JPH06105563A - Motor driver and air conditioner using the same - Google Patents

Abstract

PURPOSE:To operate a motor under optimum conditions in response to an operating state and to obtain an operation having high efficiency and small vibration. CONSTITUTION:A booster 3 is provided between a rectifier 2 and an inverter 4, and a motor 5 is controlled by switching to a range for PWM-controlling the inverter 4 while a DC input voltage of the inverter 4 is held at a predetermined constant voltage and a range for PAM-controlling the inverter 4 while the DC input voltage of the inverter 4 is varied by the booster 3. Thus, the motor 5 can be efficiently controlled in a wide range of the output of the motor 5.

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 using an inverter, and in particular, it converts electric power from an AC power supply into DC power having a voltage higher than the voltage of the AC power supply, and converts the DC power. The present invention relates to an electric motor drive device that controls a rotation speed over a wide range by converting the AC power into an AC power by an inverter and supplying the AC power to the electric motor.

[0002]

2. Description of the Related Art As a prior art of a motor drive device using an inverter, as described in, for example, Japanese Patent Application Laid-Open No. 59-181973, the output voltage of the inverter is controlled and the DC voltage which is the input of the inverter is controlled. There is an electric motor drive device of a system in which it is divided into a region where the input DC voltage is kept constant and a region where the conduction ratio of the inverter is controlled.

More specifically, in the electric motor drive device according to this prior art, when the inverter output voltage command is larger than a preset DC voltage reference value, the duty ratio of the inverter is fixed to, for example, the maximum value. As it is, the DC voltage is controlled according to the inverter output voltage command. On the other hand, when the inverter output voltage command is smaller than the DC voltage reference value, the DC voltage remains the DC voltage reference value, and Is controlled so that the output voltage of the inverter matches the inverter output voltage command.

In such a prior art, when the output of the motor is small, the DC voltage is kept constant at a low voltage to reduce the switching loss of the inverter and realize the highly accurate control. Further, when the motor output becomes large, the inverter only controls the frequency, and the DC voltage is controlled to realize the rotation speed control.

[0005]

In the motor drive device according to the above-mentioned prior art, the DC voltage value is determined by the difference between the inverter output voltage command and the DC voltage reference value. When the inverter output voltage is determined, there is a problem that the command value of the DC voltage cannot be determined.

Further, when the DC voltage is higher than the DC voltage reference value, the inverter output becomes maximum. Therefore, for example, when the power supply input is a single phase, fluctuations in the power supply caused by the DC voltage may cause fluctuations in the motor torque or the motor. There is a problem that the current may fluctuate.

Further, when performing variable speed operation in the air conditioner, the variable speed range and the load fluctuation range are wide, and the operating conditions of the electric motor differ depending on the operation mode of the air conditioner. There was a problem that optimum driving could not be realized.

An object of the present invention is to provide an electric motor drive device capable of sufficiently addressing the above problems of the prior art.

[0009]

In order to achieve the above object, an AC / DC converting means for obtaining a DC voltage higher than a power supply voltage from an AC power source, an inverter for converting the DC voltage into an AC voltage, and an inverter driven by the inverter. A voltage control means for controlling the AC / DC converting means so that the DC voltage matches a command value, and an inverter output frequency and an inverter output power so that the motor operates at a commanded speed. In a motor drive device having speed control means, the output voltage of the inverter is controlled by the voltage control means in a region where the output power of the inverter is a predetermined value or less, and the output power of the inverter exceeds the predetermined value. Then, the inverter is pulse width modulated to control the output voltage.

In order to achieve the above object, the difference between the pulse current of the pulse width modulated signal and a preset preset pulse current ratio,
And a detecting means for detecting any one of a difference between the DC voltage and a predetermined voltage set in advance, an input power supplied from a power source, a DC power supplied to an inverter, an inverter output supplied to an electric motor, or an output of the electric motor. The command value of the DC voltage should be determined by the current value detected by the detection means that detects the power detected by the power supply, the input current supplied from the power supply, the DC current supplied to the inverter, or the winding current of the motor. It is the one.

Further, the motor control means for controlling the DC voltage higher than the inverter output voltage and the means for detecting the DC current supplied to the inverter are provided, and the DC power supply fluctuation is smaller than the specified value, independently of the inverter control. The DC voltage is controlled.

Further, the motor control means for controlling the DC voltage higher than the inverter output voltage and the means for detecting the power or current supplied from the AC power supply are provided, and the inverter control is performed so as to minimize the power input from the AC power supply. Is to control the DC voltage independently.

Further, the capacity of the air conditioner is controlled by using the above-mentioned electric motor drive device.

[0014]

With the above construction, the electric power supplied to the electric motor is estimated from the difference between the duty ratio of the pulse width modulated signal and the preset predetermined duty ratio and the difference between the DC voltage and the preset predetermined voltage. Then, it works to determine the DC voltage and the inverter output voltage according to this power.

