JP2015139360A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller that can reduce a time lag between a carrier period corresponding to calculated three-phase currents and a carrier period for performing control using the calculated three-phase currents.SOLUTION: In the motor controller, a calculating portion calculates, when a determining portion determines that a detectable phase of three-phase currents varies between a first carrier period and a second carrier period following the first carrier period, calculates first-phase and second-phase currents on the basis of a bus bar current detected in the first carrier period, and calculates approximately a third-phase current from the first-phase and the second-phase currents; calculates the first-phase and the third-phase currents on the basis of a bus bar current detected in the second carrier period; and calculates three-phase currents at boundary timing between the first carrier period and the second carrier period on the basis the first-phase and the third-phase currents in the first carrier period and the first-phase and the third-phase currents in the second carrier period.

Description

  The present invention relates to a motor control device.

  In order to accurately control the brushless DC motor, it is necessary to accurately grasp the phase current flowing through the stator (stator) winding. If the current flowing through each phase can be grasped, the position of the rotor of the motor can be estimated and the rotational speed of the motor can be controlled.

  Generally, there are two methods for obtaining a current value of a current flowing through a node of a circuit. The first method is a method using a current sensor. In this method, a current is detected using a current transformer (CT) having a current detection transformer, a current sensor having a Hall element, or the like. The second method uses a shunt resistor. A shunt resistor is connected to a node to be obtained in advance, a voltage value at both ends of the shunt resistor is measured, and a current value is obtained from the voltage value and the resistance value.

  On the other hand, there is a 180-degree energization method (sine wave energization method) as a motor driving method that performs position sensorless driving. In the case of a three-phase motor, the motor rotation speed is set to the target rotation speed using the motor three-phase current value. PWM control is performed so that One method for detecting the current of each phase of the motor is to use a single shunt resistor inserted in the DC section of the inverter circuit. When one shunt resistor is used, the detection timings of the phase current values for two phases detected by the shunt resistor are not the same. As a result, when estimating the remaining one-phase current from the two-phase phase current based on the three-phase condition that the sum of the three-phase currents becomes zero, the two-phase phase currents with different detection timings are used. The error can increase.

  On the other hand, in Patent Document 1, in a phase current estimation device for an electric motor, two-phase phase currents estimated at symmetrical timings with respect to the carrier vertex in one period of a PWM-controlled triangular wave carrier signal are averaged. It is described that the two-phase phase current at the carrier apex is calculated, and the remaining one-phase current is calculated from the obtained two-phase phase current. Thereby, according to patent document 1, it is supposed that the three-phase phase current can be accurately estimated at the same timing.

JP 2010-88260 A

  In the phase current estimation device described in Patent Document 1, after calculating the current of two phases within the current carrier cycle, the current value of the other phase is calculated based on the current value of the two phases. Even if an attempt is made to use the three-phase current for the control in the current next carrier cycle, it is not in time due to restrictions such as the calculation speed of the microcomputer and the response characteristics of the inverter circuit. That is, in the phase current estimation device described in Patent Document 1, the process of calculating the three-phase current is performed in the current next carrier cycle, and the calculated three-phase phase current can be used. The next and next carrier cycle. Therefore, the time lag between the period corresponding to the calculated three-phase phase current (current carrier cycle) and the control period using the phase current (next carrier cycle) increases. If the time lag between the cycle corresponding to the calculated three-phase phase current and the cycle in which control is performed using the phase current is increased, the accuracy of motor control may be reduced.

  The present invention has been made in view of the above, and the time lag between the period corresponding to the calculated three-phase phase current (carrier cycle) and the period of control using the phase current (carrier period) is reduced. An object of the present invention is to obtain a motor control device capable of increasing the accuracy of motor control by reducing the motor.

  In order to solve the above-described problems and achieve the object, a motor control device according to a first aspect of the present invention converts DC power supplied from a DC power source into three-phase AC power by PWM control and supplies the motor power. Based on an inverter to be supplied, a current detector that detects a bus current of the inverter using one shunt resistor connected between the DC power source and the inverter, and a bus current detected by the current detector A three-phase voltage command value generated based on the three-phase current calculated by the calculation unit, a calculation unit that calculates a three-phase current flowing in the motor, and a generated three-phase voltage command value; A generating unit that generates a three-phase PWM signal from a triangular wave carrier signal having a predetermined period, and the calculation unit includes a three-phase PWM signal having a first carrier period and a latter half of the first carrier period. A two-phase current among the three-phase currents in the latter half of the first carrier period is calculated from the detected bus current, and a three-phase PWM signal of the second carrier period following the first carrier period A first calculator that calculates a two-phase current out of the three-phase currents in the first half of the second carrier cycle from the bus current detected in the first half of the second carrier cycle; and the first calculator A second calculation unit that calculates the remaining one phase from the two-phase current in the latter half of the calculated first carrier cycle; and the first carrier calculated by the first calculation unit and the second calculation unit. The three-phase current at the boundary timing between the first carrier period and the second carrier period is calculated based on the three-phase current in the second half of the period and the two-phase current in the first half of the second carrier period. And a third calculation unit A determination unit configured to determine whether or not a detectable phase of a three-phase current has changed between the first carrier cycle and the second carrier cycle, wherein the third calculation unit includes the first carrier If the determination unit determines that the detectable phase of the three-phase current does not change between the period and the second carrier period, the three-phase current is calculated using the two-phase current calculated by the first calculation unit. When the determination unit determines that the detectable phase has changed, the three-phase current is calculated using the current calculated by the first calculation unit and the phase current calculated by the second calculation unit, The generation unit generates a three-phase voltage command value for generating a three-phase PWM signal used in a third carrier period following the second carrier period based on the three-phase current at the boundary timing. It is characterized by.

  A motor control device according to a second aspect of the present invention is the motor control device according to the first aspect of the present invention, wherein the third calculation unit is configured to calculate a two-phase current in the latter half of the first carrier period. An interpolation calculation unit that calculates a two-phase current at the boundary timing by linear interpolation from a two-phase current in the first half of the second carrier cycle, and a two-phase current at the boundary timing calculated by the interpolation calculation unit To a calculation processing unit for calculating the remaining one-phase current among the three-phase currents.

  The motor control device according to the third aspect of the present invention is the motor control device according to the second aspect or the third aspect of the present invention, wherein the first calculation unit is the second half of the first carrier cycle. Are divided into a first period corresponding to the current of the first phase and a second period corresponding to the current of the second phase at the second period side from the center in the first period. Based on the bus current detected at the first timing, the current of the first phase at the first timing is calculated, and the second timing on the first period side from the center in the second period. The second phase current at the second timing is calculated based on the bus current detected at the second timing, and the second calculation unit calculates the second phase current and the second phase current at the first timing. Of the second phase at the timing of From the flow Prefecture, characterized by approximately calculating the current of the third phase in the third timing between the second timing and the first timing.

  According to the present invention, the motor control accuracy can be improved by reducing the time lag between the period carrier period corresponding to the calculated three-phase phase current and the carrier period controlled using the phase current. Play. Further, the same processing can be performed regardless of whether or not the detectable phase of the three-phase current changes between the first carrier cycle and the second carrier cycle.

FIG. 1 is a diagram illustrating a configuration of a motor control device according to the embodiment. FIG. 2 is a diagram illustrating a configuration of the 3φ current calculator in the embodiment. FIG. 3 is a diagram illustrating a magnitude relationship between three-phase voltage commands in the embodiment. FIG. 4 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 5 is a diagram illustrating the operation of the interpolation calculation unit in the embodiment. FIG. 6 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 7 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 8 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 9 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 10 is a diagram illustrating an operation of the motor control device according to the embodiment. FIG. 11 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 12 is a diagram illustrating the operation of the motor control device according to the comparative example. FIG. 13 is a diagram illustrating an operation of a motor control device according to another comparative example. FIG. 14 is a diagram illustrating an operation of a motor control device according to another comparative example.

