JP2014011820A - Ac/dc power conversion device, dc/ac power conversion device, and uninterruptible power supply device comprising both power conversion devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an uninterruptible power supply device having a wide input voltage range.SOLUTION: An AC/DC power conversion device comprises: a first power conversion unit 5 which is connected to one power line of an AC power supply 1, and is a single-phase full bridge inverter; a second power conversion unit 6 which is connected between an output of the first power conversion unit 5 and the other power line of the AC power supply 1, and operates by a drive signal of one pulse applied for each half period of the AC power supply 1 to convert AC to positive and negative DC; and a positive electrode side capacitor 7 and a negative electrode side capacitor 8 to which the second power conversion unit 6 supplies power. The first power conversion unit 5 transforms input current waveform from the AC power supply 1 so as to reduce a maximum current value of the input current waveform.

Description

  The present invention includes an AC / DC power converter that converts AC power from an AC power source into DC power, an orthogonal power converter that converts DC power from a DC power source into AC power, and both power converters, and an AC power source The present invention relates to an uninterruptible power supply apparatus that supplies AC power from a power source to a load and converts DC power stored in a power storage unit to AC power and supplies the AC power to a load when the voltage of the AC power source drops.

In the conventional uninterruptible power supply, when the AC power is healthy, the connected AC power is converted into DC power by the AC / DC power converter, and this DC power is converted into AC power by the orthogonal power converter and supplied to the load. . And if it detects a voltage fluctuation that the voltage of the AC power supply is lower than the set value, it is determined as a power failure, the voltage is boosted by the DC / DC converter from the power storage unit, and then the AC power is supplied to the load via the orthogonal power converter. (For example, refer to Patent Document 1).
As described above, in the conventional uninterruptible power supply, in order to generate, for example, a + 200V positive DC power supply and a -200V negative DC power supply by the AC / DC power converter, the transistor constituting the AC / DC power converter is DC200V. Is switched at about 20 kHz. In this way, switching a high voltage of 200 V at a high frequency of 20 kHz causes a great power loss in the transistor.
In order to prevent this, as a method of reducing the power loss of the AC / DC power converter, there is a high-efficiency AC / DC power converter in which a single-phase full-bridge inverter is added before the circuit of the conventional AC / DC power converter (for example, , See Patent Document 2).
Further, as a method for reducing the power loss of the orthogonal power conversion unit, there is a high-efficiency orthogonal power conversion device in which a single-phase full-bridge circuit is added after the conventional half-bridge inverter circuit (see, for example, Patent Document 3).

Japanese Patent No. 3829846 JP 2010-63326 A WO2008-102552

When the above-described high-efficiency AC / DC converter is applied to a conventional uninterruptible power supply, in the uninterruptible power supply, it is necessary to stabilize the AC output voltage, and for that purpose, the uninterruptible power supply is configured. It is necessary to keep the DC power supply of the orthogonal power converter, that is, the output voltage of the high efficiency AC / DC power converter constant.
Maintaining the DC power supply voltage of the single-phase full-bridge inverter that constitutes the high-efficiency AC / DC power converter while maintaining the output voltage of the high-efficiency AC / DC converter constant, that is, the power balance handled by the single-phase full-bridge inverter In order to make it zero, when the input voltage from the AC power source becomes high, it is necessary to adjust by widening one pulse width output from the transistor of the conventional converter circuit. However, this one-pulse width has a maximum width that is half the period of the AC input voltage, and the maximum usable voltage of the input voltage of the AC power supply is determined from the restrictions. For example, when + 140V and -140V are output as the output voltage of the high-efficiency AC / DC converter, the input voltage of the AC power supply is the maximum usable voltage of about AC125V, and in the case of an input voltage higher than that, a single-phase full bridge Since the voltage of the DC power supply of the inverter circuit cannot be maintained, the DC power supply of the single-phase full bridge inverter has a problem that it is necessary to provide a dedicated DC power supply.
Similarly, the high-efficiency orthogonal power converter also has a problem that it is necessary to provide a dedicated DC power supply in order to maintain the voltage of the DC power supply of the single-phase full-bridge inverter circuit.

  The present invention has been made in order to solve the above-described problems, and in an AC / DC power conversion apparatus or a quadrature power conversion apparatus to which a single-phase full-bridge inverter is added in order to achieve high efficiency, a single-phase full-bridge inverter is provided. Therefore, it is possible to obtain an AC / DC power converter, an orthogonal power converter, and an uninterruptible power supply equipped with both of these power converters that do not require a dedicated DC power source to maintain the voltage of the DC power source.

  The AC / DC power converter according to the present invention is connected to one power line of an AC power supply, and is a first power conversion unit that is a single-phase full-bridge inverter, the output of the first power conversion unit, and the other power line of the AC power supply. And a second power conversion unit that operates with one pulse of drive signal applied every half cycle of the AC power source and converts AC to positive and negative DC, and supplies power by the second power conversion unit The first power conversion unit deforms the input current waveform so as to reduce the maximum current value of the input current waveform from the AC power supply.

  According to the present invention, the output voltage is deformed so as to reduce the maximum current value of the input current waveform from the AC power supply, or the maximum voltage value of the output voltage waveform in the AC output of the device is reduced. Since the waveform is deformed, there is no need to provide a DC power source for maintaining the voltage of the capacitor of the single-phase full-bridge inverter, and the apparatus can be reduced in size and cost.

It is a circuit diagram which shows the whole structure of the uninterruptible power supply in Embodiment 1 of this invention. It is a block diagram which shows the structure of the 3rd power converter part of the uninterruptible power supply in Embodiment 1 of this invention. It is a wave form diagram which shows the operation | movement of the 1st, 2nd power conversion part of the uninterruptible power supply in Embodiment 1 of this invention. It is a wave form diagram which shows operation | movement of the 1st power conversion part of the uninterruptible power supply in Embodiment 1 of this invention. It is a wave form diagram which shows operation | movement of the 2nd power conversion part of the uninterruptible power supply in Embodiment 1 of this invention. It is a wave form diagram which shows operation | movement of the 1st power conversion part of the uninterruptible power supply in Embodiment 1 of this invention. It is a wave form diagram which shows the operation | movement of the 1st, 2nd power conversion part of the uninterruptible power supply in Embodiment 1 of this invention. It is a wave form diagram which shows the operation | movement of the 3rd power converter part of the uninterruptible power supply in Embodiment 1 of this invention. It is a circuit diagram which shows another structural example of the 2nd power conversion part of the uninterruptible power supply in Embodiment 1 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the overall configuration of the uninterruptible power supply according to Embodiment 1 of the present invention, FIG. 2 is a block diagram showing the configuration of the third power conversion unit in FIG. 1, and FIG. 4 is a waveform diagram showing the operation of the first power conversion unit, FIG. 4A is a waveform diagram showing the operation of the first power conversion unit, FIG. 5A is a positive voltage output, FIG. 4B is a negative voltage output, and FIG. FIG. 6A is a waveform diagram showing the operation of the second power converter, FIG. 6A is a waveform diagram showing the operation of the first power converter, FIG. 6B is a waveform diagram showing the operation of the first power converter, FIG. FIG. 7 is a waveform diagram showing the operation of the first and second power converters when AC135V is input, and FIG. 7A is a waveform of one-pulse operation of the second power converter. FIG. 8B is a current waveform of the first power converter, FIG. 8 is a waveform diagram showing the operation of the third power converter, and FIG. It is a circuit diagram showing another configuration example of the power conversion unit.

