JPH0625950B2 - Reactive power compensator - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a reactive power compensator, and an effective reactive power compensation system in a system for supplying power from an AC power supply system to an AC power bus to a load with a large fluctuation of reactive power. The present invention relates to a reactive power compensator for performing power compensation.

[Technical background of the invention and its problems]

In recent years, large-capacity arc furnace equipment has been connected to an AC power supply system and operated. As is well known, the arc furnace generates reactive power on the power supply side that fluctuates abruptly depending on the state of the melt in the furnace. This abruptly changing reactive power distorts the voltage waveform due to the interaction with the power supply system impedance and causes flicker of the lighting equipment, and also causes a reduction in the utilization rate of the power supply equipment. Therefore, when installing a large-capacity arc furnace, etc., a reactive power compensator is installed in parallel with the arc furnace to compensate for the rapidly fluctuating reactive power generated by the arc furnace and to fluctuate the reactive power of the AC power system. Is suppressed.

For such a reactive power compensator, see [Reference] Technical Report of The Institute of Electrical Engineers of Japan (Part II), April 1979, 76th edition.
Nos. P26 to P31, "Power Conversion Technology for Reactive Power / Harmonics Countermeasures", edited by the rectifier permanent technical committee, the configuration is the power supply system as shown in FIG.

That is, in the figure, 10 is the load of the arc furnace,
Iron or the like is put into the furnace 12, and an electric current is caused to flow through the electrode 11 by electric discharge to heat and melt the iron inside. 9 is a transformer for the furnace.

Reference numeral 100 is a reactive power compensator, which is a reactor unit 300.
And a phase advancing capacitor section 200 that also serves as a harmonic filter. Reactor section 300 is reactor 302u-
302w and anti-parallel thyristor 30 connected in series to it
1u to 301w and load current detectors 81R, 81S, 8
1T, voltage detection transformer 70, and its control circuit 350
The reactive power of the arc furnace 10 is detected, the conduction angles of the thyristors 301u to 301w are adjusted in accordance with the detected value, and the reactor current is controlled. That is, in the reactive power compensator 100, the currents of the reactors 302u to 302w are controlled in combination with the action of the phase advancing capacitor 200, and the amount of lead reactive power equal to the generated reactive power (delay) of the arc furnace 10 is applied to the lines 51R, 51S, It is controlled to occur at 51T, and the reactive power disappears at the point of the three-phase bus 4 and only the active power of the load flows. Therefore, the voltage distortion of the bus bar 4 is reduced and the utilization rate of the power supply equipment is improved. Reference numeral 3 is a system impedance existing in a three-phase AC power supply system, and 1 is a power supply source such as a three-phase AC power supply system or a transmission and distribution bus.

In the reactive power compensator 100 having the above configuration, the control circuit 3
How accurately the reactive power generated by the load 10 is detected by 50 is a key to the device performance. An example of this reactive power detection circuit is shown in FIG.

That is, FIG. 6 shows a circuit disclosed in FIG. 2 of JP-A-59-139416. First, a 90 ° delayed phase waveform e _{90 of a} bus voltage e.
When the product q of the load current i _L and the load current i _L is created, q becomes a form that includes a direct current component (reactive power component) and an alternating current component that oscillates at twice the fundamental wave frequency. The direct current component q _VAR (amount indicating the reactive power) is detected through and the current of the reactor unit 300 is controlled based on the detected direct current component q _VAR .

Besides, various reactive power detection methods have been proposed, but the gist thereof can be reduced to the principle disclosed in Japanese Patent Laid-Open No. 59-139416.

The above is the description of the conventional reactive power compensator, but this device has the following drawbacks. That is, when fluctuating power generated by an arc furnace (including active power and reactive power) is analyzed, the component of the DC amount that does not fluctuate (that is, positive phase power due to positive phase voltage and positive phase current) ) And a fluctuating component (that is, the negative phase power caused by the positive phase voltage and the negative phase current), the conventional reactive power detection method clearly separates these positive phase power and negative phase power. There is no concept, therefore, the electric power is regarded only as a fluctuation component in which the positive-phase electric power and the negative-phase electric power are mixed together, and the reactor current is controlled based on the fluctuation. Therefore, what is to be compensated in the conventional reactive power compensator, that is, whether the positive-phase reactive power (component that does not fluctuate) is controlled or the negative-phase reactive power (component that fluctuates) is controlled. , Could not be identified in principle, and it was impossible to develop into more advanced control.

In recent years, there has been a strong demand for improving the quality of power in the AC power system,
In order to meet this demand, there is a strong demand for more advanced control of reactive power compensators for flicker countermeasures in arc furnaces, etc., and reactive power compensators for AC power system stabilization measures, and this requirement is satisfied. Therefore, the emergence of a reactive power compensator equipped with a new and accurate power detection method (including active and reactive components) based on a control concept is desired.

[Object of the Invention]

The present invention has been made in view of the above-mentioned problems of the prior art,
The purpose is to separate and detect the positive-phase component and the negative-phase component in the load current in a device that compensates the reactive power generated by the load of an arc furnace, etc. Another object of the present invention is to provide a reactive power compensator capable of performing highly accurate compensation control.

