A. P. Sakis Meliopoulos - Academia.edu (original) (raw)

Papers by A. P. Sakis Meliopoulos

Proceedings of the ... Annual Hawaii International Conference on System Sciences, 2017

Recent technological advances in protection, control and optimization are enabling a more automat... more Recent technological advances in protection, control and optimization are enabling a more automated power system. This paper proposes the use of these technologies towards an integrated and seamless infrastructure for protection, control and operation. This infrastructure is the basis for accommodating and providing robust solutions to new problems arising from the integration of renewables, namely more uncertainty and steeper ramp rates. At the lower level we propose a dynamic state estimation of a protection zone (EBP) for the purpose of providing protection for the zone. The estimation based protection (EBP) provides the real time dynamic model of the zone as well as the real time operating conditions. Since protection is ubiquitous, it can cover the full system. We assume that GPS synchronization of the EBP is available providing accurate time tags for the real time model and operating conditions. The real time model and operating conditions can extent from the "turbine to the toaster". We propose a methodology for automatically constructing the power system state locally and centrally at the control center with distributed controls as well as centralized controls depending on the application. For example, the centralized system wide real time model is used to perform system optimization functions, and then send commands back through the same communication structure to specific power system components. Since protection is ubiquitous and the modern power system has several layers of communication infrastructure, the proposed approach is realizable with very small investment. The availability of the real time dynamic model and state locally and centrally enables the seamless integration of applications. Three applications are discussed in the paper: (a) settingless protection, (b) voltage/var control and (c) feeder load flexibility scheduling. The proposed approach and infrastructure can form the basis for the next generation of Energy Management Systems.

2019 IEEE Power & Energy Society General Meeting (PESGM)

The introduction of new data acquisition systems, i.e., merging units, provides more accurate dat... more The introduction of new data acquisition systems, i.e., merging units, provides more accurate data to protection schemes enabling faster and more reliable protection. This paper presents an object-oriented dynamic state estimation based protection (DSEBP) scheme on a protection unit using the measurements obtained from merging units. The DSEBP uses instantaneous measurements and adopts a detailed and object-oriented model that represents the protection zone, which may comprise two or more devices, and performs dynamic state estimation to determine whether an internal fault has occurred. The dynamic state estimation provides the best estimate of the protection zone states as well as the probability that the un-faulted protection zone model fits the measurements. When the probability drops below a certain threshold, a trip decision is issued with a user selected time delay. The DSEBP requires few settings (e.g., trip delay time, etc.) and is applicable to any combination of devices in the protection zone. This paper uses an example consisting of a transformer and a cable in a substation to substantiate the effectiveness of this method.

2022 17th International Conference on Probabilistic Methods Applied to Power Systems (PMAPS)

Composite Power System Reliability is defined as the computational procedure that quantifies the ... more Composite Power System Reliability is defined as the computational procedure that quantifies the probability that the power system will perform the function of delivering electric power to customers adequately, on a continuous basis and with an acceptable quality. This definition leaves many details undefined and exemplifies the ambiguity in reliability analysis. The increasing deployment of wind and PV creates additional uncertainties that make reliability analysis a rather complex issue. Because of increased uncertainty the need for composite reliability analysis and utilization of results in power system planning is critical. New approaches are emerging for dealing with these problems from the operational point of view, including demand response programs, tapping on customer and distributed resource flexibility and new control approaches. The key question to be addressed is: how the new operational paradigms affect composite power system reliability. This paper presents the ongoing work of the IEEE Composite System Reliability Task Force of the IEEE PES Reliability, Risk, Probability Application (RRPA) Subcommittee.

