JP3374827B2 - Reactive power generator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive power generator for suppressing voltage flicker in a power system due to fluctuations in reactive current generated by a DC electric furnace or the like.

[0002]

2. Description of the Related Art FIG. 17 shows Mitsubishi Electric Technical Report VO1.62.
No. FIG. 8 is a circuit diagram showing a configuration of a conventional active filter device of this type disclosed in 1988, P15 to P20 and a connection with a power supply system to be controlled.

In FIG. 17, reference numeral 1 is a system power supply for supplying power to the load 2 to be compensated, 2 is a load to be compensated connected to the system power supply 1, and a harmonic source 3 for generating higher harmonics such as an inverter is used. It comprises a capacitive load 4 such as a phase capacitor. 5a is a load current I flowing into the load 2 to be compensated.
A current transformer 6 for detecting L is an active filter device which outputs the same compensation current Ic as the harmonic current component of the load current IL based on the output of the current transformer 5a.

The active filter device 6 is composed of the elements within the frame indicated by the alternate long and short dash line in FIG. In the above-mentioned frame of the figure, 5b is a current transformer for detecting the compensation current Ic, 7 is an inverter transformer for introducing the compensation current Ic from the power supply system including the system power supply 1 and the load 2 to be compensated, 8
Is composed of a plurality of inverter units, and a self-excited inverter for applying a voltage to the inverter transformer 7 to convert the DC voltage charged in the DC voltage source capacitor 9 into an AC voltage is a compensation current based on the load current IL. Standard Ic ^*
Compensation current detection circuit (details will be described later), 11 is an adder / subtractor for obtaining the difference ΔI between the compensation current reference Ic ^* and the output Ic ⁻ of the current transformer 5b, and 12 is the above ΔI.
And a current control circuit that calculates the voltage reference V ^* based on the output of the capacitor voltage control circuit 13, 13 is a capacitor voltage control circuit that controls the voltage of the DC voltage source capacitor 9,
Reference numeral 14 is a PWM (Pulse Width Modulation) control circuit that drives the self-excited inverter 8 based on the output of the current control circuit 12.

Further, the compensation current detection circuit 10 is shown in FIG.
It is composed of elements within a dotted line frame of 7. In the above frame of the figure, 10a is the angular velocity θ synchronized with the system power supply.
PLL circuit for detecting (frequency of fundamental wave), 10
b is a three-phase signal (iLa, i) detected by the current transformer 5a.
Lb, iLc) is a 3φ / 2φ conversion circuit for converting an AC component into a two-phase signal (id, iq) of a DC component based on the angular velocity θ, and 10c is a two-phase signal (id, output of the 3φ / 2φ conversion circuit 10b, filter circuit for extracting a specific signal from iq), 10d converts the filtered two-phase signal by the filter circuit 10c (id ', iq') to the three-phase signal based on the angular velocity theta, as a compensation current reference Ic ^* It is a 2φ / 3φ conversion circuit for outputting. The number (3) displayed on the signal line in the figure indicates that the signal line is a three-phase signal line.

Next, the operation will be described. The active filter device 6 is connected in parallel to the load 2 to be compensated, detects a fault current component such as a harmonic current contained in the load current IL, and supplies a compensation current Ic having a phase opposite to this to the active filter device 6. This acts to cancel the fault current component on the power supply side. When the load current IL is being supplied from the system power supply 1 to the load to be compensated 2, first, the compensation current detection circuit 10
Based on the current, that the compensation current to compensate for this reference Ic ^*
Is determined (details will be described later).

The difference ΔI between the compensation current reference Ic ^* and the component Ic ^{− of} the current Ic (compensation current) flowing into the inverter transformer 7 is obtained by the adder / subtractor 11, and the current control circuit 12
Output to. The current control circuit 12 calculates the voltage reference V ^* based on this ΔI and the output of the capacitor voltage control circuit 13. The PWM control circuit 14 compares the voltage reference V ^* with a triangular wave carrier signal for pulse width modulation (PWM) of the voltage reference V ^* and modulates the voltage reference V ^* to form an inverter unit that configures the self-excited inverter 8 so that ΔI becomes small. Drive and control its output voltage. Here, by modulating using the triangular wave carrier signal, the output waveform (average) of the inverter unit becomes a sine wave.

