The document discusses cycloconverters, which are devices that convert AC power at one frequency to AC power at another frequency in a single stage using thyristors. It describes the different types of cycloconverters including step-up, step-down, single phase, and three phase cycloconverters. It also discusses the principles, components, applications, advantages, and disadvantages of cycloconverters.
This document provides an overview of power thyristors, also known as SCRs (silicon controlled rectifiers). It discusses the basic construction and operation of thyristors, including:
- Thyristors are four layer semiconductor devices with three terminals - anode, cathode, and gate. The gate controls current flow.
- In forward blocking mode, the device blocks current flow. In forward conduction mode, applying a gate pulse triggers large current flow with a small voltage drop.
- Turning on involves a delay, rise, and spread time as conduction spreads. Turning off passively occurs when current reverses; carrier charges must then be removed.
- Applications include controlling output power
Introduction of wide area mesurement syatemPanditNitesh
This document summarizes a seminar presentation on Wide Area Measurement Systems (WAMS). WAMS uses Phasor Measurement Units (PMUs) synchronized by GPS to monitor power grids. PMUs measure voltage and current phasors, while Phasor Data Concentrators (PDCs) collect and process data from multiple PMUs. The seminar discusses the components of WAMS including PMUs, PDCs, and communication protocols. It also reviews several implementations of WAMS and their applications in monitoring the electric grid.
Reactive power compensation is used to improve the performance of AC power systems. There are various methods of reactive power compensation including shunt compensation, series compensation, static VAR compensators, and static synchronous compensators. Shunt compensation devices such as capacitors and reactors are connected in parallel to transmission lines to regulate voltage. Series compensation uses capacitors connected in series to transmission lines to increase power transfer capability. Static VAR compensators and static synchronous compensators use thyristor-based voltage sourced converters to dynamically inject or absorb reactive power and control voltage. Reactive power compensation provides benefits such as improved power factor, voltage regulation, reduced losses, and increased power transfer capacity.
The document discusses three phase voltage source inverters. It begins by introducing inverters and their use in converting DC to AC power. It then classifies inverters as voltage source or current source. The main topic is the three phase voltage source inverter, which converts DC to three phase AC power using six switches in three arms delayed by 120 degrees. The inverter can operate in 180 degree or 120 degree conduction modes, which determine the output phase and line voltages. Applications of three phase inverters include DC power utilization, UPS, induction heating, variable frequency drives, and electric vehicle drives.
This document describes a project to build a third harmonic distortion meter using a PIC18F2550 microcontroller. It explains that non-linear components can cause harmonics in AC power systems, with the third harmonic being particularly impactful. The project involves using a microcontroller and discrete Fourier transform calculations to measure the amplitude of the fundamental frequency and third harmonic from a rectified input signal. This allows the third harmonic distortion to be displayed as a percentage. The document provides details of the circuit design and software used to implement this third harmonic distortion meter.
The document provides an overview of grid code technical recruitments in India. It discusses the roles of various organizations in electricity transmission planning and operations. The National Load Dispatch Center oversees national grid operations while Regional Load Dispatch Centers control regional operations. State Load Dispatch Centers control operations within states. Transmission utilities and state transmission utilities plan and develop inter-state and intra-state transmission systems respectively. The Central Electricity Authority issues technical standards and guidelines for transmission planning. Regional Power Committees facilitate coordination between states. The document also summarizes various codes related to transmission planning, grid connections, grid operations, and scheduling and dispatch of electricity.
The document discusses cycloconverters, which are devices that convert AC power at one frequency to AC power at another frequency in a single stage using thyristors. It describes the different types of cycloconverters including step-up, step-down, single phase, and three phase cycloconverters. It also discusses the principles, components, applications, advantages, and disadvantages of cycloconverters.
This document provides an overview of power thyristors, also known as SCRs (silicon controlled rectifiers). It discusses the basic construction and operation of thyristors, including:
- Thyristors are four layer semiconductor devices with three terminals - anode, cathode, and gate. The gate controls current flow.
- In forward blocking mode, the device blocks current flow. In forward conduction mode, applying a gate pulse triggers large current flow with a small voltage drop.
- Turning on involves a delay, rise, and spread time as conduction spreads. Turning off passively occurs when current reverses; carrier charges must then be removed.
- Applications include controlling output power
Introduction of wide area mesurement syatemPanditNitesh
This document summarizes a seminar presentation on Wide Area Measurement Systems (WAMS). WAMS uses Phasor Measurement Units (PMUs) synchronized by GPS to monitor power grids. PMUs measure voltage and current phasors, while Phasor Data Concentrators (PDCs) collect and process data from multiple PMUs. The seminar discusses the components of WAMS including PMUs, PDCs, and communication protocols. It also reviews several implementations of WAMS and their applications in monitoring the electric grid.
Reactive power compensation is used to improve the performance of AC power systems. There are various methods of reactive power compensation including shunt compensation, series compensation, static VAR compensators, and static synchronous compensators. Shunt compensation devices such as capacitors and reactors are connected in parallel to transmission lines to regulate voltage. Series compensation uses capacitors connected in series to transmission lines to increase power transfer capability. Static VAR compensators and static synchronous compensators use thyristor-based voltage sourced converters to dynamically inject or absorb reactive power and control voltage. Reactive power compensation provides benefits such as improved power factor, voltage regulation, reduced losses, and increased power transfer capacity.