  In FIG. 1, an uninterruptible power supply 100 is connected to one power line 17 of an AC power supply 1 via a b contact 2b (normally closed contact) of a switching relay 2, and an inrush current in which a resistor 3a and a relay 3b are connected in parallel. The prevention unit 3, that is, the parallel connection body, the first reactor 4 connected to the subsequent stage of the inrush current prevention unit 3, and the AC power input through the inrush current prevention unit 3 and the first reactor 4 1 pulse of 1 pulse which is connected between the 1st power conversion part 5 which converts into electric power, the output of the 1st power conversion part 5, and the other power line 18 of AC power supply 1, and is added every half cycle of AC power supply 1 A second power converter 6 that operates with a drive signal and converts alternating current into positive and negative direct current; a positive-side capacitor 7 that is connected to a positive output of the second power converter 6 and is charged to a predetermined value (for example, 140 V); , Of the second power converter 3 Connected to the negative output capacitor 8 connected to the pole output and charged to a predetermined value (for example, −140 V), and connected to the positive electrode side capacitor 7 and the negative electrode side capacitor 8, the DC power is converted into AC power of a predetermined voltage (for example, AC 100 V) Connected between the third power conversion unit 9, the second reactor 10 connected to the subsequent stage of the third power conversion unit 9, and the output of the second reactor 10 and the other common line 18 of the AC power supply 1. And the output relay 12 having one end connected to the load 14 and connected to the subsequent stage of the second reactor 10.

The other common line 18 of the AC power supply 1 is connected to the other end of the load 14.
The “AC / DC power converter” described in the claims includes the first power converter 5, the second power converter 6, the positive capacitor 7, and the negative capacitor 8 described above. Composed.

  The uninterruptible power supply 100 also includes a bypass relay 13 that short-circuits or opens the input-side end of the first reactor 4 and the output-side end of the second reactor 10, and a positive end that is a contact (a normally open circuit) of the switching relay 2. The power storage unit 15 connected to the contact) side and having the negative electrode end connected to the common line 18 and the fourth power conversion unit 16 that supplies the power of the power storage unit 15 to the negative capacitor 8 are also included.

  Here, the first power conversion unit 5 is a first DC power supply unit that holds the DC voltage and connects the four switching elements 5Q1 to 5Q4 in which the diodes 5D1 to 5D4 are connected in antiparallel with each other in a full bridge connection. 1 DC capacitor 5C is provided.

  The second power conversion unit 6 outputs a DC voltage having a voltage Vout (≈2 Vp) that is approximately twice the maximum voltage Vp of the AC power supply 1, and connects the diodes 6Da and 6Db in antiparallel. The pair of upper and lower switching elements 6Qa and 6Qb are connected in series with each other, and a pair of smoothing upper and lower positive electrode side and negative electrode side capacitors 7 and 8 connected in series to each other is a series circuit of these switching elements 6Qa and 6Qb. Are connected in parallel. The power line 20 that is the connection point of the switching elements 5Q1 and 5Q2 is connected to the connection point of both switching elements 6Qa and 6Qb, and the other power line 18 of the AC power supply 1 is connected to the connection point of the positive side capacitor 7 and the negative side capacitor 8 respectively. Has been. Further, the second power converter 6 includes a first bidirectional switch 6SW formed by connecting a pair of switching elements 6Qc, each having a diode 6Dc connected in antiparallel, in series with opposite polarities, and the two switching elements 6Qa, It is connected between the connection point of 6Qb and the connection point of the positive electrode side capacitor 7 and the negative electrode side capacitor 8.

Next, the structure of the 3rd power converter 9 which converts direct-current power into alternating current power is demonstrated.
In FIG. 2, the third power converter 9 is connected to the positive-side capacitor 7 and the negative-side capacitor 8 and operates with a one-pulse drive signal to convert direct current into alternating current, A second inverter 92 composed of a single-phase full-bridge circuit operating at a high frequency, and a second DC capacitor 9C serving as a DC power source for the second inverter 92. It is configured.
The “orthogonal power conversion device” and the “second capacitor” described in the claims are the above-described third power conversion unit 9 and second DC capacitor 9C, respectively.

  In the first inverter 91, a pair of upper and lower switching elements 9Qa and 9Qb in which diodes 9Da and 9Db are connected in antiparallel are connected in series with each other, and a series body of these switching elements 9Qa and 9Qb is connected to the positive side and The negative capacitors 7 and 8 are connected in parallel to the series body. Then, a second bidirectional switch 9SW formed by connecting a pair of switching elements 9Qc, each having a diode 9Dc connected in antiparallel, in series with opposite polarities, is connected to the connection point between both switching elements 9Qa, 9Qb, the positive side and the negative side It is connected between the connection points of the capacitors 7 and 8.

  The second inverter 92 connects the four switching elements 9Q1 to 9Q4, in which the diodes 9D1 to 9D4 are connected in antiparallel, to each other in a full bridge connection, and includes a second DC capacitor 9C as a DC unit that holds a DC voltage. It is provided and configured. The connection point of the switching elements 9Q1 and 9Q4 is connected to the connection point of the switching elements 9Qa and 9Qb, and the connection point of the switching elements 9Q3 and 9Q2 is connected to the input side of the second reactor 10.

  The fourth power conversion unit 16 includes a pair of upper and lower switching elements 16Qa and 16Qb in which the diodes 16Da and 16Db are connected in antiparallel, and are connected in series to each other. The switching element 16Qb side in the series body is connected to the negative side of the negative electrode side capacitor 8 at the positive electrode of the power storage unit 15. One end of the third reactor 16c is connected to the connection point between the switching elements 16Qa and 16Qb, and the other end of the third reactor 16c is connected to the power line 18.

  And each switching element 5Q1-5Q4, 6Qa-6Qc, 9Qa-9Qc, 9Q1-9Q4 which comprises said 1st power converter 5, 2nd power converter 6, and 3rd power converter 9 is as follows. Switching control is performed by a drive signal supplied from a control circuit (not shown). In addition, as each said switching element 5Q1-5Q4, 6Qa-6Qc, 9Qa-9Qc, 9Q1-9Q4, although self-extinguishing type | molds, such as IGBT, are applied here, not only this but MOSFET, A bipolar transistor or the like can be used.

Next, the operation of the uninterruptible power supply 100 will be described in detail.
First, operations of the first and second power conversion units 5 and 6 that are converters that convert AC power into DC power will be described.
When the AC power source 1 is healthy (for example, when the voltage of the AC power source 1 is from AC 80 V to AC 140 V), the b-contact 2 b of the switching relay 2 is closed, and the relay 3 b in the inrush current preventing unit 3 is closed, and the first The reactor 4, the first power conversion unit 5, and the second power conversion unit 6 supply DC power of, for example, 140 V to the positive-side capacitor 7 and −140 V, for example, to the negative-side capacitor 8.
The operation of the first and second power converters will be described with reference to operation waveform diagrams shown in FIGS. 4 and 5.

