Electric vehicles drive control in constant power mode

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Electric vehicles drive control in constant power mode

Szumanowski, A. / Bramson, E.

Studies on the performance of the batteries used in the electric vehicles have shown that the total ampere-hours available from the battery, and therefore range of the vehicle, declines if the battery is discharged at a high current rate. This has led to practice (when evaluating the performance of vehicle) of acceleration the vehicle so that constant power is delivered to the road-wheel interface, thus avoiding peak power or current. The difficulty with implementing constant power acceleration is that it requires excessively large acceleration at low velocities. Since each vehicle will have a maximum possible acceleration, a practical approach to constant power acceleration over the entire acceleration until a velocity is reached such the constant power strategy does not call for an acceleration greater then this maximum; from the point on, constant power acceleration is used. In well-known drive systems on electric vehicle, constant power strategy is realized by put into practice the second area of control dc separate machine field weakening control. This system requires to use field-weakening controller and starting point of constant power strategy is depends of nominal speed of motor. This problem has been working out in common with FIAT Research Center (CRF).