Review of Advancements in Synchrophasor Measurement Applications

Introduction

Utilities around the world who have adopted the synchrophasor technology reported numerous tangible benefits in reliability, asset utilization and power system efficiency. Many utilities have integrated the synchrophasor measurements systems along with existing Supervisory Control and Data Acquisition (SCADA) and Energy Management Systems (EMS). In response to the industry needs, the diversity of synchrophasor applications have grown significantly, and many new applications such as renewable energy generation monitoring, system inertia monitoring, and grid code compliance monitoring are emerging. There have been significant developments in wide-area protection and wide-area control applications since the publication of previous CIGRE reports in phasor measurement unit (PMU) applications.  As a result, there is a wealth of real-world experience in deployment and integration of PMUs and synchrophasor systems. Despite the work of WG C2.18 leading to the publication of TB 917 focused on operator decision support systems, there was a need to share the broader developments of the measurement technology and standards, practical experiences, best practices, and latest research. As a result, CIGRE created a joint WG to explore such advances, and the terms of reference for JWG C4/C2.62 was approved on March 28th, 2021. The objectives of this Joint Working Group were:

1. To provide an updated overview of synchrophasor technology including standard updates.
2. To provide an updated view of industry and academia experience on the concentration, archiving, and use of PMU data.
3. To describe emerging applications and any technology gaps such as high dependency on reliable telecommunication, precise time synchronisation, signal latency, etc. requiring further research and development.
4. To discuss the end-users’ experiences of deploying synchrophasor measurement systems and applications and elaborate additional specially tailored applications for enhancing secure power system operation.
5. Elaborate and deliver application examples for new specific PMU applications.

The Joint Working Group was started with 31 members representing 15 countries. During the course of its activities, in addition to the formally selected members, many other experts from the utilities, manufacturers and academia contributed to the efforts of the Working Group.

Scope and Methodology

The scope of the Working Group was to provide an updated review of specific PMU applications including:

• Detection of sub-synchronous resonance, very low frequency governor modes, control modes, and oscillations source location.
• Improved situational awareness, synchrophasor-enhanced state estimation including linear, distributed, and dynamic state estimation.
• Voltage and transient stability instability detection
• On-line and off-line model parameter identification for generators, loads, lines, and systems equivalents.
• Emerging applications such as grid code compliance monitoring such as monitoring of voltage and frequency control, fault ride through performance, etc., wide area protection and control systems including synchrophasor based backup protection, special protection systems, enhancements to FACTS and HVDC control.

The Working Group reviewed published literature and solicited the end-users’ experiences of equipment and software systems used to implement synchrophasor applications. The discussions included various practical issues encountered and solutions developed to overcome these issues.

Content of the Review

The content of the review is presented in 7 chapters.

Chapter 1 presents a brief background, motivation and scope of review. 

Chapter 2 presents a review of the recent advancements in the synchrophasor technology and standards. Highlights include the unified IEC and IEEE synchrophasor measurement standards, release of new IEEE standard on streaming telemetry transport protocol (STTP), updates to the IEEE phasor data concentrator standards and the IEEE guide on synchronization, calibration, testing and installation of PMUs. The basic measurement technology remains the same, but higher standard reporting rates will enable new types of applications, especially in the areas of renewable energy integration and wide area protection. The use of PMUs for distribution applications in the field is still emerging and there is an active IEEE/PSRC Working Group (WG C41) that attempts to identify the requirements of potential distribution applications and enhancements required to the synchrophasor measurement standards.

Chapter 3 of the technical brochure reviewed recent trends in system architecture, data integration frameworks and protocols. Vendors and utilities are experienced with integration of information from PMUs with other sources such as SCADA systems, but architecture used, and protocols employed are not uniform. The system architectures are often influenced by the existing infrastructure, and protocols. When using synchrophasor data for critical applications, data validation is essential. Despite the availability of various data validation techniques, challenges remain in validating large volumes of PMU data in real-time for using in wide area monitoring and control systems. Several examples of existing system architectures from utilities are included in this chapter.

