JPH08149895A - Generator system driven by load-commutated inverter - Google Patents

Abstract

PURPOSE: To reduce duty of units other than a load-commutated inverter, by connecting a transformer to an output terminal of the inverter and a transformer to an output terminal of a synchronous generator. CONSTITUTION: When a synchronous generator is driven, a breaker 2a is opened to operate a converter 2c and a DC current (Id) is carried through a DC reactor 2d and an inverter 2e. In the inverter 2e, the DC current (Id) is changed into an AC current (Iac) with a variable frequency on using a control command from a phase control unit 2g. The synchronous generator is driven by the AC current (Iac) through a transformer 2f. When reactive power is lacking as the load increases abruptly in power system, the load-commutated inverter 2 is connected to an output terminal of the synchronous generator even after the synchronous generator is driven. Then, the reactive power is fed as an output from the inverter 2e in the load-commutated inverter 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load commutation type inverter start-up power generation system in which a variable frequency AC is applied to a stator winding of a synchronous generator to start the synchronous generator to start operation.

[0002]

2. Description of the Related Art Conventional load commutation type inverters (Load Com
Mutant Inverter (hereinafter abbreviated as LCI) A configuration example of a start-up power generation system is shown in FIG. 5, and the configuration and action will be briefly described below. In FIG. 5, 1 is a synchronous generator, 2 is an LCI device for starting the synchronous generator 1, and includes a circuit breaker 2a, a transformer 2b, a converter 2c, and a DC reactor 2.
d, inverter 2e, AC reactor 2i, disconnector 2h
And so on. An excitation device 1a and an excitation control device 1b for exciting the field winding of the synchronous generator 1 are provided. Reference numeral 3 is a main transformer, and A, B, C and D are connection lines for electrically connecting the respective constituent devices.

When the synchronous generator 1 is driven, the breaker 2
a is closed, the converter 2c is operated, and the direct current I
d flows to the DC reactor 2d and the inverter 2e.
The inverter 2e switches the direct current Id of the LCI device 2 into a variable frequency alternating current Iac. The alternating current Iac flows through the connecting wire D to the stator winding of the synchronous generator 1, and the synchronous generator 1 is started. The synchronous generator 1 starts power generation after being driven by the LCI device 2, and is fed to the system side via the main transformer 1.

The reactive power adjusting device 4 supplies the required reactive power when the reactive power rapidly becomes insufficient due to a sudden increase in load on the system side. Further, when a short-circuit accident or the like occurs in the power transmission line on the system side, the generator output P _G of the synchronous generator 1 fluctuates, so that the fluctuation is converged so that the synchronous generator 1 does not step out. It is controlled by the excitation control device 1b and the excitation device 1a.

Generally, in the LCI start-up power generation system, L
The CI device 2 is used only when the synchronous generator 1 is started, and after the synchronous generator 1 is driven, the disconnector 2h is opened and the breaker 2a is also opened, and the LCI device 2 is disconnected from the synchronous generator circuit. Become.

[0006]

As is clear from the configuration example shown in FIG. 5, the LCI device 2 operates only when the synchronous generator 1 is first driven, and is used for other purposes. Not not. For example, when the reactive power is momentarily insufficient on the system side, the reactive power adjusting device 4 is used for adjustment, and the exciting control device 1b and the exciting device 1a are also used for adjustment during a system-side accident. A high level of ability was required.

On the other hand, although the LCI device has a reactive power adjusting function and an active power adjusting function, the LCI device is limited in capacity and used only from the economical point of view. There was a problem that it was inefficient and had a complicated structure as a power generation system.

The present invention has been made in view of the above circumstances, and an object thereof is to make full use of potentials such as reactive power and active power adjustment capability of an LCI device, which are highly functional, and a power generation system is simple. An object of the present invention is to provide an LCI start-up power generation system capable of reducing the responsibility of devices other than the device, such as an exciting device.

[0009]

In order to achieve the above object, the first aspect of the present invention is to apply a variable frequency alternating current to the stator windings of a synchronous generator to start the synchronous generator for operation. In the load commutation type inverter start-up power generation system to be started, a transformer is connected to the inverter output side of the load commutation type inverter device, the transformer is connected to the synchronous generator output side, and reactive power is generated on the grid side. When the above is required, this reactive power is supplied from the load commutation type inverter device.

According to a second aspect of the present invention, in the load commutation type inverter-starting power generation system according to the first aspect, when the output of the synchronous generator is fluctuated due to a failure such as a transmission line accident on the system side, the synchronization is performed. The load commutation type absorbs power from the inverter of the load commutation type inverter device during the period when the synchronous generator output increases in synchronization with the excitation control device of the generator, and the load commutation type during the period when the synchronous generator output decreases. Power is emitted from the inverter of the inverter device.

