JPH1189270A - Driver for motor, and electric motorcar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the responsiveness of control approximately constant even if battery voltage changes, and get specified motor property. SOLUTION: A chopper circuit 15 is interposed between a battery 14 and an inverter circuit 16. A motor 11 is driven by the inverter circuit 16. A battery voltage detecting circuit 32 is connected to the battery 14, and this driver is provided with an inverter circuit input voltage detecting circuit 33 on the input side of the inverter circuit 16. A control circuit 34 sets the loop gain of feedback control according to the battery voltage Vbat, and correts the loop gain so that the step-up chopper duty ratio and the inverter circuit input voltage Vdc may be in proportional relation, according to the ratio of the battery voltage Vbat to the inverter circuit input voltage Vdc at the time of boosting.

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 and an electric vehicle which convert DC power of a battery into AC power by a drive circuit and supply the AC power to the motor.

[0002]

FIG. 8 shows a conventional example of a driving device for driving a motor of an electric vehicle. The DC buses 2 and 3 are connected to the positive and negative terminals of the battery 1, and the DC buses 2 and 3 are driven by bridging six transistors 4U to 4W and 5U to 5W. The circuit 6 is connected, and the output terminal of the drive circuit 6 is connected to the input terminal of the motor 7.
In this case, the DC voltage of the battery 1 is directly
, The output (rotational speed) of the motor 7 is controlled by
This is executed by performing PWM control on the drive circuit 6.

The battery 1 is made of, for example, a lead storage battery, and has a characteristic that a voltage drop increases in accordance with a discharge current. For this reason, when a large output is required for the motor 7 as in starting acceleration, the current increases and the voltage drop of the battery 1 also increases. In addition, there is a large difference in the voltage of the battery 1 immediately after charging and at the end of discharging. As described above, the following problem arises due to the change in the voltage of the battery 1.

The output of the motor 7 is controlled by driving the drive circuit 6 with PW
Since the control is performed by controlling the voltage applied to the motor 7 by controlling the M, the responsiveness also changes when the battery voltage changes. That is, the responsiveness differs between the initial stage of acceleration and the end stage of acceleration, and between the initial stage of charge and the end stage of discharge. In particular, during start acceleration, the voltage drop is large and the acceleration time becomes long. Therefore, the loop gain is raised to increase the response. However, if the loop gain is too high, the control becomes unstable.

Further, when the motor 7 is designed based on the rated voltage of the battery 1, predetermined motor characteristics cannot be obtained at the end of discharging. However, if the motor 7 is designed based on the voltage at the end of battery discharge, the size of the motor 7 increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor driving apparatus capable of making control responsiveness substantially constant even when a battery voltage fluctuates and obtaining predetermined motor characteristics. And electric vehicles.

[0007]

According to a first aspect of the present invention, there is provided a motor driving device including at least one arm formed by connecting two switching elements having a flywheel diode in series, and an input terminal connected to a battery. An output terminal connected to the motor, a drive circuit for controlling the energization of the motor by turning on and off the switching element, feedback control means for feedback controlling the motor, a switching element and a flywheel connected in parallel to the drive circuit. A chopper circuit having a wheel diode, a reactor connected between a connection point between a switching element and a flywheel diode in the chopper circuit and the battery, and a chopper control for causing the chopper circuit to perform a boosting operation when necessary. Means for detecting the terminal voltage of the battery. Re-voltage detecting means, loop gain setting means for setting a loop gain for feedback control during non-boosting according to the battery terminal voltage detected by the battery voltage detecting means, and drive for detecting the drive circuit input voltage Circuit input voltage detection means, and a loop gain for feedback control according to a battery terminal voltage detected by the battery voltage detection means at the time of boosting by the chopper circuit and a drive circuit input voltage detected by the drive circuit input voltage detection means. And a loop gain correction means for correcting

In the motor driving device according to the first aspect of the present invention, a predetermined motor characteristic can be obtained even if the battery voltage is reduced by interposing the boost chopper circuit between the battery and the driving circuit. Also, since the loop gain of the feedback control is changed according to the battery voltage,
Even if the battery voltage changes, the response of the feedback control becomes constant. Further, at the time of boosting by the chopper circuit, the loop gain of the feedback control is corrected according to the battery terminal voltage and the drive circuit input voltage, so that stable control can be performed even during the chopper control.

