JP2008048520A - Active filter and voltage flicker restraint method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a voltage flicker and stabilize a voltage in a distribution system. <P>SOLUTION: This distribution system has a device (2) for detecting a mount position voltage v which is a voltage in a connection point with a distribution line DL, a device (3) for generating a compensation current command value i<SP>*</SP><SB>C</SB>from the mount position voltage v, a device (4) for restraining the voltage flicker corresponding to the compensation current command value i<SP>*</SP><SB>C</SB>, a device (3b) for extracting a high harmonic element v<SB>h</SB>of the mount position voltage v, a device (3c) for generating a high harmonic restraint current value i<SP>*</SP><SB>Ch</SB>by multiplying the high harmonic element v<SB>h</SB>by a gain K<SB>v</SB>, a device (3g) for computing an instant voltage amplitude V<SP>*</SP><SB>amp</SB>of the mount position voltage v, a device (3i) for adjusting a basic wave ineffective current command value i<SP>*</SP><SB>Cfq</SB>so as to restrain the voltage flicker based on the voltage flicker (V<SP>*</SP><SB>amp</SB>-v<SB>amp</SB>) obtained from the gap to the specified value V<SP>*</SP><SB>amp</SB>of a system voltage, and an active filter AF having a device (3d) for computing the compensation current command value i<SP>*</SP><SB>C</SB>based on the high harmonic restraint current value i<SP>*</SP><SB>Ch</SB>and the basic wave ineffective current command value i<SP>*</SP><SB>Cfq</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an active filter and a voltage flicker suppressing method used in a power distribution system, and more particularly to a technique for suppressing voltage flicker and stabilizing voltage.

  Voltage flicker is a phenomenon in which the system voltage fluctuates between 1 and 20 Hz, and may cause troubles such as flickering of lighting and malfunction of equipment. Voltage flicker is caused by load fluctuation of a large-capacity load and inrush current accompanying start / stop, and an arc furnace, a welding machine, etc. are known as main flicker generation sources.

A self-excited reactive power compensator (STATCOM) is known as a flicker suppressing device. STATCOM is installed in the vicinity of the flicker generation source, current flicker is detected, and the reactive current is controlled. As a result, the voltage drop of the distribution line caused by the current flicker can be canceled and the voltage flicker of the system can be suppressed. Such a flicker suppressing device is installed on the customer side having a flicker generation source.
JP 2004-336870 A

  By the way, there are many unspecified flicker generation sources in the power distribution system. For this reason, it is difficult to specify the flicker generation source and individually detect the current flicker. Even if the current flicker can be detected, it is difficult to determine an effective reactive current command value if the flicker generation source and the installation point of the suppression device are separated.

  The present invention has been made in view of such a background, and an object thereof is to provide an active filter and a voltage flicker suppression method used in a distribution system capable of suppressing voltage flicker and stabilizing voltage. And

In order to achieve the above object, the invention according to claim 1 of the present invention is an active filter, the voltage detecting means for detecting an installation point voltage v which is a voltage at a connection point with a distribution line, and Control means for generating a compensation current command value i ^* _C from the installation point voltage v detected by the voltage detection means, and current control means for controlling the compensation current i _C according to the compensation current command value i ^* _C The control means includes a harmonic extraction means for extracting a harmonic component v _h of the installation point voltage v, and a harmonic suppression current command value i ^* _Ch by multiplying the harmonic component v _h by a gain K _v. A harmonic suppression gain multiplier for generating voltage, voltage flicker calculation means for calculating voltage flicker from the difference between the instantaneous voltage amplitude v _amp of the installation point voltage v and the reference value V ^* _amp of the system voltage, and the voltage flicker calculation means The fundamental wave reactive current command calculation means for adjusting the fundamental wave reactive current command value i ^* _Cfq so as to suppress the voltage flicker based on the voltage flicker (V ^* _amp− v _amp ) obtained in the above, and the harmonic suppression It is assumed that current calculation means for calculating the compensation current command value i ^* _C from the current command value i ^* _Ch and the fundamental wave reactive current command value i ^* _Cfq is provided.

The active filter of the present invention extracts the harmonic component v _h based on the installation point voltage v, multiplies the harmonic component v _h by the gain K _v to generate the harmonic suppression current command value i ^* _Ch , and sets the installation point. Calculate the voltage flicker from the difference between the instantaneous voltage amplitude v _{amp of the} voltage v and the reference value V ^* _amp of the system voltage, and disable the fundamental wave so as to suppress the voltage flicker based on the voltage flicker (V ^* _amp− v _amp ) and adjusting the current command value ⁱ _{* CFQ,} calculates a compensation current command value ⁱ _{* C} from harmonic suppression current command value ⁱ _{* Ch} and fundamental reactive current command value ⁱ _{* CFQ,} this compensation current command value ⁱ _{* C} Accordingly, voltage flicker is suppressed.