  Embodiments of a motor control device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  A motor control apparatus 100 according to an embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a control device 100 for the motor M.

  The motor control device 100 generates a control signal by PWM modulation and controls the sensorless synchronous motor M. The motor M is, for example, PMSM (permanent magnet synchronous motor). In driving the PMSM, since it is necessary to synchronize the rotation of the rotor and the rotating magnetic field generated by the stator coil, it is necessary to detect the position of the rotor (rotational position). As described above, when the motor M is a sensorless synchronous motor that does not have a position detection sensor, position sensorless driving for driving the motor M is required.

  When driving a sensorless synchronous motor by sinusoidal drive, it is necessary to detect the phase current flowing in each phase of the stator winding of the motor. By detecting the motor current, the position of the rotor is estimated and the motor Control the rotation.

  At this time, in order to detect the motor current of the three-phase motor with the current sensor, it is necessary to detect at least the two-phase motor current. The current sensor for detecting the motor current has a large cost ratio in the entire control circuit, and if two more sensors are required, a large burden is imposed on the cost.

  In this embodiment, instead of the two current sensors that detect the two-phase motor current, the current is detected by a shunt resistor connected to the bus portion of the inverter of the motor control device 100. The motor current is reproduced by detecting the current together with information on the switching state of the inverter.

  Note that this motor current detection (reproduction / estimation) method using one shunt resistor is often referred to as one shunt current detection.

  The motor control device 100 according to the embodiment employs a 180-degree energization method (sine wave energization method), a position sensorless method, and a shunt current detection method as a control method. For example, when controlling the motor M, the motor control device 100 detects the bus current Is using one shunt resistor Rs, generates a control signal by PWM modulation according to the detected bus current Is, and generates the motor M. To control. Specifically, the motor control device 100 includes an inverter 10, a current detection unit 20, a calculation unit 60, a voltage detection unit 30, and a generation unit 40.

The inverter 10 receives direct-current power from the direct-current power supply _EDC, and receives three-phase (U-phase, V-phase, W-phase) PWM signals Up, Un, Vp, Vn, Wp, Wn from the generation unit 40. The inverter 10 converts DC power into three-phase AC power in accordance with the three-phase PWM signals Up to Wn. The inverter 10 drives the motor M by outputting the converted three-phase AC power to the motor M.

  Specifically, the inverter 10 includes upper arm switching elements SWup, SWvp, and SWwp and lower arm switching elements SWun, SWvn, and SWwn. The inverter 10 converts the DC power into three-phase AC power by turning on / off the switching elements SWup to SWwn according to the three-phase PWM signals Up to Wn. Note that free-wheeling diodes Dupd to Dwnd are further connected to both ends of each of the switching elements SWup to SWwn.

  The current detection unit 20 detects the bus current Is using one shunt resistor Rs. Specifically, the current detection unit 20 includes a shunt resistor Rs and a current detection circuit 21.

The shunt resistor Rs is connected between the DC power supply _EDC and the inverter 10. The shunt resistor Rs, for example, is inserted in the N on the line L _N is a DC line between the terminals and the inverter 10 of the N side of the DC power source E _DC. Incidentally, the shunt resistor Rs, for example, may be inserted into the P line L _P is a DC line between the terminals and the inverter 10 of the P side of the DC power source E _DC.

  A bus current Is flows through one shunt resistor Rs according to the U-phase current, V-phase current, and W-phase current in the inverter 10. At this time, a voltage drop occurs across the shunt resistor Rs. The current detection circuit 21 detects the bus current Is flowing through the shunt resistor Rs from the magnitude of the voltage drop and the resistance value of the shunt resistor Rs, and outputs the detection result to the calculation unit 60.

  The calculation unit 60 calculates the three-phase currents iu, iv, and iw based on the bus current Is detected by the current detection unit 20 and the three-phase PWM signals Up to Wn generated by the generation unit 40.

  Specifically, the calculation unit 60 includes a 3φ current calculator 61. The 3φ current calculator 61 receives the detected bus current from the current detection circuit 21 and receives three-phase PWM signals Up to Wn. The 3φ current calculator 61 calculates a three-phase current iu, iv, iw based on the value of the bus current and the three-phase PWM signals Up to Wn. The 3φ current calculator 61 outputs the calculated three-phase currents iu, iv, iw to the generation unit 40. Details of the configuration and operation of the 3φ current calculator 61 will be described later.

The voltage detection unit 30 detects a bus voltage. Specifically, the voltage detection unit 30 includes a DC voltage detection circuit 31 and a DC voltage calculator 32. The DC voltage detection circuit 31 detects a bus voltage between the P line L _P and the N line L _N and outputs the detection result to the DC voltage calculator 32. The DC voltage calculator 32 converts the detection result into a DC voltage Vdc and outputs the converted DC voltage Vdc to the generation unit 40.

  The generation unit 40 receives a speed command ωm * from the outside (for example, a host controller), receives three-phase currents iu, iv, and iw from the calculation unit 60, and receives a DC voltage Vdc from the voltage detection unit 30. The generating unit 40 generates the three-phase PWM signals Up to Wn based on the speed command ωm *, the three-phase currents iu, iv, iw, and the DC voltage Vdc. For example, the generation unit 40 generates the three-phase PWM signals Up to Wn so that the rotor in the motor M rotates according to the speed command ωm *.

  At this time, the generator 40 separates the motor current into a “torque current component” (q-axis component) proportional to the permanent magnet torque and an “excitation current component” (d-axis component) that changes the magnitude of the magnetic flux. By handling, it is possible to improve controllability (high efficiency, high speed response, etc.).

  In the case of alternating current, if handled in a three-phase fixed coordinate system, the voltage and current of each phase always change even in a steady state, so it is difficult for the controller to follow the command value. For example, a PI (proportional integral) controller is generally used as the current controller, but if the proportional control gain is increased to improve tracking, the control becomes unstable.

  As a coordinate system widely used in such a case, there is a dq coordinate system. This is based on the magnet direction of the rotor, and is the axis of the rotating coordinate system in which the coordinate system rotates as the rotor rotates. Even in the fixed coordinate system, the amount of alternating current can be treated as the amount of direct current on this coordinate axis, and becomes a constant value in a steady state. Moreover, even if a PI controller is used, current control without steady deviation can be realized. For example, a magnet having a d-axis in the S → N pole direction and a q-axis shifted from the d-axis in the rotation direction by 90 [deg] is used.

  Specifically, the generation unit 40 includes a 3φ / dq coordinate converter 42, a position / speed estimator 44, a 1 / Pn converter 51, a subtractor 52, a d-axis current setting unit 48, a subtractor 46, and a speed controller. 49, a subtracter 47, a d-axis q-axis voltage setting unit 45, a dq / 3φ coordinate converter 43, and a PWM generator 41.

  The 3φ / dq coordinate converter 42 receives the three-phase currents iu, iv and iw from the 3φ current calculator 61 and positions the phase angle θdq of the rotating coordinate system (dq coordinate system) relative to the fixed coordinate system (UVW coordinate system). Receive from speed estimator 44. The 3φ / dq coordinate converter 42 converts the current vector (iu, iv, iw) in the fixed coordinate system into the current vector (id, iq) in the rotational coordinate system using the phase angle θdq. The 3φ / dq coordinate converter 42 outputs the converted d-axis current id to the position / speed estimator 44, the d-axis q-axis voltage setter 45, and the subtractor 46, and the converted q-axis current iq is output to the position. Output to the speed estimator 44, the d-axis q-axis voltage setter 45, and the subtractor 47.