According to a second aspect of the present invention, the loop gain correction means is responsive to a ratio between a battery terminal voltage detected by the battery voltage detection means and a drive circuit input voltage detected by the drive circuit input voltage detection means. This is characterized in that the loop gain of the feedback control is set by the feedback control. In this configuration, when boosting by the chopper circuit, the loop gain of the feedback control is set according to the ratio between the battery terminal voltage and the drive circuit input voltage, so that the feedback control is further stabilized even during the chopper control.

According to a third aspect of the present invention, there is provided a motor driving device having at least one arm in which two switching elements each having a flywheel diode are connected in series, an input terminal is connected to a battery, and an output terminal is connected to the motor. A drive circuit that is connected and controls the energization of the motor by turning on and off the switching element; a feedback control unit that performs feedback control of the motor; and a switching element and a flywheel diode connected in parallel to the drive circuit. A chopper circuit, a reactor connected between a connection point of the switching element and the flywheel diode in the chopper circuit and the battery,
Chopper control means for causing the chopper circuit to perform a boost operation when necessary; battery voltage detection means for detecting a terminal voltage of the battery; and non-boosting operation in accordance with the battery terminal voltage detected by the battery voltage detection means. Loop gain setting means for setting a loop gain for feedback control, and step-up chopper duty ratio setting means for setting a step-up chopper duty ratio so that the relationship between the control amount calculated by the feedback control means and the motor applied voltage is proportional. And is provided.

In the motor driving device according to the third aspect, since the boost chopper circuit is interposed between the battery and the driving circuit, predetermined motor characteristics can be obtained even when the battery voltage decreases. Also, since the loop gain of the feedback control is changed according to the battery voltage,
Even if the battery voltage changes, the response of the feedback control becomes constant. Furthermore, the boost chopper duty ratio is set so that the relationship between the control amount calculated by the feedback control means and the motor applied voltage becomes proportional when the voltage is boosted by the chopper circuit, so that stable control can be performed even during the chopper control. .

According to a fourth aspect of the present invention, the chopper circuit is configured such that a parallel circuit of a switching element and a flywheel diode is connected in series, so that both the step-up and the step-down are performed. However, when supplying motor drive power to the drive circuit and boosting is necessary, the chopper circuit can function as a booster chopper,
It is characterized in that the two switching elements are turned on and off so that the two switching elements can function as a step-down chopper during regeneration of the motor. In this configuration, an effect is obtained that a large regenerative current does not flow to the battery side.

According to a fifth aspect of the present invention, there is provided an electric vehicle equipped with the motor driving device according to the first or third aspect. As a result, a stable motor can be achieved and stable running can be achieved even when the voltage of the battery fluctuates.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to an electric vehicle will be described below with reference to FIGS. In FIG. 1 showing the entire configuration, an electric vehicle is provided with a brushless motor 11 as a running motor, which is a stator 12 having a plurality of phases, for example, three-phase stator coils 12U, 12V and 12W.
, A rotor (not shown) and a position detector 13. The electric vehicle is equipped with a rechargeable battery 14 made of a lead storage battery.
4 is supplied to an inverter circuit 16 as a drive circuit via a chopper circuit 15 constituting a step-up chopper circuit and a step-down chopper circuit. The inverter circuit 16 converts the DC power into an AC power and supplies the AC power to the brushless motor 11. It is being supplied.

