JP2008210145A - Control method for power conversion system, and power conversion system using control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively suppress voltage flickers which are generated by an arc furnace, a rolling mill, or the like, and in which a plurality of frequency components coexist, in a power conversion system. <P>SOLUTION: Voltage fluctuations are adjusted by synthesizing: fluctuation adjustment for calculating a feedforward loop canceling current command value Iref1, by calculating a canceling current Ifr from a current If before fluctuation adjustment, and performing dq inverse transformation on the difference ΔI1 between an output Ifr' obtained by applying a feedforward filter 2 to the canceling current Ifr and a command 5 for suppressing current fluctuation to zero; and fluctuation adjustment for calculating a feedback loop canceling current command value Iref2, by calculating a canceling current Ibr from a current Ib after the fluctuation adjustment, and performing the dq inverse transformation on an output Iref2' after the stabilization of the feedback loop for the difference ΔI2 between an output Ibr' obtained by applying a feedback filter 4 to the canceling current Ibr and a command 6 for suppressing current fluctuation to zero. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power conversion system control method and a power conversion system using the control method. More specifically, the present invention relates to a method for controlling a power conversion system suitable for use as a countermeasure for voltage flicker, and a power conversion system using the control method.

  In this specification, voltage flicker is used to mean a voltage component that oscillates around a 10 Hz component.

  There is a problem that voltage flicker generated by an arc furnace or a rolling mill causes flickering of illumination. For this reason, it is necessary to effectively suppress voltage fluctuation.

As a conventional technique for suppressing voltage fluctuation, for example, there is a control method of a reactive power compensator (Patent Document 1). As shown in FIG. 3, this control method detects the reactive power QL of the variable load 102 connected to the system bus 101 and supplies the reactive power supplied to the system bus 101 by the thyristor control reactor TCR with a size corresponding to this. In the reactive power compensator SVC that suppresses fluctuations in the voltage Vs of the system bus 101 by increasing / decreasing QTCR, the combined reactive power QT of the entire system is detected separately from the main control signal that has detected the reactive power QL of the variable load 102. At the same time, a signal obtained by passing this through the first-order lag element 103 is taken out as a sub control signal for correcting the control error, and the phase control of the thyristor control reactor TCR is performed by the added value of the main control signal and the sub control signal.
6-15115

  However, the control method of the reactive power compensator of Patent Document 1 includes a feedforward method in which the state quantity of the variable load 102 such as an arc furnace is directly detected and canceled, and the state quantity of the system bus 101 after the cancellation. Although the voltage fluctuation is suppressed by utilizing the feedback method at the same time, the performance of the power converter is not improved because the filter set to adapt to the visibility curve in each method is not applied. It has not been fully utilized. For this reason, it cannot be said that it is sufficient to cope with voltage flicker in which a plurality of frequency components are mixed, and it is difficult to say that voltage flicker can be effectively suppressed by the reactive power compensator of Patent Document 1.

  Note that the visibility curve (also referred to as flicker visibility curve) is a curve shown in FIG. 2, and is a curve representing a ratio for each frequency of a person who feels illumination flicker due to voltage fluctuation ( For example, Electricity System Utilization Council: Rules for Electricity System Utilization Council, June 13, 2006, 8th revision, p.44).

  In addition, when the voltage fluctuation is suppressed by utilizing the feedback method, a control state quantity with a time delay is used. Therefore, it is necessary to introduce a stabilization compensator in consideration of the stability of the feedback loop. . However, the control method of the reactive power compensator of Patent Document 1 is not a control method that sufficiently considers the stability of the feedback system because it does not have a stabilization compensator, and for this reason, the cancellation effect of the feedback method is not effective. It is difficult to say that the accuracy of voltage flicker control is high because the voltage fluctuation suppressing effect is reduced and the voltage flicker control effect is reduced.

