WO2019225373A1 - Motor drive device - Google Patents

Abstract

This motor drive device for sine wave driving a three-phase brushless motor is configured to find a phase current value of each of the phases with a single current sensor. The motor drive device for sine-wave driving a three-phase brushless motor comprises: an inverter that is connected to an electric power source via a bus and configured to convert DC electric power supplied from the electric power source via the bus into AC electric power and output the electric power to the brushless motor; one current sensor that detects the value of the bus current flowing in the bus; a phase current calculating unit that uses the bus current detected by the current sensor at a timing when the phase current of one of the phases among the three phases is at zero cross to calculate the phase current values of the other two phases; and a drive control unit that controls the inverter on the basis of the phase current values calculated by the phase current calculating unit.

Description

Motor drive device

The present invention relates to a motor drive device.

The following Patent Document 1 discloses a motor driving device that drives a three-phase brushless motor in a sine wave.

JP 2016-201111 A

By the way, in the above motor drive device, in order to detect the phase current value of each phase, the two-phase phase current value of the three phases is detected by two current sensors, and the two-phase detected by each current sensor is detected. It is necessary to calculate the phase current value of the remaining one phase from each phase current value using Kirchhoff's law. For this reason, at least two current sensors are required, resulting in high costs.

The present invention has been made in view of such circumstances, and an object thereof is a motor drive device for driving a three-phase brushless motor in a sine wave, and a phase current value of each phase is obtained by one current sensor. Be able to.

One aspect of the present invention is a motor drive device that drives a three-phase brushless motor in a sine wave, and is connected to a power supply device via a busbar, and the DC power supplied from the power supply device via the busbar is AC An inverter that converts electric power and outputs it to the brushless motor, a current sensor that detects a bus current value flowing through the bus, and the current sensor at a timing when a phase current of one of the three phases becomes zero cross A phase current calculation unit that calculates a current value of each of the other two phases from the bus current detected by the control unit, and a drive control unit that controls the inverter based on the phase current value calculated by the phase current calculation unit And a motor drive device characterized by comprising:

One aspect of the present invention is the above-described motor drive device, wherein the phase current calculation unit has a timing at which the electrical angle of the brushless motor is every 60 ° as a timing when the phase current value of the one phase becomes zero cross. The current values of the other two phases are calculated from the bus current value detected by the current sensor.

One aspect of the present invention is the motor drive device described above, wherein the drive control unit performs PWM control on the inverter based on the phase current value calculated by the phase current calculation unit, and the phase current calculation unit Is obtained by dividing the bus current value detected by the current sensor at the timing when the phase current value of the one phase becomes zero crossing by the duty ratio in the PWM control, so that each phase current of the other two phases Calculate the value.

As described above, according to the present invention, it is a motor driving device that drives a three-phase brushless motor in a sine wave, and the phase current value of each phase can be obtained by one current sensor.

It is a figure which shows an example of schematic structure of the motor system A which concerns on one Embodiment of this invention. It is a figure which shows the block diagram of the control part 8 which concerns on one Embodiment of this invention. It is a flowchart of operation | movement of the motor drive device 3 which concerns on one Embodiment of this invention. It is a figure which shows the waveform of the phase current of each phase which flows into the brushless motor 1 which concerns on one Embodiment of this invention. It is a figure which shows the effect of the motor drive device 3 which concerns on one Embodiment of this invention.

Hereinafter, a motor drive device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a schematic configuration of a motor system A according to an embodiment of the present invention. As shown in FIG. 1, the motor system A includes a brushless motor 1, a hall sensor 2, and a motor driving device 3.

The brushless motor 1 is a motor having a three-phase motor structure. The brushless motor 1 includes a stator around which a U-phase stator coil, a V-phase stator coil, and a W-phase stator coil, which are three-phase armature windings, and a permanent magnet rotor having a plurality of magnetic poles.

The hall sensor 2 is attached in the vicinity of the permanent magnet rotor of the brushless motor 1. The hall sensor 2 includes three U-phase hall sensors, a V-phase hall sensor, and a W-phase hall sensor that detect a magnetic flux change signal during operation of the brushless motor 1. The U-phase hall sensor detects the switching of the magnetic poles of the permanent magnet rotor, and outputs a U-phase hall sensor signal, which is a binary signal of High (H) or Low (L), to the motor driving device 3. The V-phase Hall sensor detects the switching of the magnetic poles of the permanent magnet rotor, and outputs a V-phase Hall sensor signal that is a binary signal of H or L to the motor drive device 3 as a result of the detection. The W-phase Hall sensor detects the switching of the magnetic poles of the permanent magnet rotor, and outputs a W-phase Hall sensor signal that is a binary signal of H or L to the motor driving device 3 as a result of the detection.