The inverter circuit 16 includes NPN transistors 17U and 17 serving as six switching elements.
V, 17W and 18U, 18V, 18W are connected by a three-phase bridge, and flywheel diodes 19U, 19V, 1
9W and 20U, 20V, 20W are connected.
It has two arms 21U, 21V and 21W. The input terminals 22a, 22b of the inverter circuit 16
Is a DC bus 24 having a capacitor 23 connected between the wires,
25, output terminals 26U, 26V and 26W
Are the stator coils 12U, 1 of the brushless motor 11;
It is connected to each terminal of 2V and 12W. The other terminals of the stator coils 12U, 12V and 12W are commonly connected.

The chopper circuit 15 is configured by connecting transistors 27 and 28 as switching elements in series, and flywheel diodes 29 and 30 are connected between the respective collectors and emitters. The collector of transistor 27 is connected to DC bus 24, the emitter is connected to the collector of transistor 28, and connected to the positive terminal of battery 14 via reactor 31. The emitter of the transistor 28 is connected to the DC bus 25 and the negative terminal of the battery 14.

A battery voltage detector 32 as a battery voltage detecting means is connected between the positive and negative terminals of the battery 14, and detects the terminal voltage of the battery 14. Further, the inverter circuit input voltage detector 33 as the drive circuit input voltage detection means includes the DC buses 24 and 25.
To detect the inverter circuit input voltage.

The control circuit 34, which is a feedback control unit, a chopper control unit, a loop gain setting unit, and a loop gain correction unit, is mainly composed of a microcomputer, and has a battery voltage detector 32, an inverter circuit The output terminals of the input voltage detector 33, the position detector 13, and the speed command output terminal from the traveling control unit (not shown) of the electric vehicle are connected. Also,
Each output port is connected to the transistor 1 of the inverter circuit 16.
7U, 17V, 17W, 18U, 18V, 18W and the bases of the transistors 27, 28 of the chopper circuit 15, respectively.

The operation of the above configuration will now be described. The control circuit 34 switches between a case where the chopper circuit 15 functions as a step-up chopper, a case where the chopper circuit 15 functions as a step-down chopper, and a case where both of the functions are not functioned.

That is, the control circuit 34 also has a function of detecting the rotation speed based on the signal from the position detector 13, and controls the rotation speed of the motor 11 and the running control unit (shown in FIG. 1) of the electric vehicle. Feedback control is performed so as to match the speed command from the above. In this case, the PWM duty ratio, the step-up rate by the chopper circuit 15 and the loop gain of the feedback control are adjusted and controlled. The control forms are roughly classified into the following three.

(A) In this case, when the speed command is relatively low (when the normal output of the motor 11 (rotational speed and torque frequently used) can be less than), the voltage applied to the motor 11 can be low. Then, both transistors 27 and 28 of the chopper circuit 15 are turned off, and the DC voltage of the battery 14 is used as the input voltage of the inverter circuit 16. At this time, the above-described PWM duty ratio is appropriately calculated during the inverter control, and the voltage applied to the motor 11 is appropriately controlled. The loop gain of the feedback control is also set as described later.

(B) If the normal output of the motor 11 is almost sufficient to obtain the rotation speed according to the speed command, the transistors 27 and 28 of the chopper circuit 15 are turned off.
The DC voltage of the battery 14 is the input voltage of the inverter circuit 16. At this time, the voltage applied to the motor 11 is set to the voltage of the battery 14 assuming that the PWM duty ratio is 100% during the inverter control.

(C) Further, when a normal output of the motor 11 is required to obtain a rotation speed corresponding to the speed command, the transistor 28 of the chopper circuit 15 is turned on to act as a step-up chopper. The loop gain of the feedback control is corrected as described later.

The contents of the controls (a), (b) and (c) can be understood from the flowchart of FIG. That is,
The control circuit 34 executes the control shown in the flowchart of FIG. Steps S1 to S5 are loop gain setting / correction processing, and steps S6 to S15 are PID control processing.