  Thus, the active filter of the present invention employs a voltage detection method as a control method for suppressing voltage flicker in the distribution system, and controls by detecting voltage flicker by the voltage v at the installation point of the active filter. Even when an unspecified number of flicker generation sources exist, voltage flicker can be effectively suppressed. Therefore, there is no need to install an active filter near the flicker generation source.

  Moreover, by using both voltage flicker suppression and harmonic suppression, it is possible to effectively suppress resonance of the power distribution system caused by the presence of a phase advance capacitor, and to stably suppress voltage flicker. .

The active filter of the present invention operates as a damping resistance of 1 / K _V [Ω] with respect to the harmonics of the distribution system. Therefore, not only the installation point but also the entire feeder can be adjusted by adjusting the gain K _V that determines the resistance value. The harmonic expansion phenomenon can be suppressed.

Of the present invention, the invention described in claim 2 is the active filter according to claim 1, wherein the fundamental wave reactive current command calculation means calculates an integral of the voltage flicker (V ^* _amp− v _amp ). V is obtained by integrating means for _performing positive or negative detection for detecting positive / negative of the voltage flicker (V ^* _amp− v _amp ) and counting means for outputting a value corresponding to the positive / negative number detected by the positive / negative detection means. ^* and means for outputting _{# 038,} the voltage flicker _^(V * _{amp -v} amp) to the voltage compensation gain multiplication unit for generating a value obtained by multiplying the proportional gain _{K P,} PI control or phase compensation, transmission of such band-limited the function G _p and having a fundamental wave reactive current command value calculating means for generating the fundamental wave reactive current command value i ^* _CFQ.

According to the present invention, with respect to the value obtained by multiplying the values in the proportional gain _{K P} corresponding to the voltage flicker ^{_{(V * amp -v amp),}} PI control or phase compensation, the transfer function of such bandwidth limitation _{G p} To generate the fundamental wave reactive current command value i ^* _Cfq, thereby generating a current having a phase opposite to that of the voltage flicker. The voltage drop caused by this current cancels out with the voltage flicker, and as a result, the voltage flicker can be suppressed.

  A third aspect of the present invention is the active filter according to the first aspect, wherein the fundamental reactive current command calculating means includes a low-pass filter.

で表されるものを用いる。 Because the distribution system there is a resonance point due to the effects of such phase advancing capacitor, the increase of the harmonic voltage is set high proportional gain K _P is a feedback gain for the voltage flicker suppression is a problem, the present invention As described above, by using the low-pass filter for the fundamental wave reactive current command calculation means, it is possible to reduce the gain for the harmonic component and suppress the harmonic voltage. As the low-pass filter, for example, when the time constant is _Tc , the transfer function _GP is expressed by the following equation:

Is used.

The invention according to claim 4 of the present invention is the active filter according to claim 3,
The harmonic extraction means includes a high pass filter.

で表されるものを用いる。 When trying to reduce the harmonic voltage near the resonance point by using a low-pass filter as described above, the phase characteristics of voltage flicker suppression appear to be affected. However, as in the present invention, a high-pass filter is used for the harmonic extraction means. By using the expansion suppression together, the harmonic voltage near the resonance point of the distribution system can be reduced. As the high-pass filter, for example, the transfer function G _h when the time constant was set to T _h is the formula

Is used.

  According to the present invention, voltage flicker in a distribution system can be effectively suppressed and voltage can be stabilized without detecting a current of a variable load.

FIG. 1 shows a configuration of a power distribution system model 1 described as an embodiment of the present invention. A 6.6 kV distribution system is modeled, and the distribution substation is the voltage source (v _s ). The actual power distribution system is composed of 4 to 6 feeders, and many consumers are connected. Here, only the trunk line of one feeder is modeled.

In the figure, L ₁ is the leakage inductance of the distribution transformer, L ₂ and L ₃ are the inductances of the distribution line DL, C1 to C3 are the capacitances of the phase advance capacitors for power factor improvement, and i _C is the active filter AF. Harmonic current drawn. The active filter AF is connected to the terminal of the feeder trunk line, and suppresses voltage flicker by a voltage at a connection point with the distribution line DL (hereinafter referred to as an installation point voltage v). In the distribution system terminal voltage (installation point voltage v), a harmonic expansion phenomenon in which the voltage harmonic expands several times can be confirmed, but the active filter AF suppresses the expansion of the harmonic.

FIG. 2 shows the configuration of the active filter AF of the present embodiment. The active filter AF is drive-controlled by the detection circuit 2 as voltage detection means for detecting the installation point voltage v, the controller 3 as control means for generating the compensation current command value i ^* _C from the installation point voltage v, and the controller 3. Main circuit 4 as voltage flicker suppression means.

The main circuit 4 includes a three-phase voltage type PWM converter 4c configured by a three-phase matching transformer 4a connected to an AC distribution line DL, a three-phase reactor 4b (inductance L _c ), and an IGBT (gate isolation type bipolar transistor). , And a DC capacitor 4d (capacitance C _dc ). The main circuit 4 sends the voltage v _dc of the DC capacitor 4 d to the controller 3.

