JPH09149685A - Motor drive - Google Patents

Abstract

(57) Abstract: A motor capable of performing power running and regeneration of a permanent magnet type brushless motor with a simple circuit configuration and capable of efficiently driving a motor by switching between a PAM control system and a PWM control system. A drive device is provided. A motor drive device (1) has a brushless motor (2), a chopper (5), a smoothing capacitor (6), an inverter (7), a control circuit (8), a motor current sensor (9) and a rotor position sensor (11), and a DC voltage source (3) on its input side. Are connected. The control circuit 8 generates a command voltage vc based on the detection value from the motor current sensor 9, and compares this vc with -VR + VI, voltages 0, VI. In the case of vc> VI, powering is performed by the PAM control method, and in the case of VI>vc> 0,
Powering is performed by the PWM control method, regeneration is performed by the PAM control method when 0>vc> -VR + VI, and regeneration is performed by the PWM control method when -VR + VI> vc.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

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

In this case, in addition to simply transforming the input voltage, the PAM control system and the PWM control system are switched to drive the motor by taking advantage of both systems.

However, although the above-mentioned publication describes the switching method between the PAM control method and the PWM control method during the power running of the motor, the drive control when the electric power regenerative brake is used in the motor, particularly the power running and the regenerative operation. No mention is made of a switching method between the PAM control method and the PWM control method including 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 has a magnitude relationship between the applied voltage and the back electromotive force generated by the motor. Since current flows to generate torque, feedback control of the motor current is indispensable when variations in the back electromotive force of the motor are expected. Therefore, when the method of the electric motor drive device is used, two feedback loops of the DC voltage and the motor current are required, which causes a problem that the control circuit becomes complicated.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to enable power running and regeneration (four quadrant operation) of a permanent magnet type brushless motor with a simple circuit configuration, and a PAM control system and a PWM control system. It is an object of the present invention to provide a motor drive device capable of efficiently driving a permanent magnet type brushless motor by switching between.

[0008]

This and other objects are achieved by the present invention which is defined below as (1) to (8).

(1) A motor drive device which has a chopper capable of stepping up and down, an inverter, and a current sensor, and drives a permanent magnet type brushless motor by switching between a PAM control system and a PWM control system. , An AC output voltage value is obtained based on a detection value from the current sensor, and in power running, by comparing the AC output voltage value with a predetermined threshold value, a PAM control method or a PW control method is performed.
Select either one of the M control methods, and during regeneration,
A motor drive device characterized in that at least a PAM control method is executed to drive a motor.

(2) A motor drive device which has a chopper capable of stepping up and down, an inverter, and a current sensor and drives a permanent magnet type brushless motor by switching between a PAM control system and a PWM control system. , An AC output voltage value is obtained based on a detection value from the current sensor, and the AC output voltage value is compared with a predetermined threshold value, so that PAM can be obtained in each of power running and regeneration.
A motor drive device, characterized in that either one of a control method and a PWM control method is selected to drive a motor.

(3) With respect to the AC output voltage value, PA
The motor drive device according to (1) or (2) above, which continuously switches between the M control method and the PWM control method.

(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) above, which has a limiter circuit for limiting the upper limit and the lower limit of the AC output voltage value.

(6) It has 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 violate the command for powering or regeneration from the commanding means. The motor drive device according to (5) above, which is restricted.

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

(8) The motor drive device according to any one of (1) to (7), wherein the current sensor is a motor current sensor that detects a current flowing through the permanent magnet type brushless motor.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The motor drive device of the present invention will be described in detail below with reference to the preferred embodiments shown in the accompanying drawings.

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

As shown in the figure, the motor drive device 1 is
Switching between the PAM control method and the PWM control method as appropriate,
Permanent magnet type brushless motor (DC brushless motor)
2 drive device, especially permanent magnet type brushless motor 2
Is a device for controlling the torque generated by the. Hereinafter, the "permanent magnet type brushless motor" is simply referred to as "brushless motor".

The motor drive device 1 includes a brushless motor 2
A chopper (current reversible chopper) 5 capable of stepping up and stepping down, a smoothing capacitor 6, an inverter 7, a control circuit (control means) 8 for controlling driving (operation) of the chopper 5, the inverter 7, etc., and a current. As a sensor, 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 are provided. In addition, the motor drive device 1
A DC voltage source 3 is connected to the input side of as a power source.