The motor drive device 3 is a device that drives the brushless motor 1 in a sine wave. This sine wave drive is a drive method in which the voltage applied to the stator coils (U-phase stator coil, V-phase stator coil, and W-phase stator coil) of the brushless motor 1 is changed into a sine wave, and is changed into a rectangular wave. Noise and vibration are lower than the rectangular wave drive.
Below, the structure of the motor drive device 3 which concerns on one Embodiment of this invention is demonstrated.

The motor drive device 3 includes a power supply device 4, an inverter 5, a current sensor 6, a gate driver 7, and a control unit 8.

The power supply device 4 can be a secondary battery such as a nickel metal hydride battery or a lithium ion battery. The power supply device 4 can also use an electric double layer capacitor (capacitor) instead of the secondary battery. The power supply device 4 is, for example, a battery provided in the vehicle.

The inverter 5 is connected to the power supply device 4 via the bus L. Inverter 5 converts DC power supplied from power supply device 4 via bus L to AC power and outputs the AC power to brushless motor 1.

More specifically, the inverter 5 includes a plurality of switching elements SW _UH to SW _WL (SW _UH , SW _UL , SW _VH , SW _VL , SW _WH , SW _WL ), and the plurality of switching elements SW _UH to SW _WL. SW _WL is PWM controlled to perform a switching operation, thereby converting a current supplied from power supply device 4 via bus L (hereinafter referred to as “bus current”) into a sinusoidal AC current. The inverter 5 supplies the converted sinusoidal alternating current as a phase current to each of the U-phase stator coil, the V-phase stator coil, and the W-phase stator coil. Thereby, the brushless motor 1 is driven. In the present embodiment, the case where the six switching elements SW _UH to SW _WL are n-channel FETs (Field Effective Transistors) will be described. However, the present invention is not limited to this, and for example, an IGBT (Insulated gate bipolar transistor). , And BJT (bipolar junction transistor).

Below, the specific structure of the inverter 5 is demonstrated.
The switching elements SW _UH and SW _UL connected in series, the switching elements SW _VH and SW _VL connected in series, and the switching elements SW _WH and SW _WL connected in series are a high potential ( Connected in parallel between the output) side and the ground potential.

The drain terminal of the switching element SW _UH is connected to the output terminal of the power supply device 4. The source terminal of the switching element SW _UL is connected to GND (ground). A connection point between the source terminal of the switching element SW _{UH and} the drain terminal of the switching element SW _UL is connected to one end of the U-phase stator coil.

The drain terminal of the switching element SW _VH is connected to the drain terminal of the switching element SW _UH . The source terminal of the switching element SW _VL is connected to GND (ground). And the source terminal of the switching element SW _VH, the connection point between the drain terminal of the switching element SW _VL is connected to one end of the V-phase stator coil.

The drain terminal of the switching element SW _WH is connected to the drain terminal of the switching element SW _UH . The source terminal of the switching element SW _WL is connected to GND (ground). And the source terminal of the switching element SW _WH, the connection point between the drain terminal of the switching element SW _WL is connected to one end of the W-phase stator coil.

Each switching element SW _UH to SW _WL has a gate terminal connected to the control unit 8. Furthermore, a free-wheeling diode is connected in parallel to each of the switching elements SW _UH to SW _WL .

The switching elements SW _UH to SW _WL are switched on and off based on a pulse width modulation signal (PWM signal) input from the control unit 8 via the gate driver 7.

Current sensor 6, a first current sensor provided in the bus L, the current value of the bus current flowing through the bus line L (hereinafter, referred to as "bus current value".) To detect the I _L. The current sensor 6 outputs the detected bus current value I _L to the control unit 8. The current sensor 6, it is sufficient detected bus current value I _L, it is not particularly limited to the detection method. For example, the current sensor 6 has a shunt resistor may be one of finding the bus current value I _L from the voltage across the shunt resistor. For example, the current sensor 6 may be a current transformer or a current transformer.

The gate driver 7 outputs the PWM signal having the duty ratio D output from the control unit 8 to the gate terminals of the switching elements SW _UH to SW _WL . As a result, the switching elements SW _UH to SW _WL are PWM-controlled with the duty ratio D.

