JP4759535B2 - Uninterruptible power system - Google Patents

Description

  The present invention relates to an uninterruptible power supply, and more particularly to an uninterruptible power supply that suppresses battery deterioration due to erroneous detection of a power failure.

  The constant commercial power supply method, which is one method of the uninterruptible power supply, indicates that when the commercial power is healthy, the commercial power is supplied to the load, and when a power failure is detected, the uninterruptible power supply is started and switched to battery power supply. (For example, Non-Patent Document 1).

Uninterruptible power supply (UPS) introduction practice guide, Denki Shoin. February 25, 1989

  In the technique disclosed in Non-Patent Document 1, when a power failure is detected, the power failure detection is speeded up so that the power supply to the load system is not interrupted, but the power supply environment is bad and the commercial voltage waveform is distorted. If the device is installed in such a place, there is a risk of false detection. When there is a false detection, it is switched to battery supply each time, which adversely affects the battery life. In order to avoid erroneous detection, the power failure detection sensitivity may be made dull, but there is a problem that the detection is delayed correspondingly and the power supplied to the load system is interrupted.

  The present invention has been made to solve the above-described problems, and is an uninterruptible power supply that suppresses battery deterioration caused by turning on and off when a commercial power supply is sound and erroneously detected. It aims at obtaining a power supply device.

The uninterruptible power supply according to the present invention includes a first single-phase inverter that converts DC power from a first DC power source into AC power, and a second that converts DC power from a second DC power source into AC power. A first power converter configured by connecting the AC side of the single-phase inverter in series with the AC power source and the load in parallel,
An AC side of a third single-phase inverter that converts DC power from a third DC power source into AC power is connected in series between the AC power source and the load on the load side of the first power converter. A second power converter configured to be connected; a switch connected in series to the AC power supply and an AC side of the second power converter; and opening and closing the AC power supply; and the first power converter An uninterruptible power supply device provided with the second power converter and a control device for controlling the switch, wherein the control device closes the switch as a normal operation mode when the AC power supply is in a healthy state. The first and second power converters perform control to supply power to the load,
When an abnormal state is detected in the AC power supply, as the first operation mode, the switch is opened to disconnect the AC power supply, and the first to third single-phase inverters are connected to the first to third DC power supplies. Each of them receives a supply of power, and the first and second power converters perform control to supply power to the load,
As a second operation mode following the first operation mode, the first DC power supply is supplied with electric power from an energy storage element connected to the first single-phase inverter, and a DC is supplied from the energy storage element. The second and third DC power supplies are supplied with electric power via a DC / DC converter, and the first to third single-phase inverters are supplied with electric power from the first to third DC power supplies, respectively. The first and second power converters perform control to supply power to the load.

The uninterruptible power supply according to the present invention includes a first single-phase inverter that converts DC power from a first DC power source into AC power, and a second that converts DC power from a second DC power source into AC power. A first power converter configured by connecting the AC side of the single-phase inverter in series with the AC power source and the load in parallel,
An AC side of a third single-phase inverter that converts DC power from a third DC power source into AC power is connected in series between the AC power source and the load on the load side of the first power converter. A second power converter configured to be connected; a switch connected in series to the AC power supply and an AC side of the second power converter; and opening and closing the AC power supply; and the first power converter An uninterruptible power supply device provided with the second power converter and a control device for controlling the switch, wherein the control device closes the switch as a normal operation mode when the AC power supply is in a healthy state. The first and second power converters perform control to supply power to the load,
When an abnormal state is detected in the AC power supply, as the first operation mode, the switch is opened to disconnect the AC power supply, and the first to third single-phase inverters are connected to the first to third DC power supplies. Each of them receives a supply of power, and the first and second power converters perform control to supply power to the load,
As a second operation mode following the first operation mode, the first DC power supply is supplied with electric power from an energy storage element connected to the first single-phase inverter, and a DC is supplied from the energy storage element. The second and third DC power supplies are supplied with electric power via a DC / DC converter, and the first to third single-phase inverters are supplied with electric power from the first to third DC power supplies, respectively. Since the first and second power converters perform control to supply power to the load, the power supply environment is so poor that the AC power supply includes many harmonics even though the AC power supply is in a healthy state. Even if the control device erroneously detects a power supply abnormality due to noise or the like in the situation, the power is supplied to the load without being interrupted by the power from the DC power supply of each single-phase inverter. To avoid the activation can suppress the deterioration of the battery, it is possible to realize a turn long life of the uninterruptible power supply.