The controller 3 compares the voltage v _dc of the DC capacitor 4d with the voltage reference value v ^* _dc , adjusts the current Δi ^* _{cd in} phase with the power supply voltage of the fundamental current, and averages the voltage v _dc of the DC capacitor 4d. Operates to keep the voltage constant.

FIG. 3 shows the configuration of the controller 3 of the active filter AF. As shown in the figure, the controller 3 represents the three-phase AC voltage V = (v _u , v _v , v _w ) detected by the detection circuit 2 in FIG. 2 as two components (d, q) of the rotational coordinates. A high-pass filter as a harmonic extraction means for extracting a harmonic component of the voltage dq-converted by the dq conversion circuit 3a and the dq conversion circuit 3a for conversion into the values (v _d , v _q ) HPF) 3b, multiplied harmonic suppression gain _{K V} the voltage harmonic component extracted by the high pass filter 3b and harmonic current command value ^{_{(i * Chd, i * Chq}} ) harmonic suppression gain multiplication unit 3c for generating, Current value calculation for adding the fundamental wave reactive current command value i ^* _Cfq output from the fundamental wave reactive current command calculation circuit 3i configured as described later and the q output component i ^* _{Chq of the} harmonic suppression gain multiplier 3c. Q component addition unit 3 as means , D component adding unit 3e as a current value calculating means for adding the d output component i ^* _Chd the DC current value .DELTA.i ^* _Cd outputted from the DC component gain multiplication unit 3k below harmonic suppression gain multiplication unit 3c, The outputs (q and d components of the compensation current command value i ^* _C ) i ^* _Cq and i ^* _Cd of the q component addition unit 3d and the d component addition unit 3e are _converted into current command values I ^* _C = (i ^{_{* Cu, i * Cv, i}} * d-q inverse conversion circuit 3f to be converted in _Cw), the square root of the amplitude (the square sum of the d-q converter 3a outputted from the voltage _{(v d, v q))} v voltage amplitude calculation circuit 3g for calculating a _{# 038,} installation point voltage amplitude _{v # 038} is a system voltage reference value ^V _{* # 038} become as fundamental reactive current command calculation circuit 3i for automatically adjusting the fundamental reactive current command value ⁱ _{* CFQ} DC output from main circuit 4 A DC voltage difference calculation unit 3j that takes a difference between the voltage value v _dc and a predetermined command value (DC voltage setting value) v ^* _dc, and a gain K _dc to the output (v _dc −v ^* _dc ) of the DC voltage difference calculation unit 3j And a three-phase AC fundamental wave (angular frequency ωt) supplied to the DC component gain multiplier 3k that generates a DC current value Δi ^* _Cd and the dq conversion circuit 3a and the dq inverse conversion circuit 3f. Has a fundamental wave generating circuit 3p.

次に、ｖ_ｄ，ｖ_ｑを電圧振幅演算回路３ｇに入力して、瞬時電圧振幅ｖ_ａｍｐを次式で演算する。

そして基本波無効電流指令演算回路３ｉでｖ_ａｍｐと系統電圧の基準値Ｖ^＊ _ａｍｐとの差から基本波無効電流指令値のｑ成分ｉ^＊ _Ｃｆｑを生成する。従って、電圧フリッカ抑制のための無効電流指令値ｉ^＊ _Ｃｆｑは次式で与えられる。

なお、ＰＩ制御器や位相補償、帯域制限などの伝達関数をＧ_ｐとし、フィードバックの偏差ｅ＝Ｖ^＊ _ａｍｐ−ｖ_ａｍｐを考慮すれば、電流指令値のラプラス変換は次式で表される。

一方、高調波拡大抑制制御の手順は次の通りである。すなわち、上記と同様に設置点電圧を検出してｄ−ｑ変換を行った後、ハイパスフィルタＧ_ｈを用いて抽出した交流成分ｖ_ｈｄ，ｖ_ｈｑにゲインＫ_ｖを乗じて、高調波拡大抑制制御のための電流指令値ｉ^＊ _Ｃｈｄ，ｉ^＊ _Ｃｈｑを次式から求める。

ここで、アクティブフィルタＡＦの電流制御が理想的に動作する電流値がｉ_Ｃｈｄ＝ｉ^＊ _Ｃｈｄ, ｉ_Ｃｈｑ＝ｉ^＊ _Ｃｈｑであると仮定すると、設置点電圧ｖの高調波成分ｖ_ｈに対して、アクティブフィルタＡＦは１／Ｋ_Ｖ ［Ω］の抵抗として動作する。つまり、アクティブフィルタＡＦは、配電系統の高調波に対してダンピング抵抗として動作し、抵抗値を決めるゲインＫ_Ｖを調整することにより設置点だけでなくフィーダ全体の高調波拡大現象を抑制することができる。 According to the controller 3 shown in FIG. 3, the current command value I ^* _C = (i ^* _Cu , i ^* _Cv , i ^* _Cw ) of the active filter AF is the voltage flicker suppression control, harmonic expansion suppression control, and direct current Determined by voltage control. Among these, the procedure of voltage flicker suppression control is as follows. A voltage detection method is used to suppress voltage flicker. That is, first, the components v _u , v _v , v _w of the installation point voltage v detected by the detection circuit 2 are converted into values v _d , v _q on the dq coordinate at the angular frequency ωt by the dq conversion circuit 3a. To do. This conversion is performed according to the following equation.

