JP2008220049A - Uninterruptible power system - Google Patents

Abstract

A power factor by a parallel converter in an uninterruptible power supply that supplies input power from a commercial power source to a load and converts DC power of a battery to AC power and supplies the load as AC power in the event of a power failure Provided is an uninterruptible power supply in which a part of a load current waveform is not cut off even when improvement control accuracy is poor or power factor improvement control is not performed.
A control circuit of an uninterruptible power supply adds a section in which a pre-conduction section is added or a post-conduction section to a half cycle section of the polarity of an input voltage corresponding to the switching element of the changeover switch. The changeover switch was controlled so as to conduct in the section.
[Selection] Figure 1

Description

  The present invention relates to an uninterruptible power supply apparatus that supplies input power from a commercial power source to a load, and supplies power to the load using energy stored in a battery when the commercial power source fails.

  In the conventional uninterruptible power supply device, when the abnormality of the input voltage of the AC power at the input terminal is not detected, the changeover switch is controlled so that the switching element that conducts the current having the same polarity as the input voltage to the input terminal is conducted, When the parallel converter is controlled to adjust the current flowing through the parallel converter so that the battery energy becomes the specified value and the power factor of the AC power input to the input terminal is 1, switching is performed when an abnormality in the input voltage is detected. The parallel converter is controlled so that the switch is cut off and the battery is used as an energy source to supply AC power of a predetermined voltage to the load (see, for example, Patent Document 1).

JP 2003-259567 A

  However, in the conventional uninterruptible power supply, the power factor improvement control system by the parallel converter is bad and the power factor is deviated from 1, for example, when the load current is in phase with the input voltage, the current is positive. Even when the voltage is negative, since the switching element of the changeover switch is not conducting while the voltage is negative, there is a problem that a part of the load current waveform is cut off.

  The present invention has been made to solve the above-described problems in an uninterruptible power supply, and even when the power factor correction control accuracy by the parallel converter is poor or even when there is no power factor correction control, the load current waveform An object is to provide an uninterruptible power supply that is partially uninterrupted.

  An uninterruptible power supply according to the present invention is an uninterruptible power supply that supplies input power from a commercial power source to a load, and converts the DC power of the battery to AC power and supplies the load as AC power when the commercial power source fails. In parallel with the commercial power supply, a voltage detection circuit for detecting the input voltage of the AC power input to the input terminal of the uninterruptible power supply, a changeover switch for flowing a current having the same polarity as the input voltage when the commercial power supply is normal The first power converter connected to the output terminal of the changeover switch and the DC power output from the first power converter are charged to the battery when the commercial power is normal, and the DC power of the battery is A charge booster circuit for boosting and supplying the first power converter, a second power converter connected in series to the commercial power supply to the output terminal of the changeover switch, and a voltage detection circuit And a control circuit for controlling said first power converter and the change-over switch based on the detection result. The changeover switch includes a first parallel circuit in which the first diode element and the first switching element are connected in antiparallel, and a second parallel circuit in which the second diode element and the second switching element are connected in antiparallel. The first parallel circuit and the second parallel circuit are connected in series and in opposite directions, and the control circuit has an input voltage corresponding to the first switching element with respect to the first switching element. In the second half cycle section of the polarity of the input voltage to which the second switching element corresponds to the second switching element. The first switching element is turned on in the first half cycle section of the polarity of the input voltage corresponding to the first switching element. Conduction is performed in a section obtained by adding a post-conduction section, and is conducted in a section obtained by adding the second post-conduction section to the second half cycle section of the polarity of the input voltage corresponding to the second switching element with respect to the second switching element. Thus, the changeover switch is controlled.

  In the uninterruptible power supply device of the present invention, the first switching element is made conductive in the section obtained by adding the first pre-conduction section to the first half cycle section of the polarity of the input voltage corresponding to the first switching element. The second switching element is made to conduct in a section obtained by adding the second previous conduction section to the second half cycle section of the polarity of the input voltage corresponding to the second switching element, or the second switching element The first switching element conducts in a section obtained by adding a first post-conduction section to the first half cycle section of the input voltage polarity to which the first switching element corresponds, and the second switching element has a corresponding input voltage corresponding to the second switching element. Since the changeover switch is controlled so that the second half-cycle section of the polarity is added to the second post-conduction section, the power factor is improved by the parallel converter. If control accuracy is poor or even if there is no power factor correction control, is never blocked portion of the load current waveform.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of the uninterruptible power supply according to Embodiment 1 of the present invention. In FIG. 1, the uninterruptible power supply 101 has an input terminal 14 connected to the commercial power supply 1 and an output terminal 15 connected to the load 2. Input power supplied from the commercial power source 1 is output to the load 2 via the changeover switch 3 and the second power converter 10.

