JP2011004561A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller utilizing a multi-phase inverter and a multi-phase motor for a step-up operation, which prevents overcurrents.SOLUTION: A motor controller 1 is equipped with: a three-phase inverter circuit 10; a battery 11; a capacitor 12; and a micro computer 13. The battery 11 is connected between a neutral point N of a stator coil L1 and a DC end T2 of the three-phase inverter 10. The capacitor 12 is connected between DC ends T1 and T2 of the three-phase inverter 10. The micro computer 13 calculates a peak value of phase current based on a d-axis current command and a q-axis current command as well as the DC current flowing into the neutral point N of the stator coil L1. It corrects at least the d-axis current command or q-axis current command so that the peak value of phase current comes to be the limit value of overcurrent or smaller. Thus, the overcurrent is prevented in the motor controller 1 which utilizes the three-phase inverter 10 and a three-phase AC motor M1 for the step-up operation.

Description

  The present invention relates to a motor control device that performs a step-up operation using a multiphase inverter and a multiphase motor.

  Conventionally, some motor control devices include a multiphase inverter and a control circuit. The control circuit controls the multiphase inverter so that a multiphase AC current flows through the multiphase motor. In addition, the multiphase inverter is controlled so that the phase current of the multiphase motor does not become excessive. Specifically, the peak value of the phase current is calculated from the d-axis current command and the q-axis current command that indicate the multiphase AC current. Then, at least one of the d-axis current command and the q-axis current command is corrected so that the calculated peak value of the phase current is not more than a predetermined limit value. As a result, the peak value of the phase current flowing in practice can be made equal to or less than the limit value, and overcurrent can be prevented.

  By the way, there is a motor control device that performs a boost operation using a multiphase inverter and a multiphase motor. For example, a power conversion circuit disclosed in Patent Document 1. This power conversion circuit includes a three-phase voltage source inverter, a DC power source, and a smoothing capacitor. The three-phase induction motor includes a stator coil composed of Y-connected phase coils. Each phase end of the stator coil is connected to the AC end of the three-phase voltage source inverter. The DC power source is connected between the neutral point of the stator coil of the three-phase induction motor and the DC low potential end of the three-phase voltage source inverter. Further, the smoothing capacitor is connected between the DC high potential end and the DC low potential end of the three-phase voltage source inverter. The control circuit controls the three-phase voltage source inverter so that a three-phase alternating current flows through the three-phase induction motor. Thereby, the voltage of the DC power supply is boosted and supplied to the smoothing capacitor, and the DC voltage smoothed by the smoothing capacitor is converted into a three-phase AC voltage and supplied to the three-phase induction motor. Accordingly, a combined current of a direct current and an alternating current flows through each phase coil of the three-phase induction motor.

Japanese Patent Laid-Open No. 10-337047

  As described above, in the power conversion circuit, a combined current of a direct current and an alternating current flows through each phase coil of the three-phase induction motor. For this reason, the above-described conventional overcurrent prevention method has a problem in that the direct current component in the combined current cannot be taken into account, and the peak value of the actually flowing phase current cannot be suppressed below the limit value.

  The present invention has been made in view of such circumstances, and provides a motor control device capable of preventing overcurrent in a motor control device that performs a step-up operation using a multiphase inverter and a multiphase motor. For the purpose.

  Therefore, as a result of extensive research and trial and error, the present inventor has conducted a d-axis current command and a q-axis current command indicating a polyphase alternating current, or a d-axis forming a polyphase alternating current. The phase of a multiphase motor composed of DC current and AC current based on current and q-axis current and DC current flowing into the neutral point of the stator coil or DC current flowing out from the neutral point of the stator coil The present invention has been completed with the idea that the overcurrent can be prevented by correcting the current command so that the current or the phase current integrated value of the multiphase motor is less than the limit value.

  That is, the motor control device according to claim 1 is connected to a multiphase motor having a star-connected stator coil and supplies a multiphase inverter for supplying a phase current to the multiphase motor, and a neutral point of the stator coil. A first power source connected between one DC terminal of the multiphase inverter, one DC terminal of the multiphase inverter or a neutral point of the stator coil, and the other DC terminal of the multiphase inverter. The voltage of the first power source is boosted by controlling the multi-phase inverter so that the multi-phase AC current flows through the multi-phase motor. And a control circuit that supplies the second power source and converts the voltage of the second power source into a multi-phase AC voltage and supplies the multi-phase motor to the multi-phase motor. D-axis current command and DC current based on axial current command or d-axis current and q-axis current forming a multi-phase alternating current, and direct current flowing into the neutral point of the stator coil or direct current flowing out from the neutral point of the stator coil The current command is corrected so that the phase current of the multiphase motor composed of the combined current of the current and the alternating current or the phase current integrated value of the multiphase motor is equal to or less than the limit value. Here, the first power source and the second power source are introduced for convenience in order to distinguish the power sources. Also, the d-axis current and the q-axis current that form the multi-phase AC current are different from the d-axis current command and the q-axis current command that indicate the multi-phase AC current. It is converted into an axis and a q-axis.

