JPH11299103A - System interlinkage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the normal state loss of a load system with which a plurality of power supply system are interlinked by a system interlinkage device, and suppress the voltage decline of the load system which accompanies a failure, a switching, etc., on the power supply system side. SOLUTION: In a system interlinkage device 31, a power supply system G1 is connected to an interlinkage point 32 with a load system through a high speed current limiting breaker SW1 which has a hybrid bridge K1 and a DC reactor L1 and, in the same way, a power supply system G2 is connected to the interlinkage point 32 through a high speed current limiting breaker SW2 which has a hybrid bridge K2 and a DC reactor L2. If a failure, etc., occurs and the system G1 is switched to the system G2, until thyristors TH11 and TH12 are driven to be turned off, the current limiting effect of the DC reactor L1 is exhibited to suppress the voltage decline of the load system for that period. When the thyristors TH11 and TH12 are turned off, thyrisors TH21 and TH22 are turned on immediately and the system G2 is interlinked with the load system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in which a load system is connected to a plurality of power systems, for example, a plurality of commercial power systems of different power companies, and a backup system of a commercial power system, a private power generation system, and a stationary power supply. The present invention relates to a system interconnection device used for interconnection.

[0002]

2. Description of the Related Art For example, when a system having a severe short-circuit current and another power supply system are connected to a load system without interconnection, one is used as a normal system and the other is used as a standby system. Switching of interconnection is performed when an accident occurs in the service system. In addition, factories and the like are equipped with in-house power generators and stationary power supplies for important loads in preparation for a power outage of the commercial power supply system, and these can be switched appropriately in the event of an accident or maintenance. Will be

[0003] As a basic configuration for interconnecting a load system to a power system, a configuration is used in which each power system is connected to a connection point to the load system via a circuit breaker. With such a configuration, for example, when switching the system in response to the occurrence of an accident, the power supply voltage is detected by a voltage transformer, and the undervoltage relay detects a drop in the power supply voltage at a predetermined set value or more, or is connected continuously. When a system current is detected by a current transformer and a current increase exceeding a predetermined set value is detected by an overcurrent relay, the circuit breaker is switched.

However, it takes a long time to release the circuit breaker (three types of 2, 3, or 5 cycles in the JEC2300 standard), and thereafter, until the circuit breaker of another power supply system becomes conductive. In this case, the voltage of the load system remains low. Further, when the power supply system is switched, a sudden current fluctuation occurs in the power supply system to be switched, which places a heavy load on the power supply and also causes a voltage fluctuation in the power supply system.

FIG. 2 shows a voltage drop compensation range and a load operation compensation range when a system frequency is set to 50 Hz and a vacuum circuit breaker is used as the circuit breaker. FIG. 2 shows a threshold value at which each load has an effect on the voltage drop rate and the voltage drop duration time, and reference numeral α1 denotes a voltage drop compensation range by the vacuum circuit breaker. .

As shown in FIG. 2, most of the loads are out of the compensation range, and the influence of the voltage drop occurs. For this reason, various types of system interconnection devices that enable high-speed switching between systems have been put into practical use, and the configuration is shown in FIGS. 3 and 4.

FIG. 3 is a single-phase connection diagram of a typical prior art interconnection system 1. This system interconnection device 1 is connected to an interconnection point 2 connected to a load by one power supply system g1.
Are connected via a circuit breaker cb1 and a high-speed cutoff device sw1, and the other power supply system g2 is also connected to the interconnection point 2 via a circuit breaker cb2 and a high-speed cutoff device sw2.

The high-speed cut-off devices sw1 and sw2 are each composed of a pair of thyristors th11 and t11 connected in anti-parallel with each other.
h12; th21 and th22. The circuit breakers cb1 and cb2 are both conductive at a normal time,
If the power supply system g1 side is a normal system, the thyristor th
The gates of the thyristors th2 and th12 are driven.
The gates of 1 and th22 are shut off, and power is supplied to the load system from the power supply system g1 side. Power system g
If an accident or power outage occurs on the first side, thyristors th11,
After the gate of th12 is shut off, thyristor th2
The gates of the first and th22 are driven, power is supplied from the power supply system g2 to the load system, and the circuit breaker cb
1 is released.

