Power Electronics and Drives
Code
10919
Academic unit
Faculdade de Ciências e Tecnologia
Department
Departamento de Engenharia Electrotécnica
Credits
6.0
Teacher in charge
Stanimir Stoyanov Valtchev
Weekly hours
4
Teaching language
Português
Objectives
This subject aims at the acquisition by the students of sufficient knowledge and competence in the area of power electronics in actuators, where the students should be capable to select and/or design the most suitable power converter for a certain application. Students must acquire knowledge about the composition, properties and functioning of the power electronic circuits and devices generally used in electromechanical drives. Students should become able to design and build some circuits, following given specifications. Students should also develop soft skills such as: ability to categorize priorities in the analysis of a technical problem, ability to make structured and clear decisions and improve their written and oral communication skills. The final objective is to contribute to a more interdisciplinary profile of the student, and thus to improve his employability.
Prerequisites
Electronics I + Theorectical Electrotechnics
Subject matter
. Introduction. Terminology. Types of conversion and energy converters. Power electronics and linear electronics. Revision of the applications, especially in the area of the actuators. Classification of converters. The interdisciplinary nature of power electronics. Latest power electronics circuits, intelligent and microminiaturized circuits. Contactless energy transfer and energy harvesting.
. Basic principles of the DC-DC converter. Chopper and pulse modulation. BUCK Converter and its operation. BOOST, BUCK-BOOST, FORWARD and FLYBACK converters. Continuous and discontinuous current operation. Control methods, voltage mode and current mode.
. Revision of the electronic devices applied to control the energy flux. Characteristics: idealized and real. Diodes. Thyristors. Application limits and protection circuits. Triac. Fully controllable power electronic devices. Bipolar power transistor. Protection circuits. Unipolar transistor and power MOS. Characteristics and applications. SOAR. Gate control. IGBT as a compromise. Recent solutions. GTO, SITh, MCT etc.
. Natural (line) commutated converters (excl. resonant). Uncontrolled rectifiers. Basic concepts. Monophase rectifiers. Calculation of characteristic values. Three-phase rectifiers. N-phase rectifier and voltage multipliers. Uncontrolled rectifiers working with complex load. Phase-controlled rectifiers (SCR). Protections. Rectifier and inverter. Cycloconverter. AC switch and regulator, dimmer.
.Voltage inverter and current inverter. Differences and preferences. Single phase inverter, half-bridge and full bridge. Resistive and complex load. Harmonics reduction. Control methods. Pulse modulation and "Notching". Sinusoidal modulation. Applications that include transformer.
. Forced commutated converters. Schematic solutions for aided commutaation of thyristors. Series and parallel inverters. Resonant load commutation. Induction heating. DC-DC converters with internal resonant loop. Sub-resonant and super-resonant converters. ZVS and ZCS. PWM and phase-shift control. Parallel and series load, parallel and series resonance. Resonant switches and quasi-resonant converters.
. DC motor control. Different versions of the AC motor control. Control of induction motor. Brushless DC PM motors drives. V, f, V/f and vector control of motors. Characteristics. Renewable energy applications. Power factor improvement methods for converters.
Bibliography
· Muhammad H. Rashid, Electrônica de Potência, Makron Books do Brasil, S. Paulo, 1999
· Mohan, Undeland, Robbins , Power Electronics: Converters, Applications, and Design John Wiley & sons, 2002, John Wiley & sons, 2002
Teaching method
Scientific principles are explained by the teacher in the theory class, aided by slides. The student’s capacity for oral communication is stimulated through debate around technical and scientific questions.
In practical classes a collection of technical problems is offered to be solved by students based on theoretical class knowledge by calculation. The dialogue between the students is encouraged, and qualitative evaluation is made.
Evaluation method
1st Way: test No.1 (30%, but with a minimum note of 8, being this test eliminatory, i.e. not permitting continuing this way), test No.2 (45%), 4 reports on laboratory exercises (25 % of the final note, being the reports compulsory for the permission= frequency);
2nd Way: 4 reports on laboratory exercises (25 % of the final note, being the reports compulsory for the permission= frequency), exam of retrying (75%).