JP5347476B2 - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a conduction noise to an AC power supply input system side and a load side, even in a case of supplying power to a load in the state that the rectifying unit stops power converting operation to a DC power. <P>SOLUTION: In the power conversion apparatus, of two switching elements constituting a switching arm series connection part SA1 as the rectifying unit 11, the switching element Sx on a low voltage side is maintained in a conductive state while the switching element Su on a high voltage side in a shutoff state, in power failure operation. Thereby, a resonance route, which is formed resulting from the state that the switching elements Sx, Su are maintained in the shutoff state, is not formed to control the generation of the conduction noise caused by the resonance route, with a corresponding reduction in the conduction noise in the power failure operation. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a power conversion device that converts DC power obtained by rectifying an AC power supply input by a rectifier or DC power of a DC power source into AC power and supplies the AC power to a load.

Conduction noise and radiated noise generated by power converters may affect other devices. Therefore, these noises may be caused by CISPR (International Commission on Radio Interference) or VCCI (information processing equipment, etc. Regulated by the Regulatory Council.
FIG. 10 shows an example of a noise terminal voltage measurement system of an uninterruptible power supply device subject to noise regulation.

  As shown in FIG. 10, the noise terminal voltage measurement system of this uninterruptible power supply is configured such that a LISN (pseudo power supply network) is connected between a single-phase AC power supply system 1 and a load 2 connected in a single-phase three-wire system. 3) An uninterruptible power supply 4 is configured, and the uninterruptible power supply 4 includes an input filter 4a as a noise filter, a main converter 4b, and an output filter 4c as a noise filter.

The main converter 4b includes a rectifying unit 11, a DC intermediate voltage unit 12, and an inverter unit 13. The connection terminals BAT + and BAT- between the rectifying unit 11 and the DC intermediate voltage unit 12 are shown in FIG. A backup circuit 14 is connected.
The main converter 4b of the uninterruptible power supply 4 shown in FIG. 10 has a general circuit configuration described in, for example, Patent Literature 1 and Non-Patent Literature 1.

  That is, the R phase of the single-phase AC power is connected to the rectifying unit 11 via the normal mode reactor L1, and between the R-phase power line of the single-phase AC power and the S-phase power line of the single-phase AC power, A filter capacitor C1 is connected to the AC power supply system 1 side of the normal mode reactor L1, and an LC filter circuit for suppressing switching ripple is formed by the capacitor C1 and the normal mode reactor L1. Also, a relay circuit for cutting off the R-phase and S-phase power lines between the LC filter circuit constituted by the normal mode reactor L1 and the capacitor C1 and the input filter 4a (for noise terminal voltage reduction). Ry is inserted.

The rectifying unit 11 includes a switching element such as an IGBT and a diode connected in reverse parallel to the switching element as one arm, an arm including the switching element Su and the diode Du, and an arm including the switching element Sx and the diode Dx. The switching arm series connection portion SA1 has a configuration connected in series.
Similarly, the inverter unit 13 is configured by a switching arm series connection unit SA2 having a configuration in which an arm composed of the switching element Sw and the diode Dw and an arm composed of the switching element Sz and the diode Dz are connected in series.

The DC intermediate voltage unit 12 includes a capacitor series connection unit CA having a configuration in which capacitors Cdc1 and Cdc2 are connected in series. The switching arm series connection unit SA1, the capacitor series connection unit CA, and the switching arm series connection unit SA2 include: The AC power supply system 1 is connected in parallel from this side.
Then, one end of the normal mode reactor L1 is connected to a connection point between the switching elements Su and Sx of the switching arm series connection part SA1. In addition, an S-phase power line is connected to a connection point between the capacitors Cdc1 and Cdc2 of the capacitor series connection CA. Further, one end of the reactor L2 is connected to a connection point between the switching elements Sw and Sz of the switching arm series connection part SA2, and the other end of the reactor L2 is connected to the output filter 4c as an R-phase power line.