FIG. 4 is a single-phase connection diagram of another conventional system interconnection device 11. In this system interconnection device 11,
Similarly to the system interconnection device 1, the power supply system g1 is connected to the interconnection point 2 via the circuit breaker cb1 and the high-speed interruption device sw1.
And the power supply system g2 is connected to the interconnection point 2 via a circuit breaker cb2 and a high-speed circuit breaker sw2. Further, each of the power supply systems g1 and g2 is connected to the interconnection point 2 is connected. The main switch 12 includes a common contact connected to the interconnection point 2 and two power supply systems g.
1 and g2, and two individual contacts respectively corresponding to one of the individual contacts. In this system interconnection device 11, the circuit breakers cb1 and cb2 are both conductive at the time of steady state, and the thyristors th11 and th1
2; th21 and th22 are always shut off.

For example, when an accident or the like occurs on the power supply system g1 side while the power supply system g1 is connected to the load system, first, the gates of the thyristors th11 and th12 are driven, and the interconnection point 2 Along with the main switch 12,
The power supply system g1 is also connected via the circuit breaker cb1 and the high-speed circuit breaker sw1. Thus, after the current on the main switch 12 side is reduced, switching of the main switch 12 is performed, and the thyristors th11 and th12 are cut off.

When an accident or the like occurs on the power supply system g2 side while the power supply system g2 side is connected to the interconnection point 2, the gates of the thyristors th21 and th22 are driven, and the current of the main switch 12 is reduced. After the reduction, the main switch 12 is switched, and the thyristor th2
1, th22 is cut off. In this manner, the switching between the two power supply systems g1 and g2 is performed gently.

As described above, in the system interconnection devices 1 and 11, thyristors th11 and th12; th21 and th2
2, the two power supply systems g1,
Switching of g2 is performed. For example, in the case of the system interconnection device 1, the disconnection of the interconnected system includes detection of a voltage drop and thyristors th11, th12; th21, th.
The time required until the zero crossing through which the arc 22 can be extinguished can be reduced to about one cycle. Thereby, the voltage drop can be compensated to the range indicated by reference numeral α2 in FIG. 2, and many operations of the OA device, the medical electric device, and the like can be compensated. However, there is a problem that the influence on the electromagnetic switch interposed in the distribution line to the important load and the variable speed motor included in the important load is inevitable. Further, when the power supply system is switched, a heavy load is still applied to the power supply of the power supply system to be switched.

On the other hand, in a configuration in which the two power supply systems g1 and g2 are interconnected, if an accident occurs in one of the power supply systems, for example, g1, the other power supply system g that is connected and operated.
2 also has a problem that a voltage drop occurs. In this case, the voltage drop can be significantly suppressed in the interconnection by the system interconnection devices 1 and 11 compared to the interconnection by the circuit breaker. However, there is still an instantaneous brownout that affects the critical load.

If the power supply of the other power supply system g2 is a small-capacity power supply such as the private power generator or the stationary power supply, a large load is applied to the power supply. For example, when the power source is a rotary machine type power source such as a diesel generator or a gas turbine generator, a large torque fluctuation occurs, and in some cases, a failure such as a shear pin break occurs. Further, when the power source is a static power source such as a photovoltaic power generation system, an uninterruptible power supply device called UPS, and a fuel cell, problems such as a reduction in battery life due to a sudden change in current occur. Furthermore, when the power supply system g2 of the private power generation system is connected to the commercial power supply system g1 having a large capacity, there is a problem that a product having a large short-circuit capacity is required for a circuit breaker or a cable on the power supply system g2 side.

The thyristors th11 and th1
2; Grid interconnection devices 1 and 11 using th21 and th22
In order to compensate for the operation of the load that cannot be compensated for even by the above (outside the range indicated by reference numeral α2 in FIG. 2)
As still another conventional technique, a system interconnection device 2 shown in FIG.
1 is used. This system interconnection device 21 is a UPS
And uninterruptible power supply devices 22 and 23 referred to as “power supply units”.

The UPSs 22 and 23 convert the input power into AC / DC and rectify and smooth the input power, and
The power stored in the batteries 24 and 25 is DC / AC converted and output to a load. The battery 24 of the UPS 22 can be charged by electric power from the power supply system g1, and the battery 25 of the UPS 23 can be charged by electric power from the power supply system g1 or g2. UPS 22, 23
Is supplied from the interconnection point 2 to the load system.

In the system interconnection device 21, normally, the switches b1 to b13 are turned on, the switches a1 to a7 are turned off, and the UPSs 22, 2 are powered by power from the power system g1.
3 operate and output power from these is supplied to the load system. At this time, the thyristors th1 and th2 are conducting, and the thyristor th3 is blocking. In the case of an accident or maintenance, these switches a1 to a7;
The b1 to b13 and the thyristors th1 to th3 are driven ON / OFF in a predetermined order.

