JP3935057B2 - Stability analysis method of induction generator - Google Patents

Description

【００１４】
ただし、式中のω_rssは定常状態における回転子角速度、θ_sは三相地絡故障発生時のａ相固定子電流の位相角、また式中の時間ｔに付してある” ′”は三相地絡故障発生時刻をゼロと考えた場合の経過時間であることを示している。なお、他の定数を表２に示す。
【００１５】
【表２】

【００１６】
また、誘導発電機の出力トルクＴ_em及び電力Ｐ_IGは（５）、（６式）で表される。
【００１７】
【数２】

【００１８】
（１）〜（４）式を（５）式に代入し、整理すると、（７）式となる。
【００１９】
【数３】

【００２０】
２．運動方程式
上記過渡解析式（（１）〜（７）式）を用いて三相地絡故障時の回転子角速度を表現する速度方程式の導出を説明する。回転子の運動方程式は（８）式で表される。
【００２１】
【数４】

【００２２】
ただし、ω_f；故障期間中の回転子角速度、Ｔ_mech；機械的入力トルク、Ｔ_damp；制動トルクである。ここで、
【００２３】
【数５】

【００２４】
とおき、（８）式を回転子角速度ω_fについて解くと（９）式となる。
【００２５】
【数６】

【００２６】
【数７】

【００２７】
である。ここで、（２α／ω_rss）²≪１よりＺ_A≒１であり、またＬ_m≫Ｌ′ｌ_rの場合にはθ_A≒θ_B及びＡ≒Ｂが成り立つ。したがって、（９）式右辺第１項は第２項に比して十分小となり、（１０）式のように近似できる。
【００２８】
【数８】

【００２９】
（１０）式を用いることで三相地絡故障期間中の回転子の速度変化を考慮した誘導発電機の出力電力を表現できる。（１０）式を用いると故障期間中の誘導発電機の出力電力は（１１）式のように書き直される。
【００３０】
【数９】

【００３１】
（１０）、（１１）式の妥当性を数値計算プログラムを用いたシミュレーシン結果と比較することで検証する。数値計算プログラムにおけるシミュレーシンモデルは誘導発電機の非線形性を考慮したシステム方程式を用いて構成されている。
図３（ａ）及び（ｂ）に回転子角速度及び出力電力の解析式による計算結果（実線）及び数値計算プログラムを用いたシミュレーション結果（点線）を示す。ただし、図３は誘導発電機が定常運転中、送電線路中央で三相地絡故障が発生（ｔ_f＝４．０ｓｅｃ）した場合のシミュレーション結果である。
【００３２】
図３より、解析式による計算結果は数値計算プログラムを用いたシミュレーション結果によく一致おり、解析式の妥当性が確認できる。図３において数値計算プログラムを用いたシミュレーション結果で地絡故障直後の回転子角速度に振動がみられるが、これは（９）式右辺第一項に示す成分である。また、出力電力のシミュレーション結果に関する誤差は、解析式を導出する際に用いた近似の影響により（１１）式中の係数Ｚの値に誤差が生じたためである。
３．等面積法による誘導発電機の安定性解析
誘導発電機の出力特性表示に通常よく用いられる出力電力−すべり特性を（１０）式を用いて時間領域に変換し，等面積法によって安定性解析を行うために必要な方程式の導出を行う。
３．１ 出力電力−すべり特性
誘導発電機の回転子角速度の変化に対する出力特性は（１２）式によって表される。
【００３３】
【数１０】

