JP3494928B2 - Inverter control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an instantaneous current value control.
The present invention relates to an inverter control device. [0002] 2. Description of the Related Art Current control is performed on a PWM inverter.
Inexpensive general-purpose inverters do not exist, but high accuracy and high speed
In order to control the response, instantaneous current value control is needed.
Become. The instantaneous current value control device has (1) power
Current control circuit + PWM control circuit, (2) Instantaneous current value control type
PWM control circuit. The dq-axis current control and the triangular wave comparison PWM control
The combination is a typical control configuration of (1). dq
Shaft current control enables high-frequency current without increasing the control gain.
An excellent current control method that can control the steady-state deviation of
You. On the other hand, triangular wave comparison PWM control is excellent in harmonic reduction
The instantaneous current value control by this combination is currently widespread.
Commonly used. However, high frequency current is controlled by dq axis current control.
In order to control, a margin of voltage is required. Turn the motor high
High voltage as much as possible for efficient operation
It is desirable to apply
One-pulse square-wave operation that can be used for the ideal is ideal. Only
However, in dq-axis current control, to avoid saturation of the current controller
Voltage command of a considerably lower value than 1 pulse square wave voltage
The whole area PWM control must be performed using the value. [0005] For this reason, compared with the one pulse square wave operation,
Inefficiency at high rotational speeds and current response speed
Is limited by the triangle wave frequency of the triangle wave comparison PWM control
There is also a problem that it is. That is, the frequency of the triangular wave is
The switch is determined in consideration of the switching loss.
The slower the triangular wave frequency, the slower
The response is also low. An alternative to the instantaneous current value control type PWM control (2)
A typical method is the hysteresis comparator method shown in FIG.
You. This method uses dq axis current control and triangular wave comparison PWM control.
One-pulse square wave operation, which is impossible with your combination, is possible
High-speed current response even with slow switching elements
Have the advantage of being [0007] The figure about the hysteresis comparator system
5 and FIG. Figure 5 shows the hysteresis
Current control of voltage source inverter using comparator method.
It is a block diagram of an apparatus. In FIG. 5, a hysteresis comparator
The current control device of the voltage type inverter using the
DC power supply 1 that supplies power to the barter 3 and harmonic current
Filter capacitor 2 that suppresses voltage changes due to
Inverter that receives voltage Vdc and outputs three-phase AC voltage
Data 3. [0009] The inverter 3 has a structure such as an IGBT.
Self-extinguishing type switching element and anti-parallel connection
Switching elements U, V,
It is composed of W, X, Y and Z. U of inverter 3
Phase output, V-phase output, W-phase output and DC power supply plus side
The elements U, V, and W are between them, and the elements X and V are between them and the minus side.
Y and Z are connected. And the inverter 3
AC power having an arbitrary frequency is output to the AC motor 4
Is done. [0010] Further, the device is provided with an AC power supply from an inverter 3.
The current detection signal iU, which is proportional to the three-phase current flowing through the motive 4,
current detectors 5U, 5V, and 5W that output iV and iW,
The current detection signals i from the current detectors 5U, 5V, 5W
Three phases set by U, iV, iW and setting device (not shown)
Current reference signal iU^* , IV^* , IW^* And take the difference
Current deviation ΔiU (= iU^* −iU), ΔiV (= iV^*
−iV), ΔiW (= iW^* −iW)
6U, 6V, 6W and the subtracters 6U, 6V, 6W
Of the current deviations ΔiU, ΔiV, ΔiW of
If the value is between the value H / 2 and -H / 2, the logic signal being output is
Hold, and if greater than H / 2, change the output to logic signal 1.
If it is smaller than the predetermined value -H / 2, a logical signal 0 is output.
Hysteresis comparators 7U, 7V, 7 for changing force
W. Hysteresis comparators 7U, 7V, 7
The logic signal (PWM signal) output by W is
Of the elements U, V, W on the plus side of the inverter 3
It is used as the ching signals SU, SV, SW. Also,
Output from hysteresis comparators 7U, 7V, 7W
The polarity of the logic signal is inverted by the NOT logic circuits 8U, 8V, 8W.
The signals X, Y, Z on the negative side of the inverter 3
Used as the switching signals SX, SY, SZ
You. Switching signals SU, SV, SW, SX, SY,
SZ is a dead time processing circuit and gate amplifier (both figures
, Etc.), the corresponding switching element U,
V, W, X, Y, and Z. Next, the operation principle of the above-described current control device will be described.
This will be described with reference to FIG. Note that in FIG.
