JP3817921B2 - Grid interconnection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention disconnects the bus of the private power generation facility linked to the power system from the power receiving bus connected to the power system when a failure such as a voltage drop or power failure of the power system occurs, and the failure is restored The present invention relates to a grid interconnection device that is reconnected to a power receiving bus and secures load feeding of the bus of a private power generation facility.
[0002]
[Prior art]
Conventionally, for high-voltage or extra-high-voltage power receiving facilities such as factories and buildings, a private power generation facility such as a cogeneration facility is connected to a commercial power system and connected to the bus of this power generation facility (self-generated bus). The so-called important load power supply is duplicated.
[0003]
The grid interconnection in this case is conventionally performed using a grid interconnection apparatus shown in the single-line system diagram of FIG.
[0004]
Then, the power receiving bus 4 is connected to the commercial system power supply 1 via the circuit breaker 2 and the transformer 3, and the general loads 7a of the feeders 6a,..., 6n are connected from the power receiving bus 4 to the circuit breakers 5a,. .., 7n are fed with the system power supply 1.
[0005]
Also, a generator (cogeneration generator) 8 serving as a private power generation facility is connected to a bus (self-generated bus) 10 of the private power generation facility via a circuit breaker 9, and this bus 10 is a mechanical bus such as a circuit breaker. It is connected to the power receiving bus 4 via a contact switch 11.
[0006]
Then, by means of sequence control of a control unit (not shown), the switch 11 is normally turned on and closed in synchronization with the system power supply 1, and the generator 8 is connected to the power system.
[0007]
Furthermore, important loads 14a,..., 14n of feeders 13a,..., 13n are connected to the self-generated bus 10 via circuit breakers 12a,..., 12n, and the system power supply 1 and the load 14a,. The AC output of the generator 8 is fed, and the feeding of each important load 14a, ..., 14n is duplicated.
[0008]
When the output of the generator 8 is reduced due to the duplexing, the important loads 14a,..., 14n are supplied with power from the system power supply 1, and stable supply of the important loads 14a,.
[0009]
[Problems to be solved by the invention]
In the case of the conventional apparatus shown in FIG. 5, when a voltage drop such as an instantaneous voltage drop due to lightning damage or a fault such as a ground fault or a short-circuit power failure occurs in the power system or the power receiving bus 4, the switch 11 is detected based on the detection. Even if an attempt is made to secure power supply for the important loads 14a,..., 14n by disconnecting the self-generated bus 10 from the power receiving bus 4 and disconnecting the self-generated bus 10 from the power receiving bus 4, it takes time to disconnect the mechanical switch 11; It cannot be disconnected instantly.
[0010]
And since overcurrent flows from the generator 8 through the switch 11 to the failure point during that time, even if the generator 8 does not stop, the voltage of the self-generated bus 10 decreases, and the important loads 14a,. It causes accidents such as 14n malfunction and data erasure.
[0011]
Further, when the overcurrent is extremely large and greatly exceeds the capacity of the generator 8, the generator 8 stops due to the overload, leading to a situation where the critical loads 14a,. .
[0012]
Therefore, as shown in FIG. 6, a series circuit of a switch 11 and a rectifier bridge circuit 15 for high-speed interruption with an overcurrent limiting function is provided in the connection path of the buses 4 and 10, and when the failure occurs It is conceivable to secure the power supply of the important loads 14a,..., 14n by preventing the voltage drop and power failure of the private bus 10 by limiting the current of the bridge circuit 15 and cutting off at high speed.
[0013]
The bridge circuit 15 is formed by bridge-connecting two-arm thyristors 16 a and 16 b as control rectifier elements and two-arm diodes 17 a and 17 b, and is connected to the power receiving bus 4 via the switch 11. between the AC terminals AC1 and the other AC terminal AC ₂ connected to the private power-generating system bus 10, the anode of the thyristor 16a, cathode, one of the DC terminals DC _1, the cathode of the diode 17a, the anode of the series circuit, a thyristor the cathode of 16b, the anode, the other DC terminal DC _2, the anode of the diode 17b, the cathode of the series circuit provided in parallel is formed.
