367
Hybrid Vehicles
initial pure electric range and hence significantly reduce the requirement for
refueling. The corresponding electric motor and battery ratings are similar
to that of the plug-in hybrid, typically 30−50 kW and 400−500 V.
12.4 Hybrid Vehicle Operations
Due to the variations in HEV configurations, different power control strategies are necessary to regulate the power flow to and from different components. These control strategies aim to satisfy a number of goals for HEVs
(Beretta 2000; Van Mierlo 2000). There are four key goals: maximum fuel
economy, minimum emissions, minimum system costs, and good driving
performance. The design of power control strategies for HEVs involves different considerations. Some key considerations are summarized below:
• Optimal engine operation point: The optimal operation point on the
torque–speed plane of the engine can be based on the maximization
of fuel economy, the minimization of emissions, or even a compromise between fuel economy and emissions.
• Optimal engine operation line: In case the engine needs to deliver different power demands, the corresponding optimal operation points
constitute an optimal operating line.
• Optimal engine operation region: The engine has a preferred operation
region on the torque–speed plane, in which fuel economy and emissions remain optimum.
• Proper power distribution: The distribution of power demand between
the engine and electric motor should be properly split up during
the driving cycle, aiming to ensure that the battery can provide
instantaneous discharge for hill-climbing or acceleration, and allow
instantaneous recharge for regenerative braking.
• Zero-emission policy: In some areas, the HEV needs to be operated as
a ZEV. The changeover between the pure electric mode and hybrid
mode should be controlled manually by the driver or automatically
by the GPS-based controller.
12.4.1 Series Hybrid Operation
In the series hybrid system, the power flow control can be illustrated by
four operating modes shown in Figure 12.4. During launching, normal
driving or accelerating, both the engine (via the generator) and battery
deliver electrical energy to the power converter that then feeds the electric
motor and hence drives the wheels via the transmission. At light load,
Hybrid Vehicles
initial pure electric range and hence significantly reduce the requirement for
refueling. The corresponding electric motor and battery ratings are similar
to that of the plug-in hybrid, typically 30−50 kW and 400−500 V.
12.4 Hybrid Vehicle Operations
Due to the variations in HEV configurations, different power control strategies are necessary to regulate the power flow to and from different components. These control strategies aim to satisfy a number of goals for HEVs
(Beretta 2000; Van Mierlo 2000). There are four key goals: maximum fuel
economy, minimum emissions, minimum system costs, and good driving
performance. The design of power control strategies for HEVs involves different considerations. Some key considerations are summarized below:
• Optimal engine operation point: The optimal operation point on the
torque–speed plane of the engine can be based on the maximization
of fuel economy, the minimization of emissions, or even a compromise between fuel economy and emissions.
• Optimal engine operation line: In case the engine needs to deliver different power demands, the corresponding optimal operation points
constitute an optimal operating line.
• Optimal engine operation region: The engine has a preferred operation
region on the torque–speed plane, in which fuel economy and emissions remain optimum.
• Proper power distribution: The distribution of power demand between
the engine and electric motor should be properly split up during
the driving cycle, aiming to ensure that the battery can provide
instantaneous discharge for hill-climbing or acceleration, and allow
instantaneous recharge for regenerative braking.
• Zero-emission policy: In some areas, the HEV needs to be operated as
a ZEV. The changeover between the pure electric mode and hybrid
mode should be controlled manually by the driver or automatically
by the GPS-based controller.
12.4.1 Series Hybrid Operation
In the series hybrid system, the power flow control can be illustrated by
four operating modes shown in Figure 12.4. During launching, normal
driving or accelerating, both the engine (via the generator) and battery
deliver electrical energy to the power converter that then feeds the electric
motor and hence drives the wheels via the transmission. At light load,