  The position / speed estimator 44 receives the d-axis current id and the q-axis current iq from the 3φ / dq coordinate converter 42, and receives the d-axis voltage command Vd * and the q-axis voltage command Vq * as the d-axis q-axis voltage setting unit 45. Receive from. The position / velocity estimator 44 determines the electrical estimated angular velocity ωe of the voltage vector and the phase of the rotating coordinate system based on the d-axis current id, the q-axis current iq, the d-axis voltage command Vd *, and the q-axis voltage command Vq *. Each angle θdq is estimated. The position / velocity estimator 44 outputs the electrical estimated angular velocity ωe to the 1 / Pn converter 51 and outputs the phase angle θdq to the 3φ / dq coordinate converter 42 and the dq / 3φ coordinate converter 43.

  The 1 / Pn converter 51 receives the electrical estimated angular velocity ωe from the position / velocity estimator 44. The 1 / Pn converter 51 multiplies, for example, the electrical estimated angular velocity ωe by 1 / Pn (Pn is the number of pole pairs), thereby converting the electrical estimated angular velocity ωe into the mechanical estimated angular velocity ωm of the rotor in the motor M. Convert. The 1 / Pn converter 51 outputs the mechanical estimated angular velocity ωm to the subtractor 52.

  The subtractor 52 receives the mechanical estimated angular velocity ωm from the 1 / Pn converter 51 and receives the velocity command ωm * from the outside (for example, a host controller). The subtractor 52 subtracts the estimated angular speed ωm from the speed command ωm * to obtain a speed deviation Δω, and outputs the obtained speed deviation Δω to the speed controller 49.

  The d-axis current setting unit 48 generates a d-axis current command id * with a predetermined value (for example, a fixed value) and outputs it to the subtractor 46.

  The subtractor 46 receives the d-axis current command id * from the d-axis current setter 48 and receives the d-axis current id from the 3φ / dq coordinate converter 42. The subtractor 46 subtracts the d-axis current id from the d-axis current command id * to obtain a d-axis current deviation Δid, and outputs the obtained d-axis current deviation Δid to the d-axis q-axis voltage setting unit 45.

  Speed controller 49 receives speed deviation Δω from subtractor 52. The speed controller 49 obtains the q-axis current command iq * so that the speed deviation Δω approaches zero. The speed controller 49 outputs the obtained q-axis current command iq * to the subtractor 47.

  Subtractor 47 receives q-axis current command iq * from speed controller 49 and q-axis current iq from 3φ / dq coordinate converter 42. The subtractor 47 subtracts the q-axis current iq from the q-axis current command iq * to obtain the q-axis current deviation Δiq, and outputs the obtained q-axis current deviation Δiq to the d-axis q-axis voltage setting unit 45.

  The d-axis q-axis voltage setting unit 45 receives the d-axis current deviation Δid from the subtractor 46 and receives the q-axis current deviation Δiq from the subtractor 47. The d-axis q-axis voltage setting unit 45 determines the d-axis voltage according to the d-axis current deviation Δid and the q-axis current deviation Δiq (for example, the d-axis current deviation Δid and the q-axis current deviation Δiq approach zero). A command Vd * and a q-axis voltage command Vq * are obtained. The d-axis q-axis voltage setting unit 45 outputs the obtained d-axis voltage command Vd * and q-axis voltage command Vq * to the position / speed estimator 44 and the dq / 3φ coordinate converter 43.

  The dq / 3φ coordinate converter 43 receives the d-axis voltage command Vd * and the q-axis voltage command Vq * from the d-axis q-axis voltage setting unit 45, and is a rotating coordinate system with respect to the fixed coordinate system (UVVW coordinate system). The phase angle θdq of (dq coordinate system) is received from the position / speed estimator 44. The dq / 3φ coordinate converter 43 converts the voltage vector (Vd *, Vq *) of the rotating coordinate system into the voltage vector (Vu *, Vv *, Vw *) of the fixed coordinate system using the phase angle θdq. .

  That is, the dq / 3φ coordinate converter 43 performs coordinate conversion of the d-axis voltage command Vd * and the q-axis voltage command Vq * corresponding to the three-phase currents iu, iv, iw generated by the 3φ current calculator 61. Three-phase voltage commands Vu *, Vv *, and Vw * are generated. The dq / 3φ coordinate converter 43 outputs the generated three-phase voltage commands Vu *, Vv *, Vw * to the PWM generator 41.

  The PWM generator 41 receives the three-phase voltage commands Vu *, Vv *, and Vw * from the dq / 3φ coordinate converter 43 and receives the DC voltage Vdc from the DC voltage calculator 32. The PWM generator 41 generates three-phase PWM signals Up to Wn according to the three-phase voltage commands Vu *, Vv *, Vw * and the DC voltage Vdc.

  For example, the PWM generator 41 includes a normalizer 41a, a carrier generator 41b, and three comparators 41c. The normalizer 41a normalizes the absolute value of the amplitude of the three-phase voltage commands Vu *, Vv *, and Vw * to, for example, 1 using the DC voltage Vdc, and standardizes the three-phase voltage command Vu * ′. , Vv * ′ and Vw * ′ are output to the comparator 41c. Three comparators 41c are provided for three phases.

  The carrier generator 41b generates, for example, a triangular wave signal whose amplitude has an absolute value of 1 as a carrier signal (see FIG. 4), and outputs the generated carrier signals to the three comparators 41c.

  Each of the three comparators 41c generates three-phase PWM signals Up to Wn by comparing the voltage commands Vu * ', Vv *', and Vw * 'with the carrier signal. For example, the U-phase comparator 41c compares the voltage command Vu * ′ with the carrier signal, and when the carrier signal level is higher than the voltage command Vu * ′, the U-phase PWM signal Up is turned on and the Un is turned off. When the level of the carrier signal is smaller than the voltage command Vu * ′, the U-phase PWM signal Up is turned off and Un is turned on and supplied to the control terminals of the switching elements SWup and SWun, respectively. Similarly, as a result of comparing the voltage command Vv * ′ and the carrier signal, the V-phase comparator 41c generates V-phase PWM signals Vp and Vn and supplies them to the control terminals of the switching elements SWvp and SWvn, respectively. Similarly, the W-phase comparator 41c compares the voltage command Vw * ′ with the carrier signal, and as a result, generates W-phase PWM signals Wp and Wn and supplies them to the control terminals of the switching elements SWwp and SWwn, respectively. To do.

  For example, when the comparison operation is performed based on the carrier peak (when the carrier signal is a peak reference), each carrier cycle is set so that the carrier peak is at the center of the carrier cycle. Then, levels of voltage commands Vu * ′, Vv * ′, and Vw * ′ that are constant within the carrier cycle are given, and each comparator 41c has a level of the carrier signal of voltage commands Vu * ′, Vv * ′, When Vw * 'is exceeded, the P-side PWM signals Up, Vp, Wp are on level and the N-side PWM signals Un, Vn, Wn are off-level (when the P-side switching element is on, the N-side switching element Is turned off, and when the P side is off, the N side is turned on.) When the carrier signal level becomes lower than the voltage commands Vu * ', Vv *', Vw * ', the P side PWM signals Up, Vp , Wp are turned off (the N-side PWM signals Un, Vn, Wn are turned on). At this time, in each carrier cycle, the PWM signals Up, Vp, and Wp have a symmetrical pattern with respect to the peak of the carrier (see FIG. 4). At this time, the level of the voltage commands Vu *, Vv *, and Vw * can be changed for each carrier period. Therefore, when viewed in adjacent carrier periods, the PWM signals Up, Vp, and Wp are asymmetric with respect to the carrier valleys. It becomes a pattern (see FIG. 4).