According to a third aspect of the present invention, in the load commutation type inverter start-up power generation system according to the first or second aspect, during normal operation, the inverter of the load commutation type inverter device is operated in a reflux mode. Characteristic load commutation type inverter start-up power generation system.

According to a fourth aspect of the present invention, in the load commutation type inverter start-up power generation system according to any one of the first to third aspects, during the period when the reactive power is required on the system side, the load commutation type inverter device is operated. It is characterized in that the converter is operated in the reflux mode.

[0013]

According to the first aspect of the present invention, when a sudden shortage of the reactive power occurs on the system side, the thyristor phase angle control of the inverter causes the system voltage and the voltage difference to be generated to supply the required reactive power. be able to.

According to the second aspect of the present invention, when a short-circuit accident or the like occurs in the power transmission line on the system side, the active power, that is, the power factor of the input of the inverter is made variable by controlling the thyristor phase angle of the inverter, thereby varying the output of the generator. Can be controlled in a direction to suppress the.

According to the third and fourth aspects of the present invention, it is possible to cancel the interconnection of the inverter and the converter with the AC system, and prevent excessive reactive power supply and propagation of high frequency to the system side. It becomes possible.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment (corresponding to claim 1) of the present invention. In the figure, when driving the synchronous generator 1, the circuit breaker 2a is closed, the converter 2c is operated, and the DC current Id flows through the DC reactor 2d and the inverter 2e. The inverter 2e converts this direct current Id into a variable frequency alternating current Iac according to a control command from the phase controller 2g. The alternating current Iac flows into the stator winding of the synchronous generator 1 via the transformer 2f and starts the synchronous generator 1.

When reactive power becomes insufficient due to a sudden increase in load on the system side, required reactive power is supplied to the system side as described below. That is, the LCI device 2 is electrically connected to the output side of the synchronous generator 1 even after the synchronous generator 1 is activated, and reactive power is supplied by the output of the inverter 2e of the LCI device 2.

In general, the output Q _IW of the inverter 2e is expressed as follows, where α is the phase control angle of the thyristor of the inverter 2e.
It is expressed by the following equation (1).

[Equation 1] As shown in the equation (1), the output Q _{IW of the} inverter 2e is proportional to the sine component (sin) of the phase control angle α. Here, α can be changed from 0 ° to 360 °, and by varying α, the absolute value | K |
If it is within the range, it is possible to supply both reactive power for the advanced phase and reactive power for the delayed phase.

As described above, according to this embodiment, the LC
The I-device 2 has not only the function of starting the synchronous generator 1,
Even when the reactive power is insufficient on the system side, it is possible to perform the function of supplying the required reactive power, and since it is not necessary to use the reactive power adjusting device as shown in the prior art,
The power generation system can be simplified accordingly.

Next, a second embodiment of the present invention (corresponding to claim 2) will be described. (Sign is inverted output if α exceeds 90) P _INV active power input of the inverter 2e of LCI device 2 is generally a thyristor phase control angle α
Then, there is a relationship as shown in equation (2), which is proportional to the cosine (cos) of the phase control angle α.

[Equation 2] Here, cos α is a power factor, α is variable from 0 ° to 360 °, and its control speed is several msec to several tens mse.
c and high speed. When a short-circuit accident of the transmission line or the like occurs on the system side, it is possible to suppress the generator output fluctuation of the synchronous generator, as described later in FIG.

FIG. 2 (a) is a diagram showing changes in the generator output P _G , and FIG. 2 (b) is a diagram showing changes in the inverter input (or output) P _INV of the inverter 2e of the LCI device 2. . As can be seen from this figure, immediately after the occurrence of the accident on the system side, that is, in the time region I, P _G sharply decreases and the phase angle of the synchronous generator 1 begins to open and is accelerated. P _{G in} time domain II
Exceeds the rated output Pgn and decelerates. The time domains III and IV make similar movements and then converge. This is due to the input control of the inverter 2e and the control of the excitation control device 1b.

Next, the input P _INV control of the inverter 2e will be focused and described. Input P _INV inverter 2e, since the synchronous generator 1 is in the time domain I and III to accelerate, the power is controlled in a direction to be input to the inverter 2e in proportion to the generator output, if uncontrolled (P _G It acts in the direction of decreasing the amount of the power generation output Pg that exceeds the rated output Pgn (arrow in the figure) compared to the broken line (indicated by arrow). This makes P _INV
The acceleration component of the generator is offset by the input of. Time domain
Even in the deceleration regions of II and IV, the deceleration component of the generator is canceled by the output of P _INV by the action opposite to the above, and the fluctuation gradually converges.