Further, input power (or current) supplied from a power source, DC power (or current) supplied to the inverter, inverter output (or current) supplied to the electric motor,
The DC voltage and the inverter output voltage are determined by using the difference between the detection value detected by the detection means for detecting any one of the outputs of the electric motor and the maximum output that can be supplied by the inverter at the voltage at that time.

Further, by controlling the DC voltage higher than the inverter output voltage and simultaneously controlling the inverter with a low DC voltage, the power supply current or the power is minimized or the fluctuation range of the DC current is within a predetermined range. Thus, the DC voltage command value is determined.

Further, by controlling the capacity of the air conditioner using the above-mentioned electric motor drive device, the operation at the optimum point of vibration and vibration according to the operation mode of the air conditioner is realized.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A motor drive device according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a first embodiment of the present invention, which is composed of a rectifier circuit 2, a booster circuit 3, an inverter 4, and a motor control device 6, and changes the AC power supplied from an AC power source 1 into a variable voltage. , Is converted into AC power of variable frequency and supplied to the electric motor 5, so that the electric motor (three-phase induction motor) 5 is subjected to variable speed drive control according to the speed command value N _R. .

The rectifier circuit 2 functions to rectify the AC voltage supplied from the AC power supply 1 and input the DC voltage to the booster circuit 3. The booster circuit 3 includes an inductance element, a switching element, and a diode. When the switching element is turned on, the electric circuit on the output side of the inductance element is short-circuited to allow a direct current to flow through the inductance element and store energy in the inductance element. After that, the switching element is turned off, the voltage generated in the inductance element by this is added to the input DC voltage, and the capacitor C is added.
It is charged to 1 to boost the input DC voltage.

According to the booster circuit of this type,
By controlling the on / off time ratio of the switching element (hereinafter referred to as duty or conduction ratio), the AC side input current is controlled in a sine wave shape, and the power factor can be improved. The DC voltage can be controlled (hereinafter referred to as PAM control) by controlling the magnitude (absolute value).

The inverter 4 has a function of converting the DC voltage supplied from the booster circuit 3 into an AC of an arbitrary frequency again by pulse width modulation and supplying the AC voltage to the electric motor 5. That is, the terminals of each phase of the electric motor 5 are connected to the positive side and the negative side of the DC power supply via the switching elements in the inverter 4, and the terminals of the electric motor 5 are turned on and off by the switching elements of each phase. The alternating voltage is alternately inverted and the DC voltage is applied during the period, and the AC power is supplied to the electric motor 5.

The electric motor 5 rotates at an arbitrary rotation speed and torque according to the frequency and current of the AC power supplied from the inverter 4 and drives a load.

The electric motor control device 6 detects the rotation speed of the electric motor 5 by the rotation signal S4 obtained from the magnetic pole position detection sensor P1 and the like, and outputs the inverter drive signal S2 so as to match the speed command value N _R. The inverter drive signal S2 is a signal for turning on / off the switching element connected to each arm of the inverter 4, and is modulated by the pulse width modulation signal. The output voltage Vinv or the inverter output current Iinv of the inverter 4 is changed by this modulation degree. Control (hereinafter referred to as PWM control).

Further, the motor control device 6 outputs the booster circuit drive signal S1 so that the DC voltage detection signal S3 detected by the DC voltage detector R3 matches the voltage command value VdR. The booster circuit drive signal S1 turns on / off the switching element of the booster circuit 3 to control the DC voltage. Details of the electric motor control device 6 will be further described with reference to the drawings.

As shown in FIG. 2, the electric motor control device 6 calculates the rotational speed of the electric motor 5 from the rotation signal S4 and outputs a speed detection value N, a speed detection device 605, a speed detection value N and a speed command. the value N _R, speed controller 610 which outputs a voltage command value V _dR to conduction ratio command value D _R and the booster circuit 3 to the inverter 4, the conduction ratio command value D _R for driving the inverter 4 It is composed of a _duty ratio generating device 603 which outputs an inverter drive signal S2, and a DC voltage control device 601 which drives a switching element of the booster circuit 3 according to the voltage command value V _dR and controls a DC voltage.

Further, the speed control device 610 communicates with the speed control unit 613 which calculates the speed deviation value Ne from the speed detection value N and the speed command value N _R , and the speed deviation value Ne or the speed deviation zero signal N _Z. The voltage command intermediate value V _dRM and the voltage command value V from the current flow rate command unit 612 that calculates the rate intermediate value D _RM and the flow rate command value D _R , the speed deviation value Ne or the speed deviation zero signal N _Z.
The voltage command unit 611 that calculates _dR , and whether to transmit the speed deviation value Ne to the current ratio command unit 612 or the voltage command unit 611 is selected according to the operating state of the electric motor, the current ratio, and the DC voltage. And a switching unit 614.

