JPH1042567A - Frequency converter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To economically improve the reliability of a frequency conversion device. SOLUTION: A spare / inverting device having a function of forward power conversion from AC to DC of frequency I and a function of reverse power conversion from DC to AC of frequency II is provided as a spare device,
This spare device was connected via a selection switch so as to be operated as a forward conversion device and also as an inverse conversion device, thereby constituting a frequency conversion device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system configuration of a frequency converter having different frequencies of input and output AC power. More specifically, the present invention relates to a configuration of a highly reliable frequency conversion device including a spare conversion device.

[0002]

2. Description of the Related Art Two frequencies of 50 Hz and 60 Hz are used in a commercial power system in Japan, and two types of load equipment are provided corresponding to these frequencies. For this reason,
There is a case where power of one frequency is converted into another frequency and used. Often, a 400 Hz power supply used for ships is converted to 50 or 60 Hz AC power for use in general-purpose equipment. 400 Hz power used for large computers and aircraft related equipment is also obtained by converting commercial power. When high reliability is expected for these frequency converters, a method is provided in which a spare converter is provided, and when the operating converter breaks down, it is switched to the spare device and used.

[0003] Hereinafter, a conventional high-reliability frequency converter will be described. First, a single frequency converter having no spare device will be described. FIG. 5 shows the configuration of the frequency conversion device. The converter A is placed in the AC input section of the frequency converter. The converter A is a forward converter that receives, for example, 50 Hz commercial AC power and converts the AC power into DC power, and has a function as a so-called rectifier. An inexpensive thyristor rectifier circuit may be used for simple power conversion from AC to DC, but in this example, a high-performance bridge circuit is used to increase the input power factor until it approaches 1, and to reduce harmonic components in the input current. It has a function to control so that it is not included. This eliminates the injection of harmonic current into the commercial power system and prevents harmonic pollution. The converter B is placed at the AC output part of the frequency converter. The converter B has a function as a so-called inverter that converts DC power into a constant frequency AC voltage having a desired frequency, for example, 400 Hz. The battery BT is placed in the DC section. 400Hz for load
AC power is supplied. Although the frequency converter is an example of a three-phase device, the connection outside the frequency converter is simplified and shown in a single-line diagram. Normally, the frequency converter receives electric power from the AC power supply 1 of 50 Hz, converts the electric power into DC with the converter A, charges the battery BT, and supplies power to the converter B. The converter B outputs AC power with a constant frequency and a constant voltage of 400 Hz. At the time of the power failure of the AC power supply 1, the discharge power of the battery BT is supplied to the converter B, and the power is continuously supplied to the load from the frequency converter without a power failure. The two sets of converters A and B incorporated in the frequency converter may have the same configuration. Change the constant of the AC filter as needed. The control device is different for converter A and converter B. The control device A of the AC input unit shapes the waveform of the AC current into a sine wave shape, generates a signal for setting the input power factor to 1 and also keeps the output DC voltage of the converter A constant, and sends the signal to the converter A. . On the other hand, the control device B of the output section generates a signal for controlling the voltage and frequency of the output of the frequency conversion device and sends the signal to the converter B.

In the example of FIG. 5 using a single frequency converter, if a failure occurs in a part of the frequency converter, power supply to a load is stopped. When higher reliability is required for the frequency converter, a redundant parallel operation system using two frequency converters is configured. FIG. 6 shows the configuration of the redundant parallel operation system. One of the two frequency converters a and b
The stand is spare. For example, even if one of the frequency converters is disconnected due to a failure, the power required by the load can be supplied by the remaining frequency converters. While power is being supplied to the load,
Another advantage is that maintenance and inspection can be performed by separating the frequency converters. The input / output of the frequency converter is performed by opening and closing the switches Sa1 and Sa2 on the input side, and by opening and closing the switches Sb1 and Sb2 on the output side. The switch may be a mechanical switch such as an electromagnetic switch or a semiconductor switch such as a thyristor. Also, switch S
a1, 2 and Sb1 and 2 may be mounted inside the frequency converter. The numbers shown in parentheses indicate the relative magnitude of the power capacity. If the power consumption of the load is 100,
The rated output capacity of each frequency converter is 100. Each of the forward conversion unit and the inverse conversion unit constituting each frequency conversion device also has 100 power conversion capacities. There are a total of 200 power conversion facilities. Since the redundant operation frequency conversion system has two frequency conversion devices a and b, the total power conversion capacity is 100 × 4, which is four times the load demand.

