JPS58116094A - Current comparison type alternating current power supply device - Google Patents

Abstract

PURPOSE:To lower the speed of revolution of a motor without increasing a torque ripple, vibration and noises by controlling DC voltage at the inverter input side supplied to a main switching element in response to the induced electromotive force of the motor. CONSTITUTION:A vector controller 50 compares signals displaying the speed of revolution of the motor 3 inputted from a speed detector 52 and speed command signals, and generates current command signals with frequency corresponding to these difference. A voltage detector 60 detects the output voltage of a forward converting section 40, voltage Ed as the DC input of an inverter section 2, and supplies the subtracting input of an adding circuit 64 with detecting signals C. A pattern generator 62 uses speed signals V as input, generates voltage command signals D in response to the speed signals, and supplies the adding input of the adding circuit 64 with the signals D. The output of the adding circuit 64 is inputted to the forward converting section 40 through an error amplifier 66 and a phase shifter 68, and the DC output voltage Ed of the forward converting section 40 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AC power source device 41 used for rotational speed control 11 of an AC motor such as a -4'WL motor, and an AC power supply device 41 of a speed ratio plate type inverter type.

For example, AC motors such as rice-carrying electric motors have the advantages of simple structure, long life, easy maintenance, and relatively low cost. (Although it is used, conventionally there was no method to efficiently control the Ig1 rotation speed, so its applications are limited, and even in applications where speed control is preferable,
In order to take advantage of the advantages mentioned above, it has been used without simultaneous rotation speed control.

However, in recent years, various semiconductor electronics have been provided, and an AC power supply consisting of a static inverter that can obtain an output of any frequency regardless of the frequency of the commercial power supply. A device has appeared that can falsely obtain effective rotational speed control by changing the frequency t of the power supply supplied to AC motors (hereinafter simply referred to as motors) such as nzm conductive motors. It's here.

As this AC power supply device, a current ratio plate type AC power supply using a pulse width M (PWM) type inverter as described below is known.

11t! Figure 1 shows an example of the main circuit of the above-mentioned conventional device, where 1 is a stone conversion section (AC/IL flow conversion section), 2 is an inverter section (inverse conversion section), 3 is a motor on the drive side, and 4Vi current detection. 10 to 15 are rectifier diodes, 16Fi smoothing capacitors, 20 to 25 are main switching elements consisting of transistors, gate turn-off thyristors, etc.
26 to 31 are flywheel diodes.

The converting section 1 is formed by a three-phase full-wave rectifier circuit consisting of diodes 10 to 1B, and is connected in the form of an inverter@2Vi bridge between the terminals of the n1 smoothing capacitor 16 to generate a DC voltage with less pulsation. Each of the main switching elements 20 to 25, which are composed of main switching elements 20 to 25 with f' and diodes 26 to 31, constitute a PVv'M type inverter.
'1. is controlled on and off at a predetermined timing, and the DC voltage supplied from the forward converter 1 via the smoothing capacitor 1ε is switched from K to supply a 3-phase PWM AC current to the motor 3. 6 11fIL detection-4 detects the current flowing through each phase of the motor 3, and generates a current tIL detection signal.
A 5-control m circuit that performs on/off 1111 control will be explained with reference to Fig. 2.The second problem is shown only for the control m circuit for one phase, and 15 is an addition path (comparison path); 6 is a threshold circuit (hysteresis comparator), 7.8 is a drive path, and S is a current/voltage converter.

Addition power of addition circuit 5 K11l inno (-ta s1 (m
il commanding the temporary value amount (sine wave) of the output current (1)
E flow command number A is supplied, and signal B, which will be described later, is supplied to the subtractor, so the difference between them, number 01 C, or the output of the adder circuit 5 is rL 1, which is the threshold value circuit. 6 is addition circuit 5
A circuit that outputs a switching signal S when the signal C from the input signal CVr reaches a predetermined value or more, and outputs the switching signal S until the signal C reaches a predetermined value or less, and provides a predetermined nohysteresis width δ to the input signal CVr. It is set to work.

Drive planes w & 7 and 8 are input signals S, respectively.

S is amplified and supplied to the main switching elements 20 and 21 L,
Contra 17) A 1,20t21t'+g9S, 8 to turn on and off according to the expansion.

