JP3293435B2 - Motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor driving apparatus for driving a permanent magnet type brushless motor.

[0002]

2. Description of the Related Art As an apparatus for driving a motor by converting a DC voltage into an AC voltage, for example, Japanese Patent Application Laid-Open No. 6-10556.
An electric motor driving device described in Japanese Patent Publication No. 3 is known.

This motor drive device has a rectifier circuit, a booster circuit, an inverter, a motor control device, and a DC voltage feedback loop, and converts AC power supplied from an AC power supply into a variable voltage and a variable frequency. By converting the AC power and supplying the AC power to the motor, the motor (the three-phase induction motor) is configured to perform variable speed control in accordance with the speed command value.

In this case, the motor is driven not only by simply transforming the input voltage, but also by switching between the PAM control method and the PWM control method, taking advantage of both methods.

[0005] However, in the above-mentioned publication, although a method of switching between the PAM control method and the PWM control method during motor power running is described, drive control in the case of using a power regenerative brake with a motor, particularly power running and regenerative braking, is described. No mention is made of a switching method between the PAM control method and the PWM control method with the above.

Further, for example, in an actual electric vehicle (for example, an electric vehicle), it is desirable to control the torque generated by the motor. However, the motor is controlled by the magnitude relationship between the applied voltage and the back electromotive voltage generated by the motor. Since the current flows and generates torque, feedback control of the motor current is indispensable if the back electromotive voltage of the motor varies. Therefore, when the method of the electric motor driving device is used, two feedback loops of a DC voltage and a motor current are required, which causes a problem that a control circuit is complicated.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to perform powering and regeneration (four-quadrant operation) of a permanent magnet type brushless motor with a simple circuit configuration, and to provide a PAM control method and a PWM control method. It is an object of the present invention to provide a motor drive device that can efficiently drive a permanent magnet type brushless motor by switching the motors.

[0008] Such an object is achieved by the present invention described in the following (1) to (7).

(1) It has a chopper capable of stepping up and stepping down, an inverter, and a motor current sensor for detecting a current flowing in a driven permanent magnet type brushless motor, and switches between a PAM control method and a PWM control method. A motor drive device for driving a permanent magnet type brushless motor, comprising: a motor current command value that is a target value of a current flowing through the permanent magnet type brushless motor; and an AC output voltage based on a detection value from the motor current sensor. In the power running, either the PAM control method or the PWM control method is selected by comparing the AC output voltage value with a predetermined threshold value, and at least the PAM control method is executed in the regeneration. A motor driving device characterized in that the motor is driven by the motor.

(2) It has a chopper capable of stepping up and stepping down, an inverter, and a motor current sensor for detecting a current flowing in a driven permanent magnet type brushless motor, and switches between a PAM control method and a PWM control method. A motor drive device for driving a permanent magnet type brushless motor, comprising: a motor current command value that is a target value of a current flowing through the permanent magnet type brushless motor; and an AC output voltage based on a detection value from the motor current sensor. The motor drive is performed by selecting one of the PAM control method and the PWM control method in each of the power running and the regeneration by obtaining the AC output voltage value and comparing the AC output voltage value with a predetermined threshold value. Motor drive.

(3) For the AC output voltage value, PA
The motor drive device according to (1) or (2), wherein switching between the M control method and the PWM control method is performed continuously.

(4) Based on the AC output voltage value,
The motor drive device according to any one of (1) to (3), wherein the duty ratio of the chopper or the inverter is obtained, and the PAM control method or the PWM control method is executed at the duty ratio.

(5) The motor drive device according to any one of (1) to (4), further including a limiter circuit that limits an upper limit and a lower limit of the AC output voltage value.

(6) There is provided command means for issuing a command for powering or regeneration, and the limiter circuit sets the upper and lower limits of the AC output voltage value so as not to contradict the command for powering or regeneration from the command means. The motor drive according to the above (5), wherein the motor drive is restricted.

(7) The motor drive device according to any one of (1) to (6), wherein at least two threshold values are set.

[0016]

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a motor driving device according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing a configuration example of a motor driving device according to the present invention.

As shown in FIG.
By appropriately switching between the PAM control method and the PWM control method,
Permanent magnet type brushless motor (DC brushless motor)
, Especially a permanent magnet type brushless motor 2
This is a device for controlling the generated torque. Hereinafter, the “permanent magnet type brushless motor” is simply referred to as “brushless motor”.

The motor driving device 1 includes a brushless motor 2
A chopper (current reversible chopper) 5 capable of stepping up and down, a smoothing capacitor 6, an inverter 7, a control circuit (control means) 8 for controlling driving (operation) of the chopper 5 and the inverter 7, The sensor includes a motor current sensor 9 for detecting a current flowing in the brushless motor 2 and a rotor position sensor 11 provided in the brushless motor 2. In addition, the motor driving device 1
Is connected to a DC voltage source 3 as a power supply.

The control of the generated torque of the brushless motor 2 is performed by a control circuit 8 which controls the motor current value (detected value) detected by the current sensor 9.
And a signal from a rotor position sensor 11 provided in the brushless motor 2 to control the chopper 5 and the inverter 7 in accordance with a motor current command described later, thereby controlling the positive and negative generated torque of the brushless motor 2. Thus, the powering / regenerative operation (four-quadrant operation) of the brushless motor 2 is realized.

The chopper 5 includes, for example, the inductor 4 and
It comprises a first switching element 51 and a second switching element 52, and a first diode 53 and a second diode 54 provided for each switching element.

