JPH06245389A - Instantaneous voltage drop compensator - Google Patents

Abstract

PURPOSE:To use a semiconductor switch in which a voltage between poles is twice or less as large as a system voltage. CONSTITUTION:An instantaneous voltage drop compensator 1 connected between a system A side and a non-utility generator G side uses a semiconductor switch SS in which a voltage between poles is twice or less as large as a circuit voltage, and connects in series with a breaker CB. When the system A side is instantaneously power interrupted to open the switch SS, the voltage between the poles is detected by a detecting.operator 2, a ratio to its time is measured, an open command is output from a sequencer 3 to the breaker CB by expecting a time delay until the breaker CB is actually opened so as not to exceed the voltage between the poles of the switch, thereby preventing damage of the switch SS having twice or less of the voltage between the poles as large as a circuit voltage. Then, complete opening of the breaker SS is detected, a close command is output to the switch SS for next connection.

Description

Detailed Description of the Invention

[0001]

[Industrial application] In a cogeneration system that is interconnected to the power grid, if an instantaneous voltage drop occurs on the power grid side, the generator may go down or the voltage may drop due to reverse power from the private power generation side to the power grid side. The present invention relates to an instantaneous voltage drop compensating device for preventing a load from dropping.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, a device for compensating an instantaneous voltage drop of a private power generation facility that is also incorporated in a power system connects a power system side bus B ₁ and a private power generation side bus B ₂ to a semiconductor switch SS.
When the power system A has a momentary power failure, the reverse current is detected and the semiconductor switch SS is operated within 1 cycle,
The interconnection is instantaneously disconnected to minimize the voltage drop of the generator G (for example, Japanese Patent Application No. 3-44606).

In addition, when the private generator connected to such an electric power system by a semiconductor switch is synchronously input to the electric power system, the semiconductor switch is used to suppress the cross current and bring the generator closer to the synchronous by the cross current. At high speed (for example, Japanese Patent Application No. 4-126544).

[0004]

When the private generator is synchronized with the power system, the worst case may occur when the phases of the power system and the private generator are not aligned before the synchronization. Since the withstand voltage design of is determined in consideration of the worst state, for example, even in the case of the 6.6 KV system, the inter-electrode withstand voltage of the semiconductor switch is set to 10 KV to 20 KV. Withstand voltage is 4KV
Then, the number of series is 4 to 5, which makes the entire apparatus large and costly.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an instantaneous voltage capable of making the inter-electrode withstand voltage of a semiconductor switch to be twice or less the system voltage. It is to provide a drop compensation device.

[0006]

In order to achieve the above object, an instantaneous voltage drop compensating device according to the present invention has a semiconductor switch connected between a system side and a private power generation side, in which a voltage between contacts is a circuit line. Use a voltage that is less than twice the inter-terminal voltage and connect a circuit breaker in series with this semiconductor switch, and detect the inter-electrode voltage when the semiconductor switch is open in the control section and measure the rate of change with respect to that time. In anticipation of the time delay until the circuit breaker actually opens, issue an open command to the circuit breaker so as not to exceed the voltage across the semiconductor switch and then detect that the circuit breaker has completely opened It is provided with a circuit for issuing a closing command to prepare for re-joining.

[0007]

[Operation] When an instantaneous low voltage or the like occurs on the system side, the semiconductor switch is instantly opened by the control unit.

The control unit detects the voltage between contacts of the semiconductor switch when the semiconductor switch is opened, measures the rate of change, and anticipates a delay in the operating time of the circuit breaker so as not to exceed the voltage between contacts of the semiconductor switch. Since a circuit breaker connected in series is opened by issuing an open command, the semiconductor switch will not be damaged even if the voltage between contacts is less than twice the voltage between circuit lines. When the circuit breaker is completely opened, a closing command is issued and the semiconductor switch is opened, so that the automatic synchronous closing device can be used together.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, A is an electric power system, G ₁ and G ₂ are generators of a private power generation facility, B ₁ is a power system side bus line that supplies power to local loads L ₁ and L ₂ , and B ₂ is an important internal load L. ₃ and L ₄ , power generating side busbars for supplying power, 52B is an interconnecting circuit breaker that connects between busbars B ₁ and B ₂ , and 1 is an instantaneous voltage drop provided between the interconnecting circuit breaker 52B and the busbar B _2. Compensation device.

25R ₁ is a protective relay for controlling the power receiving breaker 52R and the automatic synchronizing device SY of the generator by using the voltage and current signals of the power system A, 25R ₂ is the voltage of the bus B ₁ ,
It is a protective relay that controls the interconnection breaker 52B from the current signal.

The instantaneous voltage drop compensator 1 includes an interconnection breaker 5
2B and a busbar B ₂ which are connected in series with a gas or vacuum circuit breaker CB, a semiconductor switch SS, a backup switch MC thereof, and control units (2 to 4).

Reference numeral ₂ denotes the voltage V and current I of the semiconductor switch from the voltage on the interconnection circuit breaker 52B side of the circuit breaker CB, the current signals Vac1 and Iac and the voltage signal Vac2 of the bus B2 side of the semiconductor switch SS. A detection / calculation circuit that detects and calculates a phase difference, a frequency difference, a change rate of the voltage V between electrodes, an electric power W, and a reactive power Var.

