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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. Source


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. Source


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. Source


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. Source


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. Source

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