Chapter 4 examines the synchrophasor applications that are operationally deployed in the industry. Synchrophasor-based visualization tools are increasingly being incorporated in control centers for enhanced situational awareness. Enhancing state estimation with PMU measurements is well-established and the technology is progressing towards linear state estimation. Oscillations and voltage stability monitoring applications are widely deployed, and the recent advancements include enhanced capabilities in oscillation source location. Use of synchrophasor data for model validation, load or line parameter estimation, controller tuning, and post event analysis is widely adopted across the industry. Many new applications motivated by the issues related to large-scale integration of inverter-based resources including intermittent renewable generation and HVDC systems are emerging. Several examples of applications like grid code compliance monitoring, inertia and dynamic response monitoring are presented. The chapter also reports examples of using wide area measurements in closed loop oscillation damping control and wide area protection systems.    

Chapter 5 covers potential applications that are not yet operationally deployed. The maturity of many applications that creatively use synchrophasor measurements range from initial algorithms to prototypes or field-tested applications. While it is impossible to cover all proposed applications, Chapter 5 captures a representative cross section of examples. Several applications such as synchrophasor based fault location and fast frequency control have been demonstrated in the field and can be considered as approaching the stage of field deployment. Certain applications such as dynamic state estimation are ready to be applied in limited contexts, for example to estimate parameters or validate dynamic models. Synchrophasor based dynamic line rating is another promising application but needs overcoming some challenges such as inability to recognize the weakest sections. Many critical real-time applications such as transient and short-term voltage stability assessment, asset and system protection have been demonstrated in simulated environments. Many such applications tend to use machine learning based algorithms to solve problems that are intractable with traditional model-based approaches. The concept of digital twins is being embraced by the power industry and synchrophasor measurements can play a major role in the development of digital twins. A novel example of utilizing synchrophasor infrastructure for monitoring geomagnetic disturbances is also reported.

In Chapter 6, trends and technologies that support the needs of future grids are discussed. The complexity of the future electric power systems is expected to increase due to renewable energy integration, decentralized power generation, and the addition of electric vehicles. High speed wide area monitoring can assist in early detection of grid anomalies and possible threats, which could range from equipment failures to cyber-attacks, and will be essential for ensuring grid stability and security. The key technologies that can enable futuristic applications include the cloud based synchrophasor architectures and applications of artificial intelligence and machine learning. With increasing use of power electronic converters at both generation and loads, adequacy of phasors for effectively monitoring the future grids is questioned. The notion of synchronized waveform monitoring or continuous point on wave monitoring is emerging. Cybersecurity concerns, standardization and interoperability issues, dearth of applications assisting large scale integration of renewable energy systems, and lack of comprehensive methods for validating applications using AI and ML techniques are identified as major technology gaps. This chapter also presents a list of areas for further research. 

Conclusions and Recommendations

The synchrophasor measurement technology is maturing at a fast rate and the related standards cover most aspects of accuracy and interoperability. One area that needs further effort is the distribution system applications. Thus, further research and development work related to synchrophasor applications for distribution systems, designing measurement devices tailored to requirements in distribution systems, and establishment of standards for distribution PMUs is recommended.

The synchrophasor measurement system architectures are often influenced by the existing infrastructure and protocols and therefore differs from utility to utility. Further research is recommended in the area of designing futuristic system architectures to exploit recent developments such as software defined networking and cloud-edge computing. The future system architectures must be able to combine the SCADA systems and synchrophasor measurements into a unified framework in the control centre hosting multivariate spatio-temporal data including non-electrical data for various data-driven applications.

Data validation and quality assurance have become essential as the PMU data being increasingly applied in critical and real-time applications. Therefore, further research is recommended in developing techniques, possibly exploiting the recent advancements in data science and machine learning, for validating large volumes of high-speed data, managing data with varying quality levels, and adapting to dynamic power system changes.

While the industry has become comfortable with monitoring and off-line applications, there is still shortage of real-world examples of using synchrophasor measurements in closed loop control and protection applications. There is a need to disseminate and share the experiences and lessons learned from such applications to establish the confidence of the industry.

There are many new applications that creatively use synchrophasor measurements. Big-data analytics are necessary to automatically interpret large archives of synchrophasor data. Researchers have shown variety of potential applications where PMU measurements can be used with machine learning to develop solutions to complex problems. It is recommended to direct further research toward real-time implementation and pilot testing of these new applications. Furthermore, methodologies need to be developed to assess and ensure the performance of applications that use machine learning.   

In summary, the field of synchrophasor measurement based wide area monitoring, protection and control have significantly advanced recently, and the synchrophasor technology is expected to play a crucial role in the transformation of electricity grids to achieve net zero emission targets.