WO2000013290A1

WO2000013290A1 - Parallel operation device

Info

Publication number: WO2000013290A1
Application number: PCT/JP1999/004695
Authority: WO
Inventors: Nariisa Imoto
Original assignee: Nariisa Imoto
Priority date: 1998-08-31
Filing date: 1999-08-31
Publication date: 2000-03-09
Also published as: AU5445999A

Abstract

A parallel operation device, wherein, in order for a higher-voltage power source (e1) to be consumed preferentially in parallel-operating the main power source (e1) and an auxiliary power source (e2), respective source terminals (S1) and (S2) of an FET switch (SW1) and an FET switch (SW2) are interconnected, drain terminals (D3) and (D4) of a two-way switch (2) using as both ends thereof respective drain terminals (D1) and (D2) of SW1 and SW2 are connected between the input terminal and the output terminal of the auxiliary power source (e2), the both ends of the main power source (e1) are connected to a detection voltage input terminal of a control unit (3), and gate terminals (G1, G2, G3, G4) which control conduction directions of two-way switches (1, 2) are respectively connected to the control output terminal of the control unit (3).

Description

Description Parallel operation equipment Technical field

The present invention provides a power failure countermeasure device or a cogeneration system that can continue to supply power to a load without a momentary power failure even when a power failure such as a power failure due to a natural disaster or man-made disaster occurs by parallel operation of a plurality of power supplies. Wind power generation, solar power generation, engine power generation, in-house power generation and other various power generation equipment (hereinafter abbreviated as special power supply), battery power supply, inverter power supply, UPS (uninterruptible power supply), commercial power supply, etc. The present invention relates to a high-efficiency parallel operation device or an economical parallel operation device using an arbitrary combination of a plurality of power sources, or a parallel operation device for increasing the electric capacity. Background art

One of the external causes of problems with electronics products is the disturbance of electricity. A device that completely guards against such power supply problems is an uninterruptible power supply as a power failure countermeasure, and is usually called a UPS. UPS is an acronym for Uniterruptible Power System, and was formerly called CVCF power supply. . In recent years, the environment has been rapidly changing, such as the downsizing of computers and the decentralized system using networks, and in response, UPS has been downsizing in the same way as computers, and from specific companies to general companies. Is infiltrating.

Abnormal phenomena that occur in the commercial power system, such as instantaneous low voltage and instantaneous power outage due to falling down, power outage due to disaster or human error, fluctuation of peripheral load, and power supply situation

Replacement form (Rule 26) It has the ability to cope with various power failures such as voltage fluctuations and noise, and is becoming essential in the advanced information society.

The mainstream of the conventional UPS technology system is the “always-inverter power supply system”, but when the UPS is configured according to the present invention, it becomes the “new always-on commercial power supply system”, and the power consumption of the main unit during operation, reactive power, Power supply harmonic current, battery utilization, electromagnetic interference, noise, etc. can be remarkably improved, and low-cost, high-efficiency, high-performance UPS that switches to sine wave voltage output, power outage, over voltage, and low voltage without interruption. It is possible. Disclosure of the invention

According to the present invention, during normal operation, the power supply having the higher selected voltage becomes the main power and is consumed preferentially, and the burden on other power supplies (standby power supply and backup power supply) is reduced. In the event of failure or power down due to man-made disaster, economical operation of multiple power supply parallel operation equipment or combined power supply equipment that enables continuous power supply by a standby power supply without any momentary power outage and enables non-stop operation of important equipment To provide a parallel operation device with multiple power supplies for the purpose of providing more economic benefits.

In the parallel operation device according to the first invention, a common load (hereinafter abbreviated as a load) is provided through an AC switch (hereinafter, referred to as a bidirectional switch) capable of controlling a plurality of power supplies in a conduction direction. ).