FIG. 7 shows a configuration example of a power supply system in which the loads are divided into two systems and power is supplied from different power sources in order to improve reliability. Examples of such loads are found in the case of highly reliable computer systems that are forced to operate nonstop. In order to enhance the reliability, the computer system is composed of exactly the same two sets of the system 0 and the system 1, and the same computer processing is performed. Even if one of them stops due to failure or inspection, the other is operated continuously. In these highly reliable computer systems, two power supply systems are provided so that computer work can be continued even when a part of power supply is stopped, and power is separately supplied to the 0 system and 1 system computers. FIG. 7 shows an example of a power supply system for supplying power to these two loads 0 and 1 using two redundant parallel operation systems of the frequency converter of FIG. 1
Assuming that the power consumption of one load is 100, the output power capacity of each of the frequency converters a to d to supply power may be 100. Since the converters A and B require 100 power conversion capacities inside the frequency converter, one frequency converter performs a total of 200 (100 + 100) power conversion processes. As a 400 Hz power supply system, a total of 800 (100 × 8) power is converted for a total of 200 required by the loads 0 and 1.

[0006]

When power is supplied by one frequency converter, a power supply system can be constructed at low equipment cost. However, if the frequency converter breaks down, the power supply stops, and the reliability of the power supply is not high. On the other hand, when performing redundant parallel operation using a plurality of frequency converters,
Although the reliability of the power supply system is increased, a spare device needs to be provided, and the cost of the equipment is greatly increased. If there are multiple loads, this high cost becomes a serious problem. It is required to build a highly reliable frequency conversion system while suppressing an increase in cost.

[0007] If any of the frequency converters operating in redundant parallel operation fails, the faulty device must be disconnected from the parallel operation system for repair and inspection. Therefore, until the repair and inspection of the failed device are completed, the sound circuit mounted in the failed device is not utilized and is asleep (for example, if the converter A fails, the converter B becomes healthy). But is disconnected from the power supply system). Similarly, the battery of the frequency converter that has been separated is sleeping without being able to provide a power supply service even when a commercial power supply fails. We want to use sound parts as much as possible to improve the reliability of the power supply system.

[0008]

According to the present invention, there is provided an apparatus for receiving power from an AC power supply having a frequency I, converting the power into AC power having a frequency II, and outputting the AC power. And three or more converters each including a bridge circuit using a semiconductor switch and a filter. At least one of the converters is a forward converter for converting the frequency I from alternating current to direct current. At least one converter is a reverse converter for converting DC to AC of frequency II. At least one of the converters is a converter for converting AC to DC of frequency I and DC to frequency. II is a forward / inverse converter selectively operated to perform either of the inverse conversion into alternating current, and the AC terminal of the forward conversion device has a frequency I
The AC terminal of the inverter is connected to a load via a selection switch, and the AC terminal of the inverter is connected to the AC power source of the frequency I or the load via a selection switch. The gist of the present invention is a frequency converter characterized in that the DC terminals of the converters are commonly connected.

The converter A and the converter B constituting the frequency converter are separated and made independent. This reduces the number of structural units per device, and therefore reduces the number of failed parts. As a result, the probability of device failure is reduced. That is, the reliability is improved. The failure of the converter A does not affect the converter B, and the converter B
However, if a failure occurs, the connection is made so as not to affect the converter A. Thus, even if a failure occurs, only the failed device needs to be disconnected, and all the remaining converters can be provided for the power supply service. In order to improve the workability of repairs and inspections, when a failure occurs, only the failed converter can be separated and repaired. If a failure occurs in the forward converter, switch the spare forward / reverse converter to the AC power supply side and use it . In addition, when the inverter on the output side fails, power can be supplied to the load from the backup inverter, so the reliability of power supply to the load is improved, and at the same time, the workability to repair and inspect only the failed converter can be separated. Improvement can be expected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A forward / inverting device having both a function of a forward conversion for converting an alternating current having a frequency I into a direct current and a function of performing a reverse conversion from a direct current to an alternating current having a frequency II is provided as a spare device.
It is characterized in that it is connected via a selection switch so that it can be operated for both forward conversion and reverse conversion, and that the reliability of the frequency conversion device is increased at a lower cost than in the conventional example.