Embodiment 1 FIG.
Hereinafter, an uninterruptible power supply according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a main circuit configuration diagram of an uninterruptible power supply 3 that is connected between a power source and a load and supplies stable power to the load even when an abnormality occurs in the power source.
As shown in FIG. 1, the main circuit of the uninterruptible power supply 3 connected between a single-phase AC power source 1 (hereinafter simply referred to as an AC power source) and a single-phase load 2 (hereinafter simply referred to as a load) is The first power converter 31 is formed by connecting the alternating current sides of a plurality (in this case, two) of single-phase inverters 43 and 42 (first single-phase inverter 43 and second single-phase inverter 42) in series. And a second power converter 32 composed of a single-phase inverter 41 (third single-phase inverter 41). The first power converter 31 is connected in parallel between the AC power supply 1 and the load 2 via the interconnection reactor 51 on the first power converter 31, and the second power converter 32 (single-phase inverter 41) The side is connected in series between the AC power source 1 and the load 2. The first power converter 31 is connected to the AC power supply side with respect to the second power converter 32, and the reactor 52 and the capacitor 6 serving as an output filter are provided on the load 2 side of the second power converter 32. Arrange.

  Furthermore, the uninterruptible power supply 3 includes a switch 9 that is connected in series to the AC power source 1 and the AC side of the second power converter 32 to open and close the AC power source 1. This switch 9 disconnects the AC power source 1 and the load 2 by turning off the AC power source 1 when an abnormal state occurs, and is a semiconductor such as a thyristor, triac, MOSFET, or IGBT (Insulated Gate Bipolar Transistor). A switch composed of elements may be used.

Each of the single-phase inverters 41 to 43 is configured by, for example, a full bridge inverter including a plurality of self-extinguishing semiconductor switching elements such as IGBTs having diodes connected in antiparallel. The self-extinguishing type semiconductor switching element may be a GCT, GTO, transistor, MOSFET, or the like, or a thyristor without a self-extinguishing function, as long as it can perform forced commutation operation.
The first and second power converters 31 and 32 are controlled by the control device 50. Each single-phase inverter 42, 43, 41 in the first and second power converters 31, 32 is provided with a gate drive circuit (not shown) individually in each switching element, and an inverter drive circuit in the control device 50 In response to a signal from (not shown), a pulse voltage for applying a voltage to the gate of the switching element is created. As the configuration of the gate drive circuit, since it is necessary to insulate the control circuit and the power circuit, a pulse transformer circuit or a circuit using a photocoupler is used.

  Each of the single-phase inverters 41 to 43 includes first to third DC capacitors 41a, 42a, and 43a as independent DC power sources, and can output a DC voltage charged with the polarity shown in an arbitrary period. it can. Specifically, if the DC voltage of the third single-phase inverter 41 is V1, the voltage of {−V1, 0, V1} is connected between the output terminals of the third single-phase inverter 41 depending on the on / off combination of the switching elements. Can be applied. Also, assuming that the capacitor voltage of the second single-phase inverter 42 is V2, a voltage of {−V2, 0, V2} is applied between the output terminals of the second single-phase inverter 42 by a combination of on / off of the switching elements. Can do. Further, assuming that the capacitor voltage of the first single-phase inverter 43 is V3, a voltage of {−V3, 0, V3} is applied between the output terminals of the first single-phase inverter 43 by a combination of on / off of the switching elements. Can do. In addition to a DC capacitor, a DC power source that can store DC power can be used.