In the loop gain setting / correction process, the battery voltage Vbat detected by the battery voltage detector 32 is read (step S1), and the loop gain G is set according to the battery voltage Vbat (step S2). This loop gain G is determined so that G = Gref × Vref / Vbat with respect to the reference voltage Vref and the reference loop gain Gref. That is, the value obtained by multiplying the loop gain G by the motor applied voltage is set to be constant.

Next, the voltage Vdc detected by the inverter circuit input voltage detector 33 is read (step S3).
Battery voltage Vbat and inverter circuit input voltage Vdc
Are compared (step S4). The purpose of this comparison is
If bat <Vdc, it is understood that the boost operation is being performed, and if Vbat = Vdc, it is known that the boost operation is not being performed.

If the boost operation is being performed, the process proceeds to step S5, and the loop gain G set in step S2 is corrected according to the boost ratio (Vdc / Vbat). That is, in this embodiment, the optimum magnification α for the loop gain with respect to the boosting rate is experimentally obtained in advance and stored as data (FIG. 4 shows the relationship between the boosting rate and this magnification α).
The gain α to the loop gain corresponding to the boost rate is accessed, and the gain α is multiplied by the loop gain G (specific value is set to G1) set in step S2 to obtain the final loop gain G (G = G1 × α). Get) Here, the broken line A in FIG. 3 shows the relationship between the general chopper duty ratio and the motor applied voltage, and the magnification α is obtained by adding the final loop gain to the relationship between the chopper duty ratio and the motor applied voltage. FIG. 4 shows that the multiplied values have a proportional relationship. That is, the magnification α is set so that the chopper duty ratio and the motor applied voltage have a proportional relationship indicated by a solid line B in FIG. This final loop gain is used for feedback control for performing boost control of the chopper circuit 15.

If it is determined in step S4 that the voltage is not being boosted, the loop gain is not corrected in step S5, and the loop gain set in step S2 is used for feedback control performed by the PWM control of the inverter circuit 16 later. Is done.

In the PID control process, a speed command is read (step S6), and the rotation speed of the motor 11 is calculated based on the detection signal from the position detector 13 (step S7).
Then, a deviation of the rotation speed is obtained (step S8). Next, a proportional operation process (step S9), an integral operation process (step S10), and a differential operation process (step S11) are performed from the obtained deviation, and a control value serving as a control amount is obtained by adding each process value (step S12). . From this control value, the PWM duty ratio and the boost chopper duty ratio are determined as shown in FIG. 5 (step S13).

Thereafter, the on / off timing of the transistors 17U to 17W and 18U to 18W of the inverter circuit 16 or the transistor 2 of the chopper circuit 15
An energization timing signal is generated for the energization timing of 8 (the transistor 27 is turned off) (step S14), and a base signal is supplied to each of the transistors 17U to 17W, 18U to 18W, or the transistor 28 at the energization timing, and The transistor is turned on / off (step S15).

In steps S13 to S15, the following control is specifically performed. That is, as can be seen from FIG. 5, the chopper circuit 15 is not used until the control value reaches 50% (the transistors 27 and
28 is turned off), the motor 11 is feedback-controlled by PWM duty ratio control, and its loop gain uses the loop gain set in step S2. In such an operation, even when the voltage of the battery 14 decreases, the value obtained by multiplying the loop gain by the voltage applied to the motor is made constant, so that the responsiveness of the feedback control can be made constant. it can.

When the control value exceeds 50%, the PWM duty ratio is set to 100%, and the motor 11 is feedback-controlled by controlling the boost chopper duty ratio by the chopper circuit 15. At this time, the loop gain corrected in step S5 is used. In such an operation, the loop gain is set so that the step-up chopper duty ratio and the inverter circuit input voltage Vdc are proportional to the ratio between the battery voltage Vbat and the inverter circuit input voltage Vdc. Does not become unstable.

