Comparitive Loss Evaluation of Si IGBT Versus Sic Mosfet (Silicon Carbide) for 3 Phase Spwm Inverter

Transcription

1 ndian Journal of Science and Technology, Vol 8(8), DO:.7485/ijst/5/v8i8/798, October 5 SSN (Print) : SSN (Online) : Coparitive Loss Evaluation of Si GBT Versus Sic Mosfet (Silicon Carbide) for 3 Phase Spw nverter Trinadh Mathe and K. Narsiha Raju KL University, Vijaywada, Andhra Pradesh, ndia; athe.trinadh@gail.co Departent of EEE, KL University, Vijaywada, Andhra Pradesh, ndia; narsiharaju_eee@kluniversity.in Abstract Background/Objectives: Reducing the losses of 3 phase spw level inverter by replacing the present sei conductor switches which are si igbt (silicon) with the latest sic osfet (silicon carbide) switches. Methods/Statistical Analysis: si igbt (silicon) and sic osfet (silicon carbide) are odelled in pspice using the data sheet paraeters and the odelled switches are used to siulate the three phase spw inverter and the losses of the syste are copared. Findings: The three phase spw inverter siulated at switching freuency ranges of 5khz, 8khz, khz, 5khz and it had been observed that the losses of the 3 phase spw sic osfet inverter are 9% less for 5khz switching freuency, 34% less for switching freuency of 8khz, 37% less for switching freuency of khz, 4% less for the switching freuency of 5khz over the 3 phase spw inverter based on si igbt. Application/proveents: The sic osfet can replace the si igbt in 3 phase spw inverter syste for better efficiency and the pspice siulations showed siilar results showing that sic osfet is efficient than si igbt based three phase spw inverter. Keywords: nsulated Gate bi Polar Transistor (GBT), Losses, Metal Oxide Sei Conductor Field Effect Transistor (MOS- FET), Silicon (Si), Silicon Carbide (SC), Sine Pulse Width Modulation (SPWM). ntroduction n 99 UMOSFET was first aong sic osfet technology that was developed by cree. Later in 997 Accufet (Accuulation-channel fet) was developed in NC State University by Dr. Baliga's group using 6h-sic dos geoetry and it was the first high voltage (35V) planar vertical sic (Accufet) developed with buried iplanted region for shielding the gate oxide. Later in.4 KV 4h-sic Diosfet having specific on state resistance of 4Ωc was deonstrated by cree 3. n 4 4,5 Dr. Jaes Coopers group of Purdue University developed 3KV, 5KV Uosfet of 4h-sic having junction terination extension (jte) and trench oxide protection. n 4 6 kv, 4h-sic was developed by cree. Large effort is put into sic research and developent in recent years as the critical electric field of 4h-sic is 8. ties larger than that of si. So there are ore advantages in using sic s as their electric break down field, electron saturated drift velocity, theral conductivity, irradiation tolerance aking sic available for high voltage, high teperature and freuency and also cobining low power loss 8,9. Considering case of kw inverters used to drive otors they conventionally eploy si igbts that operate at ax teperatures of 5ºc. That has to be ounted on larger heat sink. As they produce ore losses on increasing the switching freuency and has to be cooled using forced air cooling or water cooling as their perforance is liiting sic has gained ore attention.. Seiconductor Property Related Application Advantages Sic s are expected to enable superior perforance copared to si s. n view of sic's excellent electrical and physical properties. Author for correspondence