[0011]

Embodiment 1 FIG. 1 shows a first embodiment of the present invention and shows an example in which 50 Hz power is converted to 400 Hz power. Reference numeral 1 denotes an AC power supply, and a commercial power supply of, for example, 50 Hz is generally used. In the case where an engine / generator is provided as a standby power source, the engine / generator is used as an AC power source when a commercial power source fails. Reference numeral 2 denotes a forward converter, and 3 denotes an inverse converter having an output frequency of 400 Hz. 4
Is a forward / inverse conversion device. 5 is a load. 6 is a battery. Forward conversion device 2 is connected to AC power supply 1.
The inverter 3 is connected to the load 5 via the selection switch SB1. The forward / inverse conversion device 4 is connected to the AC power supply 1 of 50 Hz via the selection switch SA1 and to the selection switch S
It is connected to a load 5 requiring 400 Hz via A2 and SB2. Although two selection switches SA2 and SB2 are provided to facilitate maintenance and inspection, only one of them may be provided. The DC side of each converter 2, 3, 4 is a battery 6
It is connected to the. In the case where it is not necessary to supply power to the load during the power failure of the AC power supply, the battery 6 may not be provided.

Next, the operation of the embodiment of FIG. 1 will be described. (Continuous operation mode) This is an operation mode in which the forward conversion device 2 and the inverse conversion device 3 are in the operating state. Selection switches SB1, S
A2 is closed, and SA1 and SB2 are open. The forward converter 2 converts the AC power of the AC power supply 1 into DC power and supplies power to the inverse converter 3 and charges the battery 6. The inverter 3 supplies an AC voltage of 400 Hz to the load 5. The forward-inverse conversion device 4 is in the reverse conversion mode, ie, 400H in preparation for the failure of the inverse conversion device 3.
Standby operation as z output inverter.

(Operation mode at the time of power failure) This is an operation mode in which the AC power supply 1 is powered down and power is supplied with the discharge power of the battery 6.
When the AC power supply 1 loses power, the forward conversion device 2 stops, and the reverse conversion device 3 converts DC power resulting from the discharge of the battery 6 into AC power and feeds it to the load 5. The forward / inverse converter 4 is 400H
Standby operation at z.

(Operation Mode at the Time of Failure of Inverter) This is an operation mode when the inverter 3 supplying power to the load 5 fails. When the inverter 3 fails, the selection switch SB1
And close SB2, until the output frequency is 400Hz
Is supplied to the load 5 from the forward / inverting converter 4 which has been in standby operation. Selector switch SB by repairing and recovering inverter 3
When SB2 is opened and SB1 is closed, the operation mode returns to the normal operation mode.

(Operation mode at the time of failure of the forward converter) This is an operation mode when the forward converter 2 receiving power from the AC power supply 1 fails. When a failure occurs, the inverter 3 converts the power of the battery 6 and feeds the power to the load 5. Select switch SA2
Is opened, and the forward / inverse conversion device 4 that has been in standby operation at 400 Hz as an inverse conversion device is operated as a forward conversion device with an input frequency of 50 Hz, and the selection switch SA1 is closed.
As a result, power is supplied from the AC power supply 1 and the battery 6
To stop discharging. When a battery is not provided, the capacity of the DC capacitor C _DC can be increased, and switching can be performed within a period covered by this discharge.
The failed forward conversion device 2 is restarted after repair and inspection, the selection switch SA1 is opened, the forward / reverse conversion device 4 performs a reverse conversion operation, and is input to SA2. This returns to the normal operation state.

(Large-capacity battery charging mode) In order to operate the load even in the case of a long-term power failure of the AC power supply 1, the storage capacity of the battery 6 is increased. If the battery 6 is large, the amount of electric power to be charged is large. Therefore, the capacity is insufficient with only the forward conversion device 2 in which the required capacity is determined to be 100 in consideration of the capacity (tentatively, 100) of the inverse conversion device 3. In the present invention, during the charging time of the battery 6, the forward / reverse converter 4 is operated in parallel with the forward converter 2 to increase the forward conversion power to 100 × 2 to charge the large capacity battery 6.

The relationship between the load power demand and the power conversion capacity of the converter will be described below. The numbers in parentheses in FIG. 1 are relative power capacities. Assuming that the demand power of the load is 100, the total power conversion amount of the three converters is 100 × 3. In FIG. 6 of a conventional highly reliable frequency converter corresponding to this, the total power conversion amount is 100 × 4, and in the present invention, equal or higher reliability is obtained with a smaller amount of equipment. The economic effect is clear.