A control circuit 8 controls the torque generated by the brushless motor 2. The control circuit 8 controls the motor current value (detection value) detected by the current sensor 9.
And a signal from a rotor position sensor 11 provided in the brushless motor 2, the chopper 5 and the inverter 7 are controlled so as to follow a motor current command described later, and positive and negative generated torques of the brushless motor 2 are controlled. The powerless / regenerative operation (four-quadrant operation) of the brushless motor 2 is realized.

The chopper 5 includes, for example, an inductor 4 and
It is composed of a first switching element 51 and a second switching element 52, and a first diode 53 and a second diode 54 provided in each switching element.

The chopper 5 boosts the voltage of the DC voltage source 3 to supply the electric 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 in the power running mode. Supply to 7. Further, when power is supplied from the inverter 7 and the brushless motor 2 side to the DC voltage source 3, that is, when the brushless motor is regeneratively operated (regenerative braking), the terminal voltage of the smoothing capacitor 6 on the inverter 7 side is stepped down. Supply to the 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 a sixth switching element 76, and a first diode 71a and a second diode 7 provided in each switching element.
2a, third diode 73a, fourth diode 74
a, the fifth diode 75a and the 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. 4 is connected to the connecting point of the switching element 74 and the v phase of the three-phase winding of the brushless motor 2, and the connecting point of the fifth switching element 75 and the sixth switching element 76 is connected to the connecting point of the brushless motor 2. The w phase of the three-phase winding is connected.

This inverter 7 energizes 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, and drives the brushless motor 2 for power running and regenerative operation. Controlled by.

As the switching elements of the chopper 5 and the inverter 7, for example, bipolar transistors, field effect transistors, thyristors, etc. are used.

The step-up operation and step-down operation of the chopper 5 described above will be described below. In this case, it is assumed that the voltage drop in each switching element or each diode can be ignored.

First, the boosting operation of the chopper 5 will be described. As shown in FIG. 1, by turning on the second switching element (lower arm switching element) 52, the circuit from the DC voltage source 3 to 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 the above,
In a steady state in which the OFF operation is repeated, the inductor 4 is switched on and the energy absorbed from the DC voltage source 3 is switched off to be released to the smoothing capacitor 6, and the energy consumption of the inductor 4 is ignored. If possible, the average voltage applied to the inductor 4 is 0, and as a result, the average voltage generated in the smoothing capacitor 6 is expressed by the following number according to the duty ratio which is the ratio of the ON time to one cycle of the second switching element 52. It is determined by the equation (1) shown in 1.

[0031]

(Equation 1)

When all the energy stored in 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 is averaged. Voltage is 0
Therefore, the relation of the above formula (1) does not hold. 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 is not lowered, and the energy hardly moves, it can be considered that the operation is stopped. Using this feature, for example, by controlling the duty ratio to gradually increase from 0 at the start of operation, it is possible to safely start operation without directly reading the potentials on the input side and the output side of the chopper 5. Also, if the duty ratio is controlled to output 0 when the operation is stopped, the operation can be stopped safely. As a further feature, the presence of the first diode 53 prevents the terminal voltage of the smoothing capacitor 6 from being 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, current flows from the smoothing capacitor 6 through the inductor 4 toward the DC voltage source 3.
At this time, the terminal voltage of the smoothing capacitor 6 is applied to the DC voltage source 3 and the inductor 4. Then, when the first switching element 51 is turned off, the second diode (lower arm diode) is generated due to the continuity of the current of the inductor 4.
54 is turned on, and a 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 / off operation is 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 step-up operation described above, the average voltage applied to the DC voltage source 3 is the ratio of the on-time to one cycle of the first switching element 51. The duty is determined by the following equation (2).

[0034]

(Equation 2)

Just as in the boosting operation, when the inductor 4 releases all the energy accumulated during the switch-on period during the switch-off period, that is, the current becomes 0 during the switch-off period. In that 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 V _DC 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, the input current becomes positive, the movement of lowering the DC voltage is not exerted, and the energy hardly moves, so that it can be regarded as the operation stopped state. As in the case of the boost operation, if this characteristic is used, for example, when the duty is controlled so as to gradually increase from 0 at the start of operation, it is possible to safely read the potentials on the chopper input side and the output side directly. The operation can be started, and if the duty ratio is controlled to output 0 when the operation is stopped, the operation can be stopped safely.

