JPH05284655A - Reverse charge preventing unit for distributed power supply - Google Patents

Abstract

PURPOSE:To obtain an inexpensive reverse charge preventing unit for distributed power supply by a constitution wherein ON/OFF state of a circuit breaker is detected based on presence/absence of high frequency signal superposed on a distribution line. CONSTITUTION:High frequency detectors 12a, 12B disposed on the distributed power supply 10a, 10b side make a decision whether a high frequency signal is present on a distribution line 5. Since no high frequency signal is superposed on the circuits subsequent to a distribution line 3 upon opening of a circuit breaker 2, the high frequency signal detectors 12a, 12B make a decision that the circuit breaker 2 is opened and then open switches 11a, 11b immediately. The switches 11a, 11b can be thrown in when the high frequency detectors 12a, 12b detect a high frequency signal on the distribution line 5 or a voltage being applied on the distribution line 5. According to the constitution, distributed power supply is disconnected quickly from the system and reverse charging is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when a circuit breaker of a power system is opened, promptly disconnects a distributed power source connected to its subordinate system from the system to prevent reverse charging to the power system. The present invention relates to a reverse charge prevention device for a distributed power source.

[0002]

2. Description of the Related Art A system in which direct current power of a fuel cell or the like is converted into alternating current power by an inverter and connected to a power supply system through an interconnection reactor or a transformer is widely spread from the viewpoint of effective use of energy. It is expected to do. In addition, a co-processor that uses heat and electricity effectively by using an engine and a generator
Demand for generation-type power supplies is also expected to grow. A problem when these distributed power sources are used in conjunction with the power grid is that no adequate protection scheme against reverse charging has been established.

Conventionally, in order to maintain the electric power system, if the upper circuit breaker is opened, the lower system becomes a power failure state. However, if the distributed power supply is connected to the distributed power supply, the distributed power supply may charge the lower system. Alternatively, if the distributed power supply continues to operate when the high-order circuit breaker opens and then closes again immediately after a power system accident, the voltage (amplitude, phase, etc.) between the distributed power supply and the power system will be uniform. Since it is not done, there is a risk that overcurrent will cause a failure in the distributed power supply.
From this point of view, the distributed power source connected to the power system is required to stop its operation within, for example, one second when the breaker of the system is opened. Countermeasures to prevent such reverse charging include (1) voltage and frequency anomaly detection (2) phase monitoring (3) harmonic waveform distortion monitoring, and other passive measures.

(4) The frequency, voltage, current, AC power such as active power or reactive power is always slightly changed,
Active measures such as detection are being considered by utilizing the fact that the fluctuations are increased by opening the upper circuit breaker. These are carried out by the manufacturer of the distributed power source, but there are also plans to individually cut off the transfer from the power company side.

Electric power companies and the like have evaluated their respective performances in the above-described method for preventing reverse charging on the distributed power source side, but in reality, there is nothing that can be said to be sufficient in terms of reliability. This will be described with reference to FIG. FIG. 4 is the same as FIG. 5 described as a conventional example in Japanese Unexamined Patent Publication No. 64-23726, in which 101 is a DC power source such as a fuel cell, and 102 is a DC voltage supplied from the DC power source 101. An inverter for conversion, 103 is an interconnection reactor for connecting the inverter 102 and the AC system, and 104 is a switch for connecting or disconnecting the inverter 102 and the AC system. When the circuit breaker 118 operated by the upper power company is broken, the switch 10
4 needs to be opened after a predetermined time.

Reference numeral 105 is an AC system distribution line, 106 is a load, 107 is a voltage detector, 108 is a current detector, and 109 is a current detector.
Is the reference value P ^{* of} the active power output by the inverter 102 ^. Active power setter 110 for setting the active power setter 10
A phase calculator to which the output of 9 is applied, and 111 adds the output θ1 of the phase calculator 110 and the output θs of the power supply phase calculator 112 to obtain the phase reference θI ^* of the inverter 102 ^. , 113 is a reference value Q ^{* of} the reactive power output from the inverter 102 ^. , 114 is an adder that adds the output of the reactive power calculator 116 and the output of the reactive power setter 113 to the amplifier 115, and 117 is the output of the voltage detector 107 and the output of the amplifier 115. Addition and inverter amplitude reference VI ^* Is an adder for obtaining. The reactive power calculator 116 calculates and calculates the reactive power from the output of the voltage detector 107 and the output of the current detector 108.