Here, the operation of the second power converter 6 will be described with reference to FIG.
In the positive half cycle of AC power supply 1, switching element 6Qb is kept off. Since the switching element 6Qc of the first bidirectional switch 6SW is turned on at the rising and falling portions of the voltage in the positive half cycle, the two power lines 20 and 18 are short-circuited. Vx (indicated by a thick solid line in FIG. 3) is zero. In the other period within the positive half cycle of the AC power supply 1, the switching element 6Qc is off, and the switching element 6Qa is turned on at this time, so that the upper positive-side capacitor 7 is set to Vx. Charged.

  In the negative half cycle of AC power supply 1, switching element 6Qa is kept off. Since the switching element 6Qc of the first bidirectional switch 6SW is turned on at the rising and falling portions of the voltage in the negative half cycle, the power lines 20 and 18 are short-circuited. Voltage Vx (indicated by a thick solid line in FIG. 3) becomes zero. In the other period within the negative half cycle of the AC power supply 1, the switching element 6Qc is off, and the switching element 6Qb is turned on at this time, so that the lower negative-side capacitor 8 becomes Vx Is charged.

  In this way, the upper positive-side capacitor 7 is charged to Vx in the positive half cycle, and the lower negative-side capacitor 8 is charged to Vx in the negative half cycle. 7 and 8 as a whole are charged with a voltage of 2 · Vx, which becomes the output voltage Vout of the second power converter 6.

Next, the operation of the first power conversion unit 5 will be described.
The first power conversion unit 5 and the first reactor 4 include a voltage Vx determined by the switching elements 6Qa and 6Qc of the second power conversion unit 6 and a voltage of the AC power supply 1 when the AC power supply 1 is in a positive half cycle. A voltage Viv (indicated by a thick broken line in FIG. 3) that fills the voltage difference from Vp · sin (ωt) is always generated. That is, the voltage Viv generated in the first power conversion unit 5 and the first reactor 4 is subjected to switching control so as to satisfy the following relational expression.
Viv = Vx−Vp · sin (ωt) (1)

Therefore, the voltage Vx applied to the second power converter 6 is
Vx = Vp · sin (ωt) + Viv (2)
It becomes.

  The first power conversion unit 5 and the first reactor 4 are switched by the switching elements 6Qb and 6Qc of the second power conversion unit 6 even when the AC power supply 1 is in the negative half cycle, as in the case of the positive half cycle. A voltage −Viv that fills the voltage difference between the determined voltage Vx and the voltage Vp · sin (ωt) of the AC power supply 1 is generated.

  Next, a specific operation of the first power converter 5 will be described with reference to an operation waveform diagram shown in FIG. In general, the converter circuit is often PWM controlled so that the current flowing from the AC power supply 1 is approximately a sine wave. However, also in the first embodiment, the current flowing from the AC power supply 1 is sine. A case where PWM control is performed so as to approximate a wave will be described.

  As described above, the first power conversion unit 5 and the first reactor 4 are voltages that fill the difference between the voltage Vx applied to the second power conversion unit 6 and the voltage Vp · sin (ωt) of the AC power supply 1. Although it operates to generate Viv, specifically, the first power converter 5 generates an output voltage so that the current io of the AC power supply 1 is approximately a sine wave.

  FIG. 4 shows an example of a voltage waveform output from the first power converter 5. As shown in FIG. 5A, if the switching element 5Q3 is turned on / off while the switching elements 5Q1 and 5Q2 are turned off and the switching element 5Q4 is turned on, the output voltage has a positive rectangular waveform. Further, as shown in FIG. 5B, if the switching element 5Q1 is turned on / off while the switching elements 5Q3 and 5Q4 are off and the switching element 5Q2 is on, the output voltage has a negative rectangular waveform. Become. Then, PWM control is performed to change the duty ratio of the rectangular wave so that the switching elements 5Q1 to 5Q4 are switched by a drive signal by a control circuit (not shown) and the current of the AC power supply 1 becomes approximately a sine wave. .

  At that time, the first reactor 4 is smoothed by applying the rectangular wave voltage as described above, and as a result, the voltage Viv generated in the first power conversion unit 5 and the first reactor 4. Is a waveform indicated by a thick broken line in FIG. In this case, the voltage Viv should have a value sufficient to fill the difference between the Vx applied to the second power converter 6 and the voltage Vp · sin (ωt) of the AC power supply 1 (see the above-described equation (1)). Therefore, the voltage Vo that becomes the peak value (peak value) of the rectangular wave for generating the voltage Viv is sufficiently smaller than the value of the voltage Vout output from the second power converter 6. For this reason, the inductance value of the 1st reactor 4 can be made small, As a result, cost is low compared with the conventional step-up type converter, and the switching loss of the 1st power converter 5 is suppressed low. be able to.

Next, the power balance handled by the first power conversion unit 5 will be described.
In FIG. 3, when attention is paid to the positive half cycle of the AC power supply 1, the power handled by the first power converter 5 is negative power (when the current is positive) during the period when the switching element 6Qc is on. ), The period during which the switching element 6Qc is off and the switching element 6Qa is on is positive power. If the two positive and negative power amounts are equal, the power balance handled by the first power conversion unit 5 (in the positive half cycle becomes zero, and a special DC power source needs to be provided in the first DC capacitor 5C portion. Absent.

  Thus, in order to make the power balance in the first power converter 5 zero, the pulse width of the voltage Vx applied to the second power converter 6 or the voltage Vout output from the second power converter 6 The value of can be controlled. That is, if the pulse width of the voltage Vx is increased by controlling the on / off period of the switching element 6Qc of the first bidirectional switch 6SW and the switching element 6Qa of the second power converter 6, the positive electric energy increases. . Further, even if the output voltage Viv of the first power conversion unit 5 is controlled by the PWM control of the first power conversion unit 5 and the voltage value of the voltage Vout output from the second power conversion unit 6 is increased, it is positive. The power value increases. Therefore, the power balance can be adjusted to be zero. In addition, since it becomes the same operation | movement also about a negative half cycle, description is abbreviate | omitted. In this way, if the power balance per cycle of the first power conversion unit 5 operating at a high frequency is zero, the first power conversion unit 5 does not require a DC power source and can be reduced in cost. . Note that when the current polarities are opposite (in the case of regenerative operation), the polarities of the respective expressions are opposite.

  However, in the case of an uninterruptible power supply, the output voltage of the third power conversion unit 9 needs to be stabilized, and the value of the voltage Vout output from the second power conversion unit 6, that is, a pair of upper and lower positive electrodes Also, the voltages of the negative side capacitors 7 and 8 are desired to be constant voltage values. Then, when the voltage of the AC power supply 1 is increased, it is necessary to increase the pulse width. However, the pulse width has an upper limit of a half cycle of the AC power supply 1, and this time becomes the upper limit of the working voltage of the AC power supply 1.