Only one phase (U phase) will be described. Figure 6
And the current reference iU that changes sinusoidally^* Is drawn with a solid line
ing. Above and below, breaks drawn in parallel across H / 2
The line is the boundary of the allowable error region of the U-phase current iU. As shown in FIG. 6, immediately before timing t0.
Then, the PWM signal SU is 0 and the U-phase current iU is decreasing.
You. At the timing t0, the current iU becomes (iU^* -H
/ 2) When the line is reached, the hysteresis comparator
The data 7U operates and SU becomes 1. With this,
Since the positive voltage of the DC power supply 1 is applied to the U-phase terminal of the machine,
The current iU starts to increase. Current iU is current reference iU^* To
Even if it exceeds, the hysteresis comparator 7U does not operate.
No. At the timing t1, the current is changed to the hysteresis comparator.
7U operation level (iU^* + H / 2), S
U becomes zero. Negative DC power supply 1 to the U-phase terminal of the motor
As pressure is applied, the current iU moves to decrease. Thereafter, the hysteresis control is performed as in t2 and t3.
Each time the operating level of the parator is reached, the PWM signal
Instead, the direction of change of the current changes. As a result the current deviation
Is controlled to be within ± H / 2. The neutral point of the motor winding and the DC voltage of the inverter
If the middle part of the source is connected, the above explanation is correct
However, actually, the neutral point of the motor winding and the inverter
Not connected. Therefore, the switching state of the other phase
Affects the current change. In particular, SU = SV = SW = 1, or
Or if SU = SV = SW = 0, U phase, V phase, W phase
Since the terminal voltages of all phases become the same potential, the current
The direction of change is determined by the internal induced voltage of the motor. Current
iU is SU = 1 depending on the angle of the internal induced voltage.
It decreases even if SU is 0. FIG. 7 shows a hysteresis comparator system.
This shows the simulation waveform of the current control by
You. In FIG. 7, the current reference iU^* The solid line
The allowable error area is indicated by dotted lines above and below. Tolerance
It generally fits within the error area and repeats increase / decrease
Is the U-phase current iU. Below that, the PWM signal S of each phase
U, SV, and SW are shown. Phase current iU and PWM signal
A vertical dashed line with the SU signal indicates a change signal of the SU signal.
Imming. As shown in FIG. 7, when SU = 0 and iU becomes (i
U^* −H / 2), or SU = 1
And iU becomes (iU^* + H / 2)
U changes. When SU changes, the change direction of iU changes
PWM signal that keeps the current iU within the allowable error region.
Signal is output. Until time t1, U-phase current iU and P
The WM signal SU operates as described with reference to FIG.
I have. Immediately after time t1 when SU changes from 0 to 1
IU is also increasing. However, when both SV and SW become 1
At time t2, although i is 1, SU is equal to iU.
It is starting to decrease. At time t3, iU becomes (iU
^* -H / 2). At this time, if SU = 0, SU
= 1, but already SU = 1. phase
The current iU continues to decrease, and the SV at time t4
Changes from = 1 to SV = 0 only increase
ing. As described above, the current deviation is determined by the hysteresis width ± H.
The hysteresis con
This is because the width of the tolerance area of the parator method changes.
You. This will be described in detail with reference to FIG. FIG. 8 is drawn perpendicular to the U-phase axis.
Of the three straight lines, the solid line represents the current deviation Δ
A line where iU is zero, above and below it, separated by H / 2
The dashed line drawn on the line is the boundary of the U-phase
You. Similarly, three V-phase and W-phase orthogonal to each axis
A parallel line indicates an allowable error area. In the figure, (H,-
H / 2, H / 2) are UVW coordinates
The coordinates of that point in the system. If the explanation given with reference to FIG. 6 is correct,
In the hysteresis comparator method, iU, iV, iW
Must fall between the criteria ± H / 2. this
In this case, the current deviation is the allowable error of each axis of UVW in FIG.
Hexagon, top formed by intersection of difference areas (hysteresis width)
The coordinates of the point are (H / 2, -H / 2, 0), (0,-
H / 2, H / 2), (H / 2, 0, H / 2), (-H /
2, H / 2, 0), (0, H / 2, -H / 2), (H /
2,0, -H / 2).
Will be. However, actually, the small triangular area outside the
Are included in the allowable error region. Besides, it is troublesome small three
The square area becomes an allowable error area depending on the switching state.