Then, the switching unit 614 _{controls the} speed deviation value Ne, the conduction ratio intermediate value D _RM, and the voltage command intermediate value V _dRM.
Switching is performed based on. Then, the speed deviation value N
When e is transmitted to the flow rate command unit 612, PWM control is performed based on the speed deviation value Ne, and the speed deviation value N
When e is transmitted to the voltage command unit 611, PAM control is performed based on the speed deviation value Ne, while when the zero speed deviation signal N _Z is transmitted, the flow rate command unit 61 is transmitted.
In 2, the maximum _duty ratio command value D _RMAX is output, and in the voltage command unit 611, the minimum DC voltage command value V _dRMIN is output.

The electric motor control device 6 configured as described above is
The PWM control and the PAM control are switched according to the operating conditions, and the electric motor 5 is controlled so that the speed detection value N matches the speed command value N _R.

Next, the operation of the motor control device 6 will be described with reference to FIGS. 3 and 4. 3 shows a switching algorithm of the switching unit 614 according to one embodiment of the present invention, and FIG. 4 shows a relationship between the DC voltage V _d and the conduction ratio D with respect to the electric motor output in the electric motor control device 6. is there.

Below, in the motor starting state, the flow rate command value D _R = 0% and the DC voltage command value V _dR = 150 V are given as initial values in the speed control device 610, and the switching unit 61 is provided.
4, it is assumed that the speed deviation value Ne is connected to the flow rate command unit 612, and the description will be given according to the algorithm shown in FIG.

In FIG. 3, first, at 621, acceleration / deceleration is determined by accelerating if the speed deviation value Ne is positive and decelerating if the speed deviation value Ne is negative. And if the motor is accelerating 622
Then, the flow rate intermediate value D _RM is used to determine whether the flow rate command value is the maximum value. If the flow rate is the maximum flow rate, the process proceeds to 624, where the flow rate command Ne is transmitted to the flow rate command value. The part 612 is switched to the voltage command part 611, the direct-current voltage is controlled by the booster circuit 3, and the speed of the electric motor 5 is controlled. At this time,
Since the zero velocity deviation signal N _Z is input to the flow rate command unit 612, the maximum flow rate command value D is output from the flow rate command unit 612.
_RMAX is output and the flow rate is the maximum value (here 100%)
Controlled by.

If the motor 5 is decelerating at 621, then 6
23, it is determined whether the DC voltage command value becomes the minimum DC voltage value using the voltage command intermediate value V _dRM . If the DC voltage command value is the minimum DC voltage value, the process proceeds to 625, and the speed deviation value Ne is transmitted to the voltage command unit. The flow rate control unit 612 is switched to the flow rate command unit 612, and the speed of the electric motor 5 is controlled by controlling the electric motor voltage applied to the electric motor 5 by the inverter 4. At this time, since the zero speed deviation signal N _Z is input to the voltage command unit 611, the minimum DC voltage command value V is output from the voltage command unit 611.
_dRMIN is output, and the DC voltage is at the minimum value (150 in this case).
V).

By the way, in this embodiment, the speed deviation value N
Although the switching was performed based on e, the intermediate value of conduction ratio D _RM and the intermediate value of voltage command V _dRM , any value may be used as long as it is a value related to the operating state of the electric motor, the conduction ratio and the DC voltage. . Furthermore, it is possible to switch using any value that shows the maximum output point (with respect to voltage) of the motor.

Returning to FIG. 3, at 621, when the electric motor 5 is rotating at a constant speed, at 622, the flow rate command value is 100% or less, or at 623, the DC voltage command value is 150 V or more, 626.
Continue to the current state.

Therefore, according to the electric motor drive device 6,
As shown in FIG. 4, when the electric motor 5 has a low output, the booster circuit 3
Controls the DC voltage to 150 V, and the inverter 4 controls the electric motor voltage by changing the conduction ratio according to the speed deviation value Ne to control the electric motor speed. And
At the time when the DC voltage reaches 150 V, when the maximum output that can be output by the electric motor 5 is reached, the duty ratio command value D _R is 100%.
Therefore, the connection of the speed deviation value Ne is switched, the voltage command value V _dR increases, and from there, the booster circuit 3 increases the DC voltage V _{D as} shown in FIG. After that, when the electric motor 5 is in a high output state, the speed of the electric motor is controlled by controlling the electric motor voltage by the booster circuit 3.

On the contrary, when the electric motor 5 changes from the high output state to the low output state, the voltage command value V _dR becomes 150 V or less, so that the maximum output that the electric motor 5 can output when the DC voltage drops to 150 V. At the point, the connection of the speed deviation value Ne is switched, the conduction ratio command value D _R is decreased, and the electric motor voltage is decreased by the inverter 4. Thereafter, the inverter 4 changes the electric motor voltage according to the speed deviation value Ne. To control the speed of the electric motor.

