Regen Braking

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PROJECT PRESENTATION PROJECT PRESENTATION ON ON Regenerative Braking in three phase Regenerative Braking in three phase locomotives locomotives By By Ajay Israni Ajay Israni IRSEE(P) 2006 IRSEE(P) 2006

Transcript of Regen Braking

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PROJECT PRESENTATIONPROJECT PRESENTATION

ONON

Regenerative Braking in three phase locomotivesRegenerative Braking in three phase locomotives

ByByAjay IsraniAjay IsraniIRSEE(P) 2006IRSEE(P) 2006

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Brake:Brake:

Application of negative tractive effort Application of negative tractive effort to the train and the purpose is to to the train and the purpose is to reduce the speed of the train or stop reduce the speed of the train or stop the train.the train.

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Types of Braking SystemTypes of Braking System

• Friction basedFriction based- Vaccum Brake- Vaccum Brake- Air Brake- Air Brake

• Electrical based (momentum)Electrical based (momentum)- Dynamic Brake- Dynamic Brake

- Rheostatic - Rheostatic - Regenerative- Regenerative

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Regeneration of Power in 3 Phase Regeneration of Power in 3 Phase Induction MotorInduction Motor

Speed torque characteristics of conventional fixed Speed torque characteristics of conventional fixed frequency fixed voltage squirrel cage induction frequency fixed voltage squirrel cage induction motor is given by motor is given by

T = k (v/f)T = k (v/f)2 2 * slip* slip

Where v = terminal voltageWhere v = terminal voltage and f = supply frequencyand f = supply frequency

Regeneration takes place only when rotor is Regeneration takes place only when rotor is driven mechanically at super synchronous speed driven mechanically at super synchronous speed

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3 Phase Induction motor characteristics3 Phase Induction motor characteristics

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PWM Control of Induction MotorPWM Control of Induction Motor Control System is required to give a variable Control System is required to give a variable

voltage and variable frequency power supply to voltage and variable frequency power supply to the traction motor from a fixed catenary voltage. the traction motor from a fixed catenary voltage. This is achieved by using a voltage source This is achieved by using a voltage source inverter (VSI) which is fed from the 25kV catenary inverter (VSI) which is fed from the 25kV catenary power through a converter and DC link capacitor. power through a converter and DC link capacitor. In a VSI the voltage as well frequency are varied In a VSI the voltage as well frequency are varied on demand. To enable movement in either on demand. To enable movement in either direction and regenerative braking, the power direction and regenerative braking, the power flow must be reversible, this is achieved through flow must be reversible, this is achieved through four quadrant controller.four quadrant controller.

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Regenerative Braking In LocoRegenerative Braking In Loco

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Power Circuit DiagramPower Circuit Diagram

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Traction ConverterTraction Converter

Line ConverterLine Converter DC LinkDC Link Drive ConverterDrive Converter

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Traction Converter contd..Traction Converter contd..

The traction converter allows the train not The traction converter allows the train not only to drive but also to brake electrically. To only to drive but also to brake electrically. To control the tractive or braking effort and hence control the tractive or braking effort and hence the speed of the vehicle, both frequency and the speed of the vehicle, both frequency and amplitude of three phase converter output amplitude of three phase converter output voltage are continuously changed according to voltage are continuously changed according to the demand from the driver’s cab. This allows the demand from the driver’s cab. This allows continuous adjustment of the driving or braking continuous adjustment of the driving or braking torque of the traction motor, which means that torque of the traction motor, which means that the driving speed changes smoothly.the driving speed changes smoothly.

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Line converterLine converter

The line converter maintains the DC link The line converter maintains the DC link voltage at a value dependent on power, direction voltage at a value dependent on power, direction of energy flow and line voltage. Line converter of energy flow and line voltage. Line converter consists of two pulse controlled single phase full consists of two pulse controlled single phase full bridge circuits which are connected in parallel on bridge circuits which are connected in parallel on the DC link side. On the AC side, they are the DC link side. On the AC side, they are connected to the secondary winding terminals of connected to the secondary winding terminals of the main transformersthe main transformers

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Intermediate DC linkIntermediate DC link

It performs two main tasks. Firstly it smoothens the It performs two main tasks. Firstly it smoothens the direct current that flow through. Secondly it also direct current that flow through. Secondly it also performs storage function.performs storage function.

