JP3015559B2 - Harmonic current compensator - Google Patents

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, for example, high power applications, and more particularly to a harmonic current compensator in which N multi-phase 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 has been operated. As a result, harmonic current generated by the cycloconverter has become a problem. A harmonic current compensator is installed as a countermeasure for the harmonic current. However, 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 f0, and therefore includes a conventional capacitor and a reactor. There is a problem that a sufficient compensation effect cannot be obtained with a passive resonance type filter.

In order to solve this problem, recently, a so-called harmonic current compensator (also referred to as an active filter) which actively performs harmonic compensation by applying a power converter technology has been studied in various fields. . The harmonic current compensator detects the harmonic current of the power supply system and uses it as a command value to operate a power converter such as an inverter to generate a compensated harmonic having the opposite phase to the current to be compensated and inject it into the power supply system. The harmonic current is compensated for in principle, and in principle, any harmonic current can be dealt with. The power converter in this case has, as a basic circuit, a multi-phase inverter using a gate turn-off thyristor (hereinafter, GTO), a power transistor (hereinafter, GTR), and the like. There are many things to deal with. In this case, the performance of the harmonic current compensator depends on how the multi-phase inverters are multiplexed. Therefore, there is a strong demand for an efficient multi-phase inverter multiplexing method. Hereinafter, the configuration and problems of a conventional harmonic current compensator for high power use 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 rotationally driving the AC power supply system such as a transmission / distribution bus,
U to 3W are impedances of the power supply system. The harmonic current compensator (active filter) 30 has terminals 4U,
The currents connected between 4V, 4W and 5U, 5V, 5W and for detecting currents iLU to iLW containing harmonics and inputting to input terminals 310U, 310W of controller 300 shown in detail in FIG. Detectors 32U and 32W and controller 300
And the compensation harmonic current icu is supplied to the power supply system 1.
To icw.

With this configuration, a current (icu to icw) having the same amplitude and the same amplitude as that of the harmonic current generated by the cycloconverter 10 is generated in the active filter 30. Ten harmonic currents are connected to terminals 4U to 4W and 5U, 5V, 5
W are combined at the connection points 31U to 31W and cancel each other out, so that no harmonic current flows toward the power supply system 1.

FIG. 9 shows a power converter 400 in which, for example, three three-phase inverters INV1 to INV3 are multiplexed in parallel in order to cope with an increase in power. 410, 4 in the same figure
Reference numerals 20 and 430 denote three-phase inverters composed of a GTO or the like, which are operated by a known pulse width control (PWM control). 411, 421, 431 are DC power supplies, 412
U-412W, 422U-422W, 432U-432
W is the 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,
They are multiplexed in parallel via 433U to 433W. 4
51U, 451W are current detectors, and the power converter 40
The currents iCUT to iCWT where 0 occurs are detected. Reference numeral 355 denotes a transformer for matching the power supply system voltage with the output voltage of the power converter 400.
Are connected to the terminals 31U to 31W.

FIG. 8 illustrates a power converter 400 having a multiplex configuration.
It is a controller for controlling. In the figure, 302 is high
Harmonic detector, input to input terminals 301U and 301W
Current signal iLU, iLW (load current
Flow and its detection signal are identified by the same symbol).
Removes the fundamental component from the load current signals iLU and iLW of
Harmonic corresponding to the harmonic component generated by the wave generation load 10
Signal iHUR^* , IHWR^* And output terminals 303U, 3
Output to 03W. 304U and 304W are comparators.
And the harmonic signal iHUR^* , IHWR^* And the detection signal iCUT,
iCWT are compared with each other, and deviations ΔHU and ΔHW are output terminals.
Output to the slaves 305U and 305V. These deviations increase
Amplified by width units 306U and 306W and output terminal 307
U, 307W to W-phase voltage command vHU^* , ΔHW^* Got
It is.

