JP2761538B2 - Uninterruptible power system - Google Patents

Description

The present invention relates to an uninterruptible power supply for supplying uninterruptible AC power to a communication device or a computer, and in particular, operates an inverter also as a charger, Small and lightweight equipment,
The present invention relates to an economical uninterruptible power supply.

2. Description of the Related Art Conventionally, as an uninterruptible power supply of this type, a system shown in FIG. 1 has been proposed (Japanese Patent Publication No. 49-41734). In this figure, an AC power source such as a commercial power source is connected to a load 7 via a switch 2, an inverter 5 is connected to a rechargeable storage battery 4, and the inverter 5 is connected to the load via the switch 3, 3 is connected in parallel with a reactance circuit 6. The switch 2 is turned on when the AC power supply 1 is normal, and is turned off when the power failure occurs, and the switch 3 operates in the opposite direction to the switch 2. That is, the switch 3 is turned off when the AC power supply 1 is normal, and turned on when the power failure occurs. The reactance circuit 6 mainly includes a reactor, a capacitor, or a reactor and a capacitor.

In this circuit, when the AC power supply 1 is normal, the switch 2 is on, and the AC power is directly sent to the load 7. On the other hand, the inverter 5 receives the power of the storage battery 4 and outputs an AC voltage synchronized with the voltage of the AC power supply 1, and its output side is connected to the AC power supply 1 via the reactance circuit 6. At this time, the switch 3 is off. Here, by delaying the phase of the output of the inverter 5 from the AC power supply 1, power flows from the AC power supply 1 to the inverter 5, and the inverter 5 operates as a charger and charges the storage battery 4.

When the AC power supply 1 fails, the switch 2 is turned off and the switch 3 is turned on, thereby supplying the AC output of the inverter 5 to the load 7.

Generally, when the output sides of two AC power supplies are connected and a voltage difference or a phase difference is given between them, a current flows from one power supply to the other power supply according to the difference. That is, a cross flow occurs.

In this conventional example, since the AC power supply 1 and the output side of the inverter 5 are always connected, the reactance circuit 6 is indispensable to suppress a cross current flowing due to a phase difference or a voltage difference between the two power supplies. Reactors and capacitors used in the reactance circuit 6 need to be designed to operate at a commercial frequency, and are large in size and weight. In addition, in the event of a commercial power failure, a switch 3 for short-circuiting the rear stance circuit 6 is required to supply power from the inverter 5 to the load 7. Thus, in the conventional uninterruptible power supply,
There have been problems that the size and weight of the device are increased, and that economic efficiency is impaired.

An object of the present invention is to provide a compact, lightweight, and economical uninterruptible power supply that solves these problems.

According to the present invention, an AC power supply is connected to a load via a switch, and a storage battery is connected to a load via an inverter circuit. The inverter circuit includes a DC filter unit and a high-frequency inverter. , A high-frequency transformer, a frequency conversion unit, an AC filter unit, and a control circuit unit. The control circuit unit controls the inverter circuit in a charger mode or an inverter mode. AC power is converted to high-frequency AC, insulated by a high-frequency transformer, and converted to DC by a high-frequency inverter. In the inverter mode, the DC power of the storage battery is converted to high-frequency AC by a high-frequency inverter, and isolated by a high-frequency transformer. The frequency converter converts the frequency to supply power to the load, and the power failure detection circuit determines whether AC power is present. Detect
A switch is controlled and a signal for switching between the two operation modes is given to the control circuit unit.

In the charger mode, the frequency converter includes:
After the voltage of the AC power supply is generated in the high-frequency transformer in the positive direction, an operation of returning the exciting current of the high-frequency transformer is performed.After the voltage of the AC power supply is generated in the high-frequency transformer in the negative direction, the high-frequency When the voltage of the AC power supply is converted into a high-frequency AC voltage by repeating the operation of returning the exciting current of the transformer, and after storing energy in the reactor of the AC filter of the frequency conversion unit, the voltage of the AC power supply is reduced. An operation of applying a voltage obtained by superimposing a voltage of the reactor of the AC filter to the high-frequency transformer, and storing energy in the reactor of the AC filter, and then superimposing a voltage of the reactor of the AC filter on a voltage of the AC power supply. The operation of applying the applied voltage to the high-frequency transformer with a polarity opposite to the applied voltage of the high-frequency transformer is repeated. This may convert the voltage of the AC power supply into a high-frequency AC voltage.

