JP4523950B2 - Reactive power compensation device, reactive power compensation system, and reactive power compensation method - Google Patents

Description

  The present invention relates to a reactive power compensation device, a reactive power compensation system, and a reactive power compensation method that suppress load fluctuations that occur on a consumer side on a power supply side.

In an arc furnace that melts metal, a positive phase active current that is used electric power, a positive phase reactive current that causes voltage fluctuation, or a negative phase current that causes voltage imbalance frequently fluctuates. For this reason, voltage flicker occurs in the arc furnace bus of the arc furnace customer. This voltage flicker is transmitted while being attenuated from the arc furnace bus to the general consumer bus via the arc furnace transformer, the upper bus on the electric power company side, and the general consumer transformer. In order to reduce the voltage flicker of the general consumer bus, it is necessary to suppress the voltage flicker of the arc furnace bus that is the generation source.
For example, Patent Literature 1 includes a bus connected to a power source via a reactance, a load connected to the bus via a transformer, a plurality of filters connected to the bus, and a reactor connected to the bus. A technology is disclosed in which a thyristor is provided, and the phase of the thyristor is controlled using the voltage of the bus and the current flowing through the load to suppress reactive power fluctuations in the arc furnace. A direct current component is extracted using a band reject filter (BRF).
In addition, since each of the plurality of filters connected in parallel to the arc furnace bus line constitutes a series resonance circuit, the arc furnace current includes, for example, a secondary filter current, a tertiary filter current, a fourth filter current, and a fifth filter. Current is included. When the reactive power compensator detects the arc furnace current including these filter currents and performs control so as to cancel the reactive power fluctuation, positive feedback to these resonant circuits occurs due to the control delay, and these high There is a problem that the secondary current further increases. In order to avoid this, the reactive power compensator has been controlled to detect only the arc furnace current that does not include the filter current and cancel the fluctuations in the positive-phase reactive current and the negative-phase current. .
JP-A-7-67321 (FIG. 1, paragraph number 0011)

Due to contract or facility restrictions, there has been a demand to install a reactive power compensator on the power supply side (electric power company side) via a reactance (transmission line) instead of the conventional consumer side. Since the arc furnace current that is input to the reactive power compensator includes a plurality of filter currents connected in parallel, there is a problem that higher-order current increases due to positive feedback.
The filter frequency setting value on the customer side is a fixed value, but the resonance point (control unstable point) seen from the reactive power compensator installed on the power source side is low due to the influence of the power system configuration on the power source side or the customer side. appear. Since the power system configuration constantly changes, there is a problem that the resonance point (control unstable point) seen from the reactive power compensator installed on the power supply side changes. Note that the technique of Patent Document 1 has few problems because voltage flicker is detected on the bus side (on the consumer side) and reactive power fluctuations are suppressed.

  Then, this invention makes it a subject to provide the reactive power compensation apparatus, the reactive power compensation system, and the reactive power compensation method which can suppress the electric power fluctuation which generate | occur | produces on the consumer side at the electric power supply side.

  In order to solve the above problem, a reactive power compensation system according to the present invention includes a host system, a power transmission line having an impedance, and a customer who is transmitted from the host system via the power transmission line. The reactive power compensation system includes a reactive power compensation device that reduces a negative phase current component from a load current flowing in the transmission line measured on the higher system side of the transmission line. A positive phase current extracting means, a negative phase current extracting means for extracting a negative phase current component from the load current, a connection point voltage measured on the upper system side of the transmission line and a frequency of the load admittance from the load current A frequency characteristic for specifying a specific frequency from the amplitude phase calculation means for calculating the characteristic and the amplitude characteristic and phase characteristic of the load admittance calculated by the amplitude phase calculation means. Means, a first filter for removing the frequency component of the singular frequency from the output signal of the positive phase current extracting means, and a second filter for removing the frequency component of the singular frequency from the output signal of the negative phase current extracting means; And a power converter for adding a compensation current composed of a positive phase current for canceling the output signal of the first filter and a negative phase current for canceling the output signal of the second filter to the load current. .

  According to this, a normal phase current and a negative phase current flowing in the load current are extracted, and a specific frequency component is removed from each extracted current. Then, a positive phase current and a negative phase current are generated so as to cancel the removed current, and the generated current is added to the load current as a compensation current. Also, the singular frequency of the positive phase amplitude of the load admittance calculated by the interconnection point voltage and the load current is specified, and the frequency component of this singular frequency is removed from the positive phase current and the negative phase current extracted from the load current. The

  According to the present invention, power fluctuations that occur on the consumer side can be suppressed on the power supply side.

