- May 5, 2022 7:22 pm GMT
Historically, one of the energy industry’s least examined concepts has been the issue of power quality (PQ). PQ, or more specifically a PQ disturbance, is defined by IEEE (Institute of Electrical and Electronics Engineers) as any change in the power (voltage, current, or frequency) that interferes with normal operation of electrical equipment. In the past 50 years, PQ has grown to address customer technologies and an increasingly complex power grid. Today, PQ is recognized as a fundamental component of grid performance, energy company economics, and customer satisfaction.
What changed to increase PQ awareness and research?
Until the 1970s, most electrical loads were linear and could ride through most grid voltage and current variations. The emergence of microprocessors, process controls, and other equipment sensitive to voltage and current variations, as well as equipment that caused PQ variations, resulted in a new technology discipline focused on the compatibility between the grid and the devices connected to it. This concept of compatibility is at the heart of PQ issues and research.
While perhaps not top of mind for consumers, PQ concerns can impact any customer. For instance, voltage variations caused by large load variations, such as when motors start or when arc furnaces are in use, may cause customers’ lights to flicker over a wide area. While light flickers are not as common with use of LED lights, shot term reductions in voltage (i.e., voltage sags, the most common cause of poor PQ) occurring over wide areas when there is a fault on the grid can potentially affect a diverse range of equipment and processes. Consumer electronic devices, like televisions, computers, and now electric vehicle chargers, can affect both the grid and other customers by causing harmonic distortion (voltage and current variations due to frequency changes withing the electrical distribution system).
Since the 1980s, EPRI’s PQ research program, in coordination with utilities and global research institutions, has studied these issues through detailed laboratory and field investigations. For more than 40 years, EPRI’s PQ research has helped raise awareness of this important topic, while providing solutions to utilities.
Overview of Highlights in PQ Research
In evaluating the current state of PQ research, it is worth looking at the history of PQ research and related activities, particularly as new compatibility challenges emerge. A small sample of key PQ innovators that have paved the way for the improved compatibility that we have today include:
- Francois Martzloff: Characterized transient voltage concerns, how to measure them, and how to protect equipment from them. Identified and assembled industry leading references on surge protection.
- Roger Dugan, Mack Grady, Erich Gunther, Mark Halpin: Led advances in harmonic analysis methods and standards for evaluating compatibility.
- Tom Key, Math Bollen, Dan Sabin: CBEMA power acceptability curve (Key); voltage sags (Bollen); analytical tools for analyzing PQ measurements (Sabin).
(A personal note: I am the co-author, with Roger Dugan and Surya Santoso, of Electrical Power Systems Quality, now in its third edition, the leading textbook on PQ and compatibility issues.)
In examining historical PQ developments and events, lessons learned may be important when looking for solutions to current and future PQ issues.
For example, many current PQ compatibility challenges are the result of the increasingly complex grid environment associated with new technologies and system configurations associated with the energy transition. Some of the most important areas of investigation today include:
- Voltage regulation with increased penetration of distributed resources
- Hosting capacity—the ability of the power system to function properly with more and more devices that may affect quality or reliability
- Electrification impacts (electric vehicle charging, heat pumps)
- Energy storage
- Higher frequency harmonics (supraharmonics)
- Monitoring everywhere, artificial intelligence
- Improved power supplies and power electronics
- Importance of communications infrastructure
PQ’s Future as Global Electrification Grows
PQ research is driven by digitization in equipment and processes, customer needs and economic impacts, standards development, and a changing power grid environment. Continued use of computers, inverters, and microprocessors potentially will introduce new challenges and influence research pathways in the future.
Integrating distributed energy resources (DER) and increased system complexity remains a core PQ challenge unique to each local system as the grid continues to evolve. Ongoing integration of solar PV, electric vehicle chargers, and other inverter-connected devices also may introduce new PQ issues as economy-wide electrification efforts increase.
With possibly millions of electricity dependent devices operating throughout the grid, it is important to consider systemwide PQ for the reliable operation of these devices and to minimize PQ impacts on the grid. Updated and new standards, such as IEEE 1547 and IEEE P2800, provide guidelines on how DER and inverter-based resources may minimize impact to PQ on the grid, including resources interconnecting with transmission systems.
However, instead of reacting to PQ issues, a systemwide, data-driven approach may aid in proactively identifying PQ issues that could lead to major incidents. Artificial intelligence and machine learning using large amounts of data could potentially bolster analysis programs to generate localized solutions. Uninterruptable power supply and battery storage also may have future value to balance dips in generation and, potentially, for voltage regulation and PQ in general.
Energy companies, manufacturers, vendors, researchers, and customers are working together to find mutual understanding and solutions beneficial to all stakeholders. EPRI’s Program 1: Power Quality is helping to continue these efforts, with research ongoing to anticipate and address PQ issues in the changing grid environment. Read the entire EPRI report from which this article was excerpted here: A History of Power Quality.
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