A description will be given of a conversion device which is a component of the present invention. FIG. 2 shows the configuration of the conversion device. Q1 to Q6 are semiconductor switch elements, for example, bipolar transistors.
D1 to D6 are diodes. Semiconductor switch element Q
A three-phase bridge inverter circuit is configured by using six sets of semiconductor switches each configured by an anti-parallel circuit including a diode D and an antiparallel circuit. Reactor L from bridge AC point AU, AV, AW
1 to L3 and connected to an AC terminal via a filter composed of capacitors C1 to C3. When this converter is connected to an AC power supply, it becomes a forward converter, and the AC terminal of the device becomes an input terminal. When connected to a load, it becomes an inverting device, and the AC terminal becomes an output terminal. DC point P of the bridge,
N is output to the DC terminal. An electrolytic capacitor C _DC is provided across the DC point of the bridge. The control device is a device for generating a signal for controlling the operation of the semiconductor switch elements Q1 to Q6 constituting the converter, and has at least one of the control devices A and B in FIG. The control device A is used to generate a signal when the conversion device is used as a forward conversion device for converting AC to DC, and the control is used for generating a signal when used as an inverse conversion device for converting DC to AC. Use device B. The functions of the control devices A and B are incorporated in the forward / inverse conversion device, and the functions of the control devices A and B are selected and used in the forward / inverse conversion device. When used as a forward conversion device, the control device A uses an AC input current and an output DC voltage as sensing information. The phase of the input current is adjusted to the phase of the AC power supply voltage, that is, the input power factor is set to 1
, And at the same time, the waveform of the input current is shaped into a sine wave to suppress the generation of harmonic current. Also, the level of the AC input current is controlled so that the level of the DC voltage becomes a desired value. A signal having these pieces of control information is generated so that each semiconductor switch element Q
1 to Q6. (For example, Japanese Patent Application Laid-Open No. 7-59354)
The control device B, when used as an inverting device, uses an AC output voltage as sensing information. Control is performed so that the frequency of the output voltage becomes a desired value and the voltage level becomes a desired value. In some cases, the voltage waveform is shaped so as to have a sine wave shape. A signal having such control information is generated and given to the semiconductor switching elements Q1 to Q6.

In FIG. 2, the control device A or B is mounted inside the conversion device, but the control devices of each conversion device may be mounted together as an independent device. This facilitates the exchange of signals between the control devices when a plurality of converters are operated in synchronization and in parallel.

In FIG. 1, the selection switches SA1, SB2 and SB1, provided on the AC side of the converter may be respectively mounted inside the converter of FIG. Further, not only mechanical switches such as electromagnetic switches but also semiconductor switches as conventionally used can be applied to the selection switches SA1, SB2, SB1 and SB2. FIG. 3 shows a configuration example of one phase of a selection switch using a thyristor as a semiconductor element. A signal is supplied to a thyristor pair to which a current is desired to flow to turn it on. The signal turns off when the signal is stopped. In the case of a three-phase selection switch, this switch is provided for each of the U, V, and W phases.

The electrolytic capacitor C _DC may be moved to the DC bus side as shown in FIG. FIG. 2 shows an example in which a bipolar transistor is used as a semiconductor switch element, but a GTO (gate turn-off thyristor), an IGBT, or the like is also used. As a circuit example of the converter, a three-phase bridge circuit that has been used conventionally is shown.
Other single-phase conventional circuits are used in the same manner.

The output capacity of each inverter may be determined according to the demand of the load. For a large load, two or more inverters can be operated in parallel. The parallel operation is conventionally used as shown in FIG. 6 and is technically established. Similarly, the forward conversion device and the forward / reverse conversion device can be easily operated in parallel by operating a plurality of devices using the conventional technology. In the present invention, the case of parallel operation is equivalently treated as one unit.

The three converters of this embodiment are functionally independent devices. They may be mounted in independent frames, or may be mounted in one frame, for example, by partitioning the inside into three.

Embodiment 2 FIG. 4 shows a second embodiment of the present invention. The first embodiment of FIG. 1 is an example in which power is supplied to a single load 5 (including a case where a plurality of loads are connected in parallel). The embodiment shown in FIG. 4 is a case where power is supplied to a plurality of loads (FIG. 4 shows the case of two sets of loads). Forward conversion devices 21 and 22 are each connected to AC power supply 1. The inverter 31 is connected to the load 51 via the selection switch SB11. The inverter 32 is connected to the load 52 via the selection switch SB21. The forward / inverse converter 4 is connected to the AC power supply 1 via the selection switch SA1, and to the selection switches SA2 and SB12.
Is connected to the load 51 via the selection switches SA2 and SB22. The DC terminal of each converter is connected to batteries 61 and 62 via switches SBT1 and SBT2, respectively.

