JPH1169664A - Distributed power supply device with instantaneous voltage drop countermeaure function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an instantaneous voltage drop at the time of a failure in a distributed power supply device which consists of a commercial power supply system and a distributed power supply system such as a cogeneration system which is linked with the commercial power supply by using a high speed current-limiting breaker system while the device cost and a loss in a steady state are suppressed. SOLUTION: A high speed current-limiting breaker 31 is constructed so as to include a single-phase rectification circuit 42 whose two AC terminals are respectively connected to systems and a DC reactor 43 which is connected between the DC terminals of the single-phase rectification circuit 42. If the allowable voltage drop ratio of a bus-bar 36 when a failure 49 occurs in the commercial power supply system is denoted by A and the equivalent inductance of the distributed power supply system is denoted by Ls, the inductance Ldc of the DC reactor 43 is selected so as to satisfy a relation; Ldc=Ls×(1-A)/A. With this constitution, the voltage of the bus-bar 36 is Ldc/(Ldc+Ls) times of a system voltage when the failure occurs, so that the voltage drop can be suppressed within a required range without using an uninterrupted power supply device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed power supply system which is operated in connection with a commercial power supply system and includes various power supplies and important loads as described later. The present invention relates to a distributed power supply device that protects the important load not only from a power failure but also from an instantaneous voltage drop.

[0002]

2. Description of the Related Art FIG. 4 is a single-phase connection diagram of a power system for explaining a conventional distributed power supply device. This distributed power supply device is configured to include, as a power supply 7, a private power generation device such as a diesel generator or a gas generator constituting a cogeneration system, which is an example of a so-called new energy power supply. The system is operated in parallel with the system and AC.

[0003] A commercial power supply line 3 drawn into a customer from a power supply 2 of a commercial power supply system is connected to a power receiving bus 4. Many power distribution lines 5 connected to a general load are connected to the power receiving bus 4. The power supply 7 is connected to the bus 6 of the distributed power supply system via a power supply line 10 and, for example, a distribution line 8 to an important load occupying 60 to 70% of the private power generation capacity. The power receiving bus 4 and the bus 6 are mutually connected by the circuit breaker 1.

The power source 7 includes an uninterruptible power source called a secondary battery, a fuel cell, a solar power generation system, a flywheel, a wind power generation system, and a UPS, in addition to the diesel generator and the gas generator. Many types of power supplies, such as devices, can be considered.

[0005]

In order to operate such a distributed power supply system and a commercial power supply system in an interconnected manner, in the prior art, the circuit breaker 1 is installed in the distributed power supply system. In addition, according to the guidelines for interconnection, countermeasures against short-circuit current such as reactors may be taken as necessary. However, when a failure such as a ground fault or a short circuit between phases occurs as indicated by reference numeral 9 in the commercial power supply system, a fault current flows from the distributed power supply system, and a voltage drop occurs in the distributed power supply system.

As a countermeasure against such a failure, the voltage of the commercial power supply line 3 is detected by a voltage transformer, and based on the detection result, it is determined by an undervoltage relay whether a voltage drop is possible or not. When it is determined, the circuit breaker 1 is configured to perform a breaking drive. Further, the interconnection current is detected by a current transformer, and whether or not the current can be increased is determined by an overcurrent relay based on the detection result. When an overcurrent of a predetermined set value or more is detected, the breaking drive of the circuit breaker 1 is performed. In some cases.

However, until the circuit breaker 1 is opened (in the JEC2300 standard, three types of two, three, or five cycles), the voltage of the distributed power supply system remains low. FIG. 5 shows a voltage drop compensation range and a load operation compensation range when a vacuum circuit breaker is used as the circuit breaker 1. FIG. 5 shows a threshold value at which each load has an influence on the voltage drop rate and the voltage drop duration, and reference numeral α1 denotes a voltage drop compensation range by the vacuum circuit breaker.

As shown in FIG. 5, most of the loads connected to the distribution line 8 are out of the compensation range, and the effect of the voltage drop occurs. That is, in the distributed power supply device shown in FIG. 4, although a distributed power supply is connected to the grid, a power failure countermeasure for the important load is taken,
No effect can be expected for the instantaneous voltage drop. For this reason, conventionally, as indicated by reference numeral 12, some of the most important loads include an uninterruptible power supply (UP
S) is interposed.