The self-excited inverter 8, which is the central part of the active filter device, is composed of a plurality of inverter units, and each unit is connected in series via an inverter transformer 7. Each inverter unit is controlled by the PWM control circuit 14 and generates a voltage necessary for flowing the compensation current Ic to the inverter transformer 7. In this way, the inverter 8 plays a role of converting the DC voltage charged in the DC voltage source capacitor 9 into an AC voltage, and serves as a voltage source for generating the AC voltage Ed.

The compensation current detection circuit 10 is a circuit for determining the compensation current from the load current IL, that is, a circuit for detecting the compensation current reference Ic ^* . Next, the operation will be described in detail. The PLL circuit 10a detects the angular velocity θ (fundamental wave frequency) synchronized with the system voltage. The 3φ / 2φ conversion circuit 10b supplies the load current IL detected by the current transformer 5a to the two-phase signal (id, id,
iq). id = (2/3) [iLa ・ sin θ + iLb ・ si
n (θ- (2/3) π) + iLc ・ sin (θ- (4/3) π)] iq = (2/3) [i
La ・ cos θ + iLb ・ cos (θ- (2/3) π) + iLc ・ cos (θ- (4 /
3) π)] d axis means the phase difference component from the reference θ,
The q-axis means the in-phase component with θ.

Here, the dq conversion is for obtaining the DC component of the angular velocity θ. That is, the above equation decomposes three-phase AC into each AC component, converts it into two-phase AC, and further calculates the angular velocity θ.
Based on, the stationary coordinates are converted into rotating coordinates. This will be described with reference to FIG. Three-phase alternating current i (iu, iv, iw) at the three-phase fixed coordinate uvw shown in FIG.
Is converted into a two-phase alternating current i (iα, iβ) at a two-phase fixed coordinate αβ shown in FIG. This two-phase fixed coordinate α
At β, the two-phase alternating current i is rotating. Therefore, by converting the two-phase fixed coordinate αβ into the two-phase rotating coordinate dq shown in FIG. 7C, the two-phase alternating current i can be made stationary at the two-phase coordinate dq. That is, id and iq are DC signals.

The outputs id, i of the 3φ / 2φ conversion circuit 10b
Of q, id corresponds to the phase difference with respect to the signal of the angular velocity θ. On the other hand, iq corresponds to the in-phase component. At this time, when θ which is the reference of the rotational coordinate conversion and the phase difference φ between the vectors (id, iq) are shown, it becomes as shown in FIG.

The filter 10c receives the two-phase signal (id,
iq) is a circuit for extracting a specific signal, and a high-pass filter (HPF) can be used to extract harmonic components other than the fundamental wave. And the filter 10
2φ / 3φ conversion circuit 10d based on the output of c and the angular velocity θ
Converts into a three-phase signal. ^{ica * = id · cos θ +} iq · sin θ icb * = id · cos (θ-2/3 · π) + iq · sin (θ-2/3 · π) icc * = id · cos (θ-4 / 3 ・ π) + iq ・ sin (θ-4 / 3 ・ π)

In this way, the compensation current detection circuit 10 outputs the compensation current reference ic ^* (the compensation amount corresponding to the harmonic component). Based on this compensation current reference ic ^* , the compensation current ic
Generate.

Next, a concrete waveform will be described as an example. FIG. 18 is an operation waveform when a rectifier load is assumed. The load current IL shown in FIG.
Detected by. The load current IL can be separated into the fundamental wave component IL (dashed line waveform in the figure) and the harmonic component (hatched portion in the figure), and the harmonic component has a waveform IH shown in FIG. 18B. In order to remove this harmonic component IH, the active filter device 6 detects the harmonic component IH by the compensation current detection circuit 10 (compensation current reference ic ^* ), and the phase opposite to that of the harmonic component IH in FIG. By operating the self-excited inverter 8 so that the current Ic flows from the power supply system, the current IH is canceled by the current Ic, and the sine wave of only the fundamental wave component is generated on the power supply side as shown in FIG. 18 (d). It becomes the current Is.

In the above description, harmonic compensation has been described as an example.
By setting the cut-off frequency of the filter 10c appropriately or changing the configuration of the filter circuit appropriately, the reactive power generator mainly compensating for the fluctuations of the reactive current (id) lead phase and lag phase ( SVG device).