The document discusses three phase voltage source inverters. It begins by introducing inverters and their use in converting DC to AC power. It then classifies inverters as voltage source or current source. The main topic is the three phase voltage source inverter, which converts DC to three phase AC power using six switches in three arms delayed by 120 degrees. The inverter can operate in 180 degree or 120 degree conduction modes, which determine the output phase and line voltages. Applications of three phase inverters include DC power utilization, UPS, induction heating, variable frequency drives, and electric vehicle drives.
This document describes a project to build a third harmonic distortion meter using a PIC18F2550 microcontroller. It explains that non-linear components can cause harmonics in AC power systems, with the third harmonic being particularly impactful. The project involves using a microcontroller and discrete Fourier transform calculations to measure the amplitude of the fundamental frequency and third harmonic from a rectified input signal. This allows the third harmonic distortion to be displayed as a percentage. The document provides details of the circuit design and software used to implement this third harmonic distortion meter.
The document provides an overview of grid code technical recruitments in India. It discusses the roles of various organizations in electricity transmission planning and operations. The National Load Dispatch Center oversees national grid operations while Regional Load Dispatch Centers control regional operations. State Load Dispatch Centers control operations within states. Transmission utilities and state transmission utilities plan and develop inter-state and intra-state transmission systems respectively. The Central Electricity Authority issues technical standards and guidelines for transmission planning. Regional Power Committees facilitate coordination between states. The document also summarizes various codes related to transmission planning, grid connections, grid operations, and scheduling and dispatch of electricity.
This document proposes installing capacitor banks on the 11kV Toitskraal feeder to improve the poor power factor. The feeder has a peak power factor of 0.78 lagging due to inductive loads like irrigation pumps. One 500kVAr fixed capacitor bank and one 750kVAr switched bank will be installed. Simulations show the banks will reduce line loading, losses, and improve voltages while paying for themselves within 4.65 months through energy savings. The project is recommended to optimize the network and significantly reduce costs.
The universal motor can operate on both AC and DC power sources. It has series-connected stator and rotor windings, with the rotor windings connected to commutator bars and brushes. The commutator switches the direction of current in the rotor coils to enable rotation when powered by either AC or DC. It is also known as an AC series motor or AC commutator motor.
An SCR (Silicon Controlled Rectifier) is a solid state semiconductor device that controls current flow through its four layers. It functions like a conventional rectifier but is controlled by a gate signal. When the gate receives a threshold voltage, the SCR turns on and conducts current in a forward conducting mode. SCRs are commonly used to produce DC voltages for motors by rectifying AC line voltage through half-wave or full-wave rectification.
This document introduces the economic dispatch problem of optimizing the allocation of power generation across multiple thermal generating units connected to a single bus to minimize total generation costs while meeting load demand. It describes the economic dispatch problem mathematically as minimizing a total cost objective function subject to the constraint that total generation equals load. It provides examples of solving the economic dispatch problem for systems both with and without considering transmission losses. The examples illustrate setting up and solving the optimization problem using Lagrange multipliers and iteratively updating generator outputs and losses until converging on a solution.
This document discusses various sources of transient over-voltages on power systems including capacitor switching and lightning. It describes how capacitor switching can cause oscillations that generate transient over-voltages. Lightning can also directly or indirectly introduce surges into power systems. The document outlines issues like magnification of transients at customer locations and ferroresonance that can occur. It discusses principles of overvoltage protection like limiting voltage and diverting surge current. Protection devices like surge arresters and transient voltage surge suppressors are described.
This document discusses different types of DC generators, including permanent magnet, separately excited, and self-excited generators. It focuses on self-excited DC generators, which can be series wound, shunt wound, or compound wound. The document provides details on the magnetic or open circuit characteristic curve, which shows the relationship between field current and generated voltage without a load. It also discusses the internal and external characteristic curves when the generator is loaded, accounting for voltage drops due to armature reaction and ohmic losses. Characteristics of series wound and shunt wound generators are covered as well.
Presentation on Siddhirganj 2×120 MW PPP of EGCB_Faujul Kabirfaujul_bigc
This document provides an overview of the Siddhirganj 2×120 MW Peaking Power Plant of the Electricity Generation Company of Bangladesh (EGCB) Ltd. Some key details include:
- The plant has 2 gas turbine generator units with a total capacity of 240 MW.
- Each unit includes a GE Frame 9E gas turbine, gas booster compressor, and generator. Natural gas is used as fuel.
- The gas turbine uses a simple cycle Brayton process involving compression, combustion, expansion, and exhaust.
- Other components discussed include the inlet air filters, combustion system, turbine, generator, step-up transformer, switchgear, and control systems.
-
This document is the draft Indian Electricity Grid Code which outlines the roles and responsibilities for planning and operating the Indian power system network. It contains 7 chapters which cover topics such as the roles of various organizations involved in grid operations, planning codes for inter-state transmission, connection codes, operating codes for regional grids, scheduling and dispatch codes. It also includes annexures on commercial mechanisms and payment for reactive energy exchanges. The document is published by the Central Electricity Regulatory Commission of India and establishes the philosophy and framework for the Indian electricity grid.