According to this embodiment, the LCI device 2 has not only the function of starting the synchronous generator 1, but also the function of suppressing the fluctuation of the generator output when a short-circuit accident occurs on the system side. Therefore, it is possible to reduce the duty of the exciter by the amount of the capability.

FIG. 3 is a configuration diagram of an inverter 2e portion of a third embodiment (corresponding to claim 3) of the present invention. Since the inverter 2e is always electrically connected to the output side of the synchronous generator 1, the reactive power shown in the equation (1) is always supplied. Now, if α = 90 °, it becomes 0 in the equation (1), but even in this case, the harmonic component superimposed on the alternating current Iac flows out to the system side. In order to prevent this, the inverter 2e can be prevented by adopting a reflux operation mode called a bypass pair operation.

Although various methods are possible for the bypass pair operation, as an example, the thyristor element 2e shown in FIG.
Of _{1 ~2e 6,} there is a method to conduct giving ignition command only to the thyristor element 2e ₂ and 2e _5. in this case,
The direct current Id flows so as to bypass the transformer 2f,
This can be prevented by setting reactive power and harmonic current Iac = 0 flowing out to the system side.

FIG. 4 is a block diagram of a converter 2c portion of a fourth embodiment (corresponding to claim 4) of the present invention. By bypassing performing pair operation similar to operation in the converter 2c, i.e. firing, conducting only thyristor 2c _2, 2c ₅ shown in FIG. 4 described in FIG. 3 in the present embodiment, the transformer a DC current Id It is possible to carry out the recirculation mode operation so as not to flow through 2b, and by this operation, the active / reactive power (P, Q) flowing from the system side can be made zero. Therefore, when reactive power control is performed using the inverter 2e, it is possible that the reactive power of the converter 2c has a reverse effect, and thus it is possible to prevent the bypass pair operation of the converter 2c from affecting it.

[0027]

As described above, according to the present invention, L
LCI start-up power generation that makes full use of the potential of the CI device such as reactive power and active power adjustment capability, has a high function, and simplifies the power generation system, and can reduce the responsibility of equipment other than the LCI device, such as the excitation device. A system can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a characteristic diagram in the case of the system fault of FIG.

FIG. 3 is a diagram showing an example of a bypass pair operation of the inverter shown in FIG.

4 is a diagram showing an example of bypass pair operation of the converter of FIG. 1. FIG.

FIG. 5 is a configuration diagram of a conventional LCI startup power generation system.

[Explanation of symbols]

1 ... Synchronous generator, 1a ... Excitation device, 1b ... Excitation control device, 2 ... LCI device, 2a ... Breaker, 2b ... Transformer,
2c ... Converter, 2d ... DC reactor, 2e ... Inverter, 2f ... Transformer, 2g ... Phase control device, 2h ... Disconnector, 2i ... AC reactor, 3 ... Main transformer, 4 ... Reactive power adjusting device, Id ... DC Current, Iac ... AC current, A,
B, C, D ... Connection line, I, ..., IV ... Time domain, P _G ... Generator output, P _INV ... Inverter input, Pgn ... Rated output,
2e ₁ ~2e ₆ ... thyristor element, 2c ₁ ~2c ₆ ... thyristor element, P ... active power, Q ... reactive power.

Claims (4)

[Claims] 1. A load commutation type inverter start-up power generation system in which a variable frequency AC is applied to a stator winding of a synchronous generator to start the synchronous generator to start operation. When a transformer is connected to the output side of the inverter and the transformer is connected to the output side of the synchronous generator, and reactive power is required on the system side, this reactive power is applied to the load commutation type inverter device. Load commutation type inverter-starting power generation system characterized by more supply. 2. The load commutation inverter start-up power generation system according to claim 1, wherein when the output of the synchronous generator fluctuates due to a failure such as a transmission line accident on the system side, the excitation control device for the synchronous generator. The load of the inverter of the load commutation type inverter device absorbs power during the period in which the output of the synchronous generator increases in synchronization with the power of the inverter of the load commutation type inverter device during the period of decrease of the output of the synchronous generator. A load commutation type inverter start-up power generation system characterized by releasing electricity. 3. The load commutation type inverter starting power generation system according to claim 1 or 2, wherein the inverter of the load commutation type inverter device is in a reflux mode operation during normal operation. Type inverter start-up power generation system. 4. The load commutation-type inverter start-up power generation system according to claim 1, wherein during the period when reactive power is required on the grid side, the converter of the load commutation-type inverter device is operated in a reflux mode. A load commutation type inverter-starting power generation system characterized by: