JP4675766B2 - Electric motor control device - Google Patents

Description

  The present invention relates to a control device for an electric motor.

Conventionally, for example, a sensor that detects a rotation angle of a rotor of an electric motor (that is, a rotation angle of a magnetic pole of a rotor from a predetermined reference rotation position) is omitted, and each phase current supplied to the electric motor from an inverter that controls the electric motor is obtained. A control device that includes a plurality of phase current sensors to detect and estimates a rotation angle based on a detection value of the phase current sensor is known (for example, see Patent Document 1).
JP 2004-343963 A

By the way, in the apparatus according to the above prior art, there is a problem that the apparatus configuration becomes complicated because a plurality of phase current sensors for detecting each phase current energized from the inverter to the motor is provided.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric motor control device capable of appropriately controlling an electric motor while suppressing an increase in complexity of the device configuration.

In order to solve the above-described problems and achieve the object, the motor control device according to the first aspect of the present invention is applied to a multi-phase motor by a pulse width modulation signal (for example, a PWM signal in the embodiment). Of the inverter (for example, the PWM inverter 14A in the embodiment) and current detection means (for example, the DC link current IDC in the embodiment) of the inverter (for example, the DC link current IDC in the embodiment) DC-side current sensor 14b) in the embodiment, and the phase current of the motor based on the DC-side current detected by the current detection means (for example, each phase current Iu, Iv, Iw in the embodiment) Phase current estimation means (for example, the phase current estimation unit 26 in the embodiment) for estimating the position of the rotor of the electric motor based on the amount of change in the phase current estimated by the phase current estimation means ( For example, the position estimation means for estimating the rotation angle θ in the embodiment (for example, the angle estimation section 29 in the embodiment) and the inverter position based on the position of the rotor estimated by the position estimation means. A control device for an electric motor comprising control means (for example, the control unit 15 in the embodiment) for performing switching control for controlling the on / off state of the switching element, wherein the ratio of the on / off state of the switching element Duty command (for example, high-side U-phase on-duty, high-side V-phase on-duty, high-side W-phase on-duty in the embodiment) or output voltage command for each phase (for example, each in the embodiment Phase output voltages * Vu, * Vv, * Vw), and at least the start timing and end of a single carrier period with respect to the DC side current. Modulation means (for example, the offset modulation unit 25 in the embodiment) that generates an on-duty command for each phase at a predetermined timing including an end timing, and the modulation means determines the predetermined timing as the start timing and the The modulation means reduces the on-duty command of the high-side arm of the minimum voltage phase in the plurality of phases to a predetermined value or less, and the potential difference of the line voltage in the plurality of phases exceeds the predetermined value. It is characterized by modulation so as to be retained .

  According to the motor control apparatus having the above configuration, the modulation means executes offset modulation for setting an offset amount with respect to the duty command for the on / off state of the switching element or the output voltage command for each of the plurality of phases, and An on-duty command for each phase is generated at a predetermined timing including at least a start timing and an end timing of a single carrier cycle with respect to the side current. As a result, the detection interval when detecting the amount of change in the phase current can be set to a time interval equivalent to the carrier cycle, and the estimation accuracy when estimating the rotor position can be improved.

According to a second aspect of the present invention, there is provided a motor control apparatus according to the present invention, wherein an inverter (for example, an implementation) for sequentially commutating energization to a plurality of phases of a motor by a pulse width modulation signal (for example, a PWM signal in the embodiment). And a current detection means (for example, a DC side current sensor 14b in the embodiment) for detecting a DC side current of the inverter (for example, a DC link current IDC in the embodiment). , Phase current estimating means for estimating the phase current of the electric motor (for example, each phase current Iu, Iv, Iw in the embodiment) based on the DC side current detected by the current detecting means (for example, implementation The position of the rotor of the motor (for example, the rotation angle θ in the embodiment) is estimated based on the amount of change in the phase current estimated by the phase current estimation unit 26) and the phase current estimation means. Position estimation means (for example, the angle estimation unit 29 in the embodiment) and switching control for controlling the on / off state of the switching element of the inverter based on the position of the rotor estimated by the position estimation means. An electric motor control device comprising a control means to execute (for example, the control unit 15 in the embodiment), which is a duty command (for example, a high ratio in the embodiment) that is a ratio of the on / off state of the switching element. Side U-phase on-duty, high-side V-phase on-duty, high-side W-phase on-duty) or output voltage command for each phase (for example, each phase output voltage * Vu, * Vv, * Vw in the embodiment) Performing offset correction, and at a predetermined timing including at least a start timing and an end timing of a single carrier cycle with respect to the DC side current Modulation means (for example, output voltage offset modulation section 31 in the embodiment) for making the DC side current larger than zero is provided , and the modulation means sets the predetermined timing to a predetermined time from the start timing and the end timing. The modulation means reduces the on-duty command of the high-side arm of the minimum voltage phase in a plurality of phases to a predetermined value or less, and modulates so that the potential difference of the line voltage in the plurality of phases is held to a predetermined value or more. It is characterized in that.