In this uninterruptible power supply, the power from the bus 6 is AC / DC converted, rectified and smoothed by a charger and stored in a battery, and the power stored in the battery is DC / AC converted. Output to the load. Therefore,
A semiconductor switching element or the like is required, and it is expensive and has a problem that a large conversion loss always occurs. Therefore, it is used for some of the most important loads. Therefore, most loads with widely used electromagnetic switches remain vulnerable to the instantaneous voltage sag.

On the other hand, as shown in FIG. 6, an interconnection device 11 using thyristors connected in antiparallel to each other has been used in order to interconnect a distributed power supply device to a commercial power supply system. In FIG. 6, portions corresponding to the configuration in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. However, even with this interconnection device 11, one cycle may be required until the detection of a voltage drop and the passage of the zero cross that can extinguish the thyristor.

For this reason, the compensation range of the voltage drop in the interconnection device 11 using the thyristor is as shown by the reference numeral α2 in FIG. Therefore, although many operations such as OA equipment and medical electrical equipment can be compensated for, they are still included in the electromagnetic switch interposed in the distribution line to the important load and included in the important load. There is a problem that the influence on the variable speed motor cannot be avoided.

Therefore, among loads that cannot be compensated for by the interconnection device 11 using thyristors (outside the range indicated by reference numeral α2 in FIG. 5), the important ones A power outage power supply 12 is required.

When the distributed power supply system is connected to the commercial power supply system, the short-circuit capacity increases, and each breaker on the load side is replaced with a large one for a short time, or connected to the breaker. It is necessary to replace the existing cable with one having a large current capacity. Furthermore, if it takes a long time to shut down the system at the time of failure, there is a problem that the power supply 7 is stopped and the distributed power supply system is completely stopped.

It is an object of the present invention to provide a distributed power supply device having an instantaneous voltage drop countermeasure function effective against a power failure and an instantaneous voltage drop when connecting a distributed power supply system to a commercial power supply system.

[0015]

According to a first aspect of the present invention, there is provided a distributed power supply device having a voltage sag countermeasure function, comprising one or a plurality of power supplies, connected to a critical load for which voltage sag and power failure are to be avoided, A distributed power supply with a sag protection function, which is operated in parallel with an AC system in parallel with a system, comprising a single-phase rectifier circuit comprising a rectifying element and a DC reactor, wherein the single-phase The AC terminals of the rectifier circuit are connected to buses of the corresponding phases of the commercial power supply system and the distributed power supply system, respectively, and the DC reactor is connected between the DC terminals, and the inductance of the DC reactor causes a failure of the commercial power supply system. When the voltage drop rate that can be tolerated in the distributed power system is sometimes A, the reactor has a value larger than (1-A) / A times the equivalent inductance corresponding to the internal impedance of the distributed power system. Formed to so as to have a scan, and having such a high-speed current-limiting breaker for each phase.

According to the above configuration, when the single-phase rectifier circuit is constituted by, for example, a diode bridge, the series circuit of the diode bridge and the circuit breaker is interposed between the buses of the two systems. When the phase rectifier circuit is configured to include a semiconductor switching element such as a thyristor bridge, the single-phase rectifier circuit is interposed between the buses, and a DC reactor is connected between DC terminals of the single-phase rectifier circuit. The high-speed current-limiting circuit device according to the present invention, when a failure occurs in the commercial power supply system, the DC reactor exhibits a large impedance and suppresses a voltage drop in the distributed power supply system,
In addition, short-circuit current is suppressed. Thus, while the voltage drop is suppressed, the circuit breaker is opened by the protective relay or the semiconductor switching element is extinguished, and the distributed power supply system is cut off from the commercial power supply system.

In the thus configured high-speed current limiting circuit device, when a failure occurs in the commercial power supply system, the bus voltage of the distributed power supply system is changed by the equivalent inductance of the distributed power supply system and the inductance of the DC reactor. The system voltage becomes a divided value. Therefore, assuming that the inductance of the DC reactor is Ldc and the equivalent inductance of the distributed power supply system is Ls, the allowable voltage drop rate A satisfies Ldc / Ls> (1-A) / A as described above. Choose to do. That is, for example, when the voltage drop rate A is set to 50%, the inductance Ldc of the DC reactor is set to be one time the equivalent inductance Ls of the distributed power supply system, so that the voltage drop rate is suppressed within the range of A. be able to. Further, for example, if the voltage drop rate A is 25%, (1-0.25) /
From 0.25, the inductance Ldc of the DC reactor
Should be set to three times the equivalent inductance Ls of the distributed power supply system.

In this way, only by setting the inductance Ldc of the DC reactor in correspondence with the voltage drop rate A allowed for the distributed power supply system at the time of failure and the equivalent inductance Ls of the distributed power supply system, the uninterruptible power supply is achieved. Even without using a power supply device, it is possible to compensate for the operation of a device that is easily affected by an instantaneous voltage drop such as an electromagnetic switch or a variable speed motor to an important load. As a result, the reliability in the interconnection operation can be improved, and the stress on the distributed power supply can be reduced. In addition, since the short-circuit current is suppressed by the current limiting action of the DC reactor, it is not necessary to replace the circuit breaker or the cable on the load side with an undesirably large one at the time of interconnection.

Further, according to a second aspect of the present invention, there is provided a distributed power supply device with a sag-reducing measure function, comprising:
It is characterized by a rotating machine.

According to the above configuration, if the power supply in the distributed power supply system is a rotating machine, the circuit voltage, that is, the output voltage of the generator becomes zero during the short-circuit accident despite the large short-circuit current flowing. Therefore, when the stress between the generator and the prime mover is released, mechanical vibration occurs in the shaft, and when the short-circuit accident is cleared, the generator bears a load exceeding its own capacity, and the generator A sudden braking torque is generated, and an excessive vibration torque is generated on the shaft. As described above, when a short-circuit fault occurs, stress (shear bin rupture, etc. in the case of a turbine generator) occurs due to transient overcurrent flowing out of the generator, whereas the short-circuit current is suppressed as described above. Thereby, the stress can be avoided.

Furthermore, a distributed power supply device with a sag prevention function according to the invention of claim 3 is characterized in that the power supply in the distributed power supply system is a stationary power supply using an inverter.

According to the above configuration, the stationary power supply has no inertia like a rotating machine, and stops immediately to cause a power failure.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on FIGS. 1 to 3 and FIG. 5 described above.

FIG. 1 is a single-phase connection diagram of a power system for explaining a distributed power supply device according to an embodiment of the present invention. A commercial power supply line 33 drawn into the customer from a power supply 32 of a commercial power supply system is connected to a power receiving bus 34. Many power distribution lines 35 connected to a general load are connected to the power receiving bus 34. Further, the bus 36 of the distributed power supply system is connected to a power supply 38 such as a cogeneration system via a power supply line 37. The bus 36 is also connected to a number of distribution lines 40 for important loads. The high-speed current-limiting device 31 provided in the distributed power supply device connects the power receiving bus 34 and the bus 36 to each other, and enables interconnection operation between the commercial power supply system and the distributed power supply system. .

The high-speed current-limiting circuit device 31 includes a circuit breaker 41
, A single-phase rectifier circuit 42, and a DC reactor 43. The single-phase rectifier circuit 42 is configured by a bridge circuit of a semiconductor rectifier in which a thyristor is connected to at least one of the two AC terminals (the circuit breaker 41 side in the example of FIG. 1). By this, at the time of failure, a half cycle (10 m at 50 Hz)
The cutoff drive can be performed within sec), and then the breaker 41 is cut off. One of the two AC terminals of the single-phase rectifier circuit 42 is connected to the bus 36, and the other is connected to the power receiving bus 34 via the circuit breaker 41. A DC reactor 43 is connected between the two DC terminals of the single-phase rectifier circuit 42.

The voltages of the power supply lines 33 and 37 are supplied to undervoltage relays 47 and 48 via voltage transformers 45 and 46, respectively.
The undervoltage relays 47, 4
8 determines that a failure has occurred when the voltage of the power supply lines 33, 37 becomes a predetermined set value, for example, 85% or less with respect to the rated voltage, extinguishes the thyristor and turns off the circuit breaker. 41 is driven to shut off.