In such a configuration, by controlling the conduction direction of each bidirectional switch in synchronization with the voltage polarity or the current polarity of the main power supply, each power supply can provide a diode-OR of a DC voltage in the positive region and the negative region, respectively. Circuit (diode OR circuit) operates in parallel, and high-voltage power is preferentially supplied to the load and consumed. For example, if the backup power supply voltage inside the battery is set lower than the main power supply voltage, the main power supply voltage will always be applied to the load, and the battery will not be consumed normally (when the main power supply is normal). May

Replacement form (Rule 26) When the mains voltage is lower than the voltage of the backup power supply due to the power supply failure or power down, the voltage of the backup power supply is automatically applied to the load. As a result, the power supply can be backed up without any interruption, and the life of the battery is extended. In addition, if the commercial power supply is used as the main power supply, an uninterruptible power supply of the always commercial power supply type that can perform backup without interruption in case of power failure can be constructed. Further, when the special power supply is used as a main power supply and the commercial power supply is used as a standby power supply, the special power supply is consumed preferentially, so that the amount of power consumption of a normal commercial power supply is reduced and electric power is reduced. Cost savings. In addition, the two-way switch connected to the main power supply is normally turned on (conducting state) in both directions, and all other power supplies are synchronized with the compressive polarity or current polarity of the main power supply. Controls the conduction direction of the two-way switch, and if an abnormality occurs in the main power supply, turns off the conduction control of the two-way switch connected to the main power supply (non-conduction state) The same effect can be obtained even if. Further, when an overvoltage, an abnormal waveform, an abnormal frequency, or another abnormal state occurs by detecting each voltage or current of the plurality of power supplies by the control unit, the two-way switch connected to the abnormal power supply By setting the conduction control to the 0FF state, the abnormal power supply can be cut off from the parallel operation and the parallel operation device can be protected.

In the parallel operation device according to the second invention, the power supply having the highest voltage is used as the main power supply, and the main power supply is connected to the load only through the protection switch without passing through the bidirectional switch. All power sources are connected to a load through a bidirectional switch.

In such a configuration, each power supply is normally controlled by closing the protection switch and controlling the conduction direction of each bidirectional switch in synchronization with the voltage polarity or current polarity of the selected main power supply. In the negative region and the negative region, the main power having a high voltage is preferentially supplied to the load, and the same effect as the first invention can be obtained when the output side of the main power is disconnected other than a short circuit or equivalent failure. Ma

Replacement paper (Kaikai IJ26) When the output side of the main power supply is short-circuited or equivalent failure, the protection switch is automatically opened by detecting the voltage signal or current signal of the main power supply by the control unit, and the main power supply is disconnected from the parallel circuit. Therefore, the same effect as the first invention can be obtained.

Further, a parallel operation device according to a third aspect of the present invention is the parallel operation device according to the first aspect of the invention, in which a voltage regulator is incorporated between each power supply and each two-way switch as needed.

In such a configuration, a difference in the magnitude of the voltage of each power supply can be provided by the inserted voltage regulator, so priority is given to the use of the power supply, and in the parallel operation of a plurality of off-the-shelf power supplies, the same as in the first invention The effect of is obtained.

In addition, the parallel operation device according to the fourth invention is characterized in that a plurality of batteries charged by the main power supply or a storage device such as an electric double layer capacitor or a general capacitor (hereinafter referred to as a capacitor) is replaced by an arbitrary number of capacitors. A back-up power supply is configured through a switch circuit, an inverter circuit for polarity reversal, and an AC filter configured so that they can be connected in series or in parallel in any combination, and the main power supply and the back-up power supply are respectively connected to two. It is connected to a load through a directional switch.

In such a configuration, a function generating circuit can be configured by a combination of a plurality of capacitors and a series-parallel switch circuit, and a sine wave voltage having a lower voltage than the main power supply can be efficiently generated. When the output voltage is AC, the inverter circuit for polarity reversal is unnecessary. Normally, the battery is charged through the charging circuit while consuming the main power preferentially. If the main power is abnormal, the same effect as in the first invention can be obtained because the power supply to the load is backed up without any instantaneous interruption. Can be If the number of dragons is n, the number of battery combinations is two. A street can be generated voltage of 2 ^[pi as the control of the series-parallel sweep rate Tutsi circuit.

Replacement paper (Kaikai IJ26) In addition, the parallel operation device according to the fifth invention is characterized in that the inverter (DC-AC converter) power supply and the main power supply, which are charged by the main power supply, are built-in through a bidirectional switch. It is connected to a load.

In such a configuration, a sine wave can be generated by PWM (Pulse Width Modulation) control or PAM (Pulse Amplitude Modulation) control of the inverter, and the same effect as the fourth invention can be obtained.

Further, the parallel operation device according to the sixth invention is such that a backup power supply for generating a predetermined voltage by a battery is connected to the load through a two-way switch, and the main power supply is connected to the load through the overload protection device and the two-way switch. And an overvoltage protection device such as a surge absorber connected between the output side of the overload protection device and the main power supply.