A capacitor C2 is connected between the other end of the reactor L2 and the S-phase power line, and the reactor L2 and the capacitor C2 form an LC filter circuit that suppresses switching ripple.
Further, the backup circuit 14 shown in FIG. 11 has a configuration in which, for example, a battery 14a, a capacitor 14b, a transformation function unit 14c, and a capacitor 14d are connected in parallel. Various circuit configurations such as a step-up chopper and a flyback converter are assumed as the transforming function unit 14c, but any circuit configuration may be used as long as a predetermined DC voltage can be generated.

In such a configuration, when power is supplied from the AC power supply system 1 to the load 2, the operation of the uninterruptible power supply 4 when the output voltage of the AC power supply system 1 is normal (hereinafter also referred to as normal operation operation). The operation is as follows.
That is, the AC power input from the AC power supply system 1 supplied to the uninterruptible power supply 4 via the LISN 3 is input to the rectifying unit 11 via the LC filter circuit including the normal mode reactor L1 and the capacitor C1. The switching elements Su and Sx constituting the switching arm series connection portion SA1 are PWM-controlled and rectified so that the input current is controlled in a sine wave shape and the capacitors Cdc1 and Cdc2 constituting the capacitor series connection portion CA are controlled. Energy is stored, and the voltage across the capacitor series connection CA is controlled so as to become the specified voltage Vdc.

Then, the switching elements Sw and Sz constituting the switching arm series connection unit SA2 are PWM-controlled to perform an inverter operation, thereby generating a stable arbitrary AC voltage from the specified voltage Vdc at both ends of the smoothed capacitor series connection unit CA. This is supplied to the load 2.
Then, conduction noise and radiation noise generated by the switching operation of each switching element are reduced below the regulation value by the input filter 4a and the output filter 4c connected to the AC power supply system 1 side and the load 2 side.

On the other hand, when the prescribed AC power is not supplied to the uninterruptible power supply 4 such as when the AC power supply system 1 fails, the uninterruptible power supply 4 performs the following operation during a power failure operation.
That is, when the AC power supply system 1 fails, the main circuit 4b and the input filter 4a are disconnected by the relay circuit Ry, the main converter 4b and the AC power system 1 are disconnected, and the backup shown in FIG. Electric power is supplied to the load 2 using the battery 14a of the circuit 14 as an energy source. In other words, the battery voltage of the battery 14a is converted by the transformer function unit 14c and applied to the terminals BAT + and BAT− of the main converter 4b, so that the charging voltages of the capacitors Cdc1 and Cdc2 are charged to the specified voltage Vdc. To do. Then, the switching elements Sw and Sz are PWM-controlled to perform an inverter operation, thereby generating a predetermined load voltage from the energy accumulated in the capacitors Cdc1 and Cdc2, and supplying this to the load 2.

  As described above, the switching elements Sw and Sz of the inverter unit 13 perform the same operation regardless of whether or not the input power supply system 1 has a power failure. However, the switching elements Su and Sx of the rectifying unit 11 are connected to the AC power source. Depending on the state of the system 1, the AC power supply system 1 performs a rectifying operation when performing a normal operation without a power failure, but does not perform a switching operation when the AC power supply system 1 performs a power failure operation. That is, the switching elements Su and Sx maintain the cutoff state.

As described above, at the time of a power failure operation, power is supplied to the load 2 using the battery 14a of the backup circuit 14 as an energy source, so that power to the load 2 can be obtained even when a power failure occurs in the AC power supply system 1. The supply is continued.
Japanese Patent Laying-Open No. 2005-278241 (FIG. 6) Power Electronics Circuit The Institute of Electrical Engineers of Japan, Semiconductor Power Conversion System Research Committee, Ohmsha P235 Figure 6.27

By the way, the conduction noise and radiation noise generated by the switching operation of the switching element must be reduced below the regulation value not only during normal operation but also during power failure operation.
In particular, even conduction noise (noise terminal voltage) to the AC power supply system 1 during a power failure operation is subject to regulation.
However, at the time of a power failure, the main converter 4b and the AC power supply system 1 are separated by the relay circuit Ry. Ideally, even if conduction noise does not propagate to the AC power supply system 1 side, In many cases, conduction noise flows out through the formed stray capacitance.

