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CASCADED MULTILEVEL INVERTER FOR HYBRID ELECTRIC VEHICLES
Authors Ankit Kumar Verma P. R. Thakura K.C.Jana and G.Buja (Fellow Member, IEEE)
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OBJECTIVE HEV are used for increase fuel efficiency and to tackle pollution problems. To make a transformer less multilevel inverter for high voltage and high current HEV. The cascaded inverter is IGBT based and it is fired in a sequence. The simulation has been done in PSIM and MATLAB and its responses match the theoretical concept of multilevel inverter.
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INTRODUCTION HEV Multilevel inverters ARCHITECTURE ENGINE EFFICIENCY
INCREASE FUEL EMISSIONS POWER ELECTRONICS MEET HIGH POWER DEMANDS using BATTERIES. Multilevel inverters HIGH VOLTAGES AND HIGH POWER NO TRANSFORMERS A STAIRCASE OUTPUT (similar to sinusoidal output waveform ) LOW HARMONIC DISTORTION INCREASE IN VOLTAGE LEVELS
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HYBRID ELECTRIC VEHICLES
C O N F I G U R A T I O N S Series : Single path to power the wheels. Two energy sources. The fuel tank feeds engine coupled to generator to charge battery which provides electrical energy to motor/generator to power the wheels. Motor/generator also used to recharge the battery during deceleration and braking. Parallel : Two parallel paths - engine path and electrical path to power the wheels. The transmission couples motor or generator and engine, allowing either/ both to power the wheels. Controlling is complex. Series-parallel: Both Series and Parallel energy paths. A system of motors and/or generators that sometimes includes a gearing or power split device couples allows engine to recharge battery. Variations on this configuration can be very complex or simple, depending on the number of motors/generators and how they are used. Configuration classified as Complex hybrids (Toyota Prius and Ford Escape Hybrids), Split-Parallel hybrids, or Power-Split hybrids. 4
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Series HEV pe = Mechanical Power ps = Stored Power or pe pw ps Here
B S G ICE W M F pw ps Here F = Fuel Tank ICE = Internal Combustion Engine G = Generator S = Energy Storage System B = Common Bus M = Motor W = Wheels pe = Mechanical Power ps = Stored Power or Power drawn by electric drive train ps = Propulsion Power drawn for wheels Electrical Link Hydraulic Link Mechanical Link
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Parallel HEV pm = Remaining Power by Electric drivetrain Here
S ICE W M F A pe pw pm ps Here pm = Remaining Power by Electric drivetrain A = adder Which draws the propulsion power for wheels cwe and cwm are coefficients that depend on gear arrangement of A.
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Series-Parallel HEV pe pd pb pm pw ps
ICE W M F A P pb pm pw ps It’s a combination of series and parallel HEV. P divides the power generated by ICE in two parts: Pd (mechanical form) and Pb(electrical form). Addition of Pd and Pw gives propulsion power for wheels (Pw). So splitting of ICE power is obtained by two ways: 1. an apparatus based on a mechanical devices. 2. an apparatus based on electrical device.
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TAXONOMY OF MULTILEVEL INVERTER
Neutral Point Clamped (NPC) Inverter Cascaded Flyback Capacitor
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DIODE CLAMPED Proposed by Nabea,Takahasi and Akagi in Switches are switched in such manner that it will give stair case output. Here for each step four switches are ON and capacitor have equal charge(Vdc/4) . There are m capacitors and 2(m-1) switches and (m-1)*(m-2)diode per phase. Advantages All of the phase share a common DC bus, which minimizes the capacitance requirement of the converter. The capacitor can be pre-charged as a group. Efficiency is high for fundamental frequency switching. Disadvantages Real power flow is difficult as the intermediate DC levels will tend to overcharge or discharge without precise monitoring and control. The number of clamping diodes required is quadratic related to levels which is cumbersome with units of high number of levels.
