JPH065982B2 - Switchgear - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a switchgear, and more particularly to a switchgear for intermittently controlling an alternating current with respect to an alternating current load using a semiconductor switch.

[Prior art]

FIG. 1 is a circuit diagram of a conventional capacitor switchgear for reactive power control using a mechanical switch, for example, as shown in FIG. 11 of P258 of the magazine “Electrical Computing” (October 1969 issue). In the figure, 1 is an AC power supply bus bar, 2
a to 2c are switches, 3a to 3c are switches 2a to
A capacitor as an AC load connected to the AC power source bus 1 via 2c.

Next, the operation will be described. In FIG. 1, when the power factor of the AC power bus 1 decreases, the switches 2a to 2c are sequentially turned on, and the capacitors 3a to 3 are turned on according to the degree of the power factor.
Input c. In this case, since a rush current of 6 to 10 times the rated current flows depending on the closing phase of the switches 2a to 2c, the voltage of the AC power bus 1 is largely distorted and other devices connected to the same bus (for example, Thyristor converter, etc.) is adversely affected. Therefore, the unit bank capacity of the capacitor cannot be increased so much, and as a result, the number of capacitor banks increases, resulting in a large arrangement space and a high price. Further, when the switching frequency is high, there is a problem that the life of the switches 2a to 2c and the capacitors 3a to 3c is shortened due to a transient phenomenon when the capacitors are opened and closed.

For this reason, as shown in FIG. 2, for applications with a high switching frequency, instead of the switches 3a to 3c shown in FIG. 1, thyristor switches 4a to 4 composed of antiparallel circuits of thyristors are used.
A capacitor switching device (for example, disclosed in Japanese Patent Publication No. 50-40218) that opens and closes the circuits of the capacitors 3a to 3c by using c is applied.

FIG. 3 uses the thyristor switch 4 shown in FIG.
The basic circuit diagram when opening and closing the capacitor 3 is shown.

Next, the operation of the basic circuit will be described with reference to the waveform chart of FIG. FIG. 4 shows that the thyristor switch is O before time t ₁ .
The state of being in the FF state is shown. As shown in FIG. 4 (b), the voltage E equal to the AC power supply voltage shown in FIG. 4 (a) is applied to the thyristor switch 4.

When the load capacitor 3 is turned on, the thyristor switch 4 is turned on in synchronism when the voltage across the thyristor switch 4 becomes 0 in order to reduce the input current at the time of turning on the control output from a control circuit (not shown). It is controlled by a signal. That is, in FIG. 4, at time t ₁ , the thyristor switch 4
Turns on. In this case, the current shown in FIG. 4 (c) flows through the capacitor.

Next, when the thyristor switch 4 is turned off, the gate ignition signal to the thyristor may be turned off.
As shown in FIG. 6C, at time t ₂ , the thyristor switch is turned off when the capacitor current reaches 0. This time t ₂ coincides with the peak phase of the power supply voltage E, and accordingly, the capacitor 3 is charged to the peak value E of the power supply voltage at time t ₂ .

When the thyristor switch is turned off at time t ₂ as described above, the voltage E of the AC voltage source 1 is superimposed on the capacitor voltage E because the voltage E remains charged in the capacitor 3, and the voltage of the AC voltage source 1 is superimposed on the capacitor voltage E, as shown in FIG. A voltage of 2E is applied to the thyristor switch 2 as shown after time t _{2 in} b). Therefore, as a thyristor element, at least 2
A breakdown voltage of E to 3E is required.

On the other hand, the thyristor switch 4 is kept ON during the period in which the capacitor 3 is turned on, which causes a large electric loss due to the forward voltage drop of the thyristor 4, resulting in a reduction in efficiency and a large cooling device, which makes the device expensive. Becomes

Since the conventional capacitor switchgear is configured as described above, the mechanical switch of FIG. 1 cannot be used in places with frequent switching, and the power supply due to the inrush current when the capacitor is turned on is used. Due to voltage distortion, the unit capacity of the capacitor bank cannot be increased. Further, when the thyristor switch shown in FIG. 2 is used, there is a drawback that the forward voltage drop of the thyristor causes a large electric loss and a thyristor switch is required for each capacitor bank, which makes the device expensive.

[Outline of Invention]

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional ones.After the capacitor is turned on by the thyristor switch, the thyristor switch is bypassed by a switch, and further By providing a single thyristor switch, it is possible to provide a compact and inexpensive capacitor switchgear with little electric loss. The present invention also provides a capacitor switching device capable of suppressing overvoltage by connecting a non-linear resistance element in parallel with the thyristor switch.