In such a configuration, when an overvoltage occurs in the main compress line due to a surge or the like, an overcurrent flows through the overload protection device by the operation of the overvoltage protection device, and the abnormal power supply line is generated by the protection operation of the overload protection device. Can be shut off. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a main electric circuit block diagram and an explanatory diagram of a preferred parallel operation device according to the first invention.

FIG. 2 is a block diagram of a main electric circuit of a parallel operation apparatus showing another embodiment according to the first invention.

FIG. 3 is a main electric circuit block diagram of a preferred parallel operation device according to the second invention.

FIG. 4 is a block diagram of a main electric circuit of a parallel operation device showing another embodiment according to the first invention.

Fig. 5 shows the main electric circuit of the preferred parallel operation system according to the fourth invention.

Replacement form (Rule 26) FIG.

FIG. 6 is a block diagram of a main electric circuit of a parallel operation device showing another embodiment according to the fourth invention.

FIG. 7 is a voltage waveform diagram of an embodiment according to the fourth invention.

FIG. 8 is a main electric circuit block diagram of a preferred parallel operation device according to the fifth invention.

FIG. 9- (a) is a block diagram of a main electric circuit of a preferred parallel operation device according to the third invention.

FIG. 9- (b) is a main electric circuit block diagram of a parallel operation device showing another embodiment according to the third invention.

Fig. 9-(c) is a block diagram of a main electric circuit of a preferred parallel operation device according to the sixth invention. BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail with reference to the accompanying drawings. The members, S3 arrangements, and the like described below do not limit the present invention, and can be variously modified within the scope of the present invention.

FIG. 1 (a) is a block diagram of a main circuit of a preferred parallel operation device according to the first invention, which is the basis of the entire present invention. As shown in Fig. 1 (a), in order to operate the main power supply e1 and the standby power supply e2 in parallel so that the higher voltage power supply e1 is consumed preferentially, the FET switch SW1 is used. And the respective source terminals S1 and S2 of the FET switch SW2 are connected to each other, and the bidirectional switch 1 having both the drain terminals D1 and D2 of SW1 and SW2 at both ends is connected to the input terminal of the power supply e1. Connect between the output terminals, and similarly connect the drain terminals D 3 and D4 of the bidirectional switch 2 between the input terminal and the output terminal of the spare pack e2, and connect both ends of the main power supply e1. Detection voltage input terminal of control unit 3

Replacement form (Rule 26) Gate terminals G 1, G 2, G 3, and G 4 for controlling the conduction direction of the bidirectional switches 1 and 2, respectively, are connected to the control output terminals of the control unit 3. As shown in FIG. 1 (d), the power supplies el and e2 have voltage waveforms like e (t), respectively, and the gate G1 and the gate G3 while the voltage of el (t) is positive. Is in the active state, gates G2 and G4 are inactive, switch SW1 and switch SW3 are closed, and switch SW2 and switch SW4 are open. The equivalent circuit in this case is shown in Fig. 1 (b). While the voltage of el (t) is negative, the gate G1 and the gate G3 are in the non-driving state, the gate G2 and the gate G4 are in the active state, and the switch SW1 and the switch SW 3 is open, and switch SW2 and switch SW4 are closed. The equivalent circuit in this case is shown in Fig. 1 (c). The switching timing of switches SW1, 2, 3, and 4 is synchronized with the polarity of the voltage or current of the main power supply voltage e1 (t) and the zero point as shown in Fig. 1 (d). Let it. Specifically, for example, the zero point of the main power supply compress el (t) is set as the first reference point, and the reference point having the same cycle as the first reference point generated by the control unit 3 is set as the second reference point. Switches SW 1, 2, 3, and 4 are switched by the signal of the logical sum of the first reference point and the second reference point. Therefore, when the first reference point does not come out due to the failure of the main power supply, the drive of the switches SW1, 2, 3, and 4 is automatically continued by the signal of the second reference point. The generation of the second reference point can be realized by an analog circuit or a digital circuit, or by a computer and a software. In addition, the bidirectional switch can be configured by a semiconductor switch such as a triac, an IGBT, a thyristor, a transistor, a SIT, and a GTO in addition to the FET semiconductor switch, and an embodiment thereof is shown in FIG. .

