Energy Efficiency of Electric Vehicles

Figure 4. Distributed control
2.2. Energy efficiency of the electric motor
The electric motor is the most important part of the electrical drive and the last link in the chain
of energy conversion. DC motors because of their good qualities, control of the rotation speed
and control of the torque, for a long time have been irreplaceable part of the controlled electric
motor drives. In recent years, thanks to the advanced control techniques, asynchronous motors
take place of the DC motors in regulated drives because of its good properties (robustness,
lower maintenance requirements and their appliances in explosive environments, which are
especially important in the case of hybrid vehicles).
Electric motor drive is designed and optimized starting from the known parameters of the
engine. The latest methods for minimizing the power losses in real-time by reducing the level
of flux does not require knowing of all engine parameters, and can be applied to asynchronous
motor drives with scalar and vector control. Optimization of efficiency of asynchronous motors
is based on adaptive adjustment of flux levels in order to determine the optimum operating
point by minimizing losses [2].
Losses due to higher harmonics have to be taken into account when determining the degree
of efficiency of the entire drive. The voltage at the output of the inverter is considered ideal
sinusoidal in the case of control structure developing and the produced effects of higher
harmonics are subsequently taken into account.
Any well-designed controller for optimization should meet the following requirements [2]:
• to determine the optimal operating point for each speed and each load torque of the defined
areas of work;
• the duration of the optimization process is as short as possible;
• to have a minimum number of sensors required;
• to be easy to use;
• that it can be applied to any standard electric motor drive;
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