By repeatedly executing the control shown in this flowchart at predetermined time intervals, a predetermined AC voltage is supplied to the motor 11 and the motor rotation speed is controlled to a predetermined value. The control circuit 34 controls the motor 1
In the case of regeneration, the transistor 28 of the chopper circuit 15
Is turned off, the transistor 27 is turned on and off at a predetermined energizing timing, and the chopper circuit 1 is turned off.
5 acts as a step-down chopper.

According to this embodiment, the loop gain of the feedback control is set according to the battery voltage Vbat, and the value obtained by multiplying the loop gain by the voltage applied to the motor is constant. Voltage Vb
Even if at decreases, the responsiveness of the feedback control can be kept constant. Further, since the input voltage of the drive circuit 16 can be increased by the chopper circuit 15 even when the voltage of the battery 14 decreases, a predetermined motor output can be obtained.

When the motor 11 is regenerated, the transistor 27 of the chopper circuit 15 is turned on and off at a predetermined energizing timing while the transistor 28 is turned off, so that the chopper circuit 15 operates as a step-down chopper. Therefore, a large regenerative current does not flow to the battery side.

Particularly at the time of boosting, the battery voltage Vb
The step-up chopper duty ratio and the inverter circuit input voltage V according to the ratio between at and the inverter circuit input voltage Vdc
Since the loop gain is corrected so that dc becomes proportional to dc, feedback control can be stabilized.

The present invention may be configured as in the second embodiment shown in FIGS. That is, steps S3 to S5 are omitted (that is, without performing the loop gain correction process) in the first embodiment, and the PWM duty ratio and the boost chopper duty ratio (particularly, the boost chopper duty The ratio may be set as shown in FIG. 6, and the control value and the motor applied voltage may be controlled so as to be in a proportional relationship as shown in FIG. 7 (this corresponds to the step-up chopper duty ratio setting means). In this way, the feedback control can be stabilized.

The present invention may be modified as follows. That is, in each of the above embodiments, the control means is constituted by a control circuit including a microcomputer, but this may be constituted by using an arithmetic circuit and an addition circuit. Also, feedback control is not limited to speed control,
Torque control or current control may be used. The motor may be an induction motor, a two-phase motor, a brushed DC motor, a reluctance motor, or the like. Also, the drive circuit only needs to have one or more arms, and the switching elements other than the transistors include IGBTs, FETs,
A thyristor may be used.

[0039]

As apparent from the above description, the present invention has the following effects. In the motor driving device according to the first aspect, since the boost chopper circuit is interposed between the battery and the driving circuit, a predetermined motor characteristic can be obtained even when the battery voltage is reduced. The loop gain of the feedback control is changed accordingly, so that the response of the feedback control becomes constant even if the battery voltage changes.Furthermore, at the time of boosting by the chopper circuit, the response of the feedback control depends on the battery terminal voltage and the drive circuit input voltage. Thus, the loop gain of the feedback control is corrected, so that stable control can be performed even during chopper control.

In the motor driving device according to the second aspect,
At the time of boosting by the chopper circuit, the loop gain of the feedback control is set according to the ratio between the battery terminal voltage and the drive circuit input voltage. Therefore, the feedback control is further stabilized even during the chopper control.

According to a third aspect of the present invention, there is provided a motor driving device comprising:
By interposing a boost chopper circuit between the battery and the drive circuit, a predetermined motor characteristic can be obtained even if the battery voltage drops, and the loop gain of the feedback control can be changed according to the battery voltage. Therefore, the response of the feedback control is constant even if the battery voltage changes, and the relationship between the control amount calculated by the feedback control means and the motor applied voltage becomes proportional when the voltage is increased by the chopper circuit. Since the step-up chopper duty ratio is set, stable control can be performed even during chopper control.

According to a fourth aspect of the present invention, there is provided a motor driving device comprising:
No large regenerative current flows to the battery side. Since the electric vehicle according to the fifth aspect is equipped with the motor driving device according to the first or third aspect, a stable motor can be achieved and stable running can be achieved even when the voltage of the battery fluctuates.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing control contents.