[0018]

In the system interconnection device 21 configured as described above, since the power from the power supply systems g1 and g2 is temporarily charged and discharged to the batteries 24 and 25 and output, an accident occurs. Even if such a situation occurs, there is almost no voltage fluctuation in the load system, and the operation of the load device can be compensated. However, since a large conversion loss always occurs, there is a problem that it can be used only for some of the most important loads such as broadcasting equipment.

An object of the present invention is to provide a system interconnection device capable of suppressing a voltage drop in a load system at the time of switching of a power system with a small constant loss.

[0020]

According to a first aspect of the present invention, there is provided a system interconnection device for interconnecting a load system to a plurality of power systems, wherein a semiconductor switching element is provided for each of the power systems. It is configured to include a current limiting reactor,
It is characterized in that a high-speed current-limiting device is provided, one end of which is connected to each of the power supply systems, and the other end of which is commonly connected to a connection point to the load system.

According to the above configuration, the first connected
When an accident or the like occurs in the power supply system of the present invention and the first power supply system is to be disconnected, the semiconductor switching element of the high-speed current-limiting device provided in connection with the first power supply system must be turned off. For example, even if a time of about one cycle is required, the current limiting reactor presents a large impedance due to the current value maintaining action of the current limiting reactor during the time, and the time between the first power supply system and the load system is reduced. And the voltage drop of the load system is suppressed.

Similarly, after the semiconductor switching element of the high-speed current limiting device of the first power supply system is turned off, the semiconductor switching element of the high-speed current limiting device of the second or third power system is selectively turned on. Even if the power is turned on, the voltage drop of the second or third power supply system is also caused by the second or third power supply system.
.. Can be suppressed by the current limiting reactor of the high-speed current limiting interrupter of the power supply system, and the load on the power supply can be reduced.

The impedance of the current limiting reactor (ωL) is large at the time of the accident and at the time of injection (when ω is large), but is small at the steady state (when ω is small). In this way, the power supply system can be switched with a small constant loss.

Further, when a plurality of power supply systems are interconnected, for example, the influence of the accident or the like occurring in the first power supply system may be caused by the second or third connected operation.
Of the second or third ...
Voltage fluctuations of the power supply system can be suppressed. Therefore, the load on the power supply of the second or third power supply system is reduced, and when the power supply is a rotary power supply such as the diesel generator or gas turbine generator having a small capacity, a shear pin breakage or the like occurs. The solar power generation system, wherein the power supply has a small capacity,
In the case of a static power supply such as an uninterruptible power supply and a fuel cell, it is possible to prevent problems such as a reduction in battery life. Furthermore, there is no need to increase the short-circuit capacity of the circuit breakers or cables on the second or third power supply system side.

Further, in the grid interconnection device according to the second aspect of the present invention, each of the high-speed current-limiting devices has a thyristor arm connected to one of two AC terminals and a diode arm or a thyristor operated by diode in the other. It is characterized by comprising a single-phase rectification bridge circuit having an arm connected thereto, and a DC reactor connected between DC terminals of the single-phase rectification bridge circuit.

According to the above configuration, the current limiting reactor is a DC reactor, and the current flowing through the DC reactor is a DC current containing a very small amount of a ripple component twice the system frequency. Can be made substantially zero.

When the system is cut off, the thyristor is turned off, whereby the magnetic field energy accumulated in the DC reactor by the DC current flows back through the diode arm or the thyristor arm operated by the diode and is absorbed. Therefore, an undesirable accident such as dielectric breakdown due to the emission of the magnetic field energy does not occur.

Further, in the grid interconnection device according to the invention of claim 3, one of the two AC terminals is connected to the interconnection point, and the other is connected to the power supply system.

According to the above configuration, the current return loop according to the second aspect is formed on the power supply system side, and it is possible to prevent the recirculated current from flowing into the load system side. The power supply system to be connected can be quickly connected.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on FIG. 1 and FIG.

FIG. 1 is a single-phase connection diagram of a system interconnection device 31 according to one embodiment of the present invention. This system interconnection device 31
Is used to selectively connect the two power supply systems G1 and G2 to the interconnection point 32 connected to the load system. The power supply system G1 is connected to the interconnection point 32 via a circuit breaker CB1 and a high-speed current-limiting circuit breaker SW1. Similarly, the power supply system G2 is connected to the interconnection point 32 via a circuit breaker CB2 and a high-speed current limiting circuit breaker SW2.

The high-speed current limiter SW1 includes a pair of diodes D11 and D12 and a pair of thyristors TH11 and TH.
12 and a DC reactor L
1 is provided. Of the two AC terminals AC11 and AC12 of the mixing bridge K1, one AC terminal AC1 to which the thyristors TH11 and TH12 are connected.
1 is connected to the interconnection point 32, and a diode D11,
Another AC terminal AC12 to which D12 is connected is connected to power supply system G1 via circuit breaker CB1. Also, the two DC terminals DC11 and DC12 of the mixed bridge K1
A DC reactor L1 is connected between them.