[0016]

The conventional SVG device has the following problems.
Since it is configured as described above, S is applied to a random reactive current fluctuation generated by a load such as a DC electric furnace.
It is not possible to compensate the reactive current fluctuation by effectively utilizing the capacity of the VG device.

Further, in the case where the fluctuation of the reactive current becomes small and the delayed reactive current is constantly generated as in the DC electric furnace,
Power supply power factor deteriorates. Since the SVG device has a small fluctuation in the reactive current, it is in an operating state in which a compensation current is hardly output, and the phase advancing capacity of the SVG device cannot be effectively used.

Further, in the final stage of melting and refining of the DC electric furnace, if the fluctuation of the reactive current becomes small and the voltage flicker becomes small, the compensation current becomes small as the SVG device, and further, if the voltage flicker becomes less than the regulation value, the SVG becomes smaller. No equipment is needed. If the SVG device continues to operate in such a state, power is consumed by the operation loss of the SVG device.

Further, since the current of the DC electric furnace is controlled by the thyristor rectifier as in the DC electric furnace, the reactive current is the main cause of the voltage flicker in the power system in a device having a very small reverse phase current. This is a fluctuation and the fluctuation of the active current has little effect. In such a device, when the SVG device tries to compensate for the fluctuation of the active current, a fluctuation of the DC voltage occurs as an effect thereof, and the capacitor capacity must be increased in order to make the voltage fluctuation below the allowable value. There were problems such as not being.

The present invention has been made in order to solve the above problems, and in order to cope with a load such as a DC electric furnace in which various load fluctuations occur, the SVG device is advanced from the delayed phase to the advanced phase. The capacity of is effectively used to compensate the fluctuation of the load reactive current and contribute to the improvement of the voltage flicker. It also contributes to the improvement of the power supply power factor of the load, and when the voltage flicker is below the allowable value, SVG An object of the present invention is to obtain an SVG device that can reduce the capacitor capacity by temporarily stopping the operation of the device to contribute to power reduction and not compensating for the fluctuation of the active current.

[0021]

(1) A reactive power generator according to the present invention derives a compensation current reference according to a reactive current component of a load current supplied from a system power supply to a load,
In a reactive power generator that generates a compensation current based on this compensation current standard and sends it to the grid to adjust the reactive power of the grid, a variable variable bias that changes according to the fluctuation of the grid voltage at the load end. Bias reference and bias reference determination means using a combined value of a fixed Baice reference set to output a predetermined lagging reactive current as a bias reference,
And a correction means for correcting the compensation current reference with the bias reference.

(2) Further, a compensation current reference is derived according to the reactive current component of the load current supplied from the system power supply to the load, a compensation current is generated based on this compensation current reference, and is sent to the system. In the reactive power generator that adjusts the reactive power of the system, between a variable bias reference that changes the bias according to the fluctuation of the load reactive current and a fixed bais reference that is set to output a predetermined lagging reactive current. Bias reference determining means for using the combined value as a bias reference and correction means for correcting the compensation current reference with the bias reference are provided.

(3) Also, a compensation current reference is derived according to the reactive current component of the load current supplied from the system power supply to the load, a compensation current is generated based on this compensation current reference, and is sent to the system. In the reactive power generator that adjusts the reactive power of the system, a variable bias reference that changes the bias according to the fluctuation of the load reactive current, and a fixed Baice reference that is set to output a predetermined advanced reactive current. A bias reference determining unit that uses the combined value as a bias reference; and a correction unit that corrects the compensation current reference based on the bias reference, wherein the fluctuation of the load reactive current is less than or equal to a predetermined value, and
This makes it possible to deal with a delayed load .

(4) Also, it is supplied to the load from the system power supply.
Derivation of compensation current reference according to reactive current component of load current
Then, generate the compensation current based on this compensation current reference and
Serial sent to the grid, ineffective electric adjusting the reactive power of the system
In the force generator, depending on the fluctuation of the reactive current
Variable bias reference to change the bias and no advance
If a fixed Bais standard is set to output effective current,
Bias reference determining means using the formed value as a bias reference, and
Correction means for correcting the above compensation current reference by the bias reference
And a fluctuation of the load reactive current is less than or equal to a predetermined value, and provided with a detection means for detecting that it is a delayed load, when the operating state output from the detection means from another operating state,
The bias reference determining means is operated.

