JP6179586B2 - Resonance suppression device - Google Patents

Description

  The present invention relates to a resonance suppression device.

  In recent years, the spread of renewable energy has progressed, and a large-scale wind farm (collective wind power plant) equipped with many wind power generators has also been constructed.

  The wind power generator includes a converter (AC-DC) that converts the generated power into direct current (AC-DC) and an inverter that converts the direct current into alternating current (DC-AC), and further eliminates harmonic current generated by the inverter. A harmonic filter is also provided. However, when a wind power generator equipped with a harmonic filter is connected (connected) to the power grid, the capacitance of the harmonic filter (capacitance) and the inductance of the power grid or transformer (inductance) Resonance may occur and the output voltage may become unstable.

  Thus, for example, in Patent Document 1, such a resonance is suppressed by connecting a resistor in series with the capacitance of the harmonic filter, and stable operation can be continued without superimposing a resonance frequency component on the output voltage. Wind power generation facilities are disclosed. For example, Non-Patent Document 1 discloses a technique for suppressing resonance using a passive notch filter or a C-type bandpass filter.

JP 2005-184990 A JP 2003-174725 A

M. Bradt, et al., "Harmonics and Resonance Issues in Wind Power Plants," Power and Energy Society General Meeting, 2011 IEEE, pp. 1-8, 24-29 July 2011

  However, in the wind power generation facility of Patent Document 1, since the resistance value Rh is given according to the system reactance X0 viewed from the induction machine of the wind power generation facility, the resonance point changes when the configuration of the power system changes, Resonance may recur. Further, even in the method using the filter of Non-Patent Document 1, since the resonance points (resonance frequencies) change when the configuration of the power system changes, it is necessary to suppress those resonance points.

  Furthermore, even if the configuration of the power system does not change, in a wind power plant equipped with a plurality of wind power generators, the capacitance of the harmonic filter changes according to the number of connected wind power generators, and the resonance point Will also change. That is, since the capacitances of the harmonic filters included in each wind power generator are connected in parallel, the resonance frequency decreases as the number of connected wind power generators increases, for example, as shown in FIG. Therefore, it is difficult to use the resonance suppression methods of Patent Literature 1 and Non-Patent Literature 1 at a wind power plant where the number of wind power generators connected to the power system changes.

The main serving present invention that solve the problems described above, the power device having a harmonic filter is a suppressing resonance suppressing apparatus resonance generated by being connected to the power grid, the said power system An inverter that supplies an alternating current in parallel with a power device, and a current that generates a current command value that moves a resonance frequency of the harmonic filter to a high frequency side, by inputting a voltage at a connection point between the power device and the power system. a command value generating unit, based on the current command value to have a, a current control unit for controlling the alternating current output from the inverter, the current command value generating portion is connected to said electric power system The resonance suppression apparatus generates the current command value based on the number of the power devices .

Also, still another primary aspect of the present invention to solve the aforementioned problems is a suppress resonance suppressing apparatus resonant power device having a harmonic filter is generated by being connected to an electric power system, coefficient together A plurality of different reactors, a reactor selection unit that selects one or more reactors from the plurality of reactors, and the one or more reactors selected by the reactor selection unit among the plurality of reactors A switching circuit connected in parallel with the capacitance, and the reactor selection unit selects the one or more reactors from the plurality of reactors based on the number of the power devices connected to the power system. This is a resonance suppression device.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, resonance can be suppressed even when the resonance point changes. In particular, in a wind power plant including a plurality of wind power generators, resonance can be suppressed even when the number of connected wind power generators to the power system changes.

