JP4239088B2 - Wind power generation equipment - Google Patents

Description

  The present invention relates to a wind power generation facility including a winding induction machine connected to a wind turbine, a converter for performing secondary excitation thereof, and a capacitor for removing harmonic current, and in particular, paralleling by the inductance of the capacitor and the interconnection system. The present invention relates to a wind power generation facility capable of suppressing resonance.

FIG. 3 shows the prior art of this type of wind power generation facility interconnected to a higher power system. This configuration is described in FIG. 5 of Non-Patent Document 1 described later.
In FIG. 3, 10 is a windmill, 20 is a gear box, 30 is a winding induction machine, 40 is an interconnection transformer, 50 is a converter as a secondary excitation device (frequency conversion device), 51 is a forward conversion unit (converter unit) ), 52 is a reverse conversion unit (inverter unit), 53 is a DC link capacitor, 61 is a filter capacitor (for removing harmonic current), 62 is a reactor, 100 is a power system, and 101 is a lead-in cable. Yes.

  In the above configuration, the primary winding (stator winding) of the induction machine 30 is connected to the power system 100 via the lead-in cable 101 and the interconnection transformer 40, and the secondary winding (rotor) of the induction machine 30. Winding) is connected to the reverse conversion part 52 of the converter 50 via a slip ring.

4 is a control block diagram described in FIG. 9 of Non-Patent Document 1 as an example of the control circuit of the converter 50.
In FIG. 4, the current I _N and voltage V _S on the primary side of the induction machine 30 detected by the current detector 501 and the voltage detector 502 are input to the power calculator 503, and the active power P and the reactive power Q are detected. . The power regulators 504 and 505 perform an adjustment operation so that each deviation between the command values P ^* and Q ^* of each power and the detected values P and Q becomes zero, and these outputs are input to the current control circuit 506. .

Current I _R of the current detector 507 induction machine 30 detected by the secondary winding 32, d-axis by a three-phase / two-phase converter 508, is broken down into q-axis component, each of these components I _Rd, I _Rq is input to the current control circuit 506. Similarly, d-axis component by the current I _S is a three-phase / two-phase converter 509 of the primary winding 31 of the induction machine 30 detected by the current detector 511 is decomposed into q-axis component, each of these components I _Sd , I _Sq are also input to the current control circuit 506.
The current control circuit 506 calculates and outputs the d-axis voltage command V _Rd and the q-axis voltage command V _Rq based on the outputs of the regulators 504 and 505 and the above I _Rd , I _Rq , I _Sd , and I _Sq .

Further, the voltage V _S of the primary winding 31 of the induction machine 30 to the angle calculator 510 is inputted, the angle phi _VS of the voltage vector calculated by the angle calculator 510, the induction machine 30 of the rotor A difference (φ _VS −φ _R ) from the detection angle φ _R by the position detector 512 is input to the three-phase / two-phase converter 508 and the two-phase / three-phase converter 513. The angle φ _VS is also input to the three-phase / two-phase converter 509.

The two-phase / three-phase converter 513 generates a three-phase voltage command V _R ^* based on the voltage commands V _Rd and V _Rq and the angle (φ _VS −φ _R ) of each axis, and outputs it to the PWM circuit 514. To do. The PWM circuit 514 generates a PWM pulse for the inverse conversion unit 52 by comparing the voltage command V _R ^* with the carrier, drives a switching element such as an IGBT, and supplies a predetermined frequency to the secondary winding 32 of the induction machine 30. And an alternating voltage having a magnitude is supplied.

Further, the DC link voltage _VDC of the converter 50 detected by the voltage detector 516 is input to the PWM circuit 517 on the forward conversion unit 51 side. Further, the alternating current I _GC of the forward conversion unit 51 detected by the current detector 515 is input to the PWM circuit 517 together with the voltages V _S and V _DC . The PWM circuit 517 generates a PWM pulse based on the voltages V _S and V _DC and the current I _GC and drives the switching element of the forward conversion unit 51 to control the DC link voltage V _DC to a predetermined value.

  In this wind power generation facility, the known secondary excitation control causes the rotor speed to fluctuate due to fluctuations in wind speed, wind direction, etc., so that the output always matches the command value even when the output of the induction machine 30 fluctuates. Since the operation of controlling the secondary voltage of the induction machine 30, that is, the rotor speed, is performed, the speed fluctuation of the rotor can be suppressed and the stable operation can be continued.