[0027] The high-speed current limiter 3 constructed as described above
1, the system impedance on the power supply 38 side is almost L
Assuming that the equivalent inductance corresponding to the internal impedance of the power supply 38 is Ls, in the present invention,
Assuming that the voltage drop rate allowed in the distributed power supply system is A, the inductance Ldc of the DC reactor 43 is given by: Ldc / Ls> (1-A) / A with respect to the equivalent inductance Ls of the distributed power supply system. ) To satisfy the relationship.

Here, as shown by reference numeral 49, when a ground fault occurs in the commercial power supply system, the voltage of the bus 36 is determined by changing the system voltage V to the equivalent inductance Ls and the inductance Ldc of the DC reactor 43. And the partial pressure is obtained. Therefore, the system voltage V ′ after the failure can be obtained by the following equation: V ′ = Ldc / (Ldc + Ls) × V (2)

Therefore, for example, when the allowable voltage drop rate A is 50%, the inductance Ldc is made equal to the inductance of the power supply 38 which is substantially equal to the equivalent inductance Ls according to the above equation (1). When a failure occurs as indicated by reference numeral 49, a voltage drop in the distributed power supply system can be suppressed to 50% of the system voltage V. Further, for example, when the allowable voltage drop rate A is 25%, the multiple Ldc / Ls is larger than 3 according to the equation 1, and the power supply 3
By setting the inductance Ldc of the DC reactor 43 to three times the inductance of 8, the voltage drop can be suppressed to 75% of the system voltage V.

As can be seen from the above equation, as the inductance Ldc of the DC reactor 43 is set to be larger, the voltage drop can be reduced. However, the voltage obtained at the time of failure depends on the set value of the undervoltage relay 48. It is desirable that:

FIGS. 2 and 3 show the results of analysis of the operation of the distributed power supply of the present invention and the above-mentioned distributed power supply when a failure occurs. FIG. 2A shows the bus voltage of the bus 36, FIG. 2B shows the interconnection current flowing through the high-speed current-limiting device 31, FIG. 3A shows the bus voltage of the bus 6, FIG. 3B shows an interconnection current flowing through the interconnection device 11. The occurrence timing of the ground fault is set to the zero cross point, and the inductance Ldc of the DC reactor 43 in the high-speed current limiter 31 of the present invention is set to be one time the inductance of the power supply 38.

As is apparent from a comparison between FIGS. 2A and 3A, in the present invention, the voltage drop is suppressed to 50% or less, and FIGS. 2B and 3B As is clear from the comparison with (1), the interconnection current is also suppressed to 以下 or less.

As described above, in the distributed power supply according to the present invention, by setting the inductance Ldc of the DC reactor 43 of the high-speed current limiting interrupter 31 based on the allowable voltage drop rate A and the equivalent inductance Ls, the commercial power supply Voltage drop at the time of failure can be suppressed to a desired level.

For example, when the allowable voltage drop rate A is 50%
In FIG. 5, the compensation range of the voltage drop is indicated by reference numeral α3 in FIG. 5, and the stable operation of the variable speed motor for power electronics application and the electromagnetic switch 39 (see FIG. 1) to which the important load is connected. Can be compensated for.

Thus, the operation of the variable speed motor and the electromagnetic switch can be compensated with low loss and low cost without using the uninterruptible power supply. by this,
The reliability in the interconnection operation can be improved, and the stress on the distributed power source can be reduced. Further, the short-circuit capacity of the electromagnetic switch 39 on the load side does not need to be increased unnecessarily by the current limiting action of the DC reactor 43 and the high-speed current interrupting action by the thyristor.
In connecting the distributed power supply system to the commercial power supply system, it is not necessary to replace the distribution line 40 and the electromagnetic switch 39.

In the high-speed current limiting device 31, the single-phase rectifier circuit 42 may be constituted by a thyristor bridge or a diode bridge in addition to the above-described mixed bridge of a thyristor and a diode. When configured with the mixing bridge and the thyristor bridge, the circuit breaker 41 may be omitted.