As another embodiment, as shown in FIG. 2 (a), the embodiment of FIG. 1 (a) is represented by a contact switch and a diode. In FIG. 2 (a), while the compressing pressure of e1 (t) is positive, the contact switches SW1 and SW3 are switched on.

Replacement form (Rule 26) Close and open contact switch SW2 and contact switch SW4. The equivalent circuit in this case is shown in Fig. 1- (b). While the voltage of e (t) is negative, the contacts of switch SW1 and switch SW3 are opened, and the contacts of switch SW2 and switch SW4 are closed. The equivalent circuit in this case is shown in Fig. 1 (c). The switching timing of the switches SW1 to SW4 is based on, for example, detecting the zero point of e1 (t). The same effect can be obtained by replacing the contacts of switches SW1 to SW4 with semiconductor switches such as triacs, FETs, IGBTs, thyristors, transistors, SITs, GTOs, and non-contact switches.

As another embodiment, as shown in Fig. 2 (b), when three-phase power supplies are operated in parallel, two-way switches are connected to each phase, and each phase of the main power supply is connected. Each bidirectional switch is controlled in synchronization with the voltage or current of the switch.

FIG. 3 is a main electric circuit block diagram of a preferred parallel operation device according to the second invention. As shown in Fig. 3 (a), connect the main power supply el to the protection switch 17 between the input terminal and the output terminal, and output the backup power supply e2 through the bidirectional switch 2. Connect the rain end of the main power supply e1 to the detection voltage input terminal of the control unit 3, and control the gate terminals G3 and G4 that control the conduction direction of the bidirectional switch 2. It is connected to the control output terminal of section 3, the compress detector CT is installed on the main power supply line, and the output of the current detector CT is connected to the detection current input terminal of control section 3.

Normally, the protection switch 17 is closed and the main power supply el is used preferentially.When an abnormality in the voltage or current of the power supply el is detected, the protection switch 17 is opened. Then, the same effect as the first invention is obtained. As the protection switch 17, an AC switch, a contactless relay or an electromagnetic switch shown in Fig. 4 can be used. The equivalent circuits under normal operating conditions are shown in Fig. 3 (b) and Fig. 3 (c). FIG. 9 (a) is a block diagram of a main electric circuit of a preferred parallel operation device according to the third invention. First block diagram of main electric circuit block diagram according to first invention

Replacement form (Rule 26) In FIG. 1 (a), as shown in FIG. 9 (a), a series transformer Tr is inserted as a voltage regulator 13 between the standby power source e2 and the bidirectional switch 2. Since the voltage e2 can be set to e2-e5 by the series transformer Tr, and the voltage el> the voltage e2, the same effect as the first invention can be obtained.

As another embodiment, in FIG. 1 (a) of the first invention, as shown in FIG. 9 (b), as shown in FIG. 9 (b), a series transformer is provided as a voltage regulator 13 between the standby power source e1 and the bidirectional switch 1. When the transformer Tr is inserted, the voltage e1 can be changed to e2 + e5 by the series transformer Tr, and the voltage e1> the voltage e2, so that the same effect as the first invention can be obtained. .

FIG. 5 is a block diagram of a main electric circuit of a preferred parallel operation device according to the fourth invention, which is made as an embodiment when the number of capacitors is six (n = 6). As shown in Fig. 5, the six secondary windings of the transformer Tr1 with the primary winding connected to the main power supply e1 are connected to the six charging circuits 7, respectively, and the outputs of the charging circuit 7 Are connected to the capacitors C1 to C6, the capacitors C1 to C6 are connected to the input side of the switch circuit 5, the output of the switch circuit 5 is connected to the input side of the inverter circuit 4, Connect the output side of the inverter circuit 4 for polarity reversal to the input side of the filter F, connect the control output of the controller 9 to the gate terminal of each control switch, and control the el and e2 voltage detection signals. Connects to the detection signal input terminal of section 9, and has a built-in backup power supply with the output voltage of filter F as e2. Main power supply e1 and backup power supply e2 are the same as Fig. 1 of the first invention-(a) In parallel.

There are 2 ^s (= 6 4) combinations of 6 capacitors in series connection, V 2 = 2 XVI, V 3 = 4 XV 1, V 4 = 8 XV 1, V 5 = 16 XV 1, V When 6 = 3 2 XVI, the output of the switch circuit 5 can be varied in steps of VI from 0 to 63 XV1 to generate a sine wave with a resolution of 1 to 63, and the reactive power is reduced. The size is very small, the AC filter is very small, and the utilization of each capacitor is improved. The number of capacitors can be determined as needed, the charging circuit

Replacement form (Rule 26) 7 controls the charging of the battery.