Example of Invention

A first embodiment of the present invention will be described below with reference to FIG. 5 in which the same parts as those in FIG. In FIG. 5, 5 is a thyristor switch commonly used for a plurality of capacitor banks 3a to 3c, and 6a to 6c are provided between the load side end of the thyristor switch 4 and the power source side ends of the capacitors 3a to 3c. This is a switch for switching the thyristor switch.

The first embodiment of the present invention has the above-mentioned configuration, and its operation will be described below with reference to the waveform chart of FIG. Fifth
In the figure, when the capacitor banks 3a to 3c are disconnected from the power source 1, the switches 2a to 2c and 6a to 6 are shown.
All c are turned off, and the thyristor switch 5 is also turned off.

When inserting the capacitor bank 3a into the AC voltage line 1, first, as shown in FIG.
With the switch off, the switch 6a is turned on at time t ₁ . In this case, when the voltage equal to the supply voltage E in the thyristor steel Tutsi 5 as shown in FIG. 7 (d) is applied, in yet time t _2, the voltage applied to the thyristor Sui Tutsi it has decreased to 0, not The thyristor switch 5 is turned on by the control signal output from the illustrated control circuit, and the capacitor bank 3a is turned on to the AC voltage line 1 without inrush current. When the capacitor bank 3a is turned on, FIG.
(e), the ON the switch 2a at time t _3, commutated the current flowing through the thyristor Sui Tutsi 5 as shown in FIG. 7 (f) to switch 2a. Thereafter the thyristor Sui Tutsi 5 to OFF further to OFF switch 6a at time t _4.

Next, when the capacitor bank 3b is turned on, the voltage applied to the thyristor switch 5 becomes 0 after the switch 6b is turned on while the thyristor switch 5 is turned off in the same manner as when the capacitor bank 3a is turned on. At that time, the thyristor switch 5 is turned on, and the capacitor bank 3b is connected to the AC voltage line 1 without an inrush current. When the capacitor bank 3b is turned on, the switch 2b is turned on, and the current flowing in the thyristor switch 5 is switched on.
Commute to b. Then turn off thyristor switch 5.
Then, the switch 6b is turned off.

When the capacitor bank 3c is turned on, the capacitor bank can be turned on by the thyristor switch 5 in the same order as above.

In this way, after turning on the capacitor, the thyristor switch 5
The thyristor switch may be rated for a short time and electrical loss is small because the inrush current can be prevented and the closing control allows the current to flow to the switches 2a to 2c.

Next, the operation when opening the capacitor bank 3c will be described below.

In Figure 8 (b), to ON thyristor Sui Tutsi 5 while the turns ON switch 6c at time t _1. To OFF in the subsequent switch 2c time t ₂ as shown in FIG. 8 (e), Figure 8 (c) and the current flowing in the switch 2c as shown in the the thyristor Sui Tutsi 5 (f) Commute. After that, when the gate signal of the thyristor switch 5 is turned off, as shown in FIG. 8 (c), the thyristor switch 5 becomes t ₃ when the current flowing through the thyristor switch becomes zero.
Turns off to block the circuit current. At this time, since the capacitor 3c is charged to the peak value E of the power supply voltage, the voltage of 2E is applied to the thyristor switch 5. Then OFF the switch 6c at time t _4, completely disconnect the capacitor down bank 3c from AC voltage line 1.

Next, when opening the capacitor bank 3b, first, similarly to when opening the capacitor bank 3c, first, the switch 6b is turned on and the thyristor switch 5 is turned on.
To After that, switch 2b is turned off and switch 2b
The current flowing in the thyristor is commutated to the thyristor switch 5. After that, turn off the gate signal of thyristor switch 5.
In this case, the thyristor switch 5 is turned off when the current flowing through the thyristor switch reaches 0, blocking the circuit current. After that, the switch 6b is turned off to completely disconnect the capacitor bank 3b from the AC voltage line 1.

The same applies when the capacitor bank 3a is opened from the AC voltage line 1.

As described above, when the capacitor banks 3a to 3c are opened and closed, the thyristor switch 5 is always used for contactless opening and closing, and the opening and closing can be performed without a transient phenomenon such as inrush current. At this time, no voltage distortion occurs on the AC voltage line 1 (power supply side). Further, since there is no rush current into the capacitor when the capacitor is turned on, the life of the capacitor does not deteriorate even if the switching frequency is high. Furthermore, when the switches 2a to 2c and 6a to 6c are opened and closed, since the current is 0 or there is a circuit that can bypass the current, there is an effect that the life of the switches does not deteriorate. . Also, since the switch does not require current switching capability,
It can also be used as a disconnector.

FIG. 6 is a circuit diagram showing a second embodiment of the present invention in which the same parts as those in FIG. In FIG. 6, reference numeral 7 is a non-linear resistor connected in parallel to the thyristor switch 5.

The operation of closing the capacitor banks 3a to 3c in FIG. 6 is exactly the same as that in FIG. However, in order to free the capacitor 3 a to 3 c, in the immediately after thyristor Sui Tutsi 5 has decreased to OFF at time _{t 3} of Figure 8 the embodiment of FIG. 5, the peak value of the capacitor 3 a to 3 c is a power supply voltage E
Since the thyristor switch 5 is charged up to this point, a voltage of 2E is applied to the thyristor switch 5 as shown by the dotted line in FIG.
Was necessary.

However, since the non-linear resistor 7 is connected in parallel with the thyristor switch 5 in the second embodiment shown in FIG.
As shown by the solid line in (d), the thyristor switch 5 is turned off.
The applied voltage thereafter is limited to a peak value of about the power supply voltage E by the nonlinear resistance 7.

No voltage is applied to the non-linear resistance 7 at all times, and it is applied only for a short period of time when the thyristor switch 5 is turned on or off. Therefore, the energy consumption inside the resistance is small, and , Thyristor switch 5
It is possible to limit the voltage applied to V to about E for a short period of time.

By connecting the non-linear resistor 7 in parallel with the thyristor switch 5 in this way, the voltage applied to the thyristor switch 5 can be limited, and the switchgear is more inexpensive than the first embodiment. Can be provided.

In the above embodiment, the case of opening and closing the capacitor bank is shown, but the load may be any AC load regardless of the capacitor. Further, although the above-mentioned embodiment shows the case of a switch or a switch, it may be a switch or a switch. Further, in the above embodiment, the case of the thyristor switch constituted by the antiparallel circuit of the thyristor is shown, but a GTO thyristor or other semiconductor switch element may be used, and in any of these cases, the same effect as the above embodiment can be obtained. .

[Effects of the Invention] As described above, according to the present invention, a single thyristor switch and a switch for switching thyristor switches are connected in common to each capacitor bank in parallel with the switches of the plurality of capacitor banks. Since all capacitor banks are opened and closed without contact using a thyristor switch, distortion of the power supply voltage when the capacitors are turned on can be eliminated and the life of the capacitors and switches will not be affected even if the frequency of opening and closing is high. Therefore, there is an effect that a switchgear with little electric loss during energization can be obtained at low cost. Further, since the nonlinear resistance element is provided in parallel with the thyristor switch, when the thyristor switch is turned off, the charging voltage of the capacitor bank is rapidly discharged through the nonlinear resistance element. As a result, the effect of suppressing the overvoltage application to the thyristor switch can be obtained.

[Brief description of drawings]

1 is a circuit diagram showing a conventional capacitor switchgear using a mechanical switch, FIG. 2 is a circuit diagram showing a conventional capacitor switchgear using a thyristor switch for each capacitor bank, and FIG. 3 is a thyristor. FIG. 4 is a circuit diagram showing the basic operation of a capacitor switchgear by a switch, FIG. 4 is a waveform diagram showing the operation waveforms of each part of the circuit of FIG. 3, and FIG. FIG. 6 is a circuit diagram showing a second embodiment of the switchgear according to the present invention, FIG. 7 is a waveform diagram showing the operation of the first embodiment shown in FIG. 5 when the capacitor is turned on, and FIG. FIG. 9 is a waveform diagram showing the operation when the capacitor is opened in the first embodiment shown in FIG. 9, and FIG. 9 is a waveform diagram showing the operation when the capacitor is opened in the second embodiment shown in FIG. 1 ... AC power bus, 2, 2a-2c ... Switch, 3, 3a
3c ... a capacitor bank, 4,4a-4c ... thyristor switch, 5 ... thyristor switch, 6a-6c ... thyristor switch switching switch, 7 ... non-linear resistance. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor switch, which is connected to an AC power supply bus and is closed in synchronization with an AC voltage phase in which no inrush current flows, and a load connected in series to a connection path of a plurality of loads to the AC power supply bus. Is applied to the AC power supply busbar, the semiconductor switch is closed and the load is turned on through the semiconductor switch, and when the load is disconnected from the AC power supply busbar, the semiconductor switch is closed. When the first switch to be opened and the load side of the semiconductor switch and the power source side of the load are respectively connected and the load is applied to the AC power source bus, the switch is preliminarily closed. The semiconductor switch and the first switch are closed and subsequently opened after the semiconductor switch is opened. When disconnecting the load from the AC power bus, the semiconductor switch is opened after the first switch is opened. A second switch which is opened after the load current flowing through the switch is blocked by the opening of the semiconductor switch and is connected in parallel to the semiconductor switch so as to discharge the charge of the load when the semiconductor switch is turned off. A switchgear having a non-linear resistance element.