FIG. 3 is a diagram illustrating a relationship between a boost chopper duty ratio and a motor applied voltage.

FIG. 4 is a diagram showing a relationship between a boost rate and a loop gain magnification α.

FIG. 5 is a diagram showing a relationship between a control value and a duty ratio.

FIG. 6 is a view corresponding to FIG. 5, showing a second embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a control value and a motor applied voltage.

FIG. 8 is a diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

11 is a brushless motor, 13 is a position detector, 14 is a battery, 15 is a chopper circuit, 16 is an inverter circuit (drive circuit), 17U, 17V, 17W and 18U, 1
8V, 18W are transistors (switching elements), 1
9U, 19V, 19W and 20U, 20V and 20W are flywheel diodes, 21U, 21V and 21W are arms, 27 and 28 are transistors (switching elements), 29 and 30 are flywheel diodes,
1 is a reactor, 32 is a battery voltage detector (battery voltage detection means), 33 is an inverter circuit input voltage detector (drive circuit input voltage detection means), and 34 is a control circuit (feedback control means, chopper control means, loop gain setting) Means, loop gain correction means).

Claims (5)

[Claims] An input terminal connected to a battery and an output terminal connected to a motor, wherein the switching element has at least one arm formed by connecting two switching elements having a flywheel diode in series. A drive circuit that controls the energization of the motor by turning on and off the power supply; a feedback control unit that performs feedback control of the motor; a chopper circuit that is connected in parallel with the drive circuit and includes a switching element and a flywheel diode; A reactor connected between the connection point between the switching element and the flywheel diode and the battery, a chopper control means for causing the chopper circuit to perform a boosting operation when necessary, and a battery voltage detection for detecting a terminal voltage of the battery Means and the battery voltage detecting means Loop gain setting means for setting a loop gain for feedback control during non-boosting according to the terminal voltage of the battery detected by the stage; drive circuit input voltage detection means for detecting the drive circuit input voltage; and the chopper circuit Loop gain correction means for correcting a loop gain of feedback control according to the battery terminal voltage detected by the battery voltage detection means and the drive circuit input voltage detected by the drive circuit input voltage detection means at the time of boosting. A driving device for a motor provided. 2. The loop gain correction means corrects a loop gain of feedback control according to a ratio between a battery terminal voltage detected by the battery voltage detection means and a drive circuit input voltage detected by the drive circuit input voltage detection means. 2. The method according to claim 1, wherein
A driving device for the motor according to the above. 3. An electronic device comprising at least one arm comprising two switching elements having a flywheel diode connected in series, an input terminal connected to a battery, and an output terminal connected to a motor, A drive circuit that controls the energization of the motor by turning on and off the power supply; a feedback control unit that performs feedback control of the motor; a chopper circuit including a switching element and a flywheel diode connected in parallel to the drive circuit; A reactor connected between the connection point between the switching element and the flywheel diode and the battery, a chopper control means for causing the chopper circuit to perform a boosting operation when necessary, and a battery voltage detection for detecting a terminal voltage of the battery Means and the battery voltage detecting means Loop gain setting means for setting a loop gain for feedback control during non-boosting according to the terminal voltage of the battery detected by the stage; and a proportional relationship between the control amount calculated by the feedback control means and the motor applied voltage. And a step-up chopper duty ratio setting means for setting a step-up chopper duty ratio such that 4. The chopper circuit is configured such that a parallel circuit of a switching element and a flywheel diode is connected in series so as to perform both step-up and step-down. When the voltage is supplied and the step-up is required, the chopper circuit can be operated as a step-up chopper, and when the motor is regenerated, the two switching elements are controlled to be on and off so as to be able to operate as a step-down chopper. The motor driving device according to claim 1 or 3, wherein: 5. An electric vehicle, comprising the motor driving device according to claim 1 mounted thereon.