[Outline of Invention]

In order to achieve the above object, the present invention provides a reactive power compensator for compensating the reactive power generated by a load connected to an AC power supply system, wherein the voltage of each phase of an N-phase multi-phase AC bus to which the load is connected is Using a synchronized unit two-phase voltage signal and a two-phase current signal obtained by converting the detected load current into two phases in accordance with the voltage of each phase, positive signals in the load current are calculated by calculating these signals. It is characterized in that the phase reactive component and the anti-phase component are separately detected, a current command of the reactive power compensator is created based on this detection signal, and the reactive power compensator is controlled based on this current command.

Example of Invention

The power supply system provided with the reactive power compensator of the present invention is the same as that of FIG. 5, and the description of the elements mentioned in the description of the conventional example is omitted here.

In FIG. 5, reference numerals 81R, 81S and 81T denote current detectors, which detect the currents (i _RL , i _SL , i _TL ) of the arc furnace 10 and guide them to the control circuit 350. 70 is a voltage detector which is an arc furnace 1
0 (including the transformer 9 for the furnace) connected to the bus voltage (e
_RS , e _ST , e _TR ) is detected and guided to the control circuit 350. Reference numeral 300 denotes a reactor portion, which is usually delta connected, and the magnitude of the current is adjusted by adjusting the firing angle of the thyristors 301u to 301w. The reactor current usually has a distorted waveform including harmonics in addition to the fundamental wave.

Reference numeral 400 is an arithmetic circuit incorporating the present invention.
_RL , i _SL , i _TL and voltage signals e _RS , e _ST , e _TR are input, various calculations are performed, and a current command of a direct current value for instructing the fundamental current that the reactor unit 300 should flow ▲ I ^* _u ▼, ▲ I
Output ^* _v ▼, ▲ I ^* _w ▼.

Reference numeral 500 denotes an ignition controller, which is a current command value ▲ I ^* _u ▼, ▲ I
Operates in response to ^* _v ▼, ▲ I ^* _w ▼, ▲ I ^* _u ▼, ▲ I ^* _v ▼,
Thyristor 3 so that reactors 302u, 302v, 302w flow the current (fundamental wave component) indicated by ▲ I ^* _w ▼.
Ignition control is performed on 01u, 301v, and 301w.

A combination of the arithmetic circuit 400 and the ignition controller 500 is called a control circuit 350, and the details of this circuit are shown in FIG.

Next, the main part of the present invention will be described with reference to FIGS.
In the present invention, the following description will be given by taking the case where the reactor part 300 of FIG. 5 is delta-connected as an example. The same symbols in FIGS. 1 and 5 represent the same elements and the same signals.

In FIG. 1, reference numeral 402 is a line / phase converter, and the load currents i _RS , i _SL , and i _TL detected as the line current in FIG.
Delta connection phase currents i _uL , i _vL , and i _wL by the calculation of (1)
(The conversion of the formula (1) is performed by the reactor unit 30 in FIG.
0 is a necessary conversion when the delta connection is used, and this conversion is not necessary when the star connection is used).

406 inputs the AC bus voltage signals e _RS , e _ST , and e _TR of FIG. 5, and based on them, the phase lock loop circuit (PLL
Circuit) and the like, and is a two-phase signal generator obtained as its output. As its output, in FIG. 5, the first phase is the R phase and the second phase is the S phase.
Assuming that the phase and the third phase are the T phase, the unit sine wave signal ▲ e _1d ^* ▼ synchronized with the line voltage e _RS of the first phase and the second phase
Unit sine wave signal with 0 ° phase delay ▲ e _1q ^* ▼, and second
Unit sine wave signal synchronized with the phase-to-line voltage e _ST of the third and third phases ▲
e _2d ^* ▼ and unit sine wave signal with 90 ° phase delay ▲ e
^* _2q ▼, and the unit sine wave signal ▲ e ^* _3d ▼ synchronized with the line voltage e _TR of the third and first phases and the unit sine wave signal ▲ e ^* _3q ▼ with a 90 ° phase delay (Eq. 2) (Note that when reactor part 300 in FIG. 5 is star connected, ▲ e ^* _1d ▼, ▲ e ^* _1q ▼ are the phase voltage of the first phase, and ▲ e ^*
_2d ▼, ▲ e ^* _2q ▼ are for the second phase and ▲ e ^* _3d ▼, ▲ e ^* _3q ▼
Are respectively synchronized with the phase voltage of the third phase).

_{Reference numeral} 403 is a two-phase converter, which is a current signal i _uL , i _vL , i
_{The wL} is _subjected to a two-phase conversion based on the equation (3) in which the d axis is fitted to the line-to-line voltage e _{RS of} the first phase and the second phase (that is, ▲ e ^* _1d ▼ of the equation (2)), and The two-phase current signals i _1dL and i _1qL for the phases are calculated. Similarly, 404 is also a two-phase converter and has signals i _uL , i _vL ,
i _wL is the line voltage e _{ST of} the second and third phases (that is, equation (2)
Roh ▲ e _2d ^* ▼) to perform two-phase conversion based on the formula (4) obtained by combining the d-axis, two-phase current signal i _2dL for the second phase, calculates the _i 2qL. And 405 are also two-phase converters, and the signals i _uL , i _vL , i
_wL is the line voltage e _{TR of} the third phase and the first phase (that is, ▲ in equation (2)).
e _3d ^* ▼) is _subjected to two-phase conversion based on the equation (5) in which the d axis is matched, and two-phase current signals i _3dL and i _3qL for the third phase are calculated.