  Furthermore, in the control method of Patent Document 1, reactive power is calculated and used as a state quantity used for controlling the reactive power compensator. In this case, the voltage information is used to use two pieces of information, voltage and current. There is a problem that the detection error and the current detection error are multiplied to appear as large noise, and it is difficult to say that the accuracy of voltage flicker control is high.

  Therefore, the present invention is particularly effective in a power conversion system that suppresses voltage fluctuations by using a feed-forward method and a feedback method at the same time to produce a voltage flicker that is generated by an arc furnace, a rolling mill, or the like and that includes a plurality of frequency components. It is an object of the present invention to provide a control method for a power conversion system that can be controlled in a controlled manner and a power conversion system using the control method.

  In order to achieve this object, the control method of the power conversion system according to claim 1 detects the current before fluctuation adjustment of the bus, performs dq conversion to calculate the reactive current, and calculates the reactive current before the fluctuation adjustment. The difference between the output obtained by applying the feedforward filter set according to the visibility curve used for calculating the ΔV10 calculation value to the reactive current before fluctuation adjustment and the command for suppressing the current fluctuation of the feedforward loop to zero Fluctuation adjustment of the feedforward method for calculating the feedforward loop reactive current command value by performing dq reverse transformation, and detecting the current after adjusting the fluctuation of the bus and performing dq transformation to calculate the reactive current and after the fluctuation adjustment The feedback filter that is set according to the visibility curve used for calculating the calculated value of ΔV10 for the reactive current is changed to the reactive current after fluctuation adjustment. A feedback method for calculating a feedback loop reactive current command value by performing dq inverse transformation on the output after stabilization of the feedback loop with respect to the difference between the output obtained by applying and the command for suppressing the current fluctuation of the feedback loop to zero. The fluctuation of the bus voltage is adjusted by combining the fluctuation adjustment.

  The power conversion system according to claim 2 is a first current transformer for detecting a current before fluctuation adjustment of a bus, and a first dq for calculating a reactive current by performing dq conversion on the current before fluctuation adjustment. Conversion device, feedforward filter set according to the visibility curve used to calculate ΔV10 calculation value for reactive current before fluctuation adjustment, and invalidity after applying feedforward filter to reactive current before fluctuation adjustment A first dq reverse conversion device that calculates a feedforward loop reactive current command value by performing dq reverse conversion on the difference between the current and the command that suppresses the current fluctuation of the feedforward loop to zero, and the current after adjusting the fluctuation of the bus A second current transformer to be detected, a second dq converter for calculating a reactive current by performing dq conversion on the current after fluctuation adjustment, and ΔV1 with respect to the reactive current after fluctuation adjustment. The difference between the feedback filter that is set according to the visibility curve used to calculate the zero calculation value, the reactive current after applying the feedback filter to the reactive current after fluctuation adjustment, and the command that suppresses the current fluctuation of the feedback loop to zero A stabilization compensator that stabilizes the feedback loop with respect to, a second dq inverse converter that calculates a feedback loop reactive current command value by performing dq inverse transformation on the output of the stabilizing compensator, and a feedforward loop invalid A pulse generator that outputs a pulse to the power converter based on the three-phase current command value obtained by adding the current command value and the feedback loop reactive current command value is provided.

  Therefore, according to the control method of the power conversion system and the power conversion system using the control method, the feedforward filter is designed based on the visibility curve used for calculating the ΔV10 calculated value, and the feedback filter is set to the ΔV10 calculated value. Since the design is based on the visibility curve used for the calculation, a filter set to adapt to the visibility curve is applied in each of the feedforward method and the feedback method.

  Note that the ΔV10 calculated value is a display scale of flicker generally used for arc furnace flicker (for example, Power System Utilization Council: Power System Utilization Council Rules, June 13, 2006, 8th meeting. Amendment, p. 44). More specifically, the ΔV10 calculated value represents a change in luminous flux of a 100V-60W incandescent lamp due to voltage fluctuation and a flickering feeling that affects human vision.