The current/voltage converter 9 converts the current detection signal & from the Kagoryu Kendamasu 4 into a voltage, generates a voltage signal B, and sends the voltage signal B to the adder circuit 50.
The signal that is supplied to the subtraction input is - Note that ■ represents the tAt, n, and η of the motor 3. Therefore, the voltage signal B represents the 11 current I of the motor 3 in terms of voltage. ing.

Next, the operation of the conventional device will be explained with reference to FIGS. 30) to e9.

Figure 3 0) is 11. This figure shows the waveforms of the current command signal A and the voltage signal B. In the same figure, ← indicates 8 to the switching point, and 4 times 39 indicates the switching external force S, and the addition circuit 5 The current command signal ^ and voltage signal B
As a result of manually inputting the signal C of the difference between them to the threshold circuit 6, the voltage (at No. 1 B or current command A predetermined value (
J/2), the switching signal S appears and the switching signal S disappears, and then when the signal SFi reaches a predetermined value (a/2) or more than the signal B or the signal A, the signal SFi disappears (the signal S Therefore, these switching signals 8.8 become as shown in Figure 3) and (c).

Therefore, if the main switching element 20 is currently on, the current of the motor 3 is controlled by f'LK in the direction of increasing, so the voltage signal B increases and eventually the current command signal A When it is more than a72, the main switching element 20 turns off, and conversely, the main switching element 2 turns off.
1 turns on. As a result, now F! L is the current of motor 3■
The voltage signal B decreases because the current command (Khj) is controlled in the decreasing direction Khj, and when the current command (e1M & 11a
I is controlled in the direction of increasing again - From this K, 1 flows into the motor 3! Current ■ is current command signal g
The waveform shown by the voltage signal B is controlled in accordance with h, and any waveform having a predetermined transition value, preferably a sine wave, can be supplied as the current command signal A.
A corresponding sine wave [fiI] can be supplied to the motor 3, and an alternating current of any frequency can be supplied to the motor 3 according to the current command signal A.

The above is an explanation about the l-phase component, and in reality, the main switching element 20.21 alone is fc < 22~2
Similar control is performed for motor 3, so if a current command signal having a four-phase relationship with the three-phase alternating current is supplied to each regulation circuit, three-phase alternating current will be supplied to the motor 3. By changing the frequency of the current command signal, the rotational speed of the motor 30 can be controlled arbitrarily.

By the way, in the above-mentioned conventional device, the deviation width of the current command signal AK (deviation width of the voltage S, that is, the output
The deviation of - is determined by the hysteresis width δ given by the threshold series circuit 6 and #L311
As is clear from W(a), the smaller the above deviation width, the better the waveform force of the output current, so it is desirable to make this hysteresis width as small as possible.

However, on the other hand, the switching frequency of the main switching elements 20 to 25 is also determined by this hysteresis width δ, and as is clear from FIGS. The pulse width becomes narrower and the switching frequency -bL becomes higher.

However, there is an upper limit to the switching frequency of the main switching elements 20-25, and therefore, the hysteresis width 6 cannot be narrowed beyond the -J limit depending on the switching frequency of the main switching elements 20-25.

Therefore, in the conventional #cPI71t described above, the hysteresis -δ of the threshold circuit 6 is determined in consideration of the permissible switching frequency of the main switching elements 20 to 250 used, so as to obtain a practically desirable result.

However, in this Yuzu device, the main switching element 20
The switching frequency of ~25 varies depending on the output frequency of the inverter, that is, the rotational speed of the motor 3, as shown in Figure 4. In other words, the output current of the inverter depends on the output voltage of the inverter and the induced voltage of the motor 3. Since the voltage rises according to the difference between the motor 3 and the electric power, the rate of change with respect to time becomes thicker (and the switching frequency becomes higher) as the induced electromotive force of the motor 3 is smaller and during low rotation.

To explain this in more detail, when the main switching element Q+CM1 of the U assembly arm of the motor 3 (20) in the figure is on, the circuit is as shown in Figure 5. In the figure, E
d is the DC-input voltage of the inverter section 2,
I variable unit 1 conversion force voltage, eI & is the #S rotation force of the motor 3, R, L are the camellia resistance and the inductance of the motor 3, Dl is the flywheel diode of the lower arm of the U digit, and the current is Ii If the direction shown is positive, then d M (1ta = R1 (1) + LL12t) = Δk
・---・-(1) From this, the change in current I with respect to time becomes I(i(,=ct-e-+')-(2).