Included or not included. Hexagon and outside it
The area that includes both the six small triangles that are in contact
It is called a “hexagonal region”. Vector state generated by the output voltage of the inverter
Are classified into zero vectors and non-zero vectors. Zerobe
A vector is a signal in which all three-phase PWM signals have the same value,
SU = SV = SW = 1 or SU = SV = SW = 0
Case, otherwise a non-zero vector. Output power
If the pressure is a non-zero vector, the small triangle is the tolerance region
Not included. When the PWM signals SU, SV and SW are all 1
Yes, the induced voltage is at an angle that increases the U-phase current deviation
And In this case, the current deviation increases (H / 2,
V, W) line (where V and W are arbitrary values)
The hysteresis comparator 7U operates,
The PWM signal SU changes to 0. Only negative for U-phase motor
Since a positive voltage is applied to the voltage, V phase, and W phase, the phase current
The voltage state is in the direction to decrease iU. That is, the line of (H / 2, V, W) is allowable.
Functions as a boundary of the error region. However, PWM communication
When the signals SU, SV and SW are all 0, the current deviation increases
The line of (H / 2, V, W)
The cis comparator 7U does not operate. Therefore, the current deviation continues to increase as it is.
You. In this case, the (H / 2, V, W) line is
Does not function as the boundary of the difference area. Further current deviation
And cross the line of (H / 2, -H / 2, W)
At this time, SV changes from 0 to 1 and (H / 2, V, -H /
When going over line 2), SW changes from 0 to 1.
This causes the voltage to reduce the U-phase axis component of the current deviation.
It becomes a direction to decrease. That is, all of the PWM signals SU, SV, SW are
0, (H, -H / 2, -H / 2), (H /
2, -H / 2,0), (H / 2,0, -H / 2)
Is included in the allowable error area,
If U, SV and SW are all 1, this small triangular area
Is not included in the allowable error region. That is, the output voltage is zero
In the case of torque, a small triangular area depends on the switching state.
May be included in the allowable error region. The same thing elsewhere
This can also be said for the five small triangle areas. This result shows that the current ripple is large as shown in FIG.
It appears as a phenomenon that becomes smaller and smaller. I
In fact, the angle of the induced voltage is
6 times the fundamental frequency of the current,
5th and 7th heights that are the most problematic for motors driven by motors
It causes harmonics. Further, the rate of change of the current has changed from FIG.
You can also see that Zero vector period from t2 to t4
Is clearly slower than the current change before t0. Ze
Since the current change during the vector period depends only on the induced voltage,
Current change speed of motor with low induced voltage in low speed range
The degree is extremely moderate. Moreover, as described above, the allowable error area is wide.
It becomes a zero vector period to become. The tolerance area is
The current becomes wider during the zero vector period where the current
It narrows during the non-zero vector period in which steepening occurs. as a result
The fluctuation of the switching frequency is very large. The hysteresis comparator method has been described earlier.
Very few special uses at the moment despite such advantages
The current ripple is not used except for
If the switching frequency is set to the same level as the comparative PWM,
That the wave number increases, that is,
The switching frequency suddenly changes, producing a harsh noise.
This is due to drawbacks such as being born. Switching state
Variations in the size of the tolerance zone due to
It is clear that it has become a thing. Advantages of hysteresis comparator system
However, large harmonics and large switching frequency fluctuations
Many attempts have been made to eliminate such drawbacks.
These improved methods use the hysteresis comparator method.
With the tolerance comparator unit
The voltage vector selection logic unit is separated. The tolerance comparator has a hysteresis
This is an alternative to the comparator-type hysteresis.
It is provided to limit the switching frequency. Tolerance
The switch from the comparator to the voltage vector selection logic
When a switching request is issued, the voltage vector selection logic
The power that seems optimal at the time
Select and output pressure vector. "Enables harmonic suppression and high-speed current response
Current-controlled PWM inverters: Satoshi Ogasawara, Toshiaki Nishimura,
Shinfumi Akagi, Akira Namba (Transactions of the Institute of Electrical Engineers of Japan, B, February 1986
Month issue) is "switching method that can suppress harmonics"
Switching method with "switching method capable of high-speed tracking"
It is described about. "Switching method capable of suppressing harmonics"
Uses a vector with a small current change rate to select the voltage vector.
Current ripple reduction and switching
Prevents sudden changes in the switching frequency. This is the current change
Control only for steady state where gentle is desirable
Method for controlling transient conditions that require rapid current changes.
Is not suitable. For this reason, the tolerance range is doubled and the current
When the difference becomes larger than the external tolerance, the conventional hysteresis
Voltage vector selection logic equivalent to the cis comparator method
Operate with the "switching method capable of high-speed tracking"
The deviation is returned to the internal tolerance area.
You. The permissible error judgment circuit is a composite vector for three phases.
The vector comparator is called a vector comparator.