ここに、ａ_ｎ：変動周波数ｆ_ｎに対応するちらつき視感度係数，ΔＶ_ｎ：変動周波数ｆ_ｎに対応する成分の振れ幅。

Here, a _n is a flickering visibility coefficient corresponding to the fluctuation frequency f _n , and ΔV _{n is} a fluctuation width of the component corresponding to the fluctuation frequency f _n .

  In addition, according to the control method of the power conversion system and the power conversion system using the control method, a stabilization compensator is introduced in consideration of the stability of the feedback loop. The amount of state is canceled appropriately.

  Furthermore, since the reactive current is used as the state quantity used for the control of the power conversion system, the detection error of the state quantity is smaller than when using power.

  According to the control method of the power conversion system of the present invention and the power conversion system using the control method, the filter designed based on the visibility curve is applied in each of the feedforward method and the feedback method. By fully utilizing the performance of the converter, it is possible to appropriately cope with voltage flicker in which a plurality of frequency components are mixed, and it is possible to improve voltage flicker suppression performance.

  Further, according to the present invention, since the stabilization compensator is introduced in consideration of the stability of the entire control target system, it is possible to appropriately cancel the feedforward type state quantity by the feedback type state quantity. Yes, the accuracy of voltage flicker control can be improved.

  Further, according to the present invention, since the reactive current is used as the state quantity for control, it is possible to reduce the detection error of the state quantity as compared with the case of using power, and the voltage flicker control The accuracy can be improved.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  FIG. 1 shows an example of an embodiment of a power conversion system control method and a power conversion system using the control method of the present invention. This control method of the power conversion system detects the current If before fluctuation adjustment of the bus 18 and performs dq conversion to calculate the reactive current Ifr and uses it for calculating the ΔV10 calculation value for the reactive current Ifr before fluctuation adjustment. The difference ΔI1 between the output Ifr ′ obtained by applying the feedforward filter 2 set according to the visibility curve to the reactive current Ifr before fluctuation adjustment and the command 5 for suppressing the current fluctuation in the feedforward loop to zero is dq reverse. Fluctuation adjustment of the feedforward system that calculates the feedforward loop reactive current command value Iref1 by performing conversion, and the current Ib after fluctuation adjustment of the bus 18 is detected and dq conversion is performed to calculate the reactive current Ibr and the fluctuation adjustment The feedback filter 4 set according to the visibility curve used to calculate the ΔV10 calculation value for the subsequent reactive current Ibr is adjusted. By performing dq inverse transformation on the output Iref2 ′ after stabilization of the feedback loop with respect to the difference ΔI2 between the output Ibr ′ obtained by applying to the subsequent reactive current Ibr and the command 6 for suppressing the current fluctuation of the feedback loop to zero. The voltage fluctuation of the bus 18 is adjusted by combining the fluctuation adjustment of the feedback method for calculating the feedback loop reactive current command value Iref2.

  The method for controlling the power conversion system is realized as the power conversion system of the present invention. The power conversion system 1 according to the present embodiment calculates the reactive current Ifr by performing dq conversion on the first current transformer 10 that detects the current If before the fluctuation adjustment of the bus 18 and the current If before the fluctuation adjustment. One dq converter 11, a feedforward filter 2 set in accordance with the visibility curve used for calculating the ΔV10 calculation value for the reactive current Ifr before fluctuation adjustment, and feedforward to the reactive current Ifr before fluctuation adjustment The first dq for calculating the feedforward loop reactive current command value Iref1 by performing dq inverse transformation on the difference ΔI1 between the reactive current Ifr ′ after applying the filter 2 and the command 5 for suppressing the current fluctuation of the feedforward loop to zero Inverting device 12, second current transformer 13 for detecting current Ib after fluctuation adjustment of bus 18, and dq conversion for fluctuation-adjusted current Ib to perform reactive power A second dq converter 14 that calculates Ibr, a feedback filter 4 that is set in accordance with a visibility curve used to calculate a ΔV10 calculation value for reactive current Ibr after fluctuation adjustment, and reactive current after fluctuation adjustment A stabilization compensator 3 for stabilizing the feedback loop with respect to a difference ΔI2 between the reactive current Ibr ′ after applying the feedback filter 4 to Ibr and a command 6 for suppressing the current fluctuation of the feedback loop to zero, and a stabilization compensator A second dq inverse converter 15 that performs a dq reverse conversion on the output Iref2 ′ of 3 to calculate a feedback loop reactive current command value Iref2, a feedforward loop reactive current command value Iref1, and a feedback loop reactive current command value Iref2 A pulse generator 7 for outputting a pulse to the power converter 8 based on the added three-phase current command value Iref. That.