S. Muller, M. Deicke, Rik W. De Doncker, “Doubly fed induction generator systems for Wind turbines”, Industry Applications Magazine, IEEE, Volume: 8 Issue: 3, May-June 2002, p.26-p.32

Now, it is known that when the forward conversion unit 51 and the reverse conversion unit 52 constituting the converter 50 are controlled by PWM (pulse width modulation), a harmonic current corresponding to the carrier frequency is generated. In the technology, a filter capacitor 61 is provided to remove the harmonic current.
On the other hand, this type of wind power generation equipment is configured on the assumption that it is connected to a power source that is relatively resistant to noise and voltage fluctuations (a power source having a short distribution line length). Only removing the harmonic current from 50 need be considered.

  However, when the wind power generation facility is connected to a relatively weak power source (a power source having a long distribution line length), the harmonic current removing capacitor 61 and the system inductance (including the leakage inductance of the interconnection transformer 40) It is necessary to consider the parallel resonance phenomenon due to the above, and the system voltage is likely to be oscillated at the resonance frequency.

Here, FIG. 5 shows an equivalent circuit when the conventional wind power generation facility is linked to a relatively weak power source.
In FIG. 5, E is the voltage of the upper system 100 (infinite bus) expressed by a voltage source, r ₁ , L ₁ , C ₁ are the resistance, inductance, capacitance, r ₂ , L of the distribution line of the upper system 100. _{2, C 2} is the resistance of the drop cable 101, inductance, _{capacitance, L TR} is the leakage inductance of interconnection transformer 40, _{C h} is the capacitance of the harmonic current eliminating capacitor 61, G is represented by a current source An induction machine 30 is shown.
As is apparent from FIG. 5, the capacitance _{C h} of the capacitor 61 constitute a parallel resonance circuit with the series circuit of the inductance _{L 1, L 2, L TR} .

Now, when fluctuations in the load connected to the system and disturbance due to stop / start of other wind power generation facilities occur, voltage oscillation due to the resonance frequency of the parallel resonance circuit is excited.
As a result, as shown in FIG. 6 (a), there is a possibility that the oscillation voltage of the resonance frequency is superimposed on the fundamental wave voltage output from the induction machine 30, and the operation becomes unstable. In the worst case, the frequency relay There was a problem that the operation of the wind power generation equipment would be stopped due to the operation of the protective equipment. In FIG. 6A, the horizontal axis represents time, and the vertical axis represents voltage amplitude expressed in the unit method.
Furthermore, the above-described voltage oscillation has a problem in that various adverse effects are caused on the devices connected to the system 100.

  Here, FIG. 6B shows the magnitude (upper stage) and phase angle (lower stage) of the impedance viewed from the induction machine 30 of the wind power generation facility, and the horizontal axis is the frequency. From this figure, the impedance around 1.3 [kHz] is large, parallel resonance occurs due to the above-mentioned disturbance, and voltage oscillation at the resonance frequency (about 1.3 [kHz]) is excited. I understand.

  Therefore, the present invention aims to provide a wind power generation facility that can suppress the instability of the output voltage due to the parallel resonance phenomenon caused by the harmonic current removing capacitor and enables stable operation.

In order to solve the above-mentioned problem, the invention described in claim 1 is a winding induction machine that is driven by a windmill and supplies generated power to the interconnection system, and a converter that performs secondary excitation of the winding induction machine. In a wind power generation facility equipped with a capacitor for removing harmonic current generated by the operation of this converter,
In order to suppress parallel resonance by the capacitor and the system inductance, a resistor having a value R _h given by the following equation, which are connected in series with said capacitor.
R _h = 2ζ√ (X ₀ / Y ₀ )
(Where X ₀ is the system reactance [pu] as seen from the induction machine at the fundamental wave frequency of the output voltage of the wind power generation facility, Y ₀ is the susceptance [pu] of the capacitor at the fundamental wave frequency, and ζ is the attenuation coefficient)

  The invention described in claim 2 is the wind power generation facility described in claim 1, wherein the attenuation coefficient ζ is about 0.01 to about 0.03.

  According to the present invention, the parallel resonance caused by the capacitor and the system inductance is suppressed by the resistor connected in series with the harmonic current absorbing capacitor, and the resonance frequency component is superimposed on the output voltage of the wind power generation facility. Absent. Thereby, stable operation can be continued without stopping the wind power generation facility, and adverse effects on the devices connected to the system can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an equivalent circuit diagram of a wind power generation facility according to the present invention linked to a power source that is relatively weak against noise and voltage fluctuations. Note that the same components as those in FIG. 5 are denoted by the same reference numerals, description thereof is omitted, and different portions will be mainly described below.

As is apparent from a comparison between FIG. 1 and FIG. 5, in this embodiment, a resistor R _h (the resistance value is also represented by R _h ) is connected in series with the harmonic current removing capacitor 61. For example, a control circuit as shown in FIG. 4 is used as the control circuit of the wind power generation facility.