  According to the motor control apparatus having the above-described configuration, the modulation means performs the offset modulation for setting the offset amount with respect to the duty for the on / off state of the switching element or the output voltage for each of the plurality of phases, and the DC side current The DC current is made larger than zero at a predetermined timing including at least a start timing and an end timing of a single carrier period. As a result, the detection interval when detecting the amount of change in the phase current can be set to a time interval equivalent to the carrier cycle, and the estimation accuracy when estimating the rotor position can be improved.

  According to the motor control apparatus having the above configuration, it is possible to further improve the estimation accuracy when estimating the position of the rotor.

  According to the motor control device having the above configuration, the current change detection section can be expanded in a state where the potential difference of the line voltage is held before and after the modulation, and the estimation accuracy when estimating the position of the rotor, This can be further improved.

According to the control device for an electric motor of the present invention described in claim 1 or claim 2, the detection interval for detecting the amount of change in the phase current can be set to a time interval equivalent to the carrier period, and the rotor The estimation accuracy at the time of estimating the position of can be improved.
Furthermore , the estimation accuracy when estimating the position of the rotor can be further improved.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an electric motor control device of the present invention will be described with reference to the accompanying drawings.
An electric motor control device 10 (hereinafter simply referred to as a motor control device 10) according to this embodiment is, for example, a brushless DC motor 12 (hereinafter simply referred to as a motor 12) mounted as a drive source together with an internal combustion engine 11 in a hybrid vehicle. The motor 12 is directly connected in series with the internal combustion engine 11 and has a rotor (not shown) having a permanent magnet used for the field and a rotating magnetic field for rotating the rotor. And a stator (not shown) to be generated.
For example, as shown in FIG. 1, the motor control device 10 includes a power drive unit (PDU) 14 that uses a battery 13 as a DC power source and a control unit 15.

In this motor control device 10, the drive and regenerative operation of a motor 12 having a plurality of phases (for example, U-phase, V-phase, and W-phase) is received by a control command output from the control unit 15 and is a power drive unit (PDU). 14.
For example, as shown in FIG. 2, the PDU 14 has a pulse width modulation (including a bridge circuit 14 a formed by bridge connection using a plurality of transistor switching elements (for example, IGBT: Insulated Gate Bipolar Mode Transistor)) and a smoothing capacitor C ( A PWM inverter 14 </ b> A based on PWM) is connected to a high-voltage battery 13 that exchanges electric energy with the motor 12.

The PWM inverter 14A provided in the PDU 14 includes a high-side, low-side U-phase transistor UH, UL and a high-side, low-side V-phase transistors VH, VL and a high-side, low-side W-phase transistor WH that are paired for each phase. , WL and a smoothing capacitor C, and the transistors UH, VH, WH are connected to the positive terminal of the battery 13 to form a high side arm. UL, VL, and WL are connected to the negative terminal of the battery 13 to form a low-side arm, and the transistors UH, UL and VH, VL, WH, and WL that are paired for each phase are in series with the battery 13. Between the collector and emitter of each transistor UH, UL, VH, VL, WH, WL from the emitter. As a forward direction toward the collector, each diode DUH, DUL, DVH, DVL, DWH, DWL is connected.
Between the bridge circuit 14a and the negative terminal of the battery 13, a direct current sensor 14b that detects a direct current (DC link current) IDC of the PWM inverter 14A is provided.

  The PDU 14 sets a pair for each phase in the PWM inverter 14A based on a gate signal (that is, a PWM (pulse width modulation) signal) that is a switching command input from the control unit 15 when the motor 12 is driven, for example. The DC power supplied from the battery 13 is converted into three-phase AC power by switching the ON / OFF (cut-off) state of each of the transistors UH, UL and VH, VL and WH, WL. By sequentially commutating energization to the stator windings of the motor 12, AC U-phase current Iu, V-phase current Iv, and W-phase current Iw are passed through the stator windings of each phase.