  According to this configuration, a combined current of a direct current and an alternating current flows as a phase current in each phase of the multiphase motor. At the neutral point of the stator coil connected in a star shape, a current that is the number of phases that is a direct current that forms the phase current flows in or out. Therefore, the direct current that forms the phase current can be known from the direct current flowing into the neutral point of the stator coil or the direct current flowing out from the neutral point of the stator coil. Further, it is possible to know the alternating current forming the phase current from the d-axis current command and the q-axis current command instructing the multi-phase alternating current, or the d-axis current and the q-axis current forming the multi-phase alternating current. Therefore, based on the d-axis current command and the q-axis current command, or the d-axis current and the q-axis current, and the DC current flowing into the neutral point of the stator coil or the DC current flowing out from the neutral point of the stator coil. Thus, it is possible to know the phase current or the phase current integrated value in consideration of the direct current. Therefore, by correcting the current command so that the phase current or the phase current integrated value is less than or equal to the limit value, the actually flowing phase current can be reliably suppressed and overcurrent can be prevented.

  In the motor control device according to claim 2, when the phase current or the phase current integrated value exceeds the limit value, the control circuit first decreases the peak value of the phase current by decreasing the d-axis current command, If the value still does not become the limit value or less, the q-axis current command is decreased. According to this configuration, it is possible to suppress the decrease in the q-axis current command that affects the output torque of the multiphase motor as much as possible. Therefore, it is possible to prevent an overcurrent by suppressing a decrease in output torque of the multiphase motor as much as possible.

  According to a third aspect of the present invention, the control circuit controls the multi-phase inverter so that the direct current forming the phase current has a third harmonic of the alternating current forming the phase current. According to this configuration, the peak value of the phase current can be reduced by the third harmonic of the alternating current forming the phase current that the direct current forming the phase current has. Therefore, overcurrent can be further suppressed.

  The motor control device according to claim 4, wherein the control circuit controls the phase voltage command or the phase duty calculated based on the d-axis current command and the q-axis current command based on the third harmonic current command. Thus, it is characterized in that the third harmonic included in the direct current forming the phase current is controlled. According to this configuration, the phase current can be controlled by controlling the phase voltage command or the phase duty. Therefore, by controlling the phase voltage command or the phase duty based on the third harmonic current command, the third harmonic included in the direct current that forms the phase current can be reliably controlled.

  The motor control device according to claim 5, wherein the control circuit controls the phase voltage command or the phase duty based on a direct current flowing into the neutral point of the stator coil or a direct current flowing out of the neutral point of the stator coil. It is characterized by doing. According to this configuration, the direct current that forms the phase current can be known from the current flowing into the neutral point of the stator coil or the current flowing out of the neutral point of the stator coil. Therefore, by controlling based on the current flowing into the neutral point of the stator coil or the current flowing out of the neutral point of the stator coil, the phase voltage command or the phase duty is controlled in consideration of the direct current that forms the combined current. be able to. Therefore, it is possible to accurately control the third harmonic included in the direct current that forms the combined current.

  In the motor control device according to claim 6, the control circuit controls the phase current based on the rotation angle of the multiphase motor, and the detected phase current exceeds the limit value when the multiphase motor is stationary. The rotation angle of the multiphase motor is corrected according to the detected magnitude of the phase current. According to this configuration, the phase current of the multiphase motor is determined by the rotation angle. Therefore, when the detected phase current exceeds the limit value in a so-called locked state where the multiphase motor is stationary, the peak value of the phase current can be suppressed by correcting the rotation angle.

  According to a seventh aspect of the present invention, the multi-phase motor is mounted on the vehicle and generates torque for assisting steering of the steering wheel. According to this configuration, an overcurrent can be prevented in a motor control device that performs a boost operation using a multiphase inverter and a multiphase motor for assisting steering of the steering wheel.

It is a circuit diagram of the motor control device in a 1st embodiment. It is a block diagram of the control block comprised by a microcomputer. It is a circuit diagram of the equivalent circuit for demonstrating the voltage of an alternating current end. It is explanatory drawing for demonstrating the phase current of a three-phase alternating current motor. It is a flowchart for demonstrating operation | movement of an overcurrent prevention process part. It is a block diagram of the control block comprised by the microcomputer in 2nd Embodiment. It is explanatory drawing for demonstrating the phase current of a three-phase alternating current motor. It is a block diagram of the control block comprised by the microcomputer in 3rd Embodiment. It is a circuit diagram which shows another example of a connection of a battery and a capacitor | condenser. It is a circuit diagram which shows another example of a connection of a battery and a capacitor | condenser. It is a circuit diagram which shows another example of a connection of a battery and a capacitor | condenser. It is a circuit diagram which shows another example of a connection of a current detection element. It is a circuit diagram which shows another example of a connection of a current detection element. It is a circuit diagram which shows another example of a connection of a current detection element.

  Next, the present invention will be described in more detail with reference to embodiments.

(First embodiment)
First, the configuration of the motor control device will be described with reference to FIG. Here, FIG. 1 is a circuit diagram of the motor control device according to the first embodiment.