  First, the configuration of the uninterruptible power supply 101 will be described. The change-over switch 3 allows a current having the same polarity as the input voltage to flow when the commercial power source 1 is normal. The change-over switch 3 includes an input voltage detection circuit 6 on the input end 14 side. 14 detects the input voltage of the AC power input to 14. The first power converter 7 is connected in parallel to the commercial power source 1 via the reactor 13 on the output end 15 side of the changeover switch 3. Further, a charge booster circuit 12 is connected to the first power converter 7 via the control circuit 4, and a battery 11 is connected to the charge booster circuit 12. The charge booster circuit 12 charges the battery 11 with the DC power output from the first power converter 7 when the commercial power source 1 is normal, and boosts the DC power of the battery 11 when the commercial power source is out of power. 7 is supplied. A second power converter 10 is connected in series with the commercial power supply 1 on the output end 15 side of the changeover switch. The control circuit 4 controls the changeover switch 3, the first power converter 7 and the second power converter 10 based on the detection result of the input voltage by the input voltage detection circuit 6.

  In the changeover switch 3, the first diode element 3a and the first switching element 3c constitute a first parallel circuit, and the second diode element 3b and the second switching element 3d constitute a second parallel circuit. In the first parallel circuit, the first diode element 3a and the first switching element 3c are connected in antiparallel, and in the second parallel circuit, the second diode element 3b and the second switching element 3d are connected in antiparallel. . Here, the reverse parallel means that the diode element and the switching element are connected in parallel, and the conduction direction of the diode element is opposite to the conduction direction when the gate of the switching element is turned on. The first parallel circuit and the second parallel circuit are connected in series and in opposite directions.

  FIG. 2 is a diagram of gate signal control of the changeover switch 3. FIG. 2 (a) is a voltage waveform of the commercial power source 1, FIG. 2 (b) is a gate signal of the first switching element 3c, and FIG. The gate signal of 2 switching element 3d is shown. The first switching element 3c corresponds to the first half cycle section in which the voltage polarity of the commercial power supply 1 is positive, and the second switching element 3d corresponds to the negative second half cycle section.

  Here, the control circuit 4 controls the two switching elements 3c and 3d of the changeover switch 3 so as to conduct in a section longer than the corresponding half cycle section. In the first switching element 3c, as shown in FIG. 2 (b), the first pre-conduction section A1 and the first post-conduction section B1 are conducted in a section added with the first half cycle section. Similarly, in the second switching element 3d, as shown in FIG. 2 (c), the second pre-conduction section A2 and the second post-conduction section B2 are conducted in a section added to the second half cycle section.

  The first power converter 7 and the second power converter 10 have, for example, a single-phase bridge inverter configuration. The first power converter is connected in parallel to the commercial power source 1 and has a power failure compensation function. The second power converter 10 is connected in series to the commercial power supply 1 and has functions of voltage fluctuation compensation and power failure compensation.

  Next, the operation will be described. First, when the commercial power supply 1 is normal (for example, when the rated voltage is AC100V, the voltage of the commercial power supply 1 is AC80V to AC120V), the control circuit 4 changes the switching element 3c, 3d is on / off controlled. If the power factor of the load is exactly 1, the waveform of the input current is in phase with the voltage waveform of the commercial power source 1. However, the power factor may deviate from 1 depending on the load.

  FIG. 3 is a diagram showing the phase difference between the input current and the input voltage as an example when the power factor is shifted. For example, assuming that the power factor is shifted to 0.9, a phase difference d (electrical angle = 25 degrees) occurs between the voltage waveform Vin of the commercial power source 1 and the current waveform Iin of the commercial power source 1. If the first pre-conducting section A1 and the second pre-conducting section A2 are not present, the first switching element 3c and the second switching element 3d are conducting in a section corresponding to 0 degree <electrical angle ≦ 25 degrees as a current advance amount. Since no current flows, the current waveform is lost.

  On the other hand, in the first embodiment, when the first pre-conducting section A1 and the second pre-conducting section A2 are set to sections corresponding to 0 degree <electrical angle θ ≦ 25 degrees, the input current advances by a power factor of 0.9. The first switching element 3c and the second switching element 3d are conductive in a region where current flows in phase. Then, the current waveform can flow without being lost.

  As an example, the case where the input current is in the leading phase has been described, but even when the input current is in the lagging phase, the first post-conduction section B1 and the second post-conduction section B2 are sections corresponding to 0 degree <electrical angle θ ≦ 25 degrees. If set to, similar results are obtained. Further, it is determined from the phase difference between the input current and the input voltage whether the input current is the leading phase or the lagging phase, and in the case of the leading phase, the first pre-conduction section A1 and the second pre-conduction section A2 are selected, and the lag phase In this case, the first post-conduction section B1 and the second post-conduction section B2 may be selected.