FIG. 2 shows an embodiment of the present invention. 2, the inverter 50 includes a DC filter 51, a high frequency inverter 52, a high frequency transformer 53, a frequency converter 54, an AC filter 55, and a control circuit 56. The power failure detection circuit 8 detects a power failure of the AC power supply 1. The same numbers as those in FIG. 1 indicate the same items.

Next, the operation of the present invention will be described. When the AC power supply 1 is normal, the switch 2 is turned on to supply power to the load 7. The inverter 50 operates as a charger with the AC power supply 1 as an input through the switch 2. That is, the AC power passes through the AC filter 55 and passes through the frequency converter.
It is input to 54 and converted to high frequency AC voltage. This high-frequency voltage is insulated by the high-frequency transformer 53, rectified by the inverter 52, and becomes a DC voltage. The ripple component included in the DC voltage is reduced by the DC filter 51 and charges the storage battery 4.

When the AC power supply 1 loses power, the power failure detection circuit 8 generates a signal, turns off the switch 2, and switches the operation mode of the control circuit 56 to the inverter mode. In the inverter mode, the DC power of the storage battery 4 is input to the inverter unit 52 through the DC filter 51 and is converted into a high-frequency AC voltage. This high-frequency voltage is insulated by the high-frequency transformer 53 and is input to the frequency conversion unit 54. The frequency conversion unit 54 performs frequency conversion into a low-frequency AC voltage by repeating a sub-mode for passing the high-frequency voltage as it is and a sub-mode for switching in the positive or negative direction within a predetermined cycle in accordance with a separately generated pulse width modulation signal. The AC voltage is supplied to the load 7 after the harmonic component is removed by the AC filter 55.

Next, a specific example of the inverter 50 and the control circuit 56 will be described.
The operation in the charger mode and the inverter mode, and the operation at the time of mode switching will be described in detail.

FIG. 3 shows an example of a specific circuit of the inverter 50. In the high-frequency inverter 52, the semiconductor switches S ₁ and S ₂ are connected in series, the semiconductor switches S ₃ and S ₄ are connected in series,
These two series connections are connected in parallel to form a DC filter 51.
Connected to. A connection point between the semiconductor switches S ₁ and S _{2 and} a connection point between S ₃ and S ₄ are connected to one winding of the high-frequency transformer 53.
Diode D _{1 is connected in} antiparallel with semiconductor switches S _{1 to} S ₄ , respectively.
~D ₄ is continued. In the frequency conversion unit 54, the semiconductor switches S ₁₁ and S ₁₂ are connected in series, the semiconductor switches S ₁₃ and S ₁₄ are connected in series, these two series connections are connected in parallel, connected to the AC filter 55, Switch S ₁₁ , S
The connection point of _{12 and} the connection point of S ₁₃ and S ₁₄
Is connected to the other winding. Semiconductor switches S _{11 to} S
Reference numeral ₁₄ denotes a switch element which can be controlled in both directions as shown in FIG. 4, for example. FIG. 5 shows an example of a specific block configuration of the control circuit. Further, FIG. 6 shows an example of the driving waveforms and the main voltage waveforms (when the polarity of the AC power supply is positive) in the charger mode, and FIG.
FIG. 8 shows an example of a drive waveform of each semiconductor switch in the inverter mode, and FIG. 8 shows an example of a voltage waveform of a main part of the main circuit in the inverter mode.

The operation of the control circuit when the AC power supply is normal will be described with reference to FIG. 5. A signal corresponding to the AC power supply normal state of the power failure detection circuit 8 turns off the drive circuit 514 through the NOT circuit 512 and turns off the switch S. ₁ ~S ₄ is turned off. The signal of the power failure detection circuit 8 is input to the switching circuit 511,
11 is a flip-flop (FF) 504, 505 signal drive circuit
Switch the circuit so that it is output to 513. On the other hand, the reference oscillator 502 generates a signal synchronized with the AC power supply by the synchronizing circuit 501 and inputs the signal to the FF 505, and generates a signal with a phase shift by the phase shift circuit 503 and inputs the signal to the FF 504. The output signal of the FF504 is a signal phase is shifted from the signal of the FF505, these signals inputted to the drive circuit 513 through the switching circuit 511, the drive signal of the switch S ₁₁ to S ₁₄ (FIG. 6 S
₁₁ ~S ₁₄₎ to generate. In response to these drive signals, the frequency converter 54, as shown in FIG. 6, the cycle shown in the following by semiconductor switches S ₁₁ to S _14, and converts the AC voltage to a high frequency AC voltage V _1.

