JP2014239564A - Uninterruptible power supply - Google Patents

Abstract

An object of the present invention is to provide an uninterruptible power supply capable of improving the accuracy of the output voltage and improving the input power factor even when the input voltage of the AC power supply fluctuates. An uninterruptible power supply apparatus includes a charging unit that charges a power storage unit with power from an AC power source, a first power conversion unit that converts AC power into DC power, and first power conversion unit. Second power conversion means for converting the output of the power supply into AC power, and third power conversion means for discharging energy from the power storage unit 23 when an abnormality occurs in the AC power supply 1 and supplying DC power to the second power conversion means And fourth power conversion means for moving charge between the positive-side capacitor 24a and the negative-side capacitor 24b of the second power conversion means, and only for a certain period centered on the zero-cross point of the AC output Outputs a sine wave waveform. [Selection] Figure 1

Description

  The present invention relates to an uninterruptible power supply apparatus that supplies AC power from an AC power source to a load, and converts DC power stored in a power storage unit to AC power and supplies the load to the load when the voltage of the AC power source drops. is there.

  The uninterruptible power supply of the inverter type always supplies AC power to the load via the switch from the AC power source connected when the AC power source is healthy, and detects a voltage fluctuation that causes the AC power source voltage to fall below the set value. The switch is opened and AC power is supplied from the power storage unit to the load via the inverter, so that a stable power supply is always supplied to the load when the AC power supply is healthy, during a power failure, and when switching. Has been.

  However, during startup when the capacitor of the inverter unit is in a non-charged state, an inrush current suppression resistor that suppresses the inrush current during startup is used to suppress the inrush current that flows through the capacitor when connected to an AC power supply. There was a need to do. The inrush current suppression resistor has a large part size due to its large power consumption, and the inrush current suppression resistor consumes excessive inrush current and generates heat, preventing the miniaturization of the uninterruptible power supply. was there. Therefore, for example, in the power conversion device of Patent Document 1, a converter unit that converts AC power of an AC power source into DC power, a power storage unit that is used as a power source during startup and power failure, and a DC voltage or power storage converted by the converter unit. A capacitor that stores the DC voltage supplied from the unit, an inverter unit that converts the DC voltage of the capacitor into AC power, and the capacitor is charged using the power storage unit at startup, and after the capacitor reaches a predetermined voltage, the power storage unit And a control unit that switches from an AC power source to an AC power source so that an excessive inrush current does not flow through a capacitor that is in a non-charged state at the time of startup. As a result, excessive inrush current at startup can be suppressed without using an inrush current suppression resistor, so heat generation of parts can be suppressed and downsizing can be achieved, and power consumption can be reduced. Can do.

  Moreover, since the transistor of the converter part is always switched at about 20 kHz, a loss generate | occur | produces also in a converter part. As a method for reducing this converter loss, for example, in the power conversion device of Patent Document 2, when the voltage of the DC power supply exceeds a predetermined voltage, the on / off operation of the switch in the boost circuit is stopped to stop the boost operation. Loss associated with boosting can be greatly reduced, and conversion efficiency is improved.

  In addition, since an inverter always performs high-frequency switching in all regions in order to generate a sine wave, a large amount of switching loss occurs in addition to conduction loss. Since the transistor of the converter unit is always switched at about 20 kHz, a loss also occurs in the converter unit. As a method for reducing this inverter loss, for example, the power conversion device of Patent Document 3 includes a converter that boosts the voltage of a DC power source and charges the power storage unit, and an inverter that converts the output voltage of the power storage unit to AC, The inverter performs sinusoidal modulation only for a certain period of time between the AC valleys. As a result, it is possible to select a waveform that reduces the inverter loss within a range in which malfunction does not occur in the connected device, thereby improving the conversion efficiency.

International Publication No. WO2003 / 032466 JP 2006-238628 A Japanese Patent Laid-Open No. 2003-219652

  However, in the uninterruptible power supply of Patent Document 1, the inrush current is suppressed, but there is a problem that the efficiency is poor because the switching loss of the converter circuit, the inverter circuit, and the like is large.

  Moreover, in the power converter device of patent document 2, when converter switching is stopped in order to reduce converter loss, since the inrush current to a capacitor becomes large and an input power factor falls, an input power factor falls. The loss due to Further, when used in a power supply environment where the input voltage is low, there is a problem that the capacitor voltage becomes low and the output voltage becomes low.