(5) Further, the variable bias reference of the bias reference determining means is a variable bias reference of the input signal to the reference determining bias means through a differential element and a first-order lag element.

[0026]

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 shows an SVG device of the present invention. The same functions as those of the conventional art are represented by the same numbers and the description thereof is omitted.

In the figure, 2 is a compensation target, which is composed of a DC electric furnace 3 and a harmonic filter 4 which also serves as a power factor improving capacitor. Reference numeral 15 represents the transmission line impedance (Xs) of the power system, 52SVG is an AC circuit breaker for the SVG device (hereinafter referred to as 52SVC), 52DC is an AC circuit breaker for the DC electric furnace (hereinafter referred to as 52DC), and 52F is a harmonic. Circuit breaker for wave filter (hereinafter referred to as 52F), 17
Is a limiter that limits the output signal of the filter 10c according to the open / closed state of 52DC, 18 is an on-delay circuit that detects the open state of 52DC, and 19 is a gain that determines the amount of compensation for fluctuations in the load reactive current.

Reference numeral 20 is a bias reference determining circuit for determining the bias reference, the details of which are shown in FIG. The compensation current Ic ^* is determined by subtracting the compensation amount for the load variation and the bias compensation amount obtained by converting the bias reference by 2φ / 3φ. Figure 2
21a is a filter for smoothing the load reactive current signal (ido) (this output serves as a variable bias reference),
Reference numeral 21b is a lagging reactive current reference, 21c is a switch for turning on and off 21b by 52F (this output signal serves as a fixed bias reference), 21d is a subtracter for subtracting a variable bias reference from the fixed bias reference, and 21e is the signal. Is a filter for smoothing, and this output serves as a bias reference.

The compensating current detecting circuit 10 of FIG. 1 detects the fluctuation of the load reactive current, but when 52DC is open, it is limited to zero signal by the limiter 17. Next, even if 52DC is input, the on-delay circuit 18 limits the zero signal to the zero signal by the limiter 17 for a certain period of time.
It is possible not to compensate for the inrush current at the time of making.

On the other hand, the bias reference determining circuit 20 shown in FIG.
Is the preset lagging reactive current reference 21b set to 5
Switch on and off with the switch 21c according to the open and closed state of 2F,
The switch 21 when the harmonic filter is turned on
c is closed, a fixed bias reference is created, a variable bias reference is created via the smoothing filter 21a for the load reactive current signal, the variable bias reference is added from the fixed bias reference by the adder / subtractor 21d, and the smoothing filter is added. The bias reference is calculated via 21e.

The above operation will be described with reference to FIG. When the load is not applied and only the harmonic filter 4 is applied to the system, the SVG device outputs a constant lagging reactive current based on a fixed bias reference, and after the load is applied, it continues for the on-delay time. By outputting a constant lagging reactive current according to a fixed bias reference and limiting the bias reference according to the amount of load reactive current after the on-delay time, it is possible to smoothly limit the lagging current output of the SVG device. .

The compensation signal determined from the fluctuation of the load reactive current is subtracted from the bias reference calculated as described above to determine the compensation current reference Ic ^*, which is sent to the power system to reduce the voltage rise.

In the above description, the load 3 is turned on after only the harmonic filter 4 is connected (turned on) to the system. However, load applying means for automatically turning on the load under these conditions. May be provided.

Embodiment 2. In the first embodiment described above, the bias reference is limited in accordance with the amount of the load reactive current to compensate the phase advancing capacity of the harmonic filter. However, as shown in FIG.
Reference numeral 22 is a flicker meter for measuring the voltage flicker of the power system, which detects and outputs the system voltage fluctuation signal 22a1 (ΔV) and the voltage flicker value (ΔV10), which is different from the system voltage fluctuation signal (ΔV) 22a1. The bias standard is determined by

Here, ΔV and ΔV10 are the following (Equation 1)
It is represented by.

