JPH05161269A - Harmonic current compensator - Google Patents

Abstract

PURPOSE:To provide a higher harmonic wave compensator which remarkably reduces current ripple of parallel multiplexed inverters and whose capacity can be made large and whose size can be reduced and which can be highly efficient. CONSTITUTION:Between an a.c. supply system and a.c. terminals of N sets of polyphase inverters 410, 420 and 430, the plurality of combined reactors 461U1-461W3 are located, each of which has the plurality of primary coils and the plurality of secondary coils which correspond to the a.c. terminals of each inverter. One terminal of the secondary coil is connected to the a.c. terminal of the polyphase inverter 410, 420 and 430 and the other terminal is commonly connected to the same phases of each polyphase inverter. The primary coil connects the same phases of each polyphase inverter 410, 420, 430 in series and one terminal of the primary coil which is serially connected to the common connection of the secondary coils is connected to the same phases of the inverters 410, 420 and 430 and the other terminal of the serially connected primary coils of the combined reactors is connected to the a.c. supply system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic current compensator for high power applications, for example, and more particularly to a harmonic current compensator in which N multiphase inverters are multiplexed.

[0002]

2. Description of the Related Art In recent years, a high power cycloconverter has been connected to a power supply system and operated, and a harmonic current generated by the cycloconverter has become a problem. A harmonic current compensator is installed as a countermeasure against the harmonic current, but as is well known, the input current harmonic of the cycloconverter changes in relation to both the power supply frequency fI and the output frequency fO, so it consists of a conventional capacitor and reactor. The passive resonance type filter has a problem that a sufficient compensation effect cannot be obtained.

To solve this problem, a so-called harmonic current compensating device (also called an active filter), which actively applies harmonic compensation by applying a power converter technique, has recently been studied in various fields. .. The harmonic current compensator detects the harmonic current in the power supply system and uses it as a command value to operate the power converter such as an inverter to generate a compensating harmonic in the opposite phase to the compensated current and inject it into the power supply system. The harmonic current is compensated for by the principle, and in principle, any harmonic current can be dealt with. The power converter in this case has a multi-phase inverter using a gate turn-off thyristor (hereinafter referred to as GTO) and a power transistor (hereinafter referred to as GTR) as a basic circuit. There are many things to deal with. In this case, the performance of the harmonic current compensator depends on how the multiphase inverters are multiplexed, so that an efficient method for multiplexing the multiphase inverters has been strongly demanded. Hereinafter, the configuration and problems of the conventional harmonic current compensator for high power applications will be clarified, and a solution thereof will be described.

FIG. 7 is a diagram in which a harmonic current compensator is applied to a power supply system. In the figure, 10 is an induction motor 12.
A harmonic generation load having a cycloconverter 11 for rotating the motor, 1 is an AC power supply system such as a transmission and distribution bus, 3
U to 3 W are impedances of the power supply system. The harmonic current compensator (active filter) 30 has terminals 4U,
Current for connecting between 4V, 4W and 5U, 5V, 5W and detecting currents iLU to iLW containing harmonics and inputting them to the input terminals 310U, 310W of the controller 300 shown in detail in FIG. Detectors 32U, 32W and controller 300
, The compensating harmonic current icu
It consists of an inverter 400 that injects ˜icw.

With this configuration, a current (icu to icw) having a phase difference of 180 degrees and the same amplitude is generated in the active filter 30 with respect to the harmonic current generated by the cycloconverter 10. Therefore, this current and the cycloconverter are generated. 10 harmonic currents are generated at terminals 4U-4W and 5U, 5V, 5
The W connection points 31U to 31W are combined and cancel each other, and as a result, the harmonic current does not flow toward the power supply system 1.

FIG. 9 shows a power converter 400 of a type in which, for example, three three-phase inverters INV1 to INV3 are multiplexed in parallel in order to cope with the increase in power consumption. In the figure 410, 4
Reference numerals 20 and 430 denote three-phase inverters composed of GTO or the like, which are operated by well-known pulse width control (PWM control). 411, 421, 431 are DC power supplies, 412
U-412W, 422U-422W, 432U-432
W is an AC output terminal of the three-phase inverter, 413U to 413
W, 423U to 423W, and 433U to 433W are AC reactors. The inverters INV1 to INV3 are AC reactors 413U to 413W, 423U to 423W,
Parallel multiplexing is performed via 433U to 433W. Four
51U and 451W are current detectors, and power converter 40
The currents iCUT to iCWT generated by 0 are detected. Reference numeral 355 denotes a transformer for matching the power supply system voltage with the output voltage of the power converter 400, and the lines 360U to 360W are shown in FIG.
Connected to the terminals 31U to 31W.

