JP3290230B2 - Instantaneous voltage drop compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In a cogeneration system that is connected to an electric power system, when a momentary 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 system side. The present invention relates to an instantaneous voltage drop compensator for preventing a load from going down.

[0002]

Conventionally, the instantaneous voltage drop compensating device private power generation facility that the incorporation to the power grid, as shown in FIG. 2, the electric power system side bus B ₁ and the private power generation side bus B ₂ and the semiconductor switch SS
When the power system A momentarily loses power, a backflow is detected and the semiconductor switch SS is operated within one cycle,
The interconnection is instantaneously disconnected to minimize the voltage drop of the generator G (for example, Japanese Patent Application No. 3-44606).

[0003] In addition, the synchronous input of the private power generator to the power system, which is connected to the power system by a semiconductor switch, is performed by controlling the cross current by the semiconductor switch so as to be close to the synchronous state by the cross current. (For example, Japanese Patent Application No. 4-126544).

[0004]

When a private power generator is synchronously inserted into a power system, the phase may be in the worst case before the synchronization, if the phases of the power system and the private generator are not aligned. The withstand voltage design of the semiconductor switch is determined in consideration of its worst state. For example, even in the case of a 6.6 KV system, the withstand voltage between the poles of the semiconductor switch is set to be several tens of KV to 20 KV. Withstand voltage of, for example, 4KV
Then, the number of series becomes 4 to 5, and the whole apparatus is large and the cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has as its object the instantaneous voltage at which the inter-electrode withstand voltage of a semiconductor switch can be made twice or less the system voltage. An object of the present invention is to provide a reduction compensating device.

[0006]

To achieve the above object, according to the Invention The instantaneous voltage drop compensating device in the present invention, a system side
In cooperation with private power generation side such as cogeneration system
Instantaneous with semiconductor switch and its control unit connected between
In the voltage drop compensator, the withstand voltage between the semiconductor switches
There connect the circuit breaker in series with both the semiconductor switches given to using 2 times the line voltage, to the control unit, the instantaneous voltage low
Measuring the rate of change with time of the machining gap voltage by detecting the inter-electrode voltage of the semiconductor switch which is opened and operated by detection below as inter-electrode voltage does not exceed the Gokuma耐voltage by open circuit breaker In addition, the gap between the breaker
A circuit provided with an open command to the circuit breaker in anticipation of a time delay before opening, and then detecting that the circuit breaker has been completely opened, issuing a turn-on command to the semiconductor switch and preparing for rejoining. It is.

[0007]

Operation When a momentary low voltage or the like occurs on the system side, the semiconductor switch is instantaneously opened by the control unit.

[0008] The control unit detects the inter-electrode voltage during open circuit of the semiconductor switch, in anticipation of the operation time delay circuit breaker to measure its change rate, inter-electrode voltage of the semiconductor switch is interpolar
A breaker connected in series is opened by issuing an open command to the breaker so as not to exceed the withstand voltage , so a semiconductor switch with a withstand voltage between poles less than twice the voltage between circuit lines is used. It will not be damaged. When the circuit breaker is completely open
Since closing command is issued to the semiconductor switch semiconductor switch is closed path, re the incorporation is ready by the automatic synchronization dosing device.

[0009]

An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, A is a power system, G ₁ and G ₂ are generators of a private power generation facility, B ₁ is a power system side bus supplying power to the local loads L ₁ and L ₂ , and B ₂ is a local important load L _3, L ₄ private power generation side bus to power, 52B are interconnection circuit breaker for communicating between bus B _1, B _2, 1 instantaneous voltage drop that is provided between the interconnection circuit breaker 52B and bus B ₂ Compensator.

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

The instantaneous voltage drop compensating device 1 includes an interconnection breaker 5
2B and the connecting gas or vacuum circuit breaker CB and the semiconductor switch SS in series between the bus B _2, and its backup switch MC, and a control unit (2-4).

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

3 indicates that the semiconductor switches SS,
A sequence circuit 4 for controlling the circuit breaker CB, the backup switch MC and the like is a gate drive circuit of the semiconductor switch SS connected to the sequence circuit 3. As the semiconductor switch SS, a switch having a withstand voltage between electrodes of twice or less the circuit line voltage 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 (the circuit breakers 52B, CB and the semiconductor switch SS are all closed) and an instantaneous voltage drop occurs on the system A side Then, current is supplied from the generators G ₁ and G ₂ to all loads connected to the power line A side. The detection / arithmetic circuit 2 calculates the current I
Alternatively, a voltage drop or reverse power to the system side is detected, and the semiconductor switch SS is opened instantaneously within one cycle via the circuit 3.4.

As a result, the bus B _{1 is} disconnected and the private generators G ₁ , G ₂ operate in an isolated state, supplying power to the loads L ₃ , L ₄ connected to the bus B ₂ , but the generators G ₁ + G ₂ And the capacity of the load L ₃ + L ₄ generally do not completely coincide with each other, so that the frequency shifts and a phase difference occurs with the system A (a sudden change occurs due to the moment of inertia of the generator). No), the gap voltage V of the semiconductor switch SS increases due to this phase difference.