  Further, in the power conversion device of Patent Document 3, the inverter is stopped only for a certain period in order to reduce the inverter loss. However, since the converter performs a switching operation, loss due to converter switching occurs. There was a problem.

  The present invention has been made to solve the above-described problems, and is capable of improving the accuracy of the output voltage and improving the input power factor even when the input voltage of the AC power supply fluctuates. The object is to provide a power supply.

  In order to solve the above-described problems, there are a charging unit that charges the power storage unit with power from an AC power source, a first power conversion unit that converts AC power into DC power, and a capacitor on each of the positive electrode side and the negative electrode side. A second power conversion means for converting the output of the first power conversion means into AC power; and a third power supply for supplying DC power from the power storage unit to the second power conversion means when the AC power supply is abnormal. Power conversion means, and fourth power conversion means for moving charge between the positive side capacitor and the negative side capacitor of the second power conversion means, and when the AC power supply is normal, by the charging means The charging operation is stopped, the switching operation of the first power conversion unit and the fourth power conversion unit is stopped, and a certain period centering on the zero cross point of the AC output of the second power conversion unit Is characterized in that to output only sinusoidal waveform.

  According to a third aspect of the present invention, there is provided an uninterruptible power supply apparatus comprising: a charging unit that charges the power storage unit with power from an AC power source; a first power conversion unit that converts AC power into DC power; A second power converter having a capacitor on each of the negative electrode sides for converting the output of the first power converter to AC power; discharging energy from the power storage unit when the AC power supply is abnormal; Third power conversion means for supplying direct current power to the power conversion means, and fourth power conversion means for moving charge between the positive side capacitor and the negative side capacitor of the second power conversion means, And when the AC power supply is normal, the charging operation by the charging unit is stopped, the switching operation of the first power conversion unit is stopped, and the output voltage of the second power conversion unit is The values provided, the peak voltage of the output voltage is characterized in that to control so as not to exceed a predetermined value.

According to the uninterruptible power supply of the present invention, the inverter output voltage is corrected in the low-loss operation mode in which the switching operation of the converter unit and the balance unit is stopped and the switching operation of the inverter unit is minimized. Thus, even when the input voltage of the AC power supply varies, the output voltage accuracy with respect to the target voltage can be improved and the input power factor can be improved.

It is a circuit block diagram which shows the whole structure of the uninterruptible power supply system including the uninterruptible power supply which concerns on Embodiment 1. FIG. It is a figure which shows the flow of an electric current in case the voltage of the alternating current power supply in the uninterruptible power supply which concerns on Embodiment 1 is a positive side. It is a figure which shows the flow of an electric current in case the voltage of the alternating current power supply in the uninterruptible power supply which concerns on Embodiment 1 is a negative side. It is a figure which shows the operation | movement which charges an electrical storage part with the alternating current power supply in the uninterruptible power supply which concerns on Embodiment 1. FIG. It is a figure which shows the operation | movement which charges the positive electrode side capacitor | condenser of the inverter part by the electrical storage part at the time of the power failure in the uninterruptible power supply which concerns on Embodiment 1. FIG. It is a figure which shows the operation | movement which charges the negative electrode side capacitor | condenser of the inverter part by the electrical storage part at the time of the power failure in the uninterruptible power supply which concerns on Embodiment 1. FIG. It is a figure which shows operation | movement of the balance part in the uninterruptible power supply which concerns on Embodiment 1. FIG. FIG. 3 is a diagram showing a switching operation of an inverter unit in the uninterruptible power supply according to Embodiment 1. It is a figure which shows the correction method of the inverter output voltage in the uninterruptible power supply which concerns on Embodiment 1. FIG. It is a figure which shows the control method of the inverter output voltage in the uninterruptible power supply which concerns on Embodiment 2. FIG. It is a figure which shows operation | movement of the balance part in the uninterruptible power supply which concerns on Embodiment 3. FIG. It is a figure which shows the operation | movement of the balance part in the uninterruptible power supply which concerns on Embodiment 3, and the voltage of the positive electrode side and negative electrode side capacitor | condenser of an inverter part.

  Hereinafter, an uninterruptible power supply according to an embodiment of the present invention will be described with reference to FIGS.

Embodiment 1 FIG.
FIG. 1 is a circuit block diagram showing the overall configuration of the uninterruptible power supply system including the uninterruptible power supply according to the first embodiment, and FIGS. 2 and 3 show the case where the voltage of the AC power supply is positive and negative FIG. 4 is a diagram illustrating an operation of charging the power storage unit with an AC power supply. 5 and 6 are diagrams illustrating operations of charging the positive-side capacitor and the negative-side capacitor of the inverter unit by the power storage unit at the time of a power failure, respectively. FIG. 7 is a diagram illustrating the operation of the balance unit. FIG. 8 is a diagram illustrating a switching operation of the inverter unit, and FIG. 9 is a diagram illustrating a method of correcting the inverter output voltage.

  As shown in FIG. 1, the uninterruptible power supply 100 includes a negative-side step-up / step-down unit 26, a charging unit that charges a power storage unit (battery) 23 with the power of the AC power source 1, a converter unit 27, and a backflow prevention. The first power conversion means is composed of a first power conversion means configured to convert AC power into DC power, and an inverter section 24 having capacitors 24a and 24b on the positive electrode side and the negative electrode side, respectively. The second power conversion means for converting the output of the means into AC power, the negative-side step-up / step-down unit 26, the converter unit 27, and the backflow prevention diodes 21 and 22 are provided. The third power conversion means for discharging energy and supplying DC power to the second power conversion means, and the balance unit 25, are composed of a positive side capacitor 24a and a negative side side capacitor. And a, a fourth power conversion means for moving charge between the capacitors 24b.

  In the uninterruptible power supply 100, one end of the AC power supply 1 and one end of the load 4 are connected by a common line. A pair of backflow prevention diodes 21 and 22 having the same polarity are connected in series, and the connection point is connected to the other end of the AC power supply 1. Further, there are a positive line 20a connected to the cathode of the reverse current blocking diode 21 and serving as a direct current positive electrode side, and a negative electrode line 20b connected to the anode of the reverse current blocking diode 22 and disposed as a direct current negative electrode side. An inverter unit 24 including a pair of capacitors 24a and 24b and an inverter is connected to the common line 20c, the positive line 20a, and the negative line 20b. The balance unit 25 is connected to the common line 20c, the positive line 20a, and the negative line 20b on the AC power supply 1 side. The negative electrode side step-up / step-down unit 26 is connected to the common line 20c, the positive electrode side of the power storage unit 23, and the negative electrode line 20b. Converter unit 27 is connected to AC power supply 1 in parallel.

  Between the AC power source 1 and the converter unit 27, a capacitor 28 connected in parallel with the AC power source 1 is connected to the AC power source 1 side, and a reactor 29 forming a filter and a filter is connected to the converter unit 27 side. . Further, between the capacitor 28 and the reactor 29, an a-contact of an AC power source / power storage unit changeover switch 30 for switching input between the AC power source 1 and the power storage unit 23 is connected. A power storage unit operation switch 31 is connected between the contact b of the AC power source / power storage unit switching switch 30 and the positive electrode of the power storage unit 23. In addition, a reactor 32 connected in series is connected to the output line of the inverter unit 24, and a capacitor 33 is connected to the load 4 side of the reactor 32 in parallel with the load 4. Is formed.

Next, the detail of each element which comprises the uninterruptible power supply 100 which concerns on Embodiment 1 is demonstrated.
First, the inverter unit 24 includes a positive side capacitor 24a connected between the common line 20c and the positive line 20a, a negative side capacitor 24b connected between the common line 20c and the negative line 20b, and a collector having a positive polarity. A semiconductor switch 24c connected to the line 20a; a diode 24d connected in reverse parallel to the semiconductor switch 24c; a semiconductor switch 24e whose collector is connected to the emitter of the semiconductor switch 24c; and an emitter connected to the negative electrode line 20b; The switch 24e and the diode 24f connected in antiparallel. Here, the inverter is a part composed of a semiconductor switch 24c, a diode 24d, a semiconductor switch 24e and a diode 24f, a positive side capacitor 24a and a negative side capacitor 24b, and converts DC power supplied from a DC power source into AC power. To do.

  The balance unit 25 includes a semiconductor switch 25a having a collector connected to the positive electrode line 20a, a diode 25b connected in reverse parallel to the semiconductor switch 25a, a collector connected to the emitter of the semiconductor switch 25a, and an emitter connected to the negative electrode line 20b. Semiconductor switch 25c, a diode 25d connected in reverse parallel to the semiconductor switch 25c, a reactor 25e having one end connected to the emitter of the semiconductor switch 25a and the collector of the semiconductor switch 25c, and the other end connected to the common line 20c. And is composed of.

