Manitoba HVDC Research Center Inc.

Winnipeg, Canada

Manitoba HVDC Research Center Inc.

Winnipeg, Canada

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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.


Badrzadeh B.,Australian Energy Market Operator | Sahni M.,PwrSolutions Inc. | Zhou Y.,Vestas Inc. | Muthumuni D.,Manitoba HVDC Research Center Inc. | Gole A.,University of Manitoba
IEEE Transactions on Power Systems | Year: 2013

This paper presents a general methodology for analysis of sub-synchronous interaction in wind power plants. These include appropriate frequency scanning method for the assessment of the sub-synchronous control interaction, and calculation of the electrical damping provided by the wind turbine generator for investigation of the sub-synchronous torsional interaction. A general formulation of both methods applicable to any given wind turbine and network is presented. A dynamic frequency scanning method for the turbine side is developed which takes account of the turbine nonlinearities and its active behavior. Various aspects that need to be considered when injecting a voltage or current signal into the system for dynamic frequency scanning are discussed in detail. The veracity of thesemethods is confirmed against electromagnetic transient analyses. The application of these tools and techniques is demonstrated on a practical power system comprising type 3 wind turbines and series compensated lines. © 2012 IEEE.


Ginn H.L.,University of South Carolina | Hingorani N.,EPRI | Sullivan J.R.,Naval Surface Warfare Center Carderock Division | Wachal R.,Manitoba HVDC Research Center Inc. | Wachal R.,University of Winnipeg
Proceedings of the IEEE | Year: 2015

When the control functions of various types of power electronics systems are examined, a significant degree of common functionality emerges, irrespective of the target application. It is possible to define hierarchical control architectures for these systems using common interface definitions between control system divisions or layers. Such definitions enable the use of common designs for multiple applications and the use of commercially available electronics and communications modules allowing cost reduction in power electronics applications. This paper presents various partitioning strategies of a hierarchical control architecture for use in high power electronics control systems and defines various parameters/functions that need to be handled within each layer, and those that need to be communicated between the layers. Each layer has characteristic processing and communication speed requirements, irrespective of the final applications. © 1963-2012 IEEE.


Peters R.R.,University of North Dakota | Muthumuni D.,Manitoba HVDC Research Center Inc. | Bartel T.,Minnkota Power Cooperative | Salehfar H.,University of North Dakota | Mann M.,University of North Dakota
Electric Power Systems Research | Year: 2010

An installed 900 kW fixed speed stall controlled soft-started wind turbine connected to a weak distribution grid was modeled under start-up conditions. Generator and soft-start control and design parameters were not available, so a modeling process independent of this information was developed. Field measured transients were closely reproduced in simulation using a full-order generator model with generic parameters and a thyristor-based graduated interconnection to the grid. A Static VAR Compensator model was then added to the wind turbine model to explore a method of reducing start-up transients. It was found that for the specific transients modeled, a 300 kVAR SVC supplied sufficient reactive power to limit line voltage variations to within 3% of steady state values. Model details and simulation output are presented in this paper. © 2009 Elsevier B.V. All rights reserved.


Gnanarathna U.N.,University of Manitoba | Gole A.M.,University of Manitoba | Jayasinghe R.P.,Manitoba HVDC Research Center Inc.
IEEE Transactions on Power Delivery | Year: 2011

The number of semiconductor switches in a modular multilevel converter (MMC) for HVDC transmission is typically two orders of magnitudes larger than that in a two or three level voltage-sourced converter (VSC). The large number of devices creates a computational challenge for electromagnetic transient simulation programs, as it can significantly increase the simulation time. The paper presents a method based on partitioning the system's admittance matrix and deriving an efficient time-varying Thvenin's equivalent for the converter part. The proposed method does not make use of approximate interfaced models, and mathematically, is exactly equivalent to modelling the entire network (converter and external system) as one large network. It is shown to drastically reduce the computational time without sacrificing any accuracy. The paper also presents control algorithms and other modelling aspects. The efficacy of the proposed method is demonstrated by simulating a point-to-point VSC-MMC-based HVDC transmission system. © 2010 IEEE.


Williams D.M.T.J.,University of Manitoba | Gole A.M.,University of Manitoba | Wachal R.W.,Manitoba HVDC Research Center Inc.
Canadian Conference on Electrical and Computer Engineering | Year: 2011

This paper investigates an approach to repurposing old hybrid electric vehicle batteries for energy storage in electrical networks that incorporate renewable energy sources. Such batteries suffer from aging affects that limit their ability to maintain their designed capacity, voltage and current ratings. Furthermore, this paper examines the battery aging factors which will affect the development of a repurposed battery energy storage system and uses pulsed charge regulation and interlacing of batteries to form a multi-level battery operation scheme to further the life of the aged batteries. The approach is demonstrated using detailed electromagnetic transient simulations. © 2011 IEEE.