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FLYBACK CAPACITOR Advantages : Disadvantages:
Introduced by Meynard and Foch in Structure similar to diode clamped. The voltage increment between two adjacent capacitor leg gives the size of the voltage steps in output waveform. There are (m-1) *(m-2)/2 capacitor and 2(m-1) switches per phase Advantages : Phase redundancies are available for balancing the voltage levels of the capacitor. Real and reactive power flow can be controlled. The large number of capacitor enables to ride through short duration outages and deep voltage sags. Disadvantages: Control is complicated to track the voltage levels for all of the capacitors and pre-charging all of them to same level and startup is complex. Switching utilization and efficiency are poor for real power transmission. Large number of capacitor makes it expensive and bulky.
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Multilevel Inverter Topologies
Per-Phase Diagram
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Cascaded Multilevel Inverters
Topics to be discussed H-Bridge Inverter Cascaded Multilevel Inverter
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H-Bridge Inverter S1 and S4; S1 and S2; S3 and S2; S3 and S4;
180o conduction mode Complementary Switch pairs: S1 and S4; S3 and S2; Firing Switch pairs at the same time: S1 and S2; S3 and S4;
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PWM technique vAB from -Vd to +Vd PWM: or from +Vd to –Vd
Just we can see that the output waveform is modulated.
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CHB Multi-level Inverter Topologies
Eleven-Level CHB Inverter Output Voltage Level Here Van = Phase Voltage m = no. of levels and m = 2s+1 where s = no. of H-bridge
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Phase Voltage Fourier series
Waveform of vAN is composed of Eleven voltage levels: 5E, 4E, 3E, 2E, E, 0, -E, -2E, -3E, -4E, and -5E
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Calculation of Switching Angles
Set of Non-linear Transcendental Equation Solving the above equation by NEWTON RAPHSON iterative method and considering M = 0.8 then m = 11 (for Eleven-Level cascaded Multilevel Inverter)
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Simulation and Results
PSIM MATLAB
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Eleven level Cascaded Multilevel Inverter
Simulation on PSIM
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Output Voltage for Eleven Level CMI
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Input – Output Response
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Model of Eleven-level CMI in MATLAB
Controlling block
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Analysis of waveform in MATLAB
(c)Line-to-line voltage (d)Phase voltage at modulation index 0.9 (b) (a) (c) (d) Line-to-line voltage Phase voltage at modulation index 0.8 From the analysis its seen that The Total Harmonic Distortion (THD) is less than 5%
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Change of Modulation Index
(b) Change of Phase voltage and Line-to-line voltage at different modulation index (0.8 and 0.9) using MATLAB
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THREE PHASE SQUIRREL CAGE INDUCTION MOTOR
Specifiation THREE PHASE SQUIRREL CAGE INDUCTION MOTOR Power = 20 kW, line-line voltage = 400 V, frequency = 50Hz, stator resistance (Rs) = Ω, rotor resistance (Rr) = Ω, stator leakage inductance (Ls) = 991 μH, rotor leakage inductance (Lr) = 991μH, mutual inductance (M) = mH, moment of inertia = JKg.m2, friction factor = FNms
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CMI circuit for application in laboratory
H-bridge Pulses to the H-Bridge is given by DSPACE/OPAL-RT Eleven-level CMI
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Selection of components for Cascaded H-Bridge Inverter
Motor Ratings Vl-l=400V, Prated=5HP, Cosθ = 0.8 = power fatcor IGBT ratings Vp= Vl-l/√3 Vp(peak)= Vpx √2 V1max= 4 sVdc/π Vp(peak) = V1max Vpx √2 = 4 sVdc/π
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Isolation transformer ratings
Capacitor ratings Isolation transformer ratings Taking a frequency of 50 Hz, the dc ripple would have a frequency of 50x6 Hz =300 Hz for a three phase rectifier. Transformer rating for prototype will be 100V and 1.5A and 300VA with a turn ratio of 1:2 and it should be electrically isolated. If the Transformer is not for prototype then rating will be 307 V and 23A and 7KVA with a turn ratio of 1:2 and it should be electrically isolated.