【００３４】
ここで、ω_eは電源電圧の角速度である。（１２）式より誘導発電機の出力電力−すべり特性は図４（ａ）のようになる。ただし、図４の特性は故障発生後の誘導発電機の出力電力をゼロと仮定した場合である。図中のｓ_fは定常状態における発電機機速度であり、ｓ_crは再閉路時の発電機速度である。ここで、発電機の損失を無視すれば図中のＡ′_acは故障期間中発電機に加えられ、回転子を加速させるエネルギーであり、Ａ′_deは再投入後発電機速度を減少させるエネルギーである。したがって、Ａ′_ac＝Ａ′_deとなるすべりｓ_crが誘導発電機の安定限界である。
３．２ 出力電力−時間特性
時間領域における誘導発電機の出力特性について説明する。（１２）式に（１０）式を代入すると、故障期間における誘導発電機の出力電力−時間特性は図４（ｂ）のようになる。ただし、図４は故障発生後の誘導発電機の出力電力をゼロと仮定した場合を表しており、実際の解析では（１１）式に示す出力を考慮した安定性解析を行う。したがって、故障期間中の発電機出力を考慮すれば図中のＡ_ac、Ａ_dcは（１３）、（１４）式によって求められる。
【００３５】
【数１１】

【００３６】
ただし、Ｐ_ssは定常状態における発電機出力電力である。等面積法では、Ａ_ac＝Ａ_dcの場合が安定限界であり、Ａ_ac＞Ａ_dcの場合は不安定、Ａ_ac＜Ａ_dcの場合が安定である。（１３）、（１４）式を用いることにより、Ａ_ac＝Ａ_dcにより得られる安定限界時間ｔ′_crを計算できる。
４．シミュレーション結果
送電線路上で三相地絡故障が生じた場合に、各機械的入力トルクに対して安定限界となる再閉路時間ｔ_crを（１３）、（１４）式とを用いて求め、その結果の妥当性を数値計算プログラムを用いたシミュレーション結果と比較することにより検証する。安定限界となる再閉路時間ｔ_crの評価は、送電線路長ｌ＝３０ｋｍ、故障発生時間ｔ_f＝４．００ｓｅｃ、故障継続時間ｔ_cont＝０．１０ｓｅｃに固定し、再投入時間のみを変化させた場合に誘導発電機が再投入後に安定な動作をするか否かで行った。図５（ａ）及び（ｂ）はその時の回転速度及び有効電力の出力波形で、図５（ａ）は再投入後誘導発電機が安定な動作を継続する場合の出力波形、図５（ｂ）は再投入後不変定な場合の出力波形である。この安定限界となる再閉路時間を臨界再閉路時間（ＣｒｉｔｉｃａｒＲｅｃｌｏｓｉｎｇＴｉｍｅ；ＣＲＴ）とし、（１５）式によって定義する。
【００３７】
【数１２】
ＣＲＴ＝ｔ_cr−ｔ_f （１５）
ここで、ｔ_f及びｔ_crはそれぞれ故障発生時間及び再閉路時間である。故障シーケンスは、誘導発電機が定常運転中送電線路上で三相地絡故障が発生（ｔ＝ｔ_f）、その後線路ブレーカを開放（ｔ＝ｔ_o）し、故障復旧後発電機を系統へ再投入（ｔ＝ｔ_cr）とした。通常、風力発電機の系統への再投入は故障除去から数分程度後であるが、等面積法を誘導発電機の安定解析へ適用することの妥当性を確認するするために発電機の再投入は故障消滅から数サイクル後とした。
【００３８】
図６（ａ）に各機械的入力トルクに対する臨界再閉路時間ＣＲＴの解析式による計算結果（実線）及び数値計算プログラムを用いたシミュレーション結果（鎖線）を表３に、また表３をプロットした結果を図６に示す。
【００３９】
【表３】