If the phases are completely opposite, a semiconductor switch
Excess voltage exceeding the withstand voltage between poles is applied between the poles of SS.
Therefore, the circuit breaker CB is opened to prevent this. Grid side
The frequency of ω _s, and the private power generator side and ω _L, the inter-electrode voltage
V beats at a period of sin ((ω _s −ω _L ) / 2) t
You. For _{example, ω s / 2π = 60H Z} , ω L / 2π = 63H Z
If (peripheral speed difference 5%), leaving the beat 1.5 H _Z
Therefore, electrical angle 3 where sin (ω _s −ω _L ) takes a value of 0.5
0 °, ie, 1 / (1.5 * 360) * 30 = 56 mm
Within seconds, if the circuit breaker CB opens,
To be able to keep the voltage between
Become. The detection / arithmetic circuit 2 detects the inter-electrode voltage V of the semiconductor switch SS, and measures the rate of change of the inter-electrode voltage V with respect to time sin ((ω _s −ω _L ) / 2) t .

Based on the measured values, the closing / opening sequence circuit 3 operates the semiconductor device by detecting an instantaneous voltage drop.
As inter-electrode voltage of the switch does not exceed Gokuma耐voltage (less than twice the circuit line voltage) by open circuit breaker CB, breaker
From the opening command to the CB until the gap between the breaker CB is actually opened
In anticipation of the time delay (known value), then exits the opening command to the circuit breaker CB, and then cut off the circuit breaker CB is completely opened
Of the breaker switching instruction auxiliary contact built in the circuit breaker CB
Detecting from the closed state, a closing command is issued to the semiconductor switch SS via the gate drive circuit 4 to bring the semiconductor switch SS into the closed state, and the system is prepared for a synchronous operation with the system A.

As for the method of synchronizing the power system A after the power is restored, the instantaneous voltage drop compensating device 1 does not have an automatic synchronizing function, so if the phase difference and the frequency difference occur as described above, the interconnection is cut off. This is performed by the device 52B and the automatic synchronization 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 completely opened, the circuit breaker CB of the device 1 is turned on.
After that, a re-entry command is issued to the automatic synchronizing device SY, the governor is controlled by the device SY, and the generators G ₁ and G ₂ and the power system A
When the frequency and phase difference have become sufficiently small, the interconnection breaker 52B is closed and reconnected.

The voltage drop time of the power system A is short,
In the case where a double current occurs after the opening and closing of the semiconductor switch and the phase difference does not occur much (that is, before the circuit breaker CB of the device 1 operates), the instantaneous value of the voltage V between the electrodes of the semiconductor switch SS becomes zero. The semiconductor switch SS is closed and the private power generation side is re-joined to the electric power system when the envelope of the voltage waveform between poles crosses zero or when the envelope crosses zero.

[0023]

Since the present invention is configured as described above, the following effects can be obtained.

(1) In order to protect an overvoltage applied between the poles of a semiconductor switch with an open circuit of a circuit breaker in series with the semiconductor switch, for example, even in the case of a 6.6 KV system, a semiconductor element constituting the semiconductor switch Assuming that the withstand voltage of one unit is 4 KV, what was necessary in the conventional case of four in series is only two or three in number,
Although the series circuit breaker is required, 70 to 70
The size can be reduced to 80%.

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

[Brief description of the drawings]

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

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

[Explanation of symbols]

1 ... instantaneous voltage drop compensating device 2 ... detection and calculation circuit 3 ... sequence circuit 4 ... gate drive circuit A ... power system B _1, B ₂ ... bus CB ... breaker G, G _1, G ₂ ... private power generator L ₁ ... L ₄ … in-house load MC… backup switch SS… semiconductor switch SY… automatic synchronous input device 25R ₁ , 25R ₂ … protective relay 52B… interconnection breaker 52G, 52G ₁ , 52G ₂ … generator breaker 52R… Power receiving circuit breaker

Continuation of the front page (72) Inventor Masaaki Ono 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Co., Ltd. (56) References JP-A-60-109726 (JP, A) JP-A-63-917 (JP) , A) Shokai Sho 62-88411 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 3/38 H02H 3/06 H02J 3/42

Claims (1)

(57) [Claims] An instantaneous voltage drop compensator comprising a semiconductor switch connected between a power system side and a private power generation side of a cogeneration system or the like to be connected thereto and a control unit therefor. both withstand voltage given to using 2 times the line voltage connected to the circuit breaker in series with the semiconductor switch, the control unit, the semi <br/> conductor opening was opened and operated by the detection of the instantaneous voltage drop by detecting the inter-electrode voltage of the vessel to measure the rate of change with time of the inter-electrode voltage, as inter-electrode voltage does not exceed the <br/> Gokuma耐voltage by open circuit breaker to breaker Actual from open command
In consideration of the time delay until the gap between the breakers opens , an open command is issued to the circuit breaker, and then it is detected that the circuit breaker has been completely opened, and a closing command is issued to the semiconductor switch to rejoin. An instantaneous voltage drop compensator comprising a circuit provided.