  For example, when the output voltage of the third power conversion unit 9 is AC100V, the value of the voltage Vout, that is, the voltages of the pair of upper and lower positive side and negative side capacitors 7 and 8 is the operation of the third power conversion unit 9. For example, it is desired to maintain about DC 140V. In this case, as shown in FIGS. 5A and 6A, when the voltage of the AC power supply 1 is 100 V AC, there is a margin for increasing the pulse width. Here, in FIG. 6, the alternate long and short dash line indicates current, the broken line indicates voltage, and the solid line indicates power.

However, as shown in FIG. 5 (b), when the voltage of the AC power supply 1 is about AC 125V, the pulse width of the second power conversion unit 6 is maximized and the pulse width is increased even if the voltage of the AC power supply 1 is further increased. Cannot be increased. Therefore, for example, when the voltage of the AC power supply 1 becomes about AC135V, as shown in FIG. 6B, the first power conversion unit 5 handles the voltages of the positive and negative capacitors 7 and 8 while maintaining them. The power balance cannot be kept at zero.
Therefore, a special operation for enabling the input voltage from the AC power supply 1 to be set higher while maintaining the voltages of the pair of upper and lower positive and negative capacitors 7 and 8 at predetermined values will be described below. .

As shown in FIG. 3, the voltage borne by the first power conversion unit 5 and the first reactor 4 is the difference between the input voltage waveform of the AC power supply 1 and the voltage borne by the second power conversion unit 6. The voltage waveform Viv is indicated by a broken line. And the electric power which the 1st electric power conversion part 5 bears becomes a product of the input current from AC power supply 1, and the voltage Viv mentioned above.
In the uninterruptible power supply 100, in order to bring the power factor close to 1, normally, the input current of the AC power supply 1 is controlled to be a sine wave synchronized with the phase of the input voltage, but the input voltage is high. As a result, the power borne by the first power converter 5 is maximized in the vicinity of the phases of 90 degrees and 270 degrees, which are the maximum values of the input current, and the voltage of the first DC capacitor 5C increases.

  Therefore, the second power conversion unit 6 controls the pulse width of the voltage applied to the second power conversion unit 6 so that the power balance per cycle of the first power conversion unit 5 becomes zero, and the pulse width The first power conversion unit 5 is connected to the AC power source 1 according to the situation in which AC reaches the half cycle of the AC power source, that is, immediately before the pulse width reaches the half cycle of the AC power source or the pulse width reaches the half cycle of the AC power source. The waveform of the input current is set to a current in which the third harmonic is superimposed on the sine waveform so as to lower the current value near the maximum value of the input current value. Thereby, even if the input voltage from AC power supply 1 is high, the electric power which the 1st power converter 5 bears can be made small, and adjustment of a power balance zero is attained. 7 (a) and 7 (b) show the case where the input voltage of the AC power supply 1 is AC135V. However, as shown by the thick solid line in FIG. 7 (b), the current waveform is superimposed on the third harmonic. Thus, the power balance can be adjusted to zero (thick broken line).

Although superimposing harmonics on the input current of the AC power supply 1 deteriorates the input power factor, a power factor of 0.9 is secured even in the case of FIG. Even if this control is performed when the input voltage of 1 becomes high, the influence on the AC power supply 1 is small.
Although an example in which the current waveform is formed by superimposing the third harmonic on the sine waveform is shown here, a trapezoidal current waveform that lowers the peak values near 90 degrees and 270 degrees may be used.

Next, the operation of the third power conversion unit 9 that is an inverter unit that converts DC power into AC power will be described.
As shown in FIG. 8, in the half cycle in which a positive voltage is output, the switching element 9Qb is kept off. Since the switching element 9Qc of the second bidirectional switch 9SW is turned on at the rising and falling portions of the voltage in the positive half cycle, the power lines 21 and 18 are short-circuited. Vy (shown by a thick solid line in FIG. 8) becomes zero. In the other period within the positive half cycle, the switching element 9Qc is off, and the switching element 9Qa is turned on at this time, so that the voltage of the upper positive side capacitor 7 is output.

  Further, in the half cycle in which a negative voltage is output, the switching element 9Qa is kept off. Since the switching element 9Qc of the second bidirectional switch 9SW is turned on at the rising and falling portions of the voltage in the negative half cycle, the two power lines 21 and 18 are short-circuited. Voltage Vy (indicated by a thick solid line in FIG. 8) becomes zero. In the other period within the negative half cycle, the switching element 9Qc is off, and the switching element 9Qb is turned on at this time, so that the voltage of the lower negative side capacitor 8 is output. .

In the second inverter 92 and the second reactor 10, the output voltage is a voltage Vy determined by the switching elements 9Qa and 9Qc of the first inverter 91 and a voltage Vo · sin (ωt) in the positive half cycle. A voltage Vov (indicated by a thick broken line in FIG. 8) that always fills the voltage difference is generated. That is, the voltage Vov generated by the second inverter 92 is switching-controlled so as to satisfy the following relational expression.
Vov = Vy−Vo · sin (ωt) (3)

Therefore, the output voltage Vy of the first inverter 91 is
Vy = Vo · sin (ωt) + Vov (4)
It becomes.

  In the second inverter 92 and the second reactor 10, the output voltage of Vy determined by the switching elements 9 </ b> Qb and 9 </ b> Qc of the first inverter 91 is the same as in the positive half cycle even in the negative half cycle of the output voltage. A voltage Vov that fills the voltage difference between the voltage and the output voltage Vo · sin (ωt) is generated.

Next, an operation of adjusting the power balance borne by the second inverter 92 to 0 in order to maintain the voltage of the second DC capacitor 9C of the second inverter 92 will be described.
In FIG. 8, when focusing on the positive half cycle of the output voltage, the power handled by the second inverter unit 92 is negative power (when the current is positive) during the period when the switching element 9Qc is on. The period when the switching element 9Qc is off and the switching element 9Qa is on is positive power. If the two positive and negative power amounts are equal, the power balance handled by the second inverter unit 92 in the positive half cycle becomes zero, and there is no need to provide a special DC power source in the second DC capacitor 9C.

  Thus, in order to make the power balance in the second inverter unit 92 zero, the pulse width of the voltage Vy applied to the first inverter unit 91 or the value of the voltage output from the third power conversion unit 9 is set. Control is sufficient. That is, if the pulse width of the voltage Vy is increased by controlling the on / off period of the switching element 9Qc of the second bidirectional switch 9SW and the switching element 9Qa of the first inverter unit 91, the positive electric energy increases. The voltage of the second DC capacitor 9C will decrease. Further, even if the output voltage Vov of the second inverter unit 92 is controlled by the PWM control of the second inverter unit 92 and the voltage value of the voltage output from the third power conversion unit 9 is lowered, a positive power value is obtained. To increase. Therefore, the power balance can be adjusted to be zero. In addition, since it becomes the same operation | movement also about a negative half cycle, description is abbreviate | omitted. As described above, if the power balance per cycle of the second inverter unit 92 operating at a high frequency is zero, the second inverter unit 92 does not require a DC power source, and the cost can be reduced. Note that when the current polarities are opposite (in the case of regenerative operation), the polarities of the respective expressions are opposite.

