Roger Champagne

Application of a multivariable feedback linearization scheme for rotor angle stability and voltage regulation of power systems

This paper investigates the application of a nonlinear controller to the multi-input multi-output model of a system consisting of a hydraulic turbine and a synchronous generator. The controller proposed is based on a feedback linearization scheme. Its main goal is to control the rotor angle as well as the terminal voltage, to improve the systems stability and damping properties under large disturbances and to obtain good post-fault voltage regulation. The response of the system is simulated in the presence of a short-circuit at the terminal of the machine in two different configurations and compared to the performance of a standard IEEE type 1 voltage regulator, PSS and a PID speed regulator.

Analysis and validation of a real-time AC drive simulator

This paper presents the analysis and validation of a real-time AC drive simulator. Real-time simulation has been used for over a decade in power systems engineering to test controllers thoroughly, efficiently, and safely. The development and testing of large DC drives could benefit from this type of simulation, but real-time power system simulators have modeling restrictions preventing stable and accurate simulation of isolated drives switching at high frequencies. These restrictions can be overcome by combining in a single model both the power converter and motor models. After discussing the salient issues related to the real-time simulation of DC drives, a prototype real-time simulator for drives is described. Its ability to accurately emulate the behavior of large drives is demonstrated through two case studies. A first case study demonstrates the feasibility of simulating a drive of typical complexity in real-time. The second case study demonstrates how the controller for a PWM VSI fed induction motor, switching at 4 kHz, is designed, implemented in a microcontroller and tested in real-time using a simulated inverter, motor and load. Comparisons against results obtained with another simulation tool, which uses extremely accurate variable-step integration algorithms, demonstrates the validity of our approach.

Transient Modeling of Squirrel-Cage Induction Machine Considering Air-Gap Flux Saturation Harmonics

A transient model of a squirrel-cage induction machine, including air-gap flux saturation harmonics, is presented in this paper. The machine model is based on a flux model, where the winding magnetizing fluxes are directly calculated from the resultant air-gap magnetomotive force, avoiding the use of complicated inductance harmonics. The effects of the fundamental and third harmonic components of the air-gap flux are incorporated in the model by two saturation factors. Moreover, the saturation effects are incorporated in the machines torque equation, allowing the model to investigate the machines performance under any load condition. The machine parameters, including saturation data, are obtained via the conventional no-load and locked-rotor tests, with access to the stator neutral connection. The proposed model is validated by experimental results for a squirrel-cage machine and can be used to predict machine transient states.

Adaptation of Apriori to MapReduce to Build a Warehouse of Relations between Named Entities across the Web

The Semantic Web has made possible the use of the Internet to extract useful content, a task that could necessitate an infrastructure across the Web. With Hadoop, a free implementation of the MapReduce programming paradigm created by Google, we can treat these data reliably over hundreds of servers. This article describes how the Apriori algorithm was adapted to MapReduce in the search for relations between entities to deal with thousands of Web pages coming from RSS feeds daily. First, every feed is looked up five times per day and each entry is registered in a database with MapReduce. Second, the entries are read and their content sent to the Web service OpenCalais for the detection of named entities. For each Web page, the set of all itemsets found is generated and stored in the database. Third, all generated sets, from first to last, are counted and their support is registered. Finally, various analytical tasks are executed to present the relationships found. Our tests show that the third step, executed over 3,000,000 sets, was 4.5 times faster using five servers than using a single machine. This approach allows us to easily and automatically distribute treatments on as many machines as are available, and be able to process datasets that one server, even a very powerful one, would not be able to manage alone. We believe that this work is a step forward in processing semantic Web data efficiently and effectively.

An approach for real-time simulation of electric drives

This paper investigates simulation techniques which differ widely from those actually used in real-time simulation of large power systems. The objective is to simulate electric drives in real-time, in order to provide drive designers with a tool which would allow them to design and prototype the controller stage of high power drives without actually needing the cumbersome power source, converter and machine. The fundamental differences between the simulation of drives and large power systems are identified. This motivates investigation of a modeling technique based on the state variable approach (SVA). An integration algorithm is then proposed to solve the state space equations. Off-line results of a case study are presented, after which limitations and applicability of this method are presented and implementation issues on a multiprocessor computer are discussed.

Real-time simulation of electric drives

This paper presents a real-time simulation of an ac electric drive. The main purpose of this type of simulation is to provide an efficient, cost-effective and secure way of testing the control part of an electric drive. Therefore, the electric motor and the electronic converter of the drive are simulated using a time-step of about 50 µs and an external controller is tested by interfacing it to the real-time simulation. Note that the distribution system and the motor mechanical load can be also conveniently included in the real-time simulation. This new way of testing drives controllers avoids the need for bulky and expensive test benches equipped with high power motors, converters and measurement devices. The real-time simulation results are validated by comparing them to their off-line version.

A new generation of simulation tools for electric drives and power electronics

This paper introduces two powerful and user-friendly simulation tools for the analysis of power systems, power electronics and drive systems. The first tool consists in the Power System Blockset (an offline simulation tool) and the second one is the fully digital real-time simulator Hypersim. Their performances are demonstrated by an application example based on an induction machine AC drive.

Investigations on power quality issues in industrial distribution systems using the Power System Blockset simulation software

This paper illustrates the use of the Power System Blockset (PSB), dedicated to the simulation of power systems with power electronic converters and drives. This Blockset based approach is valuable to identify power quality (PQ) issues and develop effective remedies for them. After a brief presentation of the new simulator, the focus of the paper is on the application of the new software tool to power quality improvement. The first case presented deals with the design of an active power filter (APF) for harmonic compensation in a three-phase system. The second study presents the PQ issues caused by the most common nonlinear loads in a single- phase industrial network and the solution using an active filter. Simulation and experimental results are included to demonstrate the usefulness of the Blockset approach.

Towards Automation of Performance Architectural Tactics Application

This paper describes the implementation of performance architectural tactics in ArchE, an expert system designed to help architects elaborate software architectures by automating certain tasks. Our goal was to explore what is involved in converting informally described tactics to a form that can be used by a tool to automate their relevant suggestion and application on software architectures. Adapting the tactics to the analysis tool and elaborating the rules that dictate their suggestion and application are the main challenges. Four performance tactics were successfully implemented in ArchE. Their use is illustrated through an example.

Experiments with Adding to the Experience that Can be Acquired from Software Courses

This paper describes approaches used in two different software engineering courses, where the goal is to give students some experience in the major aspects of real world software projects. The first course is a capstone project course, part of an undergraduate short program in software engineering. The second course is a course on software maintenance and testing, part of a full undergraduate program on software engineering. Each courses content, general organization and student workflow is described. In the case of the capstone project course, graduate students are used as experts/clients in the context of a course in their own program. For the software maintenance and testing course, the emphasis is put on laboratory work. Both courses are considered to have succeeded with respect to the stated objectives. The positive aspects and major challenges with each course are also summarized.