  The power converter 8 and the phase adjusting equipment 9 constitute a separately excited reactive power compensator.

  First, the adjustment of the voltage fluctuation by the feedforward loop of the power conversion system 1 will be described.

  The first current transformer 10 detects the current If before the fluctuation adjustment by the power conversion system 1 of the bus 18 to which the voltage fluctuation source 16 is connected. Then, the first current transformer 10 sends the value of the detected current If to the first dq converter 11. In Japan, the current If is a three-phase current composed of a system frequency component of 50 Hz or 60 Hz and other components.

  The voltage fluctuation generating source 16 is a high power consumption facility or facility that generates voltage flicker, such as an arc furnace or a rolling mill. Moreover, in FIG. 1, the code | symbol 17 shows a high-order system | strain.

  The first dq conversion device 11 calculates the reactive current Ifr by performing dq conversion on the current If before the fluctuation adjustment detected by the first current transformer 10. Specifically, the first dq conversion device 11 uses the variable converted from αβ conversion, that is, three-phase to two-phase, using Equation 2 for the current If, and dq conversion, that is, from the α-β axis orthogonal coordinate system using Equation 4. Conversion to the dq axis rotation coordinate system is performed. Then, the first dq converter 11 sends the calculated value of the reactive current Ifr to the feedforward filter 2.

ここに、Ｉfα：電流Ｉｆの無効電流Ｉfrの直交座標系α軸成分，Ｉfβ：電流Ｉｆの無効電流Ｉfrの直交座標系β軸成分，Ｉfa：電流Ｉｆの無効電流Ｉfrのａ相無効電流値，Ｉfb：電流Ｉｆの無効電流Ｉfrのｂ相無効電流値，Ｉfc：電流Ｉｆの無効電流Ｉfrのｃ相無効電流値。単位はいずれもｐｕ（ｐｅｒ ｕｎｉｔのこと）。なお、対象とするシステムの容量をＳ［ＶＡ］とし、線間電圧をＶ［Ｖ］（実効値）とすると、測定器で検出された電流［Ａ］（波高値）を数式３で割ることでｐｕの無次元の単位となる。

Here, Ifα: Cartesian coordinate system α-axis component of reactive current Ifr of current If, Ifβ: Cartesian coordinate system β-axis component of reactive current Ifr of current If, Ifa: a-phase reactive current value of reactive current Ifr of current If, Ifb: b-phase reactive current value of the reactive current Ifr of the current If, Ifc: c-phase reactive current value of the reactive current Ifr of the current If. All units are pu (per unit). When the capacity of the target system is S [VA] and the line voltage is V [V] (effective value), the current [A] (peak value) detected by the measuring instrument is divided by Equation 3. Becomes a dimensionless unit of pu.

ここに、Ｉfd：電流Ｉｆの無効電流Ｉfrの回転座標系ｄ軸成分［ｐｕ］，Ｉfq：電流Ｉｆの無効電流Ｉfrの回転座標系ｑ軸成分［ｐｕ］，Ｉfα：電流Ｉｆの無効電流Ｉfrの直交座標系α軸成分［ｐｕ］，Ｉfβ：電流Ｉｆの無効電流Ｉfrの直交座標系β軸成分［ｐｕ］，θ：直交座標系の軸と回転座標系の軸とがなす角［ラジアン］（以下、位相と呼ぶ）。

Here, Ifd: rotational coordinate system d-axis component [pu] of reactive current Ifr of current If, Ifq: rotational coordinate system q-axis component [pu] of reactive current Ifr of current If, Ifα: reactive current Ifr of current If Orthogonal coordinate system α-axis component [pu], Ifβ: Orthogonal coordinate system β-axis component [pu] of reactive current Ifr of current If, θ: Angle [radian] formed by the axis of the orthogonal coordinate system and the axis of the rotational coordinate system (radian) ( Hereinafter referred to as phase).