[0037]

[Equation 1]

However, V0: reference voltage T: period v: measurement point voltage an: flicker luminosity coefficient ΔVn for fluctuation frequency fn: fluctuation of voltage fluctuation component of fluctuation frequency fn obtained as a result of frequency analysis of voltage fluctuation

The details of the bias reference determining circuit 20 are shown in FIG. For the fluctuation signal 22a1 of the system voltage, a circuit for calculating a variable bias reference is provided by a limiter 23c and a first-order lag element 23b consisting of an incomplete differential element 23a, a proportional gain Kb and a time constant Tb, and a direct current is supplied by the incomplete differential element 23a. The proportional gain K of the first-order lag element 23b
By appropriately setting b, the time constant Tb, and the limiter 23c, the magnitude of the fluctuation of the fluctuation signal of the system voltage can be calculated.

By constructing the bias reference determination circuit 20 by combining the variable bias reference Δid0 and the fixed bias reference 21b, the bias reference is adjusted according to the magnitude of the fluctuation of the system voltage, so that the lagging capacitance of the SVG device is adjusted. Can be used effectively.

The above operation will be described with reference to FIGS. FIG. 6 is an equivalent circuit of a DC electric furnace, and the arc resistance is represented by a variable resistance R. FIG. 7A shows a waveform of the load reactive current with respect to a sudden change in the arc resistance R that occurs randomly. Normally, since the constant current control is performed by the thyristor rectifier, the load reactive current is constant, but the arc resistance R is constant.
Due to the sudden change in the load reactive current, the load reactive current increases rapidly and is limited to a constant value by the response of the thyristor rectifier. This fluctuation of the load reactive current causes voltage flicker in the power system. This phenomenon is often seen in the main melting stage of a DC furnace.

FIG. 7 (b) shows a waveform in which the fluctuation signal (ΔV) of the system voltage detected by the flicker meter changes according to the fluctuation of the load reactive current in FIG. 7 (a). Figure 7 (c)
Is S when the lagging reactive current reference 21b in FIG. 5 is zero.
FIG. 7D shows the VG device output, and the lagging reactive current reference 2 is shown in FIG.
It shows the case where 1b is slightly inserted, and S larger than that in FIG.
The VG device output can be obtained. However, although the lagging reactive current reference 21b can be set up to the device rating,
In this case, the lagging reactive current is always output, and the power source power factor of the DC furnace deteriorates, which is not preferable.

FIG. 7 (e) shows the operation of the present invention. Since the bias reference is determined according to the magnitude of the voltage fluctuation, the lagging capacitance of the SVG device is effectively used to reduce the reactive current of the load. Fluctuations are compensated on the power supply side to reduce voltage flicker.

Embodiment 3. In the second embodiment, the case where the variable bias reference is calculated according to the amount of voltage fluctuation (ΔV) has been described.
As shown in FIG. 8, the load reactive current signal (ido) 22a2
On the other hand, the circuit configuration is such that the variable bias reference is determined. The details of the bias reference determination circuit 20 are shown in FIG. 9, which corresponds to FIG. 5 of the second embodiment, and the explanation of the operation FIG. 10 corresponds to FIG. 7 of the second embodiment. Since it is the same as that described in the second embodiment, the description thereof will be omitted. In the present invention, since the voltage fluctuation (ΔV) which is the detection value of the flicker meter is not used, the flicker meter can be omitted and an inexpensive device can be obtained.

Fourth Embodiment In the third embodiment described above, when the load reactive current fluctuation in the DC furnace main melting period is large, the bias reference is determined by combining the lagging reactive current reference and the variable bias reference. During the refining period, the fluctuation of the load reactive current is small and the load becomes a constant amount of delay load. Therefore, as shown in FIG. 11, a fixed bias reference composed of the advanced reactive current reference 23d and a variable bias reference corresponding to the fluctuation of the load reactive current are used. The bias reference is determined by combining them, and the operation is shown in FIG. When the fluctuation of the load reactive current is small and the load is delayed, the phase reactive reactive current is generated to contribute to the improvement of the power source power factor with respect to the load of the DC furnace.

In this embodiment, when the fluctuation of the load reactive current is small and the load is delayed, a detecting means for detecting this state is provided and the bias reference determining circuit is turned on / off according to the output of the detecting means. It may be turned off. Further, any one of the bias reference determining circuits according to the first to third embodiments and the bias reference determining circuit according to the fourth embodiment may be provided and the both circuits may be switched by the detecting means.

