A motor driving apparatus and a control method thereof, including a dc-link capacitor configured to store DC power, an inverter including a plurality of switching elements and converting the DC power stored in the dc-link capacitor into AC power to output the power to a motor, a dc-link resistor element disposed between the dc-link capacitor and the inverter; and a controller configured to control an operation of the inverter. The controller calculates a phase difference between a first reference voltage vector among a plurality of reference voltage vectors that are preset on the space vector and a voltage command, generates a switching frequency, determines a first operating point located in a dead band that is a one-phase current undetectable area in one switching cycle and a second operating point located at an outer position including a boundary of the dead band, and controls operation of the plurality of switching elements.

At least one of conditions are satisfied, the conditions are a condition that directions of vectors of N sets of first pulse voltages are different from each other, a condition that directions of vectors of N sets of second pulse voltages are different from each other, and a condition that directions of vectors of N sets of third pulse voltages are different from each other. Further, periods in which voltages having different directions of the vectors among the N sets of the first, the second and the third pulse voltages, are applied at least partially overlap with each other.

At least one of conditions are satisfied, the conditions are a condition that directions of vectors of N sets of first pulse voltages are different from each other, a condition that directions of vectors of N sets of second pulse voltages are different from each other, and a condition that directions of vectors of N sets of third pulse voltages are different from each other. Further, periods in which voltages having different directions of the vectors among the N sets of the first, the second and the third pulse voltages, are applied at least partially overlap with each other.

A motor control device includes a backup electrical angle detection circuit in which an inter-sensor error correction unit calculates an advance gain equal to or more than 1 with respect to input of a steering torque equal to or more than a predetermined torque value, and multiplies an output shaft angular velocity by the advance gain to calculate a post-advance steering angular velocity for correcting the estimated angle error of the direction delayed with respect to the steering direction. Then, an estimated angle calculation unit of the backup electrical angle detection circuit integrates the post-advance steering angular velocity, and, on the basis of a value of the integration, calculates a second motor electrical angle that is an estimated value of a motor electrical angle.

A motor control device includes a backup electrical angle detection circuit in which an inter-sensor error correction unit calculates an advance gain equal to or more than 1 with respect to input of a steering torque equal to or more than a predetermined torque value, and multiplies an output shaft angular velocity by the advance gain to calculate a post-advance steering angular velocity for correcting the estimated angle error of the direction delayed with respect to the steering direction. Then, an estimated angle calculation unit of the backup electrical angle detection circuit integrates the post-advance steering angular velocity, and, on the basis of a value of the integration, calculates a second motor electrical angle that is an estimated value of a motor electrical angle.

In order to achieve the energy efficiency class IE4 defined in the IEC standard 60034, it is necessary to operate permanently excited synchronous machines directly on the mains. Because this is not readily possible, soft start devices may be considered as cost-efficient solutions. A method is described by which the initial rotor angle is defined, which can then be used by an encoderless start process. The fundamental concept is based on energizing in a defined direction. This is achieved in that solely two actuator phases are fired. A current space vector is thereby applied to the machine in a fixed direction and the machine is then aligned thereto. The successful alignment and a blocked motor can thus be recognized based on the profile of the stator current space vector.

In order to achieve the energy efficiency class IE4 defined in the IEC standard 60034, it is necessary to operate permanently excited synchronous machines directly on the mains. Because this is not readily possible, soft start devices may be considered as cost-efficient solutions. A method is described by which the initial rotor angle is defined, which can then be used by an encoderless start process. The fundamental concept is based on energizing in a defined direction. This is achieved in that solely two actuator phases are fired. A current space vector is thereby applied to the machine in a fixed direction and the machine is then aligned thereto. The successful alignment and a blocked motor can thus be recognized based on the profile of the stator current space vector.

A lead angle estimator is provided for estimating a lead angle of a brushless DC motor. The lead angle is the angle between a phase-voltage-vector of a phase-voltage, and a phase-current-vector of a phase-current. The lead angle estimator comprises a sampling unit and a processing unit. The sampling unit is adapted for obtaining phase-samples, which are a measure of the phase-current. The processing unit is adapted for estimating the lead angle by calculating a difference of the phase-samples in a extremum period around a maximum or around at least the phase-voltage, and by normalizing the obtained difference.

A lead angle estimator is provided for estimating a lead angle of a brushless DC motor. The lead angle is the angle between a phase-voltage-vector of a phase-voltage, and a phase-current-vector of a phase-current. The lead angle estimator comprises a sampling unit and a processing unit. The sampling unit is adapted for obtaining phase-samples, which are a measure of the phase-current. The processing unit is adapted for estimating the lead angle by calculating a difference of the phase-samples in a extremum period around a maximum or around at least the phase-voltage, and by normalizing the obtained difference.

A position control device includes a subtracter for subtracting a q-axis current detection value iq from a q-axis current command value iq* to output a q-axis current error iq, an adder for adding a q-axis current compensation amount iqc* for compensating for response timing of q-axis current to the q-axis current error iq, a q-axis current controller for amplifying an output of the adder by I-P control to calculate a q-axis voltage error vq and calculating a q-axis voltage command value vq* on the basis of the q-axis voltage error vq, and a second adder for adding a q-axis voltage feedforward amount vqf corresponding to a time derivative value s.Math.iq of the q-axis current to the q-axis voltage command value vq* to calculate a final q-axis voltage command value.