Similarly to the high-speed current limiting device SW1, the high-speed current limiting device SW2 has a pair of diodes D21 and D21.
And a rectifier L2, and a mixing bridge K2 including a thyristor TH21 and a pair of thyristors TH21 and TH22. Two AC terminals AC of the mixing bridge K2
21 and AC22, thyristors TH21 and TH22
Is connected to the connection point 3
2, and the other AC terminal AC22 to which the diodes D21 and D22 are connected is connected to the power supply system G2 via the circuit breaker CB2. Two DC terminals DC21, DC
A DC reactor L2 is connected between the terminals 22.

The thyristors TH11 and TH12; TH
21 and TH22 are turned on / off by a control circuit (not shown) at the time of system switching due to an accident such as a short circuit or ground fault.
FF drive is performed. Further, the circuit breakers CB1 and CB2 are provided for inspection and the like, and are both conductive at a normal time.

The larger the current decay time constant is between the current decay time constant determined by the reactance component and the resistance component of the DC reactor L1 and the mixing bridge K1, and the equivalent impedance seen from the system side, There is a problem that the equivalent impedance becomes small. In the present invention, the current decay time constant is selected to be about 2.5 times the system frequency cycle. As a result, during the time required from the occurrence of the accident to the interruption of the thyristors TH11 and TH12, the current limiting effect can be sufficiently exhibited, the impedance at the steady state can be reduced, and the loss can always be reduced. Similarly, the reactance component and the resistance component of the DC reactor L2 and the current decay time constant determined by the mixing bridge K2 are also selected to be about 2.5 times the system frequency cycle.

The operation of the system interconnection device 31 thus configured when the interconnection point 32 is switched from the state of being connected to the power system G1 to the power system G2 will be described. First, before switching, the thyristors TH21, T21
H22 is turned off and thyristor T
H11 and TH12 are ON.

When an accident or the like occurs on the power supply system G1 side, the thyristors TH11 and TH12 are driven off. However, it takes about one cycle, for example, as described above, after the accident actually occurs until the thyristors TH11 and TH12 are turned off. During this time, the DC reactor L1 exhibits a current limiting effect, and the AC terminal AC1
1, the impedance viewed from the AC12 side increases, and the voltage is shared between the power supply system G1 and the load system. Thus, a voltage drop in the load system can be suppressed.

Immediately after the thyristors TH11 and TH12 are turned off, the thyristors TH21 and TH22 are turned on immediately, so that switching can be performed without an instantaneous interruption. For the ON drive of the thyristors TH21 and TH22, the DC reactor L2 exhibits a current limiting effect, suppresses a voltage drop due to a load change on the power supply system G2 side, and reduces a load on the power supply of the power supply system G2. can do.

As described above, the DC reactor L1,
Due to the current limiting effect of L2, in FIG.
Voltage drop can be compensated to the range indicated by 3, and stable operation of a variable speed motor for power electronics application, an electromagnetic switch to which an important load is connected, and the like can be compensated.

In the high-speed current limiting circuit breakers SW1 and SW2, the thyristors TH11 and TH1 are connected to the interconnection point 32 side.
2; since TH21 and TH22 are arranged, when these thyristors TH11, TH12; TH21, TH22 are cut off, the magnetic field energy remaining in the DC reactors L1, L2 is reduced by the diode D11 on the power supply system G1, G2 side, respectively. , D12; D21 and D22 are refluxed and disappear, so that the current due to the magnetic field energy does not flow into the interconnection point 32. As a result, after the thyristor on the side to be cut off is driven off, the thyristor on the side to be turned on next can be immediately driven on.

On the other hand, for example, when a large-capacity power supply system G1 as a commercial power supply system is connected to a small-capacity private power supply system G2, the thyristors TH11 and TH12; TH21 and TH22 are both connected. When the power supply system G1 is turned on, the influence of, for example, an accident occurring in the power supply system G1 is prevented from reaching the power supply system G2 side, and voltage fluctuation on the power supply system G2 side can be suppressed. Therefore, the burden on the power supply of the power supply system G2 is reduced, and when the power supply is a rotary-type power supply such as a diesel generator or a gas turbine generator, it is possible to prevent the occurrence of problems such as shear pin breakage. In the case where the power supply is a static power supply such as a photovoltaic power generation system, an uninterruptible power supply, and a fuel cell, it is possible to prevent problems such as a reduction in battery life. Further, it is not necessary to increase the short-circuit capacity of the circuit breaker or the cable on the power supply system G2 side. Furthermore, when reverse power flow is possible, the generator can be efficiently operated on the power supply system G2 side even if the generator capacity is larger than the load capacity.

