JPS62631A - Starting method for gas turbine - 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] [Industrial application field] The present invention relates to a method for starting a gas turbine.

[Conventional technology]

Figure 3 shows, for example, ASEA JOURNAL197
FIG. 6 is a circuit diagram showing a conventional starting device shown in VOLUME 49 NUMBER 3; In the figure,
Reference numeral 1 denotes a Cyrisk type converter, 2 a Cyrisk type separately excited inverter, and 3 a DC reactor, and these constitute a variable voltage variable frequency power converter P.

4 is a commercial power supply, 5 is an input transformer for matching, and 6 is an output transformer for matching. This output transformer 6 is inserted via a changeover switch 7.8 between the power converter P and the armature winding of the gas turbine generator 12. Reference numeral 9 denotes a bypass switch, which is connected in parallel to a series circuit consisting of a changeover switch 7, an output transformer 6, and a changeover switch 8. The generator 12 has a rotor position detector and is connected to a commercial power source 11 via a power switch 10. 13 is a field winding of the generator 12, and a field power supply 14
The field current is supplied from Reference numeral 15 denotes a gas turbine, which is connected to the generator 12 .

Next, the operation of this device will be explained.

Since the gas turbine 15 does not have self-starting ability until ignited, the generator 12 is started up as a thyristor motor in combination with the power converter P, and during this starting operation,
In the low frequency range, in order to prevent the iron core of the output transformer 6 from being magnetically saturated by the excitation current, the switch 9 is turned on and the changeover switches 7.8 are turned off to operate the output transformer 6 as a bypass susceptor, and the generator 12 When the speed increases to a certain speed, the switch 9 is turned off and the changeover switch 7.8 is turned on to operate. The generator 12 receives variable voltage variable frequency power from the power converter P until the speed increases to the ignition speed Nl of the gas turbine 15 (approximately 1/2 speed or less of the generator rated rotation speed),
The field is set to the rated field, and the electric motor is operated at a predetermined voltage/frequency ratio, and the gas turbine 15 speeds up by itself after ignition. When the speed of the gas turbine 15 increases to the rated rotational speed NO of the generator 12, the frequency, phase, and voltage of the generator 12 and the commercial power source 11 are matched, and then the power switch 10 is turned on to start the gas turbine generator 12. Complete.

(Problems to be Solved by the Invention) However, in this conventional device, if the rated voltage of the power converter is matched to the rated voltage of the generator, an expensive power converter is required. The rating is lowered and the voltages are matched by a transformer, but since the transformer is expensive, the cost of the equipment is still high.As mentioned above, at low frequencies, the iron core of the output transformer 6 becomes magnetic. There were problems such as the need for a bypass circuit, a switch for switching bypass, etc. to prevent saturation.

[Means to solve the problem]

In order to achieve the above object, this invention starts the electric motor of a generator by weakening the field of the generator to reduce the voltage/voltage.
The configuration is such that the frequency ratio is lowered.

[Effect]

In this invention, since the generator is operated as an electric motor with a lower voltage/frequency ratio, it is possible to directly feed the output of the power converter to the generator. Switches and the like for switching can be omitted.

〔Example〕

FIG. 1 is a circuit diagram showing one embodiment of the present invention, in which the output of the impark 3 is connected to the rotor of the generator 12 via a changeover switch 7, and the circuit diagram shown in FIG. The difference is that the switch 6, the bypass switch 9, and the changeover switch 8 are omitted.

In this configuration, the field current of the generator 12 is lowered below the rated value so that the generator voltage becomes the rated voltage E2 of the inverter 3 when the rotation speed of the power generator 1a12 reaches the ignition speed Nl of the gas turbine 15. The field is weakened, the voltage/frequency ratio is lowered below the above-mentioned predetermined voltage/frequency ratio, and the generator 12 is started as a zyristor motor. in general,
The rated capacity of the generator 12 is 10 times the capacity required at startup.
Since the field current is about twice as high, there is no problem even if the field current is significantly lowered.
If the generator voltage at the ignition speed N1 is El, then the voltage E1 can be selected so that El>E2. In FIG. 2, EO is the rated voltage of the generator 12.

When the gas turbine 15 reaches the ignition speed N1 and ignites,
Although the operation of the power converter P is stopped and the changeover switch 7 is opened, it is desirable to adjust the field current so that the voltage of the generator does not increase during this time. When the speed of the gas turbine 15 increases and reaches the rated speed No., the frequency, phase, and voltage of the generator output are matched with those of the commercial power source 11, and the power switch 10 is turned on to complete the startup.

In this embodiment, the field of the generator 12 is lowered to start the motor so that the generator voltage at the gas turbine ignition speed matches the output voltage of the inverter 2, so it is the most economical power converter A. You can use the rated one.

〔Effect of the invention〕

As explained above, this invention matches the voltages between the generator side and the power converter side by weakening the field of the generator, so the conventional matching output transformer can be omitted. Since a switch circuit for bypassing the transformer is also not required, the cost of the device can be reduced and the space required can be reduced compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a voltage-speed characteristic diagram for explaining the above embodiment, and FIG. 3 is a circuit diagram showing a conventional Cyrisk starting device. In the figure, 1-converter, 2-inverter, 3-
DC reactor, 7--changeover switch, 10--power switch, 12--generator, 15-gas turbine. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a method for starting a gas turbine, the generator of the gas turbine generator is combined with a power converter and used as an electric motor at a predetermined voltage/frequency ratio to increase the speed to a speed at which the gas turbine can ignite. A method for starting a gas turbine, the method comprising: weakening the field and increasing the speed of the generator at a voltage/frequency ratio lower than the predetermined voltage/frequency ratio.