As another embodiment, as shown in FIG. 6, a main power supply e1 is connected through a charging circuit 7 to both ends of a series circuit of capacitors C1 to C6, and each of the capacitors C1 to C6 is connected. The same applies to the case where the input of the switch circuit 6 is connected to the input side of the switch circuit 6 and the output of the switch circuit 6 is connected to the input side of the polarity inverting inverter 4. The output of the switch circuit 6 can be varied in steps of VI from 0 to 6 XV 1 when the voltages V2 to V6 are all equal to VI, and can generate a sine wave with a resolution of 16 Can be.

FIG. 7 shows the voltage waveforms of the output e3 of the function generating circuit of the present invention and the output e2 of the filter F. Also, by installing three backup power supplies 15 and controlling the phase of each output voltage, it is possible to handle three-phase power supplies.

FIG. 8 is a main electric circuit block diagram of a preferred parallel operation device according to the fifth invention. Fig. 8—As shown in (a), the main power supply e1 is connected to the input side of the charger C and the inverter circuit 12 through the rectifier circuit 10 and the charging circuit 11 and the inverter circuit 12 is connected. The output side is connected to the input side of the filter F, the control output of the control section 18 is connected to the charging circuit 11 and each switch control terminal of the inverter 12 and the voltage detection signals of el and e 2 are connected. Connects to the detection signal input terminal of the control unit 18 and has a built-in backup power supply with the output voltage of the filter F as e2. The main power supply e1 and the backup power supply e2 are shown in Fig. 1 of the first invention. And connected in parallel as in The charging of the battery C is controlled by the charging circuit 11, and the voltage and frequency are adjusted by the control of the inverter circuit 12. Further, when the rectifier circuit 10 is constituted by a thyristor, the charging current of the capacitor C can be adjusted even if the voltage regulator 11 is omitted. Fig. 8 (b) shows an embodiment in the case of three phases. FIG. 9 (c) is a block diagram of a main circuit of a preferred parallel operation device according to the sixth invention. Fig. 9—As shown in (c), the output e2 of the backup power supply 15 that generates a predetermined voltage by the capacitor is connected to the bidirectional switch 2.

Replacement paper (Kaikai IJ26) To the output terminal through the overload protection device 16 and the bidirectional switch 1 from the input terminal of the main power source e1, and to the output side of the overload protection device 16 An overvoltage protection device 14 such as a surge absorber is connected between the power supply el and the power supply el.

When the overload protection device 16 performs the protection operation due to the operation of the overvoltage protection device 14 when an overvoltage occurs and the main power supply e1 is cut off, the power is supplied instantaneously by the backup power supply 15 to the first invention. This has the same effect as the first embodiment. As the overload protection device 16, a switch that is opened due to an overcurrent such as a fuse, a thermal switch, a fuse breaker, or an earth leakage breaker is preferable. Throughout the present invention, the same effects are exhibited not only for single-phase power supply but also for single-phase three-wire power supply, three-phase power supply, three-phase four-wire power supply, multi-phase power supply, and DC power supply. At the same time as backup, the alarm signal can be sent to an external device and an alarm signal can be sent to an external device, or data can be output to monitor the charge status of the battery, such as charge, voltage, current, and temperature. Can be remotely controlled. In addition, the performance of each control switch can be improved by the parallel operation of the semiconductor switch and the contact switch. In addition, reference numerals 1 and 2 in the figure are switches capable of two-way control or {NZ} FF control composed of a semiconductor switch or a contact switch, and 3, 9, and 18 are hardware. An arithmetic and control device consisting of one or software, L is an electric load, 4, 5, and 6 are switch circuits consisting of semiconductor switches or contact switches, 7 is a rectifier or rectifier circuit, or voltage and current regulation. Possible charging circuits, 1 1 is a chopper circuit for voltage adjustment, 1 2 is an inverter composed of semiconductor switches such as transistors, IGBTs, SITs, thyristors, and GT 0. 13 are various voltage regulators or stabilizing power supplies such as voltage conversion method using transformer, thyristor phase control method, switching method, inverter method, etc., and 14 is surge voltage absorption. Element or overvoltage protection device.