However, there is a permission equivalent to the hysteresis comparator method.
This is a circuit for obtaining an error area. However, a switching method capable of suppressing harmonics
Comparing only to create a tolerance region with
When using a switching
Because the hysteresis width is narrower than
Of tolerance region in controllable switching system
Has been reduced. However, depending on the switching method
Changing the hysteresis width itself creates a new harmonic.
It causes wave generation. In the AC current control, the current reference on the dq axes is
Is constant, the current reference on the UVW axis is sinusoidal
Is changing. As the rotation speed increases, the current on the UVW axis
While the reference changes faster, the induced voltage increases and the
The difference between the magnitude of the non-zero vector of the barta output voltage is small.
The current change due to the non-zero vector is slow.
You. If the current reference changes faster and the current changes slower
Following is worse, and it is difficult to control the current deviation to a small value.
It becomes difficult. The current deviation increases as the rotation speed increases.
Go on. In this process, the current deviation is for the steady state.
In the steady state
Even so, a switching method that can follow at high speed is required
Swell. High-speed tracking switching method and harmonic suppression
In the rotation speed range where the controllable switching method is mixed
Difference in hysteresis width due to switching method is harmonic
Will be the source of When the number of revolutions further rises, high-speed following is possible.
Control is performed only by the switching method. Stated earlier
In the case of solid dq axis current control and triangular wave comparison PWM control, the constant
If the normal deviation cannot be reduced to zero, the PI controller will saturate and
The current control circuit stops functioning. In such a state
Indicates that the current reference has changed and the current deviation has increased further.
However, since the PI controller is already saturated, the PWM standard
Also does not change. In other words, just because the current cannot be controlled
Therefore, PWM control cannot be performed. However, a switching method capable of high-speed tracking
Expression (a method equivalent to the hysteresis comparator method)
The current deviation is too large for current control.
PWM control according to the current deviation even in the rotational speed range
The waveform changes accordingly. This makes one pulse square wave
It is possible to perform PWM control while controlling the current waveform until operation
it can. To completely eliminate fluctuations in the tolerance range
Is a simple comparator instead of a hysteresis comparator.
8 to create a hexagonal area or a circular area as shown in FIG.
Just do it. In the circular area, the length of the current deviation vector is
Fully constant control, more favorable from the harmonic surface
No. Japanese Unexamined Patent Publication No. Hei 1-259761, "Voltage Source A"
For Steady State in "Inverter Current Control Method"
Control, so that a hexagonal or circular tolerance area
Judgment is employed. By this tolerance judgment method,
Allowable error in the range of low motor speed and low induced voltage
Generation of low-order harmonics caused by fluctuations in the area can be solved.
This method also has a voltage base with a small current change rate in the steady state.
The point that it is based on the choice of
In the transient state, the control method is switched to another control method. However, there is only one allowable error area, and the current
When the deviation reaches a predetermined level outside the tolerance range,
The vector selection logic has been switched for the transient state. This method
In the case of, a problem different from the variation of the allowable error region occurs. High
As the current deviation increases with rotation, there is no
The control method starts to operate steadily. Transient of this method
Voltage selection in the state is based only on the angle of the current deviation
The hysteresis width from the hysteresis comparator method.
It can be said that it has lost. Moreover, the allowable error area
Because it is just a circular shape, current deviation is
If it does not fit in the difference region, the selected voltage vector
This is reflected on the inverter output voltage. As a result,
High-frequency switching is performed. This example is shown in FIG.
You. In FIG. 9, between t1 and t2, the PWM signal
Only the signal SU changes at a high speed,^* Control equal to
Have been. However, during this time, iV and iW
It is not shown in FIG.
And the deviation of the U-phase current before t1 and after t2 is large.
It is obvious from. The switch with the smallest current deviation is
Only the phase that is running. SU = 1, SV = 0, SW
= 1 and SU = 0, SV = 0, SW = 1
It appears alternately, but outside of the allowable error range in either state.
You. The allowable error region controls the switching frequency.
Hysteresis comparator type hysteresis
Should have been set up as a replacement for the Sith,
In that case, it does not fulfill its role. Moreover, the current deviation vector
Because it is outside the permissible error circle for Torr, it is not very meaningful
There is no high frequency switching. Current deviation due to transient phenomenon
If it increases temporarily, high-frequency switching is also temporary
However, if the current deviation constantly increases at high rotation speed,
High frequency switching continues and switching loss sharply
To increase. In the case of the hysteresis comparator system,
Since the switching frequency is limited by the hysteresis width,
Such a situation does not occur. Hysteresis comparator
The permissible error area of the method is originally held by the comparator of each phase.