Therefore, if the change state of the output current expressed by the above equation (2) at time t[H is plotted, it becomes K as shown in Figure @6. In the figure, the curves ``■'' and ``■'' represent the characteristics when ΔEA or nΔE, /几 and Δg, /R, respectively.

As is clear from Fig. 6, the time T for the single output current I to reach the P9r foot value Ix is T8 for the curve ■ and T for the curve ■, and the difference between the time T and TI is is also ΔT. In other words, the larger ΔE becomes,
As the time T becomes shorter, it can be seen that the rise of the output current l becomes more rapid.On the other hand, as is clear from equation (1), this ΔE becomes
and Ed of motor 3 are constant, but voltage c1 is 8147
As shown in the figure, the rotational speed of the motor 3 changes relatively, and therefore, the voltage ΔE has a large value when the rotational speed of the motor 3 is low.

As a result, the time it takes for the output tmI to reach the predetermined value IxK becomes shorter as the rotational speed of the motor 3 is lower, the rise of the output 1 and flow I becomes steeper, and the switching frequency becomes higher.

Therefore, in the conventional device described above, the rating of the motor 3 is 1i.
11. Good control characteristics near the 21 transition point. If the hysteresis width δ of the K-threshold circuit 6 is determined so that the motor 3 is in the sluggish rotation extreme region, the main switching elements 20 to 25 will be in the 7t range. What is the upper limit of the switching frequency that can be switched?
There are drawbacks such as MItr+ and t-, which can result in uneasy QK at one station or the destruction of one main switching ticket. In order to prevent L, the hysteresis width was widened for K, which had the disadvantage that VJ had to be input into an insufficient motion picture.

Therefore, in order to eliminate these drawbacks of the above-mentioned conventional devices, the above-mentioned hysteresis is changed according to the rotation speed of the motor. For example, as shown in Figure 8 on the side, the switching frequency of the main switching element does not increase even in the low rotation speed region. There are suggestions on how to do this. In Fig. 8, characteristic ■ is the case where the hysteresis width is continuously changed according to the rotational speed of the motor and the switching frequency is controlled to be constant, and characteristic 0 is the case where the hysteresis width is changed continuously according to the rotational speed of the motor. This shows the case where the width is controlled to be cut in two steps.However, in this conventional method, the above-mentioned hysteresis becomes wide in the low motor rotational speed range in any case, so the following is explained below. This resulted in the following drawbacks.

(1) In the low speed region, the ripple component increases in the output current and the output current waveform becomes large, leading to an increase in motor torque ripple, vibration, and noise.

(2) Due to the ripple of the output current, regular vector calculation becomes complicated and tends to become a control or IImK.

The purpose of the present invention is to eliminate the drawbacks of the conventional hakama described above and to solve the problem that even if the rotational speed of one motor is controlled sufficiently in the low range, torque ripple, Sm movement, and shaft material increase. There is a current comparison type AC voltage control system which can prevent an increase in the switching frequency of the main switching element.

In order to achieve this object, the present invention is characterized in that the inverter input DC voltage is supplied to the main switching element according to the subsequent electromotive force of the motor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, actual and examples of a current comparison type AC power supply device according to the present invention will be explained with reference to the drawings.

Figure 9 shows an embodiment of the main circuit according to the present invention, in which 40 is a forward converter, 42 to 4T are thyristors, and the others are the first
It is the same as the conventional example shown in the figure.

Each of the thyristors 42 to 41 of the forward converter 40 generates a DC t# voltage Ed between the terminals of the phase-controlled smoothing capacitor 16 in response to a gate signal from a phase shifter, which will be described later. It is designed so that it can be changed over the required range by using the gate f#4.

Next, 50 is a block diagram showing the overall configuration of an embodiment of the present invention, 50 is a vector control proverb, 52 is a ft detection number, 60 is a voltage detector, 62 is a pattern generator, and 64 is an adder circuit. 166 is a scissor difference amplifier, 68 is a phase shifter, and is the same as the other Ayu 9 diagrams.

The vector control device 50 receives a signal V (not shown) representing the rotational speed gi [k] of the motor 3 which is inputted from the speed detector 52 . Compare the command signal and adjust according to their arrival.
It generates a Wt flow command signal A of j wave number, and compares the output t&I detected by the current detection unit 4 with the 1 torque signal B, as shown in Fig. 3, and performs the next control. Note) t'L is M
In FIG. 1 and FIG. 2, there is no particular explanation, or the same applies to the prior art.