The control device 50 for controlling the first and second power converters 31 and 32 receives a signal for detecting the voltage of the AC power supply 1 by a detector (not shown), and when the detected voltage is allowed to be normal, The switch 9 is closed, and the first power converter 31 is controlled to output a harmonic compensation current that cancels out the harmonic generated by the load 2. At the same time, the second power converter 32 is controlled so as to output a differential voltage between the power supply voltage and the target voltage, that is, a voltage that compensates for the voltage fluctuation of the AC power supply 1.
In this case, the output voltage of the first power converter 31 is controlled by the sum of the voltages generated by the two single-phase inverters 43 and 42 that receive the capacitors 43a and 42a serving as the first and second DC power supplies. As a result, a substantially sinusoidal AC voltage is output, and a harmonic compensation current (inverter current i _C ) that operates as an active filter and cancels the harmonic component current included in the load current i _L is generated. As a result, the current containing the harmonic component can be prevented from flowing out to the AC power source 1 side, and the power source current is can be made free of the harmonic component. The second power converter 32 receives the capacitor 41a as the third DC power supply as an input, the third single-phase inverter 41 is PWM-controlled, and the AC output voltage is connected to the AC power supply 1 via the reactor 52. Is done. The sum of the AC power supply voltage and the AC output voltage of the second power converter 32 is supplied to the load 2.

  In an abnormal state such as a power failure in which the detected voltage of the AC power supply 1 fluctuates beyond a predetermined voltage range, the switch 9 is opened to control the AC power supply 1 to be disconnected from the load 2. At this time, the first and second single-phase inverters 42 and 43 in the first power converter 31 and the third single-phase inverter 41 in the second power converter 32 are connected in series on the AC side, The first and second power converters 31 and 32 are controlled so as to output a substantially sinusoidal voltage to the load 2 by the sum of the generated voltages of all the single-phase inverters 41 to 43 connected in series. . In this case, the first power converter 31 is not subjected to current control that generates a harmonic compensation current, and the output voltage is controlled so that a stable AC voltage is applied to the load 2.

  Among the capacitors 41a to 43a that are input to the single-phase inverters 41 to 43, the capacitor 43a (third DC power source) having the maximum voltage is supplied with power from the AC power source 1 and controlled to a predetermined voltage. In the case of operation as an uninterruptible power supply, a battery 12 as an energy storage element provided in the first single-phase inverter 43 is connected, and power corresponding to the load 2 is supplied to the capacitor 43 a via the boost chopper 11. . In addition to the battery 12, the energy storage element may be an electric double layer capacitor, a lithium ion battery, or the like. If the DC voltage is sufficiently high, the boost chopper 11 may not be used.

  In addition, the power supply to the capacitors 41a and 42a of the third single-phase inverter 41 and the second single-phase inverter 42 is made up of a high-frequency transformer 71 and switching elements 81 to 83, and is capable of bidirectional power transfer. Only the necessary amount of electric power is supplied from the capacitor 43a of the first single-phase inverter 43 via the DC / DC converter 7 of the type, and the respective capacitor voltages are made constant. The power supply from the capacitor 43a to the capacitor 42a is a forward method in which the winding direction of the high-frequency transformer 71 is the same, and the switching elements 82 and 83 are turned on and off at the same timing. The power supply from the capacitor 43a to the capacitor 41a is a flyback method in which the winding of the high-frequency transformer 71 is reversed, and the switching elements 81 and 83 are turned on and off alternately. A normal forward type and flyback type DC / DC converter has a unidirectional flow of power, so the secondary side is composed of diodes. Here, switching elements 81 to 83 are used for the respective windings. So, bi-directional power transfer is realized.