_{Reference numeral} 410A is an arithmetic distributor, the details of which will be described later with reference to FIG. 2, but the signals i _1dL , i _1qL , i _2dL , i _2qL ,
i _3dL , i _3qL and ▲ e ^* _1d ▼, ▲ e ^* _1q ▼, ▲ e _2d ^* ▼,
Current command values I _u *, I _v *, for instructing the current flowing through the reactor unit 300 shown in FIG. 5 by performing calculations upon receiving ▲ e _2q ^* ▼, ▲ e _3d ^* ▼, ▲ e _3q ^* ▼. Output I _w *.

Reference numeral 500 denotes an ignition controller, which is a current command value ▲ I _u ^* ▼, ▲ I.
^{_{v * ▼, ▲ I w *}} ▼ operates by receiving ^{_{the, ▲ I u * ▼, ▲}} I v * ▼,
▲ I _w ^* ▼ at the indicated current thyristor to (fundamental component) of the reactor 300 is passed 301u, 301V, to Tenko control 301W.

Next, the operation distributor 410A will be described with reference to FIG. First
Signals having the same symbols in the drawings and FIG. 2 are connected according to the symbols. In FIG. 2, 411A is an arithmetic unit which _inputs signals i _1dL , i _1qL and ▲ e _1d ^* ▼, ▲ e _1q ^* ▼,
The signals Q _1P , Q _1N and P _1N are calculated by (6).

When the load currents i _RL , i _SL , and i _TL include a positive phase component and a negative phase component, Q _1P , Q _1N , and P _1N are pulses that include a DC component and an AC component that oscillates at twice the fundamental frequency. It becomes a flow.

412A and 413A are also arithmetic units, each of which has a signal i
_2dL , i _2qL and ▲ e ^* _2d ▼, ▲ e ^* _2q ▼ and i _3dL , i _3qL and ▲ e ^* _3d ▼, ▲ e ^* _3q ▼ are received and the signal Q is calculated by the equations (7) and (8). _2N , P _2N , and Q _3N , P _3N are output. These signals Q _2N , P _2N and Q _3N , P _3N also have load currents i _RL ,
When i _SL and i _TL include a positive phase component and a negative phase component, the pulsating flow includes a direct current component and an alternating current component that oscillates at twice the frequency of the fundamental wave.

Reference numerals 421 to 427 denote direct-current detection filters, which detect the direct-current components of the signals Q _1P , Q _1N , P _1N , Q _2N , P _2N , Q _3N , P _3N , respectively, and output the signals Q _1PD , Q _1ND , P _1ND , respectively.
Output as Q _2ND , P _2ND , Q _3ND , P _3ND . The DC amount signal thus obtained represents the following amount. That is,
The signal Q _1PD represents the positive phase reactive current contained in the load currents i _RL , i _SL , and i _TL . And the signals P _1ND and Q _1ND are the first signals of the equation (1).
The reverse-phase current contained in the phase current i _uL is decomposed into a component (P _1ND ) in phase with the line voltage of the first phase and the second phase and a component (Q _1ND ) different in phase from it by 90 °. Current, where P _1ND is the in-phase and in-phase current signal of the first phase, Q 1
_1ND will be referred to as the first-phase 90 ° anti-phase current signal.
Similarly, the signals P _2ND and Q _2ND are the components in phase with the opposite phase component of the second phase current i _vL of the equation (1) in the line voltage of the second phase and the third phase, and the component different in 90 ° phase from it. In-phase component current (P _2ND ) when decomposed into two, 90 ° phase difference current component (Q _2ND )
Is represented. Also, the signals P _3ND and Q _{3ND convert} the _antiphase component of the third phase current i _wL of the equation (1) into the in-phase component of the line voltage of the third phase and the first phase and the component of 90 ° phase difference from that. The in-phase component current (P _3ND ) when decomposed and the current component (Q _3ND ) having a 90 ° phase difference are shown. Here, P _2ND , Q
_2ND, P _3ND , and Q _3ND are _connected to the second phase in-phase current signal (P
_2ND ), 90 ° negative phase current signal of the second phase (Q _2ND ), and
Third-phase in-phase reverse-phase current signal (P _3ND ), third-phase 90 °
It is called a reverse-phase current signal (Q _3ND ).

The signals Q _1PD , Q _1ND , P _1ND , Q _2ND and P thus obtained
_2ND , Q _3ND and P _3ND are input to the next distributor 440A.

Next, 447 is a setting device, which is the reactor unit 300 shown in FIG.
Outputs a reactive current setting signal Q _1MAX for instructing the lowest value of the reactive current (delay) that should be generated.

440A is a distributor, in which the positive phase reactive current signal Q _1PD detected from the load current of the arc furnace, the first phase,
Second-phase and third-phase 90 ° negative-phase current signals Q _1ND , Q _2ND , Q
_{Input 3ND} , in-phase and out-of-phase current signals P _1ND , P _2ND , P _3ND and reactive current setting signal Q _1MAX , and formula based on these signals
The calculation of (9) is performed, and the reactor unit 30 of FIG.
No. 0 first phase current command ▲ I _u ^* ▼ for indicating the current to be generated by the first phase reactor 302u, and similarly, second phase current command ▲ I _v ^* ▼ for the reactor 302v and It outputs the third-phase current command I _w * for the reactor 302w. Here, the following elements are included in the distributor 440A. That is, 441A, 442A, 443A
Is a coefficient unit and Double and output. 444A, 445A and 446A are adders which add the outputs of the coefficient units 441A, 442A and 443A with the polarities shown. Adders 444A, 445A, 4
The output of 46A corresponds to the calculation of the third term of Expression (9). 44
_{Reference numeral} 8A is an adder that calculates the setting signal Q _1MAX and the signal Q _1PD with the polarities shown in the figure. That is, the output of the adder 448A corresponds to the calculation of the first term of the equation (9). 449A, 450A, 451
A is an adder, and signals Q _1ND , Q _2ND , Q _3ND and adder 4
48A output signal and adders 444A, 445A, 44
The output signals of 6 A are added with the polarities shown.