By adding the resistor R _h as shown in FIG. 1, even when the disturbance of the stop-start such a load variation or other wind turbines occurs, inductance and capacitance C _h of the capacitor 61 L _1, L ₂ parallel resonance phenomenon due to a series circuit of L _TR is suppressed, there is no possibility that the voltage of the resonance frequency to the voltage of the fundamental frequency output from the induction motor 30 is superimposed. For this reason, there is no possibility that the protection device such as the frequency relay operates and the operation of the wind power generation facility is stopped, and the stable operation can be continued.

FIG. 2A shows an output voltage waveform of the wind power generation facility (induction machine 30). Like FIG. 6A, the horizontal axis represents time, and the vertical axis represents the voltage amplitude expressed in the unit method. FIG. 2B shows the magnitude (upper stage) and phase angle (lower stage) of the impedance viewed from the induction machine 30 as in FIG. 6B, and the horizontal axis is the frequency.
2 from (a), in parallel resonance phenomenon suppressed by the addition of resistor R _h, with the output voltage waveform is substantially made only to the fundamental wave component, from FIG. 2 (b), about equivalent to the resonance frequency It can be seen that impedance fluctuations at 1.3 [kHz] are also suppressed.

Here, the resistance R _h connected in series to the harmonic current removing capacitor 61 is desirably a value R _h given by the following Equation 1.
[Formula 1]
R _h = 2ζ√ (X ₀ / Y ₀ )
In Formula 1, X ₀ is the system reactance [pu] viewed from the induction machine 30 at the fundamental frequency of the output voltage of the wind power generation facility, and Y ₀ is the susceptance [pu of the harmonic current removing capacitor 61 at the fundamental frequency. ] And ζ are damping coefficients (about 0.01 to about 0.03).

Hereinafter, a method for deriving Equation 1 will be described.
In FIG. 1, the primary winding current of the induction machine 30 is I _G , the terminal voltage is V _f , the resistors r ₁ and r ₂ and the capacitances C ₁ and C ₂ are ignored, and the inductances L ₁ , L ₂ , L _When the combined value of _TR (inductance of the system viewed from the induction machine 30) is L, Expression 2 is established.
[Formula 2]
^{_{V f / I G = (R}} h s 2 + s / C h) / [s 2 + s (R h / L) + (1 / LC h)]
Note that s is a Laplace operator.

Here, considering the characteristic equation of the secondary vibration system, when R _h / L = 2ζω _n and 1 / LC _h = ω _n ² in Equation ² , Equation 3 is obtained, and X ₀ = ω ₀ L , Y ₀ = ω _{0 Ch} , the above formula 1 is obtained.
[Formula 3]
_{R h = 2ζ√ (L / C} h) = 2ζ√ (ω 0 L / ω 0 C h)
Note that ω _n is an undamped natural frequency (or simply natural frequency), and the natural frequency ω _n and the damping coefficient ζ are well known as parameters for determining the transient response characteristics of the secondary vibration system. Yes.

  As described above, the present invention is particularly suitable for a wind power generation facility in which parallel resonance due to system inductance and a harmonic current removing capacitor is a problem, such as a wind power generation facility interconnected at the system end of a long-distance distribution line. By applying it, it is possible to avoid the stop and continue stable operation.

It is an equivalent circuit diagram showing an embodiment of the present invention. It is a characteristic view of the embodiment of the present invention. It is a block diagram which shows a prior art. It is a control block diagram of a prior art. It is an equivalent circuit diagram of a prior art. It is a characteristic view of a prior art.

Explanation of symbols

10: Windmill 20: Gear box 30: Winding induction machine 40: Interconnection transformer 50: Converter 51: Forward conversion section (converter section)
52: Inverse conversion unit (inverter unit)
53: Capacitor 61: a capacitor 62: Reactor 100: Power line 101: drop cable R _h: resistance C _h: capacitance

Claims (2)

Winding induction machine driven by a windmill and supplying generated power to the interconnection system, a converter for secondary excitation of this winding induction machine, and a capacitor for removing harmonic current generated by the operation of this converter In wind power generation equipment with
In order to suppress parallel resonance due to the capacitor and system inductance, a wind power generation facility characterized in that a resistor having a value R _h given by the following equation is connected in series to the capacitor.
R _h = 2ζ√ (X ₀ / Y ₀ )
(Where X ₀ is the system reactance [pu] as seen from the induction machine at the fundamental wave frequency of the output voltage of the wind power generation facility, Y ₀ is the susceptance [pu] of the capacitor at the fundamental wave frequency, and ζ is the attenuation coefficient) In the wind power generation facility according to claim 1,
The wind power generation facility, wherein the attenuation coefficient ζ is about 0.01 to about 0.03.

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