DriveDrive ConverterConverter

The Drive Converter converts the DC from Intermediate DC The Drive Converter converts the DC from Intermediate DC link into three phase current for the drive motor (motoring). link into three phase current for the drive motor (motoring). Conversely it is also able to convert the three phase current Conversely it is also able to convert the three phase current generated by the drive motors into direct current for brakinggenerated by the drive motors into direct current for braking

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For regenerative braking to take place, there are For regenerative braking to take place, there are two essential conditions – two essential conditions –

11 The generated voltage must be greater than the The generated voltage must be greater than the overhead voltageoverhead voltage

22 The overhead system must be receptive to the The overhead system must be receptive to the regenerative powerregenerative power

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In case of three phase induction Motor, no In case of three phase induction Motor, no additional apparatus or equipment are required additional apparatus or equipment are required for regenerative braking, since the induction for regenerative braking, since the induction motor operate as generator when driven at speed motor operate as generator when driven at speed exceeding the synchronous speed, the switchover exceeding the synchronous speed, the switchover from motor action to generator action is from motor action to generator action is automatic on a down grade with the tendency of automatic on a down grade with the tendency of the train to speed up. In VVVF system, the the train to speed up. In VVVF system, the frequency of the motor can be varied to create frequency of the motor can be varied to create the required disparity w.r.t. the supply frequency the required disparity w.r.t. the supply frequency which would permit braking even on level section which would permit braking even on level section and almost upto zero speed.and almost upto zero speed.

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Curve 3 Curve 2 Curve 1 f 3 f2 f 1 P3 P1 T1 Positive torque N2 N1 P2 P4 Negative torque

Torque - Speed characteristics in regeneration.

Regenerative Braking

If at a speed N1, we reduce the

frequency from f1 to f2 , then Sync. Speed reduces, and for the same motor speed N1, operating

point shifts from P1 to P2 on

regenerating portion with negative torque. Thus, regenerative braking is achieved, which is possible right upto near-zero speeds.

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Working of Traction Converter Working of Traction Converter (motoring/regeneration)(motoring/regeneration)

The line converter is a self commutating four quadrant The line converter is a self commutating four quadrant converter consisting of full bridge GTO circuit.converter consisting of full bridge GTO circuit.

The full bridge circuit GTOs are switched at frequency The full bridge circuit GTOs are switched at frequency much greater than the line frequency, the switching much greater than the line frequency, the switching signals for the four pairs of arm are shifted by 90° in signals for the four pairs of arm are shifted by 90° in relation to one another. This ensures that the AC current relation to one another. This ensures that the AC current in the transformer primary winding is almost sinusoidalin the transformer primary winding is almost sinusoidal

The motor converter consists of a pulse controlled three The motor converter consists of a pulse controlled three phase bridge circuit which is connected to the DC link, on phase bridge circuit which is connected to the DC link, on the AC it is connected to three motor stator windings. All the AC it is connected to three motor stator windings. All motors are connected in parallelmotors are connected in parallel

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Working of Traction Converter Working of Traction Converter (motoring/regeneration)(motoring/regeneration)

contd..contd.. In motoring mode (driving mode), the In motoring mode (driving mode), the

fundamental frequency of the motor fundamental frequency of the motor terminal is higher than the frequency terminal is higher than the frequency corresponding to the motor speed corresponding to the motor speed (positive slip) resulting in a positive motor (positive slip) resulting in a positive motor torque.torque.