When the chopper 5 supplies power from the DC voltage source 3 to the inverter 7 and the brushless motor 2 side, that is, when the brushless motor 2 is operated by power, the voltage of the DC voltage source 3 is increased to increase the inverter. 7 Further, when power is supplied from the inverter 7 and the brushless motor 2 to the DC voltage source 3, that is, when the brushless motor performs regenerative operation (regenerative braking), the terminal voltage of the smoothing capacitor 6 on the inverter 7 side is reduced. Supply to DC voltage source 3.

FIG. 2 is a circuit diagram showing a configuration example of the inverter 7 of the motor drive device 1 shown in FIG.

As shown in the figure, the inverter 7 includes, for example, a first switching element 71, a second switching element 72, a third switching element 73, a fourth switching element 74, and a fifth switching element 75. And the sixth switching element 76, and the first diode 71a and the second diode 7 provided for each switching element.
2a, third diode 73a, fourth diode 74
a, fifth diode 75a and sixth diode 7
6a.

In this case, the connection point between the first switching element 71 and the second switching element 72 and the u-phase of the three-phase winding of the brushless motor 2 are connected, and the third switching element 73 and the third switching element 73 are connected to each other. No. 4 switching element 74 and the v-phase of the three-phase winding of the brushless motor 2 are connected, and the connection point of the fifth switching element 75 and the sixth switching element 76 and the brushless motor 2 The w-phase of the three-phase winding is connected.

The inverter 7 supplies a current to a predetermined phase determined by the rotor position information of the brushless motor 2 from the rotor position sensor 11, that is, a predetermined motor winding, so that the brushless motor 2 is powered and regenerated. Is controlled by

As each switching element of the chopper 5 and the inverter 7, for example, a bipolar transistor, a field effect transistor, a thyristor, or the like is used.

Hereinafter, the step-up operation and step-down operation of the chopper 5 will be described. In this case, the description will be made assuming that the voltage drop in each switching element and each diode can be ignored.

First, the boosting operation of the chopper 5 will be described. As shown in FIG. 1, when the second switching element (the lower-arm switching element) 52 is turned on, a circuit from the DC voltage source 3 via the inductor 4 is short-circuited, and a current flows through the inductor 4. At this time, the voltage applied to the DC voltage source 3 and the inductor 4 becomes almost zero. Next, when the second switching element 52 is turned off, the energy stored in the inductor 4 charges the smoothing capacitor 6 via the first diode (upper arm diode) 53. At this time, the voltage applied to the DC voltage source 3 and the inductor 4 becomes the terminal voltage of the smoothing capacitor 6. On above,
In the steady state in which the OFF operation is repeated, the inductor 4 repeats the operation of switching on and releasing the energy absorbed from the DC voltage source 3 to the smoothing capacitor 6 when switching off, and ignores the consumption of energy in the inductor 4 at this time. If possible, the average voltage applied to the inductor 4 is 0. As a result, the average voltage generated in the smoothing capacitor 6 is expressed by the following equation according to the duty ratio, which is the ratio of the ON time to one cycle of the second switching element 52. Equation (1) shown in FIG.

[0031]

(Equation 1)

When all the energy stored by the inductor 4 during the switch-on period is released during the switch-off period, that is, when the current becomes 0 during the switch-off period, the average of the inductor 4 Voltage is 0
And the relationship of the above equation (1) does not hold. More specifically, when the actual terminal voltage of the smoothing capacitor 6 is already higher than V _LINK obtained by substituting the voltage V _DC (input voltage) of the DC voltage source 3 and the duty ratio into the above equation (1). Corresponds to this. Even in such a case, since the input current becomes negative and the terminal voltage of the smoothing capacitor 6 does not decrease, and the energy hardly moves, it can be regarded as an operation stop state. By utilizing this feature, for example, by controlling the duty ratio to gradually increase from 0 at the start of operation, the operation can be started safely without directly reading the potentials on the input and output sides of the chopper 5. If the control is performed so that the duty ratio 0 is output when the operation is stopped, the operation can be stopped safely. As a further feature, due to the presence of the first diode 53, the terminal voltage of the smoothing capacitor 6 cannot be made lower than the voltage of the DC voltage source 3.

Next, the step-down operation of the chopper 5 will be described. First switching element (upper arm switching element)
By turning on 51, a current flows from the smoothing capacitor 6 to the DC voltage source 3 via the inductor 4.
At this time, the terminal voltage of the smoothing capacitor 6 is applied to the DC voltage source 3 and the inductor 4. Subsequently, when the first switching element 51 is turned off, the second diode (lower-arm diode) is obtained from the continuity of the current of the inductor 4.
As a result, the circulating current flows through the DC voltage source 3, the inductor 4, and the second diode 54. At this time, the voltage applied to the DC voltage source 3 and the inductor 4 becomes zero. In the steady state in which the ON and OFF operations are repeated, the inductor 4 repeats the operation of releasing the voltage (energy) absorbed during the switch-on period during the switch-off period. Assuming that the average voltage applied to the inductor 4 is 0 as in the case of the boosting operation described above, the average voltage applied to the DC voltage source 3 is a ratio of the ON time to one cycle of the first switching element 51 ( (duty) is determined as in the following equation (2).