  A motor control device 1 shown in FIG. 1 is a device for controlling a three-phase AC motor M1 (multiphase motor). The three-phase AC motor M1 is, for example, a motor that is mounted on a vehicle and generates torque for assisting steering of the steering wheel. The three-phase AC motor M1 includes a stator coil L1. The stator coil L1 includes a U-phase coil L10, a V-phase coil L11, and a W-phase coil L12 that are Y-connected. The three-phase AC motor M1 is provided with a rotation angle sensor S1 that detects a rotation angle in order to control energization to the stator coil L1. The motor control device 1 includes a three-phase inverter circuit 10 (multi-phase inverter), a battery 11 (first power source), a capacitor 12 (second power source), and a microcomputer 13 (control circuit).

  The three-phase inverter 10 is controlled by the microcomputer 13 to boost the DC voltage of the battery 11 and supply it to the capacitor 12 and converts the DC voltage smoothed by the capacitor 12 into a three-phase AC voltage (multi-phase AC voltage). In this way, the circuit is supplied to the three-phase AC motor M1. The three-phase inverter 10 includes MOSFETs 100 to 105 and current detection resistors 106 to 108 for detecting a phase current. The MOSFETs 100 and 103, the MOSFETs 101 and 104, and the MOSFETs 102 and 105 are connected in series. One ends of current detection resistors 106 to 108 are connected to the sources of the MOSFETs 103 to 105, respectively. The MOSFETs 100 and 103, the MOSFETs 101 and 104, and the MOSFETs 102 and 105 to which the current detection resistors 106 to 108 are connected are connected in parallel. A DC terminal T1 (the other DC terminal) is formed at the drains of the MOSFETs 100 to 102 connected in common. A DC terminal T2 (one DC terminal) is formed at the other end of the current detection resistors 106 to 108 connected in common. The DC terminals T1 and T2 are connected to the capacitor 12. AC terminals TU, TV, and TW are formed at series connection points of the MOSFETs 100 and 103, the MOSFETs 101 and 104, and the MOSFETs 102 and 105. AC terminals TU, TV, and TW are connected to U-phase coil L10, V-phase coil L11, and W-phase coil L12, respectively. Gates of MOSFETs 100 to 105 which are control terminals of the three-phase inverter 10 are connected to the microcomputer 13 via a drive circuit (not shown).

  The battery 11 is a device that supplies a DC voltage for driving the three-phase AC motor M1. The battery 11 is connected between the neutral point N of the stator coil L1 and the DC terminal T2 of the three-phase inverter 10. Specifically, the positive end of the battery 11 is connected to the neutral point N of the stator coil L1, and the negative end is connected to the DC end T2 of the three-phase inverter 12.

  The capacitor 12 is an element for smoothing the boosted DC voltage of the battery 11. The capacitor 12 is connected between the DC terminals T1 and T2 of the three-phase inverter 10. Specifically, one end of the capacitor 12 is connected to the DC terminal T1 of the three-phase inverter 10, and the other end is connected to the DC terminal T2 of the three-phase inverter 10.

  The microcomputer 13 controls the three-phase inverter 10, boosts the voltage of the battery 11 and supplies the boosted voltage to the capacitor 12, converts the DC voltage smoothed by the capacitor 12 into a three-phase AC voltage, and converts it into a three-phase AC motor M1. It is the circuit which supplies to. The microcomputer 13 controls the three-phase inverter 10 so as to flow through the three-phase AC motor M1 as a three-phase AC current (multi-phase AC current). The microcomputer 13 is connected to the gates of the MOSFETs 100 to 105 via a drive circuit (not shown) in order to control the three-phase inverter 10. Moreover, in order to detect a phase current, it connects to the end of the current detection resistors 106-108. In order to detect the voltage of the capacitor 12, it is connected to one end of the capacitor 12. In order to detect the rotation angle of the three-phase AC motor M1, the rotation angle sensor S1 is connected.

  Next, the configuration of the control block constituted by the microcomputer will be described with reference to FIGS. Here, FIG. 2 is a block diagram of a control block configured by a microcomputer. FIG. 3 is a circuit diagram of an equivalent circuit for explaining the voltage at the AC terminal. Specifically, FIG. 3A is an equivalent circuit related to the U phase when the MOSFET 100 is on and the MOSFET 103 is off. FIG. 3B is an equivalent circuit related to the U phase when the MOSFET 100 is turned off and the MOSFET 103 is turned on. In FIG. 3, R <b> 1 is the on-resistance of MOSFET 100. R2 is the on-resistance of the MOSFET 103. R 3 is a wiring resistance between the MOSFETs 100 and 103 and the capacitor 12. Rmotor is the resistance of the U-phase coil L10. Vdc is the voltage of the battery 11. Vc is the voltage of the capacitor 12. Vu is an induced voltage of the U-phase coil L10.

  As shown in FIG. 2, the microcomputer 13 includes, as control blocks, a current command calculation unit 130, a direct current calculation unit 131, an overcurrent prevention processing unit 132, a three-phase / two-phase conversion unit 133, and a controller. 134, a two-phase / three-phase converter 135, and a voltage / duty converter 136.

  The current command calculation unit 130 is a block that calculates a d-axis current command Id * and a q-axis current command Iq * for instructing a three-phase alternating current from a torque command T * input from the outside.

  The direct current calculation unit 131 is a direct current that flows from the battery B1 to the neutral point N of the stator coil L1 based on the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw detected by the current detection resistors 106 to 108. This is a block for calculating Idc. Specifically, the sum of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw becomes the DC current Idc that flows into the neutral point N of the stator coil L1.