It is a block diagram which shows the structure of the resonance suppression apparatus in 1st Embodiment of this invention. It is a figure explaining the resonance which generate | occur | produces in the state where the resonance suppression apparatus is not installed. It is a figure explaining the effect | action which a resonance suppression apparatus provided with the integral filter suppresses resonance. It is a figure explaining the effect | action which a resonance suppression apparatus provided with the primary delay filter suppresses resonance. It is a figure explaining that the resonance frequency moves to the high frequency side by a resonance suppression device. It is a schematic diagram which shows an example of the voltage v and electric current i, i1, i2 in the state where the resonance suppression apparatus is not installed. It is a schematic diagram which shows an example of the voltage v and electric current i, i1, i2 by which the resonance was suppressed by the resonance suppression apparatus provided with the integral filter. It is a schematic diagram which shows an example of the relationship between the filter coefficient in a resonance suppression apparatus provided with the integral filter, and the resonance suppression effect. It is a schematic diagram which shows an example of the voltage v and electric current i, i1, i2 by which the resonance was suppressed by the resonance suppression apparatus provided with the primary delay filter. It is a schematic diagram which shows an example of the relationship between the filter coefficient in a resonance suppression apparatus provided with the first order lag filter, and the resonance suppression effect. It is a block diagram which shows the structure of the resonance suppression apparatus in 2nd Embodiment of this invention. It is a figure explaining the method of calculating a resonance frequency from the number of connected wind power generators. It is a block diagram which shows the structure of the resonance suppression apparatus in 3rd Embodiment of this invention. It is a block diagram which shows the structure of the resonance suppression apparatus in 4th Embodiment of this invention. It is a block diagram which shows the structure of the resonance suppression apparatus in 5th Embodiment of this invention. It is a block diagram which shows the structure of the resonance suppression apparatus in 6th Embodiment of this invention. It is a block diagram which shows the structure of the resonance suppression apparatus in 7th Embodiment of this invention. It is a block diagram which shows the structure of the resonance suppression apparatus in 8th Embodiment of this invention. It is a block diagram which shows the structure of the resonance suppression apparatus in 9th Embodiment of this invention. It is a figure which shows the relationship between the number of connected wind power generators, and a resonant frequency.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

<First Embodiment>
=== Configuration of Resonance Suppressor ===
Hereinafter, with reference to FIG. 1, the structure of the resonance suppression apparatus in the 1st Embodiment of this invention is demonstrated.

  The resonance suppression device 1a illustrated in FIG. 1 is installed in, for example, a wind power plant, and suppresses resonance that occurs when the wind power generator 3 including the harmonic filter 31 is connected to the power system 5. It is a device. The resonance suppression device 1 a includes a filter 11, an addition unit 12, a current control unit 13, a parallel inverter 14, a DC power supply 15, a resonance detection unit 16, and a coefficient setting unit 17. In the present embodiment, the filter 11 and the coefficient setting unit 17 correspond to the current command value generation unit 10.

  In FIG. 1, the wind power generator 3 represents the number of wind power generators connected to the power system 5. C1 represents a combined capacitance of the harmonic filters of the wind power generators connected to the power system 5, and L1 represents a combined inductance of transformers that connect the wind power generators to the power system 5, respectively. Inductance is shown. Further, L2 represents the inductance of the power system 5. In addition, in FIG. 1, the structure for 1 phase is shown, and when the wind power generator 3 is connected to the three-phase system | strain, the resonance suppression apparatus 1a is equipped with the same structure with respect to each phase. Shall.

The filter 11 is a digital filter having an integral characteristic or a first-order lag characteristic. Further, the voltage v at the connection point between the wind power generator 3 and the power system 5 is input to the filter 11, and the current command value i ^* for the output current i of the parallel inverter 14 is output from the filter 11.

  The connection point voltage v is also input to the resonance detection unit 16, and the detected resonance frequency f1 is output from the resonance detection unit 16. Further, the resonance frequency f <b> 1 is input to the coefficient setting unit 17, and the filter coefficient is input to the filter 11 from the coefficient setting unit 17. Here, when the filter 11 is an integral filter, an inductance L is input as a filter coefficient. When the filter 11 is a first-order lag filter, a resistance R and an inductance L are input as filter coefficients. The

The adder 12 receives the output current i of the parallel inverter 14 and the current command value i ^{* corresponding} thereto, and the adder 12 sends the current control unit 13 the difference between the current command value i ^* and the output current i ( i ^* -i) is input. Further, a voltage command value v ^* is output from the current control unit 13.

A DC power supply 15 is connected to the parallel inverter 14. Further, the voltage command value v ^* is input to the parallel inverter 14, and the alternating current i is output from the parallel inverter 14. The parallel inverter 14 is connected in parallel to the power system 5 via a transformer (not shown), and the alternating current i output from the parallel inverter 14 is in parallel with the output current i1 of the wind power generator 3. It is supplied to the electric power system 5. As such a parallel inverter 14, the parallel compensation part with which UPFC (Unified Power Flow Controller: Integrated power flow control apparatus) is provided can also be used (for example, refer patent document 2).