[0034]

(Equation 2)

Just as in the case of the boosting operation, when the inductor 4 releases all the energy stored during the switch-on period during the switch-off period, that is, the current becomes zero during the switch-off period. In such a case, the average voltage of the inductor 4 does not become 0, and the relationship of the above equation (2) does not hold. Specifically, this corresponds to the case where the actual DC voltage is already higher than _VDC obtained by substituting the terminal voltage V _LINK of the smoothing capacitor 6 and the duty ratio duty into the above equation (2). Even in such a case, since the input current becomes positive and the DC voltage does not decrease, and the energy hardly moves, the operation can be regarded as an operation stop state. As in the case of the step-up operation, by utilizing this feature, for example, by controlling the duty ratio to gradually increase from 0 at the start of operation, it is safe to directly read the chopper input side and output side potentials. The operation can be started, and the operation can be safely stopped by controlling so that the duty ratio 0 is output when the operation is stopped.

Regarding the above-mentioned steady state of the step-up and step-down operations, the inductor 4 has a sufficient inductance to keep the current continuous for one cycle of switching, and the smoothing capacitor 6 also ignores the terminal voltage fluctuation for one cycle of switching. Each is set to have a sufficient capacity.

In the motor driving device 1, the first or second switching element 51 or 52 is operated at a predetermined time ratio to execute the step-down or step-up drive by the chopper 5, that is, the PAM control method. .

Next, the inverter 7 will be described with reference to FIGS.
Will be described. As described above, the inverter 7
It has a total of six switching elements 71 to 76, so that any phase of the three-phase winding of the brushless motor 2 can be arbitrarily connected to the positive terminal and the negative terminal of the smoothing capacitor 6. ing. Therefore, the polarity of the voltage applied to the three-phase winding of the brushless motor 2 can be freely selected. Actually, ON / OFF of each of the switching elements 71 to 76 is selected in consideration of the characteristics of the brushless motor 2. Hereinafter, such a combination of ON and OFF of each of the switching elements 71 to 76 of the inverter 7 is referred to as an energization pattern.

In the brushless motor 2, the phase of the AC back electromotive voltage generated by the motor is uniquely determined by the position of the rotor. Therefore, in the motor drive device 1, an optimal energization pattern is selected according to the rotor position detected by the rotor position sensor 11, and DC-AC conversion is performed.

As shown in FIG. 2, in order to actually flow the motor current, at least one of the first, third and fifth switching elements 71, 73 and 75 (each switching element of the upper arm) is required in power running. And one of the second, fourth, and sixth switching elements 72, 74, and 76 (each switching element of the lower arm) must be turned on to apply a voltage to the brushless motor 2. is there. While these two switching elements are on, one of the switching elements is PWM
Considering the control, the PWM-controlled switching element and the inductance component included in the motor winding cooperate to form a circuit equivalent to the chopper 5 described above.

In this case, from the terminal voltage of the smoothing capacitor 6, the chopper 5
, And from the back electromotive voltage generated in the brushless motor 2 to the terminal voltage of the smoothing capacitor 6, corresponds to the above-described step-up driving of the chopper 5. Further, since the back electromotive voltage generated in the brushless motor 2 by the diodes 71a to 76a of the inverter 7 is full-wave rectified, the terminal voltage of the smoothing capacitor 6 is changed from the motor back electromotive voltage as in the case of the chopper 5 described above. It cannot usually be lowered.

FIG. 3 is a block diagram showing a configuration example of the control circuit 8 of the motor driving device 1 shown in FIG.

As shown in the figure, the control circuit 8 comprises a PI controller 81, a pulse width converter 82, a current corrector 83, and a PWM mixer / distributor 84.

The selection of the switching element based on the rotor position signal from the rotor position sensor 11 and the energization pattern is performed by the PWM mixer / distributor 84. In this embodiment, this P
The energization patterns used by the WM mixer / distributor 84 are shown in Table 1 below.

[0045]

[Table 1]

As shown in Table 1, in the powering mode (drive mode) in which the brushless motor 2 generates a rotational force, each of the six normal rotor position signals of the rotor position sensor 11 follows a so-called 120 ° conduction pattern. On the other hand, a voltage is applied to the brushless motor 2 using the switching element of the upper arm indicated by “ON” in Table 1 and the switching element of the lower arm indicated by “PWM” in Table 1. And in the switching element of the lower arm,
The PWM signal (PWM control signal) is mixed, and thereby the step-down drive by the inverter 7, that is, the PWM control method is executed.

In the regenerative mode in which the brushless motor 2 generates a rotation stopping force, all the switching elements of the upper arm, that is, the switching elements 71, 73 and 75 are all turned off regardless of the rotor position signal from the rotor position sensor 11. , Each switching element of the lower arm,
That is, the switching elements 72, 74 and 76 all mix the PWM signals, thereby executing the boosting drive by the inverter 7, that is, the PWM control method. In the regenerative mode in which all phases of the u, v and w phases are short-circuited, the amount of energy stored in the inductance component of the motor winding is proportional to the back electromotive voltage of the brushless motor 2. Therefore, at the time of regeneration, a regenerative current is drawn out prior to a phase having a high back electromotive voltage. Therefore, it is not necessary to explicitly specify a driving phase in accordance with the phase of the back electromotive voltage of the brushless motor 2. Regeneration characteristics are obtained.

Next, an outline of the operation of the control circuit 8 will be described. In the present embodiment, the main purpose is to control the generated torque of the brushless motor 2, and the generated torque of the brushless motor 2 is proportional to the current value flowing through the brushless motor 2. Accept.

That is, the control circuit 8 of the motor driving device 1
Is connected to operating means (for example, an accelerator) not shown. When the operating means is operated, a motor current command is input from the operating means to the PI controller 81 accordingly. This motor current command indicates a target value of a current flowing through the brushless motor 2. In this case, when the motor current command is positive, it means a power running command, and when the motor current command is negative, it means a regenerative command. Therefore, the operation means constitutes command means for issuing a command for powering or regeneration.