In the hysteresis and circumscribes the hexagonal area
The small triangular area is the overall operation of the three-phase voltage source inverter.
Are the resulting tolerance regions that appear. For high rpm
The current deviation can be contained in these areas.
Even if it disappears, switch with hysteresis for each phase
Limit the switching frequency. That is, iU> iU^* SU once at + H / 2
When it becomes 0, the next SU becomes 1 is iU <iU^* -H
/ 2 only. Therefore, iU is H / 2
Switching is prohibited only for the time it takes to change
The upper limit of the switching frequency is determined. [0049] SUMMARY OF THE INVENTION A hysteresis comparator
The hysteresis of the motor system has an allowable error in the low speed range.
The magnitude of the current ripple is changed by the area fluctuation.
However, in the high speed range, the switching frequency
It plays the original role of limiting the wave number. In a simple circular tolerance region, a high rotational speed region is used.
If the current deviation goes out of the range completely,
The function of limiting the switching frequency is lost. So
Here, the present invention is applied to a case where the PWM
Control to keep the current deviation within the allowable error range
If control is possible, the size of the tolerance area will change
Current deviation, as at high motor speeds.
If control cannot be performed within the tolerance range,
Limit the switching frequency of the motor
Inverter control device that can realize stable control over the whole area
The purpose is to obtain the position. [0051] Accordingly, the above object has been achieved.
In order to achieve this, the present invention provides that the current deviation of the polyphase alternating current is
Output switching request if condition is not met
The tolerance judgment means and the switching request
Select output voltage vector to reduce current deviation
Voltage vector selecting means for outputting the corresponding PWM signal
And PW output from the voltage vector selecting means.
Inverter control that controls the inverter based on the M signal
In the device, if the current deviation for each phase is within a predetermined value
Allowed, even if it is out of the predetermined value, by the PWM signal of the phase
Is a band-shaped tolerance area with allowable hysteresis and
Intersecting with the band-like tolerance area that exists for the number of phases
Radius just to include at least the formed star polygon region
The circle or diameter polygon area is also used as the tolerance area, and the current
The specified condition that the deviation is included in the allowable error area
And an allowable error determining means. In the present invention configured as described above,
Current deviation falls within a circle of radius H or polygonal area of diameter S
Is outside the star hexagonal area.
Range, so that the current
In the controllable operating region, the magnitude of the current deviation as a vector
Is controlled so that the maximum value of the radius is equal to or less than the radius H or the radius S.
Is done. Uniform magnitude of current ripple as vector
Will be controlled. The current deviation is allowed as in the case of the high rotation speed of the motor.
If you can no longer fit within the error circle,
In the allowable error area given by the width of radius H or diameter S for each phase
Therefore, the switching frequency of the element is limited. [0054] Embodiments of the present invention will be described below.
This will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention.
1 shows a configuration of an inverter control device in a state. Figure 1
And 1U to 6U, 6V, 6W and 8U, 8V, 8W
5 are the same components. As shown in FIG. 1, the embodiment of the present invention
The inverter control unit outputs the subtractors 6U, 6V, and 6W.
Current deviation ΔiU, ΔiV, ΔiW
Judge whether it is within the range of a predetermined allowable error, and as a result
As a switching request (voltage vector update request)
Allowable error code output to voltage vector selection circuit 11
It has a comparator 10. The voltage vector selection circuit 11 has a tolerance
In addition to the output of the judgment circuit 10, the current deviations ΔiU, ΔiV,
ΔiW is also given. In the voltage vector selection circuit 11
Is the voltage vector being output held in the selection circuit 11 or
Or the voltage vector information and the current deviation previously output
Voltage vector to keep the current deviation within the allowable range
Is selected. However, the switch from the allowable error determination circuit 10
The switching request is controlled by the selection operation of the voltage vector selection circuit 11.
It works as a control signal and when there is no switching request,
Do not perform the selection operation or do not update the result even if selected.
PWM system to avoid unnecessary switching
Control device. FIG. 2 shows an allowable error comparison of the present embodiment.
FIG. In FIG. 2, 20 is an allowable error.
The difference setting value H, 21 is a multiplier that outputs の of the input value.
It is. 22U, 22V, 22W, 22X, 22Y, 2
2Z is a comparator whose output of the multiplier 21 is
Any one of the current deviations ΔiU, ΔiV, and ΔiW is input to the input.
Is given to the other input. Comparators 22U, 2
2V, 22W is the current deviation given as one input
Is larger than the allowable error setting H / 2 given as the other input.
