basic principles. In essence, “frequency” may not be the best measurand for a signal obtained during a fault.
The conceptual entity that metrologists term the measurand is a model selected to represent the p... more The conceptual entity that metrologists term the measurand is a model selected to represent the physical entity being measured. In a world of digital measurements, it should be defined first mathematically, and only then put into words. Human linguistic processes lack the precision required when all we do is use labels. In this paper, reactive power and frequency are used as examples. The act of measurement finds the values of the coefficients of the model. In other words, it solves an equation. In a digital instrument, information about the quality of the fit between the physical entity being measured and the conceptual model is often available. In essence the instrument can comment on the selection of the model. This comment should be reported as part of the statement of the result of the measurement, along with the declared value and the uncertainty.
2021 IEEE Power & Energy Society General Meeting (PESGM), 2021
Continental level power system interconnections using a High Voltage direct current (HVDC) transm... more Continental level power system interconnections using a High Voltage direct current (HVDC) transmission lines have been considered to bring economic benefits such as interregional power exchange. This paper describes the modeling process and studies the technical benefits of having multiple HVDC lines, including a grid of HVDC lines (macrogrid) configuration, connecting the North American Eastern and Western electric power interconnections. The models developed provide steady state and stability analysis for multiple HVDC overlay topologies and provide technical benefit analysis in terms of frequency response and congestions management. The paper also provides a comparison of different HVDC topologies performance and their grid support in case of major disturbances.
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018
Fitting has been applied to the problem of making the measurements made by a phasor measurement u... more Fitting has been applied to the problem of making the measurements made by a phasor measurement unit. In this paper, results are presented from tests of a phasor measurement unit tested using a synthetic digital signal whose properties are well known and characterized. Because of this test method, the characteristics of the analog front-end and the A/D converter stage are bypassed, allowing the performance of the measurement algorithm to be explored. The PMU is tested according to some of the tests defined in the IEEE C37.118.1 standard, and some more stringent tests. It is shown that the system gives results with errors considerably smaller than the standard requirements for these static and dynamic tests. In addition, some results from point-on-wave recordings made by digital fault recorders are given.
2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE), 2017
It is generally understood that in a (digital) measuring system, attention must be paid to the cr... more It is generally understood that in a (digital) measuring system, attention must be paid to the criterion usually identified with the name Nyquist. The paper shows that there is no such a priori requirement. The observations of Nyquist are examined: some may seem unfamiliar. Sampling and measurement are described as different activities in the quest of information retrieval. A link to Information Theory is discussed.
This paper presents a Synchronized Phasor Measurement Unit (PMU) based controller to support the ... more This paper presents a Synchronized Phasor Measurement Unit (PMU) based controller to support the coordination and operation of a high-capacity high-voltage direct current (HVDC) macrogrid transmission for the continental US. The proposed controller allows for optimal scheduling of each segment of the multi-terminal HVDC network under normal and contingent conditions, while considering minimum levels of frequency response requirements. The performance of the proposed controller is tested on a 100,222-bus representation of the US Eastern and Western interconnections. Results show that a centralized PMU-based controller improves the frequency nadir of the HVDC macrogrid under contingency conditions by 25.9%. Furthermore, the primary frequency response (PFR) of the HVDC macrogrid is increased by 33.4%. The performance of each interconnection under the largest credible contingency conditions is also discussed.
The understanding of the word “phase” has changed over the years, and power engineers in particul... more The understanding of the word “phase” has changed over the years, and power engineers in particular have a different understanding than some others. The matter was examined in a 1946 paper by the Dutch engineer Balth. van der Pol. In the paper, he highlighted a problem with the ordinary definition, but he did not explain it in detail. In our work with phasor measurement units, we have encountered the problem. This paper explains what is going on, and examines ways around it. We examine the question of testing devices such as phasor measurement units, and show that some workers have failed to observe the effects of what we call the “van der Pol problem.” It is suggested that the PMU standard be amended to allow PMUs to show that they can perform well under changing conditions.