As shown in FIG. 1, predetermined two phases of the three-phase winding of the brushless motor 2, ie, the u-phase and the w-phase,
A motor current sensor 9 is provided.

As shown in FIG. 3, the motor current sensor 9
Are respectively input to the current corrector 83. Further, a power running / regeneration mode signal indicating whether the power running mode or the regenerative mode is performed is input from the pulse width converter 82 to the current corrector 83. The method of generating the powering / regeneration mode signal will be described later.

The current corrector 83 generates a detected motor current based on the u-phase motor current and the w-phase motor current and the powering / regeneration mode signal, and the detected motor current is input to the PI controller 81. You. This detected motor current corresponds to the current flowing in the brushless motor 2.
The method of generating the detected motor current will be described later.

The PI controller 81 further receives a powering / regeneration mode signal from the pulse width converter 82,
The I controller 81 generates a command voltage (AC output voltage value) vc based on the powering / regeneration mode signal, the motor current command, and the detected motor current. The command voltage vc indicates a target value of the voltage applied to the brushless motor 2, that is, a target value of the voltage output from the inverter 7. In addition,
The method of generating the command voltage vc will be described later.

The command voltage vc is input from the PI controller 81 to the pulse width converter 82. The pulse width converter 82 generates a powering / regeneration mode signal based on the command voltage vc and sets the powering mode or the regeneration mode. In this case, the power running mode is set when the command voltage vc is positive, and the regenerative mode is set when the command voltage vc is negative. As described above, this powering / regeneration mode signal
The pulse width is input to the PI controller 81 and the current corrector 83 from the pulse width converter 82, and is also input to the PWM mixer / distributor 84 from the pulse width converter 82.

The pulse width converter 82 generates an inverter PWM signal, a chopper upper arm PWM signal, and a chopper lower arm PWM signal based on the command voltage vc. Regarding the operation of the pulse width converter 82 at this time,
Details will be described later.

The inverter PWM signal is input from the pulse width converter 82 to the PWM mixer / distributor 84. Also,
Chopper upper arm PWM signal and chopper lower arm P
The WM signal is input from the pulse width converter 82 to the chopper 5. The first switching element 5 of the chopper 5
1 operates at a predetermined time ratio based on the chopper upper arm PWM signal, and the second switching element 52 operates at a predetermined time ratio based on the chopper lower arm PWM signal.

In the PWM mixer / distributor 84, an inverter drive signal for controlling the operation of the inverter 7 based on the powering / regeneration mode signal, the inverter PWM signal, the rotor position signal, and the energization pattern shown in Table 1 above. Generate This inverter drive signal is supplied to the PWM mixer / distributor 8.
4 to the inverter 7. Note that the inverter 7
Each of the switching elements operates at a predetermined duty ratio based on the inverter drive signal.

Next, the aforementioned PI controller 81, pulse width converter 82 and current corrector 83 will be described in detail.

First, the current corrector 83 will be described. FIG.
Is a block diagram illustrating a configuration example of a current corrector 83.

As shown in the figure, the v-phase current calculator 831 of the current corrector 83 calculates the v-phase motor current from the u-phase motor current and the w-phase motor current detected by the motor current sensor 9. The calculated u-phase motor current, v-phase motor current, and w-phase motor current are converted into absolute motor current values by absolute value circuits 832, 833, and 834, respectively. Then, the motor current absolute value of each phase is input to the maximum value detector 835, and the maximum value detector 835 selects the maximum value of the three motor current absolute values. This maximum is
From the maximum value detector 835, an amplifier 836 having an amplification factor of 1
Is input to the amplifier 837 having an amplification factor of -1.

On the other hand, the changeover switch 838 switches between the amplifier 836 and the amplifier 837 based on the powering / regeneration mode signal. That is, in the powering mode, the changeover switch 838 switches to the amplifier 836 side, and in the regenerative mode, the changeover switch 838 switches to the amplifier 837 side.

Therefore, in the case of the power running mode, the maximum value from the maximum value detector 835 is output from the amplifier 836 as it is (with a positive value), and in the case of the regeneration mode, the maximum value from the maximum value detector 835 is output. The maximum value is multiplied by -1 (converted to a negative value) and output from the amplifier 836.

This maximum value is fed back as a detected motor current and used for torque control (current control) and the like. That is, as described above, the detected motor current from the current corrector 83 is input to the PI controller 81.

It should be noted that during power running, a method is adopted in which current flows through only any two of the three phases in accordance with the above-described 120 ° conduction pattern, and no phase is explicitly specified during regeneration. Uses the maximum value of the motor phase current in this way, so that there is no problem.

As described above, the direction of energy flow is uniquely determined depending on which one of the first and second switching elements 51 and 52 is PWM-driven. Therefore, it is not necessary to directly detect the polarity of the motor current, and based on information inside the control circuit 8 which of the first and second switching elements 51 and 52 is being driven, that is, based on the powering / regeneration mode signal. , The polarity of the motor current, which can be used as a feedback value for current control.

Next, the command voltage v in the PI controller 81
After briefly describing the method of generating the c, the pulse width converter 8
2 will be described.

FIG. 5 is a block diagram showing a configuration example of the PI controller 81, and FIG. 6 is a graph showing the relationship between the command voltage vc and the duty ratio for explaining the operation of the pulse width converter 82. .