The gate signal input from the control unit 15 to the PDU 14 is, for example, according to the combination of the on / off states of the transistors UH, UL and VH, VL, and WH, WL paired for each phase, for example, Table 1 and FIG. As shown in 3 (a) to (h), a PWM (pulse width modulation) signal corresponding to each of the eight switching states S1 to S8 is obtained.
Then, phase currents Iu, Iv, Iw are intermittently generated on the DC side of the PWM inverter 14A in accordance with the switching states S1 to S8, and the DC side current (DC link current) detected by the DC side current sensor 14b. ) IDC is one of the phase currents Iu, Iv, Iw, or one of the phase currents Iu, Iv, Iw inverted, or zero.

For example, at each time t1 to time t8 in one period (carrier period fc) of a carrier signal composed of a single triangular wave with respect to each phase output voltage * Vu, * Vv, * Vw shown in FIG. In the period from time t1 to time t2 that is the start timing and from time t7 to time t8 that is the end timing of the carrier cycle fc, the high side arm of the bridge circuit 14a is in the on state and the low side arm is in the off state. In the first switching state S1, the DC link current IDC becomes zero.
In the period from time t2 to time t3 and in the period from time t6 to time t7, which is the second switching state S2 in which the high-side U-phase and V-phase transistors UH and VH and the low-side W-phase transistor WL are turned on, The DC link current IDC is a current (−Iw) obtained by inverting the sign of the W-phase current Iw.
In the period from time t3 to time t4 and in the period from time t5 to time t6, which is the seventh switching state S7 in which the high-side U-phase transistor UH and the low-side V-phase and W-phase transistors UL and WL are turned on. The DC link current IDC becomes the U-phase current Iu.
The DC link current IDC is zero during the period from time t4 to time t5, which is the eighth switching state S8 in which the high side arm is off and the low side arm is on.

  The control unit 15 performs current feedback control on the dq coordinates forming the rotation orthogonal coordinates. For example, from the torque command Tr set according to the accelerator opening degree related to the accelerator operation by the driver, the Id command * Id. And Iq command * Iq are calculated, and each phase output voltage * Vu, * Vv, * Vw is calculated based on Id command * Id and Iq command * Iq, and each phase output voltage * Vu, * Vv, * Vw is calculated. In response, a PWM signal as a gate signal is input to the PDU 14, and each phase estimated current Ius, Ivs, Iws that is an estimated value for each phase current Iu, Iv, Iw that is actually supplied from the PDU 14 to the motor 12 is DC. A d-axis current Ids and a q-axis current Iqs obtained by estimating from the link current IDC and converting each phase estimated current Ius, Ivs, Iws on the dq coordinates, and an Id command * Id and Id Each deviation between the command * Iq is controlled to be zero.

The control unit 15 includes, for example, a current command calculation unit 21, a current control unit 22, a dq-3 phase conversion unit 23, a PWM signal generation unit 24, an offset modulation unit 25, a phase current estimation unit 26, A three-phase-dq conversion unit 27, a current difference calculation unit 28, an angle estimation unit 29, and a rotation number calculation unit 30 are provided.
The control unit 15 detects a DC side current (DC link current) IDC detected by the DC side current sensor 14b and a voltage sensor 13a that detects a terminal voltage (power supply voltage) VB of the battery 13. A value and a torque command Tr output from an external control device (not shown) are input.

  The current command calculation unit 21 is required according to, for example, a torque command Tr (for example, a depression amount of an accelerator pedal by a driver, a rotational speed ω of the motor 12, etc.) input from an external control device (not shown). (Command value for generating torque to the motor 12) and the rotational speed ω of the motor 12 input from the rotational speed calculation unit 30, the phase currents Iu, Iv, Iw supplied from the PDU 14 to the motor 12 are A current command for designating is calculated, and this current command is output to the current control unit 22 as an Id command * Id and a * Iq command * Iq on rotating rectangular coordinates.

  The dq coordinates forming the rotation orthogonal coordinates are, for example, a field magnetic flux direction by a permanent magnet of a rotor as a d axis (field axis), and a direction orthogonal to the d axis as a q axis (torque axis). It rotates in synchronization with the rotational phase of the 12 rotors. As a result, the Id command * Id and the Iq command * Iq, which are DC signals, are given as current commands for the AC signal supplied from the PDU 14 to each phase of the motor 12.