  Here, the DC voltage ratio of the single-phase inverters 42 and 43 in the first power converter 31 can be arbitrarily set in the range of V2: V3 = (0.5-1): 1. Note that the total value of V2 and V3 must be larger than the voltage peak value of the AC power supply 1. The DC voltage V1 of the single-phase inverter 41 of the second power converter 32 is assumed to be smaller than V2.

  When a power failure occurs in the AC power supply 1, the switch 9 is opened instantaneously by a signal from the control device 50, the AC power supply 1 is disconnected from the load 2, and the load is applied using each single-phase inverter 41, 42, 43. 2 is supplied with power. After that, since the power supply from the AC power supply 1 is lost, the switch 10 is closed so that the power from the energy storage element such as the battery 12 is supplied to the load 2.

  FIG. 2 shows a power failure detection sequence by the uninterruptible power supply 3 in the first embodiment. When an abnormal state of the power supply voltage is detected as described above, the switch 9 is opened and the AC power supply 1 is disconnected. At this time, the switch 10 is not closed at the same time, and each single-phase inverter 41, 42, 43 is supplied with power from capacitors 41 a, 42 a, 43 a which are first to third DC power supplies provided in the DC section. Then, electric power is supplied to the load 2. This period is within a predetermined period set in advance, and the DC voltage of each single-phase inverter 41 to 43 gradually decreases. The control device 50 monitors the DC voltage V3 of the capacitor 43a of the first single-phase inverter 43. When the voltage drops by a predetermined level V3d, the control device 50 applies a load from the battery 12 to the first DC power supply (capacitor 43a) via the boost chopper 11. In response to this, power is supplied from the first DC power supply (capacitor 43a) to the second and third DC power supplies (capacitors 42a and 41a) via the DC / DC converter 7 to obtain a predetermined voltage. Control.

FIG. 3 shows a voltage waveform output by the uninterruptible power supply 3 when the AC power supply is abnormal.
In the first embodiment, since the uninterruptible power supply 3 can generate a voltage by a combination of the single-phase inverters 41, 42, 43, each single-phase inverter 42, 43 having a large DC voltage reduces the number of times of switching. By doing so, the occurrence of switching loss and noise can be reduced. Moreover, since each single-phase inverter 42 and 43 does not switch at high frequency, the driver circuit which drives switching element 81, 82, 83 is also realizable with an inexpensive structure. The output voltage waveform generation by the high-frequency PWM is performed by the third single-phase inverter 41 having a low DC voltage, so that the filter circuit can be reduced in size.

Further, it is not necessary to monitor the DC voltages V1 and V2 of the capacitors 41a and 42a of the single-phase inverters 41 and 42, and the battery start timing is determined by monitoring only the DC voltage V3 of the capacitor 43a of the first single-phase inverter 43. can do.
For the power shared by each single-phase inverter 41 to 43, the combination of output voltages is selected so that the power handled by the first single-phase inverter 43 is sufficiently larger than the power handled by each single-phase inverter 41, 42. Therefore, by monitoring the DC voltage V3 of the first single-phase inverter 43 in which the rate of change of the DC voltage increases, the number of times of charging / discharging of the battery 12 is reduced, so that deterioration of the battery is suppressed. be able to.

  When it is determined that the detection of the abnormal state is a false detection in the state where the load power is supplied with the energy of the capacitors 41a, 42a, 43a after detecting the abnormal state of the AC power supply 1, FIG. The power supply from the AC power source 1 to the load 2 is started by turning on the switch 9 again so as to shift from the first operation mode of b) to the normal operation mode of FIG.

