JPS6268024A - Parallel connecting method for power system of induction generators - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for parallel connection of a generator to a power system in a power generation facility mainly using an induction generator.

[Prior art and its problems]

When an induction generator is connected in parallel to a power system, it is important to suppress the rush current that occurs at that time to prevent adverse effects such as abnormal voltage drop on the power system as much as possible. In general, when an induction generator is operated, its phase does not necessarily need to match the phase of the power grid, and there is no risk of causing disturbances. Since it has the advantage that either of them can be used without any problems, it is suitable for induction generation for the purpose of small-scale power generation development that is effective for recovering surplus energy in fields such as hydroelectric power generation equipment or engine power generation equipment, or for the installation of backup power sources, emergency power sources, etc. Power generation equipment that uses an induction generator as the main engine is attracting attention. However, an induction generator cannot normally generate electricity by itself, and must be operated in parallel with another synchronous machine or power grid to receive the excitation power. Because of this condition, there arises the problem of parallel connection operation of induction generators to power grids, etc. Originally, two generators should be operated in parallel, such as between generators or between generators and power grids. If the power supplies are connected in parallel at the point where their voltages are in the same phase when their respective voltages and frequencies are the same, so-called synchronous parallel operation, no inrush current will occur between the two power supplies. Therefore, when operating two power supplies in parallel, the most effective means of suppressing inrush current is to connect them both in parallel. It is necessary to have a voltage value and frequency convenient for connection operation.However, in conventional power generating equipment using a general induction generator as the main engine, as shown in Fig. 4, the induction generator driven by the prime mover 1 The generator 2 is connected to the power grid via the power supply bus 9 only after the main circuit breaker 5 is closed at the moment when the slip frequency output from the generator 2 via the rotating generator 4 and the slip detection device 6 becomes almost zero. Because it is designed to be connected, it is impossible to generate a voltage suitable for parallel connection in advance in advance of the parallel connection operation to the power grid as described above.
Therefore, synchronous parallel connection operations in the power system as described above are possible, and as a result, generation of a large inrush current upon parallel connection, and therefore voltage drop in the power system caused by this cannot be avoided. However, the value of the rush current that occurs at that time is as shown in Figure 3.
For example, the voltage t of the power system and the induced voltage t of the induction generator 2
, the vector voltage difference Δt, which takes into account the phase difference between them, is divided by the sum of the impedance of the power system and the internal impedance of the generator 2. At this time, the phase difference between the t and the tung changes in accordance with the temporal change in the frequency difference between the induction generator 2 and the power system. Furthermore, in the conventional induction generator 2, the induced voltage t,
rises from zero at the moment the generator 2 is connected to the power supply bus 9, so the vector voltage difference Δ9 is almost equal to the voltage t of the power system at the moment the generators 2 are connected in parallel; In this case, even if the generator 2 is sped up to almost synchronous speed by the prime mover 1 and the influence of the current caused by the frequency difference with the power grid is eliminated, the value of the inrush current will still be significantly large. Avoiding is difficult. Furthermore, the residual magnetism of the iron core of the induction generator 2 produces a phase that reduces the internal impedance of the generator 2 depending on the magnitude and direction of its value at the moment when the generator 2 is connected in parallel to the pre-electromotive force system, As a result of unbalanced direct current components being superimposed on each phase, the rush current may further increase. In any case, in the conventional parallel connection operation of induction generators to the power system, it is unavoidable that a large inrush current is generated at the moment the parallel connection is made, causing a voltage drop in the power system. In order to prevent this, the disadvantage is that it is necessary to take complicated measures, such as inserting a rush current suppressing glue handle into the circuit of the induction generator.

Purpose of the Invention 1 In view of the above-mentioned drawbacks of the conventional method of connecting induction generators in parallel to an electric power system, etc., the present invention provides a method for applying voltage to the induction generator in advance, independently of the electric power system, prior to the parallel connection operation. It is an object of the present invention to provide a method of connecting the generator in parallel to a power system or the like under such a voltage and frequency that the inrush current that occurs during parallel connection can be suppressed by inducing the generator, a so-called synchronous parallel connection method. [Summary of the Invention] In order to achieve the above object, in the present invention, in the parallel connection method described above, a stator terminal of the generator provided with a speed detecting means is connected to the electric power system etc. through the shaft end. An appropriate amount of capacitors are connected in parallel, and a synchronization verification turning-on operation means is connected between the terminal and the power grid, and the generator is sped up to the rated speed or almost the rated speed by the prime mover to generate the power. A voltage equal to or almost equal to the voltage of the electric power system is induced in the generator alone, and the voltage between the induced voltage of the generator and the voltage of the electric power system is 31.
By performing the Jl test and synchronously closing the main circuit breakers of the generator, the inrush current is suppressed as much as possible, and the induction generator is connected in parallel to the power system.

