Training Electrical Engineers for Renewable Energy Challenges

Transcription

1 Training Electrical Engineers for Renewable Energy Challenges Dragan Maksimovic ECE Department University of Colorado at Boulder

2 Background Growing interest in Energy Engineering Environmental and climate change concerns Energy independence goals A new frontier in Engineering: challenging problems, opportunities for innovation, entrepreneurship, and rewarding careers 2

3 Background Growing interest in Energy Engineering Environmental and climate change concerns Energy independence goals A new frontier in Engineering: challenging problems, opportunities for innovation, entrepreneurship, and rewarding careers 9,212 solar panels, 1,600 kw solar power system at the Google campus, Mountain View, CA 3

4 A New Frontier in Engineering New Priorities: for some job seekers, oil companies are out. Alternative-energy startups are the place to be The Wall Street Journal, Oct. 29, 2007, p. R8 Greentech could be the largest economic opportunity of the 21 st century, KPCB Venture Capital, 4

5 Training of Electrical Energy Engineers Electrical Engineering started as electric power engineering; up to 1970 s EE curricula were dominated by traditional electric power topics Over the last years, the traditional electric power theme has diminished in EE/ECE programs Mature technology Fewer research funding opportunities Fewer attractive engineering career options Rapid emergence of many other EE and ECE areas Electrical Engineering is now at the core of many existing and emerging green energy technologies How should we (re)organize EE programs to address the growing interests, as well as current and anticipated needs? 5

6 What is Electrical Energy Engineering? In the late 19 th century Electrical Engineering started the revolution in generation, transmission and distribution of Electric Power Nikola Tesla Polyphase ac power distribution, and motors/generators based on rotating magnetic field In the 20 th century, Electrical Engineering revolutionized Communication and Computing William Shockley, John Bardeen, Walter Brattain Transistor, Bell Labs, Dec quad-core processor, more than 500 million transistors 21 st century Electrical Energy Engineering is all of the above, and more 6

7 Electrical Energy Engineering program at CU Boulder Sophomore Junior Senior Graduate ECEN2060 Renewable Sources and Efficient Electrical Energy Systems ECEN3170 Energy Conversion ECEN4797/5797 Intro to Power Electronics ECEN4517/5517 Power Electronics and Systems Lab ECEN5807 Model. and Control of Power Electronics ECEN5817 Resonant and Soft Switch Tech. in Power Electronics ECEN4167 Energy Conversion 2 ECEN5017 Conventional and Renewable Energy Issues EE/ECE fundamentals: Circuits and microelectronics, semiconductor devices, IC design, EM fields, programming, digital logic, embedded computing, communications/dsp, control systems Faculty: Frank Barnes, Robert Erickson, Ewald Fuchs, Dragan Maksimovic, Regan Zane 7

8 Electrical Energy Engineering program at CU Boulder Sophomore Junior Senior Graduate ECEN2060 Renewable Sources and Efficient Electrical Energy Systems ECEN3170 Energy Conversion ECEN4797/5797 Intro to Power Electronics ECEN4517/5517 Power Electronics and Systems Lab ECEN5807 Model. and Control of Power Electronics ECEN5817 Resonant and Soft Switch Tech. in Power Electronics ECEN4167 Energy Conversion 2 ECEN5017 Conventional and Renewable Energy Issues New introductory sophomore-level course, first offered in Spring 2008 Spring 2008 enrollment: 31 students, 2 non-credit continuing education Minimal prerequisites, strong technical contents Instructors: Dragan Maksimovic, Robert Erickson, and Regan Zane 8

9 ECEN 2060 Objectives and Outline Introduction to Electrical Energy Engineering Improve generation Reduce consumption Renewable Energy Sources Photovoltaic power systems Wind power systems Transmission, Distribution, Conversion and Storage Energy Efficiency Energy efficient lighting Drives in hybrid and electric vehicles Understanding of electrical engineering fundamentals in renewable sources and energy efficient systems Practical knowledge of engineering design issues in system examples Background and motivation for follow-up studies 9

10 ECEN 2060 Syllabus Introduction to electric power system Photovoltaic () power systems Energy efficient lighting Wind power systems Hybrid and electric vehicles I DC n T Permanentmagnet synchronous machine 3øac ø a v ab (t) ø b i a (t) i b (t) A C Q 1 v A0 (t) Q 3 B v B0 (t) Q 5 v C0 (t) V DC ø c i c (t) Q 2 Q 4 Q