As shown in FIG. 5, the value of the motor current command input to the PI controller 81 is compared in magnitude with the value of the detected motor current, and the difference value is processed as an error signal.
In this case, as in a general PI control method, the command voltage is obtained by adding a proportional component obtained by multiplying the error signal by a certain constant and an integral component obtained by multiplying the error integrated signal obtained by accumulating the error signal by a certain constant. Output as vc.

That is, the motor current command and the feedback detected motor current are respectively supplied to the PI controller 8.
The value obtained by subtracting the value of the detected motor current from the value of the motor current command is input to each of the integrator 812 and the amplifier 813 as an error signal.
The error signal input to the amplifier 813 is amplified by Kp times, and input to the adder 815 as a proportional component. on the other hand,
The error signal input to the integrator 812 is accumulated by the integrator 812, input to the amplifier 814 as an error integrated signal, and the error integrated signal input to the amplifier 814 is K
The signal is amplified by i times and input to the adder 815 as an integral component. In the adder 815, the proportional component and the integral component are added, and the added value is sent from the adder 815 to the limiter circuit 8
16 is input. In the limiter circuit 816, predetermined processing is performed, and the command voltage vc is output from the limiter circuit 816.
Is output. The other operations of the PI controller 81, such as the operation of the limiter circuit 816, will be described after the description of the pulse width converter 82.

Next, the pulse width converter 82 will be described.

The pulse width converter 82 compares the command voltage vc input from the PI controller 81 with a predetermined threshold value to be described later (power running in the PAM control system), (power running in the PWM control system), ( One of the following patterns is selected and executed: regeneration by the PAM control method and regeneration by the PWM control method.

In this case, as shown in FIG. 3, the pulse width converter 82 converts the command voltage vc into a chopper upper arm P for operating the first switching element 51 of the chopper 5.
The WM signal and the second switching element 52 of the chopper 5
Lower arm PWM signal for operating the inverter, and inverter PWM for operating the switching element of the inverter 7
The signals are converted into three PWM signals and output.

As described above, if the command voltage vc is positive, it indicates the power running mode, and if the command voltage vc is negative, it indicates the regenerative mode.
It determines whether c is positive or negative, and outputs a powering / regeneration mode signal.

The conversion method to each PWM signal used in this embodiment is as shown in the graph of FIG.
In this case, the horizontal axis of the graph is the command voltage vc input from the PI controller 81, and the vertical axis is the duty ratio of the switching element in the PAM and PWM control schemes, that is, the ratio of the ON time of the switching element to one cycle. It is. In the conversion method shown in FIG. 6, the voltage of the DC voltage source 3, that is, the assumed input voltage (the voltage immediately before the motor driving device 1) is VI, and the possible maximum value of the motor back electromotive voltage after full-wave rectification. That is, assuming that the assumed maximum generated voltage at the time of regeneration is VR, this is an example when VI = 48V and VR = 448V.

As shown in FIG. 6, this pulse width converter 8
2, “voltage 0” as the first threshold, “VI” as the second threshold, and “−VR +” as the third threshold.
VI ”, and compares these thresholds with the command voltage vc. When vc> VI, power running is performed by the PAM control method, when VI>vc> 0, power running is performed by the PWM control method, and when 0>vc> -VR + VI, the PAM control method is performed. Regeneration is performed at -VR + VI> v
In the case of c, regeneration is performed by the PWM control method.

From the command voltage vc used in this embodiment, each P
The conversion formula of the WM signal to the duty ratio duty is shown below in order. These equations use the relationship between the input and output voltages of the operation of the chopper 5 described above and calculate the duty ratio duty from the command voltage vc.
Is modified to calculate back.

A conversion formula (inverter PWM signal conversion formula) from the command voltage vc to the duty ratio of the inverter PWM signal is as shown in the following equation (3).

[0078]

[Equation 3]

From the command voltage vc, the chopper upper arm PWM
Conversion formula for duty ratio of signal (chopper upper arm P
The WM signal conversion equation is as shown in the following equation (4).

[0080]

(Equation 4)

From the command voltage vc, the chopper lower arm PWM
Conversion formula to signal duty ratio duty (chopper lower arm P
The WM signal conversion equation is as shown in the following equation (5).

[0082]

(Equation 5)

It should be noted that VR and VI in the above equations (3), (4) and (5) are respectively set to predetermined values in advance (for example, in this embodiment, VI = 48 V, VR = 4
48V).

The pulse width converter 82 has a memory and an operation unit (not shown).
Equations (5) to (5) are stored. Pulse width converter 82
Calculates (determines) each duty ratio duty by substituting the command voltage vc into the equations (3) to (5) in the arithmetic unit. Then, an inverter PWM signal, a chopper upper arm PWM signal, and a chopper lower arm PWM signal are generated and output based on the obtained duty ratios duty.

In the motor drive device 1, conversion into any PWM signal is performed uniquely for the command voltage vc. In this circuit, for example, switching between the power running mode and the regenerative mode, and the PAM control method and the PWM There is an advantage that it is not necessary to consider an internal state such as occurrence of hysteresis for switching with the control method.

More specifically, as shown in FIG. 6, the chopper upper arm PWM signal and the chopper lower arm PWM signal both have a duty ratio of 0 when the command voltage vc is in the range of 0 to 48 V, and the duty ratio is 0. As long as the voltage vc changes smoothly, changes in the operation mode of the chopper 5 (switching between the powering mode and the regeneration mode,
When switching between the PAM control method and the PWM control method), the first switching element 51 and the second switching element 52 are not switched at the same time, and a pause period for preventing a short circuit between the upper and lower arms is not required. .