Outputs logical value 1 if it works and logical 0 otherwise
You. The comparators 22X, 22Y, 22Z
If the value of the current deviation given as one input is negative,
Absolute value is the allowable error set value H given as the other input
Logical value 1 if greater than / 2, logical value otherwise
Outputs 0. 23U, 23V, 23W, 23X, 23
Y and 23Z are AND circuits, each having one input.
As comparators 22U, 22V, 22W, 22
Output of the corresponding comparator among X, 22Y and 22Z
The signal is the switching signal being output as the other input
SU, SV, SW are AND circuits 23X, 23Y, 23Z
To the AND circuits 23U, 23V, 23W
Polarity at NOT logic circuit 24U, 24V, 24W respectively
An inverted signal is provided. AND circuits 23U, 23V, 23W, 23
The outputs of X, 23Y, and 23Z are input to an OR circuit 25,
All are ORed. The above components 20 to 25
Equivalent to the conventional hysteresis comparator method
Error region having the allowable error region of FIG.
A difference determination circuit is configured. 26U, 26V, 26W are multipliers,
The current deviations ΔiU, Δi
V and ΔiW, the current deviation of the corresponding phase is
Given, the output is the square of the current deviation. Squared
The outputs of the arithmetic units 26U, 26V and 26W are
The phase components are added, and as one input of the comparator 28
Given. Allowed as the other input of comparator 28
A value obtained by taking the square of the error set value H by the multiplier 29 is given.
You. Comparator 28 ΔiU^Two + ΔiV^Two + ΔiW^Two > H^Two In this case, a logical value 1 is output. Otherwise, a logical value 0 is output. Up
Taking the square root of both sides of the equation, SQRT (ΔiU^Two + ΔiV^Two + ΔiW^Two )> H What the comparator 28 performs is the current
Whether the magnitude of the deviation vector falls within a circular area of radius H
It is a judgment of whether or not. The outputs of comparators 25 and 28
AND circuit 30 takes the final AND
Output as a signal. FIG. 3 shows voltage vector selection according to this embodiment.
2 is an example of a circuit 11. The voltage vector selection circuit 11
Select and output voltage vector based on current deviation status
Circuit, which corresponds to the improved method shown as the conventional example.
As in the part, the induced voltage, the voltage vector during output, and
Is used to select the output history of the voltage vector, etc.
May be used. FIG. 3 shows the simplest voltage vector selection circuit.
In this example, the current
The voltage vector is selected only from the difference. In FIG. 3, 4
0U, 40V, 40W are zero comparators,
Each input signal ΔiU, ΔiV, ΔiW is compared with zero voltage.
Outputs 1 if greater than zero, 0 otherwise
You. 41U, 41V, and 41W are D latch circuits.
B The output of the comparators 40U, 40V, 40W is the data
The input is given to the D input terminal. Output signal CTL of allowable error determination circuit 10
Are the control input terminals of the D latch circuits 41U, 41V and 41W.
It is provided to the child G and controls the operation of the D latch circuit. output
If the signal CTL is 1, the D latch circuit inputs data
The signal is output to the output terminal Q as it is. Output signal CTL is 1
When it changes from 0 to 0, the D latch circuit outputs 1 of the output signal CTL.
Holds the Q terminal output signal at the time of the change from 0 to 0
You. The output of the D latch circuits 41U, 41V, 41W is PW
The signals are output as M signals SU, SV, and SW. Zero Comparator of the Voltage Vector Selection Circuit of FIG.
Voltage vectors output by the radiators 40U, 40V, 40W
Delays the state of the current deviations ΔiU, ΔiV, ΔiW
The hysteresis comparison
Data method. Next, the operation of the PWM control device of FIG. 1 will be described.
2. Explanation based on the figure of the allowable error area in FIG. 3 and FIG.
I do. The hysteresis of the allowable error determination circuit of FIG.
Refer to the hysteresis of the
It is made. The configuration of the hysteresis comparator system is shown.
In FIG. 5, the hysteresis comparator 7U
Regarding the flow deviation ΔiU, the range of −H / 2 <ΔiU <H / 2
Has a hysteresis width, and the current deviation ΔiU
Operates when out of range. Therefore, the hysteresis comparator 7U
When the output SU is 0, the current deviation ΔiU is less than H / 2.
When it becomes larger, the output SU changes to 1. But once
After SU = 1, ΔiU decreases and −H / 2 <Δi
Return to the range of U <H / 2, and then larger than H / 2 again
When it becomes low, the output of the hysteresis comparator 7U
The force is unchanged since SU = 1 already. The output of AND circuit 23U in FIG. 2 becomes 1.