2018 North American Power Symposium (NAPS), 2018

Deployment of distributed energy resources (DERs) introduces more dynamics to the distribution sy... more Deployment of distributed energy resources (DERs) introduces more dynamics to the distribution system, and brings system operators more challenges in monitoring and controlling the distribution system. These challenges can be addressed by developing methods for real time extraction of the operating state and model of the system, that is advanced state estimators for distribution systems with high penetration of DERs. This paper presents an object-oriented Distributed Quasi-Dynamic State Estimator (DQDSE) that employs three-phase detailed models and enables data from sensors to be streamed and used by the DQDSE. Based on three-phase detailed quasi-dynamic models that track slow dynamics (e.g., controls of power electronics, electromechanical transients of motors, etc.), DQDSE forms network measurement model by using networkwise measurements, performs quasi-dynamic state estimation, and provides the best estimate of the distribution system states. The proposed DQDSE has the following advantages: (1) detailed modeling approach ensures accurate results even when accommodating unbalanced and asymmetric systems; (2) the measurement set of DQDSE contains measurements from sensors as well as other measurement types to increase redundancy; (3) the distributed architecture of DQDSE enables fast data processing. The paper presents the method via an illustrative example that substantiates the effectiveness of DQDSE. Index Terms-distributed quasi-dynamic state estimation, distributed energy resources, object-oriented, three-phase detailed model This work is partially supported by the Department of Energy and Sandia National Laboratories. Their support is greatly appreciated.

Journal of Electrical Engineering and Technology, 2013

This paper proposes the new adaptive protection algorithm for inverse-time overcurrent relays (OC... more This paper proposes the new adaptive protection algorithm for inverse-time overcurrent relays (OCRs) to ensure their proper operating time and protective coordination. The application of the proposed algorithm requires digital protection relays with microcontroller and memory. The operating parameters of digital OCRs are adjusted based on the available data whenever system conditions (system with distributed generation (DG)) vary. Moreover, it can reduce the calculation time required to determine the operating parameters for achieving its purpose. To verify its effectiveness, several case studies are performed in time-domain simulation. The results show that the proposed adaptive protection algorithm can keep the proper operating time and provide the protective coordination time interval with fast response.

IEEE Power Engineering Society General Meeting, 2004.

Control room operators are faced with frequent security-economy decision-making situations necess... more Control room operators are faced with frequent security-economy decision-making situations necessitated by stressed system operating conditions, and there is increased need for securityeconomy decision-support tools. Although probabilistic methods are promising in this regard, they have been mainly used in planning environments. This task force paper explores their use for operational decision-making, comparing them to the more traditional deterministic approach. Two examples are used to facilitate this comparison via overload and low voltage security assessment to identify secure regions of operation for a small 5-bus system and for the IEEE Reliability Test System. The results of this comparison show that the probabilistic approach offers several inherent advantages.

IEEE Transactions on Smart Grid, 2013

This paper proposes an advanced distribution management system (DMS) that a) monitors each compon... more This paper proposes an advanced distribution management system (DMS) that a) monitors each component and performs protection functions using a dynamic state estimation, b) the estimated states are transmitted to the DMS where the real time model of the entire feeder is synthesized, c) uses the real time model to perform upper level optimization (operations planning) and lower level optimization (real time control) via a hierarchical optimization procedure; and d) applies proper controls to operate the system at optimal points. The proposed approach for protection, operations planning, and real time control of the system provides the infrastructure for additional important applications. As an example, the paper presents a novel application for monitoring available reserves from all resources in the system. We propose the concept of Reserve-O-Meter that monitors in real time the available reserves from all resources (utility and customer owned).

IEEE Transactions on Power Systems, 2001

Restructuring of the power industry worldwide has brought the issue of market competitiveness to ... more Restructuring of the power industry worldwide has brought the issue of market competitiveness to the forefront. While "vertical" market power has been limited by disaggregating generation and transmission, nondiscriminatory access to the transmission system by power suppliers, and the creation of the independent system operator (ISO), "horizontal" and localized market power still survives. In the last few years, the issue of a small number of generators exercising market power has received a great deal of attention, and much has been published on how to identify and mitigate such abuse by market management measures. This paper focuses on the analysis and mitigation of market power in electricity supply.