Next, v _d and v _q are input to the voltage amplitude calculation circuit 3g, and the instantaneous voltage amplitude v _amp is calculated by the following equation.

Then, the fundamental wave reactive current command calculation circuit 3i generates the q component i ^* _Cfq of the fundamental wave reactive current command value from the difference between v _amp and the reference value V ^* _amp of the system voltage. Accordingly, the reactive current command value i ^* _Cfq for suppressing voltage flicker is given by the following equation.

If the transfer function such as the PI controller, phase compensation, and band limitation is _Gp , and the feedback deviation e = V ^* _{amp− vamp} is taken into account, the Laplace transform of the current command value is expressed by the following equation.

On the other hand, the procedure of harmonic expansion suppression control is as follows. That is, after detecting the installation point voltage and performing dq conversion in the same manner as described above, the harmonic components are suppressed by multiplying the AC components v _hd and v _hq extracted using the high-pass filter G _h by the gain K _v. The current command values i ^* _Chd and i ^* _Chq for control are _obtained from the following equations.

Here, assuming that the current value at which the current control of the active filter AF ideally operates is i _Chd = i ^* _Chd, i _Chq = i ^* _Chq , the harmonic component v _h of the installation point voltage v The active filter AF operates as a resistance of 1 / K _V [Ω]. In other words, the active filter AF is able to suppress the harmonic expansion phenomenon of the entire feeder well established point by adjusting the gain K _V which acts as damping resistance, determine the resistance values for the harmonics of the distribution system it can.

なお、アクティブフィルタＡＦは、瞬時無効電力を制御して電圧フリッカを抑制するため、原理的な直流コンデンサ電圧に変動は生じない。従って、直流電圧制御は、電圧フリッカ抑制制御及び高調波拡大抑制制御の特性にほとんど影響しない。 On the other hand, the procedure of DC voltage control is as follows. In the DC voltage control, feedback control is performed so that the average value of the DC capacitor voltage v _dc is constant. That is, the direct-current capacitor voltage v _dc is compared with the command value v ^* _dc and multiplied by the feedback gain K _dc to give the fundamental wave active current command value i ^* _Cfd by the following equation.

Note that the active filter AF controls the instantaneous reactive power to suppress voltage flicker, so that the fundamental DC capacitor voltage does not fluctuate. Therefore, the DC voltage control hardly affects the characteristics of the voltage flicker suppression control and the harmonic expansion suppression control.

以下では直流電圧制御の影響を無視し、電流制御系の伝達関数を考慮する。この場合、電圧フリッカ抑制装置の伝達関数は、

となる。 The current command values for voltage flicker suppression control, harmonic expansion suppression control, and DC voltage control given as described above are added on the dq coordinate. Then, inverse conversion is performed on the added current command values to obtain current command values i ^* _Cu , i ^* _Cv , i ^* _Cw for each phase. By applying the current command values i ^* _Cu , i ^* _Cv , i ^* _Cw of each phase to the PWM converter 4c shown in FIG. 2, voltage flicker suppression control, harmonic expansion suppression control, and DC voltage control are realized. The The current control uses a 2-beat setting deadbeat control. In this case, the transfer function Gc (s) of the current control system is expressed by the following equation.

In the following, the influence of DC voltage control is ignored and the transfer function of the current control system is considered. In this case, the transfer function of the voltage flicker suppression device is

It becomes.

FIG. 4 shows the configuration of the fundamental wave reactive current command calculation circuit 3i. The control circuit 3i includes a positive / negative (sign) detector 31 serving as a positive / negative detection means for outputting a positive or negative signal according to the positive / negative of (V ^* _amp− v _amp ), and the sign of the output. An up / down counter 32 as counting means for outputting a value corresponding to a positive / negative number by up / down, a multiplier 33 for multiplying (V ^* _amp− v _amp ) by a proportional gain K _P , PI A fundamental wave reactive current command value calculating means for generating the fundamental wave reactive current command value i ^* _Cfq by a transfer function G _p 34 such as a controller, phase compensation, band limitation, and the like is provided.

  As described above, suppression of voltage flicker by the active filter AF is feedback control performed by detecting voltage flicker. In the following, the stability of this feedback control will be evaluated.

<Characteristic analysis>
The characteristics of voltage flicker suppression by the active filter AF are analyzed. First, the transfer function of flicker suppression control is derived by dq conversion of the entire system including the distribution system. FIG. 5 shows a simplified distribution system used to derive the transfer function. In the figure, r is the resistance component of the distribution line DL, L is the inductance of the distribution line DL, and C is the capacitance of the phase advance capacitor for power factor improvement. An active filter AL and a flicker generator FG are connected to the end of the distribution line DL.