This document discusses the key components and operating principles of DC generators. It describes the essential parts of a practical generator including the magnetic frame, pole cores, field coils, armature core, armature windings, commutator, brushes and bearings. It also covers different types of armature windings such as lap and wave windings. Finally, it discusses losses that occur in DC generators and conditions for maximum efficiency.
The armature winding is the main current-carrying winding in which the electromotive force or counter-emf of rotation is induced.
The current in the armature winding is known as the armature current.
The location of the winding depends upon the type of machine.
The armature windings of dc motors are located on the rotor, since they must operate in union with the commutator.
In DC rotating machines other than brushless DC machines, it is usually rotating.
This document discusses different types of single-phase induction motors and how they are made self-starting. It describes the construction and working of a basic single-phase induction motor. Such a motor is not self-starting because it produces an alternating flux that cannot cause rotation on its own. The document then explains various methods used to make single-phase motors self-starting, including split-phase, capacitor-start, and shaded-pole designs. It provides details on how split-phase and capacitor-start motors introduce a phase difference between windings using a starting winding and capacitor, producing a revolving magnetic field that can start the motor.
Electric heating works by converting electrical energy to heat energy using the principle of Joule heating. When an electric current passes through a resistor, it produces heat due to I2R losses. There are various domestic and industrial applications of electric heating, including water heaters, ovens, welding, and heat treatment processes. Electric heating has advantages over other heating methods like being clean, allowing for accurate temperature control, and providing uniform heating. Resistance heating and dielectric heating are two common methods for electric heating. Resistance heating directly or indirectly heats an object by passing a current through it or a nearby resistive element. Dielectric heating generates heat in non-conductive materials using electromagnetic fields.
This document discusses solar panels, inverters, and their functions. It defines a solar inverter as a device that converts the variable direct current from a solar panel into standard 240V alternating current. It describes the different types of inverters including off-grid, micro, grid-tie, and battery backup inverters. It also explains how solar panels work by using the photovoltaic effect to absorb light and release electrons, producing an electric current. The advantages of solar power are its renewable nature and potential for large-scale electricity generation, while disadvantages include high upfront costs and needing a large area for solar panels.
Rural electrification by Lakshmi.Nidoni-seminar pptlakshmi nidoni
The document discusses rural electrification through solar and wind hybrid systems. It proposes using both solar and wind energy sources together to provide continuous power for rural areas. The hybrid system would integrate solar photovoltaic panels, a wind turbine, batteries for energy storage, and a control system to combine power from the different renewable sources. Design of such a hybrid system requires collecting data on solar radiation levels, wind speeds, and power output of the solar and wind components. The hybrid approach aims to reduce the need for energy storage by harnessing multiple renewable resources.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
The document defines and describes an ideal transformer. An ideal transformer is defined as a transformer without any losses, meaning it has 100% efficiency. The ideal transformer model assumes windings are purely inductive with zero resistance and the core is lossless. This means 100% of the flux passes through the core and links both the primary and secondary windings. When an alternating voltage is applied to the primary winding, it induces a counter emf in the primary and draws a magnetizing current that lags 90 degrees. This current produces a flux that links the secondary winding and induces another emf in the secondary.
Three phase inverter - 180 and 120 Degree Mode of ConductionMalarselvamV
The document describes the operation of a 3-phase inverter that generates 3-phase AC voltage from a DC source using switches in both 180 degree and 120 degree conduction modes. In the 180 degree mode, each switch is closed for 180 degrees before the next switch closes. In the 120 degree mode, each switch is closed for 120 degrees. Tables show the switch states and resulting phase and line voltages for each 60 degree period. While the output waveforms are not pure sine waves, they approximate the desired 3-phase voltages. The inverter circuit provides a simple example for understanding 3-phase inverter operation.
This document proposes installing capacitor banks on the 11kV Toitskraal feeder to improve the poor power factor. The feeder has a peak power factor of 0.78 lagging due to inductive loads like irrigation pumps. One 500kVAr fixed capacitor bank and one 750kVAr switched bank will be installed. Simulations show the banks will reduce line loading, losses, and improve voltages while paying for themselves within 4.65 months through energy savings. The project is recommended to optimize the network and significantly reduce costs.
The universal motor can operate on both AC and DC power sources. It has series-connected stator and rotor windings, with the rotor windings connected to commutator bars and brushes. The commutator switches the direction of current in the rotor coils to enable rotation when powered by either AC or DC. It is also known as an AC series motor or AC commutator motor.
An SCR (Silicon Controlled Rectifier) is a solid state semiconductor device that controls current flow through its four layers. It functions like a conventional rectifier but is controlled by a gate signal. When the gate receives a threshold voltage, the SCR turns on and conducts current in a forward conducting mode. SCRs are commonly used to produce DC voltages for motors by rectifying AC line voltage through half-wave or full-wave rectification.
