Determination of Energy Loss in Power Voltage Inverters for Power Supply of Locomotive Traction Motors Procedia Engineering 165 ( 2016 ) 1437 – 1443 Available online at www sciencedirect com 1877 7058[.]
Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 165 (2016) 1437 – 1443 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development” Determination of energy loss in power voltage inverters for power supply of locomotive traction motors Yurii Kabalyk a,* a Far Eastern State Transport University, Serysheva str 47, Khabarovsk, 680021, Russia Abstract The present work aims to research for power loss in electric power converters of locomotives In locomotives with induction motors is apply autonomous voltage inverter that operates with high frequency switching This produce large power losses, which reduce the overall efficiency of locomotive The exact definition of these power losses allow more accurately determine the energy efficiency of the power inverters © 2016 2016The TheAuthors Authors Published by Elsevier Ltd is an open access article under the CC BY-NC-ND license © Published by Elsevier Ltd This (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground Peer-review under scientific committee of the 15th International scientific conference “Underground Urbanisation as a Urbanisation as aresponsibility PrerequisiteoffortheSustainable Development Prerequisite for Sustainable Development Keywords: autonomous voltage inverter; DC-AC converter; traction drive; energy loss; power dissipation; energy efficiency; IGBT-transistor Introduction At present, the most efficient locomotive electric traction drive is the drive equipped with induction motor and frequency converter Such converters are based on high-power semiconductor switches Energy loss on semiconductor switches is substantial which significantly decreases performance of converters Energy loss determination accuracy is a necessary condition for detailed study of working processes in power converters * Corresponding author Tel.: +7-4212-407-076 E-mail address: kabalyk@list.ru 1877-7058 © 2016 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development doi:10.1016/j.proeng.2016.11.876 1438 Yurii Kabalyk / Procedia Engineering 165 (2016) 1437 – 1443 Context Autonomous voltage inverter (hereinafter inverter) is used in locomotives as power converter feeding induction motor There range of existing inverter circuits is diverse [1, 2, 3] The most widely spread are inverters with IGBTtransistors as key elements As a rule the circuit design includes parallel connection of legs of the same kind and the number of this legs equals the number of engine phases Figure shows legs of the same kind used in different variants of inverter circuits In these modules input for different levels of DC voltage is marked as Ud and output AC voltage is marked as UAC Fig Legs in different types of inverter circuit: a – two-level inverter; b, e – three-level inverter; c, d – four-level inverter A two-level type is the most widely spread inverter circuit (Fig.1, a) [4, 5] Inverters of this type have an advantage of simple structure and little number of semiconductor switches, but at the same time they have two main flaws: high voltage in the closed transistor and immense harmonic distortions of output voltage which increase energy losses in an induction motor [6, 7, 8] Modern power semiconductor switches are designed to handle high Yurii Kabalyk / Procedia Engineering 165 (2016) 1437 – 1443 1439 voltage thus simplifying the production of two-level inverters, yet the problem of high harmonics in an output voltage can be eliminated either by an increase of switching frequency or by a change of the structure of inverter Output voltage harmonic distortion can be reduced by additional levels of output voltage Such inverters are called multi-level inverters Three-level (Fig.1, b, e) [9, 10] and four-level inverters (Fig.1, c, d) [11, 12, 13] are the types of multi-level inverters Three-level and four-level inverters, shown in Fig 1, b, c, create AC with a low level of harmonic distortion, electric current of each phase, however, flows simultaneously through three semiconductor elements This leads to increase in total power losses of an inverter Wasteful power losses can be reduced by decreasing the number of switches in the circuit of output current [13, 14] This principle is represented by inverters composed of legs, as shown in Fig 1, d, e Research Inverter’s loss power is mainly determined by power losses in IGBT-transistors These losses are made up of dynamic losses (turn-on and turn-off) and static losses (on-state and off-state) It is considered that static losses are significantly less than dynamic, so they are not always taken into consideration In this case the amount of energy loss Eloss, emitted in one transistor per second, to be calculated according to the following equation f sw Eon f sw Eoff , Eloss (1) fsw – transistor switching frequency, Hz; Eon and Eoff – energy loss of switching transistor on and off respectively, J This concept may be fair for low-power transistors with small currents, but not applicable to high-power transistors with high currents and collector-emitter voltage of a few volts As a result, loss power of