  Based on the d-axis current command Id *, the q-axis current command Iq *, and the DC current Idc flowing into the neutral point N of the stator coil L1, the overcurrent prevention processing unit 132 controls the d-axis current to suppress the overcurrent. This block corrects at least one of the command Id * and the q-axis current command Iq * and calculates the d-axis current command Id ** and the q-axis current command Iq **.

  The three-phase / two-phase converter 133 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw detected by the current detection resistors 106 to 108 based on the rotation angle θ detected by the rotation angle sensor S1. , A d-axis current Id, and a q-axis current Iq.

  The controller 134 calculates the d-axis voltage command Vd * and the q-axis voltage command Vq * from the deviation between the d-axis current command Id **, the q-axis current command Iq **, and the d-axis current Id and the q-axis current Iq. It is a block to do.

  The two-phase / three-phase conversion unit 135 converts the d-axis voltage command Vd * and the q-axis voltage command Vq * into the U-phase voltage command Vu * and the V-phase voltage based on the rotation angle θ detected by the rotation angle sensor S1. This block converts the command Vv * and the W-phase voltage command Vw *.

  The voltage / duty conversion unit 136 converts the U-phase voltage command Vu *, the V-phase voltage command Vv *, and the W-phase voltage command Vw * into corresponding U-phase duty DutyU, V-phase duty DutyV, and W-phase duty DutyW. It is.

  Here, the voltage / duty conversion unit 136 will be described in detail with reference to FIGS. 1 and 3. In FIG. 1, when attention is paid to the MOSFETs 100 and 103 related to the U phase in the three-phase inverter 10, when the MOSFET 100 is turned on and the MOSFET 103 is turned off, the equivalent circuit shown in FIG. The equation holds.

On the other hand, when the MOSFET 100 is turned off and the MOSFET 103 is turned on, the equivalent circuit shown in FIG. 3B is obtained, and the circuit equation shown in Equation 2 is established.

  The voltage at the AC terminal TU is determined by the ratio of the period during which the MOSFET 100 is on and the MOSFET 103 is off and the period during which the MOSFET 100 is off and the MOSFET 103 is on. When the ratio of the MOSFET 100 is on and the MOSFET 103 is off, that is, when the duty is Duty (%), the ratio of the period when the MOSFET 100 is off and the MOSFET 103 is on is (100−Duty) (%). . Therefore, the voltage Vs of the AC terminal TU is as shown in Equation 3.

Therefore, the duty duty is as shown in Equation 4.

  The voltage / duty conversion unit 135 calculates the U-phase duty DutyU, the V-phase duty DutyV, and the W-phase duty DutyW based on Equation 4 as shown in Equation 5.

In Equation 5, the second term of each equation may be a fixed value. For example, as shown in Equation 6, a fixed value of 50 (%) may be used.

  The microcomputer 13 outputs a PWM signal for turning on and off the MOSFETs 100 to 105 based on the U-phase duty DutyU, the V-phase duty DutyV, and the W-phase duty DutyW.

  Next, the operation of the motor control device will be described with reference to FIG. 1, FIG. 2, and FIG. Here, FIG. 4 is an explanatory diagram for explaining the phase current of the three-phase AC motor.

  When torque command T * is input from the outside, current command calculation unit 130 shown in FIG. 2 calculates d-axis current command Id * and q-axis current command Iq * from torque command T *. Further, the direct current calculation unit 131 calculates a direct current Idc that flows into the neutral point N of the stator coil L1 from the detected phase currents Iu, Iv, and Iw.

  When the d-axis current command Id *, the q-axis current command Iq *, and the DC current Idc are calculated, the overcurrent prevention processing unit 132 is based on the d-axis current command Id *, the q-axis current command Iq *, and the DC current Idc. Then, at least one of the d-axis current command Id * and the q-axis current command Iq * is corrected, and the corrected d-axis current command Id ** and q-axis current command Iq ** are calculated. Further, the three-phase / two-phase converter 133 converts the phase currents Iu, Iv, Iw detected based on the rotation angle θ detected by the rotation angle sensor S1 into the d-axis current Id, the q-axis current Iq. .

When the d-axis current command Id **, the q-axis current command Iq **, the d-axis current Id, and the q-axis current Iq are calculated, the controller 134 controls the d-axis current command Id ** and the q-axis current command Iq *. The d-axis voltage command Vd * and the q-axis voltage command Vq * are calculated from * and the deviation between the d-axis current Id * and the q-axis current Iq *.
When the d-axis voltage command Vd * and the q-axis voltage command Vq * are calculated, the two-phase / three-phase conversion unit 135 determines the d-axis voltage command Vd *, based on the rotation angle θ detected by the rotation angle sensor S1. The q-axis voltage command Vq * is converted into a U-phase voltage command Vu *, a V-phase voltage command Vv *, and a W-phase voltage command Vw *. Further, the voltage / duty conversion unit 136 converts the U-phase voltage command Vu *, the V-phase voltage command Vv *, and the W-phase voltage command Vw * into the corresponding U-phase duty DutyU, V-phase duty DutyV, and W-phase duty DutyW. To do.