Embodiment 5. In the second embodiment, the case where the bias reference is determined in accordance with the fluctuation signal of the system voltage which is the detection signal of the flicker meter has been described. However, as shown in FIG. 13, the voltage flicker of the detection signal of the flicker meter is shown. A drive / stop circuit 24 for determining the drive / stop of the SVG device corresponding to the value 22b is provided, and the drive / stop signal 24 as the determination result is provided.
d is output to the PWM control circuit 14, and when the voltage flicker is small, the operation of the SVG device is temporarily stopped, and when the voltage flicker becomes large, the operation is restarted.

The details of the operation / stop determination circuit 24 will be described with reference to FIG. In FIG. 14, reference numeral 24a1 is a comparator for judging the operation with respect to the voltage flicker value 22b.
4a2 is a comparator for determining stop, and 24b1
Is a delay circuit for the operation command which is the determination result of the comparator 24a1, and 24b2 is a comparator 24a.
The delay circuit 24c responds to the stop command, which is the determination result of a2.
It is a latch circuit that sets and resets the stop signal 24d.

Further, in the above embodiment, the SVG device is operated / stopped with respect to the voltage flicker value 22b. However, fluctuations in the system voltage (ΔV) or load reactive current (i).
The same effect can be obtained even with a configuration in which the operation / stop of the SVG device is determined with respect to the variation amount of (do).

Further, the voltage flicker value 22b, the fluctuation of the system voltage (ΔV) and the fluctuation of the load reactive current (ido) are three.
A circuit for determining the operation / stop of the SVG device is provided according to the size of each of the three, and configured by combining these three types of circuits. If any one of the above three inputs exceeds a predetermined value, the SVG device is activated. You may make it stop. Also,
Two types of circuits may be adopted among the three types of circuits.

Sixth Embodiment Generally, the voltage drop at the power receiving point can be expressed by the following equation. ΔV = r ・ PL + x ・ QL Where ΔV: voltage fluctuation value at power receiving point r: Resistance of power source impedance x: reactance of power source impedance PL: active power of load QL: Reactive power of load

In the above equation, the advance reactive power Q in the SVG device
The voltage fluctuation at the power receiving point when compensated by c should satisfy the following formula in order to make ΔV = r · PL + x · (QL−Qc) ΔV = 0. Qc = QL + (r / x) · Since PL is normally x >> r, Qc = QL Therefore, the compensation current generated by the SVG device is (Equation 2).

[0053]

[Equation 2]

Here, −: direct current component on the (d, q) axis to :: alternating current component on the (d, q) axis The direct current component on the (d, q) axis means a positive phase component, and an alternating current component. The minute means a reverse phase component and a harmonic component. Further, the main factors of the voltage flicker are a positive phase component, a negative phase component and a harmonic component of the reactive power.

The DC electric furnace is a device in which electric power is converted by a thyristor rectifier, and the electric furnace current is controlled to be a constant current by the thyristor rectifier. Sudden changes in the electrical resistance of the melted material (hereinafter referred to as arc resistance) occur randomly, and the thyristor rectifier operates so as to limit the sudden change in current due to this sudden change in arc resistance to a constant current in response to control. At this time, transient fluctuations of active current and reactive current occur. However, since the power is converted by the thyristor rectifier, almost no negative phase component is generated. Moreover, the generated harmonic current depends on the number of phases of the thyristor rectifier, and is usually SV.
It is a higher harmonic that cannot be compensated for by the G device. Therefore, in order to compensate the voltage flicker of the DC electric furnace, the SVG
The compensation current generated by the device is (Equation 3).

[0056]

[Equation 3]

Here, −: direct current component on the (d, q) axis to: means that the alternating current component on the (d, q) axis, that is, the active current does not need to be compensated.

Next, the instantaneous power and the capacity of the DC power supply capacitor 9 which is the DC power supply of the SVG device will be described. In the electric circuit (FIG. 16) in which a single-phase sinusoidal waveform AC voltage and AC current flow, the instantaneous power p at the current phase angle φ is given by the following equation. p = Vsin (ωt) · Isin (ωt + φ) p = VI / 2 (cos (φ) −cos (2ωt−φ)) When φ = 0, there is only active power. When φ = π / 2, there is only reactive power.

