JPS592579A - Controller for inverter - Google Patents

Abstract

PURPOSE:To prevent an interference which occurs when all of the m-phases are controlled at instantaneous value by controlling ON or OF of an electric valve of the remaining one phase in response to the ON or OFF control state of an electric valve of (m-1) phase to be controlled at the instantaneous current value. CONSTITUTION:Outputs in response to phase load currents from current detectors 5U-5W and phase current command values from current command generators 6U-6W are inputted to comparators 7U-7W and compared thereby. A logic sequence circuit 13 inputs outputs of the comparators 7U-7W and level detectors 12U-12W, controls ON or OFF the electric valves of positive and negative sides of the remaining one phase in response to the electric valves of 2 phases to be controlled at the instantaneous current value irrespective of the outputs of the comparators 7U-7W, and produces an output of sequentially switching between the electric valves of the 2 phases and the electric valve of the remaining one phase at the prescribed phase of the output current phase. These outputs are respectively applied via amplifiers 8U-8Z to the electric valves GU-GZ.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement of an inverter control device, and particularly to an inverter control device suitable for drive control of an AC motor or the like without a neutral point terminal.

[Technical background of the invention]

Inverter control devices are widely used for drive control of AC motors.

Figure 1 does not show a configuration example of a three-phase inverter control device conventionally used for instantaneous current value control of a three-phase AC motor. Between the positive and negative bus lines 2P and 2N, there are electric valves GU, GX, and GV consisting of gate turn-off thyristors or giant transistors.

Two each of GY, GW, and Gz are connected in series.

Each of these electric valves has a rectifier and an element connected in antiparallel.

The midpoint of each series electric valve and each phase winding U of the load motor 3,
Conductive wires 4U, 4v, and 4w connect V and W, and a conductive wire 4N connects the neutral point N of the load motor 3 and the midpoint of the DC currents 1p and IN.

A current detector 5 is installed for each of the conductors 4j14tr, 4v, and 4w.
U, 5v.

5w are combined, and their output u, engineering vt:I
w is the current command generator for each phase 6σ, 6V, 61y
The current command value from the comparator 7υ,
It is input to 7V and 7W and compared.

Comparators 7U, 7V, 7W each phase current command value 12,
l:! Work ÷ is each phase's tonnage flow detector output lU, work V, work W
When it is greater than 111, it outputs level 111, and when it is not, it outputs level lO''.The output cuff of these comparators υOv
7Vow'7wo are amplifiers sU, 8V,
Input to sw and negative circuit 9U, 9V
, 9W, and then input to amplifiers 8x, 8Y, and 8z.

Amplifier sU, sv, sw, 8X, 8Y, sz
The outputs of electric valves GU, Gy, Gw,
It is input to each base terminal of Gx, Gy, and Gz. Therefore, the comparator 'y, , , 7v , 7
When the output of W is level “110”, the positive side electric valves GU, G
v.

Gw is turned on, and the negative side electric valves Gx, GY, and G2 are turned off. Conversely, when the output level of the comparator becomes 01, the positive side electric generator is turned off and the negative side electric valve is turned on.

Also, a comparator? In order to provide hysteresis characteristics to 0, 7V, and 7W, a voltage dividing resistor 10 connected to the output terminal is used.
U, 10v, iow, IIU, llv
, llv, is configured to be fed back to the input side.

FIG. 2 shows the zero-phase current control operation waveform in the inverter control device configured as described above. In the figure, P is the upper limit value of the hysteresis characteristic of the comparator 7U, and Yari indicates its lower limit, and the output of the comparator 7U is between the output I of the current detector 5U and P. Time does not change.

As mentioned above, when the output cuff UQ of the comparator 7U is at level 111, the electric valve GU is turned on, GX is turned off, and the output?
When tro is at level w01, electric valve Gυ is off, G
X is turned on.

When the output current IU of the current detector 5U, which is proportional to the current flowing through the load motor 3, decreases and reaches the hysteresis lower limit value IB of the comparator 7U (to), the comparator cuff UQ reaches level 111. Then, electric valve GU turns on.
GX is turned off. Therefore, the U-phase load current flows through the path of the positive power source P, the conductor 2P, the electric valve Gυ, the U-phase winding of the load motor, the neutral point N, the conductor 4N, and the power supply midpoint O.

The current increases and the output current U of the current detector 5U reaches the hysteresis upper limit IP, and at time t1 the comparator cuff UO reaches level 101, the electric valve G is off and Gx is on. becomes. Therefore, the U-phase current is negative side power supply i
It flows through the path of N - power supply middle point - conductor 4N - neutral point N - load U phase winding - conductor 4U - electric valve Dx - N - 2N.

Even after time t2 when the 0-phase current decreases and the detector output current I reaches the hysteresis lower limit ■P again, switching of the electric valves GU and GX is performed in the same way as above, and the load current is changed to the conductor 2P or 2N and conductor wire 4N.

The above is the operating waveform for the U-phase load, but the same applies to the ■-phase and W-phase loads.

Therefore, if a load current approximately like a sine wave flows through each phase winding of the load motor 3 with a phase difference angle of 120°, then K is obtained. In this case, the fundamental wave of the load current at the neutral point H cancels each other, so it does not flow through the conductor 4N, but since harmonic components remain, the conductor between the power supply neutral point 0 and the load neutral point N, 4
If an attempt is made to control the instantaneous current values of each phase independently without connecting with N, the currents of each phase will interfere with each other, making it impossible to perform good control.

[Problems with background technology]

As mentioned above, in the background technology, when controlling the instantaneous value of each phase current flowing through the load independently, it is necessary to short-circuit between the power supply neutral point and the load neutral point. It has the disadvantage that it can only be applied to a special specification electric motor with a standard electric motor. Furthermore, since two power supplies are required, one on the positive side and one on the negative side, there is a drawback that the circuit layout becomes complicated and the cost increases.

[Purpose of the invention]

The present invention eliminates the above-mentioned disadvantages in the background art,
It is an object of the present invention to provide an inverter control device that can perform good current control even with a standard AC motor without a neutral point terminal, and that requires only one power supply circuit.

[Summary of the invention]

The inverter control device of the present invention has an inverter circuit in which m sets (m is an integer of 2 or more) of series electric valves are connected to a DC power source, and connected to m sliding charge terminals at the midpoint of each of these series electric valves. A comparator that inputs the current detector output corresponding to each sliding charge current and each phase power supply command value and compares the two to generate a logic output of level 111 or level 101, and a comparator for these m phases and a level The output of the detector is manually input, and the positive side and negative side electric valves of the remaining one phase are controlled by the comparator according to the on/off state of the electric valve of the (m-'1) phase, which is controlled by the instantaneous current value. On/off control is performed regardless of the output, and the above (m-13 phase electric valve and the remaining 1
The main feature is that it is equipped with a logic sequence circuit that produces an output that sequentially switches the phase electric valves.

[Embodiments of the invention]

Hereinafter, embodiments and operations of the device of the present invention will be described with reference to FIGS. 3 and 4. In these figures, the same parts as in FIG. 1 are given the same reference numerals.

An electric valve G is connected to the DC' power source 1 via conductors 2F and 2N.
U.

Two GX, Gv, GY, GW, and GZ are connected in series, and each electric valve has a diode D.
are connected in antiparallel. Conductive wire 4U connecting between the midpoint of each phase electric valve connected in series and each phase winding of load motor 3
.

Current detectors 5U, 5V, and 5W are coupled to 4V and 4W to detect the current of each phase, respectively, and their outputs lu.

Engineering v and Engineering w are current command generators 6U and 6V for each phase.
, current command value ■δ from 6W, engineering 6, together with No. 1,
Comparator 7 [.

Input to 7V, 7W, current command value, ■
When the input and engineering numbers are larger than the current detector outputs lU, engineering V, and engineering W, level 11" is output; otherwise, level 10I is output. In addition, at the output terminal of each comparator, there is a voltage dividing resistor ioU, 10y, IOW and IIU, IIV
, l1w are connected in series, and the midpoint voltage of these series resistors is fed back to the input side of the comparators 7U, 7v, 7W, giving each comparator a hysteresis lh' property similar to that in FIG. Give.

Current command generator 6U, 6V, 6W, current command value generator, 6. I also have a level detector 12σ, 12v.

Guided by 12W. These level detectors output level 111 when the current command values ♂, ♂, ♂ are positive,
When it is negative, level 101 is output.

Comparator 7U, 7v, 7W and level detector 12U
, 12v.

12w output cuff UO+ 12UOt 7vo l 12
vQ t 7WOy 12WO are input to address inputs Ao to A5 of the logic sequence circuit 13, respectively. This logic sequence circuit is made up of, for example, 41 read-only memories (ROM), and its outputs are Do, D2. The control signal generated at D4 is increased in width &Sυ,
After being amplified by 8V and 8W, the positive electric valve control signal 8UO
+ electric valve GU, Gv, GW as svQ t 810
is input to the base terminal of Moreover, the output terminal D1. D3
．． The control signals generated at D5 are transmitted through amplifiers sx, sy,
After being amplified by sz, the negative side electric valve control signal sxo t
8YOt 8zO is input to the pace terminals of electric valves Gx, GY, and C2.

Next, the operation of the inverter control device of the present invention configured as described above will be explained with reference to FIG.

In the present invention, the -period of the current command value, for example lG, is decomposed into modes 1 to 2 as shown by mode numbers in Fig. 4, and first, in each mode, the current command value
The electric valve (indicated by aS in FIG. 4) corresponding to the phase in which the trajectory value of is the maximum is opened regardless of the outputs of the comparators 7U and 7W7w.

In other words, in mode ■, the absolute value of the current command value is maximum *, and its polarity is negative, so the output terminal D3 of the logic sequence circuit 13 has an open valve regardless of the output of the comparator 7■. A command is output, and the electric valve GY is opened by the electric valve control signal 8YO. In this case, the other U-phase and W-phase electric valves are controlled by instantaneous current values according to the outputs of the comparators 7U and 7W. Therefore, the sum of the currents of the U-phase and W-phase flows into the V-phase.

Next, the current detectors U and W for the U phase and W phase are increased, and the outputs of the comparators 7U and 'yw are both level 10.
When it becomes 1, the electric valves G[ and GW are turned off, and Gx and Gz are turned on. Thus negative (ill the electric valve Gx, G
Y.

When only Gz is on, the load current cannot be controlled, so the output of comparators 7U and 7W is level 1.
01, the electric valve GY that had been turned on until then
is turned off, and the positive side electric valve Gv is turned on while the negative side electric valve GxGz remains on. As a result, the load U phase, W phase
Phase current decreases.

In this way, during the mode ■ period, Gv is turned on continuously while electric valves G and GW are turned off at the same time, and GY is turned on continuously at other times, so that the current 1
Instantaneous value control is performed.

In mode ■, the control signal c8 in FIG.
First, the electric valve GU is turned on, and the load currents of the ■ phase and the W phase are instantaneously controlled by the comparators 7V and 7W. Also in this case, the output cuff VQ of comparison b 7y, 71y.

When both 7WO reach level A, electric valves Gv and G.

is turned on, and the valve that is open is the positive electric valve GU.

Only Gy and Gw are available. Therefore, at this point, the output of the logic sequence circuit 13 turns off the electric valve Gυ.
Turn on Gx. In this way, the electric valve GV.

Since the current flowing into the load from the shaft flows back to the power supply 1 through the negative electric valve GX, control to increase the load current is possible.

The above is the operation in modes (1) and (2), but in modes (2) to (2), each sliding charge current can be instantaneously controlled in accordance with the current command value in the same manner as described above.

The operation sequence in each mode above is for level detector 1.
2U, 12v, 12W and comparator 7U, 7y, 7
Since it is uniquely determined by the output of H, it can be easily executed by writing the data into ROM.

In addition, although the above explanation has been given with respect to an example in which a three-phase AC motor is used as the load, the present invention is not limited to this, and can also be applied to an intervening inductance load, and the number of phases is not limited to three phases. It can be widely applied to m-phase (m is an integer of 2 or more).

〔Effect of the invention〕

As described above, in the present invention, in an inverter control device that instantaneously controls the m-phase sine wave current, the remaining The one-phase electric valve of (
Since the electric valves of the m-1) phase and the remaining 1 phase are switched sequentially, it is possible to prevent the interference that occurs when instantaneous value control is applied to all m-phases, and to set the load neutral point to the target. Good control can be achieved without connection to a sleep source.

Therefore, a standard electric motor without a neutral point terminal can be used as a load, and only one DC power supply is required, and the circuit can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram illustrating a conventional inverter control device,
FIG. 2 is an operating waveform diagram, FIG. 3 is a circuit diagram showing an embodiment of the equipment of the present invention, and FIG. 4 is an explanatory diagram of its dynamic waves. 1 + Ip * IN... Surface power supply, 3... Load, 5Ut 5yt 5y... Current detector, ct,
, , 6V, 6W...Current command generator, 7U
, 7V, 7W'' comparator, 8U, 8v, 8W,
8X, 8Y, 8z...amplifier, IOU, IOV,
10y, 11t7. Ily, IIW...Voltage dividing resistor, 12U, 12V, 12W...Level detector,
13...Logic sequence circuit. Applicant's agent Kiyoshi Inomata 1 Figure 2 Rho 2 Figure 4 Figure

Claims (1)

[Claims] 1. In an inverter circuit in which m sets (m is an integer of 2 or more) of series electric valves are connected to a DC power source and connected to an m-phase load terminal at the midpoint of each of these series electric valves, A comparator that is provided corresponding to each phase and inputs the current detector output corresponding to the load current of each phase and the current command value of each phase, compares the two, and generates a logic output of level 11'' or level l g m. , a level detector provided corresponding to each phase and generating a logical output of level 11'' or level ``0'' depending on whether the current command value of each phase is positive or negative, and m sets of comparators and level detectors. The output of the detector is input, and the positive side and negative side electric valves of the remaining one phase are controlled according to the on/off state of the electric valve of the (m-1) phase, which is controlled by the instantaneous current value, and the output of the comparator is The above (m-1) is controlled for each predetermined phase of the output current phase.
1. An inverter control device comprising: a logic sequence circuit that generates an output to sequentially switch one phase electric valve and the remaining one phase electric valve. 2. The inverter control device according to claim 1, wherein the logic sequence circuit comprises a read-only memory. 3. The inverter control device according to claim 1 or 2, wherein the m-phase load is a three-phase AC motor without a neutral point terminal.