2. Types of hybrid drives

2.1. Serial hybrid drive

1 – ICE

2 – fuel tank

3 – electric machine (generator)

4 – electric machine (motor)

5 – power inverter

6 – battery

  • Serial connection of acceleration force sources.
  • The series arrangement consists of an internal combustion engine (ICE) and a pair of electrical machines.
  • The internal combustion engine (ICE) is not mechanically coupled to the axle.
  • The electric machine (3) works as a generator.
  • All power flow to the axle is realized through an electric machine (4).
  • The electric machine (4) is working
    • as a motor in drive mode, energy is taken from the traction battery and ICE,
    • as a generator during braking, the traction battery is charged,
    • as ICE starter.

    Drive mode
    • P_k = M_4 ω_4 = P_6 + P_1 = P_6 + P_3 = U_6 I_6 + M_1 ω_1 = U_6 I_6 + M_3 ω_3
    • P_1 = 0, P_k = M_4 ω_4 = P_6 = U_6 I_6
    • P_6 = 0, P_k = M_4 ω_4 = P_1 = P_3 = M_1 ω_1 = M_3 ω_3
    Brake mode
    • P_1 = 0, -P_k = -M_4 ω_4 = -P_6 = U_6(-I_6)
    • P_6 = 0, -P_k = -M_4 ω_4 = -P_1 = -P_3 = -M_1 ω_1 = -M_3 ω_3
    • -P_k = -M_4 ω_4 = -P_6 + -P_1 = -P_6 + -P_3 = U_6 (-I_6) -M_1 ω_1 = U_6 (-I_6) -M_3 ω_3

    • ICE can be operated at the optimal efficiency point:
      • P_1 = M_1 ω_1 = konst. = argmax⁡[(η_1 = f(M_1, ω_1)].
    • ICE is not mechanically coupled to the axle → many installation options in the car.
    • Low power transfer efficiency from ICE to wheel (large number of conversions).

    Example
    • Maximum efficiency η_{max} = \max(η_1 η_3 η_5 η_4 ) = 0,35\cdot0,96\cdot0,98\cdot0,96 = 0,32


    Applications
    • Buses in city traffic, ie. stop & go driving style on a known route.
    • Range extenders - practically BEV, emergency driving after discharging the battery.




    Bosch Automotive Electrics and Automotive Electronics: System Components, Networking and Hybrid Drive, Robert Bosch GmbH, Springer 2007, ISBN 978-3-658-01783-5