an on-state transistor reaches thousands of watts That is the reason, why transistor energy loss – the result of a load current flowing through a transistor – must also be taken into consideration when estimating inverter energy loss Let us consider the functioning of an IGBT-transistor Power dissipations ploss of transistor is calculated through multiplying its collector-emitter voltage uCE by its collector current iC Ploss=uCE·iC (2) and the amount of wasted energy is determined by its time integral of running time t from power dissipations t E ³ t plossdt ³u CEiС dt (3) In order to examine the origins of inverter’s energy loss Eloss in details, the electromagnetic processes during opening and closing of the semiconductor switches must be studied in details To this, we used Prof Dr Burkhard Bock’s oscilloscope records of FZ1200R33KF1 IGBT-transistor’s current and voltage levels at the ON and OFF moments [15] These records helped to determine loss power first in a separate transistor, and then in an inverter in whole Figure 2, а shows the oscilloscope records of collector-emitter voltage uCE and collector current iC at the moment of turn-on the FZ1200R33KF1 transistor on under feeding voltage Ud=2200 V and load current Iload=1200 А [15] Using these oscilloscope records and equation (2), we calculated power dissipations ploss in transistor Power dissipations curve is shown on the Figure 2, b Maximum power dissipations at the ON moment (Fig 2, b) equaled ploss=3.5 Megawatts (MW) Due to extremely fast process of switching on, average loss power does not exceed the limit values and is successfully absorbed by cooler elements Using equation (3) we defined total loss power for a time of transistor turning-on ton=5.1 μs, which equals Eon=3.4 J When a transistor is in the off-state, collector-emitter cut-off current IGES=12 mА flows through it As a result, with source voltage Ud=2200 V, loss power equals Рloss≈26 W When a transistor is in the on-state, collector-emitter 1440 Yurii Kabalyk / Procedia Engineering 165 (2016) 1437 – 1443 saturation voltage is VCEsat=3.4 V As a result, with a load current Iload=1200 А, loss power is approximately Рloss≈4.1 kW This value of loss power is significantly lower than maximum power dissipations during turning-on, though the process of turning-on lasts significantly shorter than transistor’s on-state That is why dynamic losses and static losses of transistor are commensurable Fig Oscilloscope records of FZ1200R33KF1 IGBT-transistor turning-on (a) and instantaneous power dissipation (b) Fig 3, а shows the oscilloscope records of collector-emitter voltage uCE and collector current iC at the moment of turning-off the FZ1200R33KF1 transistor with feeding voltage Ud=2200 V and load current Iload=1200 А [15] Just like in the case of oscilloscope records of engaging, these turn-off records were used to calculate, according to equation (2), power dissipations emitted in a transistor Power dissipations curve is shown in Figure 3, b Total power emitted for a time of transistor turning-off toff=6.7 μs equaled Eoff=2 J, that is less than during turning-on Eon Maximum power dissipations at the turn-off moment (Fig 2, b) equal ploss =2.8 MW Knowing transistor’s switching frequency fsw we can calculate total loss power Eloss emitted in a transistor for a particular time frame Т, sec, using the following equation Toff Ton Đ Ã ă T ă f s Eon f s Eoff uCEsatiload dt u d iGES dt | ă 0 © ¹ | Т f s Eon f s Eoff VCEsat I load Ton Vd I GES Toff , ³ Eloss ³ (4) T – time of transistor’s operating, sec; Ton and Toff – total time of on-state and off-state of a transistor per second, respectively Yurii Kabalyk / Procedia Engineering 165 (2016) 1437 – 1443 1441 Fig Oscilloscope records of FZ1200R33KF1 IGBT-transistor turning-on (a), and instantaneous power dissipation (b) Results To visualize a loss power behavior in an inverter under switching frequency change, let us examine functioning of a two-level voltage inverter with pulse-width modulation Table shows the data of calculating the operation of one FZ1200R33KF1 IGBT-transistor inside two-level autonomous voltage inverter with pulse-width modulation under feeding voltage Ud=2200 V and load current Iload=1200 А Table data were used for a graph (Fig 4) of loss power in one FZ1200R33KF1 IGBT-transistor per one second of its operated As can be seen in Figure 4, loss power in IGBT-transistor increases with the growth of its switching frequency There is also significant exceeding in total loss power in calculations according to equation (4), if compared calculations according to equation (1) That can be explained by substantial energy dissipation on open transistor With a transistor switching frequency fsw=50 Hz open transistor energy losses are approximately the same as switching energy losses When switching frequency fsw increases, the amount of switching energy losses grows up, and yet the open state energy losses also contribute considerably to the total energy loss 1442 Yurii Kabalyk / Procedia Engineering 165 (2016) 1437 – 1443 Table Data of calculating the operation of one IGBT-transistor inside two-level autonomous voltage inverter with pulse-width modulation fsw, Hz 50 100 150 200 300 Amplitude modulation index