The first term is the average power converted between the power system and the capacitor voltage, which is the DC voltage source of the SVG device, and the second term is the pulsating power oscillating at twice the frequency around the average power. Is. This pulsating component appears in the capacitor voltage.

Considering a three-phase balanced AC circuit, the second term does not appear. Only the average power of the first term appears as the fluctuation of the capacitor voltage. That is, when there is a transient power exchange between the power system and the SVG device, the capacitor voltage fluctuates. The capacitor capacity of the DC power supply capacitor 9 of the SVG device is selected so that transient power interchange is assumed and the capacitor voltage fluctuation is limited to an allowable value or less.
The voltage flicker compensating SVG device of the DC electric furnace can reduce the capacitor capacity by compensating only the reactive current and not the active current as described above.

FIG. 15 shows an embodiment of a circuit that does not compensate the active current. 2φ / 3φ in FIG.
The input side q-axis component of the conversion 10d is set to zero, and the control is performed only by the d-axis component.

Embodiment 7. In the above-described first to sixth embodiments, these embodiments may be combined and configured, and respective features may be added. In this case, there are two embodiments, or
You may combine more than embodiment. Further, the respective embodiments of the combination of these may be selectively switched. Further, this selective switching may be performed manually or automatically under a predetermined condition.

[0063]

According to the first aspect of the present invention, the combined value of the variable bias reference for varying the bias according to the fluctuation of the system voltage and the fixed bais reference set to output a predetermined lagging reactive current. Is used as the bias reference, the lag capacity of the reactive power generation device can be effectively used when the fluctuation amount of the system voltage is large, and there is an effect that it greatly contributes to the voltage flicker of the power system.

(2) According to claim 2, a variable bias reference for varying the bias according to the fluctuation of the load reactive current,
Since the bias value is a combined value with a fixed Baice reference set to output a predetermined lagging reactive current, the lagging capacity of the reactive power generator can be effectively used when the amount of variation in the load reactive current is large. It has an effect of greatly contributing to the voltage flicker of the power system.

(3) According to claim 3, a variable bias reference for varying the bias according to the fluctuation of the load reactive current,
Since the bias reference value is the combined value with the fixed Baice reference, which is set to output the specified phase-adverse reactive current, when the fluctuation of the load reactive current is small, the bias reference for the phase advance is used to generate the force of the power supply against the load. There is an effect that contributes to the rate improvement.

(4) According to claim 4, since the detecting means is provided for detecting that the fluctuation of the load reactive current is not more than a predetermined value and that it is a delayed load, automatic detection is performed according to the output of this detecting means. The effect is that the bias standard is determined.

(5) According to the fifth aspect, since the input signal to the bias reference determining means is used as the variable bias reference through the differential element and the first-order lag element, the variable bias reference can be easily generated.

[0068]

[Brief description of drawings]

FIG. 1 is a configuration diagram of a reactive power generator according to a first embodiment of the present invention.

FIG. 2 shows a configuration diagram of a bias reference determination circuit according to the first embodiment of the present invention.

FIG. 3 shows an operation explanatory diagram of the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a reactive power generator according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a bias reference determining circuit according to a second embodiment of the present invention.

FIG. 6 shows an equivalent circuit diagram of a DC electric furnace according to a second embodiment of the present invention.

FIG. 7 shows an operation explanatory diagram of the second embodiment of the present invention.

FIG. 8 is a configuration diagram of a reactive power generator according to a third embodiment of the present invention.

FIG. 9 shows a configuration diagram of a bias reference determination circuit according to a third embodiment of the present invention.

FIG. 10 shows an operation explanatory diagram of the third embodiment of the present invention.

FIG. 11 shows a configuration diagram of a bias reference determination circuit according to a fourth embodiment of the present invention.

FIG. 12 shows an operation explanatory diagram of the fourth embodiment of the present invention.

FIG. 13 shows a configuration diagram of a reactive power generator according to a fifth embodiment of the present invention.

FIG. 14 is a configuration diagram of a drive / stop determination circuit according to a fifth embodiment of the present invention.

FIG. 15 shows a configuration diagram of a reactive power generation device according to a sixth embodiment of the present invention.