Next, the operation of the embodiment of FIG. 4 will be described. (Constant operation mode) This is an operation mode in which all the converters are operating. Selection switches SA1, SB12, SB
22 is open and SA2, SB11 and SB21 are closed. Further, the switches SBT1 and SBT2 are closed.
The forward converters 21 and 22 convert the AC power of the AC power supply 1 into DC power and supply power to the reverse converters 31 and 32 and charge the batteries 61 and 62. The inverter 31 converts DC power into AC power and feeds it to the load 51. The inverter 32 also supplies power to the load 52 in the same manner. The forward / inverse conversion device 4 closes the selection switch SA2 and
Standby operation is performed in the 0 Hz reverse conversion operation mode.

(Operation Mode at Power Failure) This is an operation mode in which the AC power supply 1 loses power and supplies power with the discharge power of the batteries 61 and 62. When the AC power supply 1 loses power, the forward conversion devices 21 and 22
Are stopped, and the inverters 31, 32 are connected to the batteries 61, 62.
Is converted into AC power by the discharging of the power supply and supplied to the respective loads 51 and 52. The forward / inverse converter 4 is 400H
Standby operation at z.

(Operation mode at the time of failure of the inverter) Load 5
1 of the inverters 31 and 32 supplying power to the
This is the operation mode when the table breaks down. When the reverse conversion device, for example, 31 fails, the selection switch SB11 is opened and the SB12 is closed, and the load 51 is supplied from the forward / reverse conversion device 4 that has been in standby operation until then. The inverter 31 is restored for repair, the selection switch SB12 is opened, SB11 is closed, and the operation mode returns to the normal operation mode again.

(Front Converter Failure Mode) This is an operation mode when one of the forward converters 21 and 22 receiving power from the AC power supply 1 fails. Forward converters 21 and
2, for example, if 21 fails, the selection switch S
A2 is opened to change the operation mode of the forward / inverse conversion device to forward conversion, and then the selection switch SA1 is closed, and the forward / inverse conversion device 4 that has been in standby operation in the reverse conversion mode until now is operated as a forward conversion device. Although only the forward conversion device 22 is operated for a short period before the forward / inverse conversion device 4 starts operating, the power received from the AC power supply 1 is insufficient.
This shortage is covered by the discharge of the batteries 61 and 62, and does not hinder the power supply to the load. The failed rectifier 21 is restarted after repair and inspection, and the selection switch S
A1 is opened, the forward / backward conversion device 4 is switched to the reverse conversion operation, the selection switch SA2 is closed, and this is operated at 400 Hz with no load to return to the normal operation mode.

(Charge Mode of Large Capacity Battery) In order to operate the load even in the case of a long-time power failure of the AC power supply 1, the storage capacity of the batteries 61 and 62 is increased. If the batteries 61 and 62 are large, the amount of electric power to be charged is large, so that only the forward converters 21 and 22 whose capacities are determined according to the capacities of the inverters 31 and 32 will be insufficient in capacity. In the present invention, during the charging time of the batteries 61 and 62, the forward / reverse converter 4 is opened with the selection switch SA2 closed, and SA1 is closed to operate in parallel with the forward converters 21 and 22 to increase the amount of forward conversion power to increase the battery 61, 62. Charge 62.

It is necessary to periodically conduct a capacity test on the battery to check whether the storage capacity is normal. In addition, since the life is short, it is necessary to replace it with a new one usually in about five years. At the time of these operations, the treatment may be performed by partially and alternately disconnecting the switches by the switches SBT1 and SBT2 of the batteries 61 and 62, and the workability is good. In addition, since the work is performed while the remaining battery is provided for the service, even if the AC power supply 1 fails, the power supply service is continued because a part of the battery is always connected. In addition, the first of FIG.
In this embodiment, it is needless to say that the same effect can be obtained by dividing the battery and providing switches as shown in the example of FIG.

In the embodiment of FIGS. 1 and 4, an example has been described in which one spare forward / inverting device 4 is provided. However, by providing a plurality of spare devices, the reliability as a frequency converting device is further improved. I do.

Comparing the economic effects, in the case of the configuration shown in FIG. 4, the total power conversion capacity of the converter is 500 (100 × 5) for supplying power to two loads 100 × 2. On the other hand, the total power conversion capacity of the conventional example shown in FIG.
0 (100 × 8), and the effect of the present invention on economy is high.