【００４０】
また、図６（ｂ）にＣＲＴの解析エラーを示す。図６より等面積法を用いた誘導発電機の安定性解析結果（実線）は数値計算プログラムによるシミュレーション結果（鎖線）で得られた機械的入力トルク−ＣＲＴの特性とよく一致していることが確認できる。
ＩＩ．実施形態
本発明の実施形態に係る等面積法による三相地絡故障時おける誘導発電機の安定性解析方法について説明する。この安定性解析は上記（１０）、（１２）〜（１４）式を用い図７の手順で行う。まず、定常状態における誘導発電機出力電力Ｐ_ssを与える共に故障発生時間ｔ_f＝０とする。そして、故障期間中の誘導発電機の回転子角速度ω_fを近似式（１０）式を用いて誘導発電機の定数から求め、次に誘導発電機の出力電力−すべり特性式（１２）式を用いて故障発生からＰ_sc＝Ｐ_ssまでの時間ｔ′_fを求める。次いで（１３）、（１４）式を用いて故障期間中に発電機に加えられ回転子を加速するエネルギーＡ_acと再閉路後に発電機速度を減少させるエネルギーＡ_deを算出し、Ａ_ac＝Ａ_deを解いて安定限界再閉路時間ｔ′_crを求める。
【００４１】
この等面積法による誘導発電機の安定性解析方法によれば、三相地絡故障時おける誘導発電機の安定度を簡単に求めることができる。この方法による誘導発電機の過渡安定度解析結果は上述したように数値計算プログラムを用いたシミュレーション結果と比較することでその妥当性が確認された。この等面積法による誘導発電機の安定性解析は三相地絡故障時における誘導発電機の安定度を評価する上で有効である。
【００４２】
【発明の効果】
以上の説明で明らかなように、本発明によれば、三相地絡故障時おける誘導発電機の安定性解析時間を短縮できる。また、等面積法に基づく安定限界式から数値積分などを必要とせずに誘導発電機の安定限界再閉路時間を算出することができる。
【図面の簡単な説明】
【図１】 対象とする誘導発電機が接続された一機無限大母線系統図。
【図２】 一機無限大母線系統三相地絡故障時のｑ軸等価回路図。
【図３】（ａ）は回転子速度の解析式の計算結果及びシミュレーション結果を示す回転子の角速度時間−時間特性図、（ｂ）は出力電力の解析式の計算結果及びシミュレーション結果を示す出力電力−時間特性図。
【図４】（ａ）は故障発生後の誘導発電機の出力電力をゼロと仮定した場合の出力電力−スリップ特性図、（ｂ）は故障発生後の誘導発電機の出力電力をゼロと仮定した場合の出力電力−時間特性図。
【図５】（ａ）は再投入後誘導発電機が安定な動作を継続する場合の出力波形図、（ｂ）は再投入後不変定な場合の出力波形図。
【図６】（ａ）は誘導発動機の機械的入力トルクに対するＣＲＴ（臨界再閉路時間）の解析式による計算結果及びシミュレーション結果を示す機械的入力トルク−ＣＲＴ特性図、（ｂ）はその計算結果とシミュレーション結果と差を示す機械的入力トルク−ＣＲＴ解析エラー特性図。
【図７】本発明のシステム概念図。
【符号の説明】
１…無限大母線
２…送電線路
４…かご型誘導発電機
Ｆ…三相地絡故障点
Ｐ…誘導発電機の極数
Ｐ_ss…定常状態における誘導発電機出力電力
Ｐ_IG…誘導発電機出力電力
Ｐ_sc…誘導発電機回転子角速度の変化に対する出力特性
ＣＲＴ…臨界再閉路時間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction generator stability analysis method.
[0002]
[Prior art]
In recent years, the effective use of wind energy and other natural energy has been promoted by raising awareness of environmental issues. In Japan, a private large-scale wind park (capacity 20 MW, 1 MW x 20 aircraft) was constructed in November 1999 in Sakuma-cho, Hokkaido. Wind power generation is attracting attention as an environmentally friendly energy source. Wind energy is rare among natural energies, but it is a clean energy that does not use fossil fuels. In addition, since wind energy is purely domestic energy, it is important from the viewpoint of energy security in Japan, where most of the energy resources depend on foreign countries.
[0003]
[Problems to be solved by the invention]
In general, a squirrel-cage induction generator is often used for wind power generation because it has a simple structure and is robust so that it is easy to maintain, is inexpensive, and does not require phase adjustment when the systems are parallel. However, since the induction generator does not have an excitation source, an inrush current 6 to 7 times the generator rated current flows when the system is in parallel. In addition, when a short circuit fault or a ground fault occurs when the induction generator is connected to the grid and operating, an excessive fault current flows and greatly affects the grid. In this induction generator, the rotor starts to accelerate when a short circuit fault or ground fault occurs in the system, so the generator operates stably when it is re-entered into the system in a relatively short time after the failure occurs. Maintain, but if the re-input time becomes longer, it will become unstable. Therefore, failure current analysis or transient stability analysis of induction generators has become an important issue.
[0004]
From such a background, the present inventors have so far derived analytical formulas regarding the fault current and each output of the induction generator at the time of a three-phase ground fault, and using these analytical formulas, the induction generator at the time of transition Has been analyzed (for example, see Non-Patent Document 1).
[0005]
In addition, we have been conducting transient stability analysis of synchronous generators by the equal area method. The transient stability analysis of this synchronous generator consists of generator mechanical input other than the final disturbance occurrence time input, generator internal voltage, infinite bus voltage, generator transient reactance, transformer reactance, transmission line reactance, power generation Fix all the inputs such as unit inertia constant, generator rated angular velocity, accident occurrence time, accident interruption time, etc., find the stability limit phase difference angle by the equal area method, then all the inputs including the final disturbance occurrence time The phase difference angle at the time of the final disturbance is obtained from the fluctuation equation at the time of the disturbance generation, and the stability determination is performed by comparing the stability limit phase difference angle with the phase difference angle at the time of the disturbance generation (for example, patent Reference 1).
