Recent Advances in Electric Energy Conversion and Storage

Transcription

1 Recent Advances in Electric Energy Conversion and Storage Hamid A. Toliyat, Ph.D., P.E., Fellow of IEEE Raytheon Professor Advanced Electric Machines & Power Electronics (EMPE) Laboratory Department of Electrical & Computer Engineering Texas A&M University College Station, ti TX Tel: (979)

2 Sources for Electric Power vs. Transport are Distinct SOURCES Electricity Sent to Grid USES Nuclear 8% Renewables (incl. hydro, biomass, wind, geothermal, and solar) 6% Natural Gas 20% Imports 3% Coal 23% Imports US Petroleum 15% Electric Power Sector 39% Export Export Residential/ Commercial Heat 12% Industrial Heat & Process 16% Non-Fuel Petroleum by-products (asphalt, petrochemica ls, etc.) 6% When you connect the lines, you see that there is virtually no overlap between the energy sources used for Electric Power versus that used for Transportation (oil). This is important when considering alternative ti energy sources. Oil Imports 25% Transportation 27% Source: Lawrence Livermore Natl Labs; EIA Data rounded to nearest whole decimal. Sources and Uses less than 1% not included Advanced Electric Machines & Power Electronics (EMPE) Lab 2

3 Energy Losses are Tremendous SOURCES Electricity Sent to Grid USES Nuclear 8% Renewables 6% Electric Power Sector 39% Electrical System Energy Losses Lost Energy 61% Natural Gas 20% Residential/ Commercial 12% Imports 3% Coal 23% Imports Energy lost in the process of converting, transporting, Export & distributing energy is significant; more than 60% of energy input is lost. A 1% decrease could save more than $3.0B annually*. Export Industrial 16% Non-Fuel 6% Useful Energy 39% US Petroleum 15% Oil Imports 25% * NCI estimate using $50/bbl oil & $3/mmbtu blended cost for gas/coal Source: Lawrence Livermore Natl Labs; EIA 2002 Data: Net Resource Consumption ~ 97 Quads Sources less than 1% not included Transportation 27% Advanced Electric Machines & Power Electronics (EMPE) Lab 3

4 Energy Issues Renewable Energy Wave Energy Photovoltaic Energy Wind Energy Biomass Geothermal Hydrogen Fuel Cell Energy Storages: Batteries Large surface area electrode Frequent deep cycles Low cost integrated system Flywheels Higher tensile strength SMES Higher capacity current Higher temperature superconductor Ultra capacitors Higher voltage cells Higher reliability Lamination of cells and stacks Transportations, Plug in Hybrid Vehicles Battery and its Modeling Improvement of power density and extension of battery lifeare strongly required for batteries used for HVs, and especially the safe use of Liion batteries is required. From this point of view, the improvement of accuracy in estimating SOC is extremely important. Motor/Generator and Control Wide constant power range for traction Constant torque for power generation Inverter and Power Transistors Cooling and capacitor size C switching devices (Silicon Carbide, etc.) Energy Harvesting Advanced Electric Machines & Power Electronics (EMPE) Lab 4

5 Energy Harvesting Exploded view of Seiko Kinetic watch Advanced Electric Machines & Power Electronics (EMPE) Lab 5

6 Power Generation with Renewable and Distributed Energy Resources Advanced Electric Machines & Power Electronics (EMPE) Lab 6

7 Advanced Electric Machines & Power Electronics (EMPE) Lab 7

8 Advanced Electric Machines & Power Electronics (EMPE) Lab Worldwide Wind Growth

9 Wind As a Percentage of Electricity Consumption Advanced Electric Machines & Power Electronics (EMPE) Lab

10 Evolution of Wind Technology World oldest windmill ill ( 644A.D.), Vertical-axis i windmill ill for milling grain (Southeast t Iran) (Deutsches Museum) source: Wind Turbines book By: Erich Hau Advanced Electric Machines & Power Electronics (EMPE) Lab

11 Evolution of Wind Technology (cont d) Nacelle with Geared Drive Train and Generator Advanced Electric Machines & Power Electronics (EMPE) Lab

12 Electric Machines for Wind Turbines The three main wind turbine designs: a. Fixed speed with directly grid-coupled squirrel cage generator b. Variable speed with doubly-fed induction generator c. Variable speed based on a direct-drive system and synchronous generator Past Present Future Advanced Electric Machines & Power Electronics (EMPE) Lab

13 Commercial Doubly Fed Induction Generator Advanced Electric Machines & Power Electronics (EMPE) Lab 13

14 RePower 5MW Machine Advanced Electric Machines & Power Electronics (EMPE) Lab 14

15 Low Voltage Ride Through Requirement Advanced Electric Machines & Power Electronics (EMPE) Lab 15

16 Permanent Magnet Generator (ABB) Advanced Electric Machines & Power Electronics (EMPE) Lab 16

17 Drivetrain Possibilities The generator can be coupled to the grid frequency by use of a hydrodynamic gearbox With step down gearbox stages, the generator can operate at variable frequency with added power electronics Directly driven di turbines use no stepdown gearbox stages A magnetic gear would replace step down gearbox stages Problems with traditional gearboxes such as bearings and supplies have been plaguing industry for decades Hub Hub Hub Hub Mechanically-Controlled Mechanical Gear Excitation Control from Grid Mechanical Gear Excitation Control from Grid Mechanical Gear Mechanical Gear Hydrodynamic Gear Doubly-Fed Induction Generator Wound-Field Synchronous Generator AC DC Squirrel-Cage Induction Generator Singly-Fed Generator Permanent Magnet or Squirrel-Cage Induction Generator AC DC AC DC AC DC Directly-Driven Hub AC AC DC DC Permanent Magnet Generator Non-Contact Electromechanical Grid DC AC Grid Grid Grid Grid Hub Magnetic Gear Generator AC DC DC AC Grid Advanced Electric Machines & Power Electronics (EMPE) Lab 17

18 Motivations for Magnetic Gear Development (a) DeWind wind turbine with gear (b) a directly driven Enercon wind turbine Advanced Electric Machines & Power Electronics (EMPE) Lab 18

19 Permanent Magnet Assisted Synchronous Reluctance Machines Advanced Electric Machines & Power Electronics (EMPE) Lab 19

20 The Concentric Planetary Magnetic Gear Two permanent magnet rings with stator pieces in-between to modulate magnetic flux Advanced Electric Machines & Power Electronics (EMPE) Lab 20

21 Modes of Operation outer-rotor fixed operation fixed stator segment operation Number of inner pole pairs p i, and stator pieces n s s, determine gear ratio [1] Either the outer permanent magnet ring or the stator pieces can be fixed Outer-rotor-fixed operation yields a gear ratio of n s /p i Stator-fixed operation yields a gear ratio of (n s -p i )/p i [1] Atallah, K., Calverley, S., Howe, D., Design, analysis and realisation of a high-performance magnetic gear, IEE Proceedings Electric Power Applications, Vol. 151, Issue 2, pp , Advanced Electric Machines & Power Electronics (EMPE) Lab 21

22 2D Finite Element Analysis Analysis done in Maxwell 2D finite element analysis package Two-rotating bands are simulated in the transient solver type, both having fixed rotational speed for steady-state torque transfer Advanced Electric Machines & Power Electronics (EMPE) Lab 22

23 Selected Models Number of inner pole pairs p i, and stator pieces n s, determine gear ratio Outer-rotor-fixed operation yields a gear ratio of n s /p i Stator-fixed operation yields a gear ratio of (n s -p i )/p i Gear ratios span from 3.67/1 to 13/1 13 different models, given by the ratio of outer pole pairs to inner pole pairs, are used to simulate 26 different gear ratios p o /p i Stator Pieces Fixed Gear Ratios Outer Rotor Fixed 22/6 3.67/1 4.67/1 34/6 5.67/1 6.67/1 35/6 5.83/1 6.83/1 31/5 62/1 6.2/1 72/1 7.2/1 34/5 6.8/1 7.8/1 22/4 5.5/1 6.5/1 28/4 7/1 8/1 29/4 7.25/1 8.25/1 30/4 7.5/1 8.5/1 31/4 7.75/175/1 8.75/1 20/2 10/1 11/1 21/2 10.5/1 11.5/1 24/2 12/1 13/1 Advanced Electric Machines & Power Electronics (EMPE) Lab 23

24 Results Fixing the outer permanent magnet ring provides a full gear ratio increase over fixed-stator operation Percent torque ripple was not detrimental in this change p o /p i Percent Torque Ripple of Inner Rotor Stator Fixed Outer Rotor Fixed 22/ / / / / / / / / / / / / Advanced Electric Machines & Power Electronics (EMPE) Lab 24

25 Electromagnetic Gear Advanced Electric Machines & Power Electronics (EMPE) Lab 25

26 High Frequency AC/AC Converters

27 Introduction Types of AC/AC Converter: Indirect AC/ AC Converter o DC Link AC/AC Converters o AC Link AC/AC Converters Direct AC/AC Converter Advanced Electric Machines & Power Electronics (EMPE) Lab 27

