Hybrid Drive Systems for Vehicles

Transcription

1 Hybrid Drive Systems for Vehicles Auxilliary systems

2 Auxilliary systems? Fundamental support functions Power Steering Power Brakes Air pressure (heavy vehicles) Lighting Ventilation Suspension 12/24 V system Comfort function Air Conditioning Power windows, seats,... Entertainment systems

3 Auxilliary systems cannot be disregarded Energy consumption and peak power significant Sometimes in parity with the tractive energy Two distinct goals: 1. Minimize energy consumption 2. Limit peak power

4 Means.. Technology selection Mechanical to electric. Pneumatic to electric Hydraulic open loop to closed loop Hydraulic to electric... to increase efficiency Control and scheduling Load shaving, e.g.: reduce compressor speed at high load, or Intelligent use of braking energy, e.g. regenerate energy to aux systems like compressor when the bus is braking.

5 Test vehicle: Industrial Electrical Engineering and Automation Lund University, Sweden

6 Drive train Auxiliary system

7 Energy balance in the bus (in average powers) Hydrogen Power 58 kw 100 % Fuel Cell System Braunschweig Driving cycle FC Losses 32 kw 55 % Electrical power 24 kw 41 % Energy recovery 11 kw FC Auxiliaries 2.5 kw HV Dist. System & Battery No AC! Bus Auxilaries 4.0 kw 7.0 % 29 kw 50 % Battery losses 1.6 kw Propulsion system DC/AC & Motor Losses 4.3 kw Traction Power 24 kw Road Friction 12 kw Regeneration loss 1.9 kw

8 Auxiliary system energy Subsystem energy usage, 4 kw consumption 24 V System, 1170 W Losses in battery 24% Lights 25% Cooling Fans 31% 24V DC/DC 29% Control system 51% Compressor 21% Water pump 5% Servo pump 14% Air (compressor) system, 830 W Suspension System 32% Door Opening 35% Brake 15% Hand Brake 18%

9 Air pressure driven loads Brakes Suspension Door opening 1 Brakes 2 Electronic control 1 system 3 Valves 4 Air dryer 5 Compressor

10 Brake system Pneumatic (heavy vehicle) Slow response time Easy connection of e.g. Trailer Retarder Exhaust brake, or Hydraulic Hydraulic (light vehicle) Development towards electric Better control In heavy vehicles in hybrid vehicles with regenerative braking and friction brake fill in. Cheaper? Energy supply difficult. Local el energy generation?

11 Steering Rack and pinion manual (traditional) Hydraulic assist (modern) Need hydraulic pump Losses Electric assist 80 % less losses than hydraulic

12 Heat AC system Large windows -> increased cooling demand Private car (< 4 kw) Bus (< 30 kw) Compressor inefficient Heat Condenser Refrigerant Circui ExpansionValve Compresor Evaporator

13 New technology selection Pneumatic (air) system, 830 W Pneumatic (air) system, 830 W System Pneum [W] El [W] Suspension 32% Suspension 32% Door Opening 35% Door Opening 35% Doors Suspension Brake 15% Brake 15% Parking Brake 18% Parking Brake 18% Parkering Brake

14 Torque [Nm] Peak shaving Aux. off limit Max engine torque Aux. on limit Speed [rpm]

15 Power [kw] Propulsion [kw] Speed [km/h] Auxiliary [kw] 60 Control Peak Shaving seconds seconds AC DC/DC Propulsion AC+DC/DC+Propulsion Run 240 at 260 full power seconds seconds

16 Power [kw] off - on AC-system on/off condition duty cycle generator Propulsion power Power limits normal operation off-peak power limit on-controller on-regen. power limit offcontroller Reference Actual time

17 Fuel allocation [%] Potential improvements of the auxiliary system Potential improvements Auxiliary system Propulsion system Hybrid bus Conventional bus