2017 North American Power Symposium (NAPS), 2017

The distribution system always contains GPSsynchronized data and non-synchronized data. The appli... more The distribution system always contains GPSsynchronized data and non-synchronized data. The application of both types of data in state estimation increases redundancy of the measurements and accuracy of the estimated states. Using both GPS-synchronized and non-synchronized data, this paper introduces object-oriented distributed quasi-dynamic state estimation (DQDSE), that is, substation-level quasi-dynamic state estimation (QSE) that tracks slow dynamics (e.g., electromechanical transients) while neglecting fast electromagnetic transients. DQDSE offers an efficient and practical way of performing state estimation for subsystems with phasor measurement units and other meters. It also transmits generated results to the control center for system automation and control. The advantages of DQDSE follow: (1) It uses a highly accurate system model, (2) it deals with unbalanced operating conditions, and (3) it uses local measurements to reduce state estimation computation time. The demonstrative example verifies the effectiveness of DQDSE.

2014 47th Hawaii International Conference on System Sciences, 2014

The objectives of smart grid and grid modernization are to increase automation and seamlessly int... more The objectives of smart grid and grid modernization are to increase automation and seamlessly integrate data, models, protection, optimization and control of the power grid. This effort is affected by technological advances. One such technology is the numerical relay which has increased its domination to the point that today has almost completely displaced electromechanical and solid state relays and the most recent technology of merging units that has separated the data acquisition function from protective relays and SCADA systems. The capabilities of the numerical relays are not fully utilized today; specifically, by and large, they simply mimic the logics that were developed for the electromechanical relays but with much more flexibility. Recent developments towards substation automation are utilizing the numerical relays for SCADA, communications and in general an integrated system for protection and control. These approaches indicate the recognition that numerical relays offer much more than simply mimicking protection functions of the past. They also offer the ability to form the basic infrastructure towards a fully automated power system, the subject of this paper. In previous work, we presented a new protection scheme that is a generalization of differential protection. The approach is based on dynamic state estimation. Specifically, the protection scheme is based on continuously monitoring terminal voltages and currents of the component and other possible quantities such as tap setting, temperature, etc. as appropriate for the component under protection. The monitored data are utilized in a dynamic state estimation that continuously provides the dynamic state of the component. The dynamic state is then used to determine the health of the component. Tripping or no tripping is decided on the basis of the health of the component. The present paper takes the above concept one step further. Using the dynamic state estimation of a protection zone as the basic technology, it builds an integrated automation system that performs the protection functions, validates models, transmits the models to the control center, integrates monitoring and control, enables optimization and provides automated disturbance playback capabilities. The system provides the infrastructure and real time models for any application along the spatial extend of the power system.

IEEE Transactions on Power Systems, 2021

Dynamic state estimation (DSE) accurately tracks the dynamics of a power system and provides the ... more Dynamic state estimation (DSE) accurately tracks the dynamics of a power system and provides the evolution of the system state in real-time. This paper focuses on the control and protection applications of DSE, comprehensively presenting different facets of control and protection challenges arising in modern power systems. It is demonstrated how these challenges are effectively addressed with DSE-enabled solutions. As precursors to these solutions, reformulation of DSE considering both synchrophasor and sampled value measurements and comprehensive comparisons of DSE and observers have been presented. The usefulness and necessity of DSE based solutions in ensuring system stability, reliable protection and security, and resilience by revamping of control and protection methods are shown through examples, practical applications, and suggestions for further development.