During braking, the fundamental During braking, the fundamental frequency of the motor terminal voltage frequency of the motor terminal voltage will be lowered below the frequency will be lowered below the frequency corresponding to the motor speed, corresponding to the motor speed, resulting in a negative slip and therefore resulting in a negative slip and therefore producing braking torqueproducing braking torque

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Vector DiagramVector Diagram

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Indian RailwayIndian Railway The population of three phase locomotive on Indian The population of three phase locomotive on Indian

Railway is approx 145 comprising of WAG9, WAP5 Railway is approx 145 comprising of WAG9, WAP5 and WAP7.and WAP7.

The converter unit in these locomotives has the task The converter unit in these locomotives has the task of converting power between the transformer and of converting power between the transformer and the asynchronous motor in such a way that optimum the asynchronous motor in such a way that optimum tractive or braking effort can be generated at any tractive or braking effort can be generated at any speed.speed.

Only three loco sheds has been selected to maintain Only three loco sheds has been selected to maintain these three locomotives on Indian Railway i.e. these three locomotives on Indian Railway i.e. Gomoh, Ajni and GhaziabadGomoh, Ajni and Ghaziabad

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Indian RailwayIndian Railwaycontd..contd..

ELS Gomoh is having holding of WAG-9 60 locos and WAP-7 8 locos. Data regarding ELS Gomoh is having holding of WAG-9 60 locos and WAP-7 8 locos. Data regarding energy consumed and energy regenerated during period of Feb to May ’09 are energy consumed and energy regenerated during period of Feb to May ’09 are

Sr NoSr No Loco NoLoco No Energy Consumed Energy Consumed KWH/dayKWH/day

Energy Regenerated Energy Regenerated KWH/dayKWH/day

% Saving% Saving

11 3140031400 1179511795 13191319 11.211.222 3140231402 91389138 747747 8.28.233 3140331403 33483348 358358 10.610.644 3140431404 1026210262 11251125 111155 3140531405 1065010650 13501350 12.712.766 3140731407 1002610026 12061206 121277 3141131411 1037610376 10821082 10.210.288 3141231412 1359413594 19591959 14.414.499 3141331413 1096810968 13881388 12.512.51010 3141531415 1208912089 17281728 14.314.3

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Sr NoSr No Loco NoLoco No Energy Consumed Energy Consumed KWH/dayKWH/day

Energy Regenerated Energy Regenerated KWH/dayKWH/day

% Saving% Saving

1111 3141631416 1273712737 12571257 9.99.91212 3141731417 1089710897 942942 8.88.81313 3141831418 94239423 10141014 10.810.81414 3141931419 1314613146 14861486 11.311.31515 3142031420 1122911229 12591259 11.211.21616 3142131421 74207420 679679 9.29.21717 3142231422 1389013890 15551555 11.411.41818 3142331423 1288612886 18751875 13.013.01919 3142431424 1363313633 14151415 10.410.42020 3104931049 1535615356 11201120 7.37.32121 3020130201 2004120041 30183018 15.115.12222 3020230202 1583815838 22322232 14.114.12323 3020530205 94909490 16421642 17.317.32424 3020630206 1036710367 18271827 17.617.62525 3022630226 65226522 10211021 15.715.7

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Case Study - DMRCCase Study - DMRC

The modern design of metro rolling stock The modern design of metro rolling stock incorporating three phase induction motor and incorporating three phase induction motor and converter-inverter enables recovery of a major converter-inverter enables recovery of a major portion of consumed electricity by way of using portion of consumed electricity by way of using regenerative brakingregenerative braking

With smaller inter-station distances, metro With smaller inter-station distances, metro operation is essentially of start/stop. Due to operation is essentially of start/stop. Due to frequent acceleration and de-acceleration frequent acceleration and de-acceleration requirement, the energy demand is very high. requirement, the energy demand is very high. Traction accounts for about 60-80% of total energy Traction accounts for about 60-80% of total energy consumption in a metro systemconsumption in a metro system

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Case Study – DMRCCase Study – DMRCcontd..contd..