3, the semiconductor switch SS,
A sequence circuit 4 for controlling the circuit breaker CB, the backup switch MC, etc. is a gate drive circuit for the semiconductor switch SS connected to the sequence circuit 3. As the semiconductor switch SS, one having a withstand voltage of not more than twice the voltage between circuit lines is used.

Next, the operation of this embodiment will be described.

When the private generators G ₁ and G ₂ are operating in parallel with the power system A (when the circuit breakers 52B and CB and the semiconductor switch SS are all closed), an instantaneous voltage drop occurs on the system A side. , The electric current is supplied from the generators G ₁ and G ₂ to all the loads connected to the side of the electric system A. The detection / arithmetic circuit 2 uses this current I
Alternatively, the voltage drop or the reverse power to the system side is detected and the semiconductor switch SS is opened instantly within one cycle through the circuit 3.4.

As a result, the bus B _{1 is} disconnected, the private generators G ₁ and G ₂ are operated independently, and power is supplied to the loads L ₃ and L ₄ connected to the bus B ₂ , but the generators G ₁ + G ₂ In general, the output of and the capacity of load L ₃ + L ₄ do not completely match, so the frequency shifts and a phase difference with system A occurs (there is a moment of inertia of the generator, so a sudden change occurs. No), the inter-electrode voltage V of the semiconductor switch SS increases due to this phase difference.

The detection / calculation circuit 2 is the semiconductor switch SS.
The inter-electrode voltage V is detected and the rate of change over time is measured.

Based on this measured value, the sequence circuit 3 expects a time delay from the opening command to the circuit breaker CB until the gap between the circuit breakers CB is actually opened, and the breakdown voltage between the semiconductor switches SS (circuit line The open command is issued to the circuit breaker CB so that the voltage does not exceed twice the voltage). Next, it is detected that the circuit breaker CB is completely opened, and the semiconductor switch SS is detected via the circuits 3 and 4.
In order to prepare for the synchronous operation with system A, a closing command is issued to switch to the closing state.

Regarding the method of synchronizing the power system A after the power is restored, the instantaneous voltage drop compensating device 1 does not have the automatic synchronizing function, so if the phase difference and the frequency difference occur as described above, the interconnection is cut off. 52B and the automatic synchronizing input device SY.

In this case, the instantaneous voltage drop compensator 1 once issues an open command to the interconnection breaker 52B, and the breaker 52B is opened.
When the circuit is completely opened, the circuit breaker CB of the device 1 is turned on.
After that, the resynchronization command is issued to the automatic synchronizing injection device SY, and the governor is controlled by the device SY to control the generators G ₁ and G ₂ and the power system A.
When the frequency difference and the phase difference become sufficiently small, the interconnection breaker 52B is closed and reconnected.

The voltage drop time of the power system A is short,
If a double voltage is applied after the opening of the semiconductor switch and before the phase difference is generated (that is, before the circuit breaker CB of the device 1 is activated), the instantaneous value of the inter-electrode voltage V of the semiconductor switch SS becomes 0. The semiconductor switch SS is closed and the private power generation side is re-introduced into the power system when the envelope of the voltage waveform between the poles crosses zero.

[0023]

Since the present invention is configured as described above, it has the following effects.

(1) In order to protect the overvoltage applied between the poles of the semiconductor switch by the open circuit of the circuit breaker in series with the semiconductor switch, for example, a semiconductor element constituting the semiconductor switch even in the case of the 6.6 KV system. Assuming that one withstand voltage is 4 KV, only two or three were required in the past, four in series,
Although the series circuit breaker is required, the total device is 70-
It is possible to reduce the size to 80%.

(2) Since the number of semiconductor elements in series is small, the loss generated in the semiconductor switch part can be reduced by 50 to 60%.

[Brief description of drawings]

FIG. 1 is a single line wiring diagram showing an embodiment of the present invention.

FIG. 2 is a conventional single-line wiring diagram.

[Explanation of symbols]

1 ... Instantaneous voltage drop compensator 2 ... Detection / arithmetic circuit 3 ... Sequence circuit 4 ... Gate drive circuit A ... Power system B ₁ , B ₂ ... Bus CB ... Circuit breaker G, G ₁ , G ₂ ... Private generator L ₁ ~ L ₄ ... load on the premises MC ... backup switch SS ... semiconductor switch SY ... automatic synchronization closing device 25R ₁ , 25R ₂ ... protective relay 52B ... interconnection breaker 52G, 52G ₁ , 52G ₂ ... generator breaker 52R ... Power receiving circuit breaker

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[Procedure amendment]

[Submission date] March 17, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Ono 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Incorporated company, Meidensha

Claims (1)

[Claims] 1. An instantaneous voltage drop compensating device comprising a semiconductor switch connected between a system side and an in-house power generation side such as a cogeneration system, which is connected to the system side, and a control unit thereof.
Use a semiconductor switch with a voltage between contacts less than twice the voltage between circuit lines, and connect a circuit breaker in series with this semiconductor switch to control the voltage between contacts when the semiconductor switch is open. After detecting and measuring the rate of change with respect to that time, anticipating the time delay until the circuit breaker actually opens, issue an open command to the circuit breaker so as not to exceed the voltage between contacts of the semiconductor switch, and then the circuit breaker will be completely opened. An instantaneous voltage drop compensating device, characterized in that it is provided with a circuit that detects that a circuit has been opened and issues a closing command to the semiconductor switch to prepare for reconnection.