As described above, the present invention may be used to switch between three or more power supply systems, such as a commercial power supply system, a private power generation system, and a stationary power supply system. A thyristor pure bridge may be used instead of K1 and K2, and the thyristors of the arms on the side of the power supply systems G1 and G2 may be operated by diode.

[0043]

According to the first aspect of the present invention, there is provided a grid interconnection device,
As described above, in a system interconnection device that interconnects a load system to a plurality of power systems, a high-speed current-limiting device that includes a semiconductor switching element and a current-limiting reactor connects each power system to an interconnection point. Until disconnection of the connected power supply system, the current between the power supply system and the load system is shared by the current limiting action of the current-limiting reactor, thereby suppressing voltage drop in the load system. .

Therefore, it is possible to switch the power supply system while suppressing the voltage drop of the load system. Further, the voltage drop of the power supply system on the side to be switched can be suppressed by the current value maintaining action by the current limiting reactor of the power supply system, and the burden on the power supply can be reduced.

Further, even in the case where a plurality of power supply systems are interconnected, the influence of an accident or the like occurring in a certain power supply system is prevented from affecting other power supply systems that are connected and operated. Voltage fluctuations of the power supply system can be suppressed. Therefore, the burden on the power supply of the other power supply system is reduced, and even when the capacity of the power supply is small, it is possible to prevent the occurrence of a problem. Furthermore, there is no need to increase the short-circuit capacity of the circuit breaker or cable on the other power supply system side.

Further, in the system interconnection device according to the second aspect of the present invention, as described above, each of the high-speed current limiting interrupters is connected to one of the two AC terminals with a thyristor arm and the other with a diode arm or a diode arm. It comprises a single-phase rectifier bridge circuit connected to a thyristor arm operated by a diode, and a DC reactor connected between DC terminals of the single-phase rectifier bridge circuit.

Therefore, since the current limiting reactor is a DC reactor, the impedance of the DC reactor in a steady state can be made substantially zero. Further, at the time of system interruption, the magnetic field energy accumulated in the DC reactor can be absorbed by refluxing the diode arm or the thyristor arm side operated by the diode, and undesired breakdown such as dielectric breakdown due to emission of the magnetic field energy can be achieved. No serious accidents occur.

Further, according to the third aspect of the present invention, as described above, of the two AC terminals,
The thyristor arm side is connected to the interconnection point, and the diode arm or the diode-operated thyristor arm side is connected to the power supply system.

Therefore, the current return loop can be formed on the power supply system side to prevent the returning current from flowing into the load system side, and the power supply system to be connected next can be quickly connected. it can.

[Brief description of the drawings]

FIG. 1 is a single-phase connection diagram for explaining a system interconnection device according to an embodiment of the present invention.

FIG. 2 is a graph for explaining a relationship between a voltage drop compensation range and a load operation compensation range of a grid interconnection device according to the present invention and the prior art.

FIG. 3 is a single-phase connection diagram for explaining a typical prior art system interconnection device.

FIG. 4 is a single-phase connection diagram for explaining another conventional system interconnection device.

FIG. 5 is a single-phase connection diagram for explaining still another conventional system interconnection device.

[Explanation of symbols]

31 System interconnection device 32 Interconnection points AC11, AC12; AC21, AC22 AC terminals CB1, CB2 Circuit breaker D11, D12; D21, D22 Diode DC11, DC12; DC21, DC22 DC terminals G1, G2 Power supply system K1, K2 Mixed bridge L1, L2 DC reactor TH11, TH12; TH21, TH22 Thyristor

Claims (3)

[Claims] 1. A system interconnection device for interconnecting a load system to a plurality of power systems, wherein each power system includes a semiconductor switching element and a current limiting reactor, and one end is connected to each of the power systems. A system interconnection device, comprising: a high-speed current-limiting device that is connected and has the other end commonly connected to an interconnection point to the load system. 2. The single-phase rectifier bridge circuit according to claim 1, wherein each of the two AC terminals is connected to a thyristor arm and the other is connected to a diode arm or a diode-operated thyristor arm. The system interconnection device according to claim 1, further comprising a DC reactor connected between DC terminals of the single-phase rectification bridge circuit. 3. The system interconnection device according to claim 2, wherein one of the two AC terminals is connected to the interconnection point, and the other is connected to the power supply system.