The current control unit 22 calculates a deviation ΔId between the Id command * Id and the d-axis current Ids and a deviation ΔIq between the Iq command * Iq and the q-axis current Iqs. For example, a motor input from the rotation speed calculation unit 30 By a PI (proportional integration) operation corresponding to the rotational speed ω, the deviation ΔId is controlled and amplified to calculate the d-axis voltage command value * Vd, and the deviation ΔIq is controlled and amplified to calculate the q-axis voltage command value * Vq.
The dq-3 phase conversion unit 23 uses the rotation angle θ of the rotor input from the angle estimation unit 29 to convert the d-axis voltage command value Vd and the q-axis voltage command value Vq on the dq coordinate in the stationary coordinates. It is converted into a U-phase output voltage * Vu, a V-phase output voltage * Vv and a W-phase output voltage * Vw which are voltage command values on a certain three-phase AC coordinate.

The PWM signal generator 24 switches each of the PWM inverters 14A of the PDU 14 by pulse width modulation based on, for example, sinusoidal output voltages * Vu, * Vv, * Vw and a carrier signal composed of a single triangular wave. A gate signal (that is, a PWM (Pulse Width Modulation) signal) that is a switching command including each pulse for driving the element on / off is generated.
Then, the PWM signal generation unit 24 calculates the duty DUTY of the generated gate signal, that is, the ratio of the on / off state of each pulse for driving each switching element on / off.

The offset modulation unit 25 reduces the on-duty command of the high-side arm of the minimum voltage phase in the plurality of phases to a predetermined value or less, or changes it to substantially zero, and holds the potential difference of the line voltage in the plurality of phases to a predetermined value or more. To be modulated. For example, an on-duty command for each phase is generated at a predetermined timing including at least a start timing and an end timing of a single carrier period with respect to the DC link current IDC, or the DC link current IDC becomes larger than zero. Thus, the offset modulation is performed on the duty which is the ratio of the on / off state of the switching element.
For example, the offset modulation unit 25 first sets the minimum voltage that is the phase corresponding to the minimum value of the phase output voltages * Vu, * Vv, and * Vw with respect to the DC link current IDC in the single carrier period fc. Phase, that is, the on-duty minimum phase (for example, the W-phase shown in FIG. 5) that minimizes the on-duty, which is the ratio at which the transistors UH, VH, and WH of the high-side arm of the PWM inverter 14A are turned on. Then, with respect to this on-duty minimum phase, the on-duty command is generated (or extinguished) at the start time t1 and end time t8 of the carrier cycle fc, so to speak, the on-duty of this on-duty minimum phase. Decrease. In the same manner as this on-duty minimum phase, the on-duty is reduced by the same correction amount for the other phases.

As a result, for example, as shown in FIG. 5, the on-duty command generation timing and extinction timing before the modulation are at time t2 and time t7 with respect to the minimum on-duty phase. The generation timing and disappearance timing of the duty command are the start time t1 and the end time t8 of the carrier cycle fc.
Further, for example, as shown in FIG. 5, the maximum voltage phase corresponding to the maximum value of the phase output voltages * Vu, * Vv, * Vw, that is, the on-duty maximum phase where the on-duty becomes the maximum. Thus, the on-duty command generation timing and extinction timing before modulation are at time t3 and time t6, whereas the on-duty command generation timing and extinction timing after modulation are before the time t3. tm2 and time tm5 after time t6.

The phase current estimation unit 26 is supplied to the stator windings of the respective phases of the motor 12 based on the DC link current IDC detected by the DC side current sensor 14 b and the gate signal input from the PWM signal generation unit 24. Each phase estimation current Ius, Ivs, Iws, which is an estimated value for each phase current Iu, Iv, Iw, is estimated.
That is, the DC link current IDC detected by the DC-side current sensor 14b is obtained by inverting the sign of any one of the phase currents Iu, Iv, Iw, or any one of the phase currents Iu, Iv, Iw. Or, for example, based on Table 1 above, the DC link current IDC detected by the DC-side current sensor 14b in each of the switching states S2 to S7 of the PWM inverter 14A is converted into the estimated currents Ius, Ivs, Iws for each phase. Set as.

  For example, for each of the times t1 to t8 shown in FIG. 4, the DC link current detected by the DC-side current sensor 14b in the period from the time t2 to the time t3 and the period from the time t6 to the time t7 that are in the second switching state S2. IDC is set as a negative W-phase estimated current Iws (that is, -Iws). Further, the DC link current IDC detected by the DC-side current sensor 14b in the period from time t3 to time t4 and in the period from time t5 to time t6, which is the seventh switching state S7, is set as the positive U-phase estimated current Ius. To do.