=== Operation of Resonance Suppressor ===
Next, the operation of the resonance suppression device in the present embodiment will be described.

The resonance detection unit 16 Fourier-transforms the connection point voltage v using an FFT (Fast Fourier Transform) algorithm or the like, detects resonance from the peak of the obtained frequency spectrum, and obtains the resonance frequency f1. Further, the coefficient setting unit 17 sets the coefficient L of the integral filter 11 or the coefficients R and L of the first-order lag filter 11 based on the resonance frequency f1. The filter 11 outputs a current command value i ^* corresponding to the set filter coefficient. The relationship between the coefficient of the filter 11 and the resonance suppression effect by the resonance suppression device 1a will be described later.

The current control unit 13 outputs a voltage command value v ^* corresponding to the difference (i ^* −i) between the current command value i ^* and the output current i of the parallel inverter 14. The parallel inverter 14 performs PWM (Pulse Width Modulation) control and PAM (Pulse Amplitude Modulation) control based on the voltage command value v ^* , and converts the power of the DC power supply 15 to AC power. It converts and outputs alternating current i. Thereby, the current control unit 13 controls the parallel inverter 14 so that the output current i of the parallel inverter 14 follows the current command value i ^* , and the parallel inverter 14 follows the current command value i ^*. Is supplied to the power system 5.

=== Operation of Resonance Suppressor ===
Next, with reference to FIG. 2 to FIG. 10 as appropriate, the operation of the resonance suppression apparatus in the present embodiment to suppress resonance will be described.

となる。FIG. 2 shows an equivalent circuit of the wind power generator 3 in a state where the resonance suppression device 1a is not installed, and the wind power generator 3 can be regarded as a (harmonic) current source. At this time, the resonance frequency fr1 due to the capacitance C1 and the transformer inductance L1 is

It becomes.

  Here, since the capacitance of the harmonic filter included in each wind power generator is connected in parallel according to the number of connected wind power generators, the combined capacitance C1 increases as the number of connected wind power generators increases, and the resonance frequency fr1 becomes higher. descend. When the resonance frequency fr1 is sufficiently high and is in a high frequency region (for example, about several kHz), although resonance does not occur, the number of connected units increases and the resonance frequency fr1 is low to some extent (for example, about several hundred Hz). ), Resonance may occur depending on the number of connected units (resonance frequency fr1).

となる。ここで、Ｌ１’は、積分フィルタまたは一次遅れフィルタのインダクタンスＬと変圧器インダクタンスＬ１との合成インダクタンスであり、

となるため、ｆｒ２＞ｆｒ１となる。3 and 4 show a state in which an integral filter and a first-order lag filter are connected in parallel with the (combined) capacitance C1 of the harmonic filter, respectively. The resonance frequency fr2 in these cases is

It becomes. Here, L1 ′ is a combined inductance of the inductance L of the integral filter or the first-order lag filter and the transformer inductance L1,

Therefore, fr2> fr1.

  Therefore, when the resonance detector 16 detects resonance of the harmonic filter (resonance frequency f1), if an integral filter or a first-order lag filter is connected in parallel with the capacitance C1, for example, as shown in FIG. 5, the resonance frequency f1 Can be moved to a higher frequency side. Then, by setting the filter coefficient L so that the resonance frequency f2 after the movement is sufficiently higher than the original resonance frequency f1, it is possible to reduce the gain at the resonance frequency f1 and suppress the resonance. For example, in FIG. 5, as the resonance frequency moves (increases) from f1 to f2, the gain at the resonance frequency f1 decreases from g1 to g2. Preferably, the gain g2 at the original resonance frequency f1 when the resonance frequency is moved to f2 is set to a sufficiently small predetermined value or less, so that the resonance frequency f2 after the movement is at least twice the original resonance frequency f1. The filter coefficient is set as follows. More preferably, the filter coefficient is set so that the resonance frequency f2 after the movement is about 2 to 3.5 times the original resonance frequency f1.