Furthermore, a current limiting reactor 18 is provided between the DC terminals DC ₁ and DC ₂ .
The thyristors 16a and 16b are turned on during the interconnection operation.
[0014]
At this time, an alternating current indicated by a solid line (1) and a broken line (2) in FIG. 7 flows through the bridge circuit 15, and this alternating current flows in one direction from the direct current terminal DC ₁ to the direct current terminal DC _2. The current that flows is a direct current.
[0015]
Further, since the capacity of the reactor 18 is set so that the discharge time constant becomes sufficiently large and the discharge takes time, the thyristor indicated by the solid line (3) in FIG. A direct current of the sum of the circulating current of the loop of 16a, the reactor 18, and the thyristor 16b and the circulating current of the loop of the diode 17a, the reactor 18, and the diode 17b shown by the solid line (4) in FIG.
[0016]
Since a direct current flows through the reactor 18, the impedance becomes almost zero and the insertion loss becomes almost zero.
[0017]
The current flowing through the thyristors 16a and 16b and the diodes 17a and 17b is the sum of the alternating current of the solid line (1) or the broken line (2) and the direct current of the solid line (3) or the solid line (4). For example, an alternating current indicated by a solid line (1) and a direct current return current indicated by a solid line (3) flow through the thyristor 16a.
[0018]
Next, when a failure such as a voltage drop or a power failure occurs on the power system side and an overcurrent such as a short-circuit current flows from the generator 8 via the bridge circuit 15 and the switch 11 to the failure point, the bridge circuit 15 In the thyristor 16a and diode 17b or thyristor 16b and diode 17a, a current in the direction opposite to the circulating current flows, the circulating current disappears, and the AC terminals AC ₁ and AC ₂ The alternating current flows between the reactors 18.
[0019]
In this case, it becomes equivalent to a state in which the reactor 18 is connected in series with the switch 11, the impedance of the bridge circuit 15 viewed from between the AC terminals AC ₁ and AC ₂ increases, and the AC terminal AC _{1 is} caused by the current limiting action of the reactor 18. , The overcurrent flow between AC ₂ is suppressed and the short circuit current is limited.
[0020]
Here, the real-time monitoring and detection of the system abnormality by comparing the direct current flowing through the reactor 18 and the reference value allows the system voltage to be instantaneously reduced while maintaining the current-limiting function from the occurrence of a failure such as a power supply voltage drop or power failure. The disappearance is detected. Based on this detection, the thyristors 16a and 16b are immediately turned off by the extinction control of the thyristors 16a and 16b at the zero-cross point of the next half cycle, and the self-generated bus 10 is disconnected from the power receiving bus 4 by the high-speed shutoff operation. Disconnected.
[0021]
For this reason, when a failure such as a voltage drop or a power failure occurs on the power system side, the voltage drop or power failure of the self-system bus 10 is prevented by the current limiting action and the high-speed interruption of the bridge circuit 15, and the important load 14a, ..., 14n stable power feeding is continued.
[0022]
Next, when returning to the grid connection state, the AC terminals AC ₁ and AC _{2 of the} bridge circuit 15 are used. After closing the switch 20 for opening and closing the bypass path provided in the bypass path 19 between them, the switch 11 is synchronized and the self-generated bus 10 is connected to the power receiving bus 4 via the bypass 19 and the switch 11. Connect to a transient grid connection.
[0023]
Further, the thyristors 16 a and 16 b are controlled to be turned on to turn on the bridge circuit 15, and then the switch 20 is opened to connect the self-generated bus 10 to the power receiving bus 4 via the bridge circuit 15 and switch 11. Return to normal grid connection.
[0024]
However, in the configuration of FIG. 6, if a failure such as a voltage drop such as an instantaneous voltage drop or a power failure occurs on the power system side during a transitional period from the synchronous turning on of the switch 11 to the turning on of the bridge circuit 15, An overcurrent such as a short-circuit current flows from the system bus 10 to the power receiving bus 4 through the bypass 19 and the switch 11.
[0025]
Therefore, it is conceivable to provide a fuse 21 in series with the switch 20 of the bypass 19 as shown in FIG.