The signals I _u *, I _v *, and I _w * obtained by the above calculation are DC amount signals, and this signal includes all the information about the positive-phase current and the information about the negative-phase current. Therefore,
By controlling the reactor unit 300 of FIG. 5 based on these ▲ I _u ^* ▼, ▲ I _v ^* ▼, and ▲ I _w ^* ▼, the load current of the arc furnace or the like is added to the positive phase component and the negative phase component. The current at point 4 in FIG. 5 can be freely balanced even if it contains a large amount.

The above is a typical configuration of the present invention.

Next, the operation of the present invention will be described.

First, in FIG. 5, the electric current of the arc furnace is the signal i _RL ,
Although detected as i _SL and i _TL , this current is usually an unbalanced current including a positive phase component and a negative phase component. On the other hand, the power source bus voltage to which the arc furnace is connected is also the signal e _RS , e _ST , e.
_It is detected as _TR and is introduced into the control circuit of the reactive power compensator 100. Next, referring to FIG. 1, a two-phase generator 406
Is a two-phase signal ▲ e ^* _1d ▼, ▲ _e1q ^* ▼ (the line voltage e of the first phase and the second phase e based on the equation (2) in response to the signals e _RS , e _ST , e _TR.
(Synchronized with _RS ) and signals ▲ e _2d ^* ▼, ▲ e _2q ^* ▼ (synchronized with the line voltage e _ST of the third phase and the first phase).

On the other hand, the signals i _RL , i _SL , and i _TL detected as the line currents are converted by the equation (1) in the line / phase converter 402,
As a result, the phase currents i _uL , i _vL , and i _wL of the delta connection (that is, the reactor section 30 in the delta connection of FIG. 5 for example).
Taking 0 as an example, the reactors 302u, 302v, 302
corresponding to the current flowing through w). This signal i
_uL , i _vL , and i _wL are the following two-phase converters ₄₀₃ , ₄₀₄ , and _40.
5 is converted by the equations (3), (4) and (5), and the two-phase current signal i in which the d axis is aligned with the line voltage e _RS of the first phase and the second phase
_1dL , i _1qL , two-phase current signals i _2dL , i _2qL in which the d axis is aligned with the line voltage e _ST of the second and third phases, and the line voltage e _{TR of} the third and first phases Two-phase current signal i with d axis aligned to
_3dL and _i3qL are obtained. The signal i _1dL thus obtained,
i _1qL , i _2dL , i _2qL , i _3dL , i _3qL and ▲ e ^* _1d ▼, ▲
e ^* _1q ▼, ▲ e ^* _2d ▼, ▲ e ^* _2q ▼, ▲ e ^* _3d ▼, ▲ e ^* _3q
▼ is input to the arithmetic distributor 410A.

Next, in the operation distributor 410A shown in FIG.
In 11A, the signals ▲ e _1d ^* ▼, ▲ e _1q ^* ▼, i _1dL , i _1qL are input to obtain the signals Q _1P , Q _1N , P _1N by the calculation of the equation (6), and in the calculator 412A, the signal ▲ e _2d ^* ▼, ▲ e _2q ^*
The signals Q _2N and P _2N are obtained by the calculation of the equation (7) to which ▼, i _2dL and i _2qL are input, and the signal ▲ is calculated by the calculator 413A.
^{_{e * 3d ▼, ▲ e 3q}} * ▼, it 3dL, signal Q _3N by calculation of i _3QL is input expression (8), P _3N is obtained. These signals Q
_1P , Q _1N , P _1N , Q _2N , P _2N , Q _3N , P _3N are the following DC detection filters 421, 422, 423, 424, 425.
426, 427, the DC component in the signal is detected, and the DC amount signals Q _1PD , Q _1ND , P _1ND , Q _2ND , P _2ND ,
Q _3ND and P _3ND are obtained.

The signal Q _1PD of the DC amount thus obtained is the load current signal i
_RL , i _SL , i _TL (or may be paraphrased as i _uL , i _vL , i _{wL in the} equation (1)) represent the positive-phase reactive current, and the signals P _1ND and Q _1ND are First phase current i _{uL of} equation (1)
Each of the component currents when the negative-phase current included in is decomposed into a component having the same phase as the line voltage of the first phase and the second phase and a component having a 90 ° phase difference from that, that is, the common-mode current component P _1ND (of the first phase In-phase and anti-phase currents) and 90 ° phase-different current components Q _1ND (first
90 ° reverse-phase current of the phase). And P _2ND , Q
_2ND is the in-phase reverse-phase current P _2ND of the second phase and the 90 ° reverse-phase current Q _2ND of the second phase. Similarly, P _3ND and Q _3ND are a third-phase in-phase reverse-phase current P _3ND and a third-phase 90 ° reverse-phase current Q _3ND .