This document introduces the economic dispatch problem of optimizing the allocation of power generation across multiple thermal generating units connected to a single bus to minimize total generation costs while meeting load demand. It describes the economic dispatch problem mathematically as minimizing a total cost objective function subject to the constraint that total generation equals load. It provides examples of solving the economic dispatch problem for systems both with and without considering transmission losses. The examples illustrate setting up and solving the optimization problem using Lagrange multipliers and iteratively updating generator outputs and losses until converging on a solution.
This document discusses various sources of transient over-voltages on power systems including capacitor switching and lightning. It describes how capacitor switching can cause oscillations that generate transient over-voltages. Lightning can also directly or indirectly introduce surges into power systems. The document outlines issues like magnification of transients at customer locations and ferroresonance that can occur. It discusses principles of overvoltage protection like limiting voltage and diverting surge current. Protection devices like surge arresters and transient voltage surge suppressors are described.
This document discusses different types of DC generators, including permanent magnet, separately excited, and self-excited generators. It focuses on self-excited DC generators, which can be series wound, shunt wound, or compound wound. The document provides details on the magnetic or open circuit characteristic curve, which shows the relationship between field current and generated voltage without a load. It also discusses the internal and external characteristic curves when the generator is loaded, accounting for voltage drops due to armature reaction and ohmic losses. Characteristics of series wound and shunt wound generators are covered as well.
Presentation on Siddhirganj 2×120 MW PPP of EGCB_Faujul Kabirfaujul_bigc
This document provides an overview of the Siddhirganj 2×120 MW Peaking Power Plant of the Electricity Generation Company of Bangladesh (EGCB) Ltd. Some key details include:
- The plant has 2 gas turbine generator units with a total capacity of 240 MW.
- Each unit includes a GE Frame 9E gas turbine, gas booster compressor, and generator. Natural gas is used as fuel.
- The gas turbine uses a simple cycle Brayton process involving compression, combustion, expansion, and exhaust.
- Other components discussed include the inlet air filters, combustion system, turbine, generator, step-up transformer, switchgear, and control systems.
-
This document is the draft Indian Electricity Grid Code which outlines the roles and responsibilities for planning and operating the Indian power system network. It contains 7 chapters which cover topics such as the roles of various organizations involved in grid operations, planning codes for inter-state transmission, connection codes, operating codes for regional grids, scheduling and dispatch codes. It also includes annexures on commercial mechanisms and payment for reactive energy exchanges. The document is published by the Central Electricity Regulatory Commission of India and establishes the philosophy and framework for the Indian electricity grid.
This document discusses the key components and operating principles of DC generators. It describes the essential parts of a practical generator including the magnetic frame, pole cores, field coils, armature core, armature windings, commutator, brushes and bearings. It also covers different types of armature windings such as lap and wave windings. Finally, it discusses losses that occur in DC generators and conditions for maximum efficiency.
The armature winding is the main current-carrying winding in which the electromotive force or counter-emf of rotation is induced.
The current in the armature winding is known as the armature current.
The location of the winding depends upon the type of machine.
The armature windings of dc motors are located on the rotor, since they must operate in union with the commutator.
In DC rotating machines other than brushless DC machines, it is usually rotating.
This document discusses different types of single-phase induction motors and how they are made self-starting. It describes the construction and working of a basic single-phase induction motor. Such a motor is not self-starting because it produces an alternating flux that cannot cause rotation on its own. The document then explains various methods used to make single-phase motors self-starting, including split-phase, capacitor-start, and shaded-pole designs. It provides details on how split-phase and capacitor-start motors introduce a phase difference between windings using a starting winding and capacitor, producing a revolving magnetic field that can start the motor.
Electric heating works by converting electrical energy to heat energy using the principle of Joule heating. When an electric current passes through a resistor, it produces heat due to I2R losses. There are various domestic and industrial applications of electric heating, including water heaters, ovens, welding, and heat treatment processes. Electric heating has advantages over other heating methods like being clean, allowing for accurate temperature control, and providing uniform heating. Resistance heating and dielectric heating are two common methods for electric heating. Resistance heating directly or indirectly heats an object by passing a current through it or a nearby resistive element. Dielectric heating generates heat in non-conductive materials using electromagnetic fields.
This document discusses solar panels, inverters, and their functions. It defines a solar inverter as a device that converts the variable direct current from a solar panel into standard 240V alternating current. It describes the different types of inverters including off-grid, micro, grid-tie, and battery backup inverters. It also explains how solar panels work by using the photovoltaic effect to absorb light and release electrons, producing an electric current. The advantages of solar power are its renewable nature and potential for large-scale electricity generation, while disadvantages include high upfront costs and needing a large area for solar panels.
Rural electrification by Lakshmi.Nidoni-seminar pptlakshmi nidoni
The document discusses rural electrification through solar and wind hybrid systems. It proposes using both solar and wind energy sources together to provide continuous power for rural areas. The hybrid system would integrate solar photovoltaic panels, a wind turbine, batteries for energy storage, and a control system to combine power from the different renewable sources. Design of such a hybrid system requires collecting data on solar radiation levels, wind speeds, and power output of the solar and wind components. The hybrid approach aims to reduce the need for energy storage by harnessing multiple renewable resources.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
The document defines and describes an ideal transformer. An ideal transformer is defined as a transformer without any losses, meaning it has 100% efficiency. The ideal transformer model assumes windings are purely inductive with zero resistance and the core is lossless. This means 100% of the flux passes through the core and links both the primary and secondary windings. When an alternating voltage is applied to the primary winding, it induces a counter emf in the primary and draws a magnetizing current that lags 90 degrees. This current produces a flux that links the secondary winding and induces another emf in the secondary.
Three phase inverter - 180 and 120 Degree Mode of ConductionMalarselvamV
The document describes the operation of a 3-phase inverter that generates 3-phase AC voltage from a DC source using switches in both 180 degree and 120 degree conduction modes. In the 180 degree mode, each switch is closed for 180 degrees before the next switch closes. In the 120 degree mode, each switch is closed for 120 degrees. Tables show the switch states and resulting phase and line voltages for each 60 degree period. While the output waveforms are not pure sine waves, they approximate the desired 3-phase voltages. The inverter circuit provides a simple example for understanding 3-phase inverter operation.
Séries de Fourier complexes, Transformées de Fourier, Spectres d’amplitude et de phases, Relation d’indéterminatoin d’Heisenberg-Gabor, Produit de convolution, Théorème de convolution, Impulsion de Dirac, Éléments sur les distributions
I. Introduction
Approche fréquentielle
Signaux monodimensionnels périodiques
Signaux quelconques
Signaux numériques, discrétisation, échantillonnage
Observation spectrale, TFD et TFD 2D
Systèmes numériques
Filtres numériques
Produits de convolution. Cas 2D
Sur et sous échantillonnage. Bancs de filtres
Traitement des Images.
Approches multi résolution
II. Signaux aléatoires
variables aléatoires
Processus aléatoires. Stationnarité
Processus MA, AR et ARMA
Estimation des paramètres d’un AR
III. Traitement de l’information Application à la compression
codage de source, entropie,
compression sans perte : codages entropiques
par dictionnaire, par prédiction…
Codages par transformée
La DCT et la compression JPEG
Quantifications scalaire et vectorielle
IV. Communications numériques
Modulations numériques
modulation par impulsions codées
transmission du signal numérique
Applications : RDS, NICAM…
Détection et correction d’erreurs
Alternative au Tramway de la ville de Quebec Rev 1 sml.pdfDaniel Bedard
CDPQ Infra dévoile un plan de mobilité de 15 G$ sur 15 ans pour la région de Québec. Une alternative plus économique et rapide, ne serait-elle pas posssible?
- Valoriser les infrastructures ferroviaires du CN, en créant un Réseau Express Métropolitain (REM) plutôt qu'un nouveau tramway ou une combinaison des 2.
- Optimiser l'utilisation des rails pour un transport combiné des marchandises et des personnes, en accordant une priorité aux déplacements des personnes aux heures de pointes.
- Intégrer un téléphérique transrives comme 3ème lien urbain dédiés aux piétons et cyclistes avec correspondance avec le REM.
- Le 3 ème lien routier est repensé en intégrant un tunnel routier qui se prolonge avec le nouveau pont de l'Île d'Orléans et quelques réaménagemet de ses chausées.
https://www.linkedin.com/in/bedarddaniel/
English:
CDPQ Infra unveils a $15 billion, 15-year mobility plan for the Quebec region. Wouldn't a more economical and faster alternative be possible?
Leverage CN's railway infrastructure by creating a Metropolitan Express Network (REM) instead of a new tramway or a combination of both.
Optimize the use of rails for combined freight and passenger transport, giving priority to passenger travel during peak hours.
Integrate a cross-river cable car as a third urban link dedicated to pedestrians and cyclists, with connections to the REM.
Rethink the third road link by integrating a road tunnel that extends with the new Île d'Orléans bridge and some reconfiguration of its lanes.
https://www.linkedin.com/in/bedarddaniel/
Quelles rotations dans les systèmes caprins de Nouvelle-Aquitaine et Pays de ...
Gele2511 ch3
1. Chapitre 3
S´erie de Fourier
Une technique tr`es commune en ing´enierie est de r´eduire un probl`eme complexe en
plusieurs probl`emes simples. Les probl`emes simples sont alors r´esolus, et la solution glo-
bale est la somme des solutions simples. Ces solutions simples permettent souvent de
mieux comprendre le probl`eme complexe.
Une des m´ethodes les plus utiles dans l’analyse des signaux est la s´erie de Fourier. La
s´erie de Fourier permet de transformer n’importe quel signal p´eriodique en une somme
de sinuso¨ıdes. On peut donc prendre un signal p´eriodique complexe et le simplifier `a des
sinuso¨ıdes.
Pourquoi s’int´eresse-t’on aux signaux p´eriodiques ? Plusieurs sources ´electriques pro-
duisent des signaux p´eriodiques. Les g´en´erateurs de fonction produisent des ondes trian-
gulaires, rectangulaires et carr´ees. Les redresseurs, utilis´es pour produire des sources DC
`a partir d’un signal AC, produisent des sinuso¨ıdes qui sont p´eriodiques, mais redress´es.
