In order to reduce deviation of correction amount when calculating a magnetic pole position correction amount of a permanent magnet type rotating electrical machine, and perform magnetic pole position correction with high accuracy, in state where the permanent magnet type rotating electrical machine is rotated, a d-axis current command value and a q-axis current command value in dg vector control are kept substantially zero, an actual d-axis voltage and an actual q-axis voltage are calculated from a midpoint potential detected from a midpoint potential detection unit, a magnetic pole position correction amount is calculated based on a predetermined arithmetic expression from the actual d-axis voltage and the actual q-axis voltage, and magnetic pole position origin correction is performed based on the magnetic pole position correction amount.

In order to reduce deviation of correction amount when calculating a magnetic pole position correction amount of a permanent magnet type rotating electrical machine, and perform magnetic pole position correction with high accuracy, in state where the permanent magnet type rotating electrical machine is rotated, a d-axis current command value and a q-axis current command value in dg vector control are kept substantially zero, an actual d-axis voltage and an actual q-axis voltage are calculated from a midpoint potential detected from a midpoint potential detection unit, a magnetic pole position correction amount is calculated based on a predetermined arithmetic expression from the actual d-axis voltage and the actual q-axis voltage, and magnetic pole position origin correction is performed based on the magnetic pole position correction amount.

A feedback control switching unit of an inverter control unit selects, based on a magnitude relationship between a predetermined switching determination amount and at least one switching threshold, at least one of feedback control units to thereby execute switching among feedback control modes, such as a current feedback control mode and a torque feedback control mode, of the respective feedback control units for driving of the AC motor. A switching command generating unit generates a switching command for an inverter based on a manipulated variable calculated by the selected feedback control unit. When a torque response request determining unit determines that a required torque responsiveness is high, the feedback control switching unit reduces the number of executions of switching among the feedback control modes.

A feedback control switching unit of an inverter control unit selects, based on a magnitude relationship between a predetermined switching determination amount and at least one switching threshold, at least one of feedback control units to thereby execute switching among feedback control modes, such as a current feedback control mode and a torque feedback control mode, of the respective feedback control units for driving of the AC motor. A switching command generating unit generates a switching command for an inverter based on a manipulated variable calculated by the selected feedback control unit. When a torque response request determining unit determines that a required torque responsiveness is high, the feedback control switching unit reduces the number of executions of switching among the feedback control modes.

A motor system provided with one motor and two inverters includes a first inverter control unit which changes a frequency of a first carrier wave (first carrier frequency) used for producing a switching signal fora first inverter according to an operating point of the motor; and a second inverter control unit which changes a frequency of a second carrier wave (second carrier frequency) used for producing a switching signal for a second inverter according to an operating point of the motor. The first carrier frequency has a changing characteristic depending on the first inverter control unit and the second carrier frequency has a changing characteristic depending on the second inverter control unit, and the changing characteristics are different from each other to make the first carrier frequency and the second carrier frequency differ from each other at an identical operating point.

A motor system provided with one motor and two inverters includes a first inverter control unit which changes a frequency of a first carrier wave (first carrier frequency) used for producing a switching signal fora first inverter according to an operating point of the motor; and a second inverter control unit which changes a frequency of a second carrier wave (second carrier frequency) used for producing a switching signal for a second inverter according to an operating point of the motor. The first carrier frequency has a changing characteristic depending on the first inverter control unit and the second carrier frequency has a changing characteristic depending on the second inverter control unit, and the changing characteristics are different from each other to make the first carrier frequency and the second carrier frequency differ from each other at an identical operating point.

In order to reduce deviation of correction amount when calculating a magnetic pole position correction amount of a permanent magnet type rotating electrical machine, and perform magnetic pole position correction with high accuracy, in state where the permanent magnet type rotating electrical machine is rotated, a d-axis current command value and a q-axis current command value in dg vector control are kept substantially zero, an actual d-axis voltage and an actual q-axis voltage are calculated from a midpoint potential detected from a midpoint potential detection unit, a magnetic pole position correction amount is calculated based on a predetermined arithmetic expression from the actual d-axis voltage and the actual q-axis voltage, and magnetic pole position origin correction is performed based on the magnetic pole position correction amount.

In order to reduce deviation of correction amount when calculating a magnetic pole position correction amount of a permanent magnet type rotating electrical machine, and perform magnetic pole position correction with high accuracy, in state where the permanent magnet type rotating electrical machine is rotated, a d-axis current command value and a q-axis current command value in dg vector control are kept substantially zero, an actual d-axis voltage and an actual q-axis voltage are calculated from a midpoint potential detected from a midpoint potential detection unit, a magnetic pole position correction amount is calculated based on a predetermined arithmetic expression from the actual d-axis voltage and the actual q-axis voltage, and magnetic pole position origin correction is performed based on the magnetic pole position correction amount.

Methods and systems for load alignment assistance are provided. An alignment current may be provided with a partial power converter through an n-phase supply line to a synchronous alternating current (AC) motor during a startup of a synchronous AC grid. The synchronous AC motor may receive polyphase AC power through the n-phase supply line from the synchronous AC grid during the startup. The partial power converter may be powered by a power source isolated from the synchronous AC grid. The alignment current may be controlled such that the alignment current causes a rotor of the synchronous AC motor to align with a rotor of a generator that powers the synchronous AC grid.

Methods and systems for load alignment assistance are provided. An alignment current may be provided with a partial power converter through an n-phase supply line to a synchronous alternating current (AC) motor during a startup of a synchronous AC grid. The synchronous AC motor may receive polyphase AC power through the n-phase supply line from the synchronous AC grid during the startup. The partial power converter may be powered by a power source isolated from the synchronous AC grid. The alignment current may be controlled such that the alignment current causes a rotor of the synchronous AC motor to align with a rotor of a generator that powers the synchronous AC grid.