The signal Q _1PD obtained as described above is the load current i _RL ,
i _SL , i _TL is a signal related only to the positive-phase component current, and further, if the positive-phase component current can be decomposed into an active current and a reactive current, it is only related to the reactive current. I.e., a signal related only to the positive-phase reactive current. In the calculation of various quantities related to the positive phase of the current, for example, the conversion of Q _{1P in the} equation (6), the same quantity is calculated regardless of which phase the calculation is performed. Therefore, the calculation for the positive phase component may be performed for one phase.

Also, the signals P _1ND , Q _1ND and P _2ND , Q _2ND and P
_{Focusing on 3ND} and Q _3ND , these signals are
It is a signal related only to the negative-phase component current contained in i _uL , i _vL , and i _wL (or may be paraphrased as i _RL , i _SL , and i _TL ) in (1), and further, P _1ND , Q _1ND is only for the _{antiphase component} of the current i _uL , P _2ND , Q _2ND is only for the _{antiphase component} of i _vL , P
_3ND and Q _3ND are signals related only to the reverse phase _component of the current i _wL . More specifically, taking P _1ND and Q _1ND as an example, P
_1ND is a current component in phase with the line voltage in the antiphase component of the current i _uL , and Q _1ND is a signal related only to the current component that is 90 ° out of phase with the voltage.

As described above, all the information of the load currents i _RL , i _SL , and i _TL are DC signals Q _1PD , P _1ND , P _2ND , P _3ND , Q _1ND , Q _2ND , Q.
It will be clear that they are separately detected in the form of _3ND .

The signals thus obtained are distributed along the equation (9) in the distributor 440A of FIG. 2 and the current commands ▲ I _u ^* ▼, ▲ I _v ^* ▼, ▲
I ^* _w ▼ is made, but this current command ▲ I _u ^* ▼, ▲ I _v ^* ▼, ▲
When the current of the reactor part of FIG. 5 is controlled on the basis of I _w ^* , the anti-phase current is controlled by the anti-phase current of the current generated by the arc furnace and the compensation current generated by the reactor part 300. Since the phases of the anti-phase currents are controlled so that they are exactly opposite to each other, these are the points 51 for the anti-phase currents.
R, 51S, and 51T are combined at the R, 51S, and 51T and cancel each other, so that the negative-phase current does not flow toward the power source 1 and the current of the power source 1 is balanced. Next, regarding the positive-phase reactive current, the output signal of the adder 448A of FIG. 2 acts, and as a result, the positive-phase reactive component (delay) of the current generated by the load and the generation of the reactor unit 300 of FIG. The sum of the compensation current and the positive-phase reactive component (delay) is controlled to be exactly equal to the reactive current setting signal Q _1MAX (delay) in FIG. Fifth
The leading reactive currents of the phase advancing capacitor 200 in the figure cancel each other out, and as a result, the reactive current no longer flows toward the AC power supply 1 in FIG. 5, and only the positive phase active current generated by the load flows in the AC power supply. Will flow.

From the above description, when the reactive power compensator of the present invention operates, even if the load of the arc furnace or the like generates an unbalanced current including a positive phase component and a negative phase component, the reactive current is compensated, and the reverse current is compensated. Since the phase current is compensated, only the positive-phase active current flows through the AC power supply, and therefore the voltage fluctuation (that is, flicker).
It can be seen that the power consumption can be improved (that is, reactive power does not have to be handled) and the power consumption can be suppressed.

The above is a typical embodiment of the present invention.

Next, another embodiment of the present invention will be described with reference to FIG. That is, FIG. 3 shows the operation distributor 410 of FIG.
FIG. 3 is a modification of A, and FIG. 3 shows the operation distributor 410 of FIG.
It is inserted in A and used. Therefore, this modified example has many parts that overlap with the invention described above, and the description of the overlapping parts will be omitted. The same symbols in FIGS. 3 and 1 are connected according to the symbols.

In FIG. 3, 411B is a computing unit, which is the first unit described above.
The two-phase current signals i _1dL and i _1qL of the phase and the two-phase voltage signals ▲ e _1d ^* ▼ and ▲ e _1q ^* ▼ of the first phase are input, and the signals Q _1P and Q _1N are calculated by the equation (10).

These Q _1P and Q _1N are the same as the signals Q _1P and Q _1N obtained by the above-mentioned equation (6). Reference numerals 412B and 413B are also arithmetic units, and each of the above-mentioned second-phase two-phase current signal i
_2dL , i _2qL , two-phase voltage signal ▲ e _2d ^* ▼ ・ ▲ e _2q ^* ▼ and the third
Two-phase current signal i _3dL , i _3qL , two-phase voltage signal ▲ e _3d ^*
▼ and ▲ e _3q ^* are input, and the signals Q _2N and Q _3N are calculated by the equations (11) and (12).

Q _2N = ▲ e _2d ^* ▼ ・ i _2qL − (-▲ e _2q ^* ▼) ・ i _2dL … (1
1) Q _3N = ▲ e _3d ^* ▼ ・ i _3qL − (− ▲ e ^* _3q ▼) ・ i _3dL … (1
2) These Q _2N and Q _3N are the same as the signals Q _2N and Q _3N obtained by the equations (7) and (8) described above.

Next, these signals Q _1P , Q _1N , Q _2N and Q _3N are passed through DC detection filters 421, 422, _{424 and 426} to obtain DC component signals Q _1PD , Q _1ND , Q _2ND and Q _3ND .