[0026]
In this case, the fuse 21 is blown to prevent the overcurrent during the transient period, and stable power feeding of the important loads 14a to 14n of the self-generated bus 10 is ensured.
[0027]
However, in the case of the configuration of FIG. 8, the grid connection state cannot be restored until the blown fuse 21 is replaced, and even if the system voltage is restored after the fuse 21 is blown, the grid connection state is restored immediately. There is a problem that can not be.
[0028]
It is an object of the present invention to enable quick return to the grid connection after recovery even if a failure such as a voltage drop or a power failure occurs during the transition period when returning to the grid connection state. To do.
[0029]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the grid interconnection device of the present invention is provided between a power receiving bus connected to the power system and a bus (self-generated bus) of a private power generation facility connected to the power system. A bus contact switch that is opened in the event of a failure such as a voltage drop in the power system or a power failure, and is re-entered after the failure is restored;
A bridge connection circuit consisting of a full bridge connection of a semiconductor controlled rectifier element or a mixed bridge connection of a semiconductor controlled rectifier element and a diode, and an excess between the two buses that are provided between a pair of DC terminals of the circuit and are connected to each other during operation. Formed by a first current-limiting reactor for blocking current, a pair of AC terminals of a bridge connection circuit are connected to both buses via a bus-connecting switch, and point extinction control of a semiconductor control rectifier A rectifier type bridge circuit for high-speed shut-off that is turned off prior to opening of the switch for connecting the bus when the failure occurs based on
It is provided in the bypass path between the pair of AC terminals, and is closed only for a short time after the failure is restored until the rectifier-type bridge circuit turns on and shifts to grid operation after reconnecting the bus contactor switch. A bypass for opening and closing the bypass path;
A short-current rated current-reducing second reactor that is connected to the switch in series and is provided in the bypass path and prevents overcurrent in the bypass path.
[0030]
Therefore, the bypass circuit between the pair of AC terminals of the rectifier type bridge circuit is provided with a series circuit of a switch for opening / closing the bypass path and a second reactor for current limiting with a short-time rating.
[0031]
Then, when the failure on the power system side is recovered and the system is returned to the grid connection, after closing the bypass path opening / closing switch and turning on the bus connection switch, the self-generated bus is connected to the bypass path. It is connected to the power receiving bus line via the second reactor, the bypass path opening / closing switch, and the bus line connecting switch, so that a transient grid connection state is established.
[0032]
Next, when the rectifier type bridge circuit is turned on, the switch for opening and closing the bypass path is opened, and the connecting path of both buses is switched from the bypass path to the rectifier type bridge circuit.
[0033]
And, in the transition period until the rectifier bridge circuit is turned on, when a failure such as voltage drop or power failure occurs on the power system side including the power receiving bus, overcurrent such as short circuit current is limited by the second reactor, The voltage drop and power outage of the self-generated bus are prevented.
[0034]
In this case, a voltage drop or power failure of the self-generated bus is prevented by the current limiting action of the second reactor, not by fusing the fuse, etc., so it is not necessary to replace the fuse, etc. It becomes possible to return to the interconnection.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
In FIG. 1 showing the entire configuration of the so-called main circuit section, the difference from FIG. 8 is that the reactor 18 of the bridge circuit 15 is the first reactor for current limiting and is limited to the position of the fuse 21 in FIG. The diverted second reactor 22 is provided and the fuse 21 is omitted.
[0036]
The switching of the switches 11 and 20 and the point-extinguishing control of the thyristors 16a and 16b of the bridge circuit 15 are performed by a control unit (not shown) according to, for example, set sequence control.
[0037]
When the power system side including the power receiving bus 4 is normal, the switch 11 is closed, the thyristors 16a and 16b are controlled to be turned on, the bridge circuit 15 is turned on, and the power receiving bus 4 and the self-generated bus 10 Are connected via the switch 11 and the bridge circuit 15, and the generator 8 is operated in an interconnected state to enter the state of the interconnected system shown in FIG.
[0038]
In addition, <ON> of FIG. 2 shows a closed state and an ON (conduction) state, and <OFF> shows an open state and an OFF (non-conduction) state.