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

Reference numeral 308 denotes an adder, which is a voltage command vHU ^{* for the} U and W phases ^. , VHW ^* Is added with the polarity shown in the figure, and the V-phase voltage command vHV ^* And output this from the output terminal 307V. Comparator 304U, 304W, amplifier 306U, 3
The part including the 06W 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 waves S1, S2 and S3 have a repetition frequency fm and are shifted in phase by 2/3.
The detailed operation will be described later. However, as shown in FIG.
When multiplexing INV3 and multiplexing N inverters, 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, respectively, constituting inverters INV1, INV2, and INV3 of FIG.
U2, V2, W2, X2, Y2, Z2, U3, V3, W
3, X3, Y3, and Z3.

Voltage fingers are provided at 310U, 320U and 330U.
Order vHU^* Are given, and 310V, 320V, 330V and
Each of 310W, 320W, and 330W has a voltage command v
HV^* , VHW^* Is input to one terminal, and the comparator 3
The other terminal of 10U, 310V, 310W has a triangle
The wave signal S1 is inputted, and the comparators 320U, 320V, 3
20W and 330U, 330V, 330W respectively
Angular wave signals S2 and S3 are input, and these voltage command values and three
The magnitudes of the square waves are compared, and inverters INV1, INV2, I
Generates gate pulses GP1, GP2, GP3 of NV3
You. Gate pulses GP1 to GP3 correspond to inverter I in FIG.
NV1 to INV3, based on which
The ignition is controlled.

Here, the comparators 310U and 3U shown in FIG.
Operations 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 ^* If it is larger, a gate pulse is issued to GX1 in FIG. 8 and S1 becomes vHU ^* GU1 when smaller
A gate pulse is issued. As a result, a so-called pulse width controlled (PWM control) voltage such as eU1 in FIG. 3 is generated on the line 412U of the inverter INV1 in FIG. 3B and 3C show the comparators 320U and 330, respectively.
The operation of U and the output voltages eU2, eU3 of the lines 422U, 432U of the inverters INV2, INV3 of FIG.

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

FIG. 10 shows this state. 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, iCUT is the current iCU1, iCU2,.
The current of power converter 400, iHUR, which is the composite value of iCU3
^* Is a harmonic current command. In this case, although the individual inverter currents iCU1, iCU2, and iCU3 include a considerably large ripple component, their combined value iCUT greatly reduces the ripple current due to the effect of shifting the phase of the triangular wave signals S1, S2, and S3. You can see how it is.

[0016]

The above is a conventional harmonic current compensator using a multiplexed inverter which has been used in the past, and this configuration has a harmonic current compensator iCUT to iCWT generated as a harmonic current compensator. Because it can greatly reduce the amount of ripple inside, it is used in conventional large-capacity harmonic compensators.

However, there are the following problems. That is, the harmonic current compensator uses the harmonic current command iHUR ^* , I
HWR ^* And a current controller 360 (FIG. 8) receiving the signal, and a power converter 400 (FIG. 9) controlled by the current controller 360 (FIG. 9) constitute a closed loop current control system. For this reason, the AC reactors 413 and 42 are used to improve the harmonic compensation performance.
It is necessary to design the inductance value of 3,433 (FIG. 9) as small as possible.

However, AC reactors 413 and 42
When the inductance value of 3,433 is reduced,
There is a disadvantage that the ripples of the individual currents of the inverters INV1 to INV3 increase (see that the ripples of iCU1 to iCU3 in FIG. 10 are large). When the ripple of the current of each inverter multiplexed in parallel increases, the current due to the ripple increases as compared with the current that should originally flow.To cope with this, the current capacity of the switching element of the inverter is increased. Must therefore,
The cost is high. Further, switching of a large ripple current increases switching loss and lowers efficiency. Further, AC reactors 413, 423, 433
Since a large ripple current flows through the core, various problems such as generation of harmonic loss in an iron core constituting the reactor come out.

As is clear from the above description, in the conventional harmonic compensator having the multiplexed configuration, the demand for improving the harmonic current compensating performance, that is, reducing the inductance value of the AC reactor → improving the current control response. Demands for improved efficiency and reduced device cost, that is, increasing the inductance value of the AC reactor → reducing the current ripple, and it is impossible to realize a device that satisfies these requirements simultaneously. The current situation is to design the device at the expense of both requirements.