Here, Q _1PD is a positive-phase reactive current signal, Q _1ND is the first-phase 90 ° negative-phase current signal, Q _2ND is the second-phase 90 ° negative-phase current signal, and Q _3ND is the third-phase 90 ° This is a negative-phase current signal.

A setter 447 outputs a reactive current setting signal Q _1MAX . 440B is a distributor, which is a positive-phase reactive current signal Q
_1PD , 1st phase, 2nd phase, 3rd phase 90 ° negative phase current signal Q
_1ND , Q _2ND , Q _3ND and reactive current setting signal Q _1MAX are input, and the calculation of formula (13) is performed based on these signals, and the first
Phase, second phase, third phase current command ▲ I _u ^* ▼, ▲ I _v ^* ▼, ▲
Output I _w ^* ▼.

Here, 453B, 454B, and 455B are coefficient multipliers, which double the input signal and output it. Also, 448A, 449
B, 450B, and 451B are adders, which add the illustrated signals with the illustrated polarities.

The current commands ▲ I _u ^* ▼, ▲ I _v ^* ▼, and ▲ I _w ^* ▼ are the expressions described above.
It is exactly the same as the current command value obtained in (9). Therefore, the fifth value is obtained based on these ▲ I _u ^* ▼, ▲ I _v ^* ▼, and ▲ I _w ^* ▼.
If the current of the reactor portion 300 in the figure is controlled, the same compensation effect as that of the invention according to FIGS. 1 and 2 described above can be obtained.

As described above, in this embodiment, the arithmetic units 411B and 412 shown in FIG.
The calculation of B and 413B is performed by the calculators 411A and 41 of FIG.
2A and 413A can be simplified.

Next, another embodiment of the present invention will be described with reference to FIG. This embodiment also relates to the modification of the above-mentioned invention shown in FIG. 2, and FIG. 4 shows the arithmetic distributor 410 shown in FIG.
Inserted in A. Therefore, the description of the same parts as those of the above-mentioned invention will be omitted.

In FIG. 4, reference numeral 411C denotes an arithmetic unit, which is a first-phase two-phase current signal i _1dL , i _1qL and a first-phase two-phase voltage signal ▲ e _1d.
Input signals ^* ▼ and ▲ e ^* _1q ▼, and the signals Q _1P and Q _1N are calculated by the equation (14).

These Q _1P and P _1N are the same as the signals Q _1P and P _1N obtained by the above-mentioned equation (6). Reference numerals 412C and 413C are also arithmetic units, and each of the above-mentioned second-phase two-phase current signals i
_2dL , i _2qL , two-phase voltage signal ▲ e ^* _2d ▼, ▲ e ^* _2q ▼ and the third
Two-phase current signal i _3dL , i _3qL , two-phase voltage signal ▲ e ^* _3d
▼ and ▲ e ^* _3q ▼ are input, and the signals P _2N and P _3N are calculated by the equations (15) and (16).

P _2N = ▲ e _2d ^* ▼ ・ i _2dL + (-▲ e _2q ^* ▼) ・ i _2qL … (1
5) P _3N = ▲ e _3d ^* ▼ ・ i _3dL + (-▲ e _3q ^* ▼) ・ i _3qL … (1
6) The P _2N and P _3N are the same as the signals P _2N and P _3N obtained by the equations (7) and (8) described above.

Next, these signals Q _1P , P _1N , P _2N and P _3N are passed through DC detection filters 421, 423, _{425 and 427} to obtain DC component signals Q _1PD , P _1ND , P _2ND and P _3ND .

Here, Q _1PD is a positive-phase reactive current signal, P _1ND is a first-phase in-phase reverse-phase current signal, P _2ND is a second-phase in-phase reverse-phase current signal, and P _3ND is a third-phase in-phase reverse-phase current signal. It is a signal.

A setter 447 outputs a reactive current setting signal Q _1MAX . 440C is a distributor, which is a positive-phase reactive current signal Q
_{Input 1PD} , first-phase, second-phase, third-phase in-phase reverse-phase current signals P _1ND , P _2ND , P _3ND and reactive current setting signal Q _1MAX, and calculate equation (17) based on these signals. The current command for the first phase, the second phase, and the third phase ▲ I ^* _u ▲, ▲ I ^* _v ▲,
Output ▲ I ^* _w ▲. Here, 441A, 442A, 4
43A is a coefficient unit for input signal Double and output. 453B, 454B and 455B are also coefficient units, which double the input signal and output it. Also, 444
A, 445A, 446A, 448A, 449B, 450
Reference numerals B and 451B denote adders that add the illustrated signals with the illustrated polarities.

The current commands ▲ I _u ^* ▼, ▲ I _v ^* ▼, and ▲ I _w ^* ▼ are the expressions described above.
It is exactly the same as the current command value obtained in (9). Therefore, the current of the reactor part 300 of FIG. 5 is controlled based on these ▲ I ^* _u ▼, ▲ I ^* _v ▼, and ▲ I ^* _w ▼. Then, the above-mentioned first
The same compensation effect as the invention according to FIGS. 2 and 3 can be obtained.

As described above, in this embodiment, the arithmetic units 411C and 412 shown in FIG.
The calculation of C and 413C is performed by the calculators 411A and 412 of FIG.
A, 413A can be simplified.

〔The invention's effect〕

As is clear from the above description, the reactive power compensator of the present invention has the following effects. That is, (1) the current generated by a fluctuating load such as an arc furnace is an unbalanced current containing a large amount of reverse phase components together with the positive phase components, but in the present invention, these positive phase components and reverse phase components are clearly defined. Since it can be detected separately, the target to be compensated by the reactive power compensator becomes clear, that is, the control focusing only on the positive-phase reactive power, the control focusing on only the negative-phase current, or the current balancing control (negative-phase control). Current compensation) can be prioritized and positive-phase reactive power compensation can be performed only when there is remaining capacity in the device (priority control), etc. can be freely configured, and more advanced compensation control can be performed easily compared to the conventional control. realizable.

(2) Even if the load current fluctuates, the positive phase component and the negative phase component can be continuously detected in the form of a DC signal regardless of the lead power factor / lag power factor. Since it does not enter, stable compensation control can be realized.

(3) In the control circuit, when detecting the positive-phase component and the negative-phase component of the load current, simple elements such as a coefficient unit, an adder, and a multiplier are used as signal processing means to perform a simple calculation. Only the desired signal is obtained, and an accurate and highly accurate signal (regarding the positive phase component and the negative phase component) can be obtained without any ambiguity in the detection signal. In addition, the cost is low because the circuit is simple.

(4) Therefore, in the reactive power compensator according to the present invention, since the information regarding the positive-phase current / negative-phase current is accurately separated and detected, even if the load fluctuates rapidly like an arc furnace, Since it is possible to perform control by clarifying the target of compensation (that is, whether to control the positive-phase reactive current, the negative-phase current, etc.), stable and highly accurate reactive power compensation can be performed.

As described above, the reactive power compensator of the present invention incorporates a completely new control concept that "the positive phase component and the negative phase component are separately detected and the compensation control is performed based on them" which is not in the conventional control. Therefore, it is possible to sufficiently meet the demand for the reactive power compensation control which will be complicated and sophisticated in the future.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIGS. 2 to 4 are block diagrams showing other embodiments of the present invention, and FIG. 5 is an invalidity to which the present invention is applied. FIG. 6 is a main circuit diagram of the power compensator, and FIG. 6 is a block diagram of a reactive power detection circuit adopted in a conventional reactive power compensator. 1 ... AC power supply system, 3 ... System impedance, 9, 10
… Arc furnace equipment, 100… Reactive power compensator, 200…
Phase advancing capacitor, 300 ... Reactor section, 350 ... Control circuit, 400 ... Arithmetic circuit, 500 ... Firing control circuit, 40
2 ... Line / phase converter, 403-405 ... 2 phase converter, 40
6 ... Two-phase generator, 410A ... Arithmetic distributor, 500 ... Pointing controller, 411A-413A, 411B-413B, 4
11C to 413C ... Operation unit, 421 to 427 ... DC detection filter, 447 ... Setting device, 441A to 443A, 45
3B to 455B ... Coefficient unit, 444A to 446A, 448
A to 451A ... Adder.

Claims (4)

[Claims] 1. A reactive power compensator for compensating unbalanced power and reactive power generated by a load connected to a polyphase AC power supply system, comprising: a first phase, a second phase, and a first phase of an N-phase / polyphase AC power supply. Unit sine wave signals ▲ e ^* _1d ▼, ▲ e synchronized with 3rd to Nth phase voltage
^* _2d ▼, ▲ e ^* _3d ▼ ... ▲ e ^* _Nd ▼ and 90 ° to it
Unit sine wave signal with phase delay ▲ e ^* _1q ▼, ▲ e ^* _2q ▼, ▲
e ^* _3q ▼ ... ▲ e ^* _Nq ▼ means and N-phase / multi-phase load currents i _1L , i _2L , i _3L・ ・ ・ i _NL are detected, and from these load currents, the voltage of the first phase is respectively detected. To d
Two-phase current signals i _1dL and i _1qL are performed by performing two-phase conversion with the axes aligned.
To obtain the two-phase current signals i _2dL and i _2qL by the two-phase conversion in which the d-axis is adjusted to the second-phase voltage, and the two-phase current is obtained by the two-phase conversion in which the d-axis is adjusted to the third-phase voltage. _Means for obtaining the signals i _3dL , i _3qL and sequentially performing the same conversion to obtain the N-phase two-phase current signals i _NdL , i _NqL , and the signals ▲ e ^* _1d ▼, ▲ e ^* _2d ▼, ▲ e ^* _3d ▼ 〜 ▲ e
^* _Nd ▼, ▲ e ^* _1q ▼, ▲ e ^* _2q ▼, ▲ e ^* _3q ▼ ~ ▲ e ^* _Nq ▼
And i _1dL , i _1qL , i _2dL , i _2qL , i _3dL , i _{3qL to} i
_And means for creating current commands for the first phase, second phase, third phase to Nth phase of N-phase / multi-phase alternating current by performing calculation with _NdL and i _NqL as input signals. A reactive power compensator for controlling the reactive power compensator based on a current command. 2. A means for creating the current command, means for setting a reactive current setting signal Q _1MAX for instructing the maximum value of the reactive power to be compensated by the reactive power compensator, and the signal ▲ e ^* _1d. Using ▼, ▲ e ^* _1q ▼ and i _1dL , i _1qL , Q _1P = ▲ e ^* _1d ▼ ・ i _1qL − ▲ e ^* _1q ▼ ・ i _1dL P _1N = ▲ e ^* _1d ▼ ・ i _1dL − ▲ e ^* _1q ▼ ・ i _1qL Q _1N = ▲ e ^* _1d ▼ ・ i _1qL + ▲ e ^* _1q ▼ ・ i _1dL means for obtaining the signals Q _1P , P _1N , Q _1N , and the signal ▲ e ^* _2d Using ▼, ▲ e ^* _2q ▼ and i _2dL , i _2qL , P _2N = ▲ e ^* _2d ▼ ・ i _2dL − ▲ e ^* _2q ▼ ・ i _2qL Q _2N = ▲ e ^* _2d ▼ ・ i _2qL + ▲ e ^* _2q ▼ · i _2dL is calculated to obtain signals P _2N and Q _2N , and P _3N = ▲ e ^* _3d using the signals ▲ e ^* _3d ▼, ▲ e ^* _3q ▼ and i _3dL , i _{3qL ^{▼ · i 3dL - ▲ e *}} 3q ▼ · i 3qL Q 3N = ▲ e * 3d ▼ _{^{i 3qL + ▲ e * 3q ▼}} · i 3dL signal P _3N performs an operation of, the means for obtaining the Q _3N, the signal _{Q 1P, P 1N, Q 1N} , P 2N, Q 2N, DC P _3N, Q _3N The components are detected and the signals Q _1PD , P _1ND , Q _1ND , P _2ND , Q
_Means for obtaining _2ND , P _3ND , Q _3ND , and said signals Q _1MAX , Q _1PD , Q _1ND , Q _2ND , Q _3ND ,
Based on P _1ND , P _2ND , P _3ND The current command signals ▲ I ^* _u ▼, ▲ I ^* _v ▼, ▲ I ^* _w are calculated.
3. The reactive power compensator according to claim 1, further comprising: means for creating ▼. 3. A means for creating the current command, means for setting a reactive current setting signal Q _1MAX for instructing a maximum value of reactive power to be compensated by the reactive power compensator, and the signal ▲ e ^* _1d. Using ▼, ▲ e ^* _1q ▼ and i _1dL , i _1qL , Q _1P = ▲ e ^* _1d ▼ ・ i _1qL − ▲ e ^* _1q ▼ ・ i _1dL Q _1N = ▲ e ^* _1d ▼ ・ i _1qL + ▲ e ^* _1q ▼ · i _1dL calculation means to obtain signals Q _1P and Q _1N , and the signals ▲ e ^* _2d ▼, ▲ e ^* _2q ▼ and i _2dL , i _2qL , and ▲.
Using e ^* _3d ▼, ▲ e ^* _3q ▼ and i _3dL , i _3qL , Q _2N = ▲ e ^* _2d ▼ ・ i _2qL + ▲ e ^* _2q ▼ ・ i _2dL Q _3N = ▲ e ^* _3d ▼ ・ i _3qL + ▲ e ^* _3q ▼ · i signal Q _2N performs an operation of _{3 dL,} means for obtaining the Q _3N, the signal _{Q 1P, Q 1N, Q 2N} , Q 3N of the DC component to detect a signal Q _1PD, Q _1ND, Q _2ND, Q means for obtaining _3ND, the signal _{Q 1MAX, Q 1PD, Q 1ND} , Q 2ND, Q 3ND, on the basis _{^{▲ I * u ▼ = -Q 1MAX}} + Q 1PD -2Q 1ND ▲ I * v ▼ = -Q _1MAX + Q _1PD -2Q _2ND ▲ I ^* _w ▼ = -Q _1MAX + Q _1PD -2Q _3ND , and current command signals ▲ I ^* _u ▼, ▲ I ^* _v ▼, ▲ I ^* _w
3. The reactive power compensator according to claim 1, further comprising: means for creating ▼. 4. A means for generating the current command, means for setting a reactive current setting signal Q _1MAX for instructing a maximum value of reactive power to be compensated by the reactive power compensator, and the signal ▲ e ^*. _{Using 1d} ▼, ▲ e ^* _1qL ▼ and i _1q , i _1qL , Q _1P = ▲ e ^* _1dL ▼ ・ i _1qL − ▲ e ^* _1q ▼ ・ i _1dL P _1N = ▲ e ^* _1d ▼ ・ i _1dL − ▲ _e ^* _1q ▼ · i 1qL operation was carried out signals Q _1P, the means for obtaining a P _1N, the signal _{^{▲ e * 2d ▼, ▲ e}} * 2q ▼ and _{i 2dL,} i 2qL, and ▲
_{^{e * 3d ▼, ▲ e *}} 3q ▼ and _i 3dL, P using the _{^{i 3qL 2N = ▲ e * 2d}} ▼ · i 2dL - ▲ e * 2q ▼ · i 2qL P 3N = ▲ e * 3d ▼ · i 3dL - ▲ e ^* _3q ▼ and · i signal P _2N performs an operation of _3QL, means for obtaining a P _3N, the signal _{Q 1P, P 1N, P 2N} , P 3N of the DC component of the detected signal Q _1PD, P _1ND, P _2ND, means for obtaining a P _3ND, the signal _{Q 1MAX, Q 1PD, P 1ND} , P 2ND, based on P _3ND The current command signals ▲ I ^* _u ▼, ▲ I ^* _v ▼, ▲ I ^* _w are calculated.
5. The reactive power compensator according to claim 1, further comprising: