JP2754517B2 - 12 pulse rectification load harmonic compensation method - 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 compensator which is connected in parallel to a 12-pulse rectifier load and suppresses a harmonic current flowing into the load from flowing out to a power supply system.

[0002]

2. Description of the Related Art Harmonics for compensating input harmonic current of a 12-pulse rectifier comprising a common-mode transformer and a .DELTA.-Y transformer for converting a high voltage to a low voltage, and a first rectifier and a second rectifier. Compensation devices are known.

FIG. 2 shows a conventional 12-pulse rectification compensation system having such a harmonic compensation device. That is, in FIG. 2, a 12-pulse composed of a first rectifier 5 connected to the secondary side of the in-phase transformer 2 and a second rectifier 6 connected to the secondary side of the Δ-Y transformer 3 A rectifier rectifies the AC power from the system AC power supply 1 and supplies the rectified DC power to the load 4.

Numeral 30 indicates a 12-pulse rectification load to be compensated. The input currents i _{LU1 to} i _{LW1 of} the first rectifier 5 and the second
Any of the input current i _LU2 through i _LW2 rectifier 6 and the fundamental wave current (6n ± 1) contains a harmonic current of order harmonic.
Here, n is a positive integer.

However, the combined input currents i _{LU to} i _{LW of the} in-phase transformer 2 and the Δ-Y transformer 3 have an odd number of (6n ± 1) -order harmonics due to the phase conversion of both transformers. The harmonic currents of the components are canceled and eliminated, and the fundamental current and 11
It contains only the harmonic current of the (12n ± 1) order harmonic components such as the next and thirteenth orders.

In this case, the combined input currents i _{LU to} i _LU on the power supply side
_In order to compensate for the harmonic current of the (12n ± 1) order harmonic component contained in the _LW , a harmonic compensator 7 composed of a switching element is connected to the primary side of both transformers via a high-voltage receiving transformer 8. Is connected.

That is, the harmonic compensator 7 detects the U-phase and V-phase currents i _LU and i _LV of the input current of the 12-pulse rectifier by the current transformers 11 and 12, respectively. The circuit generates compensation currents i _{CU to} i _CW in the opposite phase to the harmonic current component of the (12n ± 1) order harmonic component, and converts the power supply currents i _{SU to} i _SW into sinusoidal currents without harmonics. It is something to make.

[0008]

The harmonic compensator 7 having the system configuration as described above compensates for the 12-pulse rectified high voltage side, so that the primary winding of the Δ-Δ connection or the YY connection is used. A harmonic compensator 7 composed of a switching element is connected via a high voltage receiving transformer 8 having the same winding as the secondary winding. Furthermore, the high-voltage switchboard 9 is connected to the power supply system side of the high-voltage receiving transformer 8 to disconnect the high-voltage receiving transformer 8 from the high-voltage system when the harmonic compensator 7 is stopped and to protect the system in the event of an overcurrent. doing. As described above, when compensating the load of the 12-pulse rectifier, since there is no current of harmonic components such as the fifth and seventh-order components, the capacity of the harmonic compensator 7 is reduced to the generally used 6-pulse rectifier. Since the load is reduced by half as compared with the case where the load (three-phase full-wave rectifier load) is compensated, it is preferably used for a large-capacity rectified load, but has a drawback that the above-described high-voltage equipment is required.

[0009]

According to the present invention, there is provided a harmonic compensator for compensating for a load of a 12-pulse rectifier, wherein a secondary winding on the low-voltage side of the in-phase transformer having the Δ-Δ connection or the YY connection. And the in-phase transformer and Δ
A current transformer for detecting input currents of two high-voltage receiving transformers of a -Y transformer, and a load resistor for obtaining an output signal of the current transformer, and an output signal V _GU based on a current flowing through the load resistor. ,
The harmonic compensator is operated according to V _GV .

[0010]

The current detected by the current transformer includes a harmonic current of a (12n ± 1) order harmonic component in addition to a fundamental component for supplying power to the rectifier load. In other words, the currents of the higher harmonic components of the fifth and seventh order components are mutually canceled out by the 12-pulse rectification function by the connection method of both transformers, and there is no compensation, so that the device capacity can be greatly reduced. However, since the effect of reducing the device capacity by the 12-pulse rectification occurs on the high voltage side which is an input to both transformers, it is necessary to connect a harmonic compensator for compensating for the effect.

In addition, a harmonic compensator composed of switching elements is generally a low voltage device because the withstand voltage of the switching elements is low. Therefore, in order to connect to the high voltage side, the phase of the current to be compensated is the same on the high voltage side and the low voltage side, so it is necessary to pass through a transformer of the same connection type of Δ-Δ connection or YY connection.

According to the present invention, one of the transformers constituting the 12-pulse rectifier has a primary, secondary or Δ-Δ connection or a Y-Y connection.
The secondary winding uses the same connection type in-phase transformer as the primary winding. In this case, in the primary and secondary windings of each transformer, the magnitude of the current flowing through both windings is multiplied by the number of turns. Therefore, a resistor for obtaining the output signal of the current transformer for detecting the input current of the receiving transformer is used. Is multiplied by the number of turns and converted to a low-voltage side current of a transformer to which the harmonic compensator is connected for control.

Accordingly, a 12-phase rectifying load to be compensated is constructed without adding a high-voltage switchboard for connecting to a high-voltage system and a special in-phase transformer for connecting to a low-voltage harmonic compensator. Using one transformer, a harmonic compensator can be installed.

[0014]

FIG. 1 shows the configuration of a principal part of an embodiment of a harmonic compensator when the present invention is applied to harmonic compensation of a 12-pulse rectifier.

In FIG. 1, 1 is a system AC power supply, 30 is a 12-pulse rectification load to be compensated, a common-mode transformer 2, a Δ-Y connection transformer 3, a load 4 such as a DC motor, a first rectifier 5
And the second rectifier 6. 7 is a harmonic compensator, and 11 and 12 are current transformers for detecting the input current of the 12-pulse rectifier load. The current transformer detects two phases of U-phase and V-phase. You may. Reference numerals 21 and 22 denote load resistors of a current transformer for controlling the harmonic compensator 7 by obtaining a current detection signal.

The current transformer 11 detects the U-phase input current i _SU of the combined current of the two transformers constituting the 12-pulse rectification, and the current transformer 12 detects the V-phase input current i _SV . Load resistance 21 and
Numeral 22 converts the current detected by the current transformer into voltage values _VGU and _VGV of the signal level controlled by the harmonic compensator 7, and outputs it to a control circuit (not shown) in the harmonic compensator. .

The detection currents i _SU and i _SV are detected on the high voltage side of two transformers constituting 12 pulse rectification. The harmonic compensator 7 that compensates the harmonic current flowing there
Since the withstand voltage of the switching device used in the device is low, the device has a low voltage of 200 V or 400 V.
Therefore, in order to inject the compensation current from the low voltage side, the transformer for converting the low voltage side current to the high voltage side current has a different current waveform to be compensated unless the primary and secondary windings have the same connection, Harmonics cannot be compensated.

In the present invention, of the two transformers constituting the 12-pulse rectifier, the in-phase transformer 2 having a Δ-Δ connection or a Y-Y connection is used, and the secondary (low voltage) of the in-phase transformer 2 is used. The harmonic compensator 7 is connected in parallel with the first rectifier 5 connected to the side ()).

Here, since the harmonic compensator 7 itself is a low voltage device, the control circuit of the present device controls the combined current inputs i _SU and i _SV detected on the high voltage side by converting them to the low voltage side. Therefore, the resistance values of the burden resistors 21 and 22 of the current transformer are selected so that a current signal whose number is equal to the number of turns of the in-phase transformer 2 is obtained, or the current calculation unit in the control circuit is replaced by the number of turns of the transformer 2 The coefficient is multiplied so as to obtain the ratio.

As described above, the current flowing in the power supply system is detected by 12-pulse rectification, the current to be compensated is converted to the low voltage side of the receiving transformer, the compensation current is controlled by the harmonic compensator, and the in-phase transformer is controlled. By injecting from the secondary side of
Harmonic compensation equivalent to the conventional method of compensating from the high voltage side can be performed.

[0021]

As described above, according to the present invention, a dedicated in-phase transformer for connecting the present harmonic compensator to a high-voltage system is obtained by diverting the in-phase transformer 2 constituting 12-pulse rectification. High-voltage receiving transformer 8
Can be omitted. Furthermore, a high-voltage switchboard 9 for opening and closing the input side of the transformer is not required, and a low-cost compensation system configuration can be provided.

Here, the current flowing through the transformer 3 on the Δ-Y connection side is the same as the conventional one, and the current flowing through the in-phase transformer 2 is the same as that of the conventional case where the high-voltage side is compensated. Current supplied to the first rectifier load including the above, and harmonic currents corresponding to two (12n ± 1) -order harmonic components generated by 12-pulse rectification such as 11th and 13th order among these harmonic components This is the sum of the components and the compensation current of the opposite phase.

That is, since the higher harmonic current of the latter component is compensated so as to cancel one component, the component of the other component does not change in magnitude and only its phase is opposite to that of the conventional one, and the voltage is transformed. The effective value of the current flowing through the transformer remains unchanged, so the transformer capacity is the same as in the prior art.

On the primary side of both transformers, harmonic current lines such as the fifth and seventh harmonics, which were not compensated by the harmonic compensator, are canceled between transformers having a 12-pulse rectification configuration. The power supply currents i _{SU to} i _SW flowing through the power supply system can be sinusoidal currents in which harmonic currents of all orders are suppressed.

As a result, the harmonic compensator 7 can be installed on the low voltage side, eliminating the need for high voltage equipment, and providing an inexpensive compensation system.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of an embodiment of a harmonic compensator when the present invention is applied to harmonic compensation of a 12-pulse rectifier.

FIG. 2 is a circuit diagram showing a conventional 12-pulse rectification compensation system including such a harmonic compensation device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 System AC power supply 2 In-phase transformer 3 Δ-Y transformer 4 Load 4 5 First rectifier 6 Second rectifier 7 Harmonic compensator 8 High-voltage receiving transformer 9 High-voltage switchboard 9 11, 12 Current transformer 21 , 22 Load resistance of current transformer 30 12-pulse rectified load to be compensated

Claims (1)

(57) [Claims] An in-phase transformer for converting high voltage to low voltage and Δ
A harmonic compensator for compensating input harmonic current of a 12-pulse rectifier comprising a Y transformer, a first rectifier and a second rectifier, comprising: a first rectifier on a secondary side of the in-phase transformer; And a harmonic compensator connected in parallel with one of the in-phase transformers connected in parallel.
A current transformer for detecting a combined current of the input current on the secondary side and the input current on the primary side of the Δ-Y transformer is connected, and the harmonic compensator is compensated by the output current of the current transformer. 12 pulse rectified load harmonic compensation method.