と表すことができる。この式からｉ_Ｓを消去して整理すると、

となる。ここでこの式は２次の微分を含んでいるが、ｎ次の微分項

のｄ−ｑ変換は、

であるので、これを用いて（１２）式をｄ−ｑ変換すると、

となる。ただし、

である。さらにこの式をラプラス変換すると、

となる。ただし、

である。 Here, the circuit equation of each phase of the circuit shown in FIG.

It can be expressed as. If i _S is deleted from this formula and arranged,

It becomes. Here, this equation includes a second-order derivative, but an n-th derivative term.

The dq transformation of

Therefore, using this, when the equation (12) is dq transformed,

It becomes. However,

It is. Furthermore, if this equation is Laplace transformed,

It becomes. However,

It is.

の関係となる。
従って、（１７），（１９）式より、補償すべき電圧変動分ΔＶ_ｄ＝Ｖ_ｄ−Ｖ_ｄ０，ΔＶ_ｑ＝Ｖ_ｑ−Ｖ_ｑ０は、

となる。 When I _d = I _q = 0, the system voltage is in an initial state with no voltage fluctuation. If the system voltage at this time is V _d0 , V _q0

It becomes the relationship.
Therefore, from the equations (17) and (19), the voltage fluctuations to be compensated ΔV _d = V _d −V _d0 and ΔV _q = V _q −V _q0 are

It becomes.

である。これを（２０）式に代入すると

となる。ただし、Ｄ_１＝Ａ_１＋Ｋ_ＶＧ_ｈＢ_１，Ｄ_２＝Ａ_２＋Ｋ_ＶＧ_ｈＢ_２である。 On the other hand, Id and Iq are the sum of the current flowing through the flicker generation source and the active filter,

It is. Substituting this into equation (20)

It becomes. _However, a _{D 1 = A 1 + K V} G h B 1, D 2 = A 2 + K V G h B 2.

となる。ここでｖ_ｑ０＝０と仮定すると、

と近似することができる。（２２），（２４）式より、電圧フリッカ抑制の制御ループの一巡伝達関数は、

となる。 The voltage amplitude calculation circuit 3g in the block diagram of FIG. 3 has a nonlinear transfer function, but the small signal approximation for v _amp is

It becomes. Assuming that v _q0 = 0,

And can be approximated. From Equations (22) and (24), the loop transfer function of the control loop for suppressing voltage flicker is

It becomes.

と近似することができる。（２６）式を（２２）式に代入すると、

となる。従って、電圧フリッカ抑制を行った場合の電圧フリッカ発生源の電流と電圧フリッカΔＶamp（ｓ）の関係は、

となる。 Also, assuming that v _amp and v _d0 are substantially equal, the deviation e of the voltage amplitude is

And can be approximated. Substituting equation (26) into equation (22),

It becomes. Therefore, the relationship between the current of the voltage flicker generation source and the voltage flicker ΔVamp (s) when the voltage flicker suppression is performed is

It becomes.

<Simulation>
Next, a simulation was performed on the model shown in FIG. 5 in order to evaluate the control characteristics of the voltage flicker suppression control guided by the transfer function. The simulation results were compared with the Bode diagram. FIG. 6 shows circuit constants used in the simulation. Note that PSCAD, which is power system analysis software, was used for the simulation. The simulation was performed for each of conditions 1 and 2 shown in FIG. In both conditions 1 and 2, the proportional gain K _P = 0.3 A / V is set. In condition 2, a low-pass filter with a cutoff frequency of 30 Hz is inserted in order to reduce the gain for high frequency.

FIG. 8 shows a Bode diagram of a circuit transfer function of voltage flicker suppression control. In condition 1, the maximum gain value reaches 0 dB at a frequency of 280 Hz on the dq axis, and the phase is inverted by 180 degrees. Therefore, if a compensation current proportional to the voltage deviation is supplied using voltage flicker suppression control, the stability limit is reached at Kp = 0.3 A / V. The peak of the gain characteristic appears near the resonance frequency of the circuit, and the stability of voltage flicker suppression is determined by the resonance of the system. On the other hand, under the condition 2, the gain characteristic is −20 dB or less in the entire frequency region. Further, the phase characteristic is 180 ° near 150 Hz due to the phase delay caused by the filter, which suppresses the gain above the cutoff frequency and increases the gain margin to 47 dB. The stability limit at this time is around K _p = 50 A / V.

FIG. 9A shows a simulation result in the case of condition 1, and FIG. 9B shows a simulation result in the case of condition 2. In this simulation, a reactive current having a flicker component having a frequency of 5 Hz and an execution value of 8 A is supplied from a flicker generation source, and current control is performed at K _v = 20 A / V.

FIG. 9A shows the proportional gain K _P and the voltage fluctuation ΔV _d to be compensated when the gain is (a) K _P = 0.3 A / V and (b) K _P = 0.35 A / V with respect to the condition 1. It is a waveform of the current i _C flowing into the active filter AF. K _P is initially set to 0 A / V and is increased over a period of 200 ms. (A) Both ΔV _d and i _C are stably controlled when K _P = 0.3 A / V, but (b) ΔV _d and i _C are 280 Hz when K _P = 0.35 A / V. Diverging with vibration.