[0037]

According to the first aspect of the present invention, as described above, the distributed power supply device having the voltage sag countermeasure function has a single-phase rectifier circuit including a rectifying element for each phase and a DC reactor, and a failure occurs. In the case of a failure of the commercial power supply system in a distributed power supply device with a voltage sag countermeasure function that is connected to the commercial power supply system using a high-speed When the voltage drop rate that can be tolerated in the distributed power system is A, the inductance Ldc of the DC reactor is set to a value larger than (1-A) / A times the equivalent inductance Ls of the distributed power system.

Therefore, when a failure occurs in the commercial power supply system, the bus voltage of the distributed power supply system becomes equal to the equivalent inductance L.
The value of the system voltage is divided by s and the inductance Ldc of the DC reactor, and the voltage drop rate can be kept within the allowable voltage drop rate A. Thereby, only by setting the inductance Ldc of the DC reactor in correspondence with the voltage drop rate A allowed at the time of occurrence of a failure and the equivalent inductance Ls, low loss and low cost can be achieved without using an uninterruptible power supply. It can also compensate for the operation of devices susceptible to instantaneous voltage drop, such as electromagnetic switches and variable speed motors to important loads. As a result, the reliability in the interconnection operation can be improved, and the stress on the distributed power supply can be reduced. In addition, a short-circuit current can be suppressed by the current limiting function of the DC reactor, and it is not necessary to replace a circuit breaker or a cable on the load side with an undesirably large capacity at the time of interconnection.

Further, the distributed power supply device with the instantaneous sag countermeasure function according to the second aspect of the present invention is characterized in that the power supply in the distributed power supply system is a rotating machine as described above.

Therefore, it is possible to avoid the stress caused by the transient outflow of excessive current from the generator.

Further, in the distributed power supply device with the sag prevention function according to the third aspect of the present invention, as described above, the power supply in the distributed power supply system is a stationary power supply using an inverter.

Therefore, the stationary power supply has no inertia like a rotating machine and stops immediately, so that it can be particularly preferably implemented.

[Brief description of the drawings]

FIG. 1 is a single-phase connection diagram of a power system for describing a distributed power supply device according to an embodiment of the present invention.

FIG. 2 is a simulation waveform diagram for explaining an operation of the distributed power supply device according to the present invention shown in FIG.

FIG. 3 is a simulation waveform diagram for explaining an operation of the conventional distributed power supply device shown in FIG.

FIG. 4 is a single-phase connection diagram of a power system for describing a typical prior art distributed power supply device.

FIG. 5 is a graph for explaining a relationship between a voltage drop compensation range and a load operation compensation range of the distributed power supply according to the present invention and the prior art.

FIG. 6 is a single-phase connection diagram of a power system for explaining another conventional distributed power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 High-speed current-limiting circuit device 32 Power supply 33 Commercial power line 34 Power receiving bus 35, 40 Distribution line 36 Bus 37 37 Power line 38 Power supply 41 Circuit breaker 42 Single-phase rectifier circuit 43 DC reactor 45, 46 Voltage transformer 47, 48 Undervoltage relay

Claims (3)

[Claims] 1. A distributed power supply device having one or a plurality of power supplies, connected to an important load for avoiding a sag and a power failure, and being operated in parallel with an AC power supply in parallel with a commercial power system. , A high-speed current-limiting circuit device including a single-phase rectifier circuit including a rectifying element and a DC reactor, wherein an AC terminal of the single-phase rectifier circuit is a bus of a corresponding phase between the commercial power supply system and the distributed power supply system. When the DC reactor is connected between the DC terminals, and the inductance of the DC reactor is A, a voltage drop rate that can be tolerated in the distributed power supply system when a failure occurs in the commercial power supply system, A (1) of the equivalent inductance corresponding to the internal impedance of the system
-A) A distributed power supply device with an instantaneous sag prevention function, characterized in that such a high-speed current-limiting circuit breaker is formed for each phase so as to have a reactance having a value greater than / A times. 2. The distributed power supply device with a voltage sag countermeasure function according to claim 1, wherein the power supply in the distributed power supply system is a rotating machine. 3. The distributed power supply device with an instantaneous voltage reduction function according to claim 1, wherein the power supply in the distributed power supply system is a static power supply using an inverter.