  In addition, the 2nd power converter device 10 produces | generates electric power so that an output voltage may become predetermined value (for example, AC100V). Thereby, even if the voltage of the commercial power supply 1 fluctuates, the output voltage from the uninterruptible power supply 101 is stabilized.

  On the other hand, when the commercial power source 1 is out of power, that is, below the allowable voltage range, the control circuit 4 determines that the input voltage is abnormal and shuts off the selector switch 3. As a result, the input power from the commercial power source 1 is stopped. Further, the control circuit 4 causes the first power converter 7 and the second power converter 10 to perform a backup operation. That is, the first power converter 7 and the second power converter 10 are operated as inverters to generate AC power having a predetermined voltage in place of the commercial power supply 1, and the energy stored in the battery 11 is supplied to the load 2.

  Next, description will be made for each period of the voltage waveform. For example, if a power failure occurs in the positive phase of the voltage waveform in FIG. 2A (25 degrees <phase <155 degrees) and the input voltage drops to 0 V, the first switching element 3c becomes conductive, The waveform can flow without missing. Further, since the second switching element 3d does not conduct, it is not conducted because the voltage applied to the second diode element 3b is a reverse voltage, and the power generated by the first power converter 7 does not flow to the input end 14 side. . Therefore, the power generated by the first power converter 7 does not decrease the output voltage. The same applies to a case where a power failure occurs in the negative phase of the voltage waveform in FIG. 2A (205 degrees <phase <335 degrees).

  For example, when a power failure occurs at the initial positive polarity of the voltage waveform in FIG. 2A (0 degree <phase ≦ 25 degrees) and the input voltage drops to 0 V, the first switching element 3c becomes conductive. The waveform can flow without missing. By the way, since the 2nd switching element 3d conduct | electrically_connects in addition to the 1st switching element 3c, the electric power which the 1st power converter 7 generate | occur | produces flows out into the input terminal 14 side, and a voltage falls. Here, the second power converter 10 generates power by compensating for the shortage due to the voltage drop. Therefore, the voltage output from the uninterruptible power supply 101 is suppressed from decreasing. The positive polarity end of the voltage waveform in FIG. 2A (155 degrees ≦ phase <180 degrees), the negative polarity initial (180 degrees <phase ≦ 205 degrees), and the negative polarity end (335 degrees ≦ phase <360 degrees). The same applies when a power failure occurs.

Embodiment 2. FIG.
FIG. 4 is a configuration diagram of the uninterruptible power supply according to Embodiment 2 of the present invention. In FIG. 4, the uninterruptible power supply 102 can adjust one or both of the first pre-conduction section A1, the second pre-conduction section A2, the first post-conduction section B1, and the second post-conduction section B2. 5 is provided. The rest is the same as in the first embodiment.

  In the second embodiment of the present invention, the first pre-conduction section A1, the second pre-conduction section A2, the first post-conduction section B1, and the second are adjusted according to the load 2 by the regulator 5 connected to the control circuit 4. For the post-conduction section B2, at least one can be adjusted to a minimum value. For example, even when the first power converter 7 does not have a power factor improvement function, a section where the output voltage does not decrease during a power failure is widened. Can do.

  In general, the power factor of the load that is supported by the uninterruptible power supply is in the range of 0.6 ≦ power factor ≦ 1, and the electrical angle corresponding to the power factor of 0.6 is 55 degrees. Therefore, when the 1st power converter 7 does not have a power factor improvement function, about 1st front conduction section A1, 2nd front conduction section A2, 1st back conduction section B1, and 2nd back conduction section B2, By adjusting to a section corresponding to a rate of 0.6, that is, an electrical angle of 55 degrees, the current waveform can be used without being lost. Furthermore, in the case of the voltage waveform of FIG. 2A, when a power failure occurs at 55 degrees <phase <125 degrees, 235 degrees <phase <305 degrees, the output voltage does not decrease. In other phases (0 degrees <phase ≦ 55 degrees, 125 degrees ≦ phase <180 degrees, 180 degrees <phase ≦ 235 degrees, 305 ≦ phase <360 degrees), the second power converter 10 compensates for the voltage. Reduces output voltage drop. By not providing the first power converter 7 with the power factor improving function, it is possible to simplify the control and reduce the loss of the first power converter 7, thereby realizing cost reduction and high efficiency.