The inverter 102 has a system voltage Vs and a phase θ.
The values of the inverter voltage VI and the phase θI are output to s to control the reactive power and the active power. FIG. 5 is an example of the schematic diagram and shows an operating state with a power factor of 1 in which the phases of the system voltage Vs and the output current I match.

As can be seen from FIG. 4, after the system voltage Vs is detected by the voltage detector 107, the phase reference θI ^{* is} supplied to the inverter 102 ^. And amplitude reference VI ^* Is giving. Therefore, even when the circuit breaker 118 is opened, Vs
The control system is maintained by considering the output voltage from the controller 102 as the system voltage, but normally, when the circuit breaker 118 is opened, a slight change occurs in the system voltage Vs. As a result, positive feedback is applied to increase or decrease the voltage, or Since the frequency increases or decreases, it can be judged as abnormal. If it is judged as abnormal, the switch 1
04 is open.

However, when the generated output of the inverter 102 and the power consumption of the load 106 are completely equal to each other, no change occurs when the breaker 118 is opened, and as a result, the abnormality does not appear easily. Therefore, a method has been considered in which the voltage, the phase, the active power, the reactive power, and the like are constantly slightly changed so that the abnormality appears faster when the breaker 118 is opened.

By the way, the measures mentioned in (1) to (4) are insufficient when (1) to (3) are the cases where the generated power of the distributed power source and the load that consumes it completely match. This is because it is considered that there is theoretically no abnormality as described above, and in (4) it is theoretically possible to cancel out if multiple distributed power sources cause different fluctuations.

An example of giving a frequency variation to the inverter 102 is disclosed in Japanese Patent Laid-Open No. 3-239124. Focusing on the frequency spectrum of the voltage generated by the generator,
A frequency spectrum different from this is generated in the inverter, and it is utilized that the frequency spectrum peculiar to the inverter increases when the system is dropped. It is considered that this also leaves a problem when a large number of inverters are connected, and it is theoretically possible that the inverter that gives fluctuations is accidentally out of order. On the other hand, the transfer interruption mentioned as a measure by the electric power company has a defect that it is impossible to construct an unspecified number of distributed power supply systems, although it is certain.

[0012]

In a state where a large number of distributed power sources are installed, when the upper circuit breakers of the power system are opened, the distributed power sources are quickly disconnected from the system to prevent reverse charging. Measures are desired.

The present invention has been made to solve the above-mentioned problems, and the distributed power source is not limited to the inverter, but is effective not only for the power generation system of cogeneration but also for an inexpensive distributed power source. It is to provide a backflow prevention device.

[0014]

The above object is to provide a plurality of distributed power sources connected to lower distribution lines of a circuit breaker via switches, respectively, and a distribution line side or a distributed power source side of each of the switches. And a device for detecting a unique signal which is respectively provided in the distribution system, a device for injecting a unique signal to the distribution system on the upper side of the circuit breaker, and a device for opening the circuit breaker. Sometimes this can be achieved by providing the device for detecting the unique signal with means for opening the switch when the device detects the unique signal.

Further, the above object is to provide a plurality of distributed power sources which are respectively connected to the lower distribution lines of the circuit breaker via switches, and are provided on the distribution line side or the distributed power source side of the respective switches. A device that detects a unique signal intermittently superimposed on a distribution system and generates a synchronization signal, and a device provided on the upper distribution system of the circuit breaker, and intermittently injects a signal unique to the distribution system. A device, a high-frequency oscillator, and an output signal of the high-frequency oscillator, which divides the output signal to output a low-frequency signal, and the low-frequency signal is synchronized by the synchronization signal; This can be achieved by varying the AC input amount of the power source and providing a means for opening the switch by detecting that the output AC amount of the distributed power source increases when the breaker is opened.

[0016]

As described above, the open / closed state of the circuit breaker can be easily detected by the presence / absence of the signal superimposed on the distribution line. Further, since the transmitters inside the distributed power sources are synchronized by using the signals intermittently superimposed on the distribution lines, the fluctuations in the amount of alternating current are the same for each distributed power source. As a result, the fluctuations of a large number of distributed power sources do not cancel each other out, and thus various reverse charging prevention measures that could lose their effects due to the conventional cancellation can be implemented.