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

In the motor drive device 1, the first or second switching elements 51, 52 are operated at a predetermined duty ratio to execute the step-down or step-up drive in 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, whereby 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, it is possible to freely select the polarity of the voltage applied to the three-phase winding of the brushless motor 2. In practice, the switching elements 71 to 76 are turned on or off in consideration of the characteristics of the brushless motor 2. Hereinafter, a combination of ON and OFF of each of the switching elements 71 to 76 of the inverter 7 will be referred to as an energization pattern.

In the brushless motor 2, the phase of the AC back electromotive force generated by the motor is uniquely determined by the position of the rotor. Therefore, in the motor drive device 1, an optimum 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 upper arm switching element) in power running. 1 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. With these two switching elements turned on, either one of the switching elements is PWM
Considering 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, for the brushless motor 2 from the terminal voltage of the smoothing capacitor 6, the chopper 5 described above is used.
The step-down driving of the chopper 5 corresponds to the back electromotive force generated in the brushless motor 2 to the terminal voltage of the smoothing capacitor 6. Further, since the back electromotive force voltage generated in the brushless motor 2 is full-wave rectified by the diodes 71a to 76a of the inverter 7, the terminal voltage of the smoothing capacitor 6 is changed from the motor back electromotive force 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 drive device 1 shown in FIG.

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

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

[0045]

[Table 1]

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

In the regenerative mode in which the rotation restraining force is generated in the brushless motor 2, all the switching elements of the upper arm, that is, the switching elements 71, 73 and 75 are 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, so that the step-up drive in the inverter 7, that is, the PWM control method is executed. In the regenerative mode in which all 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 force value of the brushless motor 2. Therefore, during regeneration, the regenerative current is drawn out preferentially over the phase with a high back electromotive force, and therefore it is sufficient to explicitly specify the drive phase in accordance with the phase of the back electromotive voltage of the brushless motor 2. Regenerative characteristics can be obtained.

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

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

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

As shown in FIG. 3, the motor current sensor 9
The u-phase motor current and the w-phase motor current detected by are respectively input to the current corrector 83. Further, the pulse width converter 82 inputs a power running / regenerative mode signal indicating the difference between the power running mode and the regenerative mode to the current corrector 83. The method of generating the power running / regeneration mode signal will be described later.

In the current corrector 83, a detected motor current is generated based on the u-phase motor current and w-phase motor current and the power running / regeneration mode signal, and this detected motor current is input to the PI controller 81. It 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 is further supplied with 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 power running / regeneration mode signal, the motor current command, and the detected motor current. The command voltage vc indicates the target value of the voltage applied to the brushless motor 2, that is, the 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 mentioned above, this powering / regenerative mode signal is
The pulse width converter 82 inputs the PI controller 81 and the current corrector 83, respectively, and the pulse width converter 82 also inputs the PWM mixer / distributor 84.

Further, 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 duty ratio based on the chopper upper arm PWM signal, and the second switching element 52 operates at a predetermined duty 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 power running / regeneration mode signal, the inverter PWM signal, the rotor position signal, and the energization pattern shown in Table 1 above. To generate. This inverter drive signal is used by the PWM mixer / distributor 8
Input from 4 to the inverter 7. Note that the inverter 7
Each of the switching elements is operated at a predetermined duty ratio based on the inverter drive signal.

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

First, the current corrector 83 will be described. FIG.
FIG. 8 is a block diagram showing a configuration example of a current corrector 83.

As shown in the figure, in the v-phase current calculator 831 of the current corrector 83, the v-phase motor current is calculated 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. 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
Are input to the amplifier 837 whose amplification factor is −1.

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

Therefore, in the power running mode, the maximum value from the maximum value detector 835 is output from the amplifier 836 as it is (while it remains a positive value), and in the regenerative mode, the maximum value detector 835 outputs it. 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 the detected motor current and used for torque control (current control) or the like. That is, as described above, the detected motor current from the current corrector 83 is input to the PI controller 81.

It is to be noted that, during power running, a method is basically adopted in which a current is allowed to flow through only two of the three phases according to the above-described energization pattern of 120 ° energization, and the phase is not explicitly specified during regeneration. Since a current similar to that at the time of power running flows through, there is no problem in using the maximum value of the motor phase current in this way.