FIG. 9B shows waveforms of K _P , ΔV _d , and i _C when the gain is (a) K _P = 45 A / V and (b) K _P = 50 A / V with respect to Condition 2. (A) It is stable when K _P = 45 A / V, but it is unstable when (b) K _P = 50 A / V.

  As described above, the analysis result and the simulation result almost coincided, and the validity of the transfer function represented by the above equation (25) could be confirmed.

そして電圧フリッカの抑制効果は、（２８）式のΔＶ_ａｍｐを用いて、

で表わすことができる。 Next, the voltage flicker suppression effect when voltage flicker suppression is applied is derived using the above transfer function. In the present embodiment, the suppression effect when voltage flicker suppression is applied is evaluated by the ratio of voltage flicker before suppression (K _P , K _V = 0 A / V) and after suppression. When K _P , K _V = 0 A / V is substituted into the above equation (28), the voltage flicker before flicker suppression is expressed by the following equation.

The voltage flicker suppression effect is obtained by using ΔV _amp in the equation (28).

It can be expressed as

<Combination of harmonic expansion suppression>
As described above, there are resonance points in the distribution system, and there are peaks in the gain characteristics. For this reason, it is difficult to set a high feedback gain for suppressing voltage flicker. Therefore, in this embodiment, resonance of the distribution system is suppressed by using harmonic expansion suppression together.

で定義される一次ローパスフィルタを用い、Ｋｖ＝１Ａ／Ｖとした場合である。図１０に示すように、高調波抑制制御によってゲイン特性に存在していたピークが良好に抑えられていることがわかる。なお、ゲイン余有は２４ｄＢであるので安定限界はＫ_Ｐ＝４．７Ａ／Ｖである。 FIG. 10 shows a Bode diagram of a round transfer function when harmonic expansion suppression is used together. In FIG. 3, the time constant T _ch = 1/15 s and G _h in the harmonic detection filter (high-pass filter 3b) in FIG.

This is a case where the first-order low-pass filter defined by (1) is used and Kv = 1 A / V. As shown in FIG. 10, it can be seen that the peak existing in the gain characteristic is well suppressed by the harmonic suppression control. Since the gain margin is 24 dB, the stability limit is K _P = 4.7 A / V.

FIG. 11 shows the effect of suppressing voltage flicker when the proportional gain K _P for controlling voltage flicker is set to 4.5 A / V. As understood from the figure, the suppression effect on voltage flicker of 20 Hz or less can be improved to −5.7 dB by using the harmonic expansion suppression together. However, harmonic voltages near 300 Hz and 1 kHz or higher are amplified. While it is possible suppressed by increasing the control gain K _V for harmonic voltage of these 300 Hz, 1 kHz harmonic voltage increases rather. This is because harmonic components are mixed in the detected value of the voltage flicker, resulting in a phase delay.

  Such a harmonic voltage can be suppressed by performing band limitation using, for example, a low-pass filter. Here, in order to reduce the harmonic voltage near the resonance point of the distribution system using the low-pass filter, it is necessary to set the cut-off frequency to about 30 Hz. In this case, the phase characteristics of voltage flicker suppression are affected. On the other hand, if the harmonic expansion suppression is used in combination, the harmonic voltage near the resonance point of the distribution system can be reduced. In this case, the cut-off frequency of the low-pass filter may be set so as to reduce the increase in harmonic components of 1 kHz or more, thereby reducing the change in phase characteristics for suppressing voltage flicker.

Ｔ_ｃ＝１／５０ｓとした。また高調波拡大抑制には、Ｇ_ｈが次式で表される二次のハイパスフィルタ

を用い、Ｔ_ｈ＝１／３０ｓ，Ｋ_ｖ＝２Ａ／Ｖとした。図１２に示すように、ローパスフィルタを用いることで高周波成分に対するゲインを大幅に低減できることがわかる。またこのときの位相余有は４３゜であり、安定性も大幅に改善されている。 FIG. 12 shows a Bode diagram of the circular transfer function with the band limited (K _P = 53 A / V). In this Bode diagram, the voltage flicker suppression compensator (fundamental wave reactive current command calculation circuit 3i) is a second-order low-pass filter in which _GP is expressed by the following equation:

T _c was set to 1/50 s. In order to suppress harmonic expansion, a second-order high-pass filter in which G _h is expressed by the following equation:

And T _h = 1/30 s and K _v = 2 A / V. As shown in FIG. 12, it can be seen that the gain for the high frequency component can be significantly reduced by using the low pass filter. Further, the phase margin at this time is 43 °, and the stability is greatly improved.