  Alternatively, for example, when the comparison operation is performed based on the carrier valley (when the carrier signal is a valley reference), each carrier cycle is set so that the carrier valley is at the center of the carrier cycle. Then, voltage commands Vu * ′, Vv * ′, and Vw * ′ whose levels are constant within the carrier cycle are given, and each comparator 41c has carrier signal levels of voltage commands Vu * ′, Vv * ′, and Vw * ′. P 'PWM signals Up, Vp, Wp are turned on (when the N side PWM signals Un, Vn, Wn are turned off), and the carrier signal level is a voltage command Vu *', Vv * '. , Vw * ′ or less, the P-side PWM signals Up, Vp, Wp are turned off (the N-side PWM signals Un, Vn, Wn are on-level). At this time, in each carrier period, the PWM signals Up, Vp, and Wp have a symmetric pattern with respect to the carrier valley (not shown). At this time, the level of the voltage commands Vu *, Vv *, and Vw * can be changed for each carrier cycle. Therefore, when viewed in adjacent carrier cycles, the PWM signals Up, Vp, and Wp are asymmetric with respect to the carrier peak. It becomes a pattern (not shown).

  Next, the configuration and operation of the 3φ current calculator 61 will be described with reference to FIGS. FIG. 2 is a diagram showing the configuration of the 3φ current calculator 61. FIG. 3 is an example showing the magnitude relationship between the three-phase voltage commands Vu *, Vv *, and Vw *. FIG. 4 is a diagram illustrating the operation of the motor control device 100. FIG. 5 is a diagram illustrating the operation of the interpolation calculation unit 61f. In the following, the case where the carrier signal is a peak reference will be described by way of example, but the following concept can be similarly applied to the case where the carrier signal is a valley reference.

  The 3φ current calculator 61 calculates three-phase currents iu, iv, and iw based on the bus current Is detected by the current detector 20 and the PWM signals Up to Wn generated by the generator 40. At this time, the 3φ current calculator 61 is a phase that can be detected from the bus current according to the relationship between the pulse widths of the PWM signals Up, Vp, and Wp (= the magnitude of the three-phase voltage commands Vu *, Vv *, and Vw *). The three-phase currents iu, iv and iw are calculated while discriminating the currents.

  As shown in FIG. 3, the magnitude relationship between the three-phase voltage commands Vu *, Vv *, and Vw * changes in 1/6 period of each voltage command. For example, the magnitude relationship of the three-phase voltage commands Vu *, Vv *, and Vw * changes for each timing ta, tb, tc, and td that appears in a 1/6 cycle. At an arbitrary timing (for example, timing te) in the period of 1/6 cycle, the magnitude relationship between the three-phase voltage commands Vu *, Vv *, and Vw * does not change.

  For example, the 3φ current calculator 61 is based on the state of the three-phase PWM signals Up to Wn of the first carrier cycle which is an arbitrary carrier cycle and the bus current Is detected in the second half of the first carrier cycle. The current of the U phase (assumed to be the first phase) and the V phase (assumed to be the second phase) of the three phases U phase, V phase, and W phase is calculated, and the calculated first phase And the current of the W phase (referred to as the third phase) in the second half of the first carrier cycle is approximately calculated based on the current of the second phase. If the detectable phase of the three-phase current does not change between the first carrier period and the second carrier period following the first carrier period, the three-phase PWM signals Up to Wn of the second carrier period Based on the state and the bus current Is detected in the first half of the second carrier cycle, the currents of the first phase (U phase) and the second phase (V phase) are calculated. The 3φ current calculator 61 is based on the currents of the first phase and the second phase in the second half of the first carrier cycle and the currents of the first phase and the second phase in the first half of the second carrier cycle. The three-phase current is calculated at the boundary timing between the first carrier period and the second carrier period. When the detectable phase of the three-phase current changes between the first carrier period and the second carrier period, that is, the three-phase PWM signals Up to Wn of the second carrier period and the second carrier period When the currents of the first phase (U phase) and the third phase (W phase) are calculated based on the bus current Is detected in the first half of the carrier cycle, the first phase in the second half of the first carrier cycle And the third phase at the boundary timing between the first carrier period and the second carrier period based on the current of the third phase and the current of the first phase and the third phase in the first half of the second carrier period. Is calculated. By calculating the third phase in the second half of the first carrier period in this way, the three-phase current is calculated in each of the cases where the detectable phase of the three-phase current does not change across the boundary timing. Can be calculated.

  The 3φ current calculator 61 outputs the calculated three-phase current to the generation unit 40 within the second carrier period, for example. In response to this, the generation unit 40 converts the calculated three-phase current into a two-phase current id, iq, and a two-phase current command id * based on the converted two-phase current and the speed command ωm *. , Iq *, two-phase voltage commands Vd *, Vq * are generated so that the current deviation becomes zero, and the three-phase voltage commands Vu *, Vv *, Vw are generated from the two-phase voltage commands Vd *, Vq *. By converting to *, three-phase voltage commands Vu *, Vv *, and Vw * used for the third carrier period following the second carrier period are generated. Then, the generation unit 40 generates the three-phase PWM signals Up to Wn based on the generated three-phase voltage commands Vu *, Vv *, Vw * and the detected DC voltage Vdc.

  For example, in the case shown in FIG. 4, the detectable phase of the three-phase current changes between the carrier cycle Tc1 and the carrier cycle Tc2. For example, when the boundary timing tc12 between the carrier period Tc1 and the carrier period Tc2 coincides with the timing tb (see FIG. 3), Vv *> Vw *> Vu * in the carrier period Tc1, but Vw * in the carrier period Tc2. *> Vv *> Vu *.

  In this case, the 3φ current calculator 61 determines the carrier current Is based on the on / off timing of the three-phase PWM signals Up to Wn of the carrier cycle Tc1 and the bus current Is detected in the second half period Tc1b of the carrier cycle Tc1. The U-phase and V-phase currents iu and iv are calculated in the second half period Tc1b of the cycle Tc1. At the same time, the 3φ current calculator 61 approximately calculates the W-phase current iw in the second half period Tc1b of the carrier cycle Tc1 from the calculated U-phase and V-phase currents iu and iv. Based on the three-phase PWM signals Up to Wn of the carrier period Tc2 and the bus current Is detected in the first period Tc2a of the carrier period Tc2, the 3φ current calculator 61 calculates the U in the first period Tc2a of the carrier period Tc2. Phase and W phase currents iu and iw are calculated. At this time, the 3φ current calculator 61 changes the detectable phase of the three-phase current between the carrier cycle Tc1 and the carrier cycle Tc2, and thus the U-phase and W-phase currents iu in the second half period Tc1b of the carrier cycle Tc1. , Iw and currents iu, iw of the U phase and W phase in the first half period Tc2a of the carrier cycle Tc2, the two-phase currents iu, iw at the boundary timing tc12 between the carrier cycle Tc1 and the carrier cycle Tc2 are calculated. . The 3φ current calculator 61 calculates the V-phase current iv based on the U-phase and W-phase currents iu and iw at the boundary timing tc12.

  The 3φ current calculator 61 outputs the three-phase currents iu, iv, iw at the calculated boundary timing tc12 to the generator 40, for example, within the carrier period Tc2. For example, the 3φ current calculator 61 outputs the calculated currents iu, iv, and iw at the three-phase boundary timing tc12 to the generation unit 40, for example, in the second half period Tc2b of the carrier cycle Tc2. In response to this, the generation unit 40 converts the three-phase voltage commands Vu *, Vv *, and Vw * for the carrier cycle Tc3 following the carrier cycle Tc2 in the Tc2b period into the three-phase currents iu, iv, and iw at the boundary timing tc12. Generate based on

  That is, the generation unit 40 converts the three-phase currents iu, iv, and iw at the boundary timing tc12 into the two-phase currents id and iq by the start timing of the carrier cycle Tc3, and converts the converted two-phase current and the speed command ωm. The two-phase voltage commands Vd * and Vq * are generated so that the current deviation from the two-phase current commands id * and iq * based on * is zero, and 3 from the two-phase voltage commands Vd * and Vq * The three-phase voltage commands Vu *, Vv *, and Vw * used for the carrier cycle Tc3 are generated by converting into the phase voltage commands Vu *, Vv *, and Vw *.

