JPS59128715A - Dc breaker - 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] [Field of Application of the Invention] The present invention relates to a DC breaker, and particularly to a commutating switch, a commutating capacitor, a commutating reactor, and a charging resistor.

It relates to direct current and disconnectors with closing switches and non-linear resistances.

[Prior art]

FIG. 1 shows an example in which a DC breaker is applied to a power transmission system. It is composed of a power transmission line 3 and a converter such as an inverse converter (not shown), and a DC breaker 4 is provided at both ends of the power transmission line 3 between a DC reactor L and a disconnector 2.

By the way, commutation capacitor C can be used without using a special charging device.
For example, a so-called reverse current insertion type DC breaker 4, which is charged from a power transmission line 3 of a power transmission system and uses this pre-charged commutation capacitor C to assist in disconnection, uses a commutation switch as shown in the figure. 5. A series connection body of a commutation capacitor C and a commutation reactor L connected in parallel to this commutation switch 5 via a closing switch 6, and a charging resistor r1 provided between this series connection body and the ground. Connected in parallel to switch 5, DC reactor L when cut off.

It is composed of a non-linear resistor R etc. that absorbs and processes the accumulated energy.

In the DC breaker 4 configured as described above, in the steady operation state, the commutation switch 5 is in the closed state, and the closing switch 6 is in the closed state.
is in an open state, so the commutating capacitor C is charged to a voltage equal to the rated voltage of the power transmission line 3. In such a situation, when the line current (load current) is cut off,
When the commutation switch 5 is opened and the closing switch 6 is turned on, the oscillating current of the commutation reactor L and the commutation capacitor C is superimposed on the DC current, which is the line current flowing through the commutation switch 5, and the DC current reaches the zero point. is created, and the commutation switch 5 shreds the current and commutates it to the non-linear resistor.

This commutated current is current-limited and cut off by a non-linear resistor, and finally the cut-off is completed.

By the way, as mentioned above, this type of new system uses the voltage of the power transmission system, that is, the line voltage, so the charging device can be omitted, but it is affected by the line voltage, especially the DC breaker 4.
When transmitting power to a multi-terminal DC transmission system that requires a This is a problem because it is reversed.

In other words, as shown in Figure 2, where the vertical axis represents the line current and line voltage, and the horizontal axis represents time, the relationship between the td line current and line voltage during power flow reversal control and time is shown. Current! The current value ■ remains constant over time, but the line voltage V is 12-! The polarity is reversed from +V to -V from about 200 to 5QQms. DC current one in this case? If the charging resistance of the disconnector is made smaller so that the charging voltage of the commutating capacitor, that is, the terminal voltage v2, follows the change in the line voltage V, the charging voltage of the commutating capacitor becomes lower and it becomes impossible to shut off during power flow reversal control. . Conversely, if the charging resistance is increased to suppress the low charging voltage, the polarity of the commutation capacitor must be reversed with a disconnector after power flow reversal control, and the DC-P disconnector must be reversed. The drawbacks are that the operation time is slow and the operation mechanism is complicated.

[Purpose of the invention]

The present invention was made in view of the above points, and there is no problem even during power flow reversal control where the polarity of the line voltage is reversed.
The purpose of this invention is to provide a DC breaker that enables the following.

[Summary of the invention]

That is, the present invention is characterized in that a thyristor connected in antiparallel is connected in parallel to a series connection body of a commutating capacitor and a commutating reactor.

[Embodiments of the invention]

The present invention will be explained below based on the illustrated embodiments. FIG. 3 shows an embodiment of the invention. Note that parts that are the same as those in the conventional model are given the same reference numerals, and therefore their explanations will be omitted. In this embodiment, a thyristor 7.8 is connected in parallel and anti-parallel to a series connection body of a commutating capacitor C and a commutating reactor L.
connected. By doing this, it became possible to electrically switch the polarity of the commutating capacitor C in a short time, making it possible to disconnect without any problems even during power flow reversal control when the line voltage polarity is reversed. A DC breaker 4a can be obtained.

In other words, a thyristor 7 is connected in parallel to the series connection of the commutating capacitor C and the commutating reactor L, and is turned on when the terminal voltage V of the commutating capacitor C is positive (+) with respect to the ground.
An anti-parallel connection body was connected to the thyristor 8 which turns on when the voltage is negative (-). By doing this, the conductor line voltage V
has positive polarity with respect to the ground, the change over time of the current waveform flowing through the thyristor 7 and the terminal voltage V of the commutating capacitor C when the gate of the thyristor 7 is turned on at the time when the line voltage V is reversed. The fourth characteristic is shown.
As shown in the figure, a half-wave current i flows through the thyristor 7 (see FIG. 3) from time t when the line voltage is reversed, and the terminal voltage V of the commutating capacitor C. The polarity is instantaneously reversed from +V to -■. This terminal voltage V can be prevented from decreasing within the reversal control time during power flow reversal control by selecting a large value for the charging resistor, so the vertical axis shows the terminal voltage V of the commutation capacitor and the line voltage. As shown in Figure 5, where the horizontal axis shows the terminal voltage V of the commutating capacitor and the change characteristics of the line voltage over time, the commutating capacitor changes at time t when the line voltage V reverses. terminal voltage V. As shown by the dotted line in the figure, the polarity is instantaneously reversed without its magnitude decreasing, and after the reversal, the commutating capacitor is charged with the negative line voltage -V. In this case, the time required to reverse the polarity of the commutating capacitor is determined by the values of the commutating capacitor and commutating reactor, but it can generally be achieved in l m 3 or less, so it can be cut off without any problem even during power flow reversal control. . In this embodiment, the case where the line voltage V is reversed from positive to negative has been explained, but the same applies to the case where the line voltage V is reversed from negative to positive. In this case, the gate of thyristor 8 (see Fig. 3) should be turned on. The terminal voltage of the commutating capacitor is V. can be reversed from negative to positive, and similar effects can be achieved.

Another embodiment of the invention is shown in FIG.

In this embodiment, considering high-speed charging such as opening and closing of the commutation switch 5, a charging resistor r with a small resistance resistance is used as the charging resistor. using
A disconnector 9 is provided on the ground side of the commutating capacitor C to prevent a drop in the charging voltage of the commutating capacitor C during power flow reversal control. By doing this, the disconnector 9 is opened before the power flow reversal control, the thyristor 7 or 8 is operated during the power flow reversal control to reverse the polarity of the commutation capacitor C, and the disconnector 9 is closed after the polarity is reversed. If the commutating capacitor C is charged with the line voltage, the commutating capacitor C is disconnected from the power transmission line during power flow reversal control, so it is possible to prevent the charging voltage of the commutating capacitor C from decreasing, and high-speed charging is possible. It becomes possible.

FIG. 7 shows yet another embodiment of the invention. In this embodiment, the charging resistor is a large charging resistor r! and a charging resistor r1 with a small resistance value, and a disconnector 9 is provided at both ends of the charging resistor 2 with a large resistance value.By doing this, the disconnector 9 is always open and the commutation switch If high-speed charging is required, such as when opening/closing the charging resistor 5, the new circuit device 9 can be used to perform high-speed charging with a charging resistor rl having a low resistance value.

Note that during normal power flow reversal control, the disconnector 9 is kept open.

FIG. 8 shows yet another embodiment of the invention. In this embodiment, the commutation reactor L for commutation cut-off is not used as a discharge circuit accelerator for switching the commutation capacitor C, and a reactor Ls that can control the polarity reversal time of the commutation capacitor C is provided separately. This is to compensate for the drawback that the polarity reversal time of the commutating capacitor C cannot be arbitrarily selected because the value of the commutating reactor L is normally determined in relation to the performance of the commutating switch 5. The polarity reversal time can be selected.

FIG. 9 shows yet another embodiment of the invention. In this embodiment, a commutation reactor L for commutation cutoff and a glue handle Lg for switching the commutating capacitor are provided in series in the switching discharge circuit of the commutating capacitor C. By doing this, the oscillation frequency of the switching discharge circuit of the commutation capacitor C can be lowered by using the commutation reactor L, so the current flowing through the thyristor 7.8 during power flow reversal control can be reduced. The value of the rear (9) vector Ltr for switching the commutation capacitor can also be reduced.

〔Effect of the invention〕

As described above, in the present invention, the polarity of the commutating capacitor can be switched in a short time, so that the polarity can be switched in a short time, and even during power flow reversal control when the polarity of the line voltage is reversed, it can be cut off without any problem. Therefore, there is no problem even during power flow reversal control where the polarity of the line voltage is reversed. Ffr
It is possible to obtain a DC breaker that enables this.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a conventional DC breaker, and Fig. 2 is a diagram of changes in line current and line voltage over time during power flow reversal control of a power transmission line in which a DC breaker is used.
Fig. 3 is a circuit configuration diagram of an embodiment of the DC breaker of the present invention, and Fig. 4 is a current waveform flowing through a thyristor during power flow reversal control and time variation characteristics of the terminal voltage of a commutating capacitor during power flow reversal control of the same embodiment. Figure 5 is a time-varying characteristic diagram of the commutating capacitor terminal voltage and line voltage during power flow reversal control according to one embodiment, and Figure 6 is another embodiment of the DC breaker according to the present invention (10). FIG. 7 is a circuit diagram of still another embodiment of the DC breaker of the present invention, FIG. 8 is a circuit diagram of still another embodiment of the DC breaker of the present invention, and FIG. 9 is a circuit diagram of still another embodiment of the DC breaker of the present invention. FIG. 2 is a circuit configuration diagram of still another embodiment of the DC breaker of the present invention. 3...Power transmission line, 4a...DC disconnector, 5...
Commutation switch, 6... Closing switch, 7, 8... Thyristor, 9... Disconnector, C... Commutation capacitor,
L... Commutation reactor, L6... DC reactor,
LI+...React (11)

Claims (1)

[Claims] 1. A commutation switch connected to a power transmission line of a power transmission system having a DC reactor and opening the power transmission line when the power transmission line is cut off, a commutation capacitor connected in parallel to the commutation switch via a closing switch, and A series connection body of commutation reactors, a charging resistor provided between the series connection body and the ground, and a non-linear resistor connected in parallel to the commutation switch and absorbing and processing the energy accumulated in the DC reactor. 1. A DC breaker comprising: a thyristor connected in antiparallel in parallel to the series connection body of the commutating capacitor and commutating reactor.