In the embodiment, the load is described as having two systems. However, the same effect can be obtained by extending the system to three or more systems. For example, when a highly reliable power supply system is constructed in a five-story building, if the load system is divided for each floor and installed as a frequency converter having five inverters, the reliability can be improved. At the same time, the economy is enhanced.

[0034]

【The invention's effect】

The input-side rectifier and the output-side inverter constituting the conventional frequency converter are separated into two independent devices. This reduces the size of the device per unit and improves reliability due to the reduced number of components. When the power supply system is configured, the same or higher reliability can be secured by using a device having a smaller total power capacity than the conventional power supply system. Therefore, the equipment of the power supply system of the present invention is superior in terms of economy. For example, in the first embodiment of FIG. 1, the total power conversion capacity on the converter side is 300 with respect to the power demand 100 of the load. On the other hand, 400 is required in the conventional example shown in FIG. 6, and it can be said that the present invention having equal or higher reliability can be economically realized. Similarly, when power is supplied to two systems of loads, the conventional example (FIG. 7) requires 800 whereas the second embodiment of FIG. 4 of the present invention requires only 500, and the economic effect is clear. If the load has a dual configuration of a 0-system and a 1-system as in a highly reliable computer, it can be said that the effect is extremely large if the present invention is applied. In the case of increasing reliability by branching a load system, the economic effect of the present invention increases as the number of branches increases. When a high-reliability power supply system is built in a high-rise building, applying the present invention and dividing the power supply in accordance with the load of each floor of the building to provide a large effect is significant. -Functional parts of the forward conversion device, the inverse conversion device, and the forward / inverse conversion device are realized with the same configuration. This made it possible to share parts. As a result, standardization of the conversion device is promoted, which contributes to cost reduction. -If any of the converters fails, it is only necessary to disconnect and repair and inspect only that device, and all other healthy converters can be provided for service, so that the operation rate of the device is high. -Since the parts are standardized, the number of types of parts to be prepared for failure repair, periodic replacement, etc. may be small, and the workability of maintenance is also good.・ Regular battery inspection, capacity test (deterioration judgment test)
Can be partly separated and work can be performed while part of the power supply system is in operation, so that the workability can be improved without lowering the reliability of the power supply system. And the like.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention.

FIG. 2 shows a configuration example of a conversion device used in the present invention.

FIG. 3 shows a configuration example of a selection switch used in the present invention.

FIG. 4 shows a second embodiment of the present invention.

FIG. 5 shows a conventional example of a frequency converter used alone.

FIG. 6 shows a conventional example of a frequency converter in which a plurality of frequency converters are operated in redundant parallel operation.

7 illustrates an example of a conventional frequency converter that supplies power to two independent loads using the frequency converter of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Forward converter 21 Forward converter 22 Forward converter 3 Inverter 31 Inverter 32 Inverter 4 Forward / inverter 5 Load 51 Load 52 Load 6 Battery 61 Battery 62 Battery SA1 selection switch SA2 selection switch SB1 Selection switch SB2 Selection switch SB11 Selection switch SB22 Selection switch SBT1 Switch SBT2 Switch Q1 Semiconductor switch element Q2 Semiconductor switch element Q3 Semiconductor switch element Q4 Semiconductor switch element Q5 Semiconductor switch element Q6 Semiconductor switch element D1 Diode D2 Diode D3 Diode D5 Diode D5 diode L1 reactor L2 reactor L3 reactor C1 capacitor C2 capacitor C3 capacitor C _DC electrolytic capacitor Support

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H02M 7/797 8110-5H H02M 7/797

Claims (1)

[Claims] 1. An apparatus for receiving power from an AC power supply having a frequency I, converting the power into AC power having a frequency II, and outputting the AC power. The conversion apparatus includes a bridge circuit using a semiconductor switch and a filter. It has three or more, at least one of which is a forward converter from frequency AC to direct current, and at least one of them is a DC to frequency II AC converter. At least one of the converters operates by selecting either the forward conversion of frequency I from AC to DC or the reverse conversion from DC to frequency II of AC. And an AC terminal of the forward conversion device having a frequency I
The AC terminal of the inverter is connected to a load via a selection switch, and the AC terminal of the inverter is connected to the AC power source of the frequency I or the load via a selection switch. A frequency converter, wherein the DC terminals of the converters are connected in common.