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Controlling of Five-level CMI for lab experiment
Gate pulses for the Five-level CHB inverter is provided by DSPACE or OPAL-RT. Simulation is done on MATLAB as RT-simulators are accessible by MATLAB
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Gate driver (HIP-4081A) PC Board schematic layout
A0 and B0 is the voltage we get from one H-bridge IN1 and IN2 are gate pulses provided from DSPACE or OPEL-R B+ and Com gets the power from the capacitor +12V supply is provided after regulating the voltage
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Components Rating No. of pieces
Components required for Gate driver (HIP-4081A) Components Rating No. of pieces CD4096UB (cmos inverter) 1µA and 18V 1 Capacitor C6 and C5 12V, 4.7mF 12V, 0.22mF (each) C3 and C4 (ceramic) 100V and 0.1 mF Bootstrap Diodes CR1 and CR2 (fast recovery diodes) 100V and 1A Resistors R33 and R34 (for deatime control) 100kW-500kW R30 and R31 (current limiting signal) 0.1W-2W
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Components selected and order placed for prototype of
CHB Inverter Components rating No. of pieces P-MOSFET IRF 520 100V 9A 24 CAPACITOR 280µF 6 RECTIFIER MODULE 8AKBU8G VPIV = 400V Vrms = 280 Ifwd(avg) = 8A GATE DRIVER IC HIP4081A VDD = 15V Igate(peak) = 2.5A VIN ≤ 2V ISOLATION TRANSFORMER 1.5A 300VA 3
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Conclusion In this work cascaded multilevel inverter is interfaced with electric drive of HEVs because of following special features: The number of components used in cascaded is less than other types of multilevel inverters like diode clamped and flyback capacitor multilevel inverter. It is suitable for high voltage and high current rating electric drives. HEV has high current and low voltage rating in order to reduce weight of the batteries. Cascaded multilevel inverters are switched at low frequency so it will create low noise which can be suppressed and comfortable for driving HEVs. This converter will have high power factor and also have less EMI and voltage unbalance problem.
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References: C C Chan, “The State of the Art of Electric, Hybrid, and Fuel Cell Vehicles”, proceeding of IEEE, 2007. M. Ehsani, Y. Gao, Ali Emadi, Modern electric ,Hybrid Electric and Fuel Cell Vehicles; Fundamentals theory and design 2nd edition, CRC Press , 2009. C C Chan and K.T. Chau, Modern Electric Vehicles Technology, Oxford University Press, 2001. L. M. Tolbert and F. Z. Peng, “Multilevel inverters for large automotive drives,” All Electric Combat Vehicle 2nd Int. Conf.,Dearborn, MI, vol. 2, pp. 209–214 ,June 8–12, 1997. P.R.Thakur et.al,” Technology and role of power split apparatus for hybrid electric vehicles, IEEE, IECON, Taiwan, Nov. 2007, pp A.Emadi, K.Rajashekara, S.S.Williamson and S.M.Lukic, ”Topological overview of hybrid electric and fuel cell vehicular power system architectures and configurations”, IEEE Trans. on Vehicular Technology, vol.54, no.3, pp , May 2005. “The Insight-Honda’s First Hybrid Electric Vehicle”, Special Auto Technology, pp , Converters used in railways. K.C. Jana, S. Biswas and P.R.Thakura “A simple and generalized space vector pulse width modulation of multi-level voltage source inverter” IEEE, ICIT-06 Mumbai, Dec.2006. M.H.Rashid, Fundamental of power electronics, Prentice Hall India, 2nd Edition, Delhi, 2004. Leon M. Tolbert, Fang Zheng Peng, and Thomas G. Habetler,“Multilevel converters for large electric drives” IEEE Trans. Indus. Applicat., vol. 35, no.1, pp , Jan. /Feb., 1999. J. S. Lai and F. Z. Peng, “Multilevel converters—A new breed of power converters,” IEEE Trans. Ind. Applicat., vol. 32, pp , May/June 1996.
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Thanks
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