Also, regarding the transition of the operation mode in the inverter 7, the command voltage vc in the regenerative mode is -400V.
The duty ratio is between 0 and 0, that is, as shown in Table 1, the duty ratio of the six switching elements is
Are all 0 (off). In this case, as long as the command voltage vc smoothly changes, the operation mode of the inverter 7 changes (switching between the powering mode and the regenerative mode, and between the PAM control method and the PWM control method). In this case, the idle period for preventing the short circuit of the upper and lower arms is not required in the same manner as described above.

That is, in the motor driving device 1, the switching between the powering mode and the regenerative mode and the switching between the PAM control system and the PWM control system are continuously performed for the command voltage vc. And the PWM control method are not executed simultaneously.

When there are a plurality of control objects such as the chopper 5 and the inverter 7, for example, if the operations of the chopper 5 and the inverter 7 are not synchronized, energy is accumulated in the smoothing capacitor 6 and an overvoltage state occurs. However, such a problem does not occur in the motor driving device 1 according to the present embodiment. The reason will be described below.

As described above, this pulse width converter 82
Operation always causes the chopper 5 and the inverter 7
One of them performs the torque control preferentially, and the other does not participate in the torque control. That is, “−VR + VI> v
In the range of “c> −VR” and the range of “VI>vc> 0”, the inverter 7 operates to perform step-up or step-down by the PWM control method. At this time, the chopper 5 is connected to the DC voltage source 3 and the brushless motor. 2 and just relay.
In addition, the range of “0>vc> −VR + VI” and “vc>
In the range of ">VI", the chopper 5 operates to perform the step-up or step-down by the PAM control method. At this time, the inverter 7 is only responsible for the conversion between DC and AC.

Further, as described above, since the switching between the two can be handled as continuous, it is easy to form a control loop.

In the expressions (3) to (5) and the above description, the domain is defined using an inequality sign.
Three threshold voltage values (three threshold values), VI, 0
And -VR + VI may belong to either region.

In this case, for example, when the command voltage value vc = 0, it may be included in any of the powering mode and the regeneration mode, but the six switching elements 71 to 76 of the inverter 7 are included.
Is preferably included in the regenerative mode, since all of them can be turned off.

As described above, in the driving method used in this embodiment, the powering mode and the regenerative mode depend on which of the first and second switching elements 51 and 52 of the chopper 5 performs switching. That is, the direction in which the energy flows is uniquely determined. That is, in the powering mode, even if the command voltage vc falls below the back electromotive voltage of the brushless motor 2, regeneration does not occur. Conversely, in the regenerative mode, the command voltage vc reduces the back electromotive voltage of the brushless motor 2. Even if it exceeds, no power running will occur.

Therefore, it is preferable to set the control circuit 8 so as to select the state of the command voltage vc = 0 as an initial value, whereby the back electromotive voltage depending on the presence or absence of rotation of the brushless motor 2 and the voltage of the smoothing capacitor 6 Regardless of the terminal voltage of the smoothing capacitor 6 due to the residual charge,
The brushless motor 2 can be started, operated, stopped, and the like.

Next, the description of the PI controller 81 will be continued with reference to FIG. Since the magnitude of the voltage (command voltage) that can be applied to the brushless motor 2 and the current that can flow through the brushless motor 2 are finite, the PI controller 81 includes a limiter circuit that limits the upper and lower limits of the command voltage vc. 816
Is provided. When the limiter circuit 816 operates, an integration stop signal is output from the limiter circuit 816 to the integrator 812, and the integrator 812 stops accumulating the error signal, thereby preventing accumulation of an inappropriate error signal.

A motor current command and a powering / regenerative mode signal are input to the limiter circuit 816, and the limiter circuit 816 changes the limit operation based on these signals. In this case, the limiter circuit 816 limits the upper and lower limits of the command voltage vc so as not to violate the powering or regeneration command from the operating means (commanding means).

FIG. 7 shows an input signal to the limiter circuit 816 (added value from the adder 815) and the limiter circuit 816.
6 is a graph showing a relationship with an output signal (command voltage vc).

If the motor current command is positive and a power running command and the current operation mode is already in the power running mode,
This corresponds to FIG. In this case, the limiter circuit 816 limits the upper limit of the command voltage vc to a predetermined value (400 V in this embodiment) and the lower limit to zero. By limiting the lower limit of the command voltage vc to 0 in the powering mode,
Even if the added value from the adder 815 becomes negative, the command voltage vc output from the limiter circuit 816 does not become negative, so that the command voltage vc is limited so as not to enter the regeneration mode.

When the motor current command is negative and the command is a regenerative command, and the current operation mode is already in the regenerative mode, this corresponds to FIG. 7B. In this case, the limiter circuit 816 limits the upper limit of the command voltage vc to 0 and limits the lower limit to a predetermined value (-448 V in this embodiment). By restricting the upper limit of the command voltage vc to 0 in the regenerative mode, even if the added value from the adder 815 becomes positive, the command voltage vc output from the limiter circuit 816 does not become positive, and enters the powering mode. Not to be restricted.

In cases other than the above, this corresponds to FIG. 7C, and the limiter circuit 816 limits the upper limit of the command voltage vc to a predetermined value (400 V in this embodiment) and sets the lower limit to a predetermined value (400 V). In this embodiment, it is limited to -448 V). In this case, transition of the mode between the powering mode and the regeneration mode is permitted.

The reason why a plurality of limiting operations are provided for the operation of the limiter circuit 816 will be described below.