[0017]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1, 3, and 5 are distribution lines, 2 is a circuit breaker operated by a power company, 4 is a transformer, and 6 is a distribution system. 1 is a device for generating a unique signal to be injected into the device 1, and a high frequency signal injection device can be used as an example of this device. Again 10
Is a distributed power source, 11 is a switch provided between the distributed power source 10 and the distribution line 5, and this switch is opened when the breaker 2 is cut off. Reference numeral 12 is a device for detecting a unique signal injected into the distribution system, which is a high frequency signal detection device in this example. A large number of distributed power sources 10 are provided, but here 2
The tables are distinguished by adding subscripts a and b. The high frequency signal injection device 6 is, for example, "Handbook of Electrical Engineering", Showa 6
As some methods are explained in 8.2.3 Distribution Line Conveying Method on page 1272 issued by The Institute of Electrical Engineers of Japan in February 3rd,
It is a device that can directly superimpose signals on distribution lines.
Generally, this distribution line transportation system is used for remote monitoring and control of devices connected to a distribution system. In a familiar example,
This method is also used to control home water heaters. In this way, it is possible to use the high-frequency signal already superposed on the distribution line, and it suffices to provide a device for receiving this signal on the distributed power supply 10 side. The high-frequency signal detection device 12 provided on the side of the distributed power source 10 is a device for determining whether or not there is a high-frequency signal on the distribution line 5. Is not superposed, the high-frequency signal detection device 12 judges that the circuit breaker 2 is opened, and opens the switch 11 immediately by an opening / closing means (not shown) that controls the opening / closing of the switch 11 in response to the high-frequency signal detection device 12. I can do it. The switch 11 can be turned on when the high-frequency signal detection device 12 detects that the distribution line 5 has a high-frequency signal or that the distribution line 5 has a voltage.

When the high-frequency signal detection device 12 is provided on the load side (distributed power supply side) of the switch 11, the switch 11 can be opened because the high-frequency signal disappears from the distribution line 5.
The charging can be performed by another voltage or frequency detecting means (not shown).

FIG. 2 showing the same parts as in FIG. 1 with the same symbols.
FIG. 8 is a flock diagram showing another embodiment of the present invention. Figure 1
However, the signal of the high frequency signal injection device 6 must be transmitted continuously, but the embodiment of FIG. 2 is a high frequency signal injection device that generates intermittent transmission, for example, once every 10 hours. 6 shows an example in which 6 is used, and the operation of FIG. 2 will be described with reference to FIG.

In FIG. 3, f1 is a signal of the high frequency signal injection device 6 which is emitted once every 10 hours, f2 is a signal f1 of the high frequency signal injection device 6, and the signal f1 of the high frequency signal injection device 6 is detected. A pulse signal output from the high-frequency signal detection device 12 according to the output timing, f3 is a signal indicating the oscillation frequency of the oscillator 13 such as a crystal oscillator in a pulse train, and f4 is a frequency division of the pulse signal f3. For example, with a signal of about 1 Hz, the amount of alternating current of the dispersed power source 10 is changed based on this signal. Here, f4 is a signal that changes the amount of alternating current of the distributed power supply 10a, and f5 is a distributed power supply 10
It is a signal for changing the AC amount of b.

In the embodiment shown in FIG. 2, the output signal f2 of the high-frequency signal detector 12 is synchronized with the output signal of the oscillator 13. That is, the output signal f2 of the high frequency signal detection device 12 causes the oscillators 13a, 1
The output signals f4 and f5 of 3b are synchronized, and even if the output signals f4 and f5 of the oscillators 13a and 13b are deviated by θ just before the output signal f2 of the next high frequency signal detecting device 12 is generated. The signal f2 will be synchronized.

Output signals f4, f of the oscillators 13a, 13b
5 is a low-frequency signal, which is used for the fluctuation of the alternating current amount described in the method (4) of the prior art. That is, in the prior art, since there are many variations in the alternating current amount of the distributed power source 10, they may cancel each other's actions. However, according to the embodiment of FIG. Since it fluctuates in synchronism with the signal F2 from 6, the fluctuations do not cancel each other out. That is, if the crystal oscillator is used as the internal oscillator of the oscillator 13 as described above, the frequency accuracy is high, and therefore it is not necessary to continuously provide the synchronization signal. For example, the oscillation frequency of the crystal oscillator is set to 1 MHz and this frequency is divided to 10
Assuming that the oscillator of Hz is used and the alternating current amount is changed by using the oscillator, it is when the 180 ° phase shift occurs that the changes in the alternating current amount of the two units cancel each other. That is, if the frequency that was originally synchronized is shifted by 0.5 Hz after T time,
The frequency accuracy is 0.5 / (T · 3600) = 1.38 · 10 ⁻⁴ / T.