2 Coparitive Loss Evaluation of Si GBT Versus Sic Mosfet (Silicon Carbide) for 3 Phase Spw nverter Table. Sei conductor property based advantages of silicon carbide (sic) aterial over silicon (si) aterial Seiconductor Properties (SiC/Si) Device Expected Perfprance (Sic / Si) Euipent Lpact Melting Point X High Teperature Operation x Band Gap 3X High breakdown Voltage Device nuber x reduction Breakdown Lield X High Current density Sall size High Low Loss /x efficiency Thenal Conductivity 3X High Speed x Sall size High Speed Saturation Carrier Velocity X Achieved Perforance (>KV) Siple heat sinc x (3 degree C) 3x (35 degree C).5 x(9.5kv) [] x (.5kv) /4x (3 oh csu) [3] /3x (69 oh csu) [4] x (8- ns) [5] 3 x (47ns) [4]. Heat Sink Higher elting point and higher band gap of the sic based would allow higher teperature operation enabling the use of saller heat sink copared to si based.. Device Count Higher break down field would result in having higher break down voltage reducing the count..3 Efficiency Higher band gap and higher break down field and higher theral conductivity are the reasons for sic having lower losses and higher efficiency. index is also taken unity the syste specification is in Table. Table. Syste specification of si igbt based 3 phase inverter. Dc voltage 586 Modulation ethod SPWM Modulation index Switching freuency 5KHZ,OKHZ,5KHZ Power factor Motor peak current Power rating 38A KW.4 Speed Higher theral conductivity and higher saturation carrier velocity would result in saller seize and high speed operation. 3. Syste Specification Two 3 phase spw inverters are designed basing on si igbt and sic osfets. Figure shows the circuit for the si igbt base level 3 phase spw inverter. Figure shows the circuit for sic osfet based level 3 phase spw inverter. For si igbt 3 phase inverter six V, 4A single si igbts are considered. The inverter operated at 3 ranges of switching freuencies 5khz, khz and 5khz. The inverter is controlled using spw techniue. For easy evaluation the power factor is taken as unity and the odulation Figure. Si igbt based 3 phase inverter with r load. Vol 8 (8) October 5 ndian Journal of Science and Technology

3 Trinadh Mathe and K. Narsiha Raju Table 3. Syste specification of si igbt based 3 phase inverter Dc voltage 586 Modulation ethod SPWM Modulation index Switching freuency 5KHZ,OKHZ,5KHZ Power factor Motor peak current 38A Power rating KW Figure 4 shows the forward characteristics of the sic osfet used for the evaluation. Figure 4. Sic osfet characteristics data sheet. 5. Loss Calculation Figure. Sic osfet based 3 phase inverter with r load. 4. Device Paraaters The Figures were taken fro the data sheets of respective si igbt and sic osfet. Figure 3 shows the forward characteristics of the si igbt used for the evaluation The conversion losses in the inverter can be divided in two categories. Conduction loss Switching loss Table 4. Paraeter coparison of si igbt vs sic osfet considering the sae freewheeling diode for both si igbt and sic osfet S GBT SC MOSFET Rating V fo 3.5V 4.V r f.7ω.66ω Eon 3.J 8µJ Eoff.4J 64 µj Table 5. Paraeter coparison freewheeling diode of si igbt vs sic osfet Si GBT freewheeling diode Sic osfet freewheeling diode V d.3.3 R d.836ω.836ω Figure 3. Si igbt characteristics data sheet. Vol 8 (8) October 5 ndian Journal of Science and Technology 3