Therefore, it can be understood from the above description that the harmonic compensator of the multiplex configuration should be capable of sufficiently increasing the current control response and sufficiently exhibiting the harmonic current compensating performance. Even in such a case, the device is a highly efficient and low-cost device, and it is desired to develop a device that satisfies these requirements.

Accordingly, an object of the present invention is to greatly reduce the current ripple of each inverter multiplexed in parallel by the action of the coupling reactor, and to multiplex any number of inverters in parallel by the design of the coupling reactor. This makes it possible to increase the capacity and reduce the size of the device.
Another object of the present invention is to provide a high-efficiency 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 polyphase inverter, and A harmonic current compensator for injecting the same into an AC power supply system to perform harmonic current compensation, the power supply system comprising a power converter having a multiplexed configuration in which N multi-phase inverters are combined. And an AC reactor according to the number of phases of the polyphase inverter, between the AC terminals of the polyphase inverter and the AC terminals of the N polyphase inverters. A plurality of coupling reactors each having a plurality of primary windings and a secondary winding corresponding to each of the AC terminals of the polyphase inverter are arranged, and one terminal of the secondary winding of the coupling reactor is connected to the terminal of the polyphase inverter. Connected to each AC terminal, the other terminal of the secondary winding of the coupling reactor is connected commonly to those belonging to the same phase of each polyphase inverter, and the primary winding of the coupling reactor is connected to each polyphase inverter. Inverters belonging to the same phase of the inverter are connected in series, and a common connection point of the secondary winding of the coupling reactor and one terminal of the primary winding connected in series are connected to each other belonging to the same phase of the multiphase inverter. And the other terminal of the series-connected primary winding of the coupling reactor is connected 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 multiplexed in parallel by the action of the coupling reactor can be greatly reduced, and the number of inverters can be multiplexed in parallel by the design of the coupling reactor. And therefore,
The capacity can be increased, the device can be downsized, and a high efficiency harmonic compensator can be realized.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a part of one embodiment of a harmonic compensator of the present invention, and FIG. 1 corresponds to FIG. Here, the differences between FIG. 1 and the conventional FIG. 9 will be mainly described, and the same parts as those in FIG. FIG. 1 shows a three-phase inverter INV1, INV2, IN
V3 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 transformer 355.

The coupling reactors 461U1 to 461 shown in FIG.
Each of the 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 a primary winding L01 and a secondary winding L02 are separated, and the number of turns N of the primary winding L01.
1 and the number of turns N2 of the secondary winding L02 are designed to have a relation of the number of turns N2 / N1 = N, where N is the number of multiplexed inverters. Similarly, coupling reactors 461U2-
461W3 is also configured.

In FIG. 1, each inverter INV1
To INV3 U-phase AC output terminals 412U, 422U,
432U are coupled reactors 461U1 and 461, respectively.
1U2, 461U3 are connected to one terminal of the secondary winding and coupled reactors 461U1, 461U2, 461U
3 are connected in common to each other, and further connected to the individual coupling reactors 461U from the common connection point.
The primary windings of 1,461U2, 461U3 are connected in series and connected to an AC reactor 460U.

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

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

The operation of the harmonic compensator configured as described above will be described. In FIG. 7, load currents of the cycloconverter 10 and the like are supplied to current detectors 32U and 32W.
, And the resulting signal is led to the controller 300 to detect a harmonic component, and a compensation current corresponding to the harmonic component is calculated as shown in FIG.
Of the power converter 400 is generated.

The power converter 400 comprises multiplexed inverters INV1 to INV3 shown in FIG. 1, and these are controlled by the PWM control method shown in FIG. Thus, the multiplexed inverter I of FIG. 1 is applied by using the PWM control method of FIG.
When NV1 to INV3 are operated, characteristics as shown in FIG. 4 are obtained.

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

Next, attention is paid to the currents iCU1, iCU2 and iCU3 in FIG. This current is applied to the individual inverters INV1 of FIG.
10 are obtained by comparing the currents of the same symbols in FIG. 10 obtained from the conventional FIG. 9 with those of the coupling reactors 461U1 to 461U in FIG.
It can be seen that the current ripple of the harmonic current compensator using 1W3 is remarkably reduced.