Shows the voltage flicker suppressing effect _{ΔV amp} / ΔV amp0 Figure 13. As shown in the figure, the suppression effect for 1 to 20 Hz is -16 dB or less, and if limited to 1 to 10 Hz, the suppression effect is -20 dB or less, and the voltage flicker is reduced to 1/10. The harmonic voltage near the resonance point of 300 Hz in the distribution system is reduced to about -6 dB, and the harmonic voltage of 1 kHz or more is reduced to almost 0 dB.

<Experimental result>
FIG. 14 shows experimental waveforms. In the experiment, a filter having a transfer function of equations (32) and (33) is used. Further, the proportional gain K _P = 53 A / V and the harmonic expansion suppression gain K _V = 2 A / V, which are voltage flicker suppression gains.

FIG. 14 shows the case where the reactive current of the flicker generation source changes from the delay 5A to the advance 5A in a stepwise manner, and (a) shows the case where the voltage flicker suppressing device is stopped. In this case, the voltage change of about 5V to the d-axis voltage [Delta] V _d with the phase change of the current flicker appearing. The d-axis voltage ΔVd and the q-axis voltage ΔVq include second-order and sixth-order voltage harmonics. This is considered to be due to the reverse voltage of the system voltage and the fifth and seventh harmonic components.

On the other hand, (b) shows a case where the voltage flicker suppressing device is operated. This voltage change [Delta] V _d If is suppressed. Further, the sixth harmonic of Δv _q is suppressed, but the second order component is hardly reduced. This is because the suppression effect in the vicinity of 100 Hz is almost 0 dB as shown in FIG.

FIGS. 15 to 17 show experimental results when voltage flicker is generated by changing the reactive current of the flicker generation source by ± 5 A in a sine wave form. 15 shows the case where the flicker frequency f _{f is set} to 1 Hz, FIG. 16 shows the case where the flicker frequency f _{f is set} to 5 Hz, and FIG. 17 shows the case where the flicker frequency f _f is set to 25 Hz. In any case, (a) when the voltage flicker suppressing device is stopped, a voltage flicker of about 5 V appears in ΔVd, but (b) when the voltage flicker suppressing device is operated, the voltage flicker is about 1 / 10 is suppressed.

FIG. 18 shows measurement results of voltage flicker. A sine wave current flicker of 1 to 25 Hz was generated from a flicker generation source, and ΔV _amp before and after the operation of the voltage flicker suppression device was obtained by Fourier transform. In the experiment, the voltage flicker is reduced by 18 dB in the range of 1 to 10 Hz. Moreover, the experimental result and the characteristic of the above-mentioned theoretical value are almost in agreement.

  The above description of the embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof.

It is a figure which shows the structure of the power distribution system model 1 demonstrated as one Embodiment of this invention. It is a figure which shows the structure of the active filter AF demonstrated as one Embodiment of this invention. It is a figure which shows the structure of the controller 3 demonstrated as one Embodiment of this invention. It is a figure which shows the structure of the fundamental wave reactive current command calculating circuit 3i demonstrated as one Embodiment of this invention. It is a figure which shows the simplified power distribution system used for derivation | leading-out of the transfer function demonstrated as one Embodiment of this invention. It is a figure which shows the circuit constant used for the simulation demonstrated as one Embodiment of this invention. It is a figure which shows the conditions of the simulation demonstrated as one Embodiment of this invention. It is a Bode diagram of a circuit transfer function of voltage flicker suppression control explained as an embodiment of the present invention. It is a figure which shows the simulation result in the case of the conditions 1 demonstrated as one Embodiment of this invention. It is a figure which shows the simulation result in the case of the conditions 2 demonstrated as one Embodiment of this invention. It is a Bode diagram of a circuit transfer function when using harmonic expansion suppression explained as one embodiment of the present invention together. Is a diagram showing the inhibitory effect of voltage flicker when the proportional gain K _P to control the voltage flicker described as an embodiment was set at 4.5A / V of the present invention. FIG. 4 is a Bode diagram of a band-limited circuit transfer function described as an embodiment of the present invention. Voltage flicker suppressing effect _{ΔV amp} / ΔV amp0 described as an embodiment of the present invention. FIG. It is a figure which shows the experimental waveform when the reactive current of a flicker generation source changes stepwise from 5 A of delays to 5 A demonstrated as one Embodiment of this invention. It is a figure which shows the experimental result at the time of setting the flicker frequency _ff to 1 Hz by changing the reactive current of a flicker generation source by varying ± 5 A in a sine wave shape, and setting the flicker frequency f _f as an embodiment of the present invention. It is a figure which shows the experimental result at the time of setting the flicker frequency _ff to 5 Hz by changing the reactive current of a flicker generation source as a sine wave shape by varying ± 5 A, and setting the flicker frequency f _f as one embodiment of the present invention. It is a figure which shows the experimental result at the time of changing the reactive current of a flicker generation source to sine wave form +/- 5A, generating voltage flicker, and setting the flicker frequency _ff to 25 Hz demonstrated as one Embodiment of this invention. It is a figure which shows the measurement result of the voltage flicker demonstrated as one Embodiment of this invention.