  Here, for the phase θ in Equation 2, it is not necessary to use the phase of the system voltage to which the power conversion system 1 is connected. What is necessary is just to calculate as (theta) = 2 (pi) f (here, f is system frequency [Hz]). The system frequency component is a DC component of the d-axis component Ifd and the q-axis component Ifq of the reactive current Ifr calculated by Equation 2, and the other components are frequency components obtained by subtracting the system frequency.

  The feedforward filter 2 is set so as to appropriately correspond to the visibility curve (FIG. 2) used for calculating the ΔV10 calculation value with respect to the reactive current Ifr calculated by the first dq converter 11. Specifically, a band pass filter represented by Formula 5 is used as the feedforward filter 2. The feedforward filter 2 outputs the reactive current Ifr 'after applying the filter to the reactive current Ifr.

ここに、Ｓ：ラプラス演算子，Ｑ：尖鋭さを表す［ｐｕ］，Ｋ：ゲイン［ｐｕ］，ω_０：角周波数［ラジアン／秒］。

Here, S: Laplace operator, Q: [pu] representing sharpness, K: gain [pu], ω ₀ : angular frequency [radians / second].

Note that K = 1 and ω ₀ = 2π10. Further, Q is set to about 0.3 to 0.5 in consideration of the visibility curve that peaks at 10 Hz shown in FIG. With this filter, a fundamental wave component that is a direct current component in the rotating coordinate system is removed, and a component around 10 Hz that affects voltage flicker is effectively extracted.

  Then, the first dq inverse converter 12 performs dq inverse conversion on the difference ΔI1 between the reactive current Ifr ′ after application of the filter that is the output of the feedforward filter 2 and the command 5 that suppresses the current fluctuation of the feedforward loop to zero. Then, the reactive current command value Iref1 of the feedforward loop is calculated. Specifically, the first dq inverse transformation device 12 uses the variable obtained by converting the difference ΔI1 by dq inverse transformation, that is, the dq-axis rotational coordinate system to the α-β-axis orthogonal coordinate system, using the formula 7 The inverse transformation of αβ, that is, the transformation from two phases to three phases is performed.

ここに、Ｉrefα1：フィードフォワードループの無効電流指令値Ｉref1の直交座標系α軸成分［ｐｕ］，Ｉrefβ1：無効電流指令値Ｉref1の直交座標系β軸成分［ｐｕ］，Ｉdref1：フィードフォワードループの電流変動をゼロに抑える指令の回転座標系ｄ軸成分であり値はゼロ［ｐｕ］，Ｉqref1：フィードフォワードループの電流変動をゼロに抑える指令の回転座標系ｑ軸成分であり値はゼロ［ｐｕ］，Ｉfrd’：フィードフォワードフィルタ適用後の無効電流Ｉfr’の回転座標系ｄ軸成分［ｐｕ］，Ｉfrq’：フィードフォワードフィルタ適用後の無効電流Ｉfr’の回転座標系ｑ軸成分［ｐｕ］，θ：位相［ラジアン］。

Where Irefα1: Cartesian coordinate system α-axis component [pu] of reactive current command value Iref1 of feedforward loop, Irefβ1: Cartesian coordinate system β-axis component [pu] of reactive current command value Iref1, Idref1: Current of feedforward loop The rotational coordinate system d-axis component of the command that suppresses the fluctuation to zero and the value is zero [pu], Iqref1: The rotational coordinate system q-axis component of the command that suppresses the current fluctuation of the feedforward loop to zero and the value is zero [pu] , Ifrd ': Rotational coordinate system d-axis component [pu] of reactive current Ifr' after applying the feedforward filter, Ifrq ': Rotational coordinate system q-axis component [pu] of reactive current Ifr' after applying the feedforward filter, θ : Phase [radian].