FIG. 8 shows a power converter 400 having a multiplex structure.
It is a controller for controlling. In the figure, 302 is high
Harmonic detector, input to input terminals 301U and 301W
Load current signals iLU, iLW (load voltage
Current and its detection signal are attached with the same symbol).
Of the harmonics by removing the fundamental wave component from the load current signals iLU and iLW of
Harmonics corresponding to the harmonic components generated by the wave generation load 10
Signal iHUR^* , IHWR^* And output terminals 303U, 3
Output to 03W. 304U and 304W are comparators
, Harmonic signal iHUR^* , IHWR^* And the detection signal iCUT,
iCWT is compared, and deviations ΔHU and ΔHW are output
Output to the child 305U, 305V. These deviations increase
Amplified by the width devices 306U and 306W and output terminal 307
U, 307W to W phase voltage command vHU^* , ΔHW^* Got
Be done.

In the three-phase system in which the neutral point is not connected, the current of the remaining one phase can be specified by controlling the current of two of the three phases. It is a control method.

Next, an adder 308 is a voltage command vHU ^{* for the} U and W phases ^. , VHW ^* Are added with the polarities shown in the figure and the V-phase voltage command vHV ^* Is generated and is output from the output terminal 307V. Comparator 304U, 304W, amplifier 306U, 3
The part including 06 W and the adder 308 is called a current controller 360.

Reference numeral 350 denotes a triangular wave generator composed of triangular wave generators 351 to 353. The triangular wave generator 350 has a repeating frequency of fm and triangular waves S1, S2 and S3 whose phases are shifted from each other by 2 / 3π.
Is generated, and the detailed operation will be described later. However, as shown in FIG. 9, three inverters INV1 to INV1
When INV3 is multiplexed, when N inverters are multiplexed, the phases of the triangular waves S1 to SN are shifted by 2π / N from each other).

Reference numerals 310, 320 and 330 denote switching elements U1, V1, W1, X1, Y1 and Z1, which constitute the inverters INV1, INV2 and INV3 of FIG. 9, respectively.
U2, V2, W2, X2, Y2, Z2, U3, V3, W
This is a comparator for determining the firing timing of X3, X3, Y3 and Z3.

The voltage fingers 310U, 320U, 330U
Order vHU^* Is given, and 310V, 320V, 330V
The voltage command v is applied to each of 310W, 320W, and 330W.
HV^* , VHW^* Is input to one terminal, and the comparator 3
Triangular on the other terminal of 10U, 310V, 310W
The wave signal S1 is input to the comparators 320U, 320V, 3
20W and 330U, 330V, 330W each have three
Square wave signals S2 and S3 are input, and these voltage command values and three
Inverter INV1, INV2, I
Generates NV3 gate pulses GP1, GP2, GP3
It The gate pulses GP1 to GP3 are the inverter I of FIG.
Given to NV1 to INV3, based on this
Ignition control is performed.

Here, the comparators 310U, 3 shown in FIG.
The operation of 20U and 330U will be described with reference to FIG. That is, in FIG. 3A, the voltage command vHU ^* from the output terminal 307U ^. And the triangular wave S1 from the output terminal 351 are compared, and S1 is vHU ^* When it is larger, a gate pulse is output to GX1 in FIG. 8 and S1 outputs vHU ^*. GU1 when smaller
Issue a gate pulse to. As a result, a voltage subjected to so-called pulse width control (PWM control), such as eU1 in FIG. 3, is generated on the line 412U of the inverter INV1 in FIG. Comparators 320U and 330 are shown in FIGS.
The operation of U and the output voltages eU2, eU3 of lines 422U, 432U of inverters INV2, INV3 of FIG.

The conventional apparatus configured as described above operates as follows. First, the harmonic component contained in the current of the harmonic generating load 10 of FIG. 7 is detected by the harmonic detector 302 of FIG. 8, and the harmonic current command iHUR ^* , IHWR ^* Is obtained. The current controller 360 uses the harmonic current command iHUR ^* , I
HWR ^* Is received as a command, the inverters INV1 to INV3 (FIG. 9) are operated in response to this command, and the power converter 4
00 of the generated current iCUT, of commanding the iCWT iHUR ^* ，
iHWR ^* Works to match. At this time, since the inverters INV1 to INV3 (FIG. 9) are operated by PWM control, the commands iHUR ^* are applied to the currents iCUT to iCWT of the power converter 400 ^. , IHWR ^* In addition to the component indicated by, the magnitude is determined by the inductance of the AC reactors 413, 423, 433 (FIG. 9) at a frequency related to the repetition frequency fm of the triangular wave signals S1 to S3 (FIG. 8 or FIG. 3). Including ripple component.