18 Electrical Systems 12 V (light vehicles) 50 Ah <-> 600 Wh 24 V (heavy vehicles) 200 Ah <-> 4800 Wh Alternators (Efficiency 50 %) Startor Rotor 80 A <-> 1.1 kw (light vehicles) INCREASING! 300 A <-> 8.4 kw in larger buses DC/DC converter in hybrids (Efficiency 90 %) Collector rings

19 Conventional electric loads Electric generator load in average 600 W Assume efficiency 50 % Mechanical Generator load 1200 W

20 Drag powers... Remember generator load 1.2 kw!

21 Additional loads... Weight, volume and efficiency benefits in electrical drive of traditionally mechanically driven loads. Many more could be added: Electric compartment heating, GPS Navigation Systems, DVD based Passenger Entertainment Systems, BlueTooth connection for giving brought on Mobile Phones Hands free via the Sound Systems, Detachable Cooling Boxes, Electrically Operated Foldable Cabriolet Roof, Electrically Controlled Suspension and Levelling System, Reversing Distance Sensing System, 230 V/50 Hz outlet for electric power to e.g. electric hand tools or electric grills for tail gate parties

22 To much...? The conventional generator is not able to provide enough power to supply all loads... Higher power is needed! Can we continue with 12 Volt?

23 Ernie I Damn! - Hi mate, my battery is dead... - Do you have any jumper cables?

24 Ernie II - Damn kind of you to help me out! - That is of course a VERY OLD yankee.. - Are you sure that it can make my Yamagucci spin?

25 Ernie III - OK, lets go!

26 Ernie IV - It was like connecting Tjernobyl to the Duracell Rabitt

27 The 12 V story 6 V to begin with 6 V electric generator and starter V not enough higher load and compression 12 V introduced 1955 Still used, up to 1 kw No electric hazard Modest isolation requirements Easy fusing Maximum power?

28 Problems with increased 12 V Cable area becomes large 1 kw needs 8 mm diameter cable 4 kw need 16 mm diameter cable 10 s of kw needs... Connectors becomes expensive Voltage drops must be kept very low

29 So, how much more do we need? 1992 MIT and Mercedes Benz took the initiative to a 42 V system voltage 42?, = 3*14 = charging voltage of a 36 V battery. Problems with 42 V: Still not enough, in particular for hybrid power levels Windings in machines bigger Fusing more expensive Filament lamps last shorter

30 42 may not be the answer Has lost its momentum A higher voltage is needed, most likely more than 100 V Already a fact today in hybrid vehicles A new standard must be expected

31 Multi voltage systems 12 Volt will be needed as service battery N*100 V will be used as traction battery 5 V will be used in control systems 36/42 will be used...? Difficulties: Power bridges are needed Foolproof, e.g. when jumpstarting Safety in accident

32 Power bridges Necessary to transfer energy between the 12 V and the traction battery The 12 V has negative earth in the chassis The traction battery can have either Negative earth in chassis Floating relative to chassis Safety and EMC when line charging Traction Batery

33 A 4 quadrant power bridge Can transfer energy in both directions Provides galvanic isolation Transformer Traction Battery No redundancy for the 12 V system Controlled with Puls Width Modulation (PWM) EMC must be considered

34 Battery blocks individuals A traction battery is a chain of blocks, being chains of cells. Each block is an individual Age, thermal history When charging Weakest block full first. What to do? When discharging Weakest block empty first. What to do? Intelligent system needed to take care of all blocks to maximize charge/discharge.

35 Charge Distribution System 1 Simple bypass to dump load Does not solve the discharge limitation... S O C lim ite r

36 Charge Distr. System 2 Bidirectional power flow between traction battery block and 12 V service battery Allows Robin Hood handling of blocks in the traction battery. DC/DC converter obsolete Increased lifetime of the batteries Traction Battery Transformer

37 Another way to charge distribution... Uni-directional, Galvanically isolated Power bridge 100 W max N*100 V Traction Battery 42 V Service Battery Uni-directional, Galvanically isolated Power bridge 1000 W max CU LAN

38 Studeranderepresentant M & E E: Thea Välemark M: Tiago Marques