At this time, the switch 20 is opened and the bypass path 19 is kept open.
[0039]
Then, based on the voltage relationship between the buses 4 and 10, for example, a part of the output of the generator 8 is supplied to the power receiving bus 4 via the bridge circuit 15 as indicated by a solid line (5) in FIG.
[0040]
Next, in this state, for example, when a failure of an instantaneous voltage drop due to lightning damage shown in FIG. 2B occurs on the power system side, an overcurrent between the buses 4 and 10 is generated by the current limiting action of the reactor 18 of the bridge circuit 5. At the same time, by the arc extinguishing control of the thyristors 16a and 16b based on the real-time monitoring of the system abnormality, the bridge circuit 15 is turned off within one cycle of the system power supply 1, and the buses 4 and 10 are opened by the high-speed disconnection operation. Is done.
[0041]
Therefore, voltage fluctuation of the self-generated bus 10 is prevented, and stable power supply without any instantaneous voltage drop or the like is continued to each of the important loads 14a to 14n based on the output of the generator 8.
[0042]
After that, the switch 11 is backed up as shown in FIG. 2C in conjunction with the continuation of the failure or the bridge circuit 15 being turned off.
[0043]
Next, the sequence control or the like shifts to the waiting state shown in FIG. 2D, the switch 20 is turned on, and the bypass 19 is turned on.
[0044]
Further, for example, based on the detection of normal return of the system voltage, the process shifts to FIG. 2 (e), the switch 11 is turned on in synchronization with the system power supply 1, and the self-generated bus 10 is connected to the bypass path 19, It is connected to the power receiving bus 4 via the switch 11 and enters a transient grid connection state.
[0045]
Then, based on the voltage difference between the buses 4 and 10, for example, as indicated by a solid line (6) in FIG. 4, a part of the output of the generator 16 is routed from the self-generated bus 10 via the bypass 19 and the switch 11. To the power receiving bus 4.
[0046]
By the way, when a voltage drop such as an instantaneous voltage drop due to lightning damage or a fault such as a ground fault or a short-circuit power failure occurs on the power system side in this transitional grid connection state, a bypass path from the self-generated bus 10 19, Overcurrent such as short-circuit current tends to flow through the power receiving bus 4 via the switch 11, but this overcurrent is limited and prevented by the current limiting action of the reactor 22.
[0047]
Then, for example, the switch 20 is opened by real-time monitoring of the above-described system abnormality, and then the switch 11 is also opened to return to the state of (c) in the figure, and the operation is repeated from this state.
[0048]
On the other hand, when the switch 11 is turned on synchronously due to the insertion of FIG. 2 (e), no fault or the like on the power system side occurs and the buses 4 and 10 are normally connected. Shifting to the grid connection return of (f), the ignition control of the thyristors 16a, 16b is started, the bridge circuit 15 is turned on, the switch 20 is then opened, and the buses 4, 10 are again connected to the switches 11, It is connected via the bridge circuit 15 and returns to a normal grid connection state.
[0049]
8 is provided in the bypass path 19 instead of the fuse 21 of FIG. 8, and an overcurrent such as a short-circuit current in a transient grid connection state in which the buses 4 and 10 are connected via the bypass path 19 is provided. Therefore, the work such as replacement of the fuse 21 is not necessary and can be immediately restored to the grid connection by the subsequent restoration on the power system side.
[0050]
In addition, based on a series of control processes for returning to the grid connection, the bridge circuit 15 is turned on after the switch 11 is turned on by the insertion of FIG. 2E, and the normal system of FIG. The time required for returning to the grid connection, and the time required for opening the switch 11 when the switch 11 is turned on due to the above-mentioned insertion, are both a short time within 1 second. The reactor 22 may be a short-time rated small-sized one that limits this short-time overcurrent.
[0051]
By the way, when applying to an actual electric power system, this grid connection apparatus is provided for every phase.
[0052]
Specifically, the switches 11 and 20, the bridge circuit 15, the main circuit unit of the reactor 22, and these control units are provided for each phase of the bus bars 4 and 10.
[0053]
The semiconductor control DC element of the bridge circuit 15 may be, for example, a power switching transistor.