FIG. 4 shows the concept of the operation mode of the uninterruptible power supply 3 according to the first embodiment. The thick lines shown in FIG. 4A to FIG. 4C indicate the power supply route to the load 2.
The normal operation mode is shown in FIG.
This normal operation mode is a diagram showing a power supply route to the load 2 when the AC power source 1 is in a healthy state. Electric power is supplied from the AC power supply 1 through a third single-phase inverter 41 connected in series with the load 2. Here, in order to stabilize the output voltage, when the AC power supply voltage fluctuates within an allowable range, the third single-phase inverter 41 corrects the fluctuating voltage. The first single-phase inverter 43 and the second single-phase inverter 42 connected in parallel with the load 2 are used to supply insufficient power to the third single-phase inverter 41 connected in series, to charge the battery 12, and to High power factor control is performed.

  The first operation mode shown in FIG. 4B is a diagram illustrating an operation mode when the high-speed power failure detection circuit provided in the control device 50 detects a power failure that is an abnormal state of the AC power supply 1. The AC power source 1 is disconnected by opening the switch 9, and the first to third single-phase inverters 41, 42, 43 convert the DC power of the capacitors 41a, 42a, 43a, which are the first to third DC power sources, into AC power. To supply to load 2. In this case, the power supplied to the load 2 is shared by the first to third single-phase inverters 41, 42, and 43. After this, if the power failure detection is a false detection, that is, if a power failure is erroneously detected due to harmonic distortion or noise of the AC power supply 1, the high-speed power failure detection circuit cancels the power failure and closes the switch 9. As described above, the normal operation mode in FIG.

  The second operation mode shown in FIG. 4C is the first direct current when the AC power supply 1 is not restored to the healthy state and the abnormal state continues after the transition to the first operation mode shown in FIG. When the voltage drop value of the voltage V3 reaches a predetermined value V3d or more, the control device 50 that monitors the voltage V3 of the power supply 43 activates the battery 12 that is an energy storage element, and the first single-phase inverter 43 from the battery 12 Power is supplied to the capacitor 43a of the second and third single-phase inverters 41 and 42 from the battery 12 via the DC / DC converter 7, thereby supplying a load. 2 shows a mode in which power is shared to 2.

  As described above, the uninterruptible power supply 3 according to the first embodiment operates in the normal operation mode, the first operation mode, and the second operation mode, so that the voltage of the AC power supply 1 is within an allowable range and is in a healthy state. Nevertheless, even in a situation where many harmonics are included, it is possible to continue operation while avoiding activation of the battery 12 due to erroneous detection of a power failure. Longer life of the power failure power supply 3 can be realized.

  The present invention can be used for an uninterruptible power supply as a backup power source that prevents obstruction of business reversal in a personal computer, a hospital, a bank, etc., when a general commercial power source fails for some reason.

It is a figure which shows the main circuit structure of the uninterruptible power supply by Embodiment 1. It is a figure which shows the power failure detection sequence of the uninterruptible power supply by Embodiment 1. FIG. It is a figure which shows the voltage waveform which the uninterruptible power supply by Embodiment 1 outputs when AC power supply abnormality. It is a figure which shows the operation mode of the uninterruptible power supply by Embodiment 1.

Explanation of symbols

1 AC power supply, 2 loads, 3 uninterruptible power supply, 7 DC / DC converter,
9 switch, 12 battery, 31 first power converter, 32 second power converter,
41-43 1st-3rd single phase inverter, 50 control apparatus.

Claims (8)