  The negative-side step-up / down unit 26 includes a semiconductor switch 26a whose collector is connected to the positive side of the power storage unit 23, a diode 26b connected in reverse parallel to the semiconductor switch 26a, and a collector connected to the emitter of the semiconductor switch 26a. Is connected to the negative electrode line 20b, a diode 26e connected in reverse parallel to the semiconductor switch 26d, one end connected to the emitter of the semiconductor switch 26a and the collector of the semiconductor switch 26d, and the other end connected to the common line And a reactor 26c connected to 20c.

  The converter unit 27 includes diodes 27a1, 27a2, 27a3, and 27a4 that constitute the diode bridge 27a, and a semiconductor switch 27b that is connected in parallel with the diode bridge 27a.

  Further, the uninterruptible power supply 100 includes a voltage detector 34 that is a voltage detecting means for detecting the voltage of the positive side capacitor 24a and the voltage of the negative side capacitor 24b, an AC power source / power storage unit changeover switch 30, and a power storage unit operation switch. 31, a semiconductor switch 27b, a semiconductor switch 24c, a semiconductor switch 24e, a semiconductor switch 25a, a semiconductor switch 25c, a semiconductor switch 26a, and a control circuit 35 for controlling the semiconductor switch 26d.

Next, the operation of uninterruptible power supply 100 according to Embodiment 1 will be described.
In the uninterruptible power supply 100, the AC power source 1 is charged during normal operation, and the power storage unit 23 is charged during a power outage, respectively, to charge the positive side capacitor 24a and the negative side capacitor 24b of the inverter unit 24. 24c, the diode 24d, the semiconductor switch 24e and the diode 24f, the DC power output from the positive side capacitor 24a and the negative side capacitor 24b is converted into AC power as a DC power source. Supplied.

  The operation of charging the positive-side capacitor 24a and the negative-side capacitor 24b of the inverter unit 24 during normal operation will be described with reference to FIGS.

When the voltage of the AC power source 1 is on the positive side, as shown in FIG. 2A, the semiconductor switch 27b of the converter unit 27 is turned on, and the AC power source 1 → the AC power source / storage unit. The path of the changeover switch 30 → the reactor 29 → the diode 27a1 of the diode bridge 27a → the semiconductor switch 27b → the diode 27a4 of the diode bridge 27a → the AC power supply 1 is formed, and energy is stored in the reactor 29.
Subsequently, as shown in FIG. 2B, the semiconductor switch 27b of the converter unit 27 is cut off (off), and the reactor 29 → the reverse current blocking diode 21 → the positive side capacitor 24a of the inverter unit 24 → the AC power source. 1 → AC power source / power storage unit changeover switch 30 → reactor 29 is formed, and the energy stored in the reactor 29 is charged to the positive side capacitor 24a of the inverter unit 24, and the positive line 20a is connected to the common line 20c. Positive potential.

When the voltage of the AC power source 1 is on the negative side, as shown in FIG. 3A, the semiconductor switch 27b of the converter unit 27 is turned on, and the diode of the AC power source 1 → diode bridge 27a. 27a2 → semiconductor switch 27b → diode 27a3 of the diode bridge 27a → reactor 29 → AC power source / power storage unit changeover switch 30 → AC power source 1 is formed, and energy is stored in the reactor 29.
Subsequently, as shown in FIG. 3B, the semiconductor switch 27 b of the converter unit 27 is turned off (off), and the reactor 29 → the AC power source / power storage unit switching switch 30 → the AC power source 1 → the inverter unit 24. A path of the negative electrode side capacitor 24b → the reverse current blocking diode 22 → the reactor 29 is formed, and the energy stored in the reactor 29 is charged in the negative electrode side capacitor 24b of the inverter unit 24, and the negative electrode line 20b is compared with the common line 20c. Negative potential.

An operation of charging power storage unit 23 during normal operation will be described with reference to FIG.
As shown in FIG. 4A, the semiconductor switch 26d of the negative side step-up / step-down unit 26 is turned on, and the negative side capacitor 24b of the inverter unit 24 → the reactor 26c of the negative side step-up / down unit 26 → semiconductor A path from the switch 26d to the negative capacitor 24b is formed, and energy is stored in the reactor 26c.
Subsequently, as shown in FIG. 4B, the semiconductor switch 26d of the negative-side buck-boost unit 26 is turned off (off), and the reactor 26c → diode 26b → power storage unit 23 → of the negative-side buck-boost unit 26 → A path called the reactor 26 c is formed, and the energy stored in the reactor 26 c is charged in the power storage unit 23.