FIG. 8 is a graph showing a current waveform of the brushless motor 2 at the time of no load in an energization pattern of 120 ° energization, and FIG.
5 is a graph showing a relationship between a detected motor current output from a current corrector 83 and a torque generated from a brushless motor 2.

When the brushless motor 2 is driven by a 120 ° conduction pattern, the current waveform of the brushless motor 2 becomes the waveform shown in FIG. 8 even when the brushless motor 2 is driven so that the torque becomes zero. Therefore, the detected motor current output from the current corrector 83 has the characteristics shown in FIG. 9 with respect to the torque generated by the brushless motor 2. This means that strictly speaking, it is impossible to follow a command torque equal to or less than this torque value (torque having a magnitude corresponding to the motor current command). For example, if you keep inputting the motor current command = 0,
In some cases, the errors may accumulate, and the command voltage vc may regenerate, that is, reach the negative maximum value.

However, by adding the limiter circuit 816 as described above, switching between the powering mode and the regenerative mode is not performed unless the powering or the regenerative mode is explicitly specified by the polarity of the motor current command. The problem of being unable to follow can be alleviated. Furthermore, since control is possible even if the relationship between the detected motor current and the motor-generated torque does not form a straight line passing through the origin, it is expected that the required accuracy of the detection circuit for detecting the motor current will be reduced and adjustment work will be omitted. it can.

Next, the operation of the motor driving device 1 will be briefly described.

During the execution of the PWM control method by the inverter 7, the same operation as that of the conventional motor control method is performed during both power running and regeneration.

In the PAM control system using the inverter 7 only for switching the phase of the brushless motor 2, the chopper 5
The electric power supplied in the step (b) causes the terminal voltage of the smoothing capacitor 6 to rise, so that a current flows into the brushless motor 2 by an amount corresponding to the voltage higher than the back electromotive voltage of the brushless motor 2, and the energy is converted by the brushless motor 2 to power the motor. Converted to torque output.

In the PAM control system, when the charge of the smoothing capacitor 6 is returned to the DC voltage source 3 by the chopper 5, the terminal voltage of the smoothing capacitor 6 is reduced by the returned power, and the reverse voltage of the brushless motor 2 is reduced. If the electromotive voltage exceeds the voltage of the smoothing capacitor 6, a current flows from the brushless motor 2, and this current causes the brushless motor 2 to generate a regenerative torque.

As described above, the motor driving device 1 does not require the feedback control of the DC voltage, and switches between the PAM control method and the PWM control method by the feedback control of only the motor current. Quadrant operation, that is, power running operation or regenerative operation can be performed.

In this case, the torque control of the brushless motor 2 can be performed with one feedback loop using only the motor current, and the circuit configuration of the control circuit 8 and the like can be simplified.

Further, there is no dead time when the mode is switched, and the switching between the PAM control method and the PWM control method and the switching between the power running and the regeneration can be continuously and smoothly performed.

The input voltage from the DC voltage source 3 can be converted into electric power by the chopper 5 and boosted to be applied to the brushless motor 2. In particular, it is possible to drive the brushless motor 2 by switching between the PAM control method and the PWM control method. In addition, the operating range of the brushless motor 2 can be expanded and the current loss can be reduced, and the degree of freedom in designing the brushless motor 2 is wide.

Further, since the input voltage from the DC voltage source 3 can be boosted and applied to the brushless motor 2, the voltage applied to the brushless motor 2 can be increased and the current can be reduced for a predetermined power. This contributes to the reduction in the diameter of the conductive wire and the diameter of the winding of the brushless motor 2, and the size of the brushless motor 2 can be reduced.

Further, since the input voltage from the DC voltage source 3 can be boosted and applied to the brushless motor 2, the DC voltage source 3 having a relatively low voltage can be used. Improvement can be achieved.

In the motor drive device 1, when only a rectifying circuit of the commercial power supply is prepared for installing a charging circuit for the DC voltage source (storage battery) 3 from the commercial power supply or the like, the smoothing capacitor 6 and the chopper 5 are respectively smoothed. It is also possible to use both as a capacitor and a charging current control circuit. For example, when charging the DC voltage source 3, a positive terminal of the rectifier circuit is connected to one end of the smoothing capacitor 6,
Connect the negative terminal of the rectifier circuit to the other end.

The motor driving device of the present invention can be applied to a motor driving device for driving a permanent magnet type brushless motor for various electric vehicles such as electric vehicles, electric scooters, forklifts and the like.

Although the motor driving device of the present invention has been described based on the illustrated configuration example, the present invention is not limited to this.

For example, in the present embodiment, the chopper capable of stepping up and stepping down is constituted by one chopper. However, in the present invention, for example, the chopper capable of stepping up and stepping down is replaced by a chopper dedicated to stepping up and a stepper dedicated to stepping down. And a chopper.

In the present invention, the inverter 7 is not limited to a voltage type inverter, but may be, for example, a current type inverter.

In the present invention, when the brushless motor 2 is regenerated, the PWM control method (−VR + VI>
vc> -VR) may be omitted.

[0122]

[0123]

As described above, according to the motor driving apparatus of the present invention, the PAM control method and the PWM control method are switched by the feedback control of only the current without the feedback control of the voltage, and the brushless control is performed. Driving of a motor, in particular, torque control of a brushless motor can be performed. For this reason, the number of feedback loops is small, and the circuit configuration of the control circuit and the like can be simplified.