  As shown in FIG. 2, the 3φ current calculator 61 includes an AD conversion unit 61a, a determination unit 61b, a first calculation unit 61c, a second calculation unit 61d, and a third calculation unit 61e. The third calculation unit 61e includes An interpolation calculation unit 61f and a calculation processing unit 61g.

  The AD conversion unit 61 a receives the bus current Is detected by the current detection circuit 21. The AD conversion unit 61a AD converts the bus current Is (analog signal) to generate the bus current Is (digital signal). The AD conversion unit 61a outputs the bus current Is (digital signal) to the first calculation unit 61c. The timing for acquiring the bus current Is is performed based on the three-phase PWM signals Up to Wn, details of which will be described later.

  The determination unit 61b can detect the phase of the three-phase current from the bus current Is when the magnitude relationship of the pulse widths of the three-phase PWM signals Up to Wn changes between the first carrier period and the second carrier period. Is determined to change. The determination result is output to the third calculator 61e.

  The first calculator 61c receives the bus current Is (digital signal) from the AD converter 61a. The first calculator 61c calculates a two-phase current in the second half of the first carrier cycle from the PWM signal and the bus current Is detected in the second half of the first carrier cycle. The first calculation unit 61b also calculates the second carrier period from the three-phase PWM signal of the second carrier period following the first carrier period and the bus current Is detected in the first half of the second carrier period. The two-phase current in the first half is calculated. The two-phase current calculated in the second half of the first carrier cycle is output to the second calculator 61d, and the two-phase currents calculated in the second half of the first carrier cycle and the first half of the second carrier cycle are 3 is also output to the calculation unit 61e.

  Regarding the calculation of the phase current by the first calculation unit 61c, a case will be described in which the detectable phase of the three-phase current changes between the carrier period Tc1 and the carrier period Tc2 in FIG.

  As shown in FIG. 4, in the period Tc1b of the second half of the carrier cycle Tc1, since the PWM signals Up, Vp, Wp are all on in the period TP1, the switching elements SWup, SWvp, SWwp are all on and other switching is performed. The element is off (see FIG. 1). At this time, since no phase current flows, the bus current Is becomes zero.

  In the period TP2 following the period TP1 in the period Tc1b, the PWM signal Up is at the off level (the PWM signal Un is at the on level), and the PWM signals Vp, Wp are both at the on level, so that the switching elements SWun, SWvp, SWwp are all It is turned on and the other switching elements are turned off (see FIG. 1). At this time, if the direction from the inverter 10 toward the motor M is the positive direction of the current, the U-phase current −Iu = Iv + Iw flows as the bus current Is. For example, the first calculator 61c calculates the bus current Is detected in the period TP2 as the U-phase current −Iu at the timing tu1 at the center of the period TP2.

  In the period TP3 following the period TP2 in the period Tc1b, the PWM signals Up and Wp are in the off level (the PWM signals Un and Wn are in the on level), and the PWM signal Vp is in the on level, so that the switching elements SWun, SWvp, and SWwn are all It is turned on and other switching elements are turned off (see FIG. 1). At this time, if the direction from the inverter 10 toward the motor M is the positive direction of the current, the V-phase current Iv = −Iu−Iw flows as the bus current Is. For example, the first calculator 61c calculates the bus current Is detected in the period TP3 as the V-phase current Iv at the timing tv1 at the center of the period TP3.

  Further, the first calculation unit 61c calculates the first half of the carrier cycle Tc2 from the three-phase PWM signals Up to Wn of the carrier cycle Tc2 following the carrier cycle Tc1 and the bus current Is detected in the first half period Tc2a of the carrier cycle Tc2. Two-phase currents iu and iw in the period Tc2a are calculated.

  As shown in FIG. 4, in the first half period Tc2a of the carrier cycle Tc2, in the period TP4, the PWM signals Up and Vp are off level (PWM signals Un and Vn are on level), and the PWM signal Wp is on level. The switching elements SWun, SWvn, and SWwp are all turned on and the other switching elements are turned off (see FIG. 1). At this time, when the direction from the inverter 10 toward the motor M is the positive direction of the current, the W-phase current Iw = −Iu−Iv flows as the bus current Is. For example, the first calculation unit 61c calculates the bus current Is detected in the period TP4 as the W-phase current Iw at the timing tw2 at the center of the period TP4.

  In the period TP5 following the period TP4 in the period Tc2a, the PWM signal Up is in the off level (the PWM signal Un is in the on level), and the PWM signals Vp and Wp are both in the on level. Therefore, the switching elements SWun, SWvp, and SWwp are all It is turned on and the other switching elements are turned off (see FIG. 1). At this time, when the direction from the inverter 10 toward the motor M is the positive direction of the current, the U-phase current −Iu = Iv + Iw flows as the bus current Is. For example, the first calculator 61c calculates the bus current Is detected in the period TP5 as the U-phase current −Iu at the timing tu2 at the center of the period TP5.

  In the period TP6 following the period TP5 in the period Tc2a, since the PWM signals Up, Vp, Wp are all on level, the switching elements SWup, SWvp, SWwp are all on and the other switching elements are off (see FIG. 1). ). At this time, no phase current flows as a bus current, and the bus current Is becomes zero.

  The first calculation unit 61c interpolates and calculates the currents of the first phase and the second phase in the second half of the first carrier cycle and the currents of the first phase and the third phase in the first half of the second carrier cycle. To the unit 61f. For example, the first calculation unit 61c outputs the U-phase current −Iu at timing tu1, the V-phase current Iv at timing tv1, the W-phase current Iw at timing tw2, and the U-phase current −Iu at timing tu2 to the interpolation calculation unit 61f. To do.

  FIG. 4 illustrates the case where the detectable phase of the three-phase current changes between the first carrier cycle and the second carrier cycle. However, when the detectable phase does not change, the first calculation unit 61c Is a two-phase current in the second half of the first carrier cycle from the three-phase PWM signal of the first carrier cycle and the bus current detected in the second half of the first carrier cycle, where the first phase and Calculate the current of the second phase. In addition, the first calculation unit 61c calculates the first phase and the first phase in the first half of the second carrier period from the three-phase PWM signal of the second carrier period and the bus current detected in the first half of the second carrier period. The currents of the two phases are calculated, and the calculated phase currents are output to the interpolation calculation unit 61f.

  The first calculation unit 61c outputs the calculated currents of the first phase and the second phase in the second half of the first carrier cycle to the second calculation unit 61d. For example, the first calculation unit 61c outputs the U-phase current −Iu at the timing tu1 and the V-phase current Iv at the timing tv1 to the second calculation unit 61d.

  Note that the first calculation unit 61c determines the second half of the calculated first carrier period regardless of whether or not the detectable phase of the three-phase current changes between the first carrier period and the second carrier period. Is output to the second calculator 61d.

  The second calculation unit 61d receives the currents of the first phase and the second phase in the second half of the first carrier cycle from the first calculation unit 61c. For example, the second calculation unit 61d receives the U-phase current −Iu at the timing tu1 and the V-phase current Iv at the timing tv1 from the first calculation unit 61c. The second calculator 61d approximately calculates the W-phase current -Iw, which is the remaining current of the third phase, from the currents of the first phase and the second phase received from the first calculator 61c.

  The second calculation unit 61d calculates the three-phase current regardless of whether or not the detectable phase of the three-phase current changes between the first carrier period and the second carrier period. The remaining one-phase current is approximately calculated from the two-phase current.