  The microcomputer 13 outputs a PWM signal for turning on and off the MOSFETs 100 to 105 based on the calculated U-phase duty DutyU, V-phase duty DutyV, and W-phase duty DutyW. MOSFETs 100 to 105 shown in FIG. 1 are turned on and off based on the PWM signal. Thus, the voltage of the battery 11 is boosted and supplied to the capacitor 12, and the DC voltage smoothed by the capacitor 12 is converted into a three-phase AC voltage and supplied to the three-phase AC motor M1. Accordingly, as shown in FIG. 4, the U-phase coil L10, the V-phase coil L11, and the W-phase coil L12 are supplied with a DC current Idc / 3 and a sine as a U-phase current Iu, a V-phase current Iv, and a W-phase current Iw. A combined current of wavy alternating current flows. Here, the direct current Idc / 3 is a current that flows when the voltage of the battery 11 is boosted and supplied to the capacitor 12. On the other hand, the AC current is a current that contributes to the torque generation of the three-phase AC motor M1. The three-phase AC motor M1 shown in FIG. 1 generates torque for assisting steering of the steering wheel corresponding to the torque command T *.

  Next, the operation of the overcurrent prevention process will be described with reference to FIGS. Here, FIG. 5 is a flowchart for explaining the operation of the overcurrent prevention processing unit.

  The overcurrent prevention processing unit 132 shown in FIG. 2 is based on the d-axis current command Id *, the q-axis current command Iq *, and the direct current Idc flowing into the neutral point N of the stator coil L1, as shown in FIG. The peak value Ipeak of the phase current is calculated. Further, a correction value Ilim_hosei is calculated based on the direct current Idc flowing into the neutral point N of the stator coil L1 (step S100). Then, it is determined whether or not the calculated peak value Ipeak of the phase current is larger than a preset overcurrent limit value Ipeak_limit (step S101).

  In step S101, when the peak value Ipeak of the phase current is equal to or less than the overcurrent limit value Ipeak_limit, no overcurrent is generated, so the overcurrent prevention processing unit 132 performs the d-axis current command Id *, the q-axis current command Iq *. Are output as d-axis current command Id ** and q-axis current command Iq ** (step S102).

  On the other hand, in step S101, when the peak value Ipeak of the phase current is larger than the limit value Ipeak_limit of the overcurrent, an overcurrent occurs. Therefore, the overcurrent prevention processing unit 132 sets the peak value Ipeak of the phase current to the correction value Ilim_hosei. It is determined whether or not the correction value of the d-axis current command calculated by correcting in step d is smaller than a preset limit value Id_limit of the d-axis current command (step S103).

  In step S103, when the correction value of the d-axis current command is smaller than the limit value Id_limit of the d-axis current command, the overcurrent prevention processing unit 132 sets the correction value to the d-axis current command Id ** and the q-axis current. Command Iq * is output as q-axis current command Iq ** (step S104).

  On the other hand, in step S103, when the correction value of the d-axis current command is equal to or greater than the limit value Id_limit of the d-axis current command, the overcurrent prevention processing unit 132 converts the peak value Ipeak of the phase current to the correction value Ilim_hosei, d-axis. It is determined whether or not the q-axis current command correction value calculated by correcting with the current command limit value Id_limit is smaller than a preset q-axis current command limit value Iq_limit (step S105).

  In step S105, when the correction value of the q-axis current command is smaller than the limit value Iq_limit of the q-axis current command, the overcurrent prevention processing unit 132 sets the limit value Id_limit of the d-axis current command as the d-axis current command Id **. At the same time, the correction value is output as the q-axis current command Iq ** (step S106).

  On the other hand, in step S105, when the correction value of the q-axis current command is equal to or greater than the limit value Iq_limit of the q-axis current command, the overcurrent prevention processing unit 132 sets the limit value Id_limit of the d-axis current command as the d-axis current command. In addition to Id **, the limit value Iq_limit of the q-axis current command is output as the q-axis current command Iq ** (step S107).

  That is, when the calculated peak value of the phase current exceeds the limit value, the overcurrent prevention processing unit 132 first decreases the d-axis current command to reduce the peak value of the phase current, and still does not exceed the limit value. If not, the q-axis current command is decreased. The overcurrent prevention processing unit 132 corrects the current command so that the phase current is equal to or less than the limit value.

  Finally, the effect will be described. According to the first embodiment, as shown in FIG. 4, a combined current of a direct current and an alternating current flows as a phase current in each phase of the three-phase AC motor M1. A DC current that is multiple times the number of DC currents forming the phase current flows from the battery B1 to the neutral point N of the Y-connected stator coil L1. Therefore, the direct current that forms the combined current can be known from the direct current that flows from the battery B1 to the neutral point N of the stator coil L1. Moreover, the alternating current which makes a phase current can be known from the d-axis current command and q-axis current command which instruct | indicate a three-phase alternating current. Therefore, based on the d-axis current command, the q-axis current command, and the direct current flowing into the neutral point N of the stator coil L1, the peak value of the phase current can be accurately calculated in consideration of the direct current. Then, by correcting the current command based on the calculated peak value of the phase current, the peak value of the actually flowing phase current can be surely made equal to or less than the limit value, and the steering of the three-phase inverter 10 and the steering wheel is assisted. Therefore, overcurrent can be prevented in the motor control device 1 that performs a boost operation using the three-phase AC motor M1 for the purpose.

