JPH0341036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a device for quickly establishing the initial field flux of a superconducting generator with an extremely long field time constant without increasing the capacity of the exciter. .

Technical background of the invention and its problems A superconducting generator uses a superconducting material in the field winding of a synchronous generator, and is used in a superconducting state at an extremely constant temperature.
The aim is to reduce ohmic loss in the field circuit and improve generator efficiency. Although superconductivity can dramatically reduce the resistance of the field circuit, the time constant of the field circuit typically reaches several thousand seconds, compared to several seconds for conventional normal conduction generators. be. Therefore, after starting the generator, it would take several thousand seconds to establish the field magnetic flux using an ordinary excitation device, which would be impractical. In this case, it is possible to increase the peak voltage of the excitation device and excite it rapidly, but in order to establish magnetic flux at a practical speed, a peak voltage that is two orders of magnitude or more higher than the rated field voltage is required, and the excitation capacity becomes extremely large. increases, and the effect of reducing excitation capacity by using superconductivity is lost. Furthermore, in an excitation device with a high peak voltage, the forward resistance also increases because, for example, the thyristor used has a high voltage rating, or the number of series stages increases.
Therefore, even when the generator is constantly operated at a low voltage, the ohmic loss of the excitation circuit increases, and the effect of improving generator efficiency by using superconductivity is impaired.

Purpose of the Invention The present invention connects a superconducting generator in parallel with an adjacent normal-conducting generator, and establishes the field magnetic flux of the superconducting generator by excitation from the armature side of the normal-conducting generator. without increasing the capacity and increasing the ohmic loss of the excitation circuit during continuous operation.
The purpose is to rapidly establish field magnetic flux.

Summary of the Invention The present invention connects a superconducting generator in parallel with an adjacent normal-conducting generator on the armature side, and strengthens the excitation of the normal-conducting generator to supply reactive power to the armature of the superconducting generator. A superconducting power generation system that rapidly establishes field magnetic flux by rapidly reducing the negative induced current flowing in the field circuit of a superconducting generator due to armature reaction using a high resistance connected in series with the field circuit. This is the initial excitation device for the machine.

Embodiments of the Invention FIG. 1 is a basic configuration diagram of the present invention. In the figure, a superconducting generator 1 is connected to an adjacent normal-conducting generator 3 via a shield and a disconnector 2 on the armature side. Both generators have exciter devices 4,5. A parallel high-resistance field resistor 6 is connected to the field circuit of the superconducting generator 1.
and a field switch 7, and in the process of increasing the excitation of the normal-conducting generator 3, the field switch 7 of the superconducting generator is in an open state.

In Fig. 1, after connecting both generators 1 and 3 on the armature side, the output of the excitation device 5 of 3 is increased, but since the field time constant of a normal conduction generator is several seconds, Fig. 2 The field current 8 rapidly increases as shown in curve A of a.
It is possible to launch. As a result, the voltage of the generator 3 is established, and delayed reactive power is supplied from the generator 3 to the generator 1. From the perspective of the generator 1, this corresponds to producing advanced reactive power, so the second field current 9 of the superconducting generator 1 is generated due to the armature reaction.
A current in the negative direction is induced as shown by the curved line a in the figure. As mentioned above, the time constant of the field circuit of the superconducting generator 1 is usually long, several thousand seconds, so this induced current does not decay for a long time, and this acts to keep the field magnetic flux of the generator 1 constant. Therefore, even if the generator 3 is strongly excited, the field magnetic flux of the generator 1 does not rise as shown by curve c in FIG. 2a.

In Fig. 1, if the field switch 7 is opened at this time, a high resistance 6 enters the field circuit in series, the time constant of the field circuit decreases, and the field induced current 9 in the negative direction is generated as shown in Fig. 2b.
The field magnetic flux of the generator 1 quickly attenuates as shown in curve B in Figure 2, and quickly rises as shown in curve C in Figure 2.

This phenomenon can be explained mathematically as follows.

The relational expression among field voltage e _fd , field magnetic flux ψ _fd , field current I _fd , and field circuit resistance R _fd is given by equation (1).

e _fd = d/dtψ _fd +R _fd I _fd ……(1) Here, if the field voltage e _fd is set to zero, equation (1) becomes ψ _fd = −∫R _fd I _fd dt ……(2) . When reactive power is supplied from an adjacent generator, the field current I _fd is negative, and −R _fd I _fd in equation (2) is positive, but in the case of a superconducting generator, the field resistance R _fd is extremely small. Therefore, Equation (2) does not get larger over time. Inserting a high resistance in series in the field circuit
When R _fd is increased, the initial field current I _fd does not change, so the value of -R _fd I _fd becomes extremely large, and equation (2) increases rapidly with time. Of course, the time constant is also small, and I _fd decreases rapidly, but by the time it has decreased, the field magnetic flux ψ _fd has been established. At this point, if the field switch 7 is closed, the field of the generator 3 is returned from the overexcited state, and the field current 8 is weakened, the reactive power supplied from the generator 3 to the generator 1 is reduced. Due to the armature reaction, the field current 9 of the generator 1 shifts in the positive direction as shown by curve B in FIG. 2b.

The higher the resistor 6 is, the faster the magnetic flux will be established, but the voltage immediately after opening the field switch 7 will be higher, so
The maximum resistance value is suppressed according to the dielectric strength of the field winding. However, since the field circuit can withstand a considerable voltage without particularly strengthening the insulation, rapid establishment of field magnetic flux is possible even with a resistance within this limit.

FIG. 3 shows another embodiment of the present invention,
A high resistor 6 is inserted in series in the field circuit of the superconducting generator 1, and a switch 7 is connected in parallel to the resistor 6. When supplying reactive power from the normal conduction generator 3, the switch 7 is opened, the induced negative field current is reduced, and the field magnetic flux is rapidly established, and then the switch 7 is closed again. is the same as in FIG.

Effects of the invention The effects of the invention can be summarized as follows.
That is, since the superconducting generator is excited from the adjacent normal-conducting generator via the armature circuit, no special connecting circuit equipment is required. Since the field voltage of a superconducting generator can be kept at its normal rating, it is possible to rapidly ramp up the field magnetic flux without increasing the capacity of the exciter or the normal ohmic loss. In addition, the resistor inserted into the field circuit for the purpose of reducing the time constant of the field circuit can also be used as a discharge resistor or a protective resistor in case of quenching of superconducting phenomena, which requires additional equipment. This makes it possible to efficiently and rapidly establish field magnetic flux.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2a and b are characteristic diagrams thereof, and FIG. 3 is a block diagram showing another embodiment. 1...Superconducting synchronous generator, 2...Shiya disconnector, 3
... Normal conduction synchronous generator, 4, 5 ... Excitation device, 6
...High resistance field resistor, 7...Field switch, 8,
9...Field current.

Claims (1)

[Claims] 1 A superconducting generator 1 and an excitation device 5 which is provided separately from the superconducting generator 1 and which is controlled to strongly excite from the time when the superconducting generator 1 starts operating until the field magnetic flux is established. During the initial excitation of the superconducting generator 1, the normal-conducting generator 3 equipped with the When the field magnetic flux of the superconducting generator 1 and the high-resistance field resistor 6 connected in series when viewed from the field winding to reduce the magnetic circuit time constant are established, the high-resistance field resistor 6 is connected in series to reduce the magnetic circuit time constant. An initial excitation device for a superconducting generator, comprising a field switch 7 that substantially cuts off the flowing current.