[0006]
[Non-Patent Document 1]
Toshinobu Senju, Yoshihide Sueyoshi, Katsumi Kamisato, Hideki Fujita “Analysis of transient phenomena in induction generators during three-phase ground faults”, IEEJ Power Technology Power System Technology Joint Study Group, PE-02-16, PSE-2-26, 2002.
[0007]
[Patent Document 1]
However, these stability analysis methods are intended for synchronous generators and cannot be applied to stability analysis of induction generators.
[0008]
The present invention has been made in view of the above problems, and the stability by the equal area method that has been used for the stability analysis of the synchronous generator by using the analytical expression relating to the fault current of the induction generator and each output. The stability analysis method of the induction generator which applied the analysis to the stability analysis of the induction generator is provided.
[0009]
[Means for Solving the Problems]
The method for analyzing the stability of an induction generator according to the present invention uses the output power-time characteristics of the induction generator to reduce the energy applied to the generator during the failure period to accelerate the rotor and the generator speed after reclosing. Since the energy is calculated and the two are equal, the stability limit reclosing time is calculated.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As described in the section “Problems to be Solved by the Invention”, the operation of an induction generator is divided into a stable state and an unstable state depending on the time from the occurrence of a failure to the re-input. In other words, there is a stability limit reclosing time for the induction generator to maintain a stable operation after recharging. In the present invention, this stability limit time is defined as "critical reclosing time", and this value is obtained by the equal area method. At this time, generally known slip-output power characteristics of an induction generator are used.
I. Derivation of Analytical Formula First, the derivation of the analytical formula used for the stability analysis method of the induction generator according to the present invention will be described.
[0011]
1. Transient analysis formula for three-phase ground faults Figure 1 shows the one-machine infinite bus system with the target induction generators connected. This one-machine infinite bus system includes a power transmission line 2 connected to the infinite bus 1 and a cage induction generator 4 connected to the load-side bus 3 of the power transmission line 2. In the figure, F is a three-phase ground fault point occurring in the transmission line 2 , R ₁ , R _30-1 and L ₁ , L _30-1 are the resistance and inductance of the transmission line 2 , CB1, CB2, and CB3 are The lower case letter L of the circuit breaker, the resistance and the inductance indicates the distance from the induction generator to the failure point. Table 1 shows the system parameters used for the simulation.
[0012]
[Table 1]
System parameter Rated power 674kVA
Rated line voltage 690V
Rated frequency 50Hz
Number of poles P 4 pole Rotor resistance R _s 0.0118 p. u.
Rotor leakage inductance L _ls 0.217 p. u.
Rotor resistance _{r 'r 0.0156p.} u.
Excitation inductance L ′ _m 7.28 p. u.
Line resistance R _l 0.000195 p. u. / Km
Line inductance L _l 0.0195 p. u. / Km
Inertia constant J 18.03kgm ²
In the one-machine infinite bus system using the squirrel-cage induction generator 4 of FIG. 1, a stability analysis of the induction generator 4 was performed assuming that a three-phase ground fault F occurs on the transmission line 3. Figure 2 is an equivalent circuit of the induction generator 4 when three-phase ground fault, in the drawing, V _f is the voltage at the fault point F, R _l, L _l is the line of resistance and inductance, r _r ', L _r ′ Is the resistance and inductance of the induction generator rotor, ω _r is the rotor angular velocity, and λ ′ _dr is the d-axis flux linkage number. Q-axis than 2 when three-phase ground fault, d-axis current assuming the rotor angular velocity omega _r is constant, q-axis current i _qs, i _'qr and the d-axis current i _ds, i' _dr is ( 1) to (4).
[0013]
[Expression 1]