  Further, according to the first embodiment, when the calculated peak value of the phase current exceeds the limit value, the overcurrent prevention processing unit 132 first decreases the d-axis current command to obtain the peak value of the phase current. If the value is reduced and still does not fall below the limit value, the q-axis current command is decreased. Therefore, it is possible to suppress a decrease in the q-axis current command that affects the output torque of the three-phase AC motor M1 as much as possible. Therefore, it is possible to prevent the overcurrent by suppressing the decrease in the output torque of the three-phase AC motor M1 as much as possible.

  In the first embodiment, an example is given in which the current command is corrected so that the phase current is equal to or less than the limit value. However, the present invention is not limited to this. For example, the current command may be corrected so that the phase current integrated value that is the time integrated value of the phase current is equal to or less than the limit value.

  In the first embodiment, the example in which the current command is corrected based on the direct current flowing into the neutral point N of the stator coil L1 is described, but the present invention is not limited to this. The current command may be corrected based on the direct current flowing out from the neutral point N of the stator coil L1.

(Second Embodiment)
Next, the motor control device of the second embodiment will be described. The motor control device of the second embodiment is such that the direct current forming the combined current flowing as the phase current has the third harmonic of the alternating current forming the combined current with respect to the motor control device of the first embodiment. Is.

  The configuration of the motor control device of the second embodiment is the same as the configuration of the motor control device of the first embodiment except for the control block. First, a control block constituted by a microcomputer, which is different from the motor control device of the first embodiment, will be described with reference to FIG. Here, FIG. 6 is a block diagram of a control block configured by the microcomputer according to the second embodiment.

  As shown in FIG. 6, the microcomputer 23 includes, as control blocks, a current command calculation unit 230, a DC current calculation unit 231, an overcurrent prevention processing unit 232, a three-phase / two-phase conversion unit 233, and a controller. 234, a two-phase / three-phase converter 235, a voltage / duty converter 236, and a controller 237. The current command calculation unit 230, the direct current calculation unit 231, the overcurrent prevention processing unit 232, the three-phase / two-phase conversion unit 233, the controller 234, and the two-phase / three-phase conversion unit 235 are the current command calculation in the first embodiment. Unit 130, DC current calculation unit 131, overcurrent prevention processing unit 132, three-phase / two-phase conversion unit 133, controller 134, and two-phase / three-phase conversion unit 135.

  The controller 237 is a block for calculating a correction value for the phase voltage command from the deviation between the input third harmonic current command Ksin3θ and the DC current Idc flowing into the neutral point N of the stator coil L1. Here, the third-order harmonic current command Ksin3θ is a command for instructing the third-order harmonic included in the direct current that forms the combined current that flows as the phase current. K designates the amplitude of the third harmonic, which may be a fixed value, based on the magnitude of the phase current, the difference between the peak value of the phase current and the limit value, and the rotational speed of the three-phase AC motor. It may be variable.

  The voltage / duty conversion unit 236 includes a U-phase voltage command Vu *, a V-phase voltage command Vv *, and a W-phase voltage command Vw * corrected by the correction value of the phase voltage command. Vv ** is a block that converts the W-phase voltage command Vw ** into the corresponding U-phase duty DutyU, V-phase duty DutyV, and W-phase duty DutyW.

  Next, with reference to FIGS. 6 and 7, the operation of the motor control device will be described focusing on a controller and a voltage / duty conversion unit that are different from the motor control device of the first embodiment. Here, FIG. 7 is an explanatory diagram for explaining the phase current of the three-phase AC motor.

  The controller 237 shown in FIG. 6 calculates a correction value for the phase voltage command from the deviation between the third harmonic current command Ksin3θ and the DC current Idc. Then, the U-phase voltage command Vu *, the V-phase voltage command Vv *, the W-phase voltage command Vw * and the correction value of the phase voltage command are respectively added and corrected, and the U-phase voltage command Vu ** and the V-phase voltage command Vv are corrected. **, W-phase voltage command Vw ** is calculated. The voltage / duty conversion unit 236 converts the U-phase voltage command Vu **, V-phase voltage command Vv **, and W-phase voltage command Vw ** to the corresponding U-phase duty DutyU, V-phase duty DutyV, and W-phase duty DutyW. Convert.

  In other words, the microcomputer 23 controls the third harmonic included in the DC current forming the phase current by controlling the phase voltage command based on the third harmonic current command Ksin3θ and the DC current Idc flowing into the stator coil.

  Thereby, like the motor control device 1 of the first embodiment, the voltage of the battery is boosted and supplied to the capacitor, and the DC voltage smoothed by the capacitor is converted into a three-phase AC voltage to be converted into a three-phase AC motor. Supplied. Accordingly, as shown in FIG. 7, a combined current of a direct current and a sinusoidal alternating current flows as the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw. Here, the average value of the direct current is Idc / 3, has a third harmonic of the alternating current, and the valley of the third harmonic coincides with the peak of the alternating current. As a result, the peak value of the phase current composed of the combined current of the direct current and the alternating current is reduced.

  Finally, the effect will be described. According to the second embodiment, as shown in FIG. 7, the peak value of the phase current can be reduced by the third harmonic of the alternating current forming the phase current that the direct current forming the phase current has. Therefore, overcurrent can be further suppressed.