  The three-phase-dq converter 27 uses the rotation angle θ of the rotor input from the angle estimator 29, and uses the phase estimated currents Ius and Ivs that are currents on the stationary coordinates estimated by the phase current estimator 26. , Iws is converted into a d-axis current Ids and a q-axis current Iqs on a rotation coordinate based on the rotation phase of the motor 12, that is, a dq coordinate.

  For example, as shown in FIG. 6, the current difference calculation unit 28 is configured such that the duty of the gate signal input from the control unit 15 to the PDU 14 (that is, the applied voltages V0, V1, V2, V3 to the motor 12 shown in FIG. 6) is a carrier. Corresponding to the change for each cycle fc, for each phase estimation current Ius, Ivs, Iws output from the phase current estimation unit 26, for each carrier cycle fc (for example, times T1, T2, T3 shown in FIG. , T4) (for example, change amounts dI0, dI1, dI2, dI3 shown in FIG. 6).

The angle estimation unit 29 is based on the amount of change for each phase estimation current Ius, Ivs, Iws calculated by the current difference calculation unit 28, and the rotation angle of the rotor of the motor 12 (that is, the rotor from a predetermined reference rotation position). The magnetic pole rotation angle) θ is estimated.
The rotation speed calculation unit 30 calculates the rotation speed ω of the motor 12 based on the rotation angle θ estimated by the angle estimation unit 29.

  The motor control apparatus 10 according to the present embodiment has the above-described configuration. Next, the operation of the motor control apparatus 10, in particular, the process of performing offset modulation on the duty of the gate signal will be described with reference to the accompanying drawings. To do.

First, for example, in step S01 shown in FIG. 7, the phase corresponds to the minimum value of the phase output voltages * Vu, * Vv, and * Vw with respect to the DC link current IDC in the single carrier period fc. The minimum voltage phase, that is, the on-duty minimum phase that minimizes the on-duty, which is the ratio at which the transistors UH, VH, and WH of the high-side arm of the PWM inverter 14A are turned on, is selected.
Next, in step S02, a predetermined minimum generatable on-duty (for example, zero) set in advance is set to a high-side minimum phase that is a ratio at which the high-side switching element of the on-duty minimum phase is turned on. A value obtained by subtracting from the on-duty is set as the offset duty.

Next, in step S03, a value obtained by subtracting the offset duty from the high-side U-phase on-duty, which is the ratio at which the high-side U-phase transistor UH is turned on, is newly set as the high-side U-phase on-duty. By doing so, the high-side U-phase on-duty is corrected.
Next, in step S04, a value obtained by subtracting the offset duty from the high-side V-phase on-duty, which is the ratio at which the high-side V-phase transistor VH is turned on, is newly set as the high-side V-phase on-duty. By doing so, the high-side V-phase on-duty is corrected.
Next, in step S05, a value obtained by subtracting the offset duty from the high-side W-phase on-duty, which is the ratio at which the high-side W-phase transistor WH is turned on, is newly set as the high-side W-phase on-duty. By doing so, the high-side W-phase on-duty is corrected, and a series of processing ends.

  As described above, according to the motor control device 10 according to the present embodiment, the detection interval when detecting the amount of change in the phase current can be set to a time interval equivalent to the carrier cycle, and the position of the rotor can be determined. The estimation accuracy at the time of estimation can be improved.

  In the above-described embodiment, the control unit 15 includes the offset modulation unit 25. However, the present invention is not limited to this. For example, the motor control device 10 according to the modification of the above-described embodiment illustrated in FIG. In addition, instead of the offset modulation unit 25, an on-duty command for each phase is generated at a predetermined timing including at least a start timing and an end timing of a single carrier period with respect to the DC link current IDC, or the DC link current An output voltage offset modulation unit 31 that performs offset modulation on each phase output voltage * Vu, * Vv, * Vw so that the IDC is greater than zero may be provided.

In the operation of the output voltage offset modulation unit 31, that is, the process of performing the offset modulation on the phase output voltages * Vu, * Vv, * Vw, first, for example, in step S11 shown in FIG. With respect to the DC link current IDC at fc, the minimum voltage phase corresponding to the minimum value of the phase output voltages * Vu, * Vv, * Vw, that is, the transistors UH, The on-duty minimum phase that minimizes the on-duty, which is the ratio at which VH and WH are turned on, is selected.
Next, in step S12, it is obtained by subtracting 1/2 of the power supply voltage VB and each phase output voltage of the minimum voltage phase from a predetermined minimum generatable voltage (for example, zero) set in advance. Is set as the offset voltage.

Next, in step S13, the U-phase output voltage * Vu is corrected by newly setting a value obtained by subtracting the offset voltage from the U-phase output voltage * Vu as the U-phase output voltage * Vu.
Next, in step S14, the V-phase output voltage * Vv is corrected by newly setting a value obtained by subtracting the offset voltage from the V-phase output voltage * Vv as the V-phase output voltage * Vv.
Next, in step S15, the value obtained by subtracting the offset voltage from the W-phase output voltage * Vw is newly set as the W-phase output voltage * Vw, thereby correcting the W-phase output voltage * Vw, A series of processing ends.

It is a block diagram of the control apparatus of the electric motor which concerns on embodiment of this invention. It is a block diagram of the PWM inverter of PDU shown in FIG. It is a figure which shows each switching state S1-S8 of the PWM inverter shown in FIG. Changes in the PWM signal and each phase current Iu, Iv, Iw and DC link current IDC in one cycle (carrier cycle fc) of a carrier signal composed of a single triangular wave with respect to each phase output voltage * Vu, * Vv, * Vw It is a graph which shows an example. The PWM signal and the phase currents Iu, Iv, Iw and the phase signals in one cycle (carrier cycle fc) of a single triangular wave with respect to each phase output voltage * Vu, * Vv, * Vw before and after modulation, and It is a graph which shows an example of the change of DC link current IDC. It is a graph which shows an example of the applied voltage and each phase current Iu, Iv, Iw which change for every carrier period fc. It is a flowchart which shows operation | movement of the control apparatus of the electric motor which concerns on embodiment of this invention. It is a block diagram of the control apparatus of the electric motor which concerns on the modification of embodiment of this invention. It is a flowchart which shows operation | movement of the control apparatus of the electric motor which concerns on the modification of embodiment of this invention.

Explanation of symbols

10 Motor control device 12 Motor (electric motor)
14 PWM inverter (inverter)
15 Control unit (control means)
25 Offset modulation section (modulation means)
26 Phase current estimation unit (phase current estimation means)
29 Angle estimation unit (position estimation means)
31 Output voltage offset modulation section (modulation means)

Claims (2)

An inverter that sequentially commutates energization of the motors of the plurality of phases by the pulse width modulation signal, current detection means that detects a DC side current of the inverter, and the DC side current detected by the current detection means based on the DC side current Phase current estimating means for estimating the phase current of the motor, position estimating means for estimating the position of the rotor of the motor based on the amount of change in the phase current estimated by the phase current estimating means, and the position estimating means A control device for an electric motor comprising: control means for executing switching control for controlling an on / off state of a switching element of the inverter based on the estimated position of the rotor,
A predetermined timing including at least a start timing and an end timing of a single carrier cycle for the DC-side current, by performing offset correction on a duty command that is a ratio of the on / off state of the switching element or an output voltage command for each phase. And a modulation means for generating an on-duty command for each phase ,
The modulation means sets the predetermined timing as a period extending from the start timing and the end timing to a predetermined time,
The modulation means reduces the on-duty command of the high-side arm of the minimum voltage phase in the plurality of phases to a predetermined value or less, and modulates the potential difference of the line voltage in the plurality of phases to be held to a predetermined value or more. > An electric motor control device characterized by the above. An inverter that sequentially commutates energization of the motors of the plurality of phases by the pulse width modulation signal, current detection means that detects a DC side current of the inverter, and the DC side current detected by the current detection means based on the DC side current Phase current estimating means for estimating the phase current of the motor, position estimating means for estimating the position of the rotor of the motor based on the amount of change in the phase current estimated by the phase current estimating means, and the position estimating means A control device for an electric motor comprising: control means for executing switching control for controlling an on / off state of a switching element of the inverter based on the estimated position of the rotor,
A predetermined timing including at least a start timing and an end timing of a single carrier cycle for the DC-side current, by performing offset correction on a duty command that is a ratio of the on / off state of the switching element or an output voltage command for each phase. And a modulation means for making the DC side current larger than zero ,
The modulation means sets the predetermined timing as a period extending from the start timing and the end timing to a predetermined time,
The modulation means reduces the on-duty command of the high-side arm of the minimum voltage phase in the plurality of phases to a predetermined value or less, and modulates the potential difference of the line voltage in the plurality of phases to be held to a predetermined value or more. > An electric motor control device characterized by the above.

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