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Cheng X.,University of Texas at Arlington | Lee W.-J.,University of Texas at Arlington | Sahni M.,PWR Solutions Inc. | Cheng Y.,Electric Reliability Council of Texas | Lee L.K.,University of Texas at Arlington
IEEE Transactions on Industry Applications | Year: 2016

An increasing number of wind turbine generators (WTGs) are being installed in modern power system networks. As a result, substantial achievements have been made in developing generic wind models to represent the dynamic behavior of WTGs on the grid. The Western Electricity Coordinating Council (WECC) has developed and proposed four generic models for positive sequence stability analysis of WTG. These models provide a good first step in terms of simulating the dynamic response of WTGs on the power system grid. Since it requires accurate parameters to predict the true response of the WTG, challenges associated with the simulation of dynamic response of WTGs in the field still remain. This paper proposes a procedure to estimate parameters of dynamic equivalent model of WTG by using the measurement data from phasor measurement units (PMUs). Hybrid dynamic simulation is used to reduce external system by employing input signal on PMU bus. Stochastic approximation is adopted in searching optimized model parameter values. A two-WTG subsystem in Electric Reliability Council of Texas (ERCOT) is presented as a case study to address the importance of correct model in system operation strategy. Two most commonly used generic WTG models have been utilized to demonstrate the effectiveness of the proposed approach. © 2016 IEEE. Source


Cheng X.,University of Texas at Arlington | Lee W.-J.,University of Texas at Arlington | Sahni M.,PWR Solutions Inc. | Cheng Y.,ERCOT | Lee L.K.,UT ArlingtonTX
2015 IEEE/IAS 51st Industrial and Commercial Power Systems Technical Conference, I and CPS 2015 | Year: 2015

An increasing number of wind turbine generators (WTGs) are being installed in modern power system networks. As a result, substantial achievements have been made in developing generic wind models to represent the dynamic behavior of WTGs on the grid. The Western Electricity Coordinating Council (WECC) has developed and proposed four generic models for positive sequence stability analysis of WTG. These models provide a good first step in terms of simulating the dynamic response of WTGs on the power system grid. Since it requires accurate parameters to predict the true response of the WTG, challenges associated with the simulation of dynamic response of WTGs in the field still remain. This paper proposes a procedure to estimate parameters of dynamic equivalent model of WTG by using the measurement data from Phasor Measurement Units (PMUs). Hybrid dynamic simulation is used to reduce external system by employing input signal on PMU bus. Stochastic approximation is adopted in searching optimized model parameter values. A two-WTG subsystem in Electric Reliability Council of Texas (ERCOT) is presented as a case study to address the importance of correct model in system operation strategy. Two most commonly used generic WTG models have been utilized to demonstrate the effectiveness of the proposed approach. © 2015 IEEE. Source


Cheng Y.,PWR Solutions Inc. | Lee W.-J.,University of Texas at Arlington | Huang S.-H.,Electric Reliability Council of Texas | Adams J.,Electric Reliability Council of Texas
IEEE Power and Energy Society General Meeting | Year: 2011

After 2003 blackout, wide area measurement, monitoring, and visualization become one of the most important areas of smart grid initiative. Synchrophasors are precise time-synchronized measurements of certain parameters on the electricity grid, now available from grid monitoring devices called phasor measurement units (PMUs). Phasor data and applications are valuable for grid reliability because they give grid operators and planners unprecedented insight into what is happening on the grid at high resolution, over a wide area in time synchronized mode, and where needed, in real-time. Phasor information gives operator the "current" situation of the system. However, engineers still rely on simulation tool to predict the behavior of the power system and provide possible mitigation measures for system problems. The accuracy of the dynamic parameters are the prerequisite for the reliable solutions. Dynamic parameter identification which aims at obtaining accurate dynamic parameters is one of the central topics in power system studies. This paper proposes a hybrid method combining particle swarm optimization (PSO) and sensitivity analysis (SA) for dynamic parameter identification. The proposed hybrid method provides the right balance and trade-off between convergence and computation speed. In addition, the parallel programming is used to take advantage of multiple core processors to significantly increase the computation speed. The simulation results show the validity and benefit of the proposed algorithm. © 2011 IEEE. Source


Cheng Y.,PWR Solutions Inc. | Sahni M.,PWR Solutions Inc. | Muthumuni D.,Manitoba HVDC Research Center Inc. | Badrzadeh B.,Vestas Inc.
IEEE Transactions on Power Delivery | Year: 2013

This paper presents a reactance crossover-based technique to investigate subsynchronous control interaction (SSCI) concerns associated with doubly fed induction generator-based wind generation resources. A theoretical discussion serving as the mathematical premise for the proposed approach is presented. The driving point reactance, as seen from the WGR, across the subsynchronous frequency range is determined using four different approaches. Specifically, two of the four methods (Methods 3 and 4) are unique in terms of the approach utilized for performing frequency scans. System-side frequency scans are augmented with turbine-side frequency scans. A dynamic frequency-scanning method for the turbine side is developed which takes the turbine nonlinearities and its active behavior into account. The presence of crossover points in the reactance scans, as obtained from four approaches, in conjunction with the turbine-side frequency scans is utilized to draw conclusions on potential SSCI concerns. A portion of the Electric Reliability Council of Texas grid model has been utilized for the case study. The observations/inferences drawn via the reactance scans are corroborated via electromagnetic transients simulations. © 1986-2012 IEEE. Source


Karnik N.,PWR Solutions Inc. | Sahni M.,PWR Solutions Inc. | York J.,LS Power | Cook T.,LS Power
45th North American Power Symposium, NAPS 2013 | Year: 2013

Zero-sequence mutual coupling between transmission lines has been known to adversely affect various facets of transmission line protection. In specific, the ground over-current and distance relay elements are most impacted by presence of mutual coupling between transmission lines. Mutual coupling causes spurious tripping of ground over-current relays and leads to over/under-reach issues in distance relays. The impact of mutual coupling on distance relays is well documented. However limited research and development has been witnessed in the use of analytical techniques to evaluate impact of mutual coupling on ground over-current protection elements. This paper presents an analytical approach to accurately and quickly determine whether ground relays on un-faulted lines will trip due to the mutual coupling effect. The proposed approach analytically identifies optimal fault locations to evaluate potential for mis-operation of ground over-current relays. It is tested on transmission lines which are a part of two asynchronous grids (ERCOT and SPP). It precisely identifies relay mis-operations on the mutually coupled lines. In addition to being highly accurate, it is amenable for implementation on conventional phasor-domain analysis tools used by most of the utilities. © 2013 IEEE. Source

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