  The operation of supplying energy from the power storage unit 23 during a power failure and charging the positive side and negative side capacitors 24a and 24b of the inverter unit 24 will be described with reference to FIGS.

At the time of a power failure, the contact of the AC power source / power storage unit changeover switch 30 is switched to the b side, and the power storage unit operation switch 31 is short-circuited (conducted).
First, the operation of charging the positive electrode side capacitor 24a is shown in FIG. As shown in FIG. 5A, the semiconductor switch 27b of the converter unit 27 is turned on, and the power storage unit 23 → the power storage unit operation switch 31 → the AC power source / power storage unit changeover switch 30 → the reactor 29 → the diode. A path of the diode 27a1 of the bridge 27a → the semiconductor switch 27b → the diode 27a4 of the diode bridge 27a → the power storage unit 23 is formed, and energy is stored in the reactor 29.
Subsequently, as shown in FIG. 5B, the semiconductor switch 27b of the converter unit 27 is cut off (off), and the reactor 29 → the reverse current blocking diode 21 → the positive side capacitor 24a of the inverter unit 24 → the power storage unit. 23 → Power storage unit operation switch 31 → AC power source / power storage unit changeover switch 30 → Reactor 29 is formed, and the energy stored in the reactor 29 is charged to the positive capacitor 24a.

Next, the operation of charging the negative electrode side capacitor 24b is shown in FIG. As shown in FIG. 6 (a), the semiconductor switch 26a of the negative-side step-up / step-down unit 26 is turned on, and the power storage unit 23 → the semiconductor switch 26a → the reactor 26c of the negative-side side step-up / down unit 26 → the power storage unit. 23 is formed, and energy is stored in the reactor 26c.
Subsequently, as shown in FIG. 6B, the semiconductor switch 26a of the negative-side buck-boost unit 26 is cut off (off), and the reactor 26c of the negative-side buck-boost unit 26 → the negative-side capacitor of the inverter unit 24 A path of 24b → diode 26e → reactor 26c of the negative side boosting / lowering unit 26 is formed, and the energy stored in the reactor 26c is charged in the negative side capacitor 24b.

  Further, using the energy stored in the positive side capacitor 24a and the negative side capacitor 24b of the inverter unit 24 charged as described above, the inverter unit 24 converts the DC power into the AC power, and the load 4 receives the AC power. However, the voltage of the positive side capacitor 24a and the voltage of the negative side capacitor 24b of the inverter unit 24 may become unbalanced due to an unbalance of the load 4 or the like. Therefore, in order to eliminate this unbalance, a balance unit 25 is provided in parallel with the inverter unit 24.

For example, when the voltage of the negative side capacitor 24b becomes high, as shown in FIG. 7A, the semiconductor switch 25c of the balance unit 25 is turned on, and the negative side capacitor 24b → the balance unit. Energy is stored in the reactor 25e through a path of 25 reactors 25e → semiconductor switch 25c → negative capacitor 24b.
Subsequently, as shown in FIG. 7B, the semiconductor switch 25c is turned off (off), and the reactor 25e → the diode 25b of the balance unit 25 → the positive capacitor 24a of the inverter unit 24 → the reactor 25e. The positive capacitor 24a is charged with the energy stored in the reactor 25e, and the voltages of the positive capacitor 24a and the negative capacitor 24b are balanced.

  Next, an operation for correcting the output voltage from the inverter unit 24 in the uninterruptible power supply 100 according to Embodiment 1 so as to approach the target output voltage will be described with reference to FIGS. 1 to 3, 8, and 9. To do. The correction is performed by stopping the switching operation of the converter unit 27 and the balance unit 25 for a predetermined time and outputting a sine wave waveform from the inverter unit 24 only during a fixed period centered on the zero cross point of the AC output.

Input voltage _{V in} of the AC power supply 1, for example, when close to 90V~110V and rated voltage, a path shown in FIG. 2 (b) and 3 (b), the positive capacitor 24a and the negative electrode side capacitor 24b By performing charging, the semiconductor switch 27b of the converter unit 27 and the semiconductor switches 25a and 25b of the balance unit 25 are stopped (cut off) to suppress switching loss.