(First embodiment)
A configuration of a reactive power compensation system according to an embodiment of the present invention will be described.
In FIG. 1, a reactive power compensation system 200 includes a reactive power compensator 100 connected to a host system 110 via a transmission line 130 and a transformer Tr3 for an arc furnace customer, a transmission line 135 and a transformer for a general consumer. A general customer 120 connected to the host system 110 via Tr2A, Tr2B, Tr2C, and an arc furnace customer 150 connected to a transformer Tr3 for an arc furnace customer via a power transmission line 137 are provided.

The electric arc furnace customer 150 receives electric power from the electric arc furnace 152, the BPF 155 in which a plurality of LC series resonance circuits having resonance frequencies f 2, f 3, f 4, and f 5 are connected in parallel, and the electric power transmission line 137. And a transformer Tr4 to be supplied.
The arc furnace 152 is a furnace in which a three-phase voltage is applied to a metal waste such as iron to cause an arc current to flow between the phases to be melted, and the instantaneous current of the arc sequentially varies depending on the melting state. In addition, an unbalanced current flows through the arc furnace 152 due to variations in instantaneous current between phases, and the current amplitude and phase fluctuate irregularly and irregularly due to the inductance component of the metal waste. Voltage fluctuations occur in the arc furnace customer 150 due to current fluctuation components over a wide frequency range centered on the interconnection point frequency generated by the arc furnace operation. This voltage fluctuation is transmitted to the arc furnace bus of the reactive power compensation system 200 via the transformer Tr4 and the reactance L3 of the power transmission line 137, and further to the upper bus via the transformer Tr3, and part of the power transmission line. The variable current is shunted to the upper system 110 via the reactance L1 of 130, and the rest is transmitted to the general customer bus via the transformers Tr2A, Tr2B, Tr2C, and further to the general customer 120 via the reactance L2 of the power transmission line 135. Also affects.

  The BPF 155 has a resonance frequency of integer multiples f2, f3, f4, f5 (120 Hz, 180 Hz, 240 Hz, 300 Hz) of the commercial frequency f0 (60 Hz), and bypasses the voltage noise of the harmonic frequency generated in the arc furnace 152. Yes.

The host system 110 is typically a power generation facility or a substation facility. The power transmission line 130 is often a long-distance power transmission line, and there may be a plurality of routes or two lines. Switching of the upper system 110 and the transmission line 130 is performed several times a day due to restrictions such as transmission line capacity, power generation equipment capacity, substation equipment capacity, or equipment inspection. At this time, the reactance L1 of the power transmission line 130 changes.

Reactive power compensator 100 receives as inputs the interconnection point voltage Vs detected by the potential transformer PT, the arc furnace current I _L flowing through the transmission line 137 detected by the current transformer 50 to the arc furnace customer 150 Then, fluctuation components of the normal phase reactive current and the negative phase current are extracted, and a compensation current Ic for canceling these components is generated and injected into the arc furnace bus. In other words, interconnection current Is flowing in the arc furnace busbar becomes Is = Ic + _{I L.}

Here, the three-phase unbalanced power will be described. In the arc furnace load, the three-phase power source includes a plurality of frequency components. Here, the frequency component f will be described.
When the three-phase voltages Vu (f), Vv (f), Vw (f) and the three-phase currents Iu (f), Iv (f), Iw (f) are used, the three-phase power P (f) for the frequency component f Is
P (f) = Vu (f) · Iu (f) + Vv (f) · Iv (f) + Vw (f) · Iw (f)
= 3V0 (f) · I0 (f) + 3V1 (f) · I1 (f) + 3V2 (f) · I2 (f)
And is the sum of zero-phase power, positive-phase power, and negative-phase power.
In addition,
Zero-phase current I0 (f) = (1/3) (Iu (f) + Iv (f) + Iw (f)),
Positive phase current I1 (f) = (1/3) (Iu (f) + a · Iv (f) + a 2 · Iw (f)),
Reverse phase current I2 (f) = (1/3) (Iu (f) + a ² · Iv (f) + a · Iw (f))
And a is a vector operator.