Replacement form (Rule 26) Industrial applicability

As described above, when the parallel operation device according to the present invention is used as a power failure countermeasure device, the present invention can reduce the electric energy consumption by 20 to 28% compared to the conventional system. Compared to the conventional method, there is much less loss, and all the loss is changed to heat. Therefore, it is possible to save only the difference in efficiency for cooling-related items. Battery use is also reduced.

Nowadays, the rationalization of energy use is very important from the viewpoint of environmental improvement and effective use of resources, which are issues common to all humankind. High-precision equipmentResearch equipment requires a highly reliable UPS with low running cost as a power failure countermeasure device, and a high-efficiency parallel operation device or economical system using any combination of the special power supply and commercial power supply There is also a growing need for intelligent parallel operation equipment. Also, due to environmental issues, there is a high demand for the reduction of the amount of batteries used, which can bring economic effects to a wider range of industries.

Replacement form (Rule 26)

Claims

The scope of the claims

1. As the first invention, two FET semiconductor switches are connected in series in the opposite direction to each other in order to operate two or more power supplies in parallel and use the power supply with the higher voltage preferentially. To form an AC switch (bidirectional switch) capable of controlling the conduction direction. The same number of bidirectional switches as the plurality of power supplies are used as input terminals and a common output terminal (hereinafter referred to as output) for connecting a load. And a voltage signal or a current signal of a power supply selected from the plurality of power supplies (hereinafter referred to as a main power supply) is connected to a signal detection input terminal of a control unit. A parallel operation device comprising a control output of a control unit connected to a conduction direction control input terminal of the two-way switch.

2. As a second invention, in the configuration of the parallel operation device of the first invention, the power supply having the highest voltage is connected from the input terminal to the output terminal only through the protection switch without passing through the two-way switch, and The parallel operation device according to the first invention, wherein all power supplies are connected to output terminals through two-way switches.

3. As a third invention, in order to provide a difference in the magnitude of the voltage of each power supply during parallel operation of a plurality of power supplies and to give priority to the use of the Oshi source, the voltage is adjusted from the input terminal to which each power supply is connected. The parallel operation device according to the first invention or the second invention, characterized in that the parallel operation device is connected to an output terminal through a switch and a bidirectional switch.

4. As the fourth invention, an arbitrary number of Oshiike or electric double-layer capacitors or general capacitors (hereinafter referred to as capacitors) charged by the main power supply can be connected in series or parallel in any combination in any number. The input side of the switch circuit is connected to the capacitor, the output side of the switch circuit is connected to the input side of an inverter circuit for inverting the polarity, and the output side of the inverter is the input side of an AC filter. And the control terminals of the switches constituting the switch circuit and the inverter circuit are connected to the control output terminal of the control unit.

Replacement paper (Kaikai 26) A power supply and a voltage signal or a current signal on the output side of the AC filter are connected to a signal detection input terminal of the control section to constitute a backup power supply, and the output of the AC filter (the output of the backup power supply) is formed. ) Is connected to the output terminal through a two-way switch, and the main power supply is connected from the input terminal to the output terminal through the two-way switch. The parallel operation device of the three inventions.

5. As a fifth invention, a capacitor charged by the main power supply is connected to an input side of an inverter circuit for converting DC to AC, and an output side of the inverter is connected to an input side of an AC filter. A control terminal of a switch constituting the inverter circuit is connected to a control output terminal of a control unit, and a main power supply and a voltage signal or a current signal on the output side of the AC filter are transmitted to the control unit by a signal of the control unit. A backup power supply is configured by connecting to the detection input terminal. The output of the AC filter (output of the backup power supply) is connected to the output terminal through a bidirectional switch, and the main power source is connected to the input terminal. The parallel operation device according to the first invention, the second invention, or the third invention, wherein the parallel operation device is connected to an output terminal through a directional switch.

6. According to a sixth aspect of the present invention, there is provided one or more capacitors that are charged by a main power supply, and a backup source that generates a voltage by the capacitors is connected to an output terminal through a bidirectional switch. The main power supply is connected from the input terminal to the output terminal through an overload protection device and a bidirectional switch, and an overvoltage protection device such as a surge absorber is connected between the output side of the overload protection device and the main power supply. A parallel operation device according to the first invention, the second invention, the third invention, the fourth invention, or the fifth invention, wherein the parallel operation devices are connected to each other.

Replacement form (Rule 26)