と表され、これをラプラス変換すると、

となる。ここで、積分フィルタの伝達関数をＨ１とすると、

となるため、共振抑制装置１ａが積分フィルタ１１の出力（電流指令値ｉ^＊）に追従する交流電流ｉを電力系統５に供給することは、図３のように積分フィルタを接続するのと等価である。By the way, in FIG.

And when this is Laplace transformed,

It becomes. Here, when the transfer function of the integral filter is H1,

Therefore, supplying the alternating current i that follows the output (current command value i ^* ) of the integration filter 11 to the power system 5 by the resonance suppression device 1a is equivalent to connecting the integration filter as shown in FIG. It is.

  Therefore, resonance can be suppressed by moving the detected resonance frequency to the high frequency side by the resonance suppression device 1 a including the integration filter 11. As an example, FIG. 6 shows a state in which resonance occurs and a resonance frequency component is superimposed on the connection point voltage v and the supply current i2 (= i1) to the power system 5, and FIG. A state in which the resonance is suppressed by the provided resonance suppression device 1a is shown. As shown in FIGS. 6 and 7, the resonance is suppressed by the resonance suppression device 1a including the integration filter 11, and the waveform of the voltage v at the top of FIG. 6 is improved as shown at the top of FIG. An example of the relationship between the coefficient L of the integral filter 11 and the resonance suppression effect is shown in FIG. As shown in FIG. 8, although the resonance suppression effect increases as the inductance L decreases, the output current i of the parallel inverter 14 increases from the equation (6), and it is necessary to use a larger one as the parallel inverter 14. There is.

と表され、これをラプラス変換すると、

となる。ここで、一次遅れフィルタの伝達関数をＨ２とすると、

となるため、共振抑制装置１ａが一次遅れフィルタ１１の出力（電流指令値ｉ^＊）に追従する交流電流ｉを電力系統５に供給することは、図４のように一次遅れフィルタを接続するのと等価である。On the other hand, in FIG.

And when this is Laplace transformed,

It becomes. Here, when the transfer function of the first-order lag filter is H2,

Therefore, supplying the alternating current i that follows the output (current command value i ^* ) of the first-order lag filter 11 to the power system 5 by the resonance suppression device 1a connects the first-order lag filter as shown in FIG. Is equivalent to

  Therefore, resonance can be suppressed by moving the detected resonance frequency to the high frequency side by the resonance suppression device 1a including the first-order lag filter 11. As an example, FIG. 9 illustrates a state in which the resonance illustrated in FIG. 6 is suppressed by the resonance suppression device 1 a including the first-order lag filter 11. As shown in FIGS. 6 and 9, the resonance is suppressed by the resonance suppression device 1a including the first-order lag filter 11, and the waveform of the voltage v at the top of FIG. 6 is improved as shown at the top of FIG. FIG. 10 shows an example of the relationship between the coefficients R and L of the first-order lag filter 11 and the resonance suppression effect. As shown in FIG. 10, by using a first-order lag filter as the filter 11, although there is power consumption due to the resistance R, the resonance suppression effect is greater than that of the integral filter.

Second Embodiment
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the second embodiment of the present invention will be described with reference to FIG.

  The resonance suppression device 1b shown in FIG. 11 includes a coefficient setting unit 18 instead of the resonance detection unit 16 and the coefficient setting unit 17 with respect to the resonance suppression device 1a of the first embodiment. . In the present embodiment, the filter 11 and the coefficient setting unit 18 correspond to the current command value generation unit 10. Then, the coefficient setting unit 18 obtains the current connected number G # of wind power generators online, and based on the connected number G #, the coefficient L of the integral filter 11 or the coefficient R, Set L.

と表すことができる。Here, as shown in FIG. 12, when n wind power generators 3 are connected to the power system 5, resonance is caused by the capacitance C1 of each harmonic filter 31, the system inductance L2, and each transformer inductance L1. The frequency fr1 is

It can be expressed as.

  Therefore, from the relationship between the number of connected wind power generators G # = n and the resonance frequency fr1, the coefficient setting unit 18 determines the current resonance frequency fr1 based on the current number of connections G # acquired online. Can be sought. Then, the coefficient setting unit 18 filters the current resonance frequency fr1 so that the resonance frequency fr2 when the integral filter or the first-order lag filter is connected in parallel with the capacitance C1 of each harmonic filter 31 is sufficiently high. 11 coefficients are set. Preferably, the coefficient of the filter 11 is set so that the resonance frequency fr2 is at least twice the resonance frequency fr1. More preferably, the coefficient of the filter 11 is set so that the resonance frequency fr2 is about 2 to 3.5 times the resonance frequency fr1.