  Further, the load currents Iu (f), Iv (f), and Iw (f) for the frequency component f are decomposed into a balanced current and an unbalanced current, and the unbalanced current is caused by the reverse phase current I2 (f). Occur. Here, the ratio I2 (f) / I1 (f) between the negative phase current I2 (f) and the positive phase current I1 (f) is the unbalance rate k (f). In particular, when the three-phase AC balanced current I (f), I0 (f) = 0, I1 (f) = I, I2 (f) = 0, and only the positive phase current is obtained.

The positive phase current is decomposed into a positive phase active current and a positive phase reactive current. Therefore, in order to reduce the reactive power and the unbalanced power, the reactive power compensator 100 injects the compensation current Ic for canceling the positive phase reactive current and the negative phase current into the power system.

  In FIG. 2, the reactive power compensator 100 is also called a STATCOM (STATic synchronous compensator) or a self-excited SVC (Static Var Compensator). ), Transformer 10, power converter 20, capacitor 30, current control means 40, amplitude phase calculation means 60, amplitude phase calculation means 65, frequency identification means 70, and positive phase current extraction means. 80, reverse-phase current extraction means 85, BEF (Band Elimination Filter) 90, 95, and a current transformer (CT) 55, and supply reactive power to the arc furnace bus to generate the interconnection voltage Vs. Stabilize. The current control means 40, the amplitude phase calculation means 60, the amplitude phase calculation means 65, the frequency identification means 70, the positive phase current extraction means 80, the negative phase current extraction means 85, and the BEFs 90 and 95 are a CPU, ROM, It functions by a computer and program using RAM or the like.

  The transformer 10, the power converter 20, and the capacitor 30 process the DC voltage of the capacitor 30 by controlling the switch timing of the power converter 20, and output it as an AC voltage. Adjust. The power converter 20 is a self-excited converter and can be operated regardless of the distortion of the AC voltage on the system side, so that there are few restrictions on the compensation power supply capability. Further, the self-excited SVC does not require a phase advance capacitor, and therefore has an advantage that the installation space is small as compared with the separately excited SVC. The power converter 20 is configured using a semiconductor control element such as an IGBT (Insulated Gate Bipolar Transistor), but a GTO (Gate Turn-Off thyristor), an IEGT (Injection Enhanced Gate Transistor), or the like can also be used. .

  The current control means 40 controls the switch timing of the power converter 20 based on the normal phase reactive current component and the negative phase current component of the arc furnace current IL.

The positive phase current extraction means 80 extracts a positive phase reactive current from the arc furnace current IL. Specifically, the positive phase reactive current is calculated by multiplying sin θ by using the phase characteristic value θ at the interconnection point frequency calculated by the amplitude phase calculation means 60 from the arc furnace current IL. The BEF 90 removes the set frequency component from the positive phase reactive current signal output by the positive phase current extraction means 80. The negative phase current extraction unit 85 extracts the negative phase current from the system current Is. For example, the reverse phase current I2 is I2 = (1/3) (Iu + a ² · Iv + a · Iw)
Calculate using. The BEF 95 removes one or a plurality of frequency components set from the negative phase current signal output by the negative phase current extraction unit 85.

Amplitude phase calculating means 60 calculates a Bode diagram of a load admittance using interconnection point voltage Vs and the arc furnace current I _L. That is, frequency analysis is performed for each of the arc furnace current _IL and the interconnection point voltage Vs to obtain an n-order (first order = 1/10 s = 0.1 Hz if the measurement window is 10 s), and the arc furnace current n The n-th order component load admittance Yarc (n) is calculated by dividing the next component by the n-th component of the interconnection point voltage, and the frequency characteristics of the amplitude and phase of this load admittance Yarc (n) are calculated.

  Specifically, in the configuration diagrams of FIGS. 3 and 4, the amplitude / phase calculation means 60 includes αβ conversion means 310 and 315, waveform memories 312, 313, 317 and 318, FFT 320, 322, 324 and 326, Normal phase calculation means 330, 335, reverse phase calculation means 370, 375, amplitude phase separation means 340, 345, 380, 385, dividers 350, 355, and adders 360, 365 are provided.