2017 IEEE Power & Energy Society General Meeting

a method for synchronous generator parameter estimation by dynamic state estimation is presented ... more a method for synchronous generator parameter estimation by dynamic state estimation is presented using PMU data. A three phase physically based two-axis generator model with two damper windings is utilized for the dynamic state estimation. Eleven independent parameters are estimated: ten self and mutual inductances of the various windings and the inertia constant. These parameters can be either used for the three phase physically based model or be converted to the usual dq0 synchronous generator model. The proposed method requires time domain three phase sampled data for better estimation accuracy. In the paper, the PMU phasor data with disturbance provided by NERC was converted to three phase sampled data first and then they were fed into the dynamic state estimation. The comparison between the calibrated parameters and the actual parameters provided by NERC is shown to prove the effectiveness of the proposed method. The accuracy of the proposed method can be greatly improved if the three phase sampled value data are provided at the generator three phase terminals, the exciter and the governor.

2016 North American Power Symposium (NAPS)

A dynamic state estimation (DSE) based protection algorithm using weighted least square (WLS) met... more A dynamic state estimation (DSE) based protection algorithm using weighted least square (WLS) method was introduced recently. In this paper, the DSE-based protection algorithm using constraint weighted least squares (CWLS) method is applied to capacitor bank protection. This approach monitors the health status of the capacitor bank by fitting real time measurements to the capacitor bank dynamic model via dynamic state estimation. Virtual measurements are added to the measurements set by considering the physical laws that must be obeyed by the capacitor bank (i.e. KVL, KCL). Virtual measurements can be handled as measurements with high accuracy or as constraints to the dynamic state estimation. The CWLS method treats the virtual measurements as constraints while the WLS method treats them as highly accuracy measurements. Comparison of capacitor bank protection results using unconstraint WLS and CWLS is provided. It is shown that the proposed method can detect internal faults and issue the trip signal correctly The use of CWLS provides a more sensitive protection for capacitor banks.

Proceedings of the Annual Hawaii International Conference on System Sciences, 2020

This paper presents a mixed integer linear program (MILP) to optimally size power and energy of e... more This paper presents a mixed integer linear program (MILP) to optimally size power and energy of energy storage systems (ESSs). The sizing model takes into account conventional generation (CG) operation constraints in addition to seasonal and locational wind speed and solar radiation variations, and variable generation (wind turbine systems (WTSs) and solar cell generators (SCGs)) forced outages. Subsequently, the outcomes of the ESS sizing model are inputted to the probabilistic production method (PCC) to assess the reliability of the integrated system. All aforementioned analyses have been applied to a system with different penetration levels. The method is demonstrated with case studies on a system consisting of 10 CG units and VG penetration levels of 20% and 30%. For each penetration level, ESS sizing is computed and then reliability assessment is performed. PESS Maximum discharge/charge rate of ESS (MW)

Proceedings of the Annual Hawaii International Conference on System Sciences, 2022

Technological advances in electric energy system data acquisition systems, time synchronization, ... more Technological advances in electric energy system data acquisition systems, time synchronization, and cyber assets used in power system substations, distribution systems, and control centers offer new opportunities to dramatically improve the practice of monitoring, protection, control, and operation of the system. We can make the computer based new technologies smarter and more intelligent to fully automate the basic protection and control functions. The challenges posed to the system from the continuous deployment of renewable resources that are typically inverter interface resources require monitoring of the system at much higher rates and development of protection and control systems that can respond in much faster rates than for conventional systems and they are immune to the characteristics of the new system, namely reduced fault currents and suppressed negative and zero sequence components of the fault currents. We propose a new system that provides validated data at fast rates (once per cycle), protective relays that are immune to the effects of inverter interfaced generation, detect anomalies, and enable the continuous operation of relays and other functions even in the presence of hidden failures in instrumentation. This system will enable the operators to meet the challenges posed by the evolving power system and provides robust solutions to the new requirements.

Proceedings of the 33rd Annual Hawaii International Conference on System Sciences

A new tool for computing and visualizing the operation of power system components and systems is ... more A new tool for computing and visualizing the operation of power system components and systems is presented. One component of the tool is a time domain simulator that operates in the background within a multitasking environment. Visualization and animation objects can retrieve data in real time from the time domain simulator and display a detailed picture of a component or system operation. As the system state evolves, the pictures are updated resulting in an animated visualization of the process. The tool has been implemented in a multitasking environment, thus permitting user interaction in real time with the system parameters and immediate reflection of the results in animations and visualizations. Several examples of visualization and animation are presented, including animation of Mho relay operation, visualization of small signal stability, load dynamics and voltage sensitivity and synchronous machine operation.

The performance of electric circuits enclosed in steel conduit or EMT is of great importance for ... more The performance of electric circuits enclosed in steel conduit or EMT is of great importance for the proper operation of industrial and commercial installations as well as the safety of humans in these facilities. This paper presents a comprehensive modeling procedure for these systems and the verification of these models with extensive testing under various loading conditions. The paper presents the mathematics of the approach as well as the testing procedure, test results and verification of the mathematical model. One important parameter in the model is the magnetization characteristics of the various steel raceway materials. The paper presents an elegant and simple procedure to measure the magnetic properties of the various raceway materials. The validated model is used to compute important design parameters, such as maximum permissible lengths and to assess the performance of specific designs. This work updates the results obtained with a similar but less comprehensive previous...

Proceedings of the Annual Hawaii International Conference on System Sciences, 2021

Many power grid applications rely on the timesynchronized measurement data collected by phasor me... more Many power grid applications rely on the timesynchronized measurement data collected by phasor measurement units (PMUs) and or Merging Units (MUs)). The synchronization of data from multiple PMUs and MUs relies on the global positioning system (GPS) to provide the time reference. The civilian GPS receivers used in PMU operate according to the publicly available mechanism. Therefore, attackers can easily generate false GPS signals with low-cost portable devices. During the spoofing attacks, the signal received by the PMUs and MUs is arbitrarily modified by the attacker without being detected, leading to the malfunction of other applications in the power system including transmission line protection. In this paper, we investigate the effect of GPS spoofing attack on transmission line differential protection schemes based on PMUs, including the percentage differential method and alpha-plane protection method. The mis-operation of these relays is observed during GPS spoofing attacks. In addition, we propose a quasi-dynamic stateestimation-based method to detect GPS spoofing attacks, identify the affected PMUs, correct the compromised data, and enable the continuous and reliable operation of the relays. Numerical results show that the proposed method detects the GPS spoofing successfully and the recovered measurement data eliminate the misoperation of line differential protection.

Electric Power Systems Research, 2020

This survey paper discusses the fundamentals of power systems modelling in the presence of large ... more This survey paper discusses the fundamentals of power systems modelling in the presence of large amounts of converter-interfaced generation (CIG). By referring to real-life events characterised by anomalous dynamics associated to the presence of CIG, the concepts of narrow versus broad band signals are first recalled along with the limitation of the meaning of apparent power, power factor and reactive power. In this regard, the adequacy of the phasor representation of voltages and currents waveforms is thoroughly discussed. Then, with respect to the central subject of control of power converters, a revised definition of grid-following and grid-forming converters is provided along with a thorough discussion of their associated controls and a comprehensive classification for both classes of converters. Several applications inspired by actual case studies are included in the paper in order to provide realistic application examples.

IEEE Transactions on Power Systems, 2020

Power system dynamic state estimation (DSE) remains an active research area. This is driven by th... more Power system dynamic state estimation (DSE) remains an active research area. This is driven by the absence of accurate models, the increasing availability of fast-sampled, timesynchronized measurements, and the advances in the capability, scalability, and affordability of computing and communications. This paper discusses the advantages of DSE as compared to static state estimation, and the implementation differences between the two, including the measurement configuration, modeling framework and support software features. The important roles of DSE are discussed from modeling, monitoring and operation aspects for today's synchronous machine dominated systems and the future power electronics-interfaced generation systems. Several examples are presented to demonstrate the benefits of DSE on enhancing the operational robustness and resilience of 21st century power system through time critical applications. Future research directions are identified and discussed, paving the way for developing the next generation of energy management systems.