Here, since the resonance suppression device 1b of the present embodiment does not include the resonance detection unit, the resonance suppression device 1b follows the output (current command value i ^* ) of the filter 11 regardless of whether or not resonance actually occurs. An alternating current i is supplied to the power system 5. Therefore, the resonance suppression apparatus 1b can determine the resonance frequency fr1 when it is assumed that resonance has occurred, and can move the resonance frequency fr1 to fr2 to suppress the resonance. Instead of obtaining the resonance frequency fr1 each time based on the connected number G # of wind power generators, a coefficient setting table in which the connected number G # is associated with the coefficient of the filter 11 to be set is created in advance. The coefficient of the filter 11 may be set with reference to this.

<Third Embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the third embodiment of the present invention will be described with reference to FIG.

A resonance suppression device 1c shown in FIG. 13 includes a switch 19 in place of the coefficient setting unit 17 with respect to the resonance suppression device 1a of the first embodiment. In the present embodiment, the filter 11 corresponds to the current command value generation unit 10. When the resonance detector 16 detects resonance, the switch 19 inputs the output of the filter 11 as a current command value i ^* to the adder 12, and when the resonance detector 16 does not detect resonance, The current command value i ^* = 0 is input to the adding unit 12. Thereby, the alternating current i is supplied from the parallel inverter 14 to the power system 5 only when the resonance detection unit 16 detects resonance.

  Here, since the resonance suppression device 1c of the present embodiment does not include a coefficient setting unit, the coefficient of the filter 11 is a fixed value set in advance. For example, the resonance frequency fr1 in a state where all the wind power generators of the wind power plant are connected to the power system 5 is obtained, and the resonance frequency fr1 is moved to a high-frequency region having a small influence (no resonance occurs). The coefficient of the filter 11 is set. In this case, the coefficient of the filter 11 is set on the basis of the case where the resonance frequency fr1 is the lowest, and the resonance suppression device 1c can suppress resonance regardless of the number of connected wind power generators. In the present embodiment, since the coefficient of the filter 11 is a fixed value, the filter 11 may be configured as an analog filter.

<Fourth embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the fourth embodiment of the present invention will be described with reference to FIG.

  The resonance suppression device 1d shown in FIG. 14 is a combination of the resonance suppression device 1b of the second embodiment and the resonance suppression device 1c of the third embodiment. The apparatus further includes a resonance detection unit 16 and a switch 19 of the device 1c. In the present embodiment, the filter 11 and the coefficient setting unit 18 correspond to the current command value generation unit 10. Therefore, in the resonance suppression device 1b of the second embodiment, the alternating current i is always supplied to the power system 5 regardless of the presence or absence of resonance, whereas the resonance suppression device 1d of the present embodiment actually The alternating current i can be supplied to the power system 5 only when resonance occurs.

<Fifth Embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression apparatus according to the fifth embodiment of the present invention will be described with reference to FIG.

A resonance suppression device 1e shown in FIG. 15 includes a filter 11, an adder 12, a current controller 13, a parallel inverter 14, and a DC power supply 15. In the present embodiment, the filter 11 corresponds to the current command value generation unit 10. Then, similarly to the resonance suppression device 1b of the second embodiment, the resonance suppression device 1e is an alternating current that follows the output (current command value i ^* ) of the filter 11 regardless of whether or not resonance actually occurs. The current i is supplied to the power system 5. Similarly to the third embodiment, the coefficient of the filter 11 is set based on, for example, the case where the resonance frequency fr1 is the lowest, and the resonance suppression device 1c suppresses the resonance regardless of the number of connected wind power generators. be able to.

<Sixth Embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the sixth embodiment of the present invention will be described with reference to FIG.

