TUTORIAL II Electric Drives 101 & Variable-Frequency Drives

TUTORIAL IIElectric Drives 101 &Variable-Frequency Drives1.2.Basic Principles: Ned Mohan UofMNPractical Aspects: Robin Priestley, RockwellAutomation50th MIPSYCONMinneapolis, MNNovember 6, 20141

Part 1Basic Principles – Ned MohanPart 2Practical Aspects - Robin Priestley2

Part 1Variable-Frequency Electric Drives areessential in wind-turbines and in pumps/compressors in oil/gas industry spurred byfracking.This tutorial will present their operatingprinciple requiring only basic EE concepts asprerequisites.3

References:www.wiley.com/college/mohan4

Efficiency Improvement by Motor DrivesLighting 19%ThrottlingValveIT14%HVAC 16%Motors 51%OutletMOTORInletConstantfrequencyAC EssentiallyConstant SpeedPumpOutletAdjustableSpeed Drive(ASD)ConstantfrequencyACInletAdjustable frequencyelectric converterAdjustable Pumpspeed5

Role of Electric Drives inHarnessing Wind Energy6

Wind Resource in the U.S.Fig. 3-7 Wind-resource map of the United States [6].20% of the U.S. Power Productionby 2030 can be by Wind.7

WIND161kVV0TimeLow-VoltageRide-Through0 690V10 60 HzGenerator690VPower ElectronicsConverters34.5kV60 Hz8

GE 1.5 MW Turbinem/s1m / s 2.25 miles / hrSource:9

Power from the tyWind turbinePwind13 AV2Source: 1 Pturbine C p Pwind C p AV 3 2 R mechV10

Interface for WindGenerator:Power ElectronicsInterfaceConverterWind GeneratorUtilityLoad GridSourceController Ned Mohan, 201211

Wind Generation using an ACGenerator Connected through PowerElectronics12

Wind Generation using a Doubly-FedInduction GeneratorWound rotorInduction CGrid-sideConverter13

Motor DrivesElectricDrivefixedformPowerProcessingUnit (PPU)Motorspeed /positionadjustableformElectric Source(utility)LoadSensorsmeasuredspeed/ positionControllerPowerSignalinput comm and(speed / position)14

Power Electronics Basics:Power Semiconductors15

Switch-Mode Conversion: Switching Power-Poleas the Building Block qA 1VinvvAA vA--Vin00tqA(a)(b)Figure 1-20 Switching power-pole as the building block in converters.16

Pulse-Width Modulation (PWM) of the Switching Power-PoleqAidA iAtTupTsvA-dA0d A Ts Vin1vA-q A 1or 0VinvA0(a)(b)d A (1-21 TupPWM/ Ts ) of the switching power-pole.FigurevA TupTsVin d AVin170 dA 1t

Switching Power-Pole in a Buck DC-DC Converter:An ExampleqAiin0 iLVin 1vAtd ATsTsVinvA vAVo 0qAtiL0tiin(a)0t(b)FigureBuckV 1-22v Switchingd V power-pole 0in a V Vconverter.oAA ino18in

Synthesis of Low-Frequency AC:vaNVd0vaNvaN00TsvaN t

InverterInverterVdcabcNVdc vaN vbNvcN0.5Vdc020

Interface for WindGeneratorInverterVdcabcNGen21

Electric Machines Basics:161kVV0TimeLow-VoltageRide-Through0 690V10 60 HzGenerator690VPower ElectronicsConverters34.5kV60 Hz22

AC MachinesSynchronous MachinesInduction Machinesb axisib2 / 32 / 32 / 3iaa axisicc axis23

24

Basic PrinciplesElectromagnetic Force:external B fieldBfemfemfemiresultant(a)subtract(b)add(c)fem B i[ Nm][T ] [ A] [ m]25

Induced Voltage:B (into paper) fq fq B (into papufq (a)e B l[V ](b)u[T ] [ m][ m / s ]26

Three-Phase StatorWindings:27

Synchronous ions/alternator.html syn pf ( )2 228

eaf synAt the Condition for Max Torque/Amp:Tem I a Copyright N. Mohan 201029

Production of Magnetic Fieldbaima(a)imbcimca t0 o 60 o 120 o 180 o 240 o 300 o 360 ob) t 0o t 60 o(c)aacbcbbcbcaa t 120 oac60 ob120 o(e) t 180 oacb180 occbb vectors.htmlaa30 t 240 oo

Equivalent Circuiteaf mea , AR I aea eaf ea , AR 31

Current Controlconv1conv2utilityLoadcontrollerFigure 12-1 Voltage-link system.32

Squirrel-Cage Induction ilityWind turbineb axisib2 / 3a axis2 / 32 / 3iaicc axis33

Short-circuited RotorTransformer Analogy mim i2 i2 v1 N1N2Load34

Electrically Open-circuited RotorVc va vb vc vbib I mcI mb iaVa n v avc icVbI ma35

Production of Magnetic Fieldbaima(a)imbcimca t0 o 60 o 120 o 180 o 240 o 300 o 360 ob) t 0o t 60 o(c)aacbcbbcbcaa t 120 oac60 ob120 o(e) t 180 oacbva ea180 o syn2 2 ( ) fpccbb vectors.htmlaa36 t 240 oo

Induced Voltages in Rotor Bars: m synMotoring Mode slip ( syn m ) ebar slipat t 0 m synvsa axis syn Bms37

Induced Currents in Rotor Bars: msynMotoring Modeibar ebar slipat t 0 m synvsa axis syn Bmsfrontend-ringebar Rbaribar ( )back end-ringMax Torque/Amp38

Torque – Speed CharacteristicsTem,ratedV ConstantfTem ,ratedTem0 m syn, rated m, rated slip,ratedTem qmoviemotgen.html39

Slip frequency (fslip) in the rotor circuit slip syn - m slips synf slip s f40

How does an inductionmotor work? Load Torque goes upSpeed slows downSlip speed goes upRotor-bar induced voltages go upRotor-bar currents go upElectromagnetic torque goes up41

Generator Mode: InducedVoltages in Rotor Bars m synat t 0 m synvsa axis syn Bms42

Induced Currents in RotorBars m syn43

Torque – Speed CharacteristicsTem,ratedTem ,ratedTem0 m syn, rated m, rated ions/sqmoviemotgen.html44

MMF Due to Rotor Bar Currents m synat t 0 m synvsa axis syn Bms45

Controlling TorqueTem0 m46

Doubly-Fed Induction Generator47

Doubly-Fed Induction GeneratorWound rotorInduction CGrid-sideConverter48

Ps , QsPemirPEConverterRotorerRr j slip L rvrPr , Qr slip , sPs(Speed)(mode) (sub-syn)Ps (sub-syn)(super-syn)(super-syn)PrQrQr' - - ---- (generating)Ps (generating)Ps (generating)Ps (generating)49

Effect of Reactive Power onBus VoltageVbus VTh jX Th II jX Th IjX Th I VThVbusVThjX Th IVbus VbusjX Th I VTh(a)(b)I50

Summary of Generator Types: Synchronous Generators (torque is controlled bystator current)– Permanent Magnet– DC Excitation Induction Generators– Squirrel-cage (torque is controlled by statorfrequency)– Wound Rotor DFIG (torque is controlled by injectedrotor currents)51

Electric Drives 101 & Variable-Frequency Drives 1. Basic Principles: Ned Mohan UofMN 2. Practical Aspects: Robin Priestley, Rockwell Automation 50th MIPSYCON . Electric Machines Basics: 0 690 10 60 V Hz 34.5kV 161kV Power Elec