11 ECEN 2060 Syllabus, Spring 2008 Electric Power System (4 lectures) Electric utility industry, generation and consumption statistics, cost of electricity Overview of electricity generation: power plants and polyphase generators Transmission and distribution of electricity, the US electric power grids Photovoltaic Power Systems (16 lectures) The solar resource cell physics and efficiency limits, technologies, and cell electrical model Grid-connected systems Power electronics Stand-alone systems and lead-acid batteries Energy Efficient Lighting (5 lectures) Lighting technologies, luminous efficiency and cost of lighting Electronic ballasts for discharge lamps Solid-state lighting and LED drives Wind Power Systems (10 lectures) The wind resource and efficiency limits, overview of wind turbines Wind turbine electrical systems: constant-speed and variable-speed architectures AC machines 3-phase power electronics Guest lecture on wind turbine electrical systems and controls by Lee Jay Fingersh (NREL) Hybrid and Electric Vehicles (6 lectures) HEV power train architectures: series, parallel and series/parallel Batteries for HEV, PHEV and EV Variable-speed AC drives Operation and sizing of system components 11

12 ECEN2060 topic example: systems Grid-tie power system example I i L L i dc array V C pv v L i t v t C V DC Single-phase DC-AC inverter i ac v ac AC utility grid v gate DT s T s MPPT controller Inverter controller What is it and how does it work? Basic physics Operation and engineering of system components System engineering and economics 12

13 (1) Fundamentals of technology Power density p(lambda) [W/m^2/nm] Full sun: 1,000 W/m 2 = ( λ) dλ = AM1.5 Ideal photovoltaic output Photoelectric output power (ideal): I p pv λ max p 0 300nm pv ( λ) dλ = 490 W/m I ηmax = = 49% I S 2 Basic semiconductor and cell physics; limits of efficiency Overview of technologies, crystalline Si, thin film, etc cell circuit model and characteristics ISC I D V D R p R s V _ I 0.2 cell Wavelength [nm] 13

14 (2) modules and arrays Module and array characteristics Maximum power point (MPP) array I V C pv i L L v L v gate i t DT s v t T s C V DC i dc Single-phase DC-AC inverter i ac v ac AC utility grid Effects of shading MPPT controller Inverter controller Ipv [A] I pv [A] Characteristics of an array of twenty 75 Wp modules (36-cell each) in series Ppv [W] P pv [W] 900 W/m 2 (partial shading) 1,000 W/m 2 (uniform) 200 W/m 2 (uniform) Vpv [V] V pv [V] Vpv [V] V pv [V] 14

15 (3) power electronics Basic operation of DC-DC converters and DC-AC inverters Overview of power semiconductor switches Basic averaged models and efficiency analysis Boost DC-DC converter averaged model V I R L I pv [A] η boost Ipv [A] 1D : = 92% I 1 out I sw V DC Vpv [V] η boost Boost DC-DC efficiency analysis in the system η boost = 96% V pv [V] = 92% I i L L i dc Boost DC-DC waveforms array V C pv v L i t v t C V DC Single-phase DC-AC inverter i ac v ac AC utility grid v gate DT s T s MPPT controller Inverter controller Grid-tie system using Boost DC-DC MPP tracker 15

16 (4) system controls MPP P pv Initialize I ref, ΔI ref, P old Measure P pv I pv = I ref Perturb and observe maximum power point tracking algorithm DC-AC inverter controls DC bus voltage control AC grid current shaping; unity power factor YES Continue in the same direction P pv > P old? I ref = I ref ΔI ref P old = P pv Change direction NO ΔI ref = ΔI ref 16

17 (5) system design and economics Insolation data: US hours of full sun map kwh m 2 day Solar resource System sizing and basic economics Example: a grid-tie system in Boulder Average of 5.5 hours or full sun array I V C pv i L L v L v gate i t MPPT controller DT s v t T s C V DC i dc Single-phase DC-AC inverter Inverter controller i ac v ac AC utility grid 1 Wp (Watts peak) installed produces about 1.5 kwh per year Cost: about $8/Wp (excluding incentives) 17

18 ECEN2060 observations Energy systems rich in EE contents (e.g., Wind, Hybrid and Electric Vehicles) are great motivators for students in an introductory class This is not just a survey class: it is possible to introduce electrical energy engineering topics in significant technical depths even in an introductory class Basic physics, materials and components Power electronics and electric machines System controls, system design and economics Curriculum revisions are under way to open space for attractive introductory courses such as ECEN2060 at the sophomore level 18