3.1 S´erie de Fourier
Le math´ematicien franc¸ais Jean-Batiste Fourier d´ecouvrit qu’on pouvait transformer
n’importe quel signal p´eriodique en une somme de sinuso¨ıdes. Donc, pour une fonction
p´eriodique quelconque f (t), Fourier d´emontra qu’on pouvait faire l’´equivalence suivante :
f (t) = av +
∞
n=1
an cos(nω0t) + bn sin(nω0t) (3.1)
o`u av, an et bn sont les coefficients de Fourier, et ω0 est la fr´equence fondamentale. Les
fr´equences qui sont des multiples entiers de ω0 (comme 2ω0, 3ω0, etc.) sont nomm´es
1
2. CHAPITRE 3. S ´ERIE DE FOURIER
les harmoniques. Par exemple, 2ω0 est la deuxi`eme harmonique, 3ω0 est la troisi`eme
harmonique, et ainsi de suite.
Pour faire l’analyse de circuits dont la source est p´eriodique mais non sinuso¨ıdale, il
faut d´ecomposer l’entr´ee en une s´erie de Fourier. Le premier coefficient obtenu, av, est
la composante DC du signal. Les autres composantes repr´esentent diff´erentes fr´equences
qui sont pr´esentent dans notre signal d’entr´ee. Ensuite, pour obtenir la sortie, on calcul la
sortie pour chaque fr´equence, puis on fait la superposition.
3.2 Coefficients de Fourier
Les coefficients de Fourier sont obtenus selon les ´equations suivantes :
av =
1
T
t0+T
t0
f (t) dt (3.2)
an =
2
T
t0+T
t0
f (t)cos(nω0t) dt (3.3)
bn =
2
T
t0+T
t0
f (t)sin(nω0t) dt (3.4)
Remarquer que av est la valeur moyenne (ou DC) du signal.
Exemple 1
Calculer la s´erie de Fourier pour le signal p´eriodique suivant.
v(t)
t
Vm
0 T 2T
Lorsqu’on utilise les ´equations 3.2 `a 3.4, on peut choisir la valeur de t0. Le meilleur
choix est de prendre t0 = 0, ce qui simplifie beaucoup les calculs. L’´equation de v(t) entre
0 et T est :
v(t) =
Vm
T
t
Gabriel Cormier 2 GELE2511
3. CHAPITRE 3. S ´ERIE DE FOURIER
Donc l’´equation pour av est :
av =
1
T
T
0
Vm
T
t dt =
1
2
Vm
L’´equation de an est :
an =
2
T
T
0
Vm
T
t cos(nω0t) dt
=
2Vm
T 2
1
n2ω2
0
cos(nω0t) +
t
nω0
sin(nω0t)
T
0
=
2Vm
T 2
1
n2ω2
0
(cos(2πn) − 1) = 0 pour tout n
L’´equation de bn est :
bn =
2
T
T
0
Vm
T
t sin(nω0t) dt
=
2Vm
T 2
1
n2ω2
0
sin(nω0t) +
t
nω0
cos(nω0t)
T
0
=
2Vm
T 2
0 −
T
nω0
cos(2πn)
=
−Vm
πn
La s´erie de Fourier de v(t) est :
v(t) =
Vm
2
−
Vm
π
∞
n=1
1
n
sin(nω0t)
On peut reconstruire le signal original `a l’aide de la s´erie de Fourier pour v´erifier si on
peut bel et bien obtenir l’original. La figure 3.1 montre la reconstruction en utilisant 7, 15
et 51 harmoniques.
On voit bien que plus le nombre d’harmoniques utilis´es est ´elev´e, plus le signal origi-
nal est reconstruit fid`element. Cependant, il y a un pic lorsque la fonction a un change-
ment abrupte (`a t = 1s, par exemple). Ce pic est dˆu `a ce qu’on appelle l’effet Gibbs.
Le calcul des coefficients de Fourier est, g´en´eralement, un calcul assez long. N’importe
quoi qui simplifie la tˆache est donc b´en´efique. On verra dans la prochaine section que si
le signal poss`ede de la sym´etrie, on peut grandement simplifier le calcul des coefficients
de Fourier.
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4. CHAPITRE 3. S ´ERIE DE FOURIER
0 0.5 1 1.5 2
0
0.5
1
Temps (s)
Original
0 0.5 1 1.5 2
0
0.5
1
Temps (s)
n = 7
0 0.5 1 1.5 2
0
0.5
1
Temps (s)
n = 15
0 0.5 1 1.5 2
0
0.5
1
Temps (s)
n = 51
Figure 3.1 – Onde en dent de scie reconstruite par s´erie de Fourier
3.3 Sym´etrie et les coefficients de Fourier
Le type de sym´etrie d’un signal peut simplifier le calcul des coefficients de la s´erie de
Fourier. Voir le chapitre 1 pour les types de sym´etrie. Selon le type de sym´etrie, certains
des coefficients de la s´erie de Fourier sont nuls. Il est important de bien identifier le type
de sym´etrie d’un signal avant de d´ecomposer en s´erie de Fourier.