In the said 1st thru | or 5th embodiment, the alternating current i which follows the output (current command value i ^* ) of the filter 11 (current command value generation part 10) is output from the parallel inverter 14, and wind power generation is carried out to the electric power grid | system 5. It is supplied in parallel with the machine 3. On the other hand, in this embodiment, when a power conversion device capable of outputting an alternating current i is connected to the power system, a resonance current is output by outputting a current command value i ^* to the power conversion device. Suppress.

  The resonance suppression device 1f shown in FIG. 16 corresponds to the filter (11) and coefficient setting unit (17, 18) in the first, second, and fourth embodiments, and the filter (11) in the third and fifth embodiments. It is comprised including the electric current command value production | generation part 10 to perform. Note that the resonance suppression device 1f may include the resonance detection unit (16) in the first, third, and fourth embodiments as appropriate.

The current command value generation unit 10 is input with the voltage of the power system 5 (the connection point voltage between the wind power generator 3 and the power system 5) v. Then, the current command value generation unit 10 generates a current command value i ^* and outputs it to the power conversion device 7 connected to the power system 5. Thereby, the alternating current i is supplied from the power converter device 7 to the electric power system 5, and the resonance can be suppressed by moving the resonance frequency to the high frequency side as in the first to fifth embodiments. As a power converter capable of outputting such an alternating current i, for example, a reactive power compensator can be used in addition to an inverter and a UPFC.

<Seventh embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the seventh embodiment of the present invention will be described with reference to FIG.

In the first to sixth embodiments, the output (current command value i) of the current command value generation unit 10 is equivalent to connecting an integral filter or a first-order lag filter in parallel with the capacitance C1 of the harmonic filter 31. ^* ) An alternating current i following the above is supplied to the power system 5. On the other hand, in this embodiment, as shown in FIG. 3 or FIG. 4, a resonance corresponding to an integral filter or a first-order lag filter is actually connected in parallel with the capacitance C 1 of the harmonic filter 31. Suppress.

  The resonance suppression device 2a illustrated in FIG. 17 includes a reactor group 21, a switch circuit 22, a resonance detection unit 26, and a reactor selection unit 27.

Reactor group 21 includes a plurality of reactors having different coefficients. Further, as an example, the coefficient (inductance) of each reactor is sequentially reduced by a factor of 1/2, such as L0, L0 / 2,..., L0 / 2 ^n-1 .

  Similar to the resonance detector 16 of the resonance suppression device 1a, the resonance detector 26 performs Fourier transform on the connection point voltage v to detect resonance and obtain the resonance frequency f1. Then, the reactor selection unit 27 selects one reactor from the reactor group 21 based on the resonance frequency f1, and the switch circuit 22 sets the selected one reactor in parallel with the capacitance C1 of the harmonic filter 31. Connecting. Alternatively, the reactor selection unit 27 may select two or more reactors from the reactor group 21, and the combined reactor (synthetic inductance) may be connected in parallel with the capacitance C1.

For example, if the reactor group 21 includes three reactors and their inductances are L0, L0 / 2, and L0 / 4, by selecting two reactors of the inductances L0 and L0 / 2, the combined inductance is L0 / 3 Similarly, by selecting two reactors of inductances L0 and L0 / 4, the combined inductance is L0 / 5, and by selecting two reactors of inductances L0 / 2 and L0 / 4, the combined inductance is L0 / 6. Further, by selecting all three reactors, the combined inductance becomes L0 / 7, so that L0, L0 / 2, L0 / 3, L0 / 4, L0 / 5, L0 / 6, and L0 / 7 are 7 The selected inductance can be selected. More generally, reactor group 21 is an inductance L0, L0 / 2, ..., L0 / 2 if made of ^n-1 of n reactors, L0 ^/ 1~L0 / the ^{(2 n -1) (2 n} - 1) Inductance can be selected.

  Accordingly, since the resonance frequency f1 can be moved to a higher frequency side, the gain at the resonance frequency f1 is selected by selecting the reactor (one or more) so that the resonance frequency f2 after the movement becomes sufficiently high. The resonance can be suppressed by reducing the value. Preferably, in order to set the gain at the original resonance frequency f1 when the resonance frequency is moved to f2 to a sufficiently small predetermined value or less, the moved resonance frequency f2 is at least twice or more than the original resonance frequency f1. Select the reactor. Note that, by selecting all the reactors in the reactor group 21, the gain at the original resonance frequency f1 is minimized, but the current flowing through those reactors is increased. Therefore, more preferably, the reactor is selected such that the resonance frequency f2 after movement is about 2 to 3.5 times the original resonance frequency f1.