The αβ conversion means 310 outputs an α-phase voltage Vsa and a β-phase voltage Vsb using the three-phase interconnection point voltage Vs (Vsu, Vsv, Vsw) based on the equations (1) and (2). .
Vsa = Vsu · 2 / 3−Vsv / 3−Vsw / 3 (1)
Vsb = Vsu / √3−Vsw / √3 (2)

αβ conversion unit 315 outputs the a-phase current Iarca and b current Iarcb using a three-phase arc furnace current _{I L (Iarcu, Iarcv, Iarcw} ) based on the equation (3) (4).
Iarca = Iarcu 2 / 3-Iarcv / 3-Iarcw / 3 (3)
Iarcb = Iarcu / √3−Iarcw / √3 (4)

  The waveform memories 312, 313, 317, and 318 store an α-phase voltage Vsa, a β-phase voltage Vsb, a current a-phase current Iarca, and a b current Iarcb for 10 seconds, respectively.

  The FFT converters 320, 322, 324, and 326 perform fast Fourier transform on the α-phase voltage Vsa, β-phase voltage Vsb, α-phase current Iarca, and β-phase current Iarcb, respectively, and sine wave components Vsas, Vsbs, and Iarcas, respectively. , Iarcbs and cosine wave components Vsac, Vsbc, Iarcac, Iarcbc. If the detection resolution is assumed to be 0.1 Hz, the sampling period necessary for the determination is T = 1 / 0.1 Hz = 10 seconds.

A general expression of the n-th order FFT of the function f (t) can be expressed by the following expressions (5) and (6).

The positive phase calculation means 330 converts the connection point voltages Vsas (n), Vsbs (n), Vsac (n), and Vsbc (n) that have been subjected to FFT conversion into positive phase voltages Vsd (positive) (n), Vsq (positive). ) (N).
The positive phase calculation means 335 calculates the FFT-transformed arc furnace currents Iarcas (n), Iarcbs (n), Iarcac (n), Iarcbc (n) and the positive phase currents Iarcd (positive) (n), Iarcq (positive). (N).

The amplitude phase separation means 340 separates the positive phase voltages Vsd (positive) (n) and Vsq (positive) (n) into the positive phase amplitude and the positive phase, and is calculated by the following equation.
Vs positive phase amplitude (n) = √ {Vsd (positive) (n) ² + Vsq (positive) (n) ² }
Vs positive phase (n) = tan ⁻¹ {Vsd (positive) (n) / Vsq (positive) (n)}

The amplitude phase separation means 345 separates the positive phase currents Iarcd (positive) and Iarcq (positive) into the positive phase amplitude and the positive phase, and is calculated by the following equation.
Iarc positive phase amplitude (n) = √ {Iarcd (positive) (n) ² + Iarcq (positive) (n) ² }
Iarc positive phase (n) = tan ⁻¹ {Iarcd (positive) (n) / Iarcq (positive) (n)}

  The divider 350 calculates the positive phase amplitude (n) of the load admittance Yarc (n) by dividing the Iarc positive phase amplitude (n) by the Vs positive phase amplitude (n). The adder 360 calculates the load admittance Yarc positive phase (n) by subtracting the Vs positive phase (n) from the Iarc positive phase (n).

  The negative phase calculating means 370 converts the FFT-connected interconnection point voltages Vsas (n), Vsbs (n), Vsac (n), Vsbc (n) into the positive phase voltage Vsd (reverse) (n) obtained by dq vector conversion. ), Vsq (reverse) (n). Further, the normal phase calculation means 375 converts the FFT-converted arc furnace currents Iarcas (n), Iarcbs (n), Iarcac (n), and Iarcbc (n) into the dq vector-converted positive phase current Iarcd (reverse) ( n), Iarcq (reverse) (n).

The amplitude / phase separation means 380 separates the dq vector-converted negative phase voltages Vsd (reverse) (n) and Vsq (reverse) (n) into the negative phase amplitude and the negative phase, and is calculated by the following equation: Is done.
Vs reverse phase amplitude (n) = √ {Vsd (reverse) (n) ² + Vsq (reverse) (n) ² }
Vs negative phase (n) = tan ⁻¹ {Vsd (reverse) (n) / Vsq (reverse) (n)}

The amplitude phase separation means 385 separates the dq vector-converted negative phase currents Iarcd (reverse) (n) and Iarcq (reverse) (n) into the negative phase amplitude and the negative phase phase. Is done.
Iarc negative phase amplitude (n) = √ {Iarcd (reverse) (n) ² + Iarcq (reverse) (n) ² }
Iarc reversed phase (n) = tan ⁻¹ {Iarcd (reverse) (n) / Iarcq (reverse) (n)}

  The divider 355 calculates the load admittance Yarc negative phase amplitude (n) by dividing the Iarc negative phase amplitude (n) by the Vs negative phase amplitude (n). The adder 365 calculates the negative phase phase (n) of the load admittance Yarc by subtracting the Vs negative phase phase (n) from the Iarc negative phase phase (n).