  In the section A (A1, A2) shown in FIG. 8, the semiconductor switch 24c of the inverter unit 24 performs a switching operation and outputs a sine wave waveform. In the section B, the switching operation of the semiconductor switch 24c is stopped, and the switching loss is reduced by always turning on (on). The semiconductor switch 24e of the inverter unit 24 performs a switching operation in a section C (C1, C2) shown in FIG. 8, and outputs a sine wave waveform. In section D, the switching operation of the semiconductor switch 24e is stopped, and the switching loss is reduced by always turning on (on).

The condition for shifting to the section A1 → B is that the ideal output voltage value of the uninterruptible power supply 100 is obtained by subtracting the ON voltage of the semiconductor switch 24c from the voltage of the positive capacitor 24a of the inverter unit 24 detected by the voltage detector 34. When the voltage value is equal to or higher than the voltage value, and when the voltage value is equal to or lower than the voltage value, the process proceeds to the section B → A2.
Further, the condition for shifting to the section C1 → D is that the ideal output voltage value is equal to or higher than the voltage value obtained by subtracting the ON voltage of the semiconductor switch 24e from the voltage of the negative capacitor 24b of the inverter unit 24 detected by the voltage detector 34. If the voltage value is less than or equal to this voltage value, the process proceeds to the section D → C2.

In practice, the input voltage V _in of the AC power supply 1, since there is a change, in accordance with the variation, since the voltage of the positive electrode side capacitor 24a and the negative electrode side capacitor 24b of the inverter 24 varies, also the inverter output voltage fluctuate. Therefore, the inverter output voltage is corrected by changing the setting of the ideal sine wave output voltage. FIG. 9 is a diagram illustrating a method of correcting the inverter output voltage.
9 (a) is illustrates a correction method of the inverter output voltage when the input voltage V _in of the AC power supply 1 is lowered. In this case, correction is performed so that the effective value of the ideal sine wave increases. Further, FIG. 9 (b) shows a correction method of the inverter output voltage when the input voltage V _in of the AC power supply 1 increases. In this case, correction is performed so that the effective value of the ideal sine wave is lowered.
The correction value of the instantaneous value of the ideal sine wave can be obtained by the following equation (1).

Instantaneous value of ideal sine wave = √2 × (target output voltage effective value + Vr) × sinθ (1)

Here, Vr = Kp × (target output voltage effective value−output voltage effective value ((measured value))
+ Ki × Σ (target output voltage effective value−output voltage effective value ((measured value)).

  Thus, in the uninterruptible power supply according to Embodiment 1, the inverter output voltage is reduced in the low-loss operation mode in which the switching operation of the converter unit and the balance unit is stopped and the switching operation of the inverter unit is minimized. By performing this correction, it is possible to improve the output voltage accuracy with respect to the target voltage and improve the input power factor even when the input voltage of the AC power supply varies.

Embodiment 2. FIG.
FIG. 10 is a diagram illustrating waveforms of the inverter output voltage and the current flowing through the load in the uninterruptible power supply according to the second embodiment. The operation in the second embodiment is different from the operation in the first embodiment in that the switching operation of the inverter unit is performed in all phases. The configuration of the uninterruptible power supply according to Embodiment 2 is the same as that of Embodiment 1.

Input voltage V _in of the AC power supply 1, when higher than the rated voltage, the converter section 27, when stopping the switching operation of the balance unit 25, to the input voltage V _in of the AC power supply 1, the inverter unit Since the voltages of the positive electrode side capacitor 24a and the negative electrode side capacitor 24b of 24 become low, the charging currents of the positive electrode side capacitor 24a and the negative electrode side capacitor 24b increase in the paths shown in FIGS. 2 (b) and 3 (b).

  In order to suppress this, an output voltage maximum value is provided for the output voltage from the inverter unit 24, and the peak voltage of the output voltage is a predetermined value (for example, the peak voltage of the ideal sine wave of the ideal output voltage value). 75% to 95%) is controlled so that the output current flowing to the load 4 does not increase rapidly.

  Specifically, the switching operation of the inverter unit 24 is controlled by the control circuit 35, and the control circuit 35 compares the calculated output target voltage with the measured value of the output voltage sensor 12, and the difference ΔV ( = Measurement value absolute value of output voltage sensor 12 -output target voltage) The conduction (on) time of the semiconductor switch 24c and the semiconductor switch 24e of the inverter unit 24 is increased or decreased to control the output voltage to approach the output target voltage. .

