A motor drive device includes a power conversion circuit that drives an AC motor and a controller that controls the power conversion circuit. The controller includes a command current calculation unit generating a command current according to command torque for the AC motor and a current control unit that performs feedback control for adjusting a current applied to the AC motor to the command current. The controller also includes a control gain setting unit that calculates a control gain used for the feedback control based on the command torque and sets the calculated control gain in the current control unit. The control gain setting unit performs control such that a time from a decrease of an absolute value of the command torque to switching of the control gain is longer than a time from an increase of the absolute value of the command torque to switching of the control gain.

An apparatus for a drive for driving an externally excited synchronous motor. The apparatus includes means for performing the following. The apparatus causes the drive to operate in a primary operating mode for achieving unity power factor. The apparatus monitors stator flux linkage load angle, stator flux linkage and torque references. In response to the stator flux linkage load angle reference, in a steady state, reaching or exceeding a pre-defined maximum allowed stator flux linkage load angle for steady state operation, the apparatus causes the drive to operate in a stator flux assistance operating mode. In the stator flux assistance operating mode, an increased stator flux linkage for allowing operation with the pre-defined maximum allowed stator flux linkage load angle with unity or maximized sub-unity power factor is used as the stator flux linkage reference.

A method and system for sensorless determination of the orientation of the rotor of an ironless PMSM motor from a known rotor angle is described. The method and system include: specifying a rotor system according to the rotor angle; applying voltage pulses to the phases of the motor in the torque-forming direction of the rotor system; measuring the current in the phases of the motor; determining the expected back EMF along the flux-forming axis, based on the measured current; forming an integral of the expected back EMF by time integration of the expected back EMF along the flux-forming axis and/or a filter-based accumulation function; and determining the orientation of the rotor from the algebraic sign of the integral of the expected back EMF and/or the accumulation function.

A method and system for sensorless determination of the orientation of the rotor of an ironless PMSM motor from a known rotor angle is described. The method and system include: specifying a rotor system according to the rotor angle; applying voltage pulses to the phases of the motor in the torque-forming direction of the rotor system; measuring the current in the phases of the motor; determining the expected back EMF along the flux-forming axis, based on the measured current; forming an integral of the expected back EMF by time integration of the expected back EMF along the flux-forming axis and/or a filter-based accumulation function; and determining the orientation of the rotor from the algebraic sign of the integral of the expected back EMF and/or the accumulation function.

Reduced computation time for model predictive control (MPC) of a five level dual T-type drive considering the DC link capacitor balancing, the common-mode voltage (CMV) along with torque control of an open-ends induction motor based on determining a reduced set of switching states for the MPC. The reduced set of switching states are determined by considering either CMV reduction (CMVR) or CMV elimination (CMVE). Cost function minimization generates a voltage vector, which is used to produce gating signals for the converter switches. The reduced switching state MPC significantly reduces computation time and improves MPC performance.

Reduced computation time for model predictive control (MPC) of a five level dual T-type drive considering the DC link capacitor balancing, the common-mode voltage (CMV) along with torque control of an open-ends induction motor based on determining a reduced set of switching states for the MPC. The reduced set of switching states are determined by considering either CMV reduction (CMVR) or CMV elimination (CMVE). Cost function minimization generates a voltage vector, which is used to produce gating signals for the converter switches. The reduced switching state MPC significantly reduces computation time and improves MPC performance.

A control device and a control method for an induction motor. The control device comprises: a magnetizing current adjusting unit used for calculating a magnetizing voltage instruction; a torque current adjusting unit used for calculating a torque voltage instruction; a flux linkage instruction angle generating unit calculating a flux linkage instruction angle according to a lower limit ω.sub.1th of a preset stator frequency, a stator frequency ω.sub.1, and a flux linkage estimation angle; and a motor stator voltage instruction calculating unit calculating, according to the magnetizing voltage instruction, the torque voltage instruction, and the flux linkage instruction angle, a stator voltage instruction for controlling a stator of the motor. The control system can be run outside an unstable area, and the stability of control by the control device is improved.

A control device and a control method for an induction motor. The control device comprises: a magnetizing current adjusting unit used for calculating a magnetizing voltage instruction; a torque current adjusting unit used for calculating a torque voltage instruction; a flux linkage instruction angle generating unit calculating a flux linkage instruction angle according to a lower limit ω.sub.1th of a preset stator frequency, a stator frequency ω.sub.1, and a flux linkage estimation angle; and a motor stator voltage instruction calculating unit calculating, according to the magnetizing voltage instruction, the torque voltage instruction, and the flux linkage instruction angle, a stator voltage instruction for controlling a stator of the motor. The control system can be run outside an unstable area, and the stability of control by the control device is improved.

In the fault-tolerant direct thrust-force control (FT-DTC) method, the generalized Clarke transform matrix and its inverse matrix are derived according to the fault-tolerant phase currents. The stator fluxes in α-β plane are deduced based on these. Based on the requirement of circular stator flux trajectory, virtual stator fluxes are defined, and then compensatory voltages in the α-β plane are obtained. Actual stator voltages in the α-β plane are calculated by modulation function of voltage source inverter. Combining with the compensatory voltages, the actual stator voltages and the stator currents, the virtual stator fluxes and the thrust-force are estimated by the flux and thrust-force observers. The thrust-force reference, the stator flux amplitude reference, the observed thrust-force and virtual stator flux are applied to predict virtual stator voltage references. The actual stator voltage references is calculated according to virtual voltage references and compensatory voltages, and are fed to voltage source inverter.

In the fault-tolerant direct thrust-force control (FT-DTC) method, the generalized Clarke transform matrix and its inverse matrix are derived according to the fault-tolerant phase currents. The stator fluxes in α-β plane are deduced based on these. Based on the requirement of circular stator flux trajectory, virtual stator fluxes are defined, and then compensatory voltages in the α-β plane are obtained. Actual stator voltages in the α-β plane are calculated by modulation function of voltage source inverter. Combining with the compensatory voltages, the actual stator voltages and the stator currents, the virtual stator fluxes and the thrust-force are estimated by the flux and thrust-force observers. The thrust-force reference, the stator flux amplitude reference, the observed thrust-force and virtual stator flux are applied to predict virtual stator voltage references. The actual stator voltage references is calculated according to virtual voltage references and compensatory voltages, and are fed to voltage source inverter.