Here, with reference to FIG. 5, it supplements about the load admittance Yarc of an electric power grid | system.
FIG. 5A is an equivalent circuit of the reactive power compensation system 200, and FIG. 5B is a Thevenin equivalent circuit of this equivalent circuit.
In FIG. 5 (a), the reactive power compensator 100, the host system 110, and the AC source 152 of the separately excited reactive power compensator that may be connected in parallel to the arc furnace have equivalent inductances Z1 and Z2, respectively. , Z3 are connected, and the connection point of these inductances Z1, Z2, Z3 is a node A. A BPF 155 is connected to the arc furnace 152.

Here, the potential V _A of the node A is calculated using the superposition theorem.
V _A = (Z2 // Z3 ′) / {(Z2 // Z3 ′) + Z1} · V1 + (Z1 // Z3 ′) / {(Z1 // Z3 ′) + Z2} · V2 + (Z1 // Z2) / {(Z1 // Z2) + Z3 ′} · V3
Here, where a and b are integers, (Za // Zb) = Za · Zb / (Za + Zb), and Z3 ′ is a combined impedance of Z3, the equivalent resistance of the arc furnace, and BPF155.

In the Thevenin equivalent circuit of FIG. 5B, this potential _VA is described as the Thevenin power source Vs. The Thevenin resistance at the point A obtained by grounding the AC sources V1, V2, V3 is a parallel circuit of the impedances Z1, Z2, Z3 ′ (FIG. 5A). In this embodiment, by measuring the arc furnace current I _L is the load current potential of the point A and the interconnection point voltage Vs, which calculates the admittance Y of the arc furnace 152. Note that, as will be described later, the device admittance of the reactive power compensator 100 is also calculated using the interconnection point voltage Vs and the compensation current Ic.

The frequency specifying unit 70 specifies one or a plurality of singular frequencies from the amplitude and phase of the admittance Y calculated by the amplitude / phase calculating unit 60.
6 (a) is a frequency characteristic of the positive-phase amplitude of the load admittance Yarc based on arc furnace current I _L, the vertical axis represents the amplitude [pu] obtained by normalizing the horizontal axis is the frequency [Hz]. FIG. 6B shows the frequency characteristics of the positive phase, the vertical axis is the phase [°], and the horizontal axis is the frequency [Hz].

In FIG. 6A, the frequencies having positive phase amplitude of 10 [pu] or more are 101.8 Hz, 104.9 Hz, 163, 5 Hz, and 212.9 Hz, and these resonance frequencies are the filter resonance frequency of the arc furnace. Presumed.
In addition, the positive phase characteristic shown in FIG. 6B has many phase change points and it is difficult to specify the resonance frequency.

7 (a) is a frequency characteristic of the reverse-phase amplitude of admittance Yarc based on arc furnace current I _L, the vertical axis represents the amplitude [pu] obtained by normalizing the horizontal axis is the frequency [Hz]. FIG. 6B shows the frequency characteristics of the antiphase phase, the vertical axis is the phase [°], and the horizontal axis is the frequency [Hz]. Since the negative phase amplitude of 10 [pu] or more is not generated, it is not specified as the resonance frequency. It should be noted that there are resonance frequencies of 101.8 Hz, 104.9 Hz, 109.5 Hz, 140.4 Hz, 154.3 Hz, 160.5 Hz, and 163.5 Hz with a negative phase amplitude of 10 [pu] or less. That is, the same frequency component as the resonance frequency estimated from the positive phase amplitude is included. Note that the antiphase characteristics shown in FIG. 6B also have many phase change points, and it is difficult to specify the resonance frequency.

That is, the frequency specifying means 70 (FIG. 2) uses the positive phase amplitude characteristics shown in FIG. 6A to specify the specified resonance frequencies f _V2 , f _V3 , f _V4 , f _I2 , f _I3 , and f _I4. Is set to BEF90, 95 (FIG. 2).