  According to the second embodiment, the phase current can be controlled by controlling the phase voltage command. Therefore, by controlling the phase voltage command based on the third harmonic current command, the third harmonic included in the direct current that forms the phase current can be reliably controlled.

  According to the second embodiment, the DC current forming the phase current can be known from the DC current flowing into the neutral point of the stator coil. Therefore, by correcting based on the direct current flowing into the neutral point of the stator coil, the phase voltage command can be corrected in consideration of the direct current that forms the combined current. Therefore, it is possible to accurately control the third harmonic having a direct current that forms a combined current.

  In the second embodiment, the U-phase voltage command Vu *, the V-phase voltage command Vv *, and the W-phase voltage command Vw * are corrected so that the direct current forming the combined current has the third harmonic. Although an example is given, it is not limited to this. For example, by correcting the U-phase duty DutyU, the V-phase duty DutyV, and the W-phase duty DutyW, the direct current forming the combined current may have a third harmonic. In this case, the same effect can be obtained.

(Third embodiment)
Next, a motor control device according to a third embodiment will be described. When the detected phase current exceeds the overcurrent limit value when the three-phase AC motor is stationary with respect to the motor control device of the first embodiment, the motor control device of the third embodiment The detected rotation angle is corrected.

  The configuration of the motor control device of the third embodiment is the same as the configuration of the motor control device of the first embodiment except for the control block. First, a control block constituted by a microcomputer, which is different from the motor control device of the first embodiment, will be described with reference to FIG. Here, FIG. 8 is a block diagram of a control block configured by the microcomputer according to the third embodiment. Note that the current command calculation unit, overcurrent prevention processing unit, and voltage / duty conversion unit are omitted because they have the same configuration as the control block of the first embodiment.

  As shown in FIG. 8, the microcomputer 33 includes, as control blocks, a direct current calculation unit 331, a three-phase / two-phase conversion unit 333, a controller 334, a two-phase / three-phase conversion unit 335, and a phase current. A calculation unit 338 and a rotation angle correction value calculation unit 339 are provided. The direct current calculation unit 331 and the controller 334 have the same configuration as the direct current calculation unit 131 and the controller 134 in the first embodiment.

  The phase current calculation unit 338 is a block that calculates the phase current based on the d-axis current Id, the q-axis current Iq, and the DC current Idc that flows into the neutral point of the stator coil.

  The rotation angle correction value calculation unit 339 is a block that calculates a rotation angle correction value based on the phase current calculated by the phase current calculation unit 338. The rotation angle correction value calculation unit 339 determines the magnitude of the calculated phase current when the phase current calculated by the phase current calculation unit 338 exceeds the overcurrent limit value in a state where the three-phase AC motor is stationary. A rotation angle correction value θh corresponding to the height is calculated.

  Next, with reference to FIG. 8, the operation of the motor control device will be described focusing on the phase current calculation unit and the rotation angle correction value calculation unit that are different from the motor control device of the first embodiment.

  The phase current calculation unit 338 illustrated in FIG. 8 calculates the phase current from the d-axis current Id, the q-axis current Iq, and the DC current Idc. The rotation angle correction value calculation unit 339 is a rotation angle correction value corresponding to the magnitude of the phase current when the calculated phase current exceeds the overcurrent limit value in a state where the three-phase AC motor is stationary. θh is calculated. Specifically, the rotation angle correction value θh corresponding to the difference between the phase current value and the overcurrent limit value is calculated. A large correction value is calculated when the difference is large, and a small correction value is calculated when the difference is small. Then, the detected rotation angle θ and the rotation angle correction value θh are corrected by adding or subtracting to calculate the rotation angle θ ′. The 3-phase / 2-phase converter 333 and the 2-phase / 3-phase converter 335 perform predetermined conversion based on the rotation angle θ ′. The rotation angle correction value θh is set so as to be within a range that does not adversely affect the steering wheel steering.

  Finally, the effect will be described. According to the third embodiment, the phase current of the three-phase AC motor is determined by the rotation angle. Therefore, when the detected phase current exceeds the overcurrent limit value in a so-called locked state where the three-phase AC motor is stationary, the peak value of the phase current is suppressed by correcting the rotation angle θ. Can do.

  In the first to third embodiments, the positive terminal of the battery is connected to the neutral point N of the stator coil, the negative terminal is connected to the DC terminal T2 of the three-phase inverter, and one end of the capacitor is connected to the DC terminal T1 of the three-phase inverter. Although the example in which the other end is connected to the DC terminal T2 of the three-phase inverter is given, it is not limited to this. For example, as shown in FIG. 9, the positive end of the battery 11 ′ is connected to the DC end T2 of the three-phase inverter 10 ′, the negative end is connected to the neutral point N of the stator coil L1 ′, and one end of the capacitor 12 ′ is 3 The other end may be connected to the DC terminal T2 of the three-phase inverter 10 ′. As shown in FIG. 10, the positive end of the battery 11 'is connected to the neutral point N of the stator coil L1', the negative end is connected to the DC end T2 of the three-phase inverter 10 ', and one end of the capacitor 12' is 3 The DC inverter T ′ of the phase inverter 10 ′ may be connected to the neutral point N of the stator coil L1 ′ at the other end. Furthermore, as shown in FIG. 11, the positive end of the battery 11 ′ is at the DC end T2 of the three-phase inverter 10 ′, the negative end is at the neutral point N of the stator coil L1 ′, and one end of the capacitor 12 ′ is at the three-phase inverter. The other end may be connected to the neutral point N of the stator coil L1 ′.