Explanation of symbols

AF active filter DL distribution line L1-L3 inductance v installation point voltage 2 detection circuit 3a dq conversion circuit 3b high pass filter 3c harmonic suppression gain multiplication unit 3d, 3e addition unit 3f dq inverse conversion circuit 3g voltage amplitude calculation circuit 3i Fundamental wave reactive current command calculation circuit 3j DC voltage difference calculation unit 3k DC component gain multiplication unit 3p Fundamental wave generation circuit 4 Main circuit 4a Three-phase matching transformer 4b Three-phase reactor 4c Three-phase voltage type PWM converter 4d DC capacitor 3l Positive / negative Detector 32 Up / down counter 33 Gain multiplier 34 Transfer function G _p such as PI controller, phase compensation, band limitation

Claims (8)

Voltage detecting means for detecting an installation point voltage v which is a voltage at a connection point with the distribution line;
Control means for generating a compensation current command value i ^* _C from the installation point voltage v detected by the voltage detection means;
Current control means for controlling the compensation current i _C according to the compensation current command value i ^* _C ,
The control means includes
Harmonic extraction means for extracting a harmonic component v _h of the installation point voltage v;
A harmonic suppression gain multiplier that multiplies the harmonic component v _h by a gain K _v to generate a harmonic suppression current command value i ^* _Ch ;
Voltage flicker calculation means for calculating voltage flicker from the difference between the instantaneous voltage amplitude v _amp of the installation point voltage v and the reference value V ^* _amp of the system voltage;
A fundamental wave reactive current command computing means for adjusting a fundamental wave reactive current command value i ^* _Cfq so as to suppress voltage flicker based on the voltage flicker (V ^* _amp− v _amp ) obtained by the voltage flicker computing means; ,
An active filter comprising: current calculation means for calculating the compensation current command value i ^* _C from the harmonic suppression current command value i ^* _Ch and the fundamental reactive current command value i ^* _Cfq . The active filter according to claim 1,
The fundamental reactive current command calculation means is:
It said voltage flicker _^(V * _{amp -v} amp) or integration means for calculating the integral of the voltage flicker _^(V * _{amp -v} amp) positive / negative to positive and negative detection means for detecting positive and negative detected by the positive and negative detection means Means for outputting V ^* _amp by means of counting means for outputting a value according to the number of
A voltage compensation gain multiplier for generating a value obtained by multiplying the voltage flicker (V ^* _amp− v _amp ) by a proportional gain K _P ;
Active filter, characterized in that it comprises a PI controller and a phase compensator, and a transfer function G _p by the fundamental wave reactive current command value calculating means for generating the fundamental wave reactive current command value i ^* _CFQ such band limitation. The active filter according to claim 1,
The fundamental filter reactive current command calculation means includes a low-pass filter. The active filter according to claim 3,
The active filter, wherein the harmonic extraction means includes a high-pass filter. Voltage detecting means for detecting an installation point voltage v which is a voltage at a connection point with the distribution line;
Control means for generating a compensation current command value i ^* _C from the installation point voltage v detected by the voltage detection means;
Current control means for controlling the compensation current i _C according to the compensation current command value i ^* _C ,
The control means includes
Harmonic extraction means for extracting a harmonic component v _h of the installation point voltage v;
A harmonic suppression gain multiplier that multiplies the harmonic component v _h by a gain K _v to generate a harmonic suppression current command value i ^* _Ch ;
Voltage flicker calculation means for calculating voltage flicker from the difference between the instantaneous voltage amplitude v _amp of the installation point voltage v and the reference value V ^* _amp of the system voltage;
A fundamental wave reactive current command calculation means for adjusting a fundamental wave reactive current command value i ^* _Cfq so as to suppress voltage flicker based on the voltage flicker (V ^* _amp− v _amp ) obtained by the voltage flicker calculation means; ,
An active filter having a current calculation means for calculating the compensation current command value i ^* _C from the harmonic suppression current command value i ^* _Ch and the fundamental reactive current command value i ^* _Cfq is connected to a distribution line. Voltage flicker suppression method that suppresses voltage flicker. The voltage flicker suppressing method according to claim 5,
The fundamental reactive current command calculation means is:
It said voltage flicker _^(V * _{amp -v} amp) or integration means for calculating the integral of the voltage flicker _^(V * _{amp -v} amp) positive / negative to positive and negative detection means for detecting positive and negative detected by the positive and negative detection means Means for outputting V ^* _amp by means of counting means for outputting a value according to the number of
A voltage compensation gain multiplier for generating a value obtained by multiplying the voltage flicker (V ^* _amp− v _amp ) by a proportional gain K _P ;
PI control or phase compensation, voltage flicker suppression method characterized by having a transfer function G _p by the fundamental wave reactive current command value calculating means for generating the fundamental wave reactive current command value i ^* _CFQ such band limitation. The voltage flicker suppressing method according to claim 5,
The method for suppressing voltage flicker, wherein the fundamental wave reactive current command calculation means includes a low-pass filter. The method for suppressing voltage flicker according to claim 7,
The harmonic extraction means includes a high-pass filter.

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