Further, as described above with respect to the operation of the chopper 5, the energy flow direction is uniquely determined depending on which 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, but based on the information inside the control circuit 8 indicating which of the first and second switching elements 51 and 52 is being driven, that is, the power running / regeneration mode signal. , The polarity of the motor current can be determined and 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 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 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 constant, and an integral component obtained by multiplying the error integration signal by accumulating the error signals by a constant. It is output as vc.

That is, the motor current command and the detected motor current fed back are the PI controller 8 respectively.
The value obtained by subtracting the value of the detected motor current from the value of the motor current command is input as an error signal to each of the integrator 812 and the amplifier 813.
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 in the integrator 812 and is input to the amplifier 814 as an error integration signal. The error integration signal input to the amplifier 814 is K
It is amplified 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 added from the adder 815 to the limiter circuit 8
16 is input. The limiter circuit 816 performs a predetermined process, and the limiter circuit 816 outputs the command voltage vc.
Is output. Note that 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, which will be described later, (power running in the PAM control system), (power running in the PWM control system), ( Either one of PAM control system regeneration) and (PWM control system regeneration) is selected and executed.

In this case, as shown in FIG. 3, the pulse width converter 82 applies the command voltage vc to the 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
Chopper lower arm PWM signal for operating the inverter and inverter PWM for operating the switching element of the inverter 7
The signal is converted into three PWM signals and these are output.

Further, as described above, when the command voltage vc is positive, it represents the powering mode, and when it is negative, it represents the regenerative mode. Therefore, the pulse width converter 82 internally has the command voltage v.
It is determined whether c is positive or negative, and a powering / regeneration mode signal is output.

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 PAM, the duty ratio of the switching element in the PWM control method, that is, the ratio of the time when the switching element is on to one cycle. Is. In the conversion method shown in FIG. 6, the voltage of the DC voltage source 3, that is, the assumed input voltage (voltage immediately before the motor drive device 1) is VI, and the possible maximum value of the motor back electromotive force after full-wave rectification is obtained. In other words, this is an example when VI = 48V and VR = 448V, where VR is the maximum voltage generated during regeneration.

As shown in FIG. 6, this pulse width converter 8
2, the first threshold value is “voltage 0”, the second threshold value is “VI”, and the third threshold value is “−VR +”.
VI ”is used to compare these threshold values with the command voltage vc. When vc> VI, powering is performed by the PAM control method, when VI>vc> 0, powering 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 duty ratio of the WM signal 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 from the command voltage vc to the duty ratio duty.
It is modified to calculate back.

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

[0078]

(Equation 3)

From the command voltage vc to the chopper upper arm PWM
Conversion formula to signal duty ratio (chopper upper arm P
The WM signal conversion formula) is as shown in formula (4) below.

[0080]

(Equation 4)

Chopper lower arm PWM from command voltage vc
Conversion formula to signal duty ratio (chopper lower arm P
The WM signal conversion formula) is as shown in formula (5) below.

[0082]

(Equation 5)

Note that VR and VI in the equations (3), (4), and (5) are set to predetermined values in advance (for example, in this embodiment, VI = 48V, VR = 4).
48V).

The pulse width converter 82 has a memory and an arithmetic unit (not shown), and the memory has the above (3).
Expressions (5) are stored. Pulse width converter 82
In the calculation section, the command voltage vc is substituted into the expressions (3) to (5) to calculate (determine) each duty ratio. Then, an inverter PWM signal, a chopper upper arm PWM signal, and a chopper lower arm PWM signal are generated based on the obtained duty ratios, and these are output.

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

This will be described in more detail. 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 48V. As long as the voltage vc changes smoothly, changes in the operation mode of the chopper 5 (switching between the power running mode and the regenerative mode,
In switching between the PAM control method and the PWM control method), the first switching element 51 and the second switching element 52 do not switch at the same time, and a pause period for preventing a short circuit between the upper and lower arms is not required. .

Regarding the transition of the operation mode in the inverter 7, the command voltage vc in the regenerative mode is -400V.
Between 0 and 0, the duty ratio is 0, that is, as shown in Table 1, the duty ratio of the six switching elements is
Are all 0 (off), and in this case, as long as the command voltage vc changes smoothly, the operation mode of the inverter 7 is changed (switching between the power running mode and the regenerative mode, 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 drive device 1, the command voltage vc is continuously switched between the power running mode and the regenerative mode and the PAM control system and the PWM control system. And the PWM control method are not executed at the same time.