  For example, in the case illustrated in FIG. 4, the second calculation unit 61d uses the three-phase condition Iu + Iv + Iw = 0 from the U-phase current −Iu at the timing tu1 and the V-phase current Iv at the timing tv1 (for example, between the timing tu1 and the timing tv1). The W-phase current Iw1 at the center (timing) tw1 is approximately calculated. That is, the second calculation unit 61d can approximately obtain the W-phase current Iw1 at the timing tw1 using the following formula 1. The second calculator 61d can perform the process of calculating the W-phase current Iw1 (current code: +) at the timing tw1 within the first half period Tc2a of the carrier cycle Tc2.

      Iw1 = − {(− Iu1) + (+ Iv1)} Equation 1

  The second calculation unit 61d outputs the calculated third-phase current (for example, the W-phase current Iw1 at the timing tw1) to the interpolation calculation unit 61f as the third-phase current in the second half of the first carrier cycle. .

  The interpolation calculation unit 61f includes the currents of the first phase and the second phase in the second half of the first carrier cycle from the first calculation unit 61c, and the first phase and the third phase in the first half of the second carrier cycle. And the current of the third phase in the second half of the first carrier cycle from the second calculator 61d.

  When the interpolation calculation unit 61f receives the determination from the determination unit 61b that the detectable phase of the three-phase current does not change between the first carrier cycle and the second carrier cycle, the interpolation calculation unit 61f receives the first calculation from the first calculation unit 61c. Based on the first phase and second phase currents in the second half of one carrier cycle and the first and second phase currents in the first half of the second carrier cycle, The currents of the first phase and the second phase at the boundary timing with the carrier cycle are calculated by linear interpolation.

  In addition, when the interpolation calculation unit 61f receives a determination from the determination unit 61b that the detectable phase of the three-phase current is changed between the first carrier period and the second carrier period, the interpolation calculation unit 61f outputs a signal from the first calculation unit 61c. First phase current in the second half of the first carrier period, first phase and third phase current in the first half of the second carrier period, and third phase current in the second half of the first carrier period Based on the above, the currents of the first phase and the third phase at the boundary timing between the first carrier period and the second carrier period are calculated by linear interpolation.

  As described above, the interpolation calculation unit 61f is configured to detect one of the three phases at the boundary timing regardless of whether or not the detectable phase of the three-phase current changes between the first carrier period and the second carrier period. A two-phase current can be obtained.

  For example, as illustrated in FIG. 4, the interpolation calculation unit 61f calculates the two-phase currents iu and iw in the second half period Tc1b of the carrier cycle Tc1 and the two-phase currents iu and iw in the first half period Tc2a of the carrier cycle Tc2. Two-phase currents iu and iw at the boundary timing tc12 are calculated by linear interpolation. At this time, the interpolation calculation unit 61f can recognize the positions on the time axis of the timings tu1, tw1, tw2, tu2, and the boundary timing tc12 using the three-phase PWM signals Up to Wn. For example, the interpolation calculation unit 61f calculates the U-phase current -Iu at the boundary timing tc12 by linear interpolation from the U-phase current -Iu at the timing tu1 and the U-phase current -Iu at the timing tu2. The interpolation calculating unit 61f calculates the W-phase current Iw at the boundary timing tc12 from the W-phase current Iw at the timing tw1 and the W-phase current Iw at the timing tw2 by linear interpolation. The interpolation calculation unit 61f can perform the process of calculating the two-phase currents iu and iw at the boundary timing tc12 by linear interpolation in the second half period Tc2b of the carrier cycle Tc2.

  At this time, as described above, the level of the voltage commands Vu *, Vv *, and Vw * can be changed for each carrier period. Therefore, when viewed in adjacent carrier periods, the PWM signals Up, Vp, and Wp The pattern is asymmetric with respect to (boundary timing). For example, as shown in FIG. 4, the PWM signals Up, Vp, Wp in the second half period Tc1b of the carrier cycle Tc1 and the PWM signals Up, Vp, Wp in the first half period Tc2a of the carrier cycle Tc2 are at the boundary timing tc12. The pattern is asymmetric.

  If the interpolation calculation unit 61f simply averages the U-phase current -Iu at the timing tu1 and the U-phase current -Iu at the timing tu2, the obtained U-phase current is the U-phase current at a timing shifted from the boundary timing tc12. Become. Alternatively, when the interpolation calculation unit 61f simply averages the W-phase current Iw at the timing tw1 and the W-phase current Iw at the timing tw2, the obtained W-phase current becomes the W-phase current at a timing shifted from the boundary timing tic12. End up. That is, when the two-phase current in the second half of the first carrier cycle and the two-phase current in the first half of the second carrier cycle are calculated by a simple average, the obtained two-phase currents are currents having different timings. (See FIGS. 4 and 5), the calculation error may increase.

  In the present embodiment, the interpolation calculation unit 61f calculates the phase current to be obtained by linear interpolation without calculating it with a simple average. That is, the interpolation calculation unit 61f is linear in order to calculate the two-phase current at the boundary timing between the two-phase current in the second half of the first carrier cycle and the two-phase current in the first half of the second carrier cycle. Use interpolation.

  For example, as illustrated in FIG. 4, the interpolation calculation unit 61f calculates the two-phase currents iu and iw in the second half period Tc1b of the carrier cycle Tc1 and the two-phase currents iu and iw in the first half period Tc2a of the carrier cycle Tc2. Two-phase currents iu and iw at the boundary timing tc12 are calculated by linear interpolation. At this time, the interpolation calculation unit 61f can recognize the positions on the time axis of the timings tu1, tw1, tw2, tu2, and the boundary timing tc12 using the three-phase PWM signals Up to Wn. For example, the interpolation calculation unit 61f calculates the U-phase current -Iu at the boundary timing tc12 by linear interpolation from the U-phase current -Iu at the timing tu1 and the U-phase current -Iu at the timing tu2. The interpolation calculating unit 61f calculates the W-phase current Iw at the boundary timing tc12 from the W-phase current Iw at the timing tw1 and the W-phase current Iw at the timing tw2 by linear interpolation. The interpolation calculation unit 61f can perform the process of calculating the two-phase currents iu and iw at the boundary timing tc12 by linear interpolation in the second half period Tc2b of the carrier cycle Tc2.

  For example, as illustrated in FIG. 5, when the U-phase current at the timing tu1 is −Iu1 and the U-phase current at the timing tu2 is −Iu2, the length of the period from the timings tu1 to tc12 is Ti, and the timings tc12 to tu2 Assuming that the length of the period is Tiv, the U-phase current Iu12 at the boundary timing tc12 can be obtained by the following Equation 2.

      Iu12 = {(− Iu2) − (− Iu1)} × Ti / (Tiv + Ti) + (− Iu1) Equation 2

  Similarly, when the W-phase current at timing tw1 is Iw1 and the W-phase current at timing tw2 is Iw2, the length of the period from timing tw1 to tw12 is Tii, and the length of the period from timing tw12 to tw2 is Tiii. Then, the W-phase current Iw12 at the boundary timing tc12 can be obtained by the following Equation 3.

      Iw12 = {(+ Iw2) − (+ Iw1)} × Tii / (Tiii + Tii) + (+ Iw1) Equation 3

  The interpolation calculation unit 61f outputs the currents of the first phase and the third phase at the boundary timing to the calculation processing unit 61g. For example, the interpolation calculation unit 61f outputs the U-phase current Iu12 and the W-phase current Iw12 at the boundary timing tc12 to the calculation processing unit 61g.

  The calculation processing unit 61g receives the currents of the first phase and the third phase at the boundary timing from the interpolation calculation unit 61f. For example, the calculation processing unit 61g receives the U-phase current Iu12 and the W-phase current Iw12 at the boundary timing tc12 from the interpolation calculation unit 61f. The calculation processing unit 61g calculates the remaining second-phase current from the first-phase and third-phase currents calculated by linear interpolation among the three-phase currents.