This is because the hysteresis comparator 7U operates and outputs
A set of a current deviation and a PWM signal corresponding to a change in force
When the matching condition is satisfied, that is, ΔiU (= iU^* −
iU) is greater than H / 2 and comparator 22U
Only when the PWM signal SU is 0 when outputting
It is. If the PWM signal SU is 1, the comparator 22
Even if U outputs 1, the output of AND circuit 23U does not become 1.
No. Similarly, the output of the AND circuit 23X becomes 1
Is ΔiU (= iU^* -IU) is smaller than -H / 2
PWM when the comparator 22X is outputting 1
Only when the signal SU is 1. As a result, the current deviation Δ
FIG. 5 shows that the output of the OR circuit 25 becomes 1 with respect to iU.
The output of the hysteresis comparator 7U changes
Combination of the same switching state and current deviation state as
Holds when the hysteresis comparator method is used.
Will have the same hysteresis. V phase, W phase
The same applies to the case. Further, multipliers 26U, 26V, 26W,
The current is calculated by the calculator 27, the multiplier 28, and the comparator 29.
The length of the combined vector of the deviations ΔiU, ΔiV, and ΔiW is
If the radius H is not exceeded, the output of the AND circuit 30, that is,
The output of the error comparator should not be 1
You. Assume that there is a current deviation vector at point A in FIG.
You. Point A is -H / 2 <ΔiW <H / 2.
The outputs of the AND circuits 23W and 23Z are both zero.
But iU> iU^* + H / 2, that is, ΔiU <−H / 2
Therefore, if SU = 1, the output of the AND circuit 23X becomes 1.
Become. Also, iV <iV^* −H / 2, that is, Δi
Since V> H / 2, the output of the comparator 22V is also 1
If SV = 0, the output of the AND circuit 23V becomes 1.
You. The current deviation is larger than the star hexagon,
Assume that the inverter output voltage is a zero vector
And SU = SV = SW, the AND circuits 23X, 23
One of V is 1. Therefore, the output of the OR circuit 25 becomes 1.
A tolerance judgment equivalent to the conventional hysteresis comparator method
If the voltage vector selection
The amount of current deviation that gives a switching request to the path
is there. In the present invention, the comparator 29 controls the current deviation.
Whether the length of the vector is greater than H, that is, the radius in FIG.
It is determined whether or not it is within the circle of H. Point A is within the circle
Therefore, the output of the comparator 29 is 0, and the OR circuit 25
Even if 1 is output, the output signal of the AND circuit 30 is 0. Therefore, the PWM signal is unchanged and the current is
Continue the same changes as before. Boundary of circle with current deviation radius H
When the point A 'on the field is reached, the output of the comparator 29 becomes 1
And a switching request is issued from the AND circuit 30.
Is forced. A comparison of the voltage vector selection circuit of FIG.
Considering the data output, the current vectors are point A, point A '
IU> iU^* That is, ΔiU <0
Therefore, 40U is 0, iV <iV^* That is, ΔiV> 0
And 40V is 1, iW> iW^*In other words, since ΔiW <0,
40W is 0. Therefore, given the switching requirements
Then, the D latch circuits 41U, 41V, 41W operate.
Thus, SU = 0, SV = 1, and SW = 0. Thus, when the inverter is operated, the V phase
Only positive voltage, negative voltage is applied to U phase and W phase,
It becomes a voltage vector that changes the V-phase current in the positive direction.
The flow will change in the reference (origin of coordinates) direction.
You. Conventional Hysteresis Comparator Comparable
In the case of the system, the voltage vector
Switching request is issued to the
However, in the determination circuit of FIG. 2, A is included in the allowable error area.
Therefore, the switching requirement is that the current deviation is A on a circle having a radius H.
Postponed until point 'is reached. The circle of radius H is the conventional hiss
Includes star-shaped hexagonal region of the teresis comparator type
Therefore, the star-shaped hexagonal area
If the current deviation could be contained in the
The current deviation can be contained in a circle of radius H by the method
You. The length of the current ripple three-phase composite vector is restricted to H
The current lip as in the conventional example of FIG.
The size of the rule does not change. Switching cycle
Wave number fluctuation is smaller than the hysteresis comparator method
Become. The voltage vector selection circuit has hysteresis.
The voltage vector based on the past state of the current deviation.
Is selected based on the current deviation state.
A different vector is selected. This is hiss
For the switching frequency of the teresis comparator method
Is one of the drawbacks that the current ripple cannot be reduced.
It was also a factor. In this embodiment, the voltage vector selection circuit
Has no hysteresis, and the allowable error determination circuit shown in FIG.