4 Coparitive Loss Evaluation of Si GBT Versus Sic Mosfet (Silicon Carbide) for 3 Phase Spw nverter 5. Conduction Losses The conduction losses are due to on-state voltage drop. They calculated by averaging the conduction losses in each switching cycle as shown in below euation: T Pc = Vf( wt) i( wt) dwt () T Where P C is the total conduction losses, switching period is T. V f (wt) is the forward voltage of the, i (wt) is the current flow through the in the conduction period. The value of V f (wt) is calculated as follow: V = V rit () () f fo f Where V f is the forward voltage at no load and forward resistance is r f. The values of V f and r f are calculated using the datasheet of characteristics provided by anufacturing copanies as shown in Figure 3, 4. The r f is the ratio between the collector eitter voltage difference and the collector current difference r f = ΔVce/ Δc while V f is the value in the curve corresponding to the actual collector current flow in the. Substituting the expression for the forward voltage in Euation () into Euation () gives P= V r c f av f rs Conduction loss in osfet is given by the euation. P R c( Q) = RMSQ DS ON Where av and rs are the average and the rs current passing through the in the conduction period. These are calculated as follows: i av = T T T T rs = i i () t dw i () t dw 5. Switching Losses The switching losses are the total su of on-state switching losses and turn-off switching losses. They depend on the characteristics, switching freuency and current. The switching energy is expressed as a function of the current as: i Esw = k Where k is got fro the switching energy graph in the datasheet. The switching loss for the is calculated as: P sw fs = p T s k i dwt 6. Evaluation of Conversion Losses in Two-Level Converters f the load current is assued as a (wt) = Sin (wt-) then the leg phase voltage is defined as V a (wt) = V Sin (wt-) and the duty cycle for the switches is: dt= dt4 = [ M sin wt ] dt4 = dd= dt= [ Msin wt] The average and rs currents for GBTs T and T are calculated using respective forulae and the duty cycle defined as below: p M cos T, av = dt id a w p = p p M cos T 4, av = dt 4id a w p = p p M cos T, rs = dt id a w p = p M cos T 4, rs = dt 4 adw p = The average and rs currents for the lower freewheeling diode are siilar to that of the upper GBT but in opposite direction therefore: M cos D, av = T 4, av = p M cos D 4, av = T, av = p M cos D, rs = T 4, rs = M cos D 4, rs = T 4, rs = The free-wheeling diode is switched on/off very fast copared to the GBT so its switching losses are relatively sall copared to that in an GBT, therefore are not considered in the calculation. The switching losses for the GBT are calculated using below euation as: kf kf Psw = t d t= p p p s s sin( w ) w 7. Coparisions By substituting the values of the paraeters in the loss evaluation forulae the respective values of the losses have been tabulated in the below Tables 4,5,6,7 for the respective switching freuencies of 5khz, 8khz, khz, 5khz. 4 Vol 8 (8) October 5 ndian Journal of Science and Technology

5 Trinadh Mathe and K. Narsiha Raju Table 6. Power loss coparison (F S = 5KHZ) Si GBT syste Sic osfet syste Conduction loss (per GBT w Mosfet- 59.9w Switching loss per 3.w.84w Total inverter loss w w Table 9. Power loss coparison (F S = 5KHZ) Si GBT syste Sic osfet syste Conduction loss (per GBT w Mosfet- 59.9w Switching loss per 39.6w 5.44w Total inverter loss w w Table 7. Power loss coparison (F S = 8KHZ) Si GBT syste Sic osfet syste Conduction loss (per GBT w Mosfet- 59.9w Switching loss per.w.9w Total inverter loss 565.8w 37.w Table 8. Power loss coparison (F S = KHZ) Si GBT syste Sic osfet syste Conduction loss (per GBT w Mosfet- 59.9w Switching loss per 6.4w 3.6w Total inverter loss w 375.4w Figure 7. Loss coparison of siulated scenarios of switching freuencies of 5khz, khz, 5khz for Si GBT versus sic osfet. The odelled si igbt based level three phase spw inverter with odelled switches was siulated and copared with sic osfet based level three phase spw Figure 5. Pspice siulated si GBT based three phase spw inverter (FS = KHZ). Vol 8 (8) October 5 ndian Journal of Science and Technology 5

6 Coparitive Loss Evaluation of Si GBT Versus Sic Mosfet (Silicon Carbide) for 3 Phase Spw nverter Figure 6. Pspice siulated sic osfet based three phase spw inverter (FS = KHZ). inverter using orcad pspice as siulation tool. Figures 5 and 6 show the scenarios one with si igbt and sic osfet at switching freuency of khz. Power loss is copared in orcad pspice at various switching freuencies and average power loss is easured across each switch for s and copared. 8. Conclusion n su, a kw sic osfet base 3 phase spw inverter syste is designed and copared with that of si igbt base three phase spw inverter at switching freuency ranges of 5khz, 8khz,,khz, 5khz and it had been observed that the losses of the 3 phase spw sic osfet inverter where 9% less for 5khz switching freuency, 34% less for switching freuency of 8khz, 37% less for switching freuency of khz, 4% less for the switching freuency of 5khz over the 3 phase spw inverter based on si igbt which in turn shows that the sic osfet can be replaced by si igbt in 3 phase spw inverter syste for better efficiency and the pspice siulations showed siilar results showing that sic osfet is efficient than si igbt based three phase spw inverter. 9. References. Palour JW, Edond JA, Kong HS, Carter CH, Jr. 6Hsilicon carbide power s for aerospace applications. Proceedings of 8th ntersociety Energy Conversion Energy Conference; Atlanta: Georgia. 993.p Shenoy MP, Baliga BJ. The planar 6H-SiC ACCUFET: A new high-voltage power MOSFET structure. EEE Electron Device Letters. Dec 997; 8(): Agarwal A, Ryu SH, Das M. Large area 4H-SiC power MOSFETs. Proceedings of the 3th nternational Syposiu on Power Seiconductor Devices and Cs. SPSD. Jun.p Li Y, Cooper JA, Jr, Capano MA. High-Voltage (3 kv) UMOSFETS in 4H-SiC. EEE Transactions on Electron Devices. Jun ; 49(6): Khan A, Cooper JA, Jr, Capano MA, saacs-sith T, Willias JR. High-voltage UMOSFETs in 4H-SiC. nternational Syposiu on Power Seiconductor Devices; Santa Fe, NM. Jun ; 3-7: Ryu SH, Krishnaswai S, O Loughlin M. -kv, 3-/spl Oega//spl iddot/c/sup /4H-SiC power DMOSFETs. EEE Electron Device Letters. Aug 4; 5(8): Baliga BJ. Power seiconductor s for variable-freuency drives. Proceedings of the EEE 994. Aug 994; 8(8):. 8. Chang HR, Hanna E, Radun AV. Developent and deonstration of silicon carbide (SiC) otor drive inverter odules. Power Electronics Specialist Conference PESC 3; Acapulco: Mexico. 3; : Zhang H, Tolbert LM. A SiC-based converter as a utility interface for a battery syste. Conference Record of the 6 EEE ndustry Applications Conference Forty-First AS Annual Meeting; Tapa: FL. Oct 6; : Sugaww Y, Y DT, Pakuand T. SPSD, ; p. 7.. Hui P, et al. Evaluation of losses in VSC-HVDC transission syste. n: Power and energy society general eeting conversion and delivery of electrical energy in the st century. 8 EEE. 8; 7(9): 6. 6 Vol 8 (8) October 5 ndian Journal of Science and Technology

7 Trinadh Mathe and K. Narsiha Raju. Blaabjerg F, et al. Power losses in PWM-VS inverter using NPT or PT GBT s. EEE Transactions on Power Electron. 995; (3): Tae-Jin K, et al. The analysis of conduction and switching losses in ulti-level inverter syste. n: Power electronics specialist s conference, PESC. EEE 3nd Annual, Vancouver, BC. ; 3: Oh KS. Application note 96: GBT basics. FARCHLD Seiconductor Corporation Rev. A; Feb. 5. Kolar JW, et al. nfluence of the odulation ethod on the conduction and switching losses of a PWM converter syste. EEE Transactions on ndustrial Applications. 99; 7(6): Yushu Z, et al. Voltage source converter in high voltage application: Multilevel versus two-level converters. Presented at the ACDC, the 9th nternational Conference on AC and DC Power Transission; London: UK. Oct.p Yazdani A, ravani R. Voltage-sourced converters in power systes: Modelling control, and applications. Hoboken (New Jersey): John Wiley and Sons nc.;. Vol 8 (8) October 5 ndian Journal of Science and Technology 7