Further, the power supply voltage can be boosted and applied to the brushless motor. In particular, since the brushless motor can be driven by switching between the PAM control method and the PWM control method, the operating range of the brushless motor is widened and the current loss is reduced. At the same time, the degree of freedom in designing a brushless motor is improved.

In addition, not only during power running but also during regeneration, at least the PAM control method is executed and the brushless motor is driven, so that the range in which the brushless motor can be safely driven is widened. In particular, since the brushless motor is driven by switching between the PAM control method and the PWM control method, the range in which the brushless motor can be safely operated is further expanded.

For example, when the motor drive device of the present invention is used for a drive device of a brushless motor of an electric vehicle such as an electric vehicle, an electric scooter, a forklift, etc., the degree of freedom in system design is increased.

Further, according to the motor driving device of the present invention,
Since either the PAM control method or the PWM control method is selected by comparing the AC output voltage value (command voltage vc) with a predetermined threshold value, dead time at the time of mode switching is not required, and PAM control is not performed. Switching between the PWM control method and the PWM control method can be continuously and smoothly performed.

A limiter circuit for limiting the lower limit and the upper limit of the AC output voltage value (command voltage vc), in particular, the lower limit and the upper limit of the AC output voltage value so as not to violate the powering or regeneration command from the command means. In the case where a limiter circuit for limiting the driving force is provided, the driving of the brushless motor can be more appropriately and reliably controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a motor drive device of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of an inverter of the motor drive device shown in FIG.

FIG. 3 is a block diagram illustrating a configuration example of a control circuit of the motor drive device illustrated in FIG. 1;

FIG. 4 is a block diagram illustrating a configuration example of a current corrector according to the present invention.

FIG. 5 is a block diagram illustrating a configuration example of a PI controller according to the present invention.

FIG. 6 is a graph showing a relationship between a command voltage vc and a duty ratio for explaining the operation of the pulse width converter according to the present invention.

FIG. 7 is a graph showing a relationship between an input signal (added value from an adder) to a limiter circuit and an output signal (command voltage vc) from the limiter circuit in the present invention.

FIG. 8 is a graph showing a current waveform of the brushless motor in a no-load state in a 120 ° conduction pattern according to the present invention.

FIG. 9 shows a detected motor current output from a current corrector in an energization pattern of 120 ° energization according to the present invention;
4 is a graph showing a relationship with a torque generated from a brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor drive device 2 Permanent magnet type brushless motor 3 DC voltage source 4 Inductor 5 Chopper 51 First switching element 52 Second switching element 53 First diode 54 Second diode 6 Smoothing capacitor 7 Inverter 71 First switching Element 72 Second switching element 73 Third switching element 74 Fourth switching element 75 Fifth switching element 76 Sixth switching element 71a First diode 72a Second diode 73a Third diode 74a Fourth Diode 75a Fifth diode 76a Sixth diode 8 Control circuit 81 PI controller 811 Subtractor 812 Integrator 813, 814 Amplifier 815 Adder 816 Limiter circuit 82 Pulse width converter 83 Current corrector 831 Phase current calculator 832 to 834 absolute value circuit 835 maximum value detectors 836 and 837 amplifier 838 change-over switch 84 PWM mixing and distributor 9 Motor current sensor 11 rotor position sensor

Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI H02P 6/02 371A (56) References JP-A-7-256147 (JP, A) JP-A-6-105563 (JP, A) JP-A Sho 59-198897 (JP, A) JP-A-59-207375 (JP, A) JP-A-7-256149 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/24 B60L 15/28 H02M 7/48 H02M 7/797 H02P 6/08

Claims (7)

(57) [Claims] 1. A power supply comprising a chopper capable of stepping up and stepping down, an inverter, and a motor current sensor for detecting a current flowing through a driven permanent magnet type brushless motor.
What is claimed is: 1. A motor drive device for driving a permanent magnet brushless motor by switching between an M control method and a PWM control method, comprising: a motor current command value that is a target value of a current flowing through the permanent magnet brushless motor; An AC output voltage value is obtained on the basis of the detected value from the above, and in power running, one of the PAM control method and the PWM control method is selected by comparing the AC output voltage value with a predetermined threshold value. In regeneration, at least PA
A motor drive device, wherein the motor drive is performed by executing an M control method. 2. A power supply system comprising: a chopper capable of stepping up and stepping down voltage; an inverter; and a motor current sensor for detecting a current flowing through a driven permanent magnet type brushless motor.
What is claimed is: 1. A motor drive device for driving a permanent magnet brushless motor by switching between an M control method and a PWM control method, comprising: a motor current command value that is a target value of a current flowing through the permanent magnet brushless motor; An AC output voltage value is obtained based on the detected value from the control unit, and the AC output voltage value is compared with a predetermined threshold value. In each of the power running and the regeneration, one of the PAM control method and the PWM control method is used. A motor drive device characterized in that a motor is selected and the motor is driven. 3. The motor drive device according to claim 1, wherein switching between the PAM control method and the PWM control method is continuously performed on the AC output voltage value. 4. The method according to claim 1, wherein a duty ratio of the chopper or the inverter is obtained based on the AC output voltage value, and the PAM control method or the PWM control method is executed based on the duty ratio. Motor drive. 5. The motor drive device according to claim 1, further comprising a limiter circuit that limits an upper limit and a lower limit of the AC output voltage value. 6. A commanding means for issuing a command for powering or regeneration, wherein the limiter circuit limits an upper limit and a lower limit of the AC output voltage value so as not to contradict a command for powering or regeneration from the commanding means. The motor drive device according to claim 5, wherein 7. The motor drive device according to claim 1, wherein at least two threshold values are set.