CONVERSION AND GENERATION FROM RENEWABLE SOURCES
Learning outcomes of the course unit
1) Knowledge and understanding
Attending classes and through individual study, students are to acquire:
• Know how to use renewables to produce electrical energy;
• Knowledge of circuits topologies and understanding of the working principle of: (i) basic circuits of the most relevant of static power converters conversion, (ii) protection circuits (snubbers), (iii) drivers for controlled switches;
• Knowledge of the devices sizing of basic converters;
• Knowledge of the working principle, construction and types of transformers;
• Knowledge of the working principle, construction and types of electric rotating machines;
• Knowledge of technologies, technics and circuits of photovoltaic and wind systems;
• Knowledge and basic skills in MATLAB-Simulink to simulate power converters and power plants by renewables, using mathematical and/or functional models.
2) Applying knowledge and understanding
A goal of this course is providing students with the ability of applying their knowledge of electrical engineering, electronics, power electronics, and power systems for electrical production from renewable sources.
Importance is also given to the ability of solving problems and exercises to size active and passive devices and to evaluate the main figures of merit of power converters, analyzing their working principle.
Students should be familiar with the notions of mathematics, physics (electromagnetism), electrical engineering, digital and analog electronics typically acquired in first-level degrees in Information engineering (class L-8).
Course contents summary
The main contents of the course, here cut into 5 parts, are the following:
- Part 1: Introduction (3 hours)
1) Consumption and generation of energy and electricity
2) Conventional and renewable generation
- Part 2: Basic principles of power electronics (26 hours)
3) Solid state switches
4) AC/DC converters (rectifiers)
5) Dissipative regulators and switching DC/DC converters
6) DC/AC converters (inverters)
7) Snubber circuits for power switches
8) Drivers for BJTs e MOSFETs
- Part 3: Electrical machines (6 hours)
9) Single-phase and three-phase transformers
10) Asynchronous AC electrical machines
11) Synchronous machines
- Part 4: Electrical power distributions systems and power generation from renewable energy sources (12 hours)
12) Photovoltaic and wind systems
13) Electrical power distribution
14) Smart grid and smart plugs
- Part 5: laboratory (16 hours)
15) Models for simulations of power electronic converters
16) Testing of development boards with power converters.
- Part 1:
1) Introduction (1 hour):
Consumption and generation of energy and electricity.
Environmental sustainability. The carbon cycle. World, European and Italian energy consumption. Energy regulations.
2) Conventional and renewable generation (2 hours):
Basic principles of the hydroelectric, geothermal, wind, solar thermal and
photovoltaic, tides and waves, biomass and biogas, conversion systems.
- Part two:
3) Introduction to power electronics (2 hours):
Basics of semiconductor power switches. Power converter classification.
Figures of merit: input and output distortion, efficiency, regulation.
4) AC/DC converters (rectifiers) (3 hours):
Single-phase half-wave rectifier. Single-phase full-wave rectifier with center-tapped transformer. Single-phase full-wave bridge rectifier. Low-pass filters. Single-phase full-wave bridge rectifier with RLE load.
Three-phase full-wave bridge rectifier.
5) Dissipative regulators and switching DC/DC converters (10 h):
Dissipative regulators. Switching DC/DC converters: Buck; Boost; Buck-
Boost; Cuk converter; H-bridge. PWM modulation.
6) DC/AC converters (inverters) (6 h):
Single-phase half-bridge inverter. Single-phase full-bridge inverter. Three-phase full-bridge inverter: 180° and 120° operation. Full-bridge inverter modulations: single-pulse PWM, multiple-pulse PWM, sinusoidal PWM;
space vector modulation.
7) Snubber circuits for power switches (4 hours):
Turn-off, overvoltage, and turn-on snubbers.
8) Drivers for BJTs e MOSFETs (1 hour):
Examples of driver circuits for BJTs and MOSFETs. Driver isolation.
- Part 3:
9) Transformers (2 hours):
Working principle, equations, equivalent electrical circuits, standard test and construction of single-phase and three-phase transformers.
10) Rotating electric machines (4 hours):
Working principle, construction of asynchronous and synchronous electric rotating machines.
- Part 4:
11) Electric power distribution (3 hours):
Distribution with centralized electricity generation. The current state of the electric grid. The impact of renewable resources. Distributed generation. Smart Grids. Energy storage. Topology of a smart plug. Reference technical rules for the connection of active and passive users to the low-voltage electrical utilities (CEI 0-21).
12) Photovoltaic and wind systems (9 hours):
Technologies, components and architectures of photovoltaic and wind power plants.
- Part 5:
13) Modeling of power electronic converters (8 hours):
Laboratory activities to show numerical models of power converters using MATLAB-Simulink.
14) Electrical tests (8 hours):
Laboratory activities to characterize buck and/or boost converters protoypes.
• L. Freris, D. Infield, "Renewable energy in power systems", Wiley, 2008, ISBN 978-0-470-01749-4
• M. Rashid, "Power electronics", 3rd ed., Prentice-Hall, ISBN 0-13-122815-3.
• M. Guarnieri e M. Stella, "Principi e applicazioni dell'elettrotecnica" Vol. II, Ed. Progetto Padova.
The course (9 credits) is given with lectures, tutorials, and laboratory work including simulation exercises, in a total amount of 63 hours:
• Classroom lectures by the instructor with the aid of slides (available for download to students) projection and web surfing (47 hours);
• Power boards testing and MATLAB-Simulink tutorials and exercises in laboratory (16 hours).
The instructor is available to answer specific questions on the lessons also by appointment (e-mail).
Assessment methods and criteria
The student is typically required to answer to three main questions on all the topics covered in the course.
Students will have to show that they:
• know the main problems due to energy balance and consumptions, with particular attention to the electricity sector. Among the skills that students must show, there is also their know-how about renewables (RE) technologies, benefits, and technical and economic problems resulting from the penetration of RE and the technical rules of reference. In addition, it is required that the students can describe the basic architectures of converters for photovoltaic and wind power plants, together with their main features.
• know the structure of the circuits analyzed in the lectures, and that they can describe their operation. Students will also have to demonstrate that they can evaluate the performance of power converters by calculating their main figures of merit based on the voltage and current waveforms. It is also expected that students will be able to solve simple design exercises involving the sizing of active and passive devices.
• know the basic theory of electric machines presented during the lectures.
• know how to model a power converter or a power plant for simulations, using mathematical and logical functions.
Depending on the knowledge and skills shown, for each answer to the main questions will be assigned a maximum score of 10. The maximum score is given if the answer is exhaustive compared to what was shown in the course lessons. When the answer is not exhaustive, the score is assigned according to what was discussed correctly by the student, comparing it with the overall topic discussed during the lessons.
In the case of test judged positive (when the student proves to know at least the basic concepts of the arguments related to each question), the final grade will be given by the sum of the three partial scores.
Praise is given in the case of achieving the highest score on each topic, which includes some in-depth knowledge of the topics discussed during the lessons and/or the mastery of the disciplinary literacy.
The final grade is communicated immediately at the end of the oral test.