  However, in the uninterruptible power supply, the output voltage of the third power conversion unit 9 cannot normally be varied greatly. Therefore, the switching element 9Qc of the second bidirectional switch 9SW and the switching element of the first inverter unit 91 By controlling the pulse width of the voltage Vy by controlling the on / off period of 9Qa, the power balance per cycle of the second inverter unit 92 becomes zero.

  As another adjustment method, the magnitude and voltage of the differential voltage generated in the second inverter unit 92 can be adjusted by increasing or decreasing the voltage values of the positive-side capacitor 7 and the negative-side capacitor 8. The polarity can be changed, and the power balance borne by the second inverter unit 92 can be adjusted to zero. That is, when the voltage values of the positive side capacitor 7 and the negative side capacitor 8 are increased, the electric power borne by the second inverter unit 92 increases in the positive direction. At this time, the voltage of the second DC capacitor 9C decreases.

  As another adjustment method, the first inverter 91 controls the pulse width of the voltage applied to the first inverter 91 so that the power balance per cycle of the second inverter 92 becomes zero, and Depending on the situation where the pulse width reaches the half cycle of the output voltage in the third power converter 9, that is, immediately before the pulse width reaches the half cycle of the output voltage, or just before the pulse width reaches the half cycle of the output voltage. The second inverter 92 transforms the waveform of the output voltage so as to reduce the maximum voltage value of the output voltage. For example, if the third harmonic is superimposed on the AC output voltage to reduce or increase the voltage value in the vicinity of 90 ° and 270 ° of the AC output voltage, the phase borne by the second inverter 92 Since the power near 90 degrees and 270 degrees increases or decreases in the positive direction, the power balance borne by the second inverter 92 can be adjusted to zero.

  In general, the second inverter 92 bears the maximum power in the vicinity of the peak value of the output voltage, so that the voltage values of the positive side capacitor 7 and the negative side capacitor 8 are around 140 V that is the peak value of the output voltage. If this is done, the burden on the second inverter 92 can be reduced. This is particularly effective in a capacitor input load in which a large current flows near the peak value of the output voltage, and contributes to downsizing and cost reduction of the second inverter 92.

The charging operation of the power storage unit 15 from the AC power source 1 during normal operation will be described with reference to FIG.
The switching element 16Qb of the fourth power conversion unit 16 is turned on, and the third reactor is routed through the route of the negative capacitor 8 → the third reactor 16c of the fourth power conversion unit 16 → the switching element 16Qb → the negative capacitor 8. Store energy in 16c. Subsequently, the switching element 16Qb is turned off, and the energy stored in the third reactor 16c is charged in the power storage unit 15 through the route of the third reactor 16c → the diode 16Da → the power storage unit 15 → the third reactor 16c. .

Next, the charging operation of the positive electrode side and negative electrode side capacitors 7 and 8 by the power storage unit 15 during the backup operation at the time of a power failure or the like will be described.
At the time of backup operation, the switching relay 2 is switched to the a contact 2a side, the switch 3b of the inrush current prevention unit 3 is turned on, both ends of the resistor 3a are short-circuited, and the switching element 5Q3 is further turned on.
Then, the first bidirectional switch 6SW of the second power conversion unit 6 is turned on, and the power storage unit 15 → the contact a 2a of the switching relay 2 → the switch 3b → the first reactor 4 → the diode 5D1 → the switching element 5Q3 → Energy is stored in the first reactor 4 through the route of the first bidirectional switch 6SW → power storage unit 15.

  Subsequently, the first bidirectional switch 6SW is turned off, and the first reactor 4 → the diode 5D1 → the switching element 5Q3 → the diode 6Da of the second power conversion unit 6 → the positive side capacitor 7 → the power storage unit 15 → the switching relay. 2, the energy stored in the first reactor 4 is charged in the positive capacitor 7 through a route of a contact 2a → switch 3b → first reactor 4.

  Further, the semiconductor switch 16Qa of the fourth power conversion unit 16 is turned on, and energy is stored in the third reactor 16c through the route of the power storage unit 15 → the semiconductor switch 16Qa → the third reactor 16c → the power storage unit 15. Subsequently, the semiconductor switch 16Qa was turned off and stored in the third reactor 16c through the route of the third reactor 16c → the negative side capacitor 8 → the fourth power converter diode 16Db → the third reactor 16c. The energy is charged in the negative capacitor 8.

Moreover, when charging the positive electrode side capacitor 7, high efficiency can be achieved by using the first power converter 5. The first power conversion unit 5 and the first reactor 4 are operated so as to generate a voltage that fills the difference between the voltage Vx applied to the second power conversion unit 6 and the voltage of the power storage unit 15. For example, the operation is performed so that the current flowing out of the direct current 15 becomes a direct current.
For example, by turning on and off the switching element 6Qc in synchronization with the cycle of the output voltage, the power borne by the first power converter 5 is negative when the switching element 6Qc is on and positive when it is off. Thus, the power balance can be made zero by changing the width of the switching pulse.
In this way, the switching loss can be reduced by using the first power conversion unit 5 and the second power conversion unit 6.

Next, when the uninterruptible power supply 100 is started, the first DC capacitor 5C, the positive capacitor 7, the negative capacitor 8, and the second DC capacitor 9C, which are capacitors in the first to third power converters, are initially set. The operation of charging will be described. Hereinafter, this operation is referred to as a first start-up charging operation.
The operation of charging the first DC capacitor 5C, the positive capacitor 7 and the negative capacitor 8 will be described with reference to FIG.

  When the AC power supply 1 is applied in the state where the uninterruptible power supply 100 is stopped, the relay 3b of the inrush current prevention relay unit 3 is open, and the first power conversion unit 5 and the second power conversion unit 6 are open. Since the semiconductor switch is turned off, the current for charging each capacitor through the resistor 3a, the first power converter 5 and the diode in the second power converter 6 (reversely connected to the semiconductor switch) Flows.

When the voltage of the AC power supply 1 is positive, the AC power supply 1 → b contact 2b of the switching relay 2 → resistor 3a → first reactor 4 → diode 5D1 → first DC capacitor 5C → diode 5D2 → diode 6Da → positive side A current flows from the capacitor 7 to the AC power source 1, and the first DC capacitor 5C and the positive capacitor 7 are charged.
When the voltage of the AC power source 1 is negative, the AC power source 1 → the negative capacitor 8 → the diode 6Db → the diode 5D3 → the first DC capacitor 5C → the diode 5D4 → the first reactor 4 → the resistor 3a → b of the switching relay 2 A current flows in the order of contact 2b → AC power supply 1, and negative electrode side capacitor 8 and first DC capacitor 5C are charged.