As described above, according to the present embodiment, the reactive power compensator 100 that reduces the voltage fluctuation of the power system that is transmitted from the host system 110 to the arc furnace customer 150 via the transmission line 130 having impedance is the host system. extracting the reactive current component from the arc furnace current I _L flowing through the transmission line 130 to be measured by the line 110 side, to remove the frequency component of the specific frequency from the signal of the reactive current component, interconnection point measured by the upper grid 110 side It calculates the frequency characteristics of the load admittance Yarc from the voltage Vs and the arc furnace current I _L, identify the specific frequency from the amplitude and phase characteristics of the load admittance Yarc, a frequency component of a specific frequency (single or multiple specific frequencies) Positive phase current that cancels the signal of the removed reactive current component and the frequency of a specific frequency (single frequency or multiple specific frequencies) Min a compensation current Ic to the sum output to the arc furnace current I _L comprising a reverse-phase current that cancels the signals of the negative sequence current component is removed. Thereby, the reactive current (positive phase current) and the reverse phase current can be compensated on the higher system 110 side than the transmission line.

(Second Embodiment)
In the first embodiment uses an arc furnace positive phase admittance amplitude computed using the arc furnace current I _L, in addition to this, using the arc furnace reverse phase admittance amplitude computed using the arc furnace current I _L The resonance frequency can be specified in consideration of the calculated load admittance reverse phase amplitude.

The configuration of the reactive power compensator of the second embodiment is the same as that of the first embodiment, but the frequency specifying method is different. This frequency specifying method will be described with reference to the flowchart of FIG.
First, the amplitude and phase calculating means 60, similarly to the first embodiment, the arc furnace current I _L and the interconnection point voltage Vs to record 10 seconds, (S10), arc furnace current I _L and the interconnection point voltage by using the Vs, by calculating the arc furnace admittance positive-phase amplitude (Yarc positive phase amplitude) (S20), by using the arc furnace current _{I L} and the interconnection point voltage Vs, the arc furnace admittance reverse phase amplitude (Yarc The negative phase amplitude is calculated (S30).

  Then, the frequency specifying means 70 specifies the frequencies 101.8 Hz, 104.9 Hz, 163.5 Hz, and 212.9 Hz where the Yarc positive phase amplitude is a predetermined value 10 [pu] or more, and the Yarc negative phase amplitude is another predetermined value. The frequencies 101.8 Hz, 104.9 Hz, 109.5 Hz, 140.4 Hz, 154.3 Hz, 160.5 Hz, and 163.5 Hz of 5 [pu] or more are specified (S40). Furthermore, the frequency specifying means 70 specifies 101.8 Hz, 104.9 Hz, and 163.5 Hz, which are common frequencies of both, and sets a frequency (overlapping frequency) based on this specific frequency in the BEFs 90 and 95 (S50). . Then, this routine ends. Thereby, the frequency 212.9 Hz specified by the Yarc positive phase amplitude is removed.

(Third embodiment)
In the first embodiment uses an arc furnace positive phase admittance amplitude computed using the arc furnace current I _L, in addition, it was calculated using the compensation current Ic of the reactive power compensation device 100 load admittance Positive The resonance frequency can be specified in consideration of the amplitude.

The configuration of the reactive power compensator of the third embodiment is the same as that of the first embodiment, but the frequency specifying method is different. This frequency specifying method will be described with reference to the flowchart of FIG.
First, the amplitude and phase calculating means 60, similarly to the first embodiment, the arc furnace current I _L and the interconnection point voltage Vs to record 10 seconds, (S110), arc furnace current I _L and the interconnection point voltage The arc furnace admittance positive phase amplitude (Yarc positive phase amplitude) is calculated using Vs (S120).
Further, the amplitude phase calculation means 65 records the compensation current Ic and the linkage point voltage Vs for 10 seconds (S110), and uses the compensation current Ic and the linkage point voltage Vs to set the reactive power compensation device 100. An admittance positive phase amplitude (Yinv positive phase amplitude) is calculated (S130).