De Silva H.M.J.,University of Manitoba | Gole A.M.,University of Manitoba | Nordstrom J.E.,Manitoba HVDC Research Center Inc. | Wedepohl L.M.,University of Manitoba
IEEE Transactions on Power Delivery | Year: 2010

This paper proposes an algorithm to enforce passivity on the time-domain simulation model for a multi-conductor cable or transmission line. The model is first reformulated in a form which reduces the severity of passivity violations. The frequency sweep method is then used to identify any remaining passivity violating regions of the model's frequency response. These small passivity violations are then removed using a linear constrained least squares algorithm to perturb the diagonal elements of propagation matrix. The passivity enforcement algorithm is applied to the Universal Line Model (ULM), a widely used robust phase domain formulation implemented in many commercial electromagnetic transients simulation programs. Two examples of multi-conductor underground cable systems, one for ac and the other for HVDC transmission are presented to demonstrate the proposed approach. © 2010 IEEE.


Nanayakkara O.M.K.K.,University of Manitoba | Rajapakse A.D.,University of Manitoba | Wachal R.,Manitoba HVDC Research Center Inc.
IEEE Transactions on Power Delivery | Year: 2012

This paper presents a novel algorithm to determine the location of dc line faults in an HVDC system with multiple terminals connected to a common point, using only the measurements taken at the converter stations. The algorithm relies on the traveling-wave principle, and requires the fault-generated surge arrival times at the converter terminals. With accurate surge arrival times obtained from time-synchronized measurements, the proposed algorithm can accurately predict the faulty segment as well as the exact fault location. Continuous wavelet transform coefficients of the input signal are used to determine the precise time of arrival of traveling waves at the dc line terminals. Performance of the proposed fault-location scheme is analyzed through detailed simulations carried out using the electromagnetic transient simulation software PSCAD. The algorithm does not use reflected waves for its calculations and therefore it is more robust compared to fault location algorithms previously proposed for teed transmission lines. Furthermore, the algorithm can be generalized to handle any number of line segments connected to the star point. © 1986-2012 IEEE.


Nanayakkara O.M.K.K.,University of Manitoba | Rajapakse A.D.,University of Manitoba | Wachal R.,Manitoba HVDC Research Center Inc.
IEEE Transactions on Power Delivery | Year: 2012

This paper presents a novel algorithm to determine the location of dc line faults in an HVDC system with a mixed transmission media consisting of overhead lines and cables, using only the measurements taken at the rectifier and inverter ends of the composite transmission line. The algorithm relies on the traveling-wave principle, and requires the fault-generated surge arrival times at two ends of the dc line as inputs. With accurate surge arrival times obtained from time-synchronized measurements, the proposed algorithm can accurately predict the faulty segment as well as the exact fault location. Continuous wavelet transform coefficients of the input signal are used to determine the precise time of arrival of traveling waves at the dc line terminals. Two possible input signals-the dc voltage measured at the converter terminal and the current through the surge capacitors connected at the dc line end-are examined and both signals are found to be equally effective for detecting the traveling-wave arrival times. Performance of the proposed fault-location scheme is analyzed through detailed simulations carried out using the electromagnetic transient simulation software PSCAD. The impact of measurement noise on the fault-location accuracy is also studied in this paper. © 2006 IEEE.


Wachal R.,Manitoba HVDC Research Center Inc.
IET Conference Publications | Year: 2010

Digital based HVDC control and protection system are a common place reality. Experience since the initial installations of these digital control systems indicate clearly that at least one control system replacement can be expected in any system prior to the retirement of the entire system. Control systems have typically fifteen to twenty-five (15-25) year life expectancy. Thyristor valves, converter transformers, high voltage circuit breakers, have a life expectancy of thirty to forty years, while the transmission line life expectancy may be seventy-five to one hundred years. A relevant question that can be asked is; "What can be specified and designed into the HVDC protection and control system, at the project conception stages that would facilitate a control system replacement project in the future?" Controls systems for HVDC systems will be replaced. While control systems are estimated at 8-10% of the cost of a green field HVDC system, control replacement costs are significant larger percentages. By understanding the issues associated with control replacement, there is opportunity at the start of an HVdc project to consider control replacement in the future. This discussion paper reviews HVDC control life expectancy issues and proposes steps the user HVDC can take to increase the life of their control system.

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