This state is shown in FIG. In the figure, iCU1 is the U-phase current output from the inverter INV1 (FIG. 9), iCU2 is the inverter INV2, iCU3 is the current of the inverter INV3, and iCUT is the current iCU1, iCU2,
The current of the power converter 400, which is the combined value of iCU3, iHUR
^* Is a harmonic current command. In this case, although the individual inverter currents iCU1, iCU2, iCU3 contain a considerably large ripple component, the ripple current is greatly reduced due to the effect of shifting the phase of the triangular wave signals S1, S2, S3 in their combined value iCUT. You can see how it is doing.

[0016]

The above is a harmonic current compensator using a conventionally used multiplex inverter, which has a configuration of compensating currents iCUT to iCWT generated as a harmonic current compensator. It is used in conventional large-capacity harmonic compensators because it can greatly reduce the ripple content.

However, there are the following problems. That is, the harmonic current compensator uses the harmonic current command iHUR ^* , I
HWR ^* A closed loop current control system is configured by the current controller 360 (FIG. 8) that receives it, and the power converter 400 (FIG. 9) controlled thereby. Therefore, in order to improve the harmonic compensation performance, the AC reactors 413, 42
The inductance values of 3,433 (FIG. 9) must be designed to be as small as possible.

However, the AC reactors 413, 42
On the other hand, if the inductance value of 3,433 is reduced,
There is a drawback that the ripples of the individual currents of the inverters INV1 to INV3 increase (see the large ripple of iCU1 to iCU3 in FIG. 10). If the ripple of the current of the individual inverters that are multiplexed in parallel increases, the current due to the ripple component will increase compared to the current that should originally flow.To cope with this, increase the current capacity of the switching element of the inverter. Must, therefore,
High cost. Further, since a large ripple current is switched, the switching loss increases and the efficiency drops. Furthermore, AC reactors 413, 423, 433
Since a large ripple current flows through the core, various problems such as generation of harmonic loss occur in the iron core that constitutes the reactor.

As is clear from the above description, in the conventional harmonic compensator having the multiplex structure, there is a demand for improving the harmonic current compensating performance, that is, reducing the inductance value of the AC reactor → improving the current control response. , Requirements for efficiency improvement and device cost reduction, that is, increasing the inductance value of the AC reactor → current ripple reduction are contradictory, and it is impossible to realize a device that satisfies these requirements at the same time. The current situation was to design the device at the expense of both requirements.

Therefore, it should be understood from the above description that the harmonic compensating device having the multiplex structure should have the current control response arbitrarily increased to sufficiently exhibit the harmonic current compensating performance. Even in such a case, it is a highly efficient and low cost device, and development of a device satisfying these is desired.

Therefore, the object of the present invention is to significantly reduce the current ripples of the individual inverters that are parallel-multiplexed by the action of the coupling reactor, and to design the coupling reactor so that any number of inverters can be parallel-multiplexed. As a result, the capacity can be increased and the device can be downsized.
Another object is to provide a highly efficient harmonic compensator.

[0022]

In order to achieve the above object, the present invention detects a harmonic current of an AC power supply system, generates a compensation current having a phase opposite to the harmonic current by a multi-phase inverter, and A harmonic current compensating device for injecting into an AC power supply system to perform harmonic current compensation, comprising a power converter configured by combining N multiphase inverters in a multiplex configuration, wherein the AC power supply system AC reactors are provided between the AC terminals of the multi-phase inverters and the AC terminals of the multi-phase inverters in accordance with the number of phases of the poly-phase inverters. A plurality of coupling reactors having a plurality of primary windings and secondary windings corresponding to the respective AC terminals of the multiphase inverter are arranged, and one terminal of the secondary winding of the coupling reactor is connected to the multiphase inverter. Connected to different AC terminals, the other terminals of the secondary windings of the coupling reactor are commonly connected to those belonging to the same phase of the respective multi-phase inverters, and the primary windings of the coupling reactor are connected to the respective multi-phases. The inverters belonging to the same phase are connected in series, and the common connection point of the secondary windings of the coupling reactor and one terminal of the primary winding connected in series are connected to those belonging to the same phase of the multiphase inverter. The connection is made by connecting the other terminal of the primary winding connected in series of the coupling reactor to the AC power supply system via the AC reactor.