Hysteresis by adding the switching condition to the
Has a lysis. The circuit of FIG. 3 includes comparators 40U, 40
Even if the output of V and 40W changes, the tolerance
If no switching request is given, the PWM signals SU, S
V and SW do not change. From the allowable error determination circuit shown in FIG.
Flow deviation is iU> iU^* + H / 2 and SU = 0
And iU <iU^* Until -H / 2, U phase current deviation
No switching request is output. Therefore, in FIG.
Switching frequency rises abnormally at high speed
Can be avoided. And voltage vector selection
Since the circuit has no hysteresis, the voltage
Vector selection requires switching from the tolerance judgment circuit.
Based on the current state of the current deviation at the time the
Is According to the present embodiment thus configured,
The maximum current ripple
Value can be controlled to a constant value,
Fast fluctuation can be reduced. By these, the torque of the motor
Ripple, vibration, noise, etc. are improved. Tolerance range
The setting of the area becomes easy. In addition, considering the switching state,
Hysteresis is provided for the difference judgment, so the switch
Operating frequency is limited to avoid abnormal loss increase.
it can. Further, the circular tolerance area and the hysteresis
It is not necessary to intentionally switch between the width and the tolerance area.
Operation mode automatically switches according to the magnitude of the current deviation.
The motor's wide operating frequency range.
A usable allowable error determination circuit can be obtained. Book
In the embodiment, the current control of the electric motor will be described as an example.
However, according to the present invention, the voltage type PW
Applicable to all M inverters. [0087] As described above, according to the present invention, the power supply
As in the case of the low rotation speed of the motive, the current deviation is controlled by PWM control.
If the difference can be controlled to be within the tolerance
Means that the size of the tolerance
The current deviation is within the allowable error range, such as when the machine is rotating at high speed.
Switching of the element when it cannot be controlled to fit
The frequency is limited and stable over the entire operating frequency range of the motor.
Inverter control device that can realize
Wear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. FIG. 2 is a detailed configuration diagram showing an allowable error comparator of the embodiment shown in FIG. FIG. 3 is a detailed configuration diagram showing a voltage vector selection circuit of the embodiment shown in FIG. FIG. 4 is a view for explaining an allowable error area by the allowable error comparator shown in FIG. 2; FIG. 5 is a schematic configuration diagram showing a control circuit of a hysteresis comparator system. FIG. 6 is a diagram illustrating the operating principle of a hysteresis comparator system. FIG. 7 is a diagram showing a simulation waveform of current control by a hysteresis comparator method. FIG. 8 is a diagram for explaining an allowable error region of the hysteresis comparator system. FIG. 9 is a diagram illustrating a high-frequency switching phenomenon without hysteresis. [Description of References] 1 ... DC power supply, 2 ... Filter capacitor, 3 ... Inverter, U, V, W, X, Y, Z ... Switching element, 4 ...
AC motor, 5U, 5V, 5W ... current detector, 6U, 6
V, 6W: subtractor, 7U, 7V, 7W: hysteresis comparator, 8U, 8V, 8W: NOT logic circuit, 10:
Tolerance error comparator, 11 ... voltage vector selection circuit,
20: Set value of allowable error H, 21: Magnifier, 22U, 2
2V, 22W, 22X, 22Y, 22Z ... Comparator, 23U, 23V, 23W, 23X, 23Y, 23Z
... AND circuit, 24U, 24V, 24W ... NOT logic circuit, 25 ... OR circuit, 26U, 26V, 26W ... multiplier, 27 ... adder, 28 ... comparator, 29 ... multiplier, 30 ... AND circuit, 40U, 40V , 40W ... Zero comparator, 41U, 41V, 41W ... D latch circuit

Claims (1)

(57) [Claims 1] An allowable error determining means for outputting a switching request if the current deviation of the polyphase alternating current does not satisfy a predetermined condition, and a current deviation for each switching request is given. Voltage vector selection means for selecting an output voltage vector to reduce the voltage signal and outputting a corresponding PWM signal; and controlling an inverter based on the PWM signal output from the voltage vector selection means. In each case, if the current deviation is within a predetermined value, the current deviation is permitted. Even if the current deviation is outside the predetermined value, a band-shaped allowable error region having hysteresis to be permitted depending on the PWM signal of the phase and the band-shaped allowable error region having the number of phases exist. A circle having a radius or a polygon having a diameter sufficient to include at least the star-shaped polygonal region formed by intersecting Inverter control apparatus characterized by that it contains tolerances region; and a tolerance determination means as the predetermined condition.