<Eighth Embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the eighth embodiment of the present invention will be described with reference to FIG.

  The resonance suppression device 2b shown in FIG. 18 includes a reactor selection unit 28 instead of the resonance detection unit 26 and the reactor selection unit 27 with respect to the resonance suppression device 2a of the seventh embodiment. . And the reactor selection part 28 acquires the connection number G # of the present wind power generator online, and selects one or more reactors from the reactor group 21 based on this connection number G #.

  Here, similarly to the coefficient setting unit 18 of the resonance suppression device 1b, the reactor selection unit 28 can obtain the current resonance frequency fr1 based on the current number of connected units G # acquired online. Then, by selecting the reactor (one or more) from the reactor group 21 such that the resonance frequency fr2 when connected in parallel with the capacitance C1 of the harmonic filter 31 is sufficiently high, the gain at the resonance frequency f1 is increased. The resonance can be suppressed by reducing the size. Preferably, the reactor is selected so that the resonance frequency fr2 is at least twice or more than the resonance frequency fr1. More preferably, the reactor is selected so that the resonance frequency fr2 is about 2 to 3.5 times the resonance frequency fr1.

<Ninth Embodiment>
=== Configuration and Operation of Resonance Suppressor ===
Hereinafter, the configuration and operation of the resonance suppression device according to the ninth embodiment of the present invention will be described with reference to FIG.

  The resonance suppression device 2c shown in FIG. 19 is configured to further include a resonance detection unit 26 with respect to the resonance suppression device 2b of the eighth embodiment. The switch circuit 22 connects the reactor (one or more) selected by the reactor selection unit 28 in parallel with the capacitance C1 of the harmonic filter 31 only when the resonance detection unit 26 detects resonance. Therefore, in the resonance suppression device 2b of the eighth embodiment, the resonance frequency is always moved regardless of the presence or absence of resonance, whereas in the resonance suppression device 2c of the present embodiment, resonance actually occurs. The resonance frequency can be moved to the high frequency side only when it is present.

As described above, in the resonance suppression device 1 f, the voltage v of the power system 5 is input to the current command value generation unit 10, and the generated current command value i ^* is supplied to the power conversion device 7 connected to the power system 5. By outputting, the alternating current i is supplied from the power converter 7 to the power system 5, and the resonance frequency can be moved to the high frequency side to suppress the resonance.

Further, as described above, in the resonance suppression devices 1a to 1e, the connection point voltage v between the wind power generator 3 and the power system 5 is input to the current command value generation unit 10, and the output (current) of the current command value generation unit 10 is obtained. The AC current i following the command value i ^* ) is output from the parallel inverter 14 and supplied to the power system 5 in parallel with the wind power generator 3, thereby changing the number of connected wind power generators to the power system. Even when the resonance point changes, the resonance can be suppressed by moving the resonance frequency to the high frequency side.

Further, in the resonance suppression device 1a, the connection point voltage v is Fourier transformed to detect the resonance and obtain the resonance frequency f1, and the coefficient L of the integration filter 11 so that the gain at the resonance frequency f1 is a predetermined value or less. Alternatively, by setting the coefficients R and L of the first-order lag filter 11 and generating the current command value i ^* , the detected resonance frequency can be moved to the high frequency side to suppress resonance.

Further, in the resonance suppression device 1b, the current number of connected wind turbine generators G # is acquired, the coefficient of the filter 11 is set based on the number of connected wind turbines G #, and the current command value i ^* is generated, thereby causing resonance. It is possible to obtain the resonance frequency fr1 when it is assumed that is generated, and to move the resonance frequency fr1 to fr2 to suppress the resonance.

  In the resonance suppression device 1c, the coefficient of the filter 11 is set as a fixed value in advance, and the resonance frequency is set by supplying the alternating current i from the parallel inverter 14 to the power system 5 only when resonance is detected. The resonance can be suppressed regardless of the number of connected wind power generators by moving to a high frequency region.