28 DC Link AC/AC Converter This type of converter is composed of two back-to-back voltage or current source converters connected via a DC link capacitor or reactor Two power conversion stages (AC/DC + DC/AC) Rectifier and inverter systems DC energy storage in the dc-link Most ASD in the current market Advanced Electric Machines & Power Electronics (EMPE) Lab 28

29 DC Link AC/AC Converter Diode Rectifier based Inverter (Diode Rectifier+ DC Link+PWM-VSI) Problems: High voltage and current stress over device High dv/dt Acoustic noise Highly polluted by harmonics DC link capacitors are bulky and are usually electrolytic Advanced Electric Machines & Power Electronics (EMPE) Lab 29

30 DC Link AC/AC Converter Back-to-Back Converter (PWM-VSR+DC Link+ PWM-VSI) Sinusoidal input/output p currents Bi-directional power flow Large DC link capacitor & input inductors required for operation Large size and volume Limited lifetime & limited high temperature operation The harmonics problem is solved, but other problems still exist here. Advanced Electric Machines & Power Electronics (EMPE) Lab 30

31 DC Link AC/AC Converter Six step current fed converter Requires a relatively large reactor Dynamic response is slower Advanced Electric Machines & Power Electronics (EMPE) Lab 31

32 Direct Conversion Matrix Converter Problems: Output/input voltage ratio limitation No input/output Isolation Advanced Electric Machines & Power Electronics (EMPE) Lab 32

33 Our Proposed High Frequency AC Link Converter Novel soft switching ac link converter High frequency ac link In ac-ac case, it uses 12 Bi-directional Switches Link is formed by an inductor-capacitor pair (low reactive ratings) Switches are turned on at zero voltage Switch turn offs are capacitance buffered Low switching losses Very compact Advanced Electric Machines & Power Electronics (EMPE) Lab 33

34 Comparing our proposed inverter with some of the existing inverters Our proposed p Kaco Blueplanet 1501 xi Fronius IG inverter series IG inverter Grid-Tie Inverter 15 Reference com/kaco Blueplanet-1501xi-p/kacoblueplanet-1501xi.htm onius/energy%20matters%20fronius%20i G%20inverter%20series%20IG%2015%20- IG%2060.pdf Power rating 1.5 kw 1.5 kw 1.5 kw Price Less than $1000 $1, $3, Weight 13 lb. (6 kg) 30.8 lbs (14 kg) lb (9 kg) Efficiency 97% 94% 94.2 % Advanced Electric Machines & Power Electronics (EMPE) Lab 34

35 Principle of Operation Link inductor charged using inputs Charged link discharged to outputs The Inductor Current Advanced Electric Machines & Power Electronics (EMPE) Lab 35

36 Principle of Operation Three input phases and one link to charge Link charging is split into two Close to unity or desired PF at input Link discharging is split intotwointervalstwo intervals as well. The sequence and the pairs calculated so as to minimize the partial resonance times while meeting the desired harmonic levels Advanced Electric Machines & Power Electronics (EMPE) Lab 36

37 Principle of Operation Mode 1 Mode 2 Advanced Electric Machines & Power Electronics (EMPE) Lab 37

38 Principle of Operation Mode 3 Mode 4 Advanced Electric Machines & Power Electronics (EMPE) Lab 38

39 Principle of Operation Mode 5 Mode 6 Advanced Electric Machines & Power Electronics (EMPE) Lab 39

40 Principle of Operation Mode 7 Mode 8 Advanced Electric Machines & Power Electronics (EMPE) Lab 40

41 Principle of Operation Modes 9-16 are the same as modes 1-8, except that the link current is reversed Advanced Electric Machines & Power Electronics (EMPE) Lab 41

42 Principle of Operation 1 st Power Cycle Advanced Electric Machines & Power Electronics (EMPE) Lab 42

43 Principle of Operation 2 nd Power Cycle Advanced Electric Machines & Power Electronics (EMPE) Lab 43

44 Applications of the proposed Inverter Our proposed converter can be used as : AC AC, AC DC, DC AC, DC DC And the most important applications are: AC drives Solar Inverter Wind Turbine Inverter Battery Utility Interface Advanced Electric Machines & Power Electronics (EMPE) Lab 44

45 Simulation Results AC-AC (15 kw) Link frequency Peak Link current Link Inductance Link Capacitance 10 khz 110 A 140 µh 0.2 µf Advanced Electric Machines & Power Electronics (EMPE) Lab 45