[0014]
Where ω _rss in the equation is the angular velocity of the rotor in the steady state, θ _s is the phase angle of the a-phase stator current when the three-phase ground fault occurs, and “” is attached to the time t in the equation This shows the elapsed time when the three-phase ground fault occurrence time is considered to be zero. Other constants are shown in Table 2.
[0015]
[Table 2]

[0016]
Further, the output torque T _em and the power P _IG of the induction generator are expressed by (5) and (6 formula).
[0017]
[Expression 2]

[0018]
By substituting (1) to (4) into (5) and rearranging, (7) is obtained.
[0019]
[Equation 3]

[0020]
2. Equation of motion Derivation of a velocity equation expressing the rotor angular velocity at the time of a three-phase ground fault will be described using the transient analysis equations (equations (1) to (7)). The equation of motion of the rotor is expressed by equation (8).
[0021]
[Expression 4]

[0022]
Here, ω _f ; rotor angular velocity during the failure period, T _mech ; mechanical input torque, T _damp ; braking torque. here,
[0023]
[Equation 5]

[0024]
Then, when equation (8) is solved for the rotor angular velocity ω _f , equation (9) is obtained.
[0025]
[Formula 6]

[0026]
[Expression 7]

[0027]
It is. Here, from (2α / ω _rss ) ² << 1, Z _A ≈1, and when L _m >> L′ l _r , θ _A ≈θ _B and A≈B hold. Therefore, the first term on the right side of equation (9) is sufficiently smaller than the second term and can be approximated as in equation (10).
[0028]
[Equation 8]

[0029]
By using the equation (10), it is possible to express the output power of the induction generator in consideration of the rotor speed change during the three-phase ground fault period. When the expression (10) is used, the output power of the induction generator during the failure period is rewritten as the expression (11).
[0030]
[Equation 9]

[0031]
The validity of the expressions (10) and (11) is verified by comparing with the results of simulation using a numerical calculation program. The simulation model in the numerical calculation program is constructed using system equations considering the nonlinearity of the induction generator.
FIGS. 3A and 3B show the calculation results (solid line) based on the analytical expressions of the rotor angular velocity and output power (solid line) and the simulation results (dotted line) using the numerical calculation program. However, FIG. 3 is a simulation result when a three-phase ground fault occurs in the center of the transmission line (t _f = 4.0 sec) during steady operation of the induction generator.
[0032]
From FIG. 3, the calculation result by the analytical expression is in good agreement with the simulation result using the numerical calculation program, and the validity of the analytical expression can be confirmed. In FIG. 3, in the simulation result using the numerical calculation program, vibration is observed in the angular velocity of the rotor immediately after the ground fault, which is a component shown in the first term on the right side of equation (9). The error relating to the simulation result of the output power is due to an error in the value of the coefficient Z in the equation (11) due to the influence of the approximation used when deriving the analytical equation.
3. Analysis of stability of induction generator by equal area method Output power-slip characteristic, which is usually used for display of output characteristics of induction generator, is converted to time domain using equation (10), and stability analysis is performed by equal area method. The derivation of the necessary equations is performed.
3.1 Output power-slip characteristics The output characteristics with respect to the change in the rotor angular speed of the induction generator are expressed by equation (12).
[0033]
[Expression 10]