  In the first to third embodiments, an example is given in which a current detection resistor is connected to the sources of the MOSFETs 103 to 105 to detect the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw. It is not limited. For example, as shown in FIG. 12, a current detection resistor may be connected to the drains of MOSFETs 100 'to 102' to detect the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw. Further, as shown in FIG. 13, current sensors 106 ″ to 108 ″ are provided between the AC terminals TU, TV, TW and the U-phase coil L10 ′, the V-phase coil L11 ′, and the W-phase coil L12 ′ to provide a U-phase. The current Iu, the V-phase current Iv, and the W-phase current Iw may be detected. Further, as shown in FIG. 14, current sensors 106 ″ and 107 ″ are provided between the AC terminals TU and TV and the U-phase coil L10 ′ and the V-phase coil L11 ′, and the negative electrode terminal and the AC terminal of the battery 11 ′ are provided. A current detection resistor 109 ″ may be connected during T2 to detect the U-phase current Iu, the V-phase current Iv, and the DC current Idc.

  Further, in the first to third embodiments, the motor control device includes a three-phase inverter and controls a three-phase AC motor. However, the present invention is not limited to this. The motor control device may include a multiphase inverter and control the multiphase motor. The same applies to this case.

  In addition, in the first to third embodiments, an example is given in which the three-phase coil is Y-connected, but the present invention is not limited to this. The multiphase coil may be star-connected. The same applies to this case.

1 to 3 ... Motor controller, 10, 10 '... 3 phase inverter (multi-phase inverter), 100 to 105, 100' to 105 '... MOSFET, 106 to 108, 106' to 108 ', 109 "... current detection resistor, 106" -108 "... current sensor, 11, 11 '... battery (first power supply), 12, 12' ... capacitor (second power supply), 13, 23, 33 ... microcomputer (control circuit), 130, 230 ... current command calculation unit, 131, 231, 331 ... DC current calculation unit, 132, 232 ... overcurrent prevention processing unit, 133 233, 333 ... 3-phase / 2-phase converter, 134, 234, 334 ... controller, 135, 235, 335 ... 2-phase / 3-phase converter, 136, 236 ... voltage / Duty conversion unit, 23 ... Controller, 338 ... Phase current calculator, 339 ... Rotation angle correction value calculator, M1 ... Three-phase AC motor (multi-phase motor), L1, L1 '... Stator coil, L10, L10 '... U phase coil, L11, L11' ... V phase coil, L12, L12 '... W phase coil, S1 ... rotation angle sensor

Claims (7)

A multiphase inverter connected to a multiphase motor having a star-connected stator coil and supplying a phase current to the multiphase motor;
A first power source connected between a neutral point of the stator coil and one DC terminal of the multiphase inverter;
A second power source connected between one DC end of the multiphase inverter or a neutral point of the stator coil and the other DC end of the multiphase inverter;
Connected to the control terminal of the multi-phase inverter, and controls the multi-phase inverter so that a multi-phase AC current flows through the multi-phase motor, thereby boosting the voltage of the first power source and supplying it to the second power source And a control circuit for converting the voltage of the second power supply into a multiphase AC voltage and supplying the same to the multiphase motor;
In a motor control device comprising:
The control circuit includes a d-axis current command and a q-axis current command that indicate a multiphase AC current, or a d-axis current and a q-axis current that form the multiphase AC current, and a DC that flows into a neutral point of the stator coil. Based on the current or the DC current that flows out from the neutral point of the stator coil, the phase current of the multiphase motor consisting of the combined current of the DC current and the AC current, or the phase current integrated value of the multiphase motor is A motor control device that corrects a current command so as to be equal to or less than a limit value.   When the phase current or the phase current integrated value exceeds the limit value, the control circuit first decreases the peak value of the phase current by decreasing the d-axis current command, and still does not exceed the limit value. 2. The motor control device according to claim 1, wherein the q-axis current command is decreased when it does not become.   3. The control circuit according to claim 1, wherein the control circuit controls the multi-phase inverter so that a direct current that forms the phase current has a third harmonic of an alternating current that forms the phase current. 4. The motor control device according to item 1.   The control circuit controls a phase voltage command or a phase duty calculated based on the d-axis current command and the q-axis current command based on a third harmonic current command, thereby forming a direct current that forms the phase current. The motor control apparatus according to claim 3, wherein the third harmonic of the current is controlled.   The control circuit controls the phase voltage command or the phase duty based on a direct current flowing into a neutral point of the stator coil or a direct current flowing out from a neutral point of the stator coil. The motor control device according to claim 4.   The control circuit controls the phase current based on a rotation angle of the multiphase motor, and detects when the detected phase current exceeds the limit value in a state where the multiphase motor is stationary. The motor control device according to claim 1, wherein the rotation angle of the multiphase motor is corrected according to the magnitude of the phase current.   The motor control device according to claim 1, wherein the multiphase motor is mounted on a vehicle and generates torque for assisting steering of a steering wheel.

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