A wide-range adjustable speed control method for multi-motor drive systems

This paper proposes a new control method for a multi-motor drive system to increase its output torque capability and extend its operating speed range. When the drive system is operated below rated speed, the motors are parallel operated to increase total output torque. By suitably distributing the stator currents based on an optimal efficiency algorithm, the output torque can be effectively increased. On the other hand, when the drive system is operated beyond rated speed, one motor is operated at a standstill and its stator inductances are used as three-phase inductances of an boost converter; moreover, an interleave control algorithm is used for the boost converter to reduce the input current ripples. The other motor is used as a driving motor. By using this method, an extended speed, which can reach twice the rated speed range with a near constant torque, is obtained. No field weakening is required. This paper proposes a new control method for a multi-motor drive system, which can be applied to electric vehicle drive systems.