Control unit 8 calculates a phase current value from the bus current value I _L from one current sensor 6, the phase current value so that the target value, PWM control of the switching elements SW UH _~ SW _WL.
Below, the structure of the control part 8 which concerns on one Embodiment of this invention is demonstrated using FIG.

As shown in FIG. 2, the control unit 8 includes an electrical angle calculation unit 9, a phase current calculation unit 10, and a drive control unit 11.

The electrical angle calculation unit 9 calculates the electrical angle θ of the brushless motor 1 at regular intervals based on the U-phase Hall sensor signal, the V-phase Hall sensor signal, and the W-phase Hall sensor signal. Then, the electrical angle calculation unit 9 outputs the calculated electrical angle θ to the phase current calculation unit 10.

The phase current calculation unit 10 calculates the phase current values of the other two phases from the bus current detected by the current sensor 6 at the timing when the phase current of one phase among the three phases becomes zero cross. For example, the timing when the phase current of one phase becomes zero crossing is the timing when the electrical angle θ of the brushless motor 1 is a multiple of 60 °.

Therefore, the phase current calculation unit 10 from the current sensor 6 electrical angle θ obtained from the electrical angle calculation unit 9 for each 60 ° acquires bus current value I _L, from the acquired bus current value I _L, the other Calculate the current value of each phase of two phases.

For example, the phase current calculation unit 10, when phase current of one phase is the timing at which the zero crossing, to the bus current I _L which is detected by the current sensor 6, is divided by the duty ratio D in the PWM control Thus, the current values of the other two phases are calculated.

The drive control unit 11 performs PWM control on the inverter 5 based on the phase current value calculated by the phase current calculation unit 10. For example, the drive control unit 11 calculates the duty ratio D such that the phase current value calculated by the phase current calculation unit 10 becomes a target value, and sends the PWM signal of the calculated duty ratio D via the gate driver 7. Output to the inverter 5. The inverter 5 supplies the voltage supplied to the stator coil of the brushless motor 1 in a sine wave shape based on the PWM signal.

Hereinafter, the operation of the motor drive device 3 according to the embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart of the operation of the motor drive device 3 according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a waveform of a phase current of each phase flowing through the brushless motor 1 according to the embodiment of the present invention.

The control part 8 determines whether it is a timing when the phase current of one phase among the three phases becomes zero cross. More specifically, the control unit 8 determines whether or not the current electrical angle θ is a multiple of 60 ° (step S101). Control unit 8, when the θ present electrical angle is determined to be a multiple of 60 ° as a timing when the phase current of one phase becomes zero crossing, to obtain a bus current value I _L from the current sensor 6 (Step S102). If the control unit 8 determines that the current electrical angle θ is not a multiple of 60 °, the control unit 8 repeats the process of step S101 until the electrical angle θ is a multiple of 60 °.

Control unit 8, the acquired bus current value I _L, is divided by the duty ratio D in the PWM control, and calculates the phase current values of the other two phases (step S103).

Here, a method for calculating the phase current value from the bus current value I _L in accordance with an embodiment of the present invention will be described with reference to FIG.

For example, as shown in FIG. 4, the timing at which the electrical angle θ = 60 ° or 240 ° is the timing at which the phase current of the W phase becomes zero cross. At this timing, no phase current flows in the W phase, and current flows only in the U phase and the V phase. More specifically, the phase current does not flow in the W-phase stator coil, and the phase current generated by the bus current flows only in the U-phase stator coil and the V-phase stator coil connected in series.

Therefore, when acquiring the bus current value I _L is the current sensor 6 at the timing when the electric angle theta = 60 ° or 240 °, the control unit 8 is divided by the duty D with respect to the bus current value I _L it is, it is possible to calculate the U-phase and the phase current value of the V phase (= bus current value I _L ÷ duty D). That is, the phase current value of the U-phase = V-phase phase current value = a (bus current value I _L ÷ duty D).

The timing at which the electrical angle θ = 120 ° or 300 ° is the timing at which the phase current of the V phase becomes zero cross. At this timing, no phase current flows in the V phase, and current flows only in the U phase and the W phase. More specifically, the phase current does not flow in the V-phase stator coil, and the phase current generated by the bus current flows only in the U-phase stator coil and the W-phase stator coil connected in series.