  In the case of the output voltage on the positive side, when the difference ΔV> 0, the conduction (on) time of the semiconductor switch 24c of the inverter unit 24 is reduced, the absolute value of the output voltage is lowered, and the difference ΔV <0. In this case, the conduction (on) time of the semiconductor switch 24c of the inverter unit 24 is increased, and the absolute value of the output voltage is increased.

  In the case of the negative output voltage, if the difference ΔV> 0, the conduction (on) time of the semiconductor switch 24e of the inverter unit 24 is reduced, the absolute value of the output voltage is lowered, and the difference ΔV <0. In this case, the conduction (on) time of the semiconductor switch 24e of the inverter unit 24 is increased, and the absolute value of the output voltage is increased.

  The control circuit 35 holds the changeable maximum output voltage value shown in FIG. 10B. When the absolute value of the ideal sine wave is less than the maximum output voltage value, the control circuit 35 sets the value of the ideal sine wave to the maximum output voltage. If the value is greater than or equal to the value, the output target voltage is calculated so as to be the maximum output voltage value. As a result, a peak voltage suppression region in which the output voltage is suppressed to the maximum output voltage value is formed.

  Thus, in the uninterruptible power supply according to Embodiment 2, even when the switching operation of the converter unit and the balance unit is stopped, the output voltage maximum value is provided for the output voltage from the inverter unit, and the output By controlling so that the peak voltage of the voltage does not exceed a predetermined value, the inrush of the input current is reduced by suppressing the current change to the load, and the input power factor can be improved.

Embodiment 3 FIG.
FIG. 11 is a diagram illustrating the operation of the balance unit in the uninterruptible power supply according to the third embodiment, and FIG. 12 illustrates the operation of the balance unit according to the third embodiment and the positive side and negative side capacitors of the inverter unit. It is a figure which shows a voltage. The operation in the second embodiment is different from the operation in the first embodiment in that the switching operation of the inverter unit is performed in all phases. The configuration of the uninterruptible power supply according to Embodiment 3 is the same as that of Embodiment 1.

Next, operation | movement of the balance part 25 of this Embodiment is demonstrated using FIG.11 and FIG.12. When the input voltage Vin of the AC power supply 1 is on the positive side, _{in the} section A1 shown in FIG. 12, the semiconductor switch 25a of the balance unit 25 is shut off (off), and the semiconductor switch 25c performs a switching operation. The power of the negative side capacitor 24b of the inverter unit 24 is charged to the positive side capacitor 24a of the inverter unit 24 via the reactor 25e of the balance unit 25, and the voltage is boosted to the target charging voltage V _T + (FIG. 11 (a)). Here, the target charge voltage _{V T} +, a certain percentage (80% to 95%) relative to the peak voltage of the input voltage _{V in} that is measured by the input voltage sensor 11.
Subsequently, in the section B1 shown in FIG. 12, the semiconductor switch 25c of the balance unit 25 is switched in order to maintain the target charging voltage V _T +.
In the section C1 of FIG. 12 shows a case where the input voltage V _in of the AC power supply 1 is higher than the voltage of the positive electrode side capacitor 24a of inverter 24, the positive electrode side capacitor 24a is, and FIG. 2 (b) It is charged by the path of and the voltage rises. Although it is in the region of the switching operation of the semiconductor switch 25c of the balance unit 25, it exceeds the target charging voltage V _T +, and thus is substantially cut off (off).
In the section D1 shown in FIG. 12, the inrush current input voltage V _in is lowered because not generated, the semiconductor switch 25c of the balance unit 25 to cut off (OFF).

When the input voltage Vin of the AC power supply 1 is negative, _{in the} section A2 shown in FIG. 12, the semiconductor switch 25c of the balance unit 25 is cut off (off), and the semiconductor switch 25a of the balance unit 25 performs a switching operation. As a result, the power of the positive side capacitor 24a of the inverter unit 24 is charged to the negative side capacitor 24b of the inverter unit 24 via the reactor 25e of the balance unit 25, and is boosted to the target charging voltage V _T − (FIG. 11 ( b)). Here, the target charging voltage _{V T} - is a certain percentage (80% to 95%) relative to the peak voltage of the input voltage _{V in} that is measured by the input voltage sensor 11.
In the section B2 shown in FIG. 12, the semiconductor switch 25a of the balance unit 25 is allowed to perform a switching operation in order to maintain the target charging voltage V _T −.
In the section C2 shown in FIG. 12 shows a case where the input voltage V _in of the AC power supply 1 is higher than the voltage of the negative electrode side capacitor 24b of the inverter unit 24, the negative electrode side capacitor 24b of the inverter unit 24, FIG. It is charged through the path 3 (b) and the voltage rises. Although it is the region of the switching operation of the balance unit 25 semiconductor switch 25a, it exceeds the target charging voltage V _T − and is substantially cut off (off).