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5. CHAPITRE 3. S ´ERIE DE FOURIER
Sym´etrie paire
Pour des fonctions paires, on peut d´emontrer que les coefficients de Fourier sont :
av =
2
T
T /2
0
f (t) dt (3.5)
an =
4
T
T /2
0
f (t)cos(nω0t) dt (3.6)
bn = 0 (3.7)
Sym´etrie impaire
Pour des fonctions impaires, on peut d´emontrer que les coefficients de Fourier sont :
av = 0 (3.8)
an = 0 (3.9)
bn =
4
T
T /2
0
f (t)sin(nω0t) dt (3.10)
Sym´etrie demi-onde
Pour des fonctions ayant de la sym´etrie demi-onde, on peut d´emontrer que les coeffi-
cients de Fourier sont :
av = 0 (3.11)
an = 0 pour n pair (3.12)
an =
4
T
T /2
0
f (t)cos(nω0t) dt pour n impair (3.13)
bn = 0 pour n pair (3.14)
bn =
4
T
T /2
0
f (t)sin(nω0t) dt pour n impair (3.15)
Sym´etrie quart-d’onde
Une fonction p´eriodique qui a la sym´etrie quart-d’onde peut toujours ˆetre rendue
soit paire ou impaire en faisant un choix appropri´e de t = 0. Pour une fonction ayant
Gabriel Cormier 5 GELE2511
6. CHAPITRE 3. S ´ERIE DE FOURIER
la sym´etrie quart-d’onde, si on la rend paire, alors
av = 0 (3.16)
an = 0 pour n pair (3.17)
an =
8
T
T /4
0
f (t)cos(nω0t) dt pour n impair (3.18)
bn = 0 (3.19)
Pour une fonction ayant la sym´etrie quart-d’onde, si on la rend impaire, alors
av = 0 (3.20)
an = 0 (3.21)
bn = 0 pour n pair (3.22)
bn =
8
T
T /4
0
f (t)sin(nω0t) dt pour n impair (3.23)
Exemple 2
Calculer les coefficients de Fourier pour la fonction de la figure suivante :
i(t)
t
Im
−Im
La premi`ere chose `a faire est de chercher pour de la sym´etrie. La fonction est impaire,
et de plus, poss`ede de la sym´etrie demi-onde et quart-d’onde. Puisque la fonction est
impaire, av = 0, et an = 0. `A cause de la sym´etrie demi-onde, bn = 0 pour les valeurs paires
de n. `A cause de la sym´etrie quart-d’onde, l’´equation de bn pour les valeurs impaires de n
est :
bn =
8
T
T /4
0
i(t)sin(nω0t) dt
Dans l’intervalle 0 ≤ t ≤ T /4, l’´equation de i(t) est :
i(t) =
4Im
T
t
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7. CHAPITRE 3. S ´ERIE DE FOURIER
Alors,
bn =
8
T
T /4
0
4Im
T
t sin(nω0t) dt
=
32Im
T 2
sin(nω0t)
n2ω2
0
−
t cos(nω0t)
nω0
T /4
0
=
8Im
π2n2
sin
nπ
2
n est impair
La repr´esentation en s´erie de Fourier de i(t) est :
i(t) =
8Im
π2
∞
n=1,3,5...
1
n2
sin
nπ
2
sin(nω0t)
La reconstruction de i(t) est montr´ee `a la figure 3.2. Dans ce cas-ci, tr`es peu de fr´equences
sont n´ecessaires pour reconstruire le signal original.
3.4 Formes alternatives de la s´erie de Fourier
Il y a deux autres fac¸ons d’exprimer la s´erie de Fourier : on peut utiliser une forme
polaire, ou une forme exponentielle. La forme polaire est la suivante :
f (t) = av +
∞
n=1
An cos(nω0t + θn) (3.24)
o`u An est d´efini selon :
An∠θn = an − jbn (3.25)
La forme polaire est plus utile pour faire des graphiques. Il est plus facile de com-
prendre des graphes d’amplitude et de phase que de regarder des sinus et cosinus pour
comprendre le comportement d’un signal. Cependant, lors de calculs math´ematiques
(dans un logiciel), il peut y avoir des erreurs si on utilise la notation polaire, `a cause
des approximations des radians et les fonctions trigonom´etriques inverses.
La forme exponentielle est :
f (t) =
∞
n=−∞
Cnejnω0t
(3.26)
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8. CHAPITRE 3. S ´ERIE DE FOURIER
0 0.5 1 1.5 2
−1
0
1
Temps (s)
Original
0 0.5 1 1.5 2
−1
−0.5
0
0.5
1
Temps (s)
n = 3
0 0.5 1 1.5 2
−1
0
1
Temps (s)
n = 7
0 0.5 1 1.5 2
−1
0
1
Temps (s)
n = 11
Figure 3.2 – Onde en dent de scie reconstruite par s´erie de Fourier
o`u
Cn =
1
T
t0+T
t0
f (t)e−jnω0t
dt (3.27)
La forme exponentielle est obtenue `a partir de la relation d’Euler. Cette repr´esentation de
la s´erie de Fourier est souvent plus facile `a utiliser lors de calculs math´ematiques ou lors
de la programmation.
On peut r´esumer la conversion d’une forme `a une autre `a l’aide du tableau 3.1.