The power grid is a large and complex system. The system becomes larger and more complex daily. D... more The power grid is a large and complex system. The system becomes larger and more complex daily. Distributed energy resources and a more active customer role are factors adding to the complexity. This complicated system is operated by a combination of human operators and automation. Effective control of the power grid requires an increasing amount of automation to support system operators. The need for more support from automation can only increase as operational complexity increases.Actions in controlling the system are entirely dependent on the results of measurements. Measurements inform decisions at all scales. How much trust can be placed in the measurements is essentially an unknown factor. North American Electric Reliability Corporation has generated reports showing that procedures and models have not always worked as expected. Part of the problem lies in the fact that system events can distort signal waveforms. Another part of the problem is that events taking place outside the control area of an operator can affect measured results. The companies involved, and their regulators, have had to change their requirements and guidelines.High “accuracy” measurements are available for most quantities of interest, but the problems are related to trustworthiness, rather than “accuracy.” Accuracy is established for a device within a controlled environment, where a “true value” can be estimated. Real-world conditions can be vastly different. The instrument may provide accurate output according to its specifications, but the measurement might not represent reality because what is happening in the real world is outside the bounds of these specifications. That is a problem that demands a solution. The crux of the matter is this: a real-world measurement’s usefulness as a decision-making aid is related to how believable the measurement is, and not to how accurate the owner’s manual says the instrument is. The concept of “uncertainty” that metrologists have refined over the last few decades is a statistical process that predicts the dispersion of future results. Such a measure is virtually meaningless for real-time power system use. The properties of the power system are not stationary for long periods. A low-quality result can lead to a bad decision, because power system measurements presently lack any kind of real-time “trustworthiness connection.”The signal model generally used in the electric power industry is that the voltages and currents are well-represented by mathematical sinusoids. Given that starting point, we describe two trust metrics that provide verifiable links to the real-time system being measured. The metrics capture any mismatch between the instrument measurement model and the actual signal. Our trust-awareness metrics can lead to ways to develop more robust operating models in the power system environment. Every measurement result is reported with an associated real-time trust (or no-trust) metric, allowing the user (whether human or not) to assess the usefulness of the result. It is, of course, up to the user to determine how a low-quality result should be used in decision-making. Examples of real-time trust metric calculations during real power system events are provided, with evaluation for application in utility user scenarios.
The success of digital instruments seems sometimes to founder when it comes to frequency measurem... more The success of digital instruments seems sometimes to founder when it comes to frequency measurement. Measurement science has developed certain broad principles over the centuries. They are so deep-rooted they are sometimes overlooked. The paper defines measurement largely by elucidating some of these broad principles, and defines frequency, a word subject to much interpretation, as a mathematical entity. Methods of measuring frequency are discussed. An example of the behavior of frequency during a fault, measured in accordance with all the basic principles, is given. The results are not particularly useful. Methods of improving the usefulness are discussed, but may violate some of the basic principles. In essence, “frequency” may not be the best measurand for a signal obtained during a fault.
The conceptual entity that metrologists term the measurand is a model selected to represent the p... more The conceptual entity that metrologists term the measurand is a model selected to represent the physical entity being measured. In a world of digital measurements, it should be defined first mathematically, and only then put into words. Human linguistic processes lack the precision required when all we do is use labels. In this paper, reactive power and frequency are used as examples. The act of measurement finds the values of the coefficients of the model. In other words, it solves an equation. In a digital instrument, information about the quality of the fit between the physical entity being measured and the conceptual model is often available. In essence the instrument can comment on the selection of the model. This comment should be reported as part of the statement of the result of the measurement, along with the declared value and the uncertainty.
2021 IEEE Power & Energy Society General Meeting (PESGM), 2021
Continental level power system interconnections using a High Voltage direct current (HVDC) transm... more Continental level power system interconnections using a High Voltage direct current (HVDC) transmission lines have been considered to bring economic benefits such as interregional power exchange. This paper describes the modeling process and studies the technical benefits of having multiple HVDC lines, including a grid of HVDC lines (macrogrid) configuration, connecting the North American Eastern and Western electric power interconnections. The models developed provide steady state and stability analysis for multiple HVDC overlay topologies and provide technical benefit analysis in terms of frequency response and congestions management. The paper also provides a comparison of different HVDC topologies performance and their grid support in case of major disturbances.
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018
Fitting has been applied to the problem of making the measurements made by a phasor measurement u... more Fitting has been applied to the problem of making the measurements made by a phasor measurement unit. In this paper, results are presented from tests of a phasor measurement unit tested using a synthetic digital signal whose properties are well known and characterized. Because of this test method, the characteristics of the analog front-end and the A/D converter stage are bypassed, allowing the performance of the measurement algorithm to be explored. The PMU is tested according to some of the tests defined in the IEEE C37.118.1 standard, and some more stringent tests. It is shown that the system gives results with errors considerably smaller than the standard requirements for these static and dynamic tests. In addition, some results from point-on-wave recordings made by digital fault recorders are given.
2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE), 2017
It is generally understood that in a (digital) measuring system, attention must be paid to the cr... more It is generally understood that in a (digital) measuring system, attention must be paid to the criterion usually identified with the name Nyquist. The paper shows that there is no such a priori requirement. The observations of Nyquist are examined: some may seem unfamiliar. Sampling and measurement are described as different activities in the quest of information retrieval. A link to Information Theory is discussed.
This paper presents a Synchronized Phasor Measurement Unit (PMU) based controller to support the ... more This paper presents a Synchronized Phasor Measurement Unit (PMU) based controller to support the coordination and operation of a high-capacity high-voltage direct current (HVDC) macrogrid transmission for the continental US. The proposed controller allows for optimal scheduling of each segment of the multi-terminal HVDC network under normal and contingent conditions, while considering minimum levels of frequency response requirements. The performance of the proposed controller is tested on a 100,222-bus representation of the US Eastern and Western interconnections. Results show that a centralized PMU-based controller improves the frequency nadir of the HVDC macrogrid under contingency conditions by 25.9%. Furthermore, the primary frequency response (PFR) of the HVDC macrogrid is increased by 33.4%. The performance of each interconnection under the largest credible contingency conditions is also discussed.
Uploads
Papers by Harold Kirkham