Therefore, when acquiring the bus current value I _L is the current sensor 6 at the timing when the electric angle theta = 120 ° or 300 °, the control unit 8 is divided by the duty D with respect to the bus current value I _L it is, it is possible to calculate the U-phase and W phase current value of the phase (= bus current value I _L ÷ duty D). That is, the phase current value of the U phase = the phase current value of the W phase = (bus current value I _L ÷ duty D).

Also, the timing when the electrical angle θ = 180 ° or 360 ° is the timing when the phase current of the U phase becomes zero cross. At this timing, no phase current flows in the U phase, and current flows only in the V phase and the W phase. More specifically, the phase current does not flow in the U-phase stator coil, and the phase current generated by the bus current flows only in the V-phase stator coil and the W-phase stator coil connected in series.

Therefore, when acquiring the bus current value I _L is the current sensor 6 at the timing when the electrical angle theta = 180 ° or 360 °, the control unit 8 is divided by the duty D with respect to the bus current value I _L it is, it is possible to calculate V-phase and the phase current value of the W phase (= bus current value I _L ÷ duty D). That is, the phase current value of the V phase = W phase of the phase current value = a (bus current value I _L ÷ duty D).

The drive control unit 11 performs PWM control on the inverter 5 based on the phase current value calculated by the phase current calculation unit 10 (step S104). For example, the drive control unit 11 calculates the duty ratio D such that the phase current value calculated by the phase current calculation unit 10 becomes a target value, and sends the PWM signal of the calculated duty ratio D via the gate driver 7. Output to the inverter 5. Thereby, the control unit 8 can drive the brushless motor 1 in a sine wave.

Hereinafter, the operation and effect of the motor drive device 3 according to the embodiment of the present invention will be described with reference to FIG.

FIG. 5A shows the phase current of each phase when the phase current of any of the three phases is not zero-crossed, for example, when the electrical angle θ is 90 °. FIG. In this case, since the U-phase, the phase current flows through the three-phase V-phase and W-phase, the bus current value I _L can not be calculated the phase current value of each phase.

FIG. 5B shows the phase current of each phase when the phase current of any one of the three phases becomes zero crossing, for example, when the electrical angle θ is 120 °. FIG. In this case, since only the phase current flows through the U-phase and W-phase, it is possible to calculate the phase current value of each phase on the bus current value I _L.

Thus, the apparatus 3 according to an embodiment of the present invention, among the three phases, the bus current value I _L obtained at the timing when the phase current of one phase becomes zero crossing, the phase currents of the other two phases Is calculated.

According to such a configuration, in the motor driving apparatus that drives the three-phase brushless motor 1 in a sine wave, the phase current of each phase can be obtained by the single current sensor 6.

The control unit 8, as the timing at which the phase current of one phase becomes zero crossing, to obtain detected bus current value I _L by the current sensor 6 at the timing of the electrical angle of the brushless motor every 60 degrees, and the obtained the bus current value I _L, may be calculated phase currents of the other two phases.

The control unit 8, for the detected bus current value I _L by the current sensor 6 at the timing when the phase current of one phase becomes zero crossing is divided by the duty ratio D in the PWM control, the other two phases Each phase current may be calculated.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within the scope not departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Brushless motor 3 Motor drive device 4 Power supply device 5 Inverter 6 Current sensor 7 Gate driver 8 Control part 9 Electrical angle calculation part 10 Phase current calculation part 11 Drive control part

Claims (3)

A motor drive device for driving a three-phase brushless motor with a sine wave,
An inverter connected to a power supply device via a bus, and converting the DC power supplied from the power supply device via the bus to AC power and outputting the AC power to the brushless motor;
One current sensor for detecting a bus current value flowing through the bus;
Of the three phases, a phase current calculation unit that calculates each phase current value of the other two phases from the bus current detected by the current sensor at the timing when the phase current of one phase becomes zero crossing;
A drive control unit that controls the inverter based on the phase current value calculated by the phase current calculation unit;
A motor drive device comprising: The phase current calculation unit calculates the other two-phase from the bus current value detected by the current sensor when the electrical angle of the brushless motor is every 60 ° as the timing when the phase current value of the one phase becomes zero cross. The motor drive device according to claim 1, wherein each phase current value is calculated. The drive control unit performs PWM control on the inverter based on the phase current value calculated by the phase current calculation unit,
The phase current calculation unit divides the bus current value detected by the current sensor at the timing when the phase current value of the one phase becomes zero crossing by a duty ratio in the PWM control, thereby obtaining another two The motor driving device according to claim 1, wherein each phase current value of the phase is calculated.

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