Therefore, in the first embodiment, by performing the above operation, the booster circuit 3 does not need to raise the DC voltage more than necessary, and the loss due to the switching of the booster circuit 3 can be reduced. Further, the inverter 4 also has a low DC voltage, so that the loss due to switching can be reduced, and the maximum voltage (instantaneous value) applied to the electric motor 5 becomes small, so that the fluctuation of the electric motor current due to switching becomes small, and therefore, The eddy current that is not related to the motor output induced on the rotor side is reduced, and the loss can be reduced.

Next, another embodiment of the present invention will be described. FIG. 5 shows a second embodiment of the present invention, and the same reference numerals as those in the embodiment of FIG. 1 indicate the same parts. In FIG. 5, first, the input current detector R1 functions to detect the current supplied from the AC power supply 1 to the rectifier 2 to generate the input current detection signal S5 and supply it to the motor controller 60. Next, the DC current detector R4 functions to generate a DC current detection signal S6 that detects the DC current supplied to the inverter 4 and supply it to the electric motor control device 60.

FIG. 6 is a detailed configuration diagram of the electric motor control device 60. The same reference numerals as those in the embodiment of FIG. 2 indicate the same operations and the same parts. The difference between the embodiment of FIG. 6 and the embodiment of FIG. 2 is that the speed control device 620 and the flow rate generation device 60 are different.
7 and the power factor correction device 630.

The speed control device 620 outputs a current command value I _dR and a voltage command value V _dR based on the speed command value N _R and the speed detection value N to control the rotation speed of the electric motor 5, At the DC voltage, when the actual DC power input to the electric motor 5 becomes equal to the maximum DC power, the PWM control and the PAM control are switched.

Therefore, the speed control device 620 calculates the voltage command value V _dR based on the speed control unit 613 which outputs the speed deviation value Ne and the value obtained by multiplying the speed deviation value Ne by the variable gain K1. The unit 611, the current command unit 616 that calculates the current command value I _dR based on the value obtained by multiplying the speed deviation value Ne by the variable gain K2, the DC current detection signal S6 and the DC voltage detection signal S3, which are detected at that time. A maximum power calculation unit 631 that calculates the maximum DC power that can be input to the electric motor 5 with a DC voltage, and an input power calculation unit 63 that calculates the input power from the input current detection signal S5 and estimates the DC power.
2, and the variable gain K based on the speed deviation value Ne, the output of the maximum power calculation unit 631 and the output of the input power calculation unit 632.
And a switching unit 615 that changes the gains of 1 and K2. In this embodiment, the variable gain K
One of K1 and K2 has a gain of 1, and the other has a gain of 0.

The duty factor generator 607 drives the inverter 4 and controls the direct current, and functions to output the inverter drive signal S2 based on the deviation between the current command value I _dR and the direct current detection signal S6. . Power factor correction device 630
Is a device that controls the power supply current in a sine wave shape (power factor improvement) using the booster circuit 3 and at the same time controls the DC voltage to a predetermined value, and performs power factor improvement control using at least the input current detection signal S5. , A step-up circuit drive signal that functions to control the DC voltage based on the voltage command value V _dR and that can perform DC voltage control at the same time as power factor improvement by the input current detection signal S5 and the voltage command value V _dR and the DC voltage detection signal S3. It outputs S1.

Next, FIG. 7 shows a switching algorithm of the switching circuit 615. The switching algorithm of 641 in FIG.
Is the same as 621 in the embodiment of FIG. 3, and the description is omitted. First, if the electric motor 5 is accelerating, the process proceeds to 642, and if the output of the maximum power calculation unit and the output of the input power calculation unit are compared and there is no difference, the process proceeds to 644. In 644, the maximum power calculation unit output at that time is stored as reference power, and 64
In step 6, the variable gain K1 is set to gain 1, and the variable gain K2 is set to gain 0.

Next, when the electric motor 5 is decelerating, 643
In step 645, the output of the input power calculator is compared with the stored reference power, and when there is no difference, the process proceeds to step 645 where the variable gain K1 is set to gain 0 and the variable gain K2 is set to gain 1. Further, at 641, the electric motor 5 is rotating at a constant speed, or 6
42, the input power calculator output is less than the maximum power,
64 when the input power calculation unit output is 43 or more at the reference power
Go to 7 and maintain the current state.

Therefore, when the electric motor drive device 60 according to this embodiment is operated in accordance with the switching algorithm of FIG. 7, the electric motor 5 is driven as shown in FIG. 4 as in the first embodiment.
When the output is low, the booster circuit 3 controls the DC voltage to 150 V (when the minimum DC voltage command V _dRMIN is set to 150 V), and the inverter 4 controls the motor voltage according to the speed deviation value Ne, and Perform speed control. When the DC voltage becomes 150 V and the actual DC power becomes the maximum DC power that can be input to the electric motor 5, the variable gain K1
The gains of K2 and K2 are switched, the voltage command value V _dR increases, and the booster circuit 3 raises the DC voltage as shown in FIG. After that, when the electric motor 5 is in a high output state, the booster circuit 3
The motor voltage is controlled to control the speed of the motor.