Incidentally, the boost to the target charging voltage V _{T +,} V _{T -} is a constant percentage of the peak voltage of the input voltage V _in, it is possible to change settings of the ratio.

  The operation of other configurations is the same as that of the second embodiment, and a description thereof will be omitted.

  As described above, in the uninterruptible power supply according to Embodiment 3, even when the switching operation of the converter unit is stopped, the positive side capacitor and the negative side are boosted by increasing the voltages of the positive side capacitor and the negative side capacitor. The inrush current to the capacitor is reduced, and the input power factor can be improved.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  Moreover, in the figure, the same code | symbol shows the same or an equivalent part.

1 AC power supply, 4 load, 11 input voltage sensor, 12 output voltage sensor, 21, 22 backflow prevention diode, 23 power storage unit, 24 inverter unit, 24a positive side capacitor, 24b negative side capacitor, 24c, 24e semiconductor switch, 25 Balance unit, 25a, 25c semiconductor switch, 25e reactor, 26 negative side step-up / step-down unit, 26a, 26d semiconductor switch, 26c reactor, 27 converter unit, 27a diode bridge, 27b semiconductor switch, 30 AC power supply / storage unit switching switch, 31
Power storage unit operation switch, 29 reactor, 34 voltage detector, 35 control circuit, 100 uninterruptible power supply.

Claims (6)

Charging means for charging the power storage unit with the power of the AC power supply;
First power conversion means for converting AC power to DC power;
A second power converter having a capacitor on each of the positive electrode side and the negative electrode side and converting the output of the first power converter to AC power;
Third power conversion means for supplying DC power from the power storage unit to the second power conversion means when the AC power supply is abnormal;
A fourth power conversion means for moving charge between a positive electrode side capacitor and a negative electrode side capacitor of the second power conversion means,
When the AC power supply is normal, the charging operation by the charging unit is stopped, the switching operation of the first power conversion unit and the fourth power conversion unit is stopped, and the AC output of the second power conversion unit An uninterruptible power supply that outputs a sine wave waveform only for a certain period centered on the zero-cross point. Voltage detecting means for detecting the voltage of the positive and negative capacitors,
The output voltage of the sine wave part is corrected so that the output voltage of the second power conversion means approaches the target output voltage based on the detected voltage when the AC power supply is normal. The uninterruptible power supply according to Item 1. Charging means for charging the power storage unit with the power of the AC power supply;
First power conversion means for converting AC power to DC power;
A second power converter having a capacitor on each of the positive electrode side and the negative electrode side and converting the output of the first power converter to AC power;
Third power conversion means for discharging energy from the power storage unit when the AC power supply is abnormal and supplying DC power to the second power conversion means;
A fourth power conversion means for moving charge between a positive electrode side capacitor and a negative electrode side capacitor of the second power conversion means,
When the AC power supply is normal, the charging operation by the charging unit is stopped, the switching operation of the first power conversion unit is stopped, and the output voltage maximum value is set with respect to the output voltage of the second power conversion unit. And providing an uninterruptible power supply that controls the peak voltage of the output voltage so as not to exceed a predetermined value.   When the input voltage of the second power conversion means is positive, the fourth power conversion means causes the voltage of the positive capacitor to be boosted to the positive target charge voltage from the negative capacitor. When the charge is transferred to the positive capacitor and the input voltage is negative, the charge from the positive capacitor to the negative capacitor is increased so that the voltage of the negative capacitor is boosted to the negative target charge voltage. The uninterruptible power supply according to claim 1 or 3, wherein   When the input voltage is on the positive side, the phase for transferring charge from the negative capacitor to the positive capacitor is limited to a range of 0 ° to 90 °, and when the input voltage is negative, 5. The uninterruptible power supply according to claim 4, wherein a phase for transferring electric charge from the positive electrode side capacitor to the negative electrode side capacitor is limited to a range of 180 ° to 270 °.   5. The uninterruptible power supply according to claim 4, wherein the positive and negative target charging voltages have a constant ratio with respect to a peak voltage of the input voltage of the AC power supply, and the setting of the ratio can be changed. .

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