Next, an operation for charging the second DC capacitor 9C, the positive-side capacitor 7, and the negative-side capacitor 8 at the time of startup will be described.
When the bypass relay 13 is normally closed (b contact), the relay 3b of the inrush current prevention unit 3 is open and the semiconductor switch of the third power conversion unit 9 is off, so that the charging operation of the first DC capacitor 5C is performed. At the same time, a current for charging each capacitor flows from the AC power supply 1 through the resistor 3a and the diode in the third power converter 9 (reversely connected to the semiconductor switch).

When the voltage of the AC power source 1 is positive, the AC power source 1 → the b contact 2b of the switching relay 2 → the resistor 3a → the bypass relay 13 → the second reactor 10 → the diode 9D3 → the second DC capacitor 9C → the diode 9D4 → the diode 9 Da → the positive side capacitor 7 → the AC power source 1 and a current flow, and the second DC capacitor 9 </ b> C and the positive side capacitor 7 are charged.
When the voltage of the AC power source 1 is negative, the AC power source 1 → negative capacitor 8 → diode 9Db → diode 9D1 → second DC capacitor 9C → diode 9D2 → second reactor 10 → bypass relay 13 → resistor 3a → switching Current flows in the order of b contact 2b → AC power supply 1 of relay 2, and negative electrode side capacitor 8 and second DC capacitor 9C are charged.

Each capacitor can adjust the upper limit voltage of charging by adjusting the ratio of capacitance, and can be charged up to a predetermined voltage. For example, if a control power source (not shown) is connected in parallel to the negative electrode side capacitor 8, the control power source starts to operate when the voltage of the negative electrode side capacitor 8 becomes equal to or higher than a predetermined voltage (for example, DC 30V or higher). The operation of a control device (for example, a microcomputer not shown) that controls the operation of 100 can be started.
However, in the first start-up charging operation described above, the voltage of each capacitor is lower than the voltage during normal operation. Therefore, in order to start normal operation, the voltage of each capacitor is further increased to the normal voltage. It needs to be charged.

Hereinafter, an operation for charging each capacitor to a normal voltage will be described. The main charging operation performed after the first starting charging operation is referred to as a second starting charging operation.
First, the relay 3b is closed and remains closed during the main operation.
When the voltage of the AC power supply 1 is positive, the first bidirectional switch 6SW is turned on and the switching element 5Q4 is switched to operate the first DC capacitor 5C by using the first reactor 4. Charge to high voltage.

  More specifically, the switching element 5Q4 of the first power converter 5 is turned on, the AC power source 1 → the b contact 2b of the switching relay 2 → the relay 3b → the first reactor 4 → the switching element 5Q4 → the diode 5D2 → the first Current is passed through a route of 1 bidirectional switch 6SW → AC power supply 1 to store energy in the first reactor 4. Subsequently, the switching element 5Q4 is turned off, and the first reactor 4 → diode 5D1 → first DC capacitor 5C → diode 5D2 → first bidirectional switch 6SW → AC power supply 1 → b contact 2b of the switching relay 2 → A current is passed through a route of relay 3b → first reactor 4, and the energy stored in the first reactor 4 is charged in the first DC capacitor 5C.

Similarly, the switching element 5Q4 is turned on and the first bidirectional switch 6SW is switched to charge the positive-side capacitor 7 to a higher voltage using the first reactor 4.
Specifically, the first bidirectional switch 6SW of the second power conversion unit 6 is turned on, and the AC power source 1 → the b contact 2b of the switching relay 2 → the relay 3b → the first reactor 4 → the switching element 5Q4 → the diode. A current is passed through a route of 5D2 → first bidirectional switch 6SW → AC power supply 1 to store energy in the first reactor 4. Subsequently, the first bidirectional switch 6SW is turned off, and the first reactor 4 → switching element 5Q4 → diode 5D2 → diode 6Da → positive side capacitor 7 → AC power source 1 → b contact 2b of the switching relay 2 → relay 3b → A current is passed through the route of the first reactor 4, and the energy stored in the first reactor 4 is charged in the positive capacitor 7.

When the voltage of the AC power supply 1 is negative, the first bidirectional switch 6SW is turned on and the switching element 5Q2 is switched to operate the first DC capacitor 5C using the first reactor 4. Can be charged to a high voltage.
Specifically, the switching element 5Q2 of the first power converter 5 is turned on, and the AC power source 1 → the first bidirectional switch 6SW → the switching element 5Q2 → the diode 5D4 → the first reactor 4 → the relay 3b → the switching relay. Current is passed through the route of b contact 2b → AC power source 1 and energy is stored in first reactor 4. Subsequently, the switching element 5Q2 is turned off, and the first reactor 4 → the relay 3b → the b contact 2b of the switching relay 2 → the AC power source 1 → the first bidirectional switch 6SW → the diode 5D3 → the first DC capacitor 5C → A current is passed through a route of the diode 5D4 → the first reactor 4, and the energy stored in the first reactor 4 is charged in the first DC capacitor 5C.

Similarly, the switching element 5Q2 is turned on and the first bidirectional switch 6SW is switched to charge the negative-side capacitor 8 to a higher voltage using the first reactor 4.
Specifically, the first bidirectional switch 6SW is turned on, and the AC power source 1 → the first bidirectional switch 6SW → the switching element 5Q2 → the diode 5D4 → the first reactor 4 → the relay 3b → the b contact of the switching relay 2 Current is passed through a route of 2b → AC power source 1 and energy is stored in the first reactor 4. Subsequently, the first bidirectional switch 6SW is turned off, and the first reactor 4 → the relay 3b → the b contact 2b of the switching relay 2 → the AC power source 1 → the negative side capacitor 8 → the diode 6Db → the switching element 5Q2 → the diode 5D4. → Current flows through the route of the first reactor 4, and the energy stored in the first reactor 4 is charged in the negative capacitor 8.

Note that the charging voltage of the first DC capacitor 5 </ b> C by boosting using the first power conversion unit 5 and the first reactor 4 is the switching element 5 </ b> Q <b> 1 to 5 </ b> Q <b> 4 constituting the first power conversion unit 5. It is desirable to use a voltage such as a withstand voltage phase (for example, about 80% of the withstand voltage).
Further, as the charging voltage of the positive side capacitor 7 and the negative side capacitor 8 by the boost using the second power conversion unit 6 and the first reactor 4, a voltage suitable for the operation of the third power conversion unit 9 is used. Is desirable.

Next, the operation of charging the second DC capacitor 9C of the second inverter 92 to the normal operating voltage will be described with reference to FIGS.
First, the relay 3b is closed and the bypass relay 13 is also closed.
When the voltage of the AC power supply 1 is positive, the second bidirectional switch 9SW is turned on and the switching element 9Q2 is switched to operate the second DC capacitor 9C using the second reactor 10. Charge to a high regular voltage.

