JPH0213560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation device that controls the excitation current of a field coil of a generator.

For convenience of explanation, both a conventional excitation device and an embodiment of the excitation device of the present invention will be described in the case of a thyristor excitation device for a self-excited generator.

FIG. 1 is a circuit diagram showing a conventional thyristor excitation device. In Fig. 1, 1 is a generator, 2 is a field coil of this generator 1, 3 is a bus bar, 4 is a main transformer connected to this bus bar 3, 5 is a voltage transformer, and 6 is a voltage transformer 5. An automatic voltage regulator (hereinafter referred to as AVR) that outputs a signal corresponding to the deviation from the set voltage for the voltage applied through the AVR6, and 7 is a point that outputs a pulse with a phase corresponding to the voltage deviation according to the signal of this AVR6. The arc device 8 is a thyristor amplifier that sends an output to the field coil 2 according to the signal from the ignition device 7.

Next, the operation of the above configuration will be explained.

Now consider the case where the terminal voltage of generator 1 exceeds the set value. The terminal voltage of the generator 1 is led to the AVR 6 via a voltage transformer 5 connected to the bus 3. The AVR 6 detects the difference between the generator terminal voltage and the set voltage and gives a signal to the ignition device 7 to lower the excitation current of the field coil 2 in accordance with the difference. Based on this signal, the ignition device 7 sends a pulse signal to the thyristor amplifier 8 with a phase corresponding to the voltage deviation in the downward direction. As a result, the thyristor amplifier 8
lowers the output current so that the excitation current of the field coil 2 decreases. By the above operation, the terminal voltage of the generator 1 is maintained at the set voltage.

Conversely, even if the terminal voltage of the generator 1 falls below the set value, the thyristor amplifier 8 outputs a current that increases the excitation current of the field coil 2 according to the output signals of the AVR 6 and the ignition device 7. Therefore, generator 1
The terminal voltage of is kept constant.

However, the conventional excitation device illustrated in FIG. 1 has the following disadvantages.

When a capacitive load is connected to the non-excited generator 1, a current flows due to the voltage generated by residual magnetism, and the terminal voltage of the generator 1 naturally rises due to the so-called self-excitation phenomenon. However, the output of the thyristor amplifier in the conventional thyristor excitation device has a capacity of at least 0 amperes, and it is not possible to flow a current in a direction that cancels residual magnetism, that is, in a direction opposite to the normal excitation current. Therefore, when a capacitive load is connected to a non-excited generator, voltage is induced by the generator, and depending on the size of the capacitive load, a very large voltage rise may occur, which may damage the insulation.

SUMMARY OF THE INVENTION An object of the present invention is to provide an excitation device that solves the above-mentioned drawbacks by adding a DC power source such as a thyristor amplifier that excites a generator field coil in the opposite direction to the conventional excitation device.

2 and 3 are circuit diagrams showing one embodiment of the present invention, in which FIG. 2 is a circuit diagram showing a thyristor excitation device, and FIG. 3 is an explanatory view of the main part of FIG. 2. In FIGS. 2 and 3, 7a and 7b are ignition devices having the same functions as the conventional ignition device 7, and the ignition phase of the ignition device 7a is α ₁ and the ignition phase of the ignition device 7b is α 1 . When α ₂ is assumed, the phase relationship between the output pulses of the ignition devices 7a and 7b is α ₁ +α ₂ 180°. 8a and 8b are thyristor amplifiers having the same functions as the conventional thyristor amplifier 8;
Thyristor amplifier 8b and thyristor amplifier 8a are connected in parallel so that the polarity is opposite to that of thyristor amplifier 8a.
i ₁ is the excitation current by the thyristor excitation device 8a, i ₂
is an excitation current by the thyristor excitation device 8b, and in a normal load state of the generator 1, a current flows in the same direction as the current _i1 in the field coil 2. I
is a circulating current that constantly circulates and flows through the thyristor excitation devices 8a and 8b. 9 is a current limiting reactor that suppresses the circulating current I.

Next, the operation of the present invention with the above configuration will be explained. In FIG. 2, consider the case where the generator 1 is in a non-excited state and a capacitive load is connected. When the terminal voltage of the generator 1 increases due to the self-excitation phenomenon and exceeds the set voltage of the AVR 6, a signal corresponding to the voltage deviation is sent from the AVR 6 to the ignition devices 7a and 7b.
sent to. Since the ignition devices 7a and 7b send pulse signals with a phase corresponding to this voltage deviation to the thyristor amplifiers 8a and 8b, the thyristor amplifier 8
The outputs of a and 8b are controlled by the phase of the pulse signal, and in the above state, the output of the thyristor amplifier 8b is smaller than that of the thyristor amplifier 8a.
Since the ignition is controlled such that the output of Therefore, an increase in the terminal voltage of the generator 1 is suppressed and the voltage is kept constant.

That is, to explain this using FIG. 3, the relationship between the output i ₂ of the thyristor amplifier 8b and the output i ₁ of the thyristor amplifier 8a is i ₂ >i ₁ , and the field coil 2 is under normal load condition. The magnet is excited by a current in the opposite direction to the exciting current, thereby canceling out the residual magnetism.

In the above, the case where the excitation device according to the present invention suppresses the self-excitation phenomenon of the generator has been described, but when reducing the excitation current in the normal load state of the generator, the output current i ₁ of the thyristor amplifier 8a By decreasing the current and simultaneously increasing the output current of the thyristor amplifier 8b, there is an effect that the response speed can be increased and transient stability can be improved.

Further, the current source of the excitation current is sufficient for the purpose if it is a DC power supply whose output is controlled according to an input signal, and is not necessarily limited to the thyristor amplifier shown in the above embodiment.

In the above embodiments, the present invention has been described only with respect to a self-excited generator, but it goes without saying that it can also be applied to a separately-excited generator.

As described above, the excitation device according to the present invention includes first and second DC power sources that output excitation currents in opposite directions to the field coil of the generator, and these DC power sources are adjusted according to the output voltage of the generator. Since the output of the power source is controlled, the self-excitation phenomenon of the generator can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional excitation device, FIG. 2 is a circuit diagram showing an embodiment of the excitation device according to the present invention, and FIG. 3 is an explanatory diagram of the main part of FIG. 2. In the figure, 1 is a generator, 2 is a field coil, 6
is an automatic voltage regulator, and 8a and 8b are DC power supplies such as thyristor amplifiers. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first DC power supply for supplying exciting current to the field coil of the generator by an output signal from an automatic voltage regulator that adjusts the terminal voltage of the generator, and a first DC power supply in the opposite direction. A pair of DC power supplies consisting of a second DC power supply connected in parallel so as to have the same polarity are simultaneously operated, and in a normal load state of the generator, the output from the first DC power supply is supplied to the field coil. When the terminal voltage of the generator increases due to a self-excitation phenomenon and exceeds the set voltage of the automatic voltage regulator, the voltage is output from the second DC power supply. An excitation device characterized by controlling the current to flow in the same direction as the current to prevent an abnormal rise in the terminal voltage of a generator due to a self-excitation phenomenon. 2. The excitation device according to claim 1, wherein the first and second DC power supplies convert alternating current into direct current using thyristors and output the converted current.