JPH0632760Y2 - Series type instantaneous voltage drop compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a series type instantaneous voltage drop compensator using capacitor energy.

[Prior Art] According to FIG.
VSS) will be explained.

Inverter 5 is connected to AC power source 10 in series with load 7.
Three parallel circuits of the secondary side of the injection transformer 1 on the output side, the bypass switch 2 by the antiparallel connection thyristor, and the backup switch 6 are connected.

The power supply 10 is branched to form a charging circuit for the capacitor 4 by the rectifier 3 and the charging resistor 9, the terminal of the capacitor 4 is connected to the inverter 5, and the output terminal of the inverter 5 is connected to the primary side of the injection transformer 1. It

The capacitor 4 is constantly charged through the rectifier 3,
When an instantaneous voltage drop occurs, the inverter 5 is operated to compensate for the voltage drop via the injection transformer 1. The bypass switch 2 composed of a thyristor
Is turned off by a signal from the control circuit 8, and the operation switching from the bypass switch 2 to the inverter 5 is performed instantaneously.

When the energy stored in the capacitor 4 drops to a certain level, the compensating voltage cannot be generated due to the constraint determined by the turns ratio of the injection transformer 1.
And the bypass switch 2 is turned on at the same time.

In this way, the terminal voltage of the load 7 can be kept constant and stable voltage supply can be performed for a short time.

[Problem] In the VSS, when the capacity is large and the power supply voltage is high (for example, 3.3 kV or 6.6 kV or more), the injection transformer 1 has 2
It is necessary to increase the secondary voltage to some extent to increase the output of the inverter 5.

For this reason, the inverter, the rectifier circuit 3 and the capacitor 4 attached to the inverter have a high voltage, and the device is large due to the insulation, which is expensive.

[Structure of the Invention] The present invention was made in order to solve the above-mentioned problems, in which injection transformers are connected in a cascade and inverters are divided into several groups and installed to use the high-voltage, large-capacity inverters. It tries to solve the problem that occurs in. The inverter used in the present invention has the same configuration as that shown in FIG. 4, but since the inverter is divided into several groups, it has a lower voltage and a smaller capacity than the one installed. Becomes

The present invention will be described below with reference to the embodiment shown in FIG. The same parts as those in FIG. 4 are designated by the same reference numerals.

Between the power supply 10 and the load 7, the secondary sides of the injection transformers 1 ₁ , 1 ₂ , 1 ₃ are connected in series, and the inverters 5 ₁ , 5 ₂ , are connected to the primary sides of the injection transformers 1 ₁ , 1 ₂ , 1 ₃ . 5 ₃ are connected. Injection transformer 1 ₁ , 1 ₂ , 1 ₃
Is shielded to reduce the secondary voltage of surge for the purpose of protecting the inverter.

Bi-Pi Switch 2 ₁ , 2 ₂ , 2 _{3 with} anti-parallel connection thyristor
Are connected so that the secondary sides of the injection transformers 1 ₁ , 1 ₂ , 1 ₃ in series can be short-circuited.

The embodiment shown in FIG. ₂ is the same as the embodiment shown in FIG. 1 in the arrangement of the inverters 5 ₁ , 5 ₂ , 5 ₃ , but the antiparallel connection thyristor switches 2 ₁ , 2 ₂ are connected in parallel. The injection transformers 1 ₁ , 1 ₂ , 1 ₃ in series are connected so that the secondary sides thereof can be short-circuited. By adopting such a parallel connection, a current capacity suitable for the load capacity can be obtained, and the number of installed inverters and injection transformers is not limited to this.

FIG. 3 shows an example of the control circuit of the device of the present invention.

A reference sine wave circuit 13 is installed to the AC power source 10 via a transformer 11 and a secondary side synchronization circuit 12. The reference sine wave circuit 13 generates a sine wave voltage having a constant amplitude according to the synchronization reference pulse of the synchronization circuit 12. A voltage corresponding to the sine wave voltage and the voltage of the power supply 10 is taken out from the transformer 11, input to the compensation voltage amplitude determination circuit 14, and if there is a difference between both input signals, it is integrated by the integration circuit 19. The integration period is performed by logic 18 for 1/4 cycle. Comparator 1
At 6, it is compared with the input signal from the reference triangular wave generation circuit 15,
Inverter base control circuit 17 Inverter 5 ₁ , 5
Control signals for ₂ , 5 ₃ are formed.

When the value obtained by integrating in the integrating circuit 19 exceeds the judgment level, the on / off control circuit 20 causes the thyristor firing signal 21
At the same time, the compensation voltage amplitude determination circuit 14 and the inverter base control circuit 17 are turned on,
5 ₁ , 5 ₂ and 5 ₃ are operated simultaneously. Inverters 5 ₁ , 5 ₂ , 5 ₃ are PWM
It is composed of a control inverter, and the semiconductor switch control signal from the inverter base control circuit 17 is input in parallel to the inverters 5 ₁ , 5 ₂ , 5 ₃ .

[Effects of the Invention] As described above, the present invention has the following effects because the injection transformer is divided into a plurality of parts.

(1) The inverter can be designed with a low-voltage circuit of DC 750 V or less, which simplifies insulation and is economical.

(2) Inverters, etc., can be configured with low voltage circuits, and are not subject to more than high voltage circuits. Therefore, the restrictions on the technical standards such as grounding work (Type 3 work for low voltage) are eased, which simplifies construction. .

(3) Even if the power supply voltage is high, it is not restricted by cascading the injection transformers in multiple stages.

(4) Even if the capacity is large, it can be implemented by a combination of small capacity devices.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 3 shows an example of the control circuit of the device of the present invention. FIG. 4 shows an example of a conventional series type instantaneous voltage drop compensator. 1 ... Injection transformer, 2 ... Bypass switch, 3 ...
Rectifier, 4 ... Capacitor, 5 ... Inverter, 6 ...
Backup switch, 7 ... Load, 8 ... Control circuit,
10 ... AC power supply.

Claims (1)

[Scope of utility model registration request] 1. A device for compensating for an instantaneous voltage drop of a power supply voltage by applying a voltage to the energy stored in a capacitor from the inverter via an injection transformer in series when the power supply voltage instantaneously drops, thereby compensating for the instantaneous voltage drop of the power supply voltage. By-pass switches consisting of anti-parallel connection thyristors, connected in series between the power supply and the load, by connecting the secondary sides of the injection transformers connected in a number corresponding to the number of these inverters in a multi-stage cascade. Is connected in parallel to the secondary side of the injection transformer connected to the multistage cascade, and when the power supply voltage is momentarily lowered, the thyristor firing signal of the antiparallel connection thyristor of the bypass switch is stopped and at the same time the inverters of the several groups are connected. A series-type instantaneous voltage drop compensating device comprising a control circuit for generating a compensation voltage.