FIG. 16 shows an auxiliary explanatory diagram for explaining the sixth embodiment of the present invention.

FIG. 17 shows a configuration diagram of a conventional active filter device.

FIG. 18 shows an operation waveform diagram of a conventional active filter device.

FIG. 19 is a diagram for explaining the operating principle of a conventional active filter device.

FIG. 20 is a diagram for explaining the operating principle of a conventional active filter device.

[Explanation of symbols]

1 system power source, 2 load, 3 harmonic source, 4 capacitive load, 5a, 5b current transformer, 6 active filter device, 7 inverter transformer, 8 self-excited inverter,
9 DC power supply capacitor, 10 Compensation current detection circuit,
10a PLL circuit, 10b 3 phase / 2 phase (3φ / 2
φ) conversion circuit, 10c filter, 11 adder / subtractor, 1
7 limiter, 18 on-delay circuit, 19 gain, 20 bias reference determining circuit, 21a filter,
21b Delayed reactive current reference, 21c switch, 21d
Adder / subtractor, 21e filter, 22 flicker meter, 22a1 system voltage fluctuation amount (ΔV), 22a2
Load reactive current, 22b Voltage flicker (ΔV10), 2
3a Incomplete differential element, 23b First-order lag element, 23c
Limiter, 23d advanced reactive power standard, 24 operation
Stop determination circuit, 24a1, 24a2 comparator, 2
4b1, 24b2 delay circuit, 24c latch circuit, 24d operation / stop signal, 52SVG AC breaker for SVG device, 52DC AC breaker for DC electric furnace, 5
Circuit breaker for 2F high frequency filter.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G05F 1/70 H02J 3/18

Claims (5)

(57) [Claims] 1. A compensating current reference is derived according to a reactive current component of a load current supplied from a system power supply to a load, a compensating current is generated based on the compensating current reference, and the compensating current is sent to the system. In the reactive power generator that adjusts the reactive power of, the variable bias reference that changes the bias according to the fluctuation of the system voltage at the load end, and the fixed bias reference that is set to output a predetermined lagging reactive current. A reactive power generation device comprising: a bias reference determination unit that uses a combined value as a bias reference; and a correction unit that corrects the compensation current reference with the bias reference. 2. A compensating current reference is derived according to a reactive current component of a load current supplied from a system power supply to a load, a compensating current is generated based on this compensating current reference, and the compensating current is sent to the system. In the reactive power generator that adjusts the reactive power of, the combined value of the variable bias reference that changes the bias according to the variation of the load reactive current and the fixed Baice reference that is set to output the predetermined lagging reactive current. A reactive power generation device comprising: a bias reference determining unit that uses a bias reference; and a correction unit that corrects the compensation current reference using the bias reference. 3. A compensating current reference is derived according to a reactive current component of a load current supplied from a system power supply to a load, a compensating current is generated based on the compensating current reference, and the compensating current is sent to the system. In the reactive power generator that adjusts the reactive power of, the combined value of the variable bias reference that changes the bias according to the fluctuation of the load reactive current and the fixed Baice reference that is set to output a predetermined advance reactive current Bias reference determining means as a bias reference and correction means for correcting the compensation current reference with the bias reference are provided, and it is possible to cope with the case where the fluctuation of the load reactive current is a predetermined value or less and the delay load is present. A reactive power generation device characterized by the above. 4. A compensating current reference is derived according to a reactive current component of a load current supplied from a system power supply to a load, a compensating current is generated based on this compensating current reference, and the compensating current is sent to the system. In the reactive power generator that adjusts the reactive power of, the combined value of the variable bias reference that changes the bias according to the fluctuation of the load reactive current and the fixed Baice reference that is set to output a predetermined advanced reactive current. Bias reference determining means as a bias reference, correction means for correcting the compensation current reference with the bias reference, and detection means for detecting that the fluctuation of the load reactive current is a predetermined value or less and is a delayed load. Is provided, and the bias reference determining means is operated when the operating state outputted by the detecting means is changed from another operating state. Location. 5. The variable bias reference of the bias reference determining means according to claim 2, wherein an input signal to the bias reference determining means is a variable bias reference through a differential element and a first-order lag element. A reactive power generation device characterized by the above.