  Specifically, the switching element 9Q2 is turned on, and the AC power source 1 → b contact 2b of the switching relay 2 → relay 3b → bypass relay 13 → second reactor 10 → switching element 9Q2 → diode 9D4 → second bidirectional switch Current is passed through a route of 9 SW → AC power supply 1, and energy is stored in the second reactor 10. Subsequently, the switching element 9Q2 is turned off, and the second reactor 10 → the diode 9D3 → the second DC capacitor 9C → the diode 9D4 → the second bidirectional switch 9SW → the AC power source 1 → the b contact 2b of the switching relay 2 → A current flows through a route of relay 3b → bypass relay 13 → second reactor 10, and the energy stored in the second reactor 10 is charged to the second DC capacitor 9C.

Similarly, the positive capacitor 7 can be charged to a higher voltage using the second reactor 10 by turning on the switching element 9Q2 and switching the second bidirectional switch 9SW.
Specifically, the second bidirectional switch 9SW is turned on, and the AC power source 1 → the b contact 2b of the switching relay 2 → the switch 3b → the bypass relay 13 → the second reactor 10 → the switching element 9Q2 → the diode 9D4 → the second. Current is passed through the route of the bidirectional switch 9SW → AC power supply 1, and energy is stored in the second reactor 10. Subsequently, the second bidirectional switch 9SW is turned off, the second reactor 10, the switching element 9Q2, the diode 9D4, the diode 9Da, the positive side capacitor 7, the AC power source 1, the b contact 2b of the switching relay 2, and the relay 3b. The current flows through the route of the bypass relay 13 → the second reactor 10, and the energy stored in the second reactor 10 is charged in the positive capacitor 7.

Even when the voltage of the AC power supply 1 is negative, the second bidirectional switch 9SW is kept on, and the switching element 9Q4 is switched to operate the second DC capacitor using the second reactor 10. 9C can be charged to a higher voltage.
Specifically, the switching element 9Q4 is turned on, and the AC power source 1 → second bidirectional switch 9SW → switching element 9Q4 → diode 9D2 → second reactor 10 → bypass relay 13 → relay 3b → b contact of the switching relay 2 Current is passed through a route of 2b → AC power source 1 and energy is stored in the second reactor 10. Subsequently, the switching element 9Q4 is turned off, the second reactor 10, the bypass relay 13, the relay 3b, the b contact 2b of the switching relay 2, the AC power source 1, the second bidirectional switch 9SW, the diode 9D1, and the second. A current is passed through a route of the DC capacitor 9C → the diode 9D2 → the second reactor 10, and the energy stored in the second reactor 10 is charged in the second DC capacitor 9C.

Similarly, the negative capacitor 8 can be charged to a higher voltage by using the second reactor 10 by turning on the switching element 9Q4 and switching the second bidirectional switch 9SW.
Specifically, the second bidirectional switch 9SW is turned on, and the AC power source 1 → second bidirectional switch 9SW → switching element 9Q4 → diode 9D2 → second reactor 10 → bypass relay 13 → relay 3b → switching relay. Current is passed through a route of 2 b contact 2b → AC power source 1 and energy is stored in the second reactor 10. Subsequently, the second bidirectional switch 9SW is turned off, the second reactor 10 → the bypass relay 13 → the relay 3b → the b contact 2b of the switching relay 2 → the AC power source 1 → the negative capacitor 8 → the diode 9Db → the switching element. A current is passed through a route of 9Q4 → diode 9D2 → second reactor 10, and the energy stored in the second reactor 10 is charged in the negative electrode side capacitor 8.

  Note that the charging voltage of the second DC capacitor 9 </ b> C by boosting using the second inverter 92 and the second reactor 10 is a voltage such as a withstand voltage phase of the switching elements 9 </ b> Q <b> 1 to 9 </ b> Q <b> 4 constituting the second inverter 92. (For example, about 80% of the breakdown voltage) is desirable.

  According to the present embodiment, the first power conversion unit 5 deforms the input current waveform so as to reduce the maximum current value of the input current waveform from the AC power source 1, so that the input voltage of the AC power source 1 is used. An uninterruptible power supply with a wide range can be obtained.

  The second power converter 6 controls the pulse width of the voltage applied to the second power converter 6 so that the power balance per cycle of the first power converter 5 is zero, and the pulse Since the first power conversion unit 5 deforms the input current waveform so as to reduce the maximum current value of the input current waveform from the AC power source 1 according to the situation where the width reaches the half cycle of the AC power source 1, An uninterruptible power supply with a wide use range of the input voltage of the power supply 1 can be obtained.

  In addition, the first inverter 91 that operates with a one-pulse drive signal applied every half cycle of the output voltage and converts positive and negative DC power into AC power, and the input is connected to the output of the first inverter 91, the high frequency And a second inverter 92 that is a single-phase full-bridge inverter that operates at the same time, and the second inverter 92 maintains the voltage of the second DC capacitor 9C that is the DC power source of the second inverter 92. Since the output voltage waveform is deformed so as to reduce the voltage maximum value of the output voltage waveform in the power failure power supply device 100, there is no need to provide a DC power source for maintaining the voltage of the second DC capacitor 9C, and the uninterruptible power supply device 100 can be reduced in size and cost.

  The first inverter 91 controls the pulse width of the voltage applied to the first inverter 91 so that the power balance per cycle of the second inverter 92 becomes zero, and the pulse width is the orthogonal power conversion. The second inverter 92 deforms the waveform of the AC output voltage so as to reduce the maximum voltage value of the AC output voltage of the third power conversion unit 9 according to the situation where the half cycle of the AC output voltage in the device is reached. Therefore, it is not necessary to provide a dedicated DC power source to maintain the voltage of the second DC capacitor 9C, and the uninterruptible power supply 100 can be reduced in size and cost.

  Further, the first power conversion unit 5 and the second power conversion unit 6 control the voltages of the positive side capacitor 7 and the negative side capacitor 8 to be equivalent to the maximum value of the AC output voltage of the uninterruptible power supply 100. Therefore, the power consumed by the second inverter 92 can be reduced, and the uninterruptible power supply 100 can be reduced in size and cost.

  The second power conversion unit 6 controls the width of one pulse applied every half cycle of the AC power supply 1 to increase or decrease the voltage values of the positive-side capacitor 7 and the negative-side capacitor 8, thereby Since the voltage of the second DC capacitor 9C is increased or decreased, there is no need to provide a DC power source for maintaining the voltage of the second DC capacitor 9C, and the uninterruptible power supply 100 can be reduced in size and cost. it can.

  When the AC power supply 1 is connected and started, the first DC capacitor 5C, the positive-side capacitor 7 and the negative-side capacitor 8 which are the DC power sources of the first power converter 5 are connected from the AC power source 1 through the resistor 3a. Therefore, it is not necessary to provide a bidirectional DC / DC converter to charge the first DC capacitor 5C, and a low-cost and high-efficiency uninterruptible power supply can be obtained.

  The first DC capacitor 5C is charged via the resistor 3a, and then the switching element 5Q4 of the first power conversion unit 5 is switched to perform the first power via the first reactor 4. Since the voltage up to the voltage phase of the switching element of the conversion unit 5 is charged, there is no need to provide a dedicated circuit such as a bidirectional DC / DC converter to charge the first DC capacitor 5C, and low cost and high efficiency An uninterruptible power supply can be obtained.