ここに、Ｉrefａ1：フィードフォワードループの無効電流指令値Ｉref1のａ相電流値，Ｉrefｂ1：無効電流指令値Ｉref1のｂ相電流値，Ｉrefｃ1：無効電流指令値Ｉref1のｃ相電流値，Ｉrefα1：無効電流指令値Ｉref1の直交座標系α軸成分，Ｉrefβ1：無効電流指令値Ｉref1の直交座標系β軸成分。単位はいずれもｐｕ。

Where Irefa1: a phase current value of reactive current command value Iref1 of feed forward loop, Irefb1: b phase current value of reactive current command value Iref1, Irefc1: c phase current value of reactive current command value Iref1, Irefα1: reactive current Cartesian coordinate system α-axis component of command value Iref1, Irefβ1: Cartesian coordinate system β-axis component of reactive current command value Iref1. The unit is pu.

  Next, adjustment of voltage fluctuation by the feedback loop of the power conversion system 1 will be described.

  The second current transformer 13 detects the current Ib after fluctuation adjustment by the power conversion system 1 of the bus 18. Then, the second current transformer 13 sends the value of the detected current Ib to the second dq converter 14.

  The second dq converter 14 performs dq conversion on the current Ib after fluctuation adjustment detected by the second current transformer 13 to calculate the reactive current Ibr. Specifically, the second dq conversion device 13 performs dq conversion on the current Ib using a variable that has been αβ converted using the matrix in the relational expressions of Expression 2 and Expression 4. Then, the second dq converter 14 sends the calculated value of the reactive current Ibr to the feedback filter 4.

  The feedback filter 4 is set so as to appropriately correspond to the visibility curve used for calculating the ΔV10 calculation value with respect to the reactive current Ibr calculated by the second dq converter 14. Specifically, a band pass filter shown in Formula 5 is used as the feedback filter 4. Then, the feedback filter 4 outputs the reactive current Ibr ′ after applying the filter to the reactive current Ibr.

Note that K = 1 and ω ₀ = 2π10. Q is set to about 0.3 to 0.5. With this filter, a fundamental wave component that is a direct current component in the rotating coordinate system is removed, and a component around 10 Hz that affects voltage flicker is effectively extracted.

  A difference ΔI2 between the reactive current Ibr ′ after application of the filter, which is the output of the feedback filter 4, and the command 6 for suppressing the current fluctuation of the feedback loop to zero is input to the stabilization compensator 3. Here, the value of the command 6 for suppressing the current fluctuation in the feedback loop to zero is zero for both the rotating coordinate system d-axis component and the rotating coordinate system q-axis component.

  The stabilization compensator 3 includes a second current transformer 13, a second dq converter 14, a feedback filter 4, a stabilization compensator 3, a second dq inverse converter 15, a pulse generator 7, and a power converter. 8 is a compensator for stabilizing the closed loop, ie, the feedback loop. Specifically, as the stabilizing compensator 3, a compensator that is a first-order advance / delay element expressed by Equation 8 and that advances the phase due to the time delay in the separately excited reactive power compensator is used in two stages. The stabilization compensator 3 outputs a stabilized reactive current Iref2 '.

ここに、Ｋ：ゲイン［ｐｕ］，Ｔ：時定数［秒］，Ｓ：ラプラス演算子。また、添字１〜４：時定数を設定するパラメータ。

Here, K: gain [pu], T: time constant [second], S: Laplace operator. Subscripts 1 to 4: Parameters for setting time constants.