By turning on the switches S ₁₁ and S ₁₄ , a positive voltage is generated in the high-frequency transformer 53.

By turning on the switches S ₁₁ and S ₁₃ , the exciting current of the high-frequency transformer 53 is returned. No voltage is generated in the high-frequency transformer 53.

By turning on the switches S ₁₂ and S ₁₃ , a negative voltage of the high-frequency transformer 53 is generated.

By turning on the switches S ₁₂ and S ₁₄ , the exciting current of the high-frequency transformer 53 is returned. No voltage is generated in the high-frequency transformer 53.

Thus obtained high-frequency AC voltages V ₁ is rectified by the diode D ₁ to D ₄ of the high-frequency inverter unit 52 V _2, and the
It is smoothed by passing through the DC filter 51 and charges the storage battery 4.

Next, the operation when the AC power supply 1 is out of power will be described with reference to FIG. 5. The power outage detection signal of the power outage detection circuit 8 is transmitted through the NOT circuit 512 by the drive circuit 514 to the FFs 504 and 505.
, The on-signals of the switches S _{1 to} S ₄ are generated, and at the same time, the switching circuit 511 is operated so that the output signal of the switch determination logic circuit 510 is input to the drive circuit 513.

On the other hand, since the input signal of the synchronization circuit 501 disappears, the reference oscillator 502 oscillates at an independent frequency, and the phase shift circuit 503, FF
Signals are generated by 504 and 505 in the same manner as when the AC power supply is normal. These signals are different from when the AC power supply is normal.
Through the drive circuit 514, drive signals S _{1 to} S ₄ (FIG. 7 S ₁ to S ₄
S _4), and the drive switches S ₁ to S ₄ of the high-frequency inverter unit 52. The signal of the reference oscillator 502 is input to a PWM signal generation circuit 506, and a sine wave generation circuit 507 and a carrier triangular wave generation circuit 508 generate a sine wave and a carrier triangular wave synchronized with the reference oscillator 502, and compare them with a comparison amount 509. A PWM (pulse width modulation) signal is generated by the comparison. The PWM signal and the output of the sine wave generator 507 are input to the switch determination logic circuit 510, and a signal for determining the drive timing of each switch of the frequency converter 54 is generated. Since the PWM signal is a signal that takes “0” level or “1” level, for example,
When the signal is at the “0” level, regardless of the signal of the sine generator 507, a signal for determining the timing of the drive signal is output so as to be in a sub-mode for passing a high-frequency AC voltage.
When the M signal is at the “1” level and the polarity of the sine wave generator 507 is positive, the sub-mode rectifies in the positive direction when the polarity is positive, and the sub-mode rectifies in the negative direction when the polarity is negative. Output. These signals are input to the driving circuit 513 through the switching circuit 511, the drive signal S ₁₁ to S ₁₄ (7
Figure S ₁₁ to S ₁₄₎ it becomes.

Upon receiving the above signal groups S _{1 to} S ₄ and S _{11 to} S ₁₄ , the inverter 50
Then, the following operation as shown in FIG. 7 is performed. The high-frequency inverter unit 52 to generate a high frequency AC voltage V ₃ to the primary side of the transformer 53 to the following cycle.

By turning on the switch S ₁ and S _4, to generate a positive voltage to the high frequency transformer 53.

By turning on the switches S ₁ and S ₃ , the exciting current of the high-frequency transformer 53 is returned. No voltage is generated in the high-frequency transformer 53.

By turning on the switches S ₂ and S ₃ , a negative voltage is generated in the high-frequency transformer 53.

By turning on the switches S ₂ and S ₄ , the exciting current of the high-frequency transformer 53 is returned. No voltage is generated in the high-frequency transformer 53.

High frequency AC voltage V ₃ generated is input to the frequency converter 54 via the high-frequency transformer 53. The frequency converter 54 operates in three sub-modes: a sub-mode for passing the high-frequency AC voltage as it is, a sub-mode for synchronous rectification in the positive direction, and a sub-mode for synchronous rectification in the negative direction.

In the sub-mode for synchronous rectification is a high frequency AC voltage V ₃ in the positive direction, to operate the semiconductor switches of the frequency converter 54 as follows.

Since the output of the high-frequency inverter 52 is in the positive direction, the switches S ₁₁ and S ₁₄ are turned on to rectify in the positive direction.

Since the output of the high-frequency inverter unit 52 is zero voltage, the switch S _13, S ₁₄ or S _11, S ₁₂ are turned on, is refluxed output current.

Since the output of the high-frequency inverter 52 is in the negative direction, the switches S ₁₂ and S ₁₃ are turned on, and synchronous rectification is performed in the positive direction.

In the sub-mode in which the high-frequency AC voltage is passed as it is, since the output of the high-frequency inverter 52 is a positive or negative voltage, the switches S ₁₁ and S ₁₄ or S ₁₂ and S ₁₃ are turned on to pass the high-frequency AC voltage as it is. Let it.

Since the output of the high-frequency inverter unit 52 is zero voltage, the switch S _13, S ₁₄ or S _11, S ₁₂ are turned on, is refluxed output current.

Furthermore, in the sub-mode for synchronous rectification in the negative direction, since the output of the high-frequency inverter unit 52 is positive, it rectifies the negative direction by turning on the switch S _12, S _13.

Since the output of the high-frequency inverter unit 52 is zero voltage, turns on the switch S _13, S ₁₄ or S _11, S _12, is refluxed for output current.

Since the output of the high-frequency inverter unit 52 is a negative direction, by turning on the switch S _11, S _14, it rectifies the negative direction.

These three sub-modes, by repeating according to an output signal of the output and the sine wave generator 507 of PWM signal generating circuit 506, for example, as shown in FIG. 8, the circumferential force V ₃ of the high-frequency inverter unit 52 pulse width modulation The voltage waveform V ₄ becomes the sine wave AC voltage V ₅
Becomes By adjusting the output level of the sine wave generator 507, the output level of the inverter 50 can be adjusted.

Switching between the charger mode and the inverter mode is performed by the signal of the power failure detection circuit 8 as described above. That is, when the AC power supply 1 loses power, the power failure detection circuit 8 generates a signal in FIG.
The switch drive signals S _{1 to} S ₄ of the high-frequency inverter 52 are turned on and off, and the switches S _{11 to} S
The drive sequence of FIG. ₁₄ is switched from FIG. 6 to the sequence of FIG. This switching is completed within one cycle of the operating frequency of the high-frequency inverter unit 52 and the frequency conversion unit 54, as is clear from FIGS. 6 and 7, so that the output of the inverter 50 is almost equal to the power failure of the AC power supply 1. Simultaneously, power can be supplied to the load 7 without an instantaneous interruption.

Also, when the AC power supply 1 recovers, the power failure detection circuit 8 again generates a signal, and the synchronization circuit 501 controls the reference oscillator 502, and thus the output of the inverter 50, to synchronize with the AC power supply 1, and thereafter, The switch 2 in FIG. 2 is turned on, and the control signal of the inverter 50 is switched from the sequence of FIG. 7 to the sequence of FIG. At this time, the switching is completed within one cycle of the operating frequency of the frequency conversion unit 54. Therefore, power can be supplied to the load 7 without interruption, and the charging of the storage battery 4 can be started immediately, so that the charging time can be shortened.

FIG. 9 shows a second specific example of the control waveform of the inverter 50 of FIG. 3 in the charger mode. The control waveform of FIG. 9 is the same as the control waveform of the first specific example of FIG. 6, and only the switch element to be controlled is different. Therefore, the circuit shown in FIG. 5 can be applied as it is to the control circuit for outputting the waveform shown in FIG. 9, and the description of the configuration and operation of the control circuit for generating the control waveform shown in FIG. 9 is omitted. Next, FIG. 3 and FIG.
The operation of this specific example will be described with reference to the drawings. This specific example is characterized in that in the charger mode of the inverter 50, the inverter 50 operates in a step-up manner. That is,
The switch S ₁₁ and S ₁₂ are turned on simultaneously, storing energy in the reactor of AC filter (), then the switch
Off the S _12, by turning on the S _14, the voltage of the AC power supply 1 is superposed a voltage of the reactor of AC filter 55 is applied to the high-frequency transformer 53 (). Next, switch S
₁₁ turned off, by turning on the S _13, again, storing energy in the reactor of AC filter 55 (), further turns off the switch S _14, by turning on the S _12, before and reverse polarity voltage Is applied to the high frequency transformer 53 (). By repeating this operation, the voltage applied to the high frequency transformer 53, a high voltage from the AC voltage AC voltages V _1, and this voltage V ₁ was, by the diode D ₁ to D ₄ of the high-frequency inverter unit 52 The battery is rectified and becomes a DC voltage, and the storage battery is charged through the DC filter 51. The operation in the inverter mode is the same as that of the first specific example shown in FIGS. 7 and 8, and a description thereof will be omitted. Switching between the inverter mode and the charger mode is completed within one cycle of the operating frequency of the high-frequency inverter 52 and the high-frequency converter 54, as in the first specific example. . In this specific example, a voltage higher than the AC power supply 1
Since V ₁ and therefore a high DC voltage can be obtained, the battery can be charged even when the storage battery voltage is high, and the storage battery 4 can be charged efficiently.