[Embodiments of the invention]

Next, the present invention will be explained in detail based on embodiments shown in the drawings. As illustrated in FIG. 1, a stator terminal 2a of an induction generator driven by a prime mover 1 equipped with a speed governor 3 is connected to a source bus 9 connected to the power system via a main interrupter 1P15. A tachometer generator 4 is provided at the end of the rotor shaft of the generator 2 and is connected to a slip detection device 6 . Furthermore, an appropriate amount of capacitors 11 are connected to the terminal 2a of the induction generator 2 via a switch 10 in parallel with the source bus 9,
Further, a synchronization verification closing operation unit 1 is connected between the stator terminal 2a and the mother uI9 via a transformer 13 respectively.
2 is connected, while 1. Outputs from the B-spear constant closing operation section 12 and the slippage detection device [6] are input to a sequence calculation section 14, and the main circuit breaker 5 is closed by the output. In a power generation equipment having an induction generator as a main engine configured as described above, when the switch 10 is stopped and the capacitor 11 is connected, the induction generator 2 is started by the prime mover 1, or the induction generator 2 is started by the prime mover 1. When the switch 10 is closed and the capacitor 11 is connected when the rotation speed reaches an appropriate speed after starting the generator 2, a voltage due to the residual magnetism of the generator 2 is applied to the capacitor 11, and as a result, a phase-advanced current is applied to the generator 2. The voltage flows into the unit 2 and further increases its voltage. As this phenomenon repeats, that is, as the self-excitation of the induction generator 2 by the capacitor 11 progresses further, the voltage of the induction generator 2 eventually stabilizes at a value determined by its saturation characteristics and the excitation current characteristics by the capacitor 11. . Now, when the amount of capacitor 11 is constant, the frequency f of the generator 2 is used as a parameter to calculate the generator voltage V. As shown in FIG. 2, which shows the relationship between
The stable point P moves within a specific range on the stability characteristic curve as the frequency f changes. That is, the frequency of the generator 2 is f ed via the prime mover 1.
+f 1. When the voltage is changed to f9u, the generator voltage changes accordingly to vId+@r+v@u, and the capacitor current also changes to lCd+Icr+lcu. Accordingly, the stable point of the generator is the lower limit ■ Pa (f@4+ *a, t-a) with the rated stable point p, (r, , , , , lcr ) above the stability characteristic curve. and upper limit P
u (flul v111+1cm). Therefore, the amount of the capacitor 11 is determined according to the stability characteristic curve shown in FIG. 2 and the phase difference θ between the generator 2 and the power system.
The voltage difference Δt (FIG. 3) can be determined in consideration of the tolerance value of the mutual voltage difference Δt (FIG. 3) obtained by accurately detecting the voltage difference Δt. At this time, in order to connect the induction generator 2 in parallel to the electric power system, when the stable point P is near P on the stability characteristic curve, the synchronization verification closing operation section 12 is activated to generate the power. The synchronization state of the generator 2 with the power system is detected, and depending on the result, the speed governor 3 of the prime mover 1 is operated to change the frequency f of the generator 2, and the difference from the frequency f- of the power system is detected. Δf-f, -f, and the voltage difference Δ+-+, -9, including the phase difference θ between the generator 2 and the power system;
If the main circuit breaker 5 is closed when the Δt is zero or the minimum value and the Δf is zero or almost zero, the inrush current can be reduced. A zero or minimum synchronous parallel connection is realized. At this time, the slip detection device 6, which played a leading role in providing the basic signal for closing the main circuit breaker 5 in the conventional parallel connection method, is replaced by the synchronous verification device 6, which emits the main signal, in the synchronous parallel connection method of the present invention. It merely plays an auxiliary role to the operating section 12. In this case, as described above, inducing an appropriate voltage in advance with the capacitor 11 before connecting the induction generator 2 in parallel to the power system enables the synchronous parallel connection operation of the generator 2 to the power system. Not only to
Effects such as eliminating the above-mentioned influence of residual magnetism on the internal impedance of the generator 2 and preventing transient fluctuations in the vector voltage difference Δt caused by the voltage rise of the generator 2 at the moment of parallel connection. There is. Generally, as shown in Fig. 1, in power generation equipment that uses an induction generator as its main engine, a power factor correction capacitor 8 is connected to a power supply bus 9 that connects the induction generator 2 to the power system, etc. Depending on the case, a part of the power factor correction capacitor 8 may be used as the excitation capacitor 11 of the machine 2. Furthermore, the timing to connect the excitation capacitor 11 to the induction generator 2 does not necessarily have to be when the generator 2 is stopped;
This can be carried out at any time during acceleration until the generator 2 reaches the rated speed.