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

As described above, this pulse width converter 82
The operation of the chopper 5 and the inverter 7
One of them preferentially performs the torque control, 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 and the step-up or step-down is executed by the PWM control method. At this time, the chopper 5 includes the DC voltage source 3 and the brushless motor. It only relays 2 and.
In addition, the range of “0>vc> -VR + VI” and “vc
In the range of "VI", the chopper 5 operates to perform step-up or step-down by the PAM control method, and the inverter 7 only takes charge of conversion between direct current and alternating current.

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

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

In this case, for example, when the command voltage value vc = 0, it may be included in either the power running mode or the regenerative mode, but the six switching elements 71 to 76 of the inverter 7 are included.
Can be turned off, so it is preferable to include them in the regenerative mode.

As described above, in the drive system used in this embodiment, the power running mode and the regenerative mode are selected depending on which of the first and second switching elements 51 and 52 of the chopper 5 performs switching. That is, the direction of energy flow is uniquely determined. That is, in the power running mode, regeneration does not occur even if the command voltage vc is lower than the counter electromotive voltage of the brushless motor 2. On the contrary, in the regenerative mode, the command voltage vc is the counter electromotive voltage of the brushless motor 2. Even if it exceeds, powering will not 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 counter electromotive voltage depending on the rotation of the brushless motor 2 and the smoothing capacitor 6 are set. Safely, regardless of the magnitude 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 in the brushless motor 2 is finite, the PI controller 81 limits the upper limit and the lower limit of the command voltage vc to the limiter circuit. 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 the accumulation of error signals, which prevents inappropriate accumulation of error signals.

Further, the motor current command and the power running / regeneration mode signal are input to the limiter circuit 816, and the limiter circuit 816 is adapted to change the limit operation based on these signals. In this case, the limiter circuit 816 limits the upper limit and the lower limit of the command voltage vc so as not to violate the power running or regenerative command from the operating means (command means).

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

When the motor current command is positive and is a power running command, and the current operation mode is already in the power running mode,
This corresponds to (a) of 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 limits the lower limit to 0. 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 and is restricted so as not to enter the regeneration mode.

Further, when the motor current command is negative and the regeneration command and the current operation mode is already in the regeneration mode, it corresponds to (b) of FIG. 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 limiting 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 the power running mode is entered. Be restricted not to.

In other cases, 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 a predetermined value (c) of FIG. In this embodiment, it is limited to -448V). In this case, mode transition between the power running mode and the regenerative 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 the current waveform of the brushless motor 2 under no load in the energization pattern of 120 ° energization, and FIG. 9 is the energization pattern of 120 ° energization.
6 is a graph showing the relationship between the detected motor current output from the current corrector 83 and the torque generated from the brushless motor 2.

When the brushless motor 2 is driven by the energization pattern of 120 ° energization, the current waveform of the brushless motor 2 becomes the waveform shown in FIG. 8 even if 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 characteristic 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 (a torque having a magnitude corresponding to the motor current command) equal to or less than this torque value. For example, when the motor current command = 0 is continuously input,
In some cases, the error accumulates, and the command voltage vc may regenerate, that is, reach a negative maximum value.

However, by adding the limiter circuit 816 as described above, the power running mode and the regenerative mode are not switched unless the power running or the regenerative mode is explicitly specified by the polarity of the motor current command, and the command torque is changed. The problem of being unable to follow can be alleviated. Furthermore, control is possible even if the relationship between the detected motor current and the motor generated torque is not a straight line that passes through the origin in this way, so it is expected that the required accuracy of the detection circuit that detects the motor current will decrease and that adjustment work will be omitted. it can.

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

During execution of the PWM control system in the inverter 7, the operation is almost the same as the conventional motor control system both during power running and during regeneration.

In the PAM control system in which the inverter 7 is used only for phase switching of the brushless motor 2, the chopper 5
Since the electric power input at increases the terminal voltage of the smoothing capacitor 6, a current flows into the brushless motor 2 by an amount that is higher than the back electromotive force of the brushless motor 2, and energy is converted by the brushless motor 2 for power running. Converted to torque output.

In the PAM control method, if 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 amount of the returned power, and the reverse of the brushless motor 2 is reduced. When 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 drive device 1 does not need the feedback control of the DC voltage, and the feedback control of only the motor current is used to switch between the PAM control system and the PWM control system so that the brushless motor 2 can be driven by the four motors. 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 by one feedback loop of only the motor current, and thus the circuit configuration of the control circuit 8 and the like can be simplified.