As described above, in the uninterruptible power supply according to the present invention, the inverter 50 operates at a high frequency and switches between the inverter mode and the charger mode within one cycle of the operating frequency. Since no moving parts are used, the device can be reduced in size and weight. Further, since the input and output of the inverter 50 are insulated by the high-frequency transformer 53, the storage battery 4 can be grounded even on the electric line where one line of the AC power supply 1 is grounded. When used, the safety of the device can be extremely enhanced for human safety.

[Effects of the Invention] As described above, according to the present invention, an uninterruptible power supply is configured using an inverter operating at a high frequency and having an input and output insulated, and all components operating at a low frequency are used. Therefore, it is possible to provide a compact, weighing, and economical uninterruptible power supply that is safe in terms of human body safety, has no output interruption, and is safe.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a conventional uninterruptible power supply, FIG. 2 is a block diagram showing an embodiment of the uninterruptible power supply of the present invention,
FIG. 3 is a connection diagram showing a specific example of an inverter circuit, FIG. 4 is a diagram showing a specific example of a bidirectional switch, FIG. 5 is a block diagram showing a specific example of a control circuit, and FIG. FIG. 7 is a drive waveform of each semiconductor switch and a voltage waveform diagram of a main part of the inverter circuit in the charger mode of the inverter circuit. FIG. 7 is a drive waveform and main waveforms of each semiconductor switch in three sub-modes of the inverter circuit of FIG. FIG. 8 is a voltage waveform diagram of a main part of the inverter circuit of FIG. 3 in an inverter mode, and FIG. 9 is a second specific example of a drive waveform of each semiconductor switch in a charger mode. It is a voltage waveform diagram of a principal part.

Claims (3)

(57) [Claims] 1. A switch for connecting an AC power supply to a load, a storage battery, an inverter circuit having the storage battery as an input side, and an output terminal connected to the load side of the switch, and a power failure detection circuit, The inverter circuit includes a DC filter unit, a high-frequency inverter unit, a high-frequency transformer, a frequency conversion unit, an AC filter unit, and a control circuit unit. The control circuit unit controls the inverter circuit in a charger mode or an inverter mode. In the charger mode, the frequency converter converts the AC power of the AC power supply into high-frequency AC, insulates it with the high-frequency transformer, and converts it into DC with the high-frequency inverter. The DC power of the storage battery is converted into high-frequency AC by the high-frequency inverter, and is insulated by the high-frequency transformer. The frequency converter converts the frequency, and supplies power to the load. The power failure detection circuit detects the presence or absence of the AC power supply, controls the switch, and controls the signal for switching the two operation modes. An uninterruptible power supply characterized by being provided to a circuit section. 2. The uninterruptible power supply according to claim 1,
In the charger mode, the frequency converter generates a voltage of the AC power supply in the high-frequency transformer in a positive direction, and then recirculates an exciting current of the high-frequency transformer. An uninterruptible power supply device wherein the voltage of the AC power supply is converted into a high-frequency AC voltage by repeating the operation of returning the exciting current of the high-frequency transformer after the voltage is generated in the transformer in the negative direction. 3. The uninterruptible power supply according to claim 1,
In the charger mode, after storing energy in the reactor of the AC filter of the frequency conversion unit, an operation of applying to the high-frequency transformer a voltage obtained by superimposing the voltage of the reactor of the AC filter on the voltage of the AC power supply, After storing energy in the reactor of the AC filter, a voltage obtained by superimposing the voltage of the reactor of the AC filter on the voltage of the AC power supply is applied to the high frequency transformer with a polarity opposite to the applied voltage of the high frequency transformer. An uninterruptible power supply device that converts the voltage of the AC power supply to a high-frequency AC voltage by repeating the operation.