  For example, as illustrated in FIG. 4, the calculation processing unit 61g calculates the V-phase current Iv12 at the boundary timing tc12 from the U-phase current Iu12 and the W-phase current Iw12 at the boundary timing tc12 using the three-phase condition Iu + Iv + Iw = 0. That is, the calculation processing unit 61g can obtain the V-phase current Iv12 at the boundary timing tc12 by the following formula 4. The calculation processing unit 61g can perform the process of calculating the V-phase current Iv12 at the boundary timing tc12 within the latter half period Tc2b of the carrier cycle Tc2.

      Iv12 = −Iu12−Iw12 Equation 4

  The calculation processing unit 61g outputs the three-phase currents of Iu12 and Iw12 together with the calculated Iv12 to the 3φ / dq coordinate converter 42 (see FIG. 1) of the generation unit 40.

  Next, the flow of operations for estimating the three-phase current in the motor control device 100 will be described with reference to FIGS. 6 to 9 are diagrams illustrating the operation of the motor control device 100.

  In the motor control apparatus 100, two points are sampled in the second half of the previous carrier cycle and two points are sampled in the first half of the subsequent carrier cycle with respect to the carrier valley (boundary timing). The motor control device 100 associates the time, the detected value, the detected phase, and the current code for each of these sampling points. Then, the motor control device 100 calculates the current value (for two phases) at the carrier valley timing (boundary timing) from the sampling data by linear interpolation. The motor control device 100 calculates the current value for the remaining one phase from the current value for the two phases at the carrier valley timing.

More specifically, as shown in FIG. 6, the bus current generated in the second half of the carrier cycle before the boundary timing is
0 [A]
↓
Negative minimum voltage phase (U phase in the figure)
↓
Positive maximum voltage phase (V phase in the figure)
↓
0 [A]
It becomes.

  Among these, sampling is performed in a section where a negative minimum voltage phase current (U-phase current in the case of FIG. 6) and a positive maximum voltage phase current (V-phase current in the case of FIG. 6) are generated.

As shown in FIG. 7, the bus current generated in the first half of the carrier cycle after the boundary timing is
0 [A]
↓
Positive maximum voltage phase (W phase in the figure)
↓
Negative minimum voltage phase (U phase in the figure)
↓
0 [A]
It becomes.

  Among these, sampling is performed in a section where a positive maximum voltage phase current (W-phase current in the case of FIG. 7) and a negative minimum voltage phase current (U-phase current in the case of FIG. 7) are generated.

  At this time, the symbols i, ii, iii, and iv are assigned to the sampling points shown in FIG. 8 in order (see FIG. 5), and the sampling point data shown in FIG. The value, the detection phase, and the current code are associated and stored in a storage unit (not shown).

  Then, the motor control device 100 calculates the current value (for two phases) at the carrier valley timing (boundary timing) from the sampling data by linear interpolation. Data of the same detection phase is retrieved from the data stored in association.

  8 and 9, i and iv are picked up as the U phase. The value at the carrier valley is calculated by linear interpolation.

  For example, the current value of the U phase at the carrier valley timing is calculated by the above mathematical formula 2 stored in a storage unit (not shown). In Equation 2, Ti represents the time from timing i (tu1) to carrier valley (tc12). Tiv represents the time from carrier valley (tc12) to timing iv (tu2).

  On the other hand, since the detection phases of ii and v are different between the V phase and the W phase, the current value at the carrier valley timing cannot be interpolated as it is. Therefore, using the i (U phase) and v (V phase) data in the second half of the carrier (down count), the current value of the W phase at the sampling point ii between i and v (for example, the center) is approximately calculated. To do.

  For example, the current value of the W phase at the sampling point ii is calculated by Equation 1 above. Then, the current value of the W phase at the carrier valley timing is calculated by Equation 3 stored in a storage unit (not shown). In Equation 3, Tii represents the time from timing ii (tw1) to carrier valley (tc12). Tiii represents the time from the carrier valley (tc12) to the timing iii (tw2). Note that Tv shown in FIG. 9 represents the time from timing v (tv1) to carrier valley (tc12), but is not used for calculation of the current value.

  The control device 100 calculates the current value for the remaining one phase from the current value for the two phases at the carrier valley timing (boundary timing). For example, the control device 100 calculates the remaining V-phase current value from the current values for the two phases calculated by Equations 2 and 3. Since the current data for the two phases calculated by Equations 2 and 3 are approximately time-matched, Iu + Iv + Iw≈0 holds. Therefore, the remaining V-phase current value is calculated by the above mathematical formula 4 stored in a storage unit (not shown).

  Here, suppose that, as shown in FIG. 12, the current value of another phase is calculated based on the current value of two phases after calculating the current of two phases within the current carrier cycle Tc902. In this case, it is not in time to use the calculated three-phase current for control in the current next carrier cycle Tc 903. That is, in the motor control device shown in FIG. 12, a process for calculating a three-phase current and generating a voltage command from the current value is performed in the current next carrier cycle Tc903, and the generated three-phase current command is generated. Is used for the current next further carrier cycle Tc904. Therefore, the time lag between the cycle corresponding to the calculated three-phase phase current (current carrier cycle Tc902) and the control cycle (next carrier cycle Tc904) is increased. When the time lag between the cycle corresponding to the calculated three-phase phase current and the control cycle becomes large, the accuracy of motor control decreases.

  Further, suppose that the calculation unit 60 does not perform a process of approximately calculating the remaining one-phase current from the estimated two-phase current in the second half of the first carrier cycle. In this case, the first carrier period and the second carrier period are always used by using the two-phase current calculated in the second half of the first carrier period and the two-phase current calculated in the first half of the second carrier period. It is necessary to calculate a two-phase current at the boundary timing between the two. If the detectable phase of the three-phase current does not change between the first carrier period and the second carrier period, a two-phase current can be calculated as shown in FIG. As shown in FIG. 13, since the detectable phase of the three-phase current does not change between the carrier period Tc801 and the carrier period Tc802, the common two-phase (U-phase, W-phase) current before and after the boundary timing tc812 is obtained. The current value between the two can be calculated.

  However, when the detectable phase of the three-phase current changes between the first carrier period and the second carrier period, it is impossible to calculate the two-phase current as shown in FIG. As shown in FIG. 14, the detectable phase of the three-phase current changes depending on the carrier cycle Tc 701 and the carrier cycle Tc 702, so that only one phase current can be calculated as a common phase before and after the boundary timing tc 712. That is, only one phase (U phase) is common to the two phases (U phase and V phase) estimated for the carrier cycle Tc 701 and the two phases (U phase and W phase) calculated for the carrier cycle Tc 701. This makes it impossible to calculate a two-phase current, and naturally, it is also impossible to calculate a three-phase current.