When T is 10 hours, it is 1.38 · 10 ⁻⁵ , which is a possible value for a crystal oscillator. Therefore, the method of synchronization is a technique that is commonly used, so a detailed description thereof will be omitted, but synchronization may be performed several times a day. Transmitters 13a, 13b
In the circuit of FIG. 4, the signals f4 and f5 of
The variation can be superimposed by the method of adding to 1,114 or 117.

When the circuit breaker 2 is cut off for some reason,
Since the fluctuation of the output AC amount of the distributed power source 10 increases, the switch 11 is opened by the opening / closing control means that detects the increase of the fluctuation of the AC amount and opens / closes the switch 11.

In the above description, the high frequency is used as the unique signal to be injected into the distribution system, but the distribution line carrier system is the audio frequency voltage signal system (ripple system) or the voltage change signal system (dip system). There are others available as well.

[0026]

As described above, according to the present invention, a signal unique to a power distribution system is used, and the presence or absence of that signal or the AC amount of the distributed power source output from the oscillator is changed to a signal. The open circuit breaker is identified by synchronizing and changing the AC amount of the distributed power source to increase the AC amount. (1) 100% detection is theoretically possible under all conditions. (2) It is economical because it is possible to use the existing distribution line transportation method. (3) It is possible to use various devised methods that utilize fluctuations in the amount of alternating current. (4) It is not necessary to install a detector according to this method in all of the distributed power sources, and for example, a distributed power source other than the inverter may be mixed. (5) In the prior art, detection may be delayed if the load includes a rotating machine, but this method does not. (6) Instead of the electric power company controlling the operation of each device,
Since the distributed power supply side has a judgment function, it is possible to construct an unspecified number of distributed power supply systems. Such effects can be obtained and contribute to the spread of distributed power sources.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a waveform diagram for explaining the operation of the embodiment shown in FIG.

FIG. 4 is a block diagram showing a configuration example of a distributed power supply to which the present invention is applied.

FIG. 5: Vector diagram showing the relationship between system voltage and inverter voltage

[Explanation of symbols] 1, 3, 5 ... Distribution line 2
… Circuit breaker 4… Transformer 6
... High-frequency signal injection device 10a, 10b ... Distributed power supply 11a, 11b
... Switches 12a, 12b ... High-frequency signal detection devices 13a, 13b
… Transmitter 101… DC power supply 102
… Inverter 103… Reactor 104
… Switch 105… Distribution line 106
... load 107 ... voltage detector 108
… Current detector 109… Active power setting device 110
... Phase calculator 111 ... Adder 112
… Power supply phase calculator 113… Reactive power setting device 114
... Adder 115 ... Amplifier 116
... Reactive power calculator 117 ... Adder 118
… Circuit breaker

Claims (2)

[Claims] 1. A plurality of distributed power sources, each of which is connected to a lower-side distribution line of a circuit breaker via a switch, and a plurality of distributed power sources provided on the distribution line side or the distributed power source side of each of the switches and superposed on a distribution system. A device for detecting a unique signal, a device for injecting a signal unique to the power distribution system provided in a distribution system on the upper side of the circuit breaker, and a device for detecting the unique signal when the circuit breaker is opened A reverse charge prevention device for a distributed power source, which comprises means for opening the switch when the unique signal is detected by. 2. A plurality of distributed power sources, which are respectively connected to the lower distribution lines of the circuit breakers through switches, and a plurality of distributed power sources, which are respectively provided on the distribution line side or the distributed power source side of the respective switches, are intermittent in a distribution system. And a device for generating a synchronization signal by detecting a unique signal that is superposed, and a device provided in a distribution system on the upper side of the circuit breaker for intermittently injecting a signal unique to the distribution system, and a high frequency An oscillator and an output signal of the high-frequency oscillator are frequency-divided to output a low-frequency signal, the low-frequency signal being synchronized by the synchronization signal, and an AC input of the distributed power source by the low-frequency signal. Change the amount,
Also, a reverse charge prevention device for a distributed power source, comprising means for detecting that the output AC amount of the distributed power source expands when the breaker is opened and opening the switch.