DMRC rolling stock uses 25kV AC Traction with AC DMRC rolling stock uses 25kV AC Traction with AC propulsion system capable of regeneration on its propulsion system capable of regeneration on its network.network.

Traction motors in DMRC are VVVF controlled Traction motors in DMRC are VVVF controlled 220kW, 1450V 3 phase squirrel cage induction 220kW, 1450V 3 phase squirrel cage induction motors.motors.

A typical rake used by DMRC consists of two units A typical rake used by DMRC consists of two units – each comprising a driving trailer and motor car– each comprising a driving trailer and motor car

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Case Study – DMRCCase Study – DMRCcontd..contd..

Benefits to DMRC –Benefits to DMRC –

11 Saving achieved through regenerative braking is an average Saving achieved through regenerative braking is an average of about 5-20% on different lines.of about 5-20% on different lines.

22 Saving in wheel wear = approx. 1.3 lac/annum/rakeSaving in wheel wear = approx. 1.3 lac/annum/rake

33 Saving in brake block consumption = 53000 Rs/annum/rakeSaving in brake block consumption = 53000 Rs/annum/rake

44 Reduced down time and reduced manpower for maintenance Reduced down time and reduced manpower for maintenance are also significantare also significant

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Advantages of regenerative brakingAdvantages of regenerative braking

1.1. Energy savingEnergy saving2.2. Reduced wear of friction brake Reduced wear of friction brake

equipmentequipment3.3. Less wear of wheelLess wear of wheel

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Limitations of regenerative brakingLimitations of regenerative braking

1.1. The regenerative braking effect rapidly reduces at The regenerative braking effect rapidly reduces at lower speeds. Therefore the friction brake is still lower speeds. Therefore the friction brake is still required in order to bring the vehicle to complete halt.required in order to bring the vehicle to complete halt.

2.2. Due to high average weight of freight trains and the Due to high average weight of freight trains and the fact that only locomotive axles are powered, high fact that only locomotive axles are powered, high share of braking power comes from mechanical brakes share of braking power comes from mechanical brakes and only small share of regenerative brake in and only small share of regenerative brake in locomotive itself, there exists limited potential to raise locomotive itself, there exists limited potential to raise the share of recovered braking energythe share of recovered braking energy

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Limitations of regenerative brakingLimitations of regenerative brakingcond..cond..

3.3. The amount of electrical energy capable of dissipation is The amount of electrical energy capable of dissipation is limited by either the capacity of the supply system to limited by either the capacity of the supply system to absorb this energy or on the state of charge of capacitors absorb this energy or on the state of charge of capacitors or battery. No regenerative braking effect can occurs if or battery. No regenerative braking effect can occurs if another electrical component on the same supply system another electrical component on the same supply system is not currently drawing power and if the battery and is not currently drawing power and if the battery and capacitors are already charged.capacitors are already charged.

4.4. The main disadvantage of regenerative braking as The main disadvantage of regenerative braking as compared to rheostatic braking is the need to closely compared to rheostatic braking is the need to closely match the generated current with the supply match the generated current with the supply characteristicscharacteristics

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ConclusionsConclusions11 Regenerative braking depends upon following Regenerative braking depends upon following

factors:factors:i.i. RouteRouteii.ii. GradientGradientiii.iii. Traffic DensityTraffic Densityiv.iv. Driven AxlesDriven Axles

22 From the data regarding percentage saving in From the data regarding percentage saving in energy, it was found that it varies from 5 – 20%energy, it was found that it varies from 5 – 20%

33 After this study, it can be concluded that by After this study, it can be concluded that by optimum use of regenerative braking optimum use of regenerative braking techniques by loco drivers, there is wide scope techniques by loco drivers, there is wide scope of energy conservationof energy conservation

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ConclusionsConclusionscontd..contd..

4.4. Auditing monthly energy conservation figures of Auditing monthly energy conservation figures of regenerationregeneration

5.5. Award for drivers for conserving maximum Award for drivers for conserving maximum energyenergy

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THANK YOUTHANK YOU