[0023]

According to the present invention, the current ripples of the individual multi-phase inverters that are parallel-multiplexed by the action of the coupling reactor can be significantly reduced, and the number of inverters can be parallel-multiplexed by the design of the coupling reactor. , Therefore,
The capacity can be increased, the size of the device can be reduced, and a highly efficient harmonic compensator can be realized.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a circuit diagram showing a part of an embodiment of a harmonic compensator of the present invention, and FIG. 1 corresponds to the conventional FIG. Here, different points between FIG. 1 and conventional FIG. 9 will be mainly described, and the same portions as those in FIG. 9 will be denoted by the same reference numerals and description thereof will be omitted. FIG. 1 shows three-phase inverters INV1, INV2, IN
This is the case when three V3s are multiplexed, and each inverter I
AC output terminals 412U, 412V of NV1 to INV3,
412W, 422U, 422V, 422W, 432U,
AC reactors 460U, 460V, 460W and coupling reactors 461U1 to 461W3 are connected between 432V, 432W and the transformer 355.

Coupling reactors 461U1-461 of FIG.
W3 has the same characteristics and is configured as shown in FIG. FIG. 2 shows the configuration of only the coupling reactor 461U1, which has two windings in which the primary winding L01 and the secondary winding L02 are separated, and the number of turns N of the primary winding L01.
The number of turns N2 of 1 and the secondary winding L02 is designed so that the number of turns is N2 / N1 = N, where N is the number of multiplexed inverters. Similarly, the coupling reactor 461U2-
461W3 is also configured.

In FIG. 1, each inverter INV1
~ INV3 U-phase AC output terminals 412U, 422U,
432U is a coupling reactor 461U1 and 46, respectively.
Connected to one terminal of the secondary winding of 1U2, 461U3, coupling reactor 461U1, 461U2, 461U
The other terminals of the secondary windings of No. 3 are commonly connected, and further, from the common connection point, individual coupling reactors 461U
The primary windings of 1,461U2 and 461U3 are connected in series and connected to the AC reactor 460U.

Similarly, V of the inverters INV1 to INV3
Phase AC output terminals 412V, 422V, 432V are connected to AC reactor 460V via coupling reactors 461V1, 461V2, 461V3, and further W phase AC output terminals 412 of inverters INV1 to INV3.
W, 422W, 432W are coupling reactors 461W
AC reactor 4 via 1,461W2,461W3
It is connected to 60W.

The AC output terminals 412U to 432W of the inverters INV1 to INV3 are connected to the AC reactor 4 respectively.
60 U to 460 W and the transformer 355 shown in FIG.
Are connected to the AC buses 31U to 31W. This Figure 1
The main circuit of (1) is incorporated in the power converter 400 of FIG. 7 described above and functions as a harmonic compensator.

The operation of the harmonic compensator constructed as above will be described. In FIG. 7, load currents of the cycloconverter 10 and the like are supplied to the current detectors 32U and 32W.
7 and guides it to the controller 300 to detect a harmonic component, and a compensation current corresponding to the harmonic component is detected as shown in FIG.
The power converter 400 of FIG.

The power converter 400 comprises the multiplex inverters INV1 to INV3 shown in FIG. 1, which are controlled by the PWM control method shown in FIG. Thus, using the PWM control method of FIG. 3, the multiplexing inverter I of FIG.
When NV1 to INV3 are operated, the characteristics shown in FIG. 4 are obtained.

That is, in FIG. 4, iHUR ^* , ICUT are waveforms of the same symbols in FIG.
INV3 current command iHUR ^* And multiplexed inverter current i
It is a CUT. The current iCUT is a current at the same symbol position in FIG. 1 and is a compensation current as an active filter, and the ripple is small due to the multiplexing effect.

Next, pay attention to the currents iCU1, iCU2, iCU3 in FIG. This current is applied to the individual inverter INV1 in FIG.
~ INV3 current, and comparing this current with the current of the same symbol in FIG. 10 obtained by the conventional FIG. 9, it is apparent that the coupling reactors 461U1 to 46 of FIG.
It can be seen that the current ripple of the harmonic current compensator using 1W3 is significantly reduced.