On the contrary, even in the case of changing from the high output state to the low output state, when the DC voltage reaches the maximum output point that can be input to the electric motor 5 at the time of 150 V, the gains of the variable gains K1 and K2 are switched to change the conduction ratio. The command value D _R decreases and the inverter 4 lowers the electric motor voltage. After that, the inverter 4 controls the electric motor voltage according to the speed deviation value Ne to control the speed of the electric motor.

Therefore, according to this second embodiment, the first
It is possible to obtain the same effect as that of the above embodiment, and since the power factor correction device 630 is used instead of the voltage control device,
The power factor of the power supply can be improved at the same time as the rotation speed control of the electric motor 5. In addition, since the duty ratio generating device 607 can control the direct current, the motor can be controlled with high accuracy.

In the second embodiment, the maximum electric power that can be input to the electric motor at the voltage at that time and the input electric power supplied from the power source are used to switch the gains of the variable gains K1 and K2. Instead of this, the switching may be performed using the DC power supplied to the inverter 4 or the output of the electric motor 5. Also, the same effect can be obtained by switching using a power supply current, a direct current, and a motor winding current.

Next, another embodiment of the present invention will be described. First, FIG. 8 is a diagram for explaining the operation in one embodiment of the present invention, and this diagram shows the operating characteristics of the motor drive device. The horizontal axis shows the motor output and the vertical axis shows the voltage. The DC voltage V _d
And the inverter output voltage V _inv are also shown. As is apparent from FIG. 8, in this embodiment, the DC voltage V _d is controlled to a constant voltage when the motor output is small, and is increased to a higher voltage when the motor output is large by increasing the boost ratio. When the motor output is large, the DC voltage V _d is kept higher than the inverter output voltage V _inv .

In the PWM control, when the inverter is switched, the voltage applied to the winding of each phase of the electric motor changes to DC voltage V _d and zero (or −V _d ) depending on the on / off state of the switching element. At this time, a change in voltage and a change in current overlap each other, so that a loss proportional to the product of current and voltage occurs in the switching element.

Further, at this time, the line voltage of the electric motor fluctuates, so that the fluctuation component of the switching frequency is added to the armature winding current, and the eddy current induced on the rotor side and not related to the electric motor output flows. Result in loss. Therefore,
These losses can be reduced by switching at a low voltage when the motor output is small. Then,
If the DC voltage V _d is made equal to the inverter output voltage V _inv, it becomes impossible to control the motor with high precision by controlling the inverter, and the motor cannot be operated under the optimum operating conditions.
Efficiency and control characteristics will deteriorate.

Therefore, in the following embodiments of the present invention, the direct current voltage V _d is set in order to have both the low loss characteristic by operating at a low voltage and the high accuracy of control by the inverter control. The control is performed slightly higher than the inverter output voltage V _inv to realize the optimum electric motor operation.

First, FIG. 9 shows a third embodiment of the present invention.
The same symbols as those in the embodiment of FIG. 1 or 5 represent the same parts.
Next, FIG. 10 shows an electric motor control device 61 in this embodiment.
2, the same reference numerals as those in the embodiment of FIG. 2 represent the same parts, and as is clear from this figure, in this embodiment, the flow rate generation device 603, the speed control device 604, and the speed calculation device are provided. A motor control system including a device 605, a voltage control device 601, a voltage command device 653, and a storage device 65.
The DC voltage control system composed of 2 is independent from the DC voltage control system. The rotation speed control is performed by PWM control by the electric motor control system, and the DC voltage control is performed by PAM control by the voltage control system.

The speed control device 604 is the speed calculation device 60.
The flow rate command value D _R associated only with the speed control is created so that the difference between the speed detection value N input from 5 and the speed command value N _R is zero. In parallel with this, the speed control device 604 outputs the speed error amount due to the shortage of the DC voltage as the speed deviation value Ne.

As described above, the DC voltage control system includes the voltage control device 601, the voltage command device 653, and the storage device 652.
The input current detection signal S5 is input to the voltage command device 653. The storage device 652 is composed of a readable / writable storage element, and stores the voltage command V _dRm at which the input current I _S becomes the smallest at that time and the input current I _Sm at that time.

The speed deviation value Ne supplied from the speed control device 604 is added to the voltage command V _dR which is the output of the voltage command device 653, and the DC voltage command value is corrected by the rotational speed error. As a result, if the speed deviation does not become zero even if the maximum flow rate is output by the speed control device, the voltage command is set higher by the speed deviation signal Ne.

When the input current I _S obtained from the input current detection signal S5 is smaller than the input current I _dm stored in the storage device 652, the voltage command device 653 outputs the voltage command V _dR and the input current at that time. _Let I _S be V _dRm and I _sm
Is recorded in the storage device 652. Further, the voltage command device 653 sequentially outputs at least three kinds of voltages, that is, a voltage command V _dRm stored in the storage device 652 at a certain cycle, a voltage V _dRm + Δ that is slightly higher than this, and a voltage V _dRm −Δ that is slightly lower. To do. And the voltage command V corresponding to the minimum input current
The input current value when _dRm is output is stored in the storage device 652.
If it is different from the I _sm stored in, update it.

Next, the operation of the electric motor control device 61 shown in FIG. 10 will be described with reference to FIG. It is assumed that V _d 1 is output as the voltage command V _dR at a certain point in time, the input current at this time is I _S 1, and these values are stored in the storage device 652. After the lapse of time, the voltage command is changed to V _dRm −Δ = V _d 2. Then, since the input current I _S 2 due to this is smaller than the current value I _Sm stored in the storage device 652, the DC voltage command value V _d 2 is _stored as V _dRm , and the input current I _S 2 is stored as I _Sm. . After that, the voltage command is changed again to V _dRm −Δ = V _d 3, and the DC voltage command value V _d 3 _{resulting therefrom} is V _dRm .
The input current I _S 3 is stored as I _Sm .

Therefore, for subsequent changes in the voltage command, the input currents become I _S 4 and I _S 2, both of which are I _S 4.
is greater than _sm, the content of the storage device 652 is not updated, now repeated to output a V _d 2~V _d 3, as a result, the voltage command V _dR is determined in the vicinity of the point input current is smallest, Efficient driving can be realized.

Next, when the rotation speed or output torque of the electric motor 5 changes, the input current changes when V _dRm is _set to the DC voltage command value, and becomes a value different from I _Sm , so the storage device 652. The content of is updated, and the input current minimum value is searched again. Therefore, according to this embodiment, efficient operation control can always be obtained.

FIG. 12 is a waveform diagram showing how the electric motor control device 61 performs control. At time t1, the speed command N
_This shows a case where the motor output changes as shown in (a) of FIG. 12 due to a change in _R or an increase in load. At this time point t1, the voltage command V _dRm does not match the minimum value of the input current detection signal. Therefore, the DC voltage is sequentially changed by the algorithm described above as shown in FIG. As shown in (c), the power supply current I _S
The operation is performed so as to approach the DC voltage that minimizes.

When the input side AC voltage is constant, the input current is proportional to the input power. Therefore, according to the third embodiment, the input power minimum operation can be easily realized and the maximum efficiency operation can be achieved. Obtainable. When the AC voltage changes, the input power may be detected instead of the input current and the same operation may be performed.

Next, another embodiment of the present invention will be described. FIG. 13 shows an electric motor drive device according to a fourth embodiment of the present invention, and the same symbols as those in the embodiment of FIG. 1 or 9 represent the same parts. Here, the DC current detector R4 functions to detect the current supplied to the inverter and input the DC current detection signal S5 to the motor control device 62.

Next, FIG. 14 is a detailed block diagram of the electric motor control device 62 in this embodiment. In FIG.
The same reference numerals as those in the above embodiment represent the same parts. In FIG. 14, the DC current detection signal S6 supplied from the DC current detector R4 is input to the conduction ratio generator 607 and the current fluctuation detector 651. Speed control device 606
Creates a current command value I _dR related only to speed control so that the difference between the speed command value N _R and the speed detection value N input from the speed calculation device 605 becomes zero.

The conduction ratio generator 607 determines the current command value I _dR.
And the inverter drive signal S2 pulse-width-modulated so that the DC current detection value S6 and the DC current detection value S6 match. The current fluctuation detection device 651 outputs a DC current fluctuation value ΔId which is the difference between the maximum current value and the minimum current value within a certain fixed time. Voltage command unit 602, the direct current variation value [Delta] I _d is the DC when the current allowable fluctuation range Δmax larger increases the DC voltage command value V _dR, DC current variation value [Delta] I _d is smaller than the direct current allowable fluctuation range Δmax In this case, the DC voltage command value V _dR is decreased.

Here, the DC voltage fluctuation increases as the PWM-modulated DC current I _d increases. Also,
The magnitude of the DC current I _d, if the output of the electric motor 5 is constant, is proportional to the DC voltage (V _d) × direct current (I _d), it is increased DC voltage is low. Therefore, by keeping the DC current fluctuation value ΔI _d constant within the DC current fluctuation allowable width Δmax, the DC voltage V _d becomes equal to the inverter output voltage Vin.
will be kept higher than v.

Next, the operation of the electric motor control device 62 will be described with reference to FIG. Now, it is assumed that the DC voltage V _d 1 is output as the DC voltage command value V _dR at a certain point in time. At this time, the DC current fluctuation value is ΔI _d
If it is 1, since ΔI _d 1> Δmax, the DC voltage command value V _dR is increased to V _d 2. Then,
Since the DC current fluctuation value ΔI _d 2> Δmax at this time, the DC voltage command value V _dR is further increased to V _d 3. Then, at this point, the DC current fluctuation value ΔI _d 3 <Δm
It becomes ax, and the DC voltage command value V _dR is kept at this value. According to this, the operation at the minimum DC voltage in which the DC current fluctuation value ΔI _d is accommodated within the current fluctuation allowable width Δmax is realized. Therefore, according to this embodiment, the loss is small and the current fluctuation is small. Since the operation can be realized, it is possible to easily obtain the operation in the state where the torque fluctuation due to the current fluctuation is small.In this embodiment, when the rotation speed or the output torque of the motor changes, the DC current fluctuation The value ΔI _d changes, the voltage command V _dR changes so as to be within the allowable range, and the DC voltage is adjusted so that the DC current fluctuation value ΔI _d falls within the current fluctuation allowable value Δmax.

FIG. 16 is a waveform diagram showing the operation when the electric motor 5 is operated by the electric motor control device 62. At time t1, the speed command N _R changes or the load increases, and so on. As shown in (a), it shows the case where the rotation speed and output torque of the electric motor change. Then, at this time point t1, the DC voltage value V _d and the DC current fluctuation value ΔId change as shown in FIGS. 7B and 7C, and the DC voltage command value is sequentially changed by the algorithm. However, the DC current fluctuation value ΔI _d gradually approaches the voltage at which it becomes Δ _max .

By the way, as is apparent from the above description, according to the electric motor drive device of the above-mentioned embodiment, the optimum electric motor operation can be easily obtained, and therefore, it can be applied to the device using various electric motors. However, here, a case where it is applied to an air conditioner will be described as an example of such a device.

FIG. 17 shows an example of the operation mode of the air conditioner according to one embodiment of the present invention. The horizontal axis of the drawing shows the output torque T of the compressor operating electric motor, and the vertical axis thereof. The number of rotations is shown. First, in the conventional air conditioner, the electric motor is operated at a constant DC voltage V _dc as an input of the inverter, and only the range where the DC voltage is lower than this is used by PWM control.

On the other hand, according to the air conditioner of the present invention, the DC voltage V _dmin is used when the load is low, and the DC voltage is boosted by the PAM control in the region where a higher DC voltage is required. Use all areas within the maximum input range. This makes it possible to operate at the point indicated as defrosting operation in the figure, compressing the refrigerant almost, defrosting in simple refrigerant circulation mode, and suppressing cold air blowing during defrosting. You can Further, since the operation is performed in a state where the DC voltage is low in the dark portion in the figure, loss is suppressed and energy saving operation can be obtained.

[0072]

According to the present invention, the electric current is supplied to the electric motor from the difference between the duty ratio of the pulse width modulation signal and the predetermined duty ratio set in advance and the difference between the DC voltage and the predetermined voltage preset. Since the electric power is estimated and the DC voltage and the inverter output voltage are determined according to the electric power, there is an effect of always realizing a predetermined switching mode and a predetermined DC voltage / inverter output voltage ratio regardless of the control method of the electric motor.

Further, according to the present invention, the input power (or current) supplied from the power source, the DC power (or current) supplied to the inverter, and the inverter output supplied to the electric motor.
(Or current), because the DC voltage and the inverter output voltage are determined using the difference between the detection value detected by the detection means that detects either the output of the motor and the maximum output that the inverter can supply at the voltage at that time, There is an effect that a predetermined switching mode and a predetermined DC voltage / inverter output voltage ratio are always realized by using the detected value that can be most easily detected by the configuration of the driving device.

Furthermore, according to the present invention, by controlling the DC voltage higher than the inverter output voltage, the inverter can be controlled at a low DC voltage at the same time, so that the operation with a small torque fluctuation and the operation with the smallest input can be performed. It is effective in realizing electric motor control according to the demands of the electric motor.

Further, according to the present invention, since the capacity control of the air conditioner is performed by using the electric motor drive device which independently controls the DC voltage and the output of the inverter, the efficiency and the vibration optimum according to the operation mode of the air conditioner are optimized. It has the effect of realizing driving at points.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an electric motor drive device according to the present invention.

FIG. 2 is a block diagram showing an electric motor control device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a switching unit P according to the first embodiment of the present invention.
It is explanatory drawing which shows a WM control / PAM control switching algorithm.

FIG. 4 is an operational characteristic diagram of the first embodiment of the present invention.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a block diagram showing an electric motor control device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a switching unit P according to the second embodiment of the present invention.
It is explanatory drawing which shows a WM control / PAM control switching algorithm.

FIG. 8 is an operation characteristic diagram for explaining the concept of control in the embodiment of the present invention.

FIG. 9 is a block diagram showing a third embodiment of the present invention.

FIG. 10 is a block diagram showing an electric motor control device according to a third embodiment of the present invention.

FIG. 11 is an operating characteristic diagram of the third embodiment of the present invention.

FIG. 12 is a waveform diagram illustrating the operation of the third exemplary embodiment of the present invention.

FIG. 13 is a block diagram showing a fourth embodiment of the present invention.

FIG. 14 is a block diagram showing an electric motor control device according to a fourth embodiment of the present invention.

FIG. 15 is an operating characteristic diagram of the fourth embodiment of the present invention.

FIG. 16 is a waveform diagram illustrating the operation of the fourth embodiment of the present invention.

FIG. 17 is an explanatory diagram of an operation mode of an embodiment of the air conditioner according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Booster circuit 4 Inverter 5 Electric motor 6, 60, 61, 62 Electric motor control device 601 Voltage control device 602, 653 Voltage command device 603, 607 Current flow control device 605 Speed calculation device 604, 606, 610 , 620 Speed control device 614, 615 Switching unit 611 Voltage command unit 612 Duty factor command unit 616 Current command unit 630 Power factor correction device 651 Current fluctuation detection device 652 Storage device NR Speed command value N Speed detection value S1 Boost circuit drive signal S2 Inverter drive signal S3 DC voltage detection signal S4 Rotation signal S5 Input current detection signal S6 DC current detection signal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Ishii 800 Tomita, Ohira Town, Shimotsuga-gun, Tochigi Prefecture Tochigi Plant, Hitachi Ltd.

Claims (9)

[Claims] 1. An AC / DC converting means for obtaining a DC voltage higher than a power supply voltage from an AC power supply, an inverter for converting the DC voltage into an AC voltage, and an electric motor driven by the inverter, wherein the DC voltage is a command value. In a motor drive device having voltage control means for controlling the AC / DC conversion means so as to match, and speed control means for controlling the inverter output frequency and the inverter output power so that the electric motor operates at a commanded speed, The output voltage of the inverter is controlled by the voltage control means in a region where the output power of the inverter is less than or equal to a predetermined value, and the output voltage is pulse-width modulated to control the inverter in a region where the output power of the inverter exceeds the predetermined value. An electric motor drive device comprising an electric motor control means for controlling the motor. 2. The invention according to claim 1, further comprising detection means for detecting at least one of input power supplied from a power supply, DC power supplied to an inverter, inverter output supplied to an electric motor, and output of an electric motor. However, the electric motor control means is configured to identify the region according to a difference between a value detected by the detection means and a maximum output that can be supplied by the inverter at the voltage at that time. Drive. 3. The invention according to claim 1, further comprising detection means for detecting at least one of input power supplied from a power supply, DC power supplied to an inverter, inverter output supplied to an electric motor, and output of an electric motor. However, the electric motor control means is configured to identify the region according to a difference between a value detected by the detection means and a maximum current that can be supplied by the inverter at the voltage at that time. Drive. 4. An AC / DC converting means for obtaining a DC voltage higher than a power supply voltage from an AC power supply, an inverter for converting the DC voltage into an AC voltage, and an electric motor driven by the inverter, wherein the DC voltage is a command value. And a speed control means for controlling the inverter output frequency and the inverter output power by a pulse width modulation signal so that the electric motor operates at a commanded speed. An electric motor drive device, comprising: an electric motor control means for controlling a DC voltage higher than an output voltage of the inverter. 5. The invention according to claim 4, further comprising detection means for measuring a current or electric power supplied from an AC power supply, and directing the DC voltage so that the power supply current or electric power measured by the detection means is minimized. A motor drive device characterized in that a voltage command device for determining a value is provided in the AC / DC converting means. 6. The invention according to claim 4, wherein a detecting means for measuring a direct current supplied to the inverter is provided, and the alternating current to direct current converting means calculates a fluctuation range of the direct current measured by the detecting means. And a voltage command device that determines a DC voltage command value such that the fluctuation range of the DC current detected by this means falls within a predetermined range. 7. The invention according to claim 4, further comprising a detection means for measuring a current or an electric power supplied from an AC power source, wherein the AC / DC conversion means has a certain time interval when a load or a rotation speed of the electric motor changes. And a voltage command device for changing the DC voltage command value so as to change the DC voltage command value so that the power supply current or the electric power approaches a constant value with the passage of time. 8. The invention according to claim 4, wherein a detecting means for measuring a direct current supplied to the inverter is provided, and when the load or rotation speed of the electric motor changes in the alternating current to direct current converting means, at a certain time interval. An electric motor drive device comprising: a voltage command device that changes a DC voltage and changes a DC voltage command value so that a change width of the DC current approaches a constant value with time. 9. An air conditioner configured to drive a compressor electric motor by using the electric motor drive device according to any one of claims 1 to 8.