  Then, the second dq inverse conversion device 15 uses the matrix in the relational expressions of Expressions 6 and 7 for the stabilized reactive current Iref2 ′ after stabilization, which is the output of the stabilization compensator 3, as a variable. The inverse current command value Iref2 of the feedback loop is output by performing αβ reverse conversion.

  Then, the reactive current command value Iref1 of the feedforward loop calculated as described above and the reactive current command value Iref2 of the feedback loop are added and input to the pulse generator 7 as a three-phase current command value Iref (= Iref1 + Iref2).

  The pulse generator 7 outputs a pulse to the power converter 8 based on the three-phase current command value Iref.

  As described above, the combined current Ic of the power conversion device 8 and the phase adjusting equipment 9 flows so as to be equal to the three-phase current command value Iref. That is, the voltage fluctuation of the bus 18 is suppressed.

  In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention.

It is a block diagram which shows the structure of an example of embodiment of the power conversion system of this invention. It is a figure which shows a visibility curve. It is a figure which shows the control circuit of the control system of the conventional reactive power compensation apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power conversion system 2 Feed forward filter 3 Stabilization compensator 4 Feedback filter 5 Command which suppresses current fluctuation of feedforward loop to zero 6 Command which suppresses current fluctuation of feedback loop to zero 7 Pulse generator 8 Power converter 9 Phase adjustment Facility 10 First current transformer 11 First dq converter 12 First dq inverse converter 13 Second current transformer 14 Second dq converter 15 Second dq inverse converter 16 Occurrence of voltage fluctuation Source 17 Host system 18 Bus

Claims (2)

  A feedforward filter that detects a current before fluctuation adjustment of the bus and performs dq conversion to calculate a reactive current and is set according to a visibility curve used for calculating a ΔV10 calculation value for the reactive current before fluctuation adjustment Feedforward loop reactive current command value is calculated by performing dq inverse transformation on the difference between the output obtained by applying the current to the reactive current before fluctuation adjustment and the command for suppressing the current fluctuation of the feedforward loop to zero. In accordance with the visibility curve used to calculate the ΔV10 calculation value for the reactive adjustment after the fluctuation adjustment of the system and the current after the fluctuation adjustment of the bus is detected and the dq conversion is performed to calculate the reactive current Applying the feedback filter set to the reactive current after the fluctuation adjustment to zero the output fluctuation and the current fluctuation of the feedback loop The voltage fluctuation of the bus is adjusted by synthesizing with the fluctuation adjustment of the feedback method for calculating the feedback loop reactive current command value by performing dq inverse transformation on the output after stabilization of the feedback loop with respect to the difference from the command to be suppressed to A method for controlling a power conversion system.   A first current transformer for detecting a current before fluctuation adjustment of the bus, a first dq converter for calculating a reactive current by performing dq conversion on the current before fluctuation adjustment, and a reactive current before fluctuation adjustment A feedforward filter set in accordance with a visibility curve used for calculating a ΔV10 calculation value, a reactive current after applying the feedforward filter to a reactive current before the fluctuation adjustment, and a current fluctuation of a feedforward loop A first dq reverse conversion device that calculates a feedforward loop reactive current command value by performing dq reverse conversion on the difference from the command that suppresses the current to zero, and a second current transformation that detects the current after adjusting the fluctuation of the bus A second dq converter for calculating a reactive current by performing dq conversion on the current after fluctuation adjustment, and calculating a calculated value of ΔV10 for the reactive current after fluctuation adjustment. The difference between the feedback filter set according to the visibility curve used for the calculation, the reactive current after applying the feedback filter to the reactive current after the fluctuation adjustment, and the command for suppressing the current fluctuation of the feedback loop to zero A stabilization compensator for stabilizing the feedback loop, a second dq inverse converter for calculating a feedback loop reactive current command value by performing dq inverse transformation on the output of the stabilization compensator, and the feed forward loop invalid A power conversion system comprising: a pulse generator that outputs a pulse to a power converter based on a three-phase current command value obtained by adding a current command value and the feedback loop reactive current command value.

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