46 Simulation Results Advanced Electric Machines & Power Electronics (EMPE) Lab 46

47 Simulation Results Advanced Electric Machines & Power Electronics (EMPE) Lab 47

48 Simulation Results DC-AC: Solar Converter Advanced Electric Machines & Power Electronics (EMPE) Lab 48

49 Simulation Results Advanced Electric Machines & Power Electronics (EMPE) Lab 49

50 Simulation Results Power Reversal DC/AC We have achieved power reversal time of less than 1 ms. AC/DC Advanced Electric Machines & Power Electronics (EMPE) Lab 50

51 Simulation Results Input Filtered current Input Voltage Advanced Electric Machines & Power Electronics (EMPE) Lab 51

52 Simulation Results Output Filtered current Output Voltage Advanced Electric Machines & Power Electronics (EMPE) Lab 52

53 Actual Converter Advanced Electric Machines & Power Electronics (EMPE) Lab 53

54 Actual Converter results Low power results Advanced Electric Machines & Power Electronics (EMPE) Lab 54

55 Actual Converter results Link voltage and Link Current Advanced Electric Machines & Power Electronics (EMPE) Lab 55

56 Conclusion The proposed converter is a soft switched high frequency AC link converter The efficiency is high (around 98%) It is very compact Switching losses are very small due to the design and control method The size of the converter is very compact It can even be used for power reversal application, and simulations have shown 1ms power reversal time. Advanced Electric Machines & Power Electronics (EMPE) Lab 56

57 Flywheel Energy Storage System Fundamentals Charging Mode of the Flywheel Power in Input electronics Motor Flywheel (stored) T Ap T Bp T Cp T Sp T Tp T Rp v A v B v C i A i B i C L r u A u R ir C u B u S i S u C u T T i TC T T Bn Cn T An T Rn T Sn T T Tn v RS v ST PMSM Flywheel C r Line-Side Converter Machin-Side Converter Discharging Mode of the Flywheel Power out Output electronics Generator Flywheel Advanced Electric Machines & Power Electronics (EMPE) Lab 57

58 Comparison of High Speed and Low Speed 2 MW Machines 73 (1.85m) highh Conventional 2MW Machines Height 73 (1.85 m) Length 90 (2.28 m) Weight 11,310 lbs. (5130 kg) Power Density 0.39 kw/kg (326 kw/m 3 ) Calnetix 2MW High Speed Machines 28 Height 28 (0.71 m) (0.71m) high Length 53 (1.34 m) Weight 1650 lbs. (748 kg) Power Density 2.67 kw/kg (3770 kw/m 3 ) Advanced Electric Machines & Power Electronics (EMPE) Lab 58

59 Limiting Geometric Design Considerations Stored Energy 1 2 Moment of inertia of the flywheel E = Jω 2 2 rmh J = 2 Radius Mass Height (length) of the flywheel The square of the rotational velocity of the flywheel Limiting Geometric Design Considerations Tip speed ( Vt = r ω ) due to the strength of the materials Steel constructions: 220 to 240 m/s Composite structures: more than 1000 m/s Rotor dynamic behaviors The various rotor critical (resonant) speeds The ability of the flywheel assembly to avoid or traverse them without failure Advanced Electric Machines & Power Electronics (EMPE) Lab 9/1/

60 High Speed Flywheel High Speed Flywheel Operate above 10,000 rpm up to 100,000 rpm A flywheel with a low mass but a high limit for the mechanical tension The flywheel has a compound construction with a strength 5 times higher than steel The mass moment of inertia, weights and dimensions are relatively small The rotor runs in a vacuum and is supported by magnetic bearings The magnetic bearing requires a second set of bearings for emergency The output frequency of the synchronous generator is in the khz range Due to thermal reasons the rotor has no windings A drawback is the high price of the system Advanced Electric Machines & Power Electronics (EMPE) Lab 9/1/

61 An Example of Flywheel Energy Storage System (source: VYCON) Non contact fully levitated rotor Secondary Mechanical Bearings for backup only High Cycle Full Cycle every 15 minutes DSP Controlled 140 kw for 15 Seconds 1. Flywheel 4. Flywheel Controller 2. GUI 5. Power Stack 3. Master Controller 6. Vacuum Pump Advanced Electric Machines & Power Electronics (EMPE) Lab 9/1/

62 Experimental Set up Advanced Electric Machines & Power Electronics (EMPE) Lab 62