[0054]
Further, the semiconductor control rectifying element, the number of diodes, the connection combination thereof, and the like of the bridge circuit 15 are not limited to those in the embodiment.
[0055]
In the above embodiment, the bridge connection circuit of the bridge circuit 15 is formed by the mixed bridge connection of the thyristors 16a and 16b and the diodes 17a and 17b so as to reduce the size. However, the bridge connection circuit is a thyristor. It may be formed by full bridge connection.
[0056]
Further, the capacity of the reactors 18 and 22 may be set in consideration of the loads 7a to 7n and 14a to 14n of the buses 4 and 10.
[0057]
The present invention can be applied to high-voltage or extra-high power receiving facilities such as factories and buildings having various cogeneration facilities as private power generation facilities.
[0058]
【The invention's effect】
The present invention has the effects described below.
A bypass circuit 19 between the AC terminals AC1 and AC2 of the rectifier type bridge circuit 15 is provided with a series circuit of a switch 20 for opening and closing the bypass path and a second reactor 22 for current limiting with a short-time rating. When the failure of the system is restored and the system interconnection operation is resumed, when the switch 11 for connecting the bus is turned on after the switch 20 is closed, the bus (in-house system bus) 10 is connected to the reactor 22 and the switch 20 And it is connected to the power receiving bus 4 via the switch 11 and enters a transient grid connection state.
[0059]
At this time, when a failure such as a voltage drop or a power failure occurs on the system side including the power receiving bus 4, an overcurrent such as a short-circuit current is limited by the current limiting action of the reactor 22, thereby preventing a voltage drop or a power failure of the bus 10. .
[0060]
And since the voltage drop and power failure of the bus line 10 are prevented by the current limiting action of the reactor 22 rather than the fusing of the fuse or the like, it is not necessary to replace the fuse, and the system is immediately restored to the grid connection after the failure is restored. be able to.
[Brief description of the drawings]
FIG. 1 is a single-line system diagram of a first embodiment of the present invention.
2A to 2F are single line diagrams for explaining the operation of FIG.
3 is an explanatory diagram of a current path in the grid interconnection of FIG. 1. FIG.
4 is an explanatory diagram of a current path in an interconnection transition period of FIG. 1. FIG. 5 is a single-line system diagram of a conventional device.
6 is a partial connection diagram in the case where a rectifier bridge circuit and a bypass path for high-speed shutoff are added to the apparatus of FIG. 5;
7 is an operation explanatory diagram of the bridge circuit of FIG. 6;
8 is a single-line system diagram when a fuse is added to the bypass path of FIG. 6;
[Explanation of symbols]
1 System power supply 4 Receiving bus 8 Generator 10 Bus for private power generation facilities (in-house bus)
11 Bus Switch 15 Rectifier Bridge Circuits 16a, 16b Thyristors 17a, 17b Diode 18 First Reactor 19 Bypass Path 20 Bypass Path Opening Switch 22 Second Reactor

Claims (1)

It is provided between the power receiving bus connected to the power grid and the bus of the private power generation facility linked to the power grid, and is opened when a fault such as a voltage drop or power failure occurs in the power grid. A switch for connecting the bus that will be re-entered later,
A bridge connection circuit comprising a full bridge connection of a semiconductor control rectifier element or a mixed bridge connection of the semiconductor control rectifier element and a diode, and between the two buses that are provided between a pair of DC terminals of the circuit and are connected to each other. A first current-limiting reactor for preventing overcurrent, and a pair of AC terminals of the bridge connection circuit are connected to the both buses via the bus-connecting switch; A rectifier type bridge circuit for high-speed shut-off that is turned off prior to opening of the bus contact switch when the failure occurs based on the point arc extinction control, and turned on after the switch is turned on again;
Bypass provided in a bypass path between the pair of AC terminals and closed only for a short time from when the bus-connecting switch is turned on again until the rectifier bridge circuit is turned on and the grid connection is restored A switch for opening and closing the road;
And a second reactor for short-time rating current limiting, which is connected to the bypass path switching switch in series and provided in the bypass path to prevent an overcurrent of the bypass path. Grid interconnection device.

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