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9. CHAPITRE 3. S ´ERIE DE FOURIER
Tableau 3.1 – Formes de la s´erie de Fourier
Forme ´Equation
Exponentielle
∞
n=−∞
Cnejnω0t Cn = |Cn|ejθn, C−n = C∗
n
Polaire C0 +
∞
n=1
2|Cn|cos(nω0t + θn)
Trigonom´etrique C0 +
∞
n=1
(An cos(nω0t) + Bn sin(nω0t))
2Cn = An − jBn, C0 = A0
3.5 Spectre d’amplitude et de phase
Une fonction p´eriodique est d´efinie par ses coefficients de Fourier et sa p´eriode. Si on
connaˆıt av, an, bn et T , on peut construire f (t). Si on connaˆıt an et bn, on connaˆıt aussi
l’amplitude An et le d´ephasage θn de chaque harmonique.
On peut repr´esenter graphiquement une fonction p´eriodique en termes de l’amplitude
et de la phase de chaque terme de la s´erie de Fourier. On appelle ceci le spectre de la fonc-
tion. Ce graphe permet de visualiser quelles fr´equences ont une amplitude importante ;
dans certains cas, la majorit´e du signal est contenu dans quelques harmoniques.
On fera un exemple pour d´emontrer l’utilisation.
Exemple 3
Donner le spectre de la fonction suivante, si Vm = 5V et τ = T /5.
v(t)
t
−τ/2
Vm
τ/2 T
0
On utilise la forme exponentielle pour cet exemple, ce qui donnera directement l’am-
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10. CHAPITRE 3. S ´ERIE DE FOURIER
plitude de chaque composante spectrale.
Cn =
1
T
τ/2
−τ/2
Vme−jnω0t
dt
=
Vm
T
e−jnω0t
−jnω0
τ/2
−τ/2
=
2Vm
nω0T
sinnω0τ/2
On peut r´e´ecrire sous une forme un peu diff´erente :
Cn =
Vmτ
T
sinnω0τ/2
nω0τ/2
qui est de la forme (sinx)/x.
Avec les valeurs donn´ees dans le probl`eme, on a
Cn =
sinnπ/5
nπ/5
Le spectre d’amplitude est montr´e `a la figure 3.4. Remarquer que le spectre donne 0
aux multiples de 5, ou lorsque nτ/T est un entier. Ce qui veut dire que le 5i`eme, 10i`eme,
15i`eme, ... harmoniques sont nuls. L’enveloppe du signal forme la fonction sinc.
−10 −8 −6 −4 −2 0 2 4 6 8 10
0
0.2
0.4
0.6
0.8
1
n
|Cn|
Figure 3.3 – Spectre d’amplitude du signal de l’exemple 3
Le spectre de phase est montr´e `a la figure suivante. Puisque Cn est r´eel dans ce cas-ci,
la phase est 0◦ ou 180◦, selon le signe de Cn.
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11. CHAPITRE 3. S ´ERIE DE FOURIER
−10 −8 −6 −4 −2 0 2 4 6 8 10
0
60
120
180
n
θn(degr´es)
Figure 3.4 – Spectre d’amplitude du signal de l’exemple 3
3.6 Valeur RMS
La valeur RMS d’une fonction peut ˆetre exprim´ee en fonction des coefficients de la
s´erie de Fourier. Par d´efinition, la valeur RMS d’une fonction est :
frms =
1
T
T
0
f (t)2 dt (3.28)
En remplac¸ant f (t) par son ´equivalent en s´erie de Fourier, on obtient
frms = a2
v +
∞
n=1
An
√
2
2
(3.29)
La valeur RMS d’un signal p´eriodique est la racine carr´ee de la somme des amplitudes
au carr´e de chaque harmonique et de la composante DC du signal.
Cependant, il faut typiquement une infinit´e de sinuso¨ıdes pour repr´esenter un signal,
et donc il faut faire une somme infinie pour avoir la vraie valeur RMS du signal. Il est
souvent plus simple de calculer la valeur RMS `a partir de l’´equation 3.28.
3.7 S´erie de Fourier et syst`emes
La s´erie de Fourier peut ˆetre utilis´ee pour calculer la sortie d’un syst`eme, au lieu d’uti-
liser la convolution. On peut d´emontrer que la sortie en r´egime permanent d’un syst`eme
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12. CHAPITRE 3. S ´ERIE DE FOURIER
h(t) soumis `a une entr´ee x(t) est :
y(t) =
∞
n=−∞
CnH(jnω0)ejnω0t
(3.30)
ou,
y(t) = C0|H(0)| +
∞
n=−∞
2|Cn||H(jnω0)|cos(nω0t + θn + θh(jnω0)) (3.31)
o`u les coefficients sont H(jnω0) = |H(jnω0)|∠θh. En d’autres mots, le syst`eme h(t) modifie
l’amplitude et la phase de chaque fr´equence pr´esente dans l’entr´ee x(t).
La r´eponse en fr´equence H(jω) est obtenue en faisant la transform´ee de Laplace de
h(t), puis en appliquant la substitution s → jω.
H(jω) = H(s)
s=jω
(3.32)
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