  Then, the frequency specifying means 70 specifies the frequencies 101.8 Hz, 104.9 Hz, 163.5 Hz, and 212.9 Hz with the Yarc positive phase amplitude of 10 [pu] or more, and the Yinv positive phase amplitude of 20 [pu] or more. The frequencies 104.9 Hz, 141.9 Hz, 163.5 Hz, and 212.9 Hz are specified (S140). Furthermore, the frequency specifying means 70 specifies 104.9 Hz, 163.5 Hz, and 212.9 Hz, which are common frequencies of both, and sets a frequency (overlapping frequency) based on this specific frequency in the BEFs 90 and 95 (S150). . Then, this routine ends. Thereby, the frequency 101.8 Hz specified by the Yarc positive phase amplitude is removed.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications such as the following are possible.
(1) In each of the above-described embodiments, the frequency setting is made common between the reactive current (positive phase) BEF 90 and the negative phase BEF 95, but one of the BEFs may be deleted.
In the case where 102 Hz is the LC resonance frequency, the positive phase BEF90 of 102 Hz-60 Hz = 42 Hz and the negative phase BEF95 of 102 Hz + 60 Hz = 162 Hz are required in principle. For example, for the positive phase of 42 Hz In some cases, only BEF90 is sufficient.
(2) In the above embodiments, the normal phase admittance or the negative phase admittance is calculated. However, even if the positive phase impedance or the negative phase impedance is calculated, these are regarded as the positive phase admittance or the inverse number of the negative phase admittance. It is.

It is a block diagram of the reactive power compensation system which is 1st Embodiment of this invention. It is a block diagram of the reactive power compensation apparatus which is 1st Embodiment of this invention. It is one block diagram of an amplitude phase calculating means. It is another block diagram of an amplitude phase calculating means. It is an equivalent circuit of a reactive power compensation system. It is a figure which shows the frequency characteristic of an arc furnace positive phase amplitude and a positive phase. It is a figure which shows the arc furnace reverse phase amplitude and the frequency characteristic of a negative phase. It is a figure which shows the frequency characteristic of the positive phase amplitude of a reactive power compensation apparatus. The flowchart which shows the method of specifying the filter frequency of 2nd Embodiment of this invention. It is a flowchart which shows the method of specifying the filter frequency of 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transformer 20 Power converter 30 Capacitor 40 Current control means 50 Current transformer 55 Current transformer 60 Amplitude phase calculation means 65 Amplitude phase calculation means 70 Frequency identification means 80 Reactive current extraction means 85 Reverse phase current extraction means 90, 95 BEF
DESCRIPTION OF SYMBOLS 100 Reactive power compensator 110 Host system 120 General customer 130,135 Transmission line 150 Arc furnace customer 152 Arc furnace 155 BPF
200 Reactive power compensation system 310, 315 αβ conversion means 320, 322, 324, 326 FFT conversion means 330, 335 Positive phase calculation means 340, 345, 380, 385 Amplitude phase separation means 350, 355 Divider 360, 365 Adder 370 375 Reverse phase calculation means

PT transformer CT current transformer Tr2A, Tr2B, Tr2C, Tr3, Tr4 transformer _{f2, f3, f4, f V2} , f V3, f V4, f I2, f I3, f I4 resonant frequency IL arc furnace current

Claims (11)