The voltage detector @0 detects the output voltage of the lI# converter 40, that is, the voltage Bd inputted to the inverter unit 2, and supplies the detected @signal C to the subtraction input of the adder circuit 640.

supply

The pattern generator 662 receives the speed signal V as an input, generates a voltage command signal I) whose characteristics are desired to have one of the characteristics shown in FIGS.
The addition circuit 64, which supplies the addition power of the calculation circuit 64, generates both of these fractions (the difference of the sum of lj'D and C (I) - C) - Δ■, and 'L' is amplified to a specific level by the error amplifier 66, and the signal Δ■' is sent to the phase shifter 6.
Enter 8.

The phase 668 sequentially changes the gates of the thyristors 42 to 47 (Fig. M9) of the variable hμ40 to a phase l&#l according to the signal ΔV'.
I control to change the DC output voltage Ed of the forward conversion section 40,
It operates to converge to 1 voltage given by the voltage command rs@D.

Therefore, are the voltage detection TiF 60, addition circuit 64, multiplier 66, and phase shifter 68 changed as a whole? ! An automatic voltage control system has been established for each of the 40 wires, and then 1
The operation of this embodiment will be explained.

First, the pattern generator 62 is set so as to give the characteristics as shown in FIG. , suppose that Furthermore, this a
The characteristics of the stt diagram are the characteristics of the actual switching wave number versus rotational speed (shown in Figure 4), which is indicated by the broken line in the figure.
is determined as the reciprocal of motor 3.
As the rotational speed of the motor 3 changes under control, the *fl side input voltage Ed to the inverter section 2 becomes 411, and as the rotational speed of the motor 3 decreases, the voltage Ed also decreases accordingly to ↓5. In other words, the induced electromotive force Ca of the motor 3
The voltage Rd will also increase or decrease in accordance with the increase or decrease in .

Therefore, if this implementation is carried out, the above equations (1) and (2)
) The voltage ΔhFi in the equation is unrelated to the rotational speed of the motor 3.KfiP1 kept constant n1 is shown in Figure 6. The time it takes for the output current to rise to a predetermined value Ixt is also shown by T.
Since it is always constant, the hysteresis ring δ of the threshold value circuit M@ (see Jll! 211N wA) provided in the 1-vector control The switching frequency of the elements 20 to 2s is in direct relation to the rotational speed of the motor 3, so that Kfi is always kept constant, so the torque ripple of the motor 3 may increase in the low speed region, and vibration and noise may increase. Is it possible to prevent it?

In addition, in this embodiment, since the switching frequency of the main switching element is kept constant, the frequency of the noise generated from the motor is also kept constant, which reduces the noise sensation. I can do it.

Next Jf, the characteristic tm12 diagram of the pattern generator 62 or the first
Even if it is determined as shown in Fig. 3, when the rotational speed of the motor 3 is controlled to a low speed region, K is the human power voltage Ed on the 1 m stream side of the inverter s2 (low), as in the case of the 11th horse mackerel. Therefore, even if the above-mentioned hysteresis -δ [KLlj remains constant, the main switching elements 20 to 2 in the low speed region of the motor 3
It is possible to prevent the switching frequency from increasing.

In addition, the actual implementation of this succession of Figs. 12 and 13 is as shown in Fig. 11.
This is a simplified version of the embodiment shown in FIG. 12. In the embodiment shown in FIG. 12, the voltage command for the rotational speed vK is 0! In the example shown in Figure 13, the voltage command signal DWt is changed according to the rotation level VK. In this case, the pattern generator 62 can be changed in a stepwise manner in two stages, and the structure of the pattern generator 62 can be simplified, resulting in cost reduction.

Next, No. 14a is another embodiment of the present invention, and in the figure, No. 7
G is a switching frequency setter, 72 is a frequency/voltage conversion rod, 74Fi comparison addition circuit, 76Fi# difference increase IM
The switching frequency setter 70 is composed of a potentiometer, etc., and is a built-in standard for controlling the switching frequency f of the main switching elements 20 to 2s to a predetermined frequency. The wave number/voltage conversion signal 12, which generates the signal f, is supplied from the vector 8 control element sO to the inverter section 2, and is manually powered by the broken gate 2, and the main switching elements 20 to 2
A voltage signal fv1 corresponding to a switching frequency fK of 5 is generated.

The difference signal Δf between the adder circuit 74e′i and fv is supplied to the adder circuit 64.