  On the other hand, in the embodiment, in the calculation unit 60 of the motor control device 100, the first calculation unit includes the three-phase PWM signal of the first carrier cycle and the bus current detected in the second half of the first carrier cycle. The two-phase current among the three-phase currents in the second half of the first carrier period is calculated from the above and the three-phase PWM signal of the second carrier period following the first carrier period and the first half of the second carrier period The two-phase current is calculated from the three-phase current in the first half of the second carrier cycle from the bus current detected in step (b). The second calculation unit calculates the remaining one phase from the two-phase current in the second half of the first carrier cycle calculated by the first calculation unit. The third calculation unit calculates the first carrier cycle and the second carrier cycle based on the phase current calculated in the second half of the first carrier cycle and the phase current calculated in the first half of the second carrier cycle. The three-phase current at the boundary timing is calculated. The determination unit determines whether or not the detectable phase of the three-phase current has changed when the intermediate voltage phase has changed due to the magnitude of the PWM of each phase between the first carrier period and the second carrier period. judge. When the determination unit determines that the detectable phase does not change, the third calculation unit calculates a three-phase current using the current calculated by the first calculation unit, and determines that the detectable phase has changed. Is determined, a three-phase current is calculated using the current calculated by the first calculation unit and the phase current calculated by the second calculation unit. The generation unit 40 generates a three-phase voltage command value for generating a three-phase PWM signal used in a third carrier period following the second carrier period based on the three-phase current at the boundary timing. As a result, the current carrier cycle, which is the cycle corresponding to the calculated three-phase phase current, can be used for the voltage command of the next carrier cycle. As a result, it is possible to reduce the time lag between the carrier period corresponding to the calculated three-phase phase current and the carrier period in which control is performed using the phase current. Further, even when the phase that can be detected in the three-phase current is changed between the first carrier cycle and the second carrier cycle by the determination unit 61b and the second calculation unit 61d, the first carrier cycle and the second calculation unit 61d The three-phase current at the boundary timing with the carrier cycle can be calculated. That is, the same processing can be performed regardless of whether or not the detectable phase of the three-phase current changes between the first carrier cycle and the second carrier cycle.

  In the embodiment, in the calculation unit 60 of the motor control device 100, the interpolation calculation unit 61f performs the first phase and third phase currents in the second half of the first carrier cycle and the first half of the second carrier cycle. The first phase and third phase currents at the boundary timing are calculated by linear interpolation between the first phase and third phase currents. As a result, when the PWM signals before and after the boundary timing have an asymmetric pattern with respect to the boundary timing, the two-phase current in the second half of the first carrier period and the two-phase current in the first half of the second carrier period Thus, the two-phase current at the boundary timing can be accurately calculated.

  In the embodiment, the case where the sampling point i (timing tu1) and the sampling point v (timing tv1) are set to the central timing of the periods TP2 and TP3 in which the phase current is detected is described as an example. In order to improve the temporal consistency of the current value approximately calculated by the second calculator 61d, it is preferable that the temporal deviation between the sampling points i and v shown in FIG. 10 is small.

  Therefore, in the 3φ current calculator 61, the first calculator 61c includes a second period corresponding to the first period corresponding to the first phase current and the second phase current in the second half of the first carrier cycle. When divided into periods, the current of the first phase at the first timing is calculated based on the bus current detected at the first timing on the second period side from the center in the first period. Also good. The first calculation unit 61c calculates the current of the second phase at the second timing based on the bus current detected at the second timing on the first period side from the center in the second period. Also good.

  For example, in the case illustrated in FIG. 11, the first calculation unit 61c determines the timing tu1 ′ according to the bus current detected at the first timing tu1 ′ that is the timing of the period TP3 from the center in the period TP2 (see FIG. 4). The U-phase current at may be calculated. The first calculator 61c calculates the V-phase current at the timing tv1 ′ based on the bus current detected at the second timing tv1 ′ that is the timing on the side of the period TP2 from the center in the period TP3 (see FIG. 4). May be.

  At this time, the second calculation unit 61d calculates the first phase between the first timing and the second timing from the first phase current at the first timing and the second phase current at the second timing. The current of the third phase at the timing of 3 is approximately calculated.

  For example, in the case illustrated in FIG. 11, the second calculation unit 61d calculates the timing tu1 ′ and the second phase from the U-phase current at the first timing tu1 ′ (sampling point i ′) and the V-phase current at the timing tv1 ′. The current of the W phase at the timing tw1 between the timing tv1 ′ and the timing tv1 ′ is approximately calculated.

  As a result, as shown in FIG. 11, the temporal distance between the sampling point i 'and the sampling point ii can be made closer to each other, and the temporal distance between the sampling point ii and the sampling point v' can be made closer to each other. As a result, the temporal consistency between the sampling points i ′ and v ′ and the sampling point ii can be improved, and the approximation accuracy when the current of the third phase is approximately calculated can be improved. For example, the sampling points i and v can be made as close as possible in consideration of the switching elements SWup to SWwn to be used and the response speed of the current detection circuit 21.

  As described above, the motor control device according to the present invention is useful for controlling the motor.

DESCRIPTION OF SYMBOLS 10 Inverter 20 Current detection part 21 Current detection circuit 30 Detection part 31 DC voltage detection circuit 32 DC voltage calculator 40 Generation part 41a Normalizer 41b Carrier generator 41c Comparator 42 3φ / dq coordinate converter 43 dq / 3φ coordinate conversion 44 Position / speed estimator 45 d-axis q-axis voltage setter 46 Subtractor 47 Subtractor 48 d-axis current setter 49 Speed controller 51 1 / Pn converter 52 Subtractor 60 Calculation unit 61 3φ current calculator 61a AD Conversion unit 61b Determination unit 61c First calculation unit 61d Second calculation unit 61e Third calculation unit 61f Interpolation calculation unit 61g Calculation processing unit 100 Control device

Claims (3)

An inverter for converting DC power supplied from a DC power source into three-phase AC power by PWM control and supplying the motor to the motor;
A current detector for detecting a bus current of the inverter using one shunt resistor connected between the DC power source and the inverter;
A calculation unit that calculates a three-phase current flowing through the motor based on the bus current detected by the current detection unit;
A three-phase voltage command value is generated based on the three-phase current calculated by the calculation unit, and a three-phase PWM signal is generated from the generated three-phase voltage command value and a triangular wave carrier signal having a predetermined cycle. And a generation unit
The calculation unit includes:
A two-phase current among the three-phase currents in the second half of the first carrier cycle is calculated from the three-phase PWM signal of the first carrier cycle and the bus current detected in the second half of the first carrier cycle. And a three-phase current in the first half of the second carrier period from a three-phase PWM signal of the second carrier period following the first carrier period and a bus current detected in the first half of the second carrier period. A first calculation unit for calculating a two-phase current,
A second calculation unit that calculates the remaining one phase from the two-phase current in the second half of the first carrier period calculated by the first calculation unit;
The first carrier based on the three-phase current in the second half of the first carrier cycle and the two-phase current in the first half of the second carrier cycle calculated by the first calculator and the second calculator. A third calculation unit for calculating a three-phase current at a boundary timing between a cycle and the second carrier cycle;
A determination unit that determines whether or not the detectable phase of the three-phase current has changed between the first carrier period and the second carrier period;
The third calculator is
When the determination unit determines that the detectable phase of the three-phase current does not change between the first carrier cycle and the second carrier cycle, the two-phase current calculated by the first calculation unit is used. To calculate the current of three phases,
When the determination unit determines that a detectable phase has changed, a current of three phases is calculated using the current calculated by the first calculation unit and the phase current calculated by the second calculation unit,
The generation unit generates a three-phase voltage command value for generating a three-phase PWM signal used in a third carrier period following the second carrier period based on the three-phase current at the boundary timing. The motor control apparatus characterized by the above-mentioned. The third calculation unit calculates a two-phase current at the boundary timing by linear interpolation from a two-phase current in the second half of the first carrier cycle and a two-phase current in the first half of the second carrier cycle. An interpolation calculator;
The calculation processing unit that calculates a remaining one-phase current among the three-phase currents from the two-phase currents at the boundary timing calculated by the interpolation calculation unit. Motor control device. When the first calculation unit divides into a first period corresponding to a first phase current and a second period corresponding to a second phase current in the second half of the first carrier period, A current of the first phase at the first timing is calculated based on a bus current detected at a first timing on the second period side from the center in the first period, and the second period Calculating the current of the second phase at the second timing based on the bus current detected at the second timing on the first period side from the center at
The second calculation unit calculates the first timing and the second timing from the current of the first phase at the first timing and the current of the second phase at the second timing. The motor control device according to claim 1, wherein the current of the third phase at a third timing is approximately calculated.

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