【Effect of the invention】

As explained above, the present invention provides a method for connecting a generator in parallel to a power system in a power generation facility mainly using an induction generator, in which the generator is fixed with a speed detecting means provided through its shaft end. An appropriate amount of capacitor is connected to the child terminal in parallel with the power system, etc., and a synchronization verification turning operation means is connected between the terminal and the power system, etc., and the generator is operated by the prime mover at or near the rated speed. The speed is increased to a high speed, and a voltage equal to or almost equal to the voltage of the electric power system is induced in the generator alone, and the synchronization test input operation means causes the induced voltage of the generator and the voltage of the electric power system to be induced in the generator alone. By performing a synchronization test with the voltage and synchronizing the main circuit breaker of the generator, the inrush current can be reduced to zero or to a minimum when the induction generator is connected in parallel to the power system, etc. It is possible to suppress the voltage drop in the electric power system, etc., and eliminate obstacles to the stability of power sources such as those connected in parallel, making it possible to economically advantageous small-scale power supply development and emergency This has the effect of significantly contributing to the promotion of the installation of power supply equipment.

[Brief explanation of drawings]

FIG. 1 is a schematic wiring diagram of a power generation facility whose main engine is an induction generator connected to the power system by the parallel connection method of the present invention.
Figure 2 shows the voltage stability characteristic curve of the generator, Figure 3 shows the vector voltage difference between the generator and the power grid, and Figure 4 shows the induction generator connected to the power grid by the conventional parallel connection method. This shows a schematic wiring diagram of a power generation facility with a main engine. 1: Prime mover, 2: Induction generator, 2a+ stator terminal, 4-
Tachometer generator, 5: Main circuit breaker, 6I slip detection device, 11
: Excitation capacitor, 121 synchronous verification input operation part, 14
+Sequence calculation section. Figure 3 Procedural amendment (voluntary) Indication of case - ShowζQ-ZO denial♂δ7 address
1-1 Tanabeshinden, Kawasaki-ku, Kawasaki City Name (5231 Fuji Electric Co., Ltd., Address: 1-1-1 Tanabeshinden, Kawasaki-ku, Kawasaki City, 5゜6゜7゜8, - Contents of amendment 1. Patent claim The range of is corrected as follows: ``1) Permutation H of the generator in power generation equipment using a B'g-derived conductive plate electric machine, etc. to the power system etc. Connect an appropriate amount of capacitor to the terminal, and connect an appropriate amount of capacitor to the terminal.
A synchronization verification switching operation means is connected between the generator and the like, and the generator is sped up to the rated speed or almost the rated speed by the prime mover, and the voltage of the generator alone is equal to or almost equal to the voltage of the power system, etc. A voltage is induced, and the synchronization test closing operation means performs synchronization verification between the induced voltage of the generator and the voltage of the power system, etc., and performs a synchronization closing operation of the main circuit breaker of the generator. A method for connecting induction generators in parallel to a power system, etc., which is characterized by the following: 2. In the specification, page 2, lines 10 to 12, ``Induction generators do not necessarily have to match their phase with the phase of the power grid during operation, and there is no possibility of causing disturbances, making them extremely easy to handle.'' Ease-1 is corrected to ``Easy to operate with a 1-induction generator system compared to a synchronous generator''. 3. [Rotary generator 4] on page 3, lines 19 and 20 of the specification
``and slipping'' is changed to ``speed detecting device such as rotary generator 4 and slipping''
and correct it. 4. In the specification, page 6, line 11, [through the shaft end -1] is corrected to "through the shaft end, etc.". 5. Correct "-1 to the fixed terminal in parallel to the power system etc." in the 12th and 13th lines of page 6 of the specification to "in parallel to the fixed terminal." 6. "Above of generator 2" in lines 9 and 10 of page 9 of the specification is corrected to "1 of the voltage generated by generator 2." 7. Lines 14 to 16 of page 11 of the specification Correct "parallel to the electric power grid, etc. to the stator terminal of the generator provided with speed detection means via its shaft end" in the row to "parallel to the stator of the generator".

Claims (1)

[Claims] 1) In a method of parallel connection of the generator to a power system, etc. in a power generation facility mainly using an induction generator, the power system, etc. is connected to the stator terminal of the generator provided with a speed detection means through its shaft end. A suitable amount of capacitor is connected in parallel with the terminal, and a synchronization verification turning operation means is connected between the terminal and the power grid, and the generator is sped up to the rated speed or almost the rated speed by the prime mover. inducing a voltage equal to or almost equal to the voltage of the electric power system etc. in the generator alone, and performing synchronization verification between the induced voltage of the generator and the voltage of the electric power system etc. by the synchronization verification input operation means; A method for parallel connection of induction generators to a power system, etc., characterized in that the main circuit breakers of the generators are synchronously closed.