[0034]
Here, ω _e is the angular velocity of the power supply voltage. From the equation (12), the output power-slip characteristic of the induction generator is as shown in FIG. However, the characteristic of FIG. 4 is a case where the output power of the induction generator after the failure is assumed to be zero. In the figure, s _f is the generator speed in the steady state, and s _cr is the generator speed at the time of reclosing. Here, if the loss of the generator is ignored, A ′ _ac in the figure is energy that is added to the generator during the failure period and accelerates the rotor, and A ′ _de is energy that decreases the generator speed after recharging. is there. Therefore, the slip s _cr where A ′ _ac = A ′ _de is the stability limit of the induction generator.
3.2 Output power-time characteristics The output characteristics of the induction generator in the time domain will be described. When the expression (10) is substituted into the expression (12), the output power-time characteristic of the induction generator in the failure period is as shown in FIG. However, FIG. 4 shows a case where the output power of the induction generator after the occurrence of the failure is assumed to be zero, and in the actual analysis, a stability analysis is performed in consideration of the output shown in Equation (11). Therefore, if the generator output during the failure period is taken into account, A _ac and A _dc in the figure can be obtained by equations (13) and (14).
[0035]
## EQU11 ##

[0036]
Where P _ss is the generator output power in the steady state. In the equal area method, the stability limit is when A _ac = A _dc , the stability is stable when A _ac > A _dc , and the stability is stable when A _ac <A _dc . By using the equations (13) and (14), the stability limit time t ′ _cr obtained by A _ac = A _dc can be calculated.
4). Simulation results When a three-phase ground fault occurs on the transmission line, the reclosing time t _cr that becomes the stability limit for each mechanical input torque is obtained using the equations (13) and (14). The validity of the results is verified by comparing with the simulation results using a numerical calculation program. The reclosing time t _cr , which is the stability limit, is evaluated by fixing the transmission line length l = 30 km, the failure occurrence time t _f = 4.00 sec, the failure duration t _cont = 0.10 sec, and changing only the recharging time. In this case, whether or not the induction generator operates stably after being re-introduced. 5 (a) and 5 (b) are output waveforms of the rotational speed and active power at that time, FIG. 5 (a) is an output waveform when the induction generator continues a stable operation after recharging, and FIG. 5 (b). ) Is the output waveform when invariable after re-input. The reclosing time that becomes the stability limit is defined as a critical reclosing time (CRT) and is defined by the equation (15).
[0037]
[Expression 12]
CRT = t _cr −t _f (15)
Here, t _f and t _cr are fault occurrence time and the reclosing time, respectively. The failure sequence is that the induction generator is in steady operation and a three-phase ground fault occurs on the transmission line (t = t _f ), then the line breaker is opened (t = t _o ), and the generator is restored to the grid after the failure is restored. Input (t = t _cr ). Usually, re-introduction of the wind generator into the grid is about a few minutes after the failure is removed, but in order to confirm the validity of applying the equal area method to the stability analysis of the induction generator, Input was made several cycles after the failure disappeared.
[0038]
FIG. 6 (a) shows the results of calculation of the critical reclosing time CRT with respect to each mechanical input torque (solid line) and the results of simulation using the numerical calculation program (dashed line) in Table 3, and the results of plotting Table 3. Is shown in FIG.
[0039]
[Table 3]

