Low cost vector control for permanent-magnet-synchronmotor with only one DC-link current sensor for pumping application

This paper presents a cost-efficient closed loop control of a small permanent magnet machine for pumping application. The special feature of the described solution is only one current probe in the DC-link of the converter. The three phase currents are calculated from this measured current in combination with the state of semiconductors at the time of measurement. Near the sector borders of the space vector modulation the turn-on-time of one semiconductor is too short for measuring the current. A method is developed to compensate these blind areas with the extension of the turn-on-time in half of the PWM-cycles. The measured values are checked by an error detection and exchanged if necessary by an approximation. The position of the rotor is also calculated from the measured current. The paper presents a close loop vector control with less costs than conventional solutions.