  Further, as described above, in the resonance suppression devices 2a to 2c, one or more reactors are selected from the reactor group 21 including a plurality of reactors having different coefficients, and are actually parallel to the capacitance C1 of the harmonic filter 31. By connecting, even if the number of connected wind power generators to the power system changes and the resonance point changes, the resonance frequency can be moved to the high frequency side to suppress resonance.

  Further, in the resonance suppression apparatus 2a, the connection point voltage v is Fourier transformed to detect the resonance and obtain the resonance frequency f1, and based on the resonance frequency f1, select one or more reactors from the reactor group 21. By doing so, the resonance can be suppressed by moving the detected resonance frequency to the high frequency side.

  Further, in the resonance suppression device 2b, when the current number of connected wind turbine generators G # is acquired, and (one or more) reactors are selected based on the number of connected G #, resonance has occurred. The assumed resonance frequency fr1 can be obtained, and the resonance frequency fr1 can be moved to fr2 to suppress resonance.

  Further, in the resonance suppression device 2c, only when the resonance is detected, the resonance is actually generated by connecting the selected reactor (s) in parallel with the capacitance C1 of the harmonic filter 31. Only in this case, the resonance can be suppressed by moving the resonance frequency to the high frequency side.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In the above embodiment, the resonance generated by the harmonic filter 31 of the wind power generator 3 being connected to the power system 5 is suppressed, but the present invention is not limited to this. The resonance suppression device of the above embodiment can be regarded as a (harmonic) current source connected to the power system in the same manner as the wind power generator, and includes a harmonic filter including a capacitance for removing the harmonic current. It can also be applied to other electric power facilities provided. For example, the present invention can be applied to other power generation facilities such as solar power generation, geothermal power generation, and wave power generation. Furthermore, the present invention can be widely applied not only to a power generation facility but also to a case where power equipment connected to a power system includes a harmonic filter.

  Moreover, in the said embodiment, although the harmonic filter 31 is an alternating current filter (AC filter), for example, it is not limited to this, A reactor and a capacitance (for example, power capacitor) are used for the connection to the electric power system 5. What is necessary is just the structure provided.

DESCRIPTION OF SYMBOLS 1a-1f, 2a-2c Resonance suppression apparatus 3 Wind power generator 5 Power system 7 Power converter 10 Current command value production | generation part 11 Filter 12 Addition part 13 Current control part 14 Parallel inverter 15 DC power supply 16, 26 Resonance detection part 17, 18 Coefficient setting unit 19 Switch 21 Reactor group 22 Switch circuit 27, 28 Reactor selection unit 31 Harmonic filter

Claims (5)

A resonance suppression device that suppresses resonance that occurs when a power device including a harmonic filter is connected to a power system,
An inverter that supplies an alternating current in parallel with the power device to the power system;
A voltage at a connection point between the power device and the power system is input, and a current command value generation unit that generates a current command value that moves a resonance frequency of the harmonic filter to a high frequency side,
A current controller for controlling the alternating current output from the inverter based on the current command value;
I have a,
The said current command value production | generation part produces | generates the said current command value based on the number of the said electric power devices connected to the said electric power grid | system, The resonance suppression apparatus characterized by the above-mentioned . The resonance suppression device according to claim 1 ,
A resonance detector for detecting the resonance;
The resonance suppression apparatus, wherein the alternating current is supplied from the inverter to the power system only when the resonance detection unit detects the resonance. A resonance suppression device that suppresses resonance that occurs when a power device including a harmonic filter is connected to a power system,
A plurality of reactors having different coefficients,
A reactor selection unit that selects one or more reactors from the plurality of reactors;
A switch circuit for connecting the one or more reactors selected by the reactor selection unit among the plurality of reactors in parallel with a capacitance of the harmonic filter;
Have
The said reactor selection part selects the said 1 or more reactor from these reactors based on the number of the said electric power devices connected to the said electric power grid | system, The resonance suppression apparatus characterized by the above-mentioned. The resonance suppression device according to claim 3 ,
A resonance detector for detecting the resonance;
The switch circuit connects the one or more reactors selected by the reactor selection unit in parallel with the capacitance of the harmonic filter only when the resonance detection unit detects the resonance. Resonance suppression device. The resonance suppression device according to any one of claims 1 to 4 ,
The power suppression device is a wind power generator.

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