[0040]
FIG. 6B shows a CRT analysis error. From FIG. 6, it can be seen that the stability analysis result (solid line) of the induction generator using the equal area method is in good agreement with the mechanical input torque-CRT characteristic obtained from the simulation result (dashed line) by the numerical calculation program. I can confirm.
II. Embodiment A method for analyzing the stability of an induction generator in the case of a three-phase ground fault by the equal area method according to an embodiment of the present invention will be described. This stability analysis is performed according to the procedure of FIG. 7 using the above equations (10), (12) to (14). First, the induction generator output power P _ss in the steady state is given and the failure occurrence time t _f = 0. Then, the rotor angular velocity ω _f of the induction generator during the failure period is obtained from the constant of the induction generator using the approximate expression (10), and then the output power-slip characteristic expression (12) of the induction generator is expressed as The time t ′ _f from the occurrence of the failure to P _sc = P _ss is obtained. Next, using Equations (13) and (14), energy A _ac that is applied to the generator during the failure period to accelerate the rotor and energy A _de that reduces the generator speed after reclosing is calculated, and A _ac = A Solve _de to find the stability limit reclosing time t ' _cr .
[0041]
According to the stability analysis method of the induction generator by this equal area method, the stability of the induction generator in the event of a three-phase ground fault can be easily obtained. The validity of the transient stability analysis result of the induction generator by this method was confirmed by comparing with the simulation result using the numerical calculation program as described above. This stability analysis of the induction generator by the equal area method is effective in evaluating the stability of the induction generator during a three-phase ground fault.
[0042]
【The invention's effect】
As is clear from the above description, according to the present invention, it is possible to shorten the time for analyzing the stability of the induction generator in the event of a three-phase ground fault. Further, the stability limit reclosing time of the induction generator can be calculated from the stability limit formula based on the equal area method without requiring numerical integration.
[Brief description of the drawings]
FIG. 1 is a system diagram of a one-machine infinite bus connected to a target induction generator.
FIG. 2 is a q-axis equivalent circuit diagram at the time of one-machine infinite bus system three-phase ground fault.
3A is a rotor angular velocity time-time characteristic diagram showing calculation results and simulation results of rotor speed analysis, and FIG. 3B is an output showing output power analysis formula calculation results and simulation results. Power-time characteristic diagram.
4A is an output power-slip characteristic diagram when the output power of the induction generator after the occurrence of a failure is assumed to be zero, and FIG. 4B is an assumption that the output power of the induction generator after the occurrence of the failure is zero. The output power-time characteristic figure at the time of doing.
FIG. 5A is an output waveform diagram when the induction generator continues stable operation after re-input, and FIG. 5B is an output waveform diagram when invariable after re-input.
6A is a mechanical input torque-CRT characteristic diagram showing calculation results and simulation results of CRT (critical reclosing time) with respect to the mechanical input torque of the induction motor, and FIG. 6B is a calculation result thereof; The mechanical input torque-CRT analysis error characteristic figure which shows a difference with a result and a simulation result.
FIG. 7 is a system conceptual diagram of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Infinite bus 2 ... Transmission line 4 ... Cage type induction generator F ... Three-phase ground fault P ... Number of induction generator poles _ss ... Steady state induction generator output power _PIG ... Induction generator output Electric power P _sc ... Output characteristics against changes in the induction generator rotor angular velocity
CRT ... Critical reclosing time

Claims (3)

Using the output power-time characteristics of the induction generator, the energy that is applied to the generator during the failure period to accelerate the rotor and the energy that decreases the generator speed after reclosing are calculated, and the stability limit is reached because both are equal. A method for analyzing the stability of an induction generator, characterized by calculating a reclosing time. In claim 1,
A method for analyzing the stability of an induction generator, wherein the output power-time characteristic of the induction generator is obtained from an output power-slip characteristic equation of the induction generator. In claim 2,
When the output power-time characteristic of the induction generator is obtained from the output power-slip characteristic equation of the induction generator, the induction generator power generation using the approximate equation of the rotor angular velocity is calculated using the rotor angular velocity of the induction generator during the failure period. A method for analyzing the stability of an induction generator, characterized in that it is obtained from a constant of the machine.

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