Embodiment 3 FIG.
FIG. 5 is a configuration diagram of the uninterruptible power supply according to Embodiment 3 of the present invention. In FIG. 5, the uninterruptible power supply 103 includes a current detector that detects an input current of AC power input to the input terminal 14 between the input terminal 14 and the changeover switch 3. The current detector includes a current transformer 8 and a current detection circuit 9. The current transformer 8 measures an input current, and a signal from the current transformer 8 is input to the control circuit 4 via the current detection circuit 9. The The rest is the same as in the second embodiment.

  Based on the detection result of the input current by the current transformer 8 and the current detection circuit 9, the control circuit 4 performs the first front conductive section A1, the second front conductive section A2, the first rear conductive section B1, and the second rear conductive section. By controlling the adjuster 5 so as to adjust B2 as needed, the voltage and power handled by the second power converter 10 when a power failure occurs can be reduced, and the cost can be reduced.

  The power factor improvement control may be performed based on the detection result of the input current by the current transformer 8 and the current detection circuit 9. In that case, the adjustment range of the first pre-conducting section A1, the second pre-conducting section A2, the first post-conducting section B1, and the second post-conducting section B2 can be reduced, so that the second power converter 10 handles when a power failure occurs. Voltage and power can be further reduced.

It is a block diagram of the uninterruptible power supply in Embodiment 1. FIG. 3 is a diagram of gate signal control of a changeover switch in the first embodiment. FIG. 3 is a diagram illustrating a phase difference between an input current and an input voltage when the power factor is shifted in the first embodiment. It is a block diagram of the uninterruptible power supply in Embodiment 2. It is a block diagram of the uninterruptible power supply in Embodiment 3.

Explanation of symbols

  101 to 103 uninterruptible power supply, 1 commercial power supply, 2 load, 3 changeover switch, 3a to 3b diode element, 3c to 3d switching element, 4 control circuit, 5 regulator, 6 input voltage detection circuit, 7 first power conversion 8 Current transformer 9 Current detection circuit 10 Second power converter 11 Battery 12 Charge booster circuit 13 Reactor 14 Input end 15 Output end

Claims (5)

In the uninterruptible power supply that supplies the input power from the commercial power source to the load, and converts the DC power of the battery into AC power at the time of a power failure of the commercial power source and supplies the load to the load as AC power,
A voltage detection circuit for detecting an input voltage of AC power input to an input terminal of the uninterruptible power supply, a changeover switch for flowing a current having the same polarity as the input voltage when the commercial power supply is normal, and the commercial power supply In parallel, the first power converter connected to the output terminal of the changeover switch and the DC power output from the first power converter are charged to the battery when the commercial power is normal, and the commercial power Sometimes a charge booster circuit that boosts the DC power of the battery and supplies it to the first power converter, a second power converter connected in series to the commercial power supply to the output terminal of the changeover switch, A control circuit that controls the changeover switch, the first power converter, and the second power converter based on a detection result in a voltage detection circuit;
The changeover switch includes a first parallel circuit in which a first diode element and a first switching element are connected in antiparallel, and a second parallel in which a second diode element and a second switching element are connected in antiparallel. A first parallel circuit and the second parallel circuit are connected in series and in opposite directions,
The control circuit conducts the first switching element in a section obtained by adding a first previous conduction section to a first half cycle section of the polarity of the input voltage corresponding to the first switching element, and the second switching element. The switching element is made conductive in a section obtained by adding a second pre-conduction section to the second half cycle section of the polarity of the input voltage corresponding to the second switching element, or the switching element is connected to the first switching element The first switching element is conducted in a section obtained by adding a first post-conduction section to the first half cycle section of the polarity of the input voltage corresponding to the first switching element, and the second switching element corresponds to the second switching element. The changeover switch is controlled to conduct in a section obtained by adding a second post-conduction section to the second half-cycle section of the polarity of the input voltage. Uninterruptible power supply that.   And a regulator connected to the control circuit, the regulator being capable of adjusting the first pre-conduction section and the second pre-conduction section or the first post-conduction section and the second post-conduction section. The uninterruptible power supply according to claim 1.   A current detector for detecting an input current of AC power input to the input terminal of the uninterruptible power supply, and the control circuit, based on a detection result of the current detector, The uninterruptible power supply according to claim 2, wherein the regulator is controlled to adjust the second pre-conduction section or the first post-conduction section and the second post-conduction section.   The first pre-conducting section and the second pre-conducting section or the first post-conducting section and the second post-conducting section are sections corresponding to an electrical angle greater than 0 degree and 55 degrees or less. The uninterruptible power supply according to claim 1 or 2.   In the second power converter, in the first pre-conduction section and the second pre-conduction section or in the first post-conduction section and the second post-conduction section, the first switching element and the second switching element are simultaneously The uninterruptible power supply according to any one of claims 1 to 3, wherein AC power is output by compensating for a decrease in output voltage caused by conduction.

Images