As described above, the harmonic compensator 4 shown in FIG.
No. 00 can greatly reduce the current ripples of the individual inverters INV1 to INV3 by the action of the coupling reactors 461U1 to 461W3.
Any number of inverters can be multiplexed in parallel by the design of 61W3, so that the capacity can be increased, the size of the device can be reduced, and a high-efficiency harmonic compensation device can be realized.

FIG. 5 shows the coupling reactor 461 shown in FIG.
U1-461W3 and AC reactor 460U-460W
This is another embodiment in the case where the arrangement is changed. That is, FIG. 5 shows a case where 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. The embodiment of FIG. 5 is characterized in that the number of AC reactors is increased as compared with the embodiment of FIG.

FIG. 6 shows one phase of the coupling reactor of FIG.
That is, the coupling reactors 461U1, 461U2, 461U
This is an embodiment in the case where 3 is manufactured as an integral reactor. In FIG. 6, the secondary windings L021, L02 in FIG.
022, L023 and the primary winding 3L01 are structurally arranged as shown in FIG. When three coupling reactors having this structure are used, the coupling reactor 4 shown in FIG.
Exactly the same effects as those of 61U1 to 461W3 can be obtained. With this structure, the volume of the coupling reactor can be reduced, which helps to reduce the installation space.

In the configuration shown in FIG.
Although three units of 0U to 460W are used, the effect of this reactor is adjusted by adjusting the degree of primary and secondary coupling in the coupling reactor shown in FIG. This can be achieved by providing an inductance. This eliminates the need to separately install an AC reactor, which helps to reduce the installation space.

[0037]

According to the present invention described above, the current ripples of the individual inverters multiplexed in parallel by the action of the coupling reactor can be significantly reduced, and the number of inverters can be multiplexed in parallel by the design of the coupling reactor. Therefore, the capacity can be increased, the device can be downsized, and a highly efficient harmonic compensator can be realized.

[Brief description of the drawings]

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

FIG. 2 is a view for explaining a configuration of a coupling reactor of FIG. 1;

FIG. 3 is a diagram for explaining the principle of current control of a controller.

FIG. 4 is a current waveform diagram for explaining the operation and effect of the harmonic compensator of FIG. 1;

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

FIG. 6 is a view for explaining a modification of the coupling reactor of FIG. 1;

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 of FIG. 7;

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

FIG. 10 is a current waveform diagram for explaining a problem of the harmonic compensator of FIG. 9;

[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 (INV
V2), 430 (INV3) ... inverter, 411, 4
21,431 ... DC power supply, 461U1-461W3 ... Coupling reactor, 460U-460W ... AC reactor,
355 ... voltage matching transformer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02J 3/01 H02M ⁷ /48-7/5395

Claims (1)

(57) [Claims] 1. A method for detecting a harmonic current of an AC power supply system, generating a compensation current having a phase opposite to the harmonic current by a polyphase inverter, and injecting the compensation current into the AC power supply system to perform harmonic current compensation. Wherein said polyphase inverter is:
A harmonic current compensator comprising a power converter having a multiplexed configuration by combining N units, wherein an AC of the N polyphase inverters is connected between the AC power supply system and an AC terminal of the N polyphase inverters. A plurality of coupling reactors having a plurality of primary windings and secondary windings corresponding to each of the terminals are arranged, and one terminal of the secondary winding of the coupling reactor is connected to each AC terminal of the polyphase inverter. The other terminal of the secondary winding of the coupling reactor is connected in common to those belonging to the same phase of each polyphase inverter, and the primary winding of the coupling reactor belongs to the same phase of each polyphase inverter. Things are connected in series,
A common connection point of the secondary windings of the coupling reactor and one terminal of the serially connected primary windings are connected to those belonging to the same phase of the polyphase inverter, and the serially connected primary windings of the coupling reactor are connected. A harmonic current compensator wherein the other terminal of the line is connected to the AC power supply system.