As described above, the harmonic compensator 4 of FIG.
00 is capable of greatly reducing the current ripple of each of the inverters INV1 to INV3 by the action of the coupling reactors 461U1 to 461W3, and the coupling reactors 461U1 to 4
With the 61W3 design, any number of inverters can be parallel-multiplexed, so that the capacity can be increased and the device can be downsized, and a highly efficient harmonic compensator can be realized.

FIG. 5 shows the coupling reactor 461 shown in FIG.
U1-461W3 and AC reactor 460U-460W
It is another embodiment in the case where the arrangement is changed. That is, in FIG. 5, the AC reactors 460U1 to 460W3 are arranged on the AC output side of the individual inverters INV1 to INV3 to be multiplexed in parallel. Compared with the embodiment of FIG. 1, the embodiment of FIG. 5 is characterized in that the number of AC reactors increases.

FIG. 6 shows one phase of the coupling reactor of FIG.
That is, the coupling reactors 461U1, 461U2, 461U
3 is an embodiment in the case where 3 is manufactured as an integral structure reactor. In FIG. 6, the secondary windings L021, L of FIG.
022, L023 and the primary winding 3L01 are structurally arranged as shown in FIG. When three connecting reactors of this structure are used, the connecting reactor 4 of FIG.
The same effect as 61U1-461W3 can be obtained. With this structure, the volume of the coupling reactor can be reduced, which helps reduce the installation space.

In the configuration of FIG. 1, the AC reactor 46 is
Although 3 units of 0U to 460W are used, the action of this reactor is controlled by adjusting the degree of primary and secondary coupling in the coupling reactor shown in FIG. It can also serve as an inductor. By doing so, it is not necessary to separately install the AC reactor, which helps reduce the installation space.

[0037]

According to the present invention described above, the current ripple of the individual inverters that are parallel-multiplexed by the action of the coupled reactor can be significantly reduced, and the number of inverters can be parallel-multiplexed by the design of the coupled reactors. Therefore, a high-capacity harmonic compensating device can be realized which can be increased in capacity and can be downsized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a harmonic compensation device according to the present invention.

FIG. 2 is a view for explaining the configuration of the coupling reactor of FIG.

FIG. 3 is a diagram illustrating a principle of current control of a controller.

FIG. 4 is a current waveform diagram for explaining the function and effect of the harmonic compensation device of FIG.

FIG. 5 is a circuit diagram showing a part of another embodiment of the harmonic compensation device according to the present invention.

FIG. 6 is a diagram for explaining a modified example of the coupling reactor of FIG.

FIG. 7 is a diagram showing a system to which the harmonic compensation device of the present invention is applied.

FIG. 8 is a circuit diagram showing an example of the controller shown in FIG.

FIG. 9 is a circuit diagram showing an example of a conventional harmonic compensation device.

FIG. 10 is a current waveform diagram for explaining a problem of the harmonic compensation device of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Distribution system, 10 ... Harmonic generation load, for example, cycloconverter, 30 ... Harmonic compensator, 300 ... Controller, 4
00 ... power converter, 410 (INV1), 420 (IN
V2), 430 (INV3) ... Inverter, 411, 4
21, 431 ... DC power supply, 461U1-461W3 ... Coupling reactor, 460U-460W ... AC reactor,
355 ... A voltage matching transformer.

Claims (1)

[Claims] 1. A harmonic current of an AC power supply system is detected, a compensating current having a phase opposite to the harmonic current is generated by a multi-phase inverter, and is injected into the AC power supply system to perform harmonic current compensation. And the multi-phase inverter is
In a harmonic current compensating device including a power converter configured by combining N units to form a multiplex structure, an AC of the N multiphase inverters is provided between the AC power supply system and the AC terminals of the N multiphase inverters. A plurality of coupling reactors having a plurality of primary windings and secondary windings corresponding to the respective terminals are arranged, and one terminal of the secondary winding of the coupling reactor is connected to each AC terminal of the multiphase inverter. Then, the other terminals of the secondary windings of the coupling reactor are commonly connected to those belonging to the same phase of each polyphase inverter, and the primary windings of the coupling reactor belong to the same phase of each polyphase inverter. Connect things in series,
The common connection point of the secondary windings of the coupling reactor and one terminal of the primary windings connected in series are connected to those belonging to the same phase of the multiphase inverter, and the primary windings of the coupling reactor connected in series are connected. A harmonic current compensator in which the other terminal of the wire is connected to the AC power supply system.