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

Further, the input voltage from the DC voltage source 3 can be converted into electric power by the chopper 5, boosted and applied to the brushless motor 2. In particular, the PAM control system and the PWM control system are switched to drive the brushless motor 2. In addition, the operating range of the brushless motor 2 can be expanded and the current loss can be reduced, and the flexibility of the design of the brushless motor 2 is wide.

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 decreased with respect to a predetermined power. As a result, the diameter of the conductor wire and the winding diameter of the brushless motor 2 can be reduced, and the brushless motor 2 can be downsized.

Further, since the input voltage from the DC voltage source 3 can be boosted and applied to the brushless motor 2, it is possible to use the DC voltage source 3 having a relatively low voltage, which contributes to downsizing of the power source and safety. Can be improved.

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

The motor drive device of the present invention can be applied to a motor drive device for driving a permanent magnet type brushless motor of various electric vehicles such as an electric vehicle, an electric scooter and a forklift.

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

For example, in the above-described embodiment, the chopper capable of boosting and reducing the voltage is configured by one chopper. However, in the present invention, for example, the chopper capable of boosting and reducing the voltage is a chopper dedicated to boosting and a chopper dedicated to stepping down. It may be configured with a chopper.

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

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

Further, in the present embodiment, the motor current sensor 9 is used as the current sensor, but the present invention is not limited to this, and for example, a current sensor for detecting the input current to the inverter 7 is provided. The drive of the brushless motor 2 may be controlled based on the value detected by the current sensor.

[0123]

As described above, according to the motor drive device of the present invention, the feedback control of the voltage is not required, and the PAM control system and the PWM control system are switched by the feedback control of only the current, and the brushless system is used. It is possible to drive the motor, particularly to control the torque of the brushless motor. Therefore, 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, and in particular, the brushless motor can be driven by switching between the PAM control system and the PWM control system, so that 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 the brushless motor is improved.

Further, not only during power running but also during regeneration, at least the PAM control method is executed to drive the brushless motor, so that the range in which the brushless motor can be safely operated is expanded. In particular, since the brushless motor is driven by switching between the PAM control system and the PWM control system, 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 as a drive device for 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 expanded.

According to the motor drive device of the present invention,
Since the AC output voltage value (command voltage vc) is compared with a predetermined threshold value and either the PAM control method or the PWM control method is selected, no dead time is required at the time of mode switching, and PAM control is possible. It is possible to continuously and smoothly switch between the system and the PWM control system.

Further, 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 power running or regeneration command from the command means. When a limiter circuit for limiting the above is provided, the drive of the brushless motor can be controlled more appropriately and reliably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing 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.

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

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

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

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 in the present invention.

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

FIG. 8 is a graph showing a current waveform of the brushless motor in the energization pattern of 120 ° energization according to the present invention when no load is applied.

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

[Explanation of symbols]

 1 Motor Drive Device 2 Permanent Magnet 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. ⁶ Identification code Internal reference number FI technical display location H02P 6/02 371A

Claims (8)

[Claims] 1. A motor drive device that has a chopper capable of stepping up and down, an inverter, and a current sensor and drives a permanent magnet type brushless motor by switching between a PAM control system and a PWM control system. An AC output voltage value is obtained based on a detection value from the current sensor, and in 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. A motor drive device characterized by performing a PAM control method to drive a motor at least during regeneration. 2. A motor drive device having a chopper capable of stepping up and down, an inverter, and a current sensor and driving a permanent magnet type brushless motor by switching between a PAM control system and a PWM control system. An AC output voltage value is obtained based on the detected value from the current sensor, and this AC output voltage value is compared with a predetermined threshold value to obtain P in power running and regeneration.
A motor drive device characterized by selecting either an AM control system or a PWM control system to drive a motor. 3. The motor drive device according to claim 1, wherein the PAM control method and the PWM control method are continuously switched for the AC output voltage value. 4. The 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 at those duty ratios. 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 limiter circuit limits the upper limit and the lower limit of the AC output voltage value so as not to violate the powering or regeneration command from the commanding means. The motor drive device according to claim 5. 7. The motor drive device according to claim 1, wherein at least two threshold values are set. 8. The motor drive device according to claim 1, wherein the current sensor is a motor current sensor that detects a current flowing through the permanent magnet type brushless motor.