Therefore, according to Konomi & HK, the main switching element 20
The W Hm + input voltage Ed of the inverter unit 2 is controlled so that the switching frequency f of ~25 is equal to the constant value f0, and the hysteresis width δ is the same as in the embodiment shown in FIG. Also, the switching frequency can be kept constant, which eliminates the drawbacks of the prior art.

Note that the setting value f in the embodiment of FIG.

may be controlled according to various patterns depending on the conditions of one operation.

In addition, in the above explanation, even in the f'L O) embodiments! The phase l by the thyristor as the jIiiia section 40
! Although the i control type 'ft1 was used, a chopper type one may be used in place of this 2'LK.Furthermore, as a configuration of the II flow circuit, the control type as shown in Fig. 17pJ942~ A gate turn-or-thyristor may be used in place of 47, and a bridge configuration or a mixed bridge may be used. It goes without saying that the manual process does not matter whether it is single phase or polyphase.

The inverter unit 2 is not limited to the vector control method described above, and may be of any type.

By the way, in recent years, digital control has been widely adopted.
ing. Therefore, it is clear that the embodiments of the present invention may also be digitally controlled by a microcomputer or the like having the above-mentioned analog configuration.

As explained above, if the present invention is applied, the hysteresis width to be set for the operation of the output current control system can be changed without changing the hysteresis width.
Since it becomes possible to control the switching frequency of the main switching element, the drawbacks of the conventional technology are eliminated, and the characteristics of the main switching element are fully utilized without increasing the motor's torque ripple or movement. Therefore, it is possible to provide a current comparison type AC 11 source device that can control the current level and reduce the influence of motor noise.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of the main circuit in a conventional example of a current comparison type AC power supply, and Figure 2 is the same. ~e9
is a waveform diagram for explaining the operation, and Figure 4 is a diagram showing the relationship between the rotational speed of the motor and the switching frequency of the main switching element.
Figures 1 and 5 are equivalent circuit diagrams for operation inspection, Figures 6 and 7.
8 and 8 are characteristic diagrams for explaining the operation, FIG. 9 is a circuit diagram showing an example of the main circuit of the current comparison type AC power switch according to the present invention, and FIG. 10 is an embodiment of the present invention. The block diagram, MTT diagram, FIG. 12, and ILA diagram showing the overall configuration of the
FIG. 814 is a block diagram showing another embodiment of the present invention. 2... Inverter section, 3... AC motor (motor), 4. ...Current test ti! I, 40
...III! Conversion unit, 50... Vector 1111111 device, 52...
(b) Rolling speed detector, 60... Voltage detector, 62... Pattern generator, 64.14...
...addition circuit (comparison (b) circuit), 66.1673
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Claims (1)

[Scope of Claims] (t) An inverter that drives and controls an AC motor using an output current obtained by switching a main switching element, a current detector that generates a current detection signal in response to the output current of the inverter, and the inverter as described above. a comparator that compares the current command signal KN''f with the current detection OIv, and a control 11 that performs switching h+all of the main switching element with a predetermined hysteresis based on the difference signal outputted from the comparator. In the current comparison type AC electromotive force wII circuit, the DC voltage control circuit 11 controls the DC voltage input terminal of the inverter, and an electromotive force that generates an electromotive force detection signal corresponding to the induced electromotive force of the AC motor. A detection circuit is provided, and m is supplied to the main switching element according to the induced electromotive force of the AC motor.
A current comparison type alternating current power N device characterized in that the switching frequency of the main switching element is controlled to be 1j to 5 to convert the Rt source voltage into a voltage. 2. In claim 1, the DC voltage rg
The IIi11 circuit includes a voltage detection means for detecting the DC side human voltage of the inverter, a comparator for comparing the detection signal of the detection means with the electromotive force # based on the output of the electromotive force #, and the comparison. 1. A current comparator-type AC voltage device comprising: means for controlling the DC side output voltage of the forward converter to the inverter according to the output of the converter. & Claim Paragraph 1 or! In item 2, the current comparison type alternating current power monitoring system a is characterized in that the electromotive force detection circuit is constituted by a co-rotation speed detector of the alternating current motor.
1. . 4. A current comparison type alternating current, characterized in that the electromotive force detection oil path is constituted by a means for detecting the switching frequency of the main switching element, in item 1 or 2 of the scope of specification IIf. power iron 1