The AC side of a first single-phase inverter that converts DC power from the first DC power source into AC power and a second single-phase inverter that converts DC power from the second DC power source into AC power are connected in series. A first power converter configured to be connected to the AC power source and a load connected in parallel;
An AC side of a third single-phase inverter that converts DC power from a third DC power source into AC power is connected in series between the AC power source and the load on the load side of the first power converter. A second power converter configured to be connected; a switch connected in series to the AC power supply and an AC side of the second power converter; and opening and closing the AC power supply; and the first power converter An uninterruptible power supply device provided with the second power converter and a control device for controlling the switch, wherein the control device closes the switch as a normal operation mode when the AC power supply is in a healthy state. The first and second power converters perform control to supply power to the load,
When an abnormal state is detected in the AC power supply, as the first operation mode, the switch is opened to disconnect the AC power supply, and the first to third single-phase inverters are connected to the first to third DC power supplies. Each of them receives a supply of power, and the first and second power converters perform control to supply power to the load,
As a second operation mode following the first operation mode, the first DC power supply is supplied with electric power from an energy storage element connected to the first single-phase inverter, and a DC is supplied from the energy storage element. The second and third DC power supplies are supplied with electric power via a DC / DC converter, and the first to third single-phase inverters are supplied with electric power from the first to third DC power supplies, respectively. The uninterruptible power supply, wherein the first and second power converters perform control to supply power to the load. 2. The uninterruptible power supply according to claim 1, wherein in the first operation mode, the second power converter and the first power converter share power supply to the load. Power supply. In the first operation mode, the voltage drop of the voltage V3 of the first DC power supply is monitored, and when the drop value becomes a predetermined value or more, the mode is shifted to the second operation mode. The uninterruptible power supply according to claim 1. 2. The uninterruptible power supply according to claim 1, wherein in the first operation mode, when the AC power supply returns from an abnormal state to a healthy state, the switch is closed to return to the normal operation mode. The ratio of the voltage V2 of the second DC power supply and the voltage V3 of the first DC power supply is V2: V3 = (0.5-1): 1, and the voltage of the third DC power supply is The uninterruptible power supply according to claim 1, wherein the value is lower than the voltage of the second DC power supply. 2. The uninterruptible power supply according to claim 1, wherein a step-up chopper is provided between the energy storage element and the first DC power supply of the first single-phase inverter. A first single-phase inverter that converts DC power from a first DC power source controlled to a predetermined voltage into AC power, and a second that is controlled to a predetermined voltage lower than the voltage of the first DC power source Connected in parallel between the AC power source and the load, the first power converter configured by connecting the AC side with the second single-phase inverter that converts DC power from the DC power source into AC power in series And an AC side of a third single-phase inverter that converts DC power from a third DC power source controlled to a predetermined voltage lower than the voltages of the first and second DC power sources into AC power. A second power converter configured to be connected in series between the AC power supply and the load on the load side of the first power converter, and an AC of the AC power supply and the second power converter. A switch connected in series to the side to open and close the AC power supply, 1 is an uninterruptible power supply device provided with a power converter, a second power converter, and a control device for controlling the switch, wherein the control device includes the first to third single-phase inverters. The first and second power converters are controlled to output the sum of the generated voltages to the load, and when the AC power source is in a healthy state, the switch is closed as a normal operation mode, and the first and first power converters are closed. The second power converter is configured such that two power converters supply power to the load, and the first power converter outputs a harmonic compensation current that cancels the harmonics generated by the load. Performs control to output a voltage that compensates for voltage fluctuations of the AC power supply, and when an abnormal state is detected in the AC power supply, as a first operation mode, the switch is opened to disconnect the AC power supply, The first to third single-phase inverters of the second power converter receive power supply from the first to third DC power sources, respectively, and the first and second power converters to the load. While performing control to supply electric power, when the AC power supply returns from an abnormal state to a healthy state, the control is performed to close the switch and return to the normal operation mode, and after shifting to the first operation mode, When the AC power supply continues to be in an abnormal state, the voltage drop of the first DC power supply is monitored, and when the drop value exceeds a predetermined value, the second operation mode follows the first operation mode. The first DC power supply is supplied with power from an energy storage element connected to the first single-phase inverter, and the second and third DCs are supplied from the energy storage element via a DC / DC converter. Power is power The first to third single-phase inverters receive power from the first to third DC power supplies, respectively, and the first and second power converters supply power to the load. An uninterruptible power supply characterized by performing supply control. The ratio between the voltage V2 of the second DC power supply and the voltage V3 of the first DC power supply is set to V2: V3 = (0.5 to 1): 1. Uninterruptible power system.

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