  The first inverter 91 is connected to the positive side capacitor 7 and the negative side capacitor 8 and operates with a drive signal of one pulse applied every half cycle of the output voltage to convert positive and negative DC power into AC power, A second inverter 92 that is a single-phase full-bridge inverter that operates at a high frequency and is connected to the output of one inverter 91, and one end connected to the output of the second inverter 92 to supply AC power to the load 14. The second reactor 10 and a second relay unit 13 that short-circuits the other end of the second reactor 10 and the other end of the inrush current preventing unit 3 are connected to the AC power source 1 and activated. Sometimes, the second DC capacitor 9C, which is the DC power source of the second inverter 92, is charged from the AC power source 1 via the resistor 3a and the second relay unit 13, so that the second DC capacitor It is not necessary to provide a dedicated circuit of the bidirectional DC / DC converter or the like in order to charge the sub 9C, it is possible to obtain a high efficiency uninterruptible power supply at low cost.

  The second DC capacitor 9C is charged up to a voltage such as a withstand voltage phase in the switching element of the second inverter 92 via the second reactor 10 by switching the switching elements 9Q2 and 9Q4 of the second inverter 92. Therefore, it is not necessary to provide a dedicated circuit such as a bidirectional DC / DC converter for charging the second DC capacitor 9C, and a low-cost and high-efficiency uninterruptible power supply can be obtained.

  In the present embodiment, the case where the bypass relay 13 is normally closed has been described. However, when the bypass relay is normally open (a contact), the control power supply is first connected in parallel by the first start-up charging operation. The second negative charging capacitor 8 is charged to a predetermined voltage value or more, and after the control power supply operates and the control device operates, the bypass relay 13 is controlled to be closed to perform the second start-up charging operation, It is also possible to charge the second DC capacitor 9C to a normal voltage.

In addition to the configuration shown in FIG. 1, the semiconductor element of the second power conversion unit 6 is connected to the positive side capacitor 7 and the negative side capacitor 8 as shown in FIG. 9A, and diodes 6 </ b> Da, 6 </ b> Db. It is also possible to change the transistors 6Qa and 6Qb connected in reverse parallel to the diodes 6D1 and 6D2.
Further, as shown in FIG. 9B, the four transistors 6Qa, 6Qb, 6Qc, and 6Qc with the diodes connected in antiparallel are connected to the four transistors 6Qa1, 6Qa2, 6Qb1, and 6Qb2 with the diodes connected in antiparallel. Two diodes 6D3 and 6D4 may be used. In this case, since the voltage borne by the transistor is halved, a transistor with a smaller rated voltage can be used, so that the loss of the transistor can be reduced.
Further, as shown in FIG. 9C, the first bidirectional switch 6SW may be deleted.

  In addition to the configuration shown in FIG. 1, the semiconductor element of the third power conversion unit 9 includes four transistors in which diodes are connected in reverse parallel as in FIG. 9B, and the diodes are connected in reverse parallel. Alternatively, four transistors and two diodes may be used. In this case, since the withstand voltage of the transistor can be halved, a transistor having a low on-resistance can be used when the transistor is constituted by a power MOS transistor. Further, the second bidirectional switch 9SW may be deleted.

  In addition, by adopting a structure in which the first power conversion unit and the fourth power conversion unit can be deleted or replaced with a reactor, when configuring a low-cost product that is not a high-efficiency product and a high-efficiency product, The diversion rate can be increased.

  Further, in the present embodiment, the first inverter 91 that operates the third power converter 9 with a one-pulse drive signal applied every half cycle of the output voltage and converts positive and negative DC power into AC power; The second inverter 92 is a single-phase full-bridge inverter that is connected to the output of the first inverter 91 and operates at a high frequency. However, a known half-bridge inverter or a known full-bridge inverter may be used.

3 inrush current prevention unit, 4 first reactor, 5 first power conversion unit,
6 second power converter, 7 positive side capacitor, 8 negative side capacitor,
9 third power converter, 10 second reactor, 13 bypass relay,
15 power storage unit, 16 fourth power conversion unit,
91 1st inverter, 92 2nd inverter, 100 uninterruptible power supply.

Claims (9)

A first power conversion unit connected to one power line of the AC power source and being a single-phase full-bridge inverter;
The first power converter is connected between the output of the first power converter and the other power line of the AC power supply, and operates with a one-pulse drive signal applied every half cycle of the AC power supply to convert alternating current into positive and negative direct current. Two power converters;
A positive-side capacitor to which power is supplied by the second power converter, and a negative-side capacitor,
The AC power converter according to claim 1, wherein the first power conversion unit deforms the input current waveform so as to reduce a current maximum value of the input current waveform from the AC power supply.   The second power conversion unit controls the pulse width of the voltage applied to the second power conversion unit so that the power balance per cycle of the first power conversion unit becomes zero, and the pulse width is determined by the AC power source. The first power conversion unit deforms the input current waveform so as to reduce a maximum current value of the input current waveform from the AC power supply according to a situation that reaches a half cycle of The AC / DC power converter described.   3. The input current waveform is obtained by superimposing a third harmonic current so as to reduce the maximum current value in synchronization with the period of the voltage waveform of the AC power supply. AC power converter. A first inverter connected to the positive and negative DC power supplies, operating with a one-pulse drive signal applied every half cycle of the output voltage, and converting the DC power of both DC power supplies into AC power; A second inverter that is a single-phase full-bridge inverter connected to the output of the inverter and operating at a high frequency,
The second inverter has a second capacitor which is a DC power supply, and the output voltage is reduced so as to reduce the maximum voltage of the output voltage in the orthogonal power converter in order to maintain the voltage of the second capacitor. The orthogonal power converter characterized by changing the waveform of.   The first inverter controls the pulse width of the voltage applied to the first inverter so that the power balance per cycle of the second inverter becomes zero, and the pulse width is the output voltage in the orthogonal power converter. 5. The orthogonal power conversion device according to claim 4, wherein the second inverter transforms the waveform of the output voltage so as to reduce the maximum voltage value of the output voltage in accordance with a situation in which the half cycle of the output voltage is reached. .   6. The output voltage waveform of the second inverter is a waveform obtained by superimposing a third harmonic on a basic sine wave so as to maintain the second capacitor voltage. Orthogonal power converter.   The AC / DC power converter according to any one of claims 1 to 3, and a DC power source for positive and negative electrodes connected to a positive side capacitor and a negative side capacitor of the AC / DC power converter. An uninterruptible power supply comprising the orthogonal power conversion device according to any one of items 6.   The first power conversion unit and the second power conversion unit control the voltages of the positive-side capacitor and the negative-side capacitor so as to correspond to the maximum value of the output voltage of the uninterruptible power supply. Uninterruptible power supply.   The second power conversion unit controls the voltage of the second capacitor by controlling the width of one pulse applied every half cycle of the AC power supply to increase or decrease the voltage value of the positive side capacitor and the negative side capacitor. The uninterruptible power supply according to claim 7 or 8, wherein the uninterruptible power supply is raised or lowered.

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