A positive phase current extraction means for extracting a positive phase current component from a load current flowing through the load;
A negative phase current extracting means for extracting a negative phase current component from the load current;
Amplitude phase calculating means for calculating a frequency characteristic of load admittance from the load current and interconnection point voltage,
Frequency specifying means for specifying a specific frequency from the amplitude characteristic and phase characteristic of the load admittance calculated by the amplitude phase calculating means;
A first filter for removing the frequency component of the singular frequency from the output signal of the positive phase current extraction means;
A second filter for removing the frequency component of the singular frequency from the output signal of the negative phase current extraction means;
A power converter that adds a compensation current composed of a positive phase current that cancels the output signal of the first filter and a negative phase current that cancels the output signal of the second filter to the load current; A reactive power compensator. The amplitude phase calculation means calculates a frequency characteristic of the positive phase amplitude of the load admittance,
The frequency specifying means selects a plurality of singular frequencies having a positive phase amplitude equal to or greater than a predetermined value, and sets the selected singular frequencies in the first filter and the second filter. 2. The reactive power compensator according to 1. The amplitude phase calculation means calculates the frequency characteristics of the negative phase amplitude of the load admittance and the positive phase amplitude of the load admittance from the load current and the interconnection point voltage,
The frequency specifying means selects a first singular frequency having a negative phase amplitude of the load admittance of a predetermined value or more and a second singular frequency having a positive phase amplitude of the load admittance of a predetermined value or more,
The plurality of common frequencies of the first singular frequency and the second singular frequency are specified, and the specified plurality of common frequencies are set in the first filter and the second filter. 2. The reactive power compensator according to 1. The amplitude phase calculation means calculates the frequency characteristics of the positive phase amplitude of the device admittance and the positive phase amplitude of the load admittance from the compensation current and the interconnection point voltage,
The frequency specifying means selects a first singular frequency in which the positive phase amplitude of the device admittance is a predetermined value or more and a second singular frequency in which the positive phase amplitude of the load admittance is a predetermined value or more,
The plurality of common frequencies of the first singular frequency and the second singular frequency are specified, and the specified plurality of common frequencies are set in the first filter and the second filter. 2. The reactive power compensator according to 1. A reactive power compensation system comprising a host system, a transmission line having impedance, a customer transmitted from the host system via the transmission line, and a reactive power compensator for reducing voltage fluctuations in the power system composed of these Because
The reactive power compensator is:
A positive phase current extraction means for extracting a positive phase current component from a load current flowing in the transmission line measured on the upper system side of the transmission line;
A negative phase current extracting means for extracting a negative phase current component from the load current;
Amplitude phase calculation means for calculating the frequency characteristics of load admittance from the interconnection point voltage measured on the higher system side of the transmission line and the load current;
Frequency specifying means for specifying a specific frequency from the amplitude characteristic and phase characteristic of the load admittance calculated by the amplitude phase calculating means;
A first filter that removes the frequency component of the singular frequency from the output signal of the reactive current extracting means;
A second filter for removing the frequency component of the singular frequency from the output signal of the negative phase current extraction means;
And a power converter for adding a compensation current composed of a positive phase current for canceling the output signal of the first filter and a negative phase current for canceling the output signal of the second filter to the load current. Reactive power compensation system. The customer includes an arc furnace and a band filter connected in parallel to the arc furnace and having a harmonic frequency of a commercial frequency as a resonance frequency,
6. The reactive power compensation system according to claim 5, wherein a difference between a specific frequency specified by the frequency specifying means and a harmonic frequency of the commercial frequency is generated by the power system. The amplitude phase calculation means calculates a frequency characteristic of the positive phase amplitude of the load admittance,
The frequency specifying means selects a plurality of singular frequencies having a positive phase amplitude equal to or greater than a predetermined value, and sets the selected singular frequencies in the first filter and the second filter. The reactive power compensation system according to claim 5 or 6. The amplitude phase calculation means calculates the frequency characteristics of the negative phase amplitude of the load admittance and the positive phase amplitude of the load admittance from the load current and the interconnection point voltage,
The frequency specifying means selects a first singular frequency having a negative phase amplitude of the load admittance of a predetermined value or more and a second singular frequency having a positive phase amplitude of the load admittance of a predetermined value or more,
The plurality of common frequencies of the first singular frequency and the second singular frequency are specified, and the specified plurality of common frequencies are set in the first filter and the second filter. The reactive power compensation system according to claim 5 or 6. The amplitude phase calculation means calculates the frequency characteristics of the positive phase amplitude of the device admittance and the positive phase amplitude of the load admittance from the compensation current and the interconnection point voltage,
The frequency specifying means selects a first singular frequency in which the positive phase amplitude of the device admittance is a predetermined value or more and a second singular frequency in which the positive phase amplitude of the load admittance is a predetermined value or more,
The plurality of common frequencies of the first singular frequency and the second singular frequency are specified, and the specified plurality of common frequencies are set in the first filter and the second filter. The reactive power compensation system according to claim 5 or 6.   7. The reactive power compensation system according to claim 5, wherein the reactive power compensator is configured such that the power converter adds and outputs a compensation current to the load current via a transformer. 8. A reactive power compensation method for a reactive power compensator for reducing voltage fluctuations in a power system including a host system, a transmission line having impedance, and a customer transmitted from the host system through the transmission line,
The reactive power compensator is:
Extracting a positive phase current component and a negative phase current component from a load current flowing in the power transmission line measured on the upper system side of the power transmission line;
Calculating a frequency characteristic of load admittance from the interconnection point voltage measured on the upper system side of the transmission line and the load current;
Identifying a singular frequency from the amplitude and phase characteristics of the load admittance;
Removing the frequency component of the singular frequency from the signal of the positive phase current component and the signal of the negative phase current component;
A compensation current comprising a positive phase current that cancels the signal of the positive phase current component from which the frequency component of the singular frequency has been removed and a negative phase current that cancels the signal of the negative phase current component from which the frequency component of the singular frequency has been removed is the load current. A reactive power compensation method characterized in that the step of adding to and outputting the output is executed.

Images