m=0.5; running time T=1 s Ton, s 0.209 0.192 0.181 0.173 0.174 Toff, s 0.790 0.807 0.817 0.825 0.822 Eloss, J, equation (1) 270 540 810 1080 1620 Eloss, J, equation (4) 1145.2 1343.9 1571.0 1806.2 2353.5 1.14 1.34 1.57 1.8 2.35 Ploss=Eloss/T, kW (Eloss according to eq (4)) Amplitude modulation index m=0.25; running time T=1 s Ton, s 0.119 0.098 0.088 0.088 0.084 Toff, s 0.880 0.901 0.910 0.910 0.912 Eloss, J, equation (1) 270 540 810 1080 1620 Eloss, J, equation (4) 780.4 962.9 1194.0 1461.6 1988.7 0.78 0.96 1.19 1.46 1.99 Ploss=Eloss/T, kW (Eloss according to eq (4)) Fig graph of loss power in one FZ1200R33KF1 IGBT-transistor per one second of its running Two-level inverter with legs, depicted on the Fig 1, а, contains IGBT-transistors Therefore, with transistor switching frequency fsw=300 Hz, load current Iload=1200 F and source voltage Ud=2200 V, power dissipations in an inverter will be as follows: with amplitude modulation index m=0.5 – Ploss=14.1 kW; with amplitude modulation index m=0.25 – Ploss=11.94 kW Under the same conditions, with only dynamic losses of transistor switching taken into consideration (and the static losses ignored), power dissipations in an inverter will be Ploss=9.72 kW with any amplitude modulation index Static losses, therefore, are significant part of inverter power losses: from 15% to 30% of a whole loss power Yurii Kabalyk / Procedia Engineering 165 (2016) 1437 – 1443 Conclusion To determine power loss in autonomous power voltage inverters with IGBT-transistors one must consider not only switching (dynamic) losses but also on- and off- states of transistor (static losses) It will allow for more precise estimation of energy efficiency of power inverters for power supply of traction inductive motors References [1] J.H Hahn, “Modified Sine-Wave Inverter Enhanced”, Power Electronics Technology 2006, pp.20-22 [2] B Xiao, F Filho, L M Tolbert, “Single-Phase Cascaded H-Bridge Multilevel Inverter with Nonactive Power Compensation for GridConnected Photovoltaic Generators”, Energy Conversion Congress and Exposition (ECCE), 2011 [3] V.A Kuchumov, A.S Knyazheva, Analysis of Electromagnetic Processes in AC Electric Locomotive with Autonomous Power Inverters and AC Traction Electric Drives, Vestnik VNIIZhT (2008) 31-35 [4] B Bhutia, Dr S.M Ali, Narayan Tiadi, Design of Three-Phase PWM Voltage Source Inverter for Photovoltaic Application, International Journal of Innovative Research in Electrical, Electronics, Instrumentation and Control Engineering 2(4) (2014) 1364-1367 [5] A Blok, V Zavgorodniy, O Ariskin, G Shestopyorov, Design of a Three-Phase Bridge Inverter for Power Supply of Traction Asynchronous Electric Drives for AC Electric Locomotives, Silovaya Elektronika (2005) 30-31 [6] A.O Chugulyov, Estimating the Effect of Feeding Voltage’s High Harmonics with Pulse-width Modulation on Power Loss in an Asynchronous Motor, Omskii Nauchny Vestnik 1(64) (2008) 72-75 [7] L Aarniovuori, Induction Motor Drive Energy Efficiency – Simulation and Analysis, Thesis for the degree of Doctor of Science (Technology) – Lappeenranta University of Technology, Lappeenranta, 2010 [8] Yu.B Kazakov, A.A Shumin, V.A Andreyev, Dependence of Power Losses in Asynchronous Motors on Parameters of Pulse-width Control of Voltage, Vestnik IGEU (2007) 1-4 [9] V Filatov, Two-level and Three-level Inverters on IGBT, Silovaya Elektronika (2012) 38-41 [10] P V Brahmam, D Bharath, M Dubey, Pureti Veera Brahmam, Daravath Bharath, Manisha Dubey, International Journal of ChemTech Research 5(5) (2013) 2449-2455 [11] N Donskoi, A Ivanov, V Matison, I Ushakov, Multi-level Autonomous Inverters for Electric Drives and Power Engineering, Silovaya Elektronika (2008) 43-46 [12] J Rodriguez, J.-S Lai, F.Z Peng, Multilevel Inverters: a Survey of Topologies, Controls and Applications, IEEE Transactions on Industrial Electronics 4(49) (2002) 724-738 [13] Yu Kabalyk, Avtonomny invertor napryazheniya [Autonomous Voltage Inverter] The Russian Federation Patent 2549206, applied for on March 12, 2014, issued on April 20, 2015, Patent owner – Far Eastern State Transport University [14] Yu.Kabalyk Povysheniye energoeffektivnosti 3-faznogo avtonomnogo invertora napryazheniya [Energy Efficiency Increase of a ThreePhase Autonomous Power Inverter], ELEKTRO Elektrotekhnika, elektroenergetika, elektrotekhnicheskaya promyshlennost’ (2015) 32-35 [15] B Bock, Switching IGBTs in Parallel Connection or with Enlarged Commutation Inductance, Thesis Submitted to the Faculty of Electricaland Computer Engineering of the Ruhr-University, Bochum In fulfilment of the requirements for the degree Doktor-Ingenieur, Germany, Bochum, 2005 1443 ... switching (dynamic) losses but also on- and off- states of transistor (static losses) It will allow for more precise estimation of energy efficiency of power inverters for power supply of traction. .. energy is determined by its time integral of running time t from power dissipations t E ³ t plossdt ³u CEiС dt (3) In order to examine the origins of inverter’s energy loss Eloss in details, the... Procedia Engineering 165 (2016) 1437 – 1443 Context Autonomous voltage inverter (hereinafter inverter) is used in locomotives as power converter feeding induction motor There range of existing inverter