19 Electrical Energy Engineering program at CU Boulder Sophomore Junior Senior Graduate ECEN2060 Renewable Sources and Efficient Electrical Energy Systems ECEN3170 Energy Conversion ECEN4797/5797 Intro to Power Electronics ECEN4517/5517 Power Electronics and Systems Lab ECEN5807 Model. and Control of Power Electronics ECEN5817 Resonant and Soft Switch Tech. in Power Electronics ECEN4167 Energy Conversion 2 ECEN5017 Conventional and Renewable Energy Issues Major course revision in Spring 2008 Spring 2008 enrollment: 33 undergraduates, 11 graduate students Objectives: hands-on design and project experience Instructors: Robert Erickson, Regan Zane and Dragan Maksimovic 19

20 ECEN4517/5517 Power Electronics and Systems Lab The course begins with basic experiments on: Photovoltaic power systems Power conversion electronics The course then culminates in a design project involving photovoltaics and power electronics panels, battery, and inverter in the ECEN 4517 laboratory DC loads Panel 85 W Charge control DC-DC converter for maximum power point tracking and battery charge profile Battery Deepdischarge lead-acid 12 V, 56 A-hr Inverter 120 V 60 Hz 300 W true sinewave AC loads Digital control A basic standalone power system in the ECEN 4517 laboratory 20

21 CoPEC ECEN4517/5517 Syllabus 1. Basic system elements (1 week) 2. Basic converter control circuitry and pulse-width modulator Buck converter (1 week) 3. Battery charge controller and peak power tracker using a DC-DC buck converter (3 weeks) 4. Inverter system (3 weeks) 5. Project (6 weeks) Battery ECE Expo v pv C 1 High side gate driver Experiment 3 12 VDC HVDC: VDC DC-DC converter Isolated flyback L 1 C 2 v batt Bootstrap power supply Pulse-width Micro modulator controller Peak power tracking and battery charge control DC-AC inverter H-bridge v ac (t) i batt Sensors Battery current and voltage AC load 120 Vrms 60 Hz d(t) Feedback controller V ref d(t) Digital controller Experiment 4 21

22 Portable carts 85 W panel that can be wheeled outside Deep discharge lead-acid battery and 300 W inverter to power test equipment Auxiliary DC power supplies for control circuitry One cart per bench, 10 total panel 85 W pk 17.2 V at 4.95 A Shell SQ-85P Battery 12 V deep-discharge 56 A-hr Battery charger Off cart: on stationary workbench Cart schematic D s panel Connectors Battery Isolated dc-dc converters Inverter 60 Hz 300 W 120 Vrms 6 outlet ac power strip Alarm Battery low voltage 12V, 1A 12V, 1A 5V, 2A Voltmeter Battery voltage DC loads Panel 85 W Charge control DC-DC converter for maximum power point tracking and battery charge profile Battery Deepdischarge lead-acid 12 V, 56 A-hr Inverter 120 V 60 Hz 300 W true sinewave AC loads Digital control 22

23 Experiment 1, Jan ,

24 ECE Expo, May 1, 2008 MPP tracker based on digitally controlled Cuk DC-DC converter (April 26 College of Engineering Expo) 20 projects in power electronics for or energy efficiency Electronic ballast for fluorescent lamps Cascaded boost DC-DC converter (battery to highvoltage DC conversion) 24

25 Research Program Colorado Power Electronics Center (CoPEC) 13 sponsoring companies, 25 graduate students, Faculty: R.Erickson, D.Maksimovic, Z.Popovic, R.Zane Smart Power Electronics Technology Analog, mixed-signal and digital control techniques Mixed-signal integrated circuits for power control Converter modeling and design Energy Harvesting Medical systems Lighting Ballasts LED drives Energy Efficiency Switched-mode power supplies Power for RF systems Power Electronics for Renewable Energy Ipv, Vpv Converter I pv, V pv Controller Ipv, Vpv Converter I pv, V pv Controller Ipv, Vpv Converter I pv, V pv Controller Ipv, Vpv Converter I pv, V pv Controller Inverter 60 Hz AC Utility PFC Isolated DC-DC POL DC-DC Multi-phase Low-power Ipv, Vpv Converter I pv, V pv Controller Ipv, Vpv Converter I pv, V pv Controller 25

26 Conclusions Electrical Energy Engineering at CU Boulder EE/ECE fundamentals materials/devices systems economics More interdisciplinary than other EE areas Emphasis on technical and engineering fundamentals, even in introductory courses with minimum prerequisites Motivated students Department strengths and new initiatives Energy is a major area of emphasis in the ECE Department CoPEC research program: very strong industrial support Related strengths in control systems, remote sensing, materials and devices, RF/microwave electronics CU/CSU/CSM/NREL CREW: Colorado Renewable Energy Collaboratory Center for Research and Education in Wind Campus-wide energy initiative 26