Moreover, since the conduction noise on the AC power supply system 1 side and the conduction noise on the load side mutually interfere, the conduction noise on the load side may increase during a power failure. Therefore, regardless of the conduction noise on either the AC power supply system 1 side or the load 2 side, during a power failure operation, the main circuit operation and the conduction noise path are different from those during normal operation, and the regulation may be exceeded.
Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and even when the power supply to the load is performed in a state where the conversion operation to the DC power of the rectifying unit is stopped. An object of the present invention is to provide a power converter capable of reducing conduction noise to the AC power supply input system side and the load side.

  In order to achieve the above object, according to a power conversion device according to claim 1 of the present invention, a first state in which an AC power supply input is converted into DC power and a second state in which the conversion operation into the DC power is stopped. A rectifier that can select any one of the states, an inverter that converts DC power into AC power, generates AC power for load supply, and supplies the AC power for load supply to the load; A DC power source, and the inverter unit generates AC power for supplying the load from the DC power converted by the rectifier unit when the first state is selected by the rectifier unit, In the power converter configured to generate the load-supply AC power from the DC power of the DC power source when the second state is selected, the rectifier unit and the inverter unit are switching elements And this The switching element has at least one switching arm series connection part in which two arms are connected in series with a diode connected in antiparallel with the switching element as one arm, and the second state is selected by the rectification part. In this case, only one of the switching elements is held in a conductive state in at least one switching arm series connection portion of the rectifying portion.

Moreover, the power converter device which concerns on Claim 2 hold | maintains only the low voltage side switching element in a conduction | electrical_connection state among the two switching elements which comprise the said switching arm series connection part of the said rectification part, It is characterized by the above-mentioned. .
Furthermore, in the power conversion device according to claim 3, the rectifier selects the first state when it is determined that the AC power input is in a non-power failure state, and the AC power input is in a power failure state. When it is determined that the second state is selected, the second state is selected.

  According to the present invention, when the second state in which the conversion operation to DC power is stopped is selected in the rectifying unit, any of the two switching elements configuring the switching arm series connection unit configuring the rectifying unit is selected. Only one of them is held in a conductive state, and the switching arm series connection portion is configured to avoid the formation of a resonance path due to the stop of the conversion operation. The conduction noise can be suppressed, and the conduction noise in an abnormal state can be reduced.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic configuration diagram illustrating an example of an uninterruptible power supply to which the present invention is applied.
Since the basic configuration of FIG. 1 is the same as that of the uninterruptible power supply 4 shown in FIG. 10, the same reference numerals are given to the same parts, and detailed description thereof is omitted.
In FIG. 1, an uninterruptible power supply 4 is connected between a single-phase AC power supply system 1 and a load 2 such as a single-phase AC motor. The uninterruptible power supply 4 includes an input filter 4a, a main converter 4b, and an output filter 4c, and cuts off the R-phase power line and the S-phase power line between the input filter 4a and the main converter 4b. A relay circuit Ry is inserted.

  The main converter 4b includes an LC filter circuit composed of a capacitor C1 and a normal mode reactor L1, a switching arm series connection SA1 that performs rectification operation, a capacitor series connection CA that maintains a DC intermediate voltage at a specified voltage, and a switching that performs inverter operation. The LC filter circuit is composed of an arm series connection SA2, a reactor L2, and a capacitor C2.

Further, a backup circuit 14 as a DC power source shown in FIG. 11 is connected between the switching arm series connection part SA1 and the capacitor series connection part CA.
And between the input filter 4a and the relay circuit Ry, the AC power supply voltage is detected, and based on this, the power failure detector 21 that detects the power failure of the AC power supply system 1, and each part based on the detection result of this power failure detector 21. And a control unit 22 for controlling.

  The control unit 22 controls the relay circuit Ry to be in a conductive state when no power failure is detected by the power failure detector 21. Further, the rectifying unit 11 is rectified and PWM control is performed on the switching elements Su and Sx of the switching arm series connection unit SA1 so that the voltage across the capacitor series connection unit CA becomes the specified voltage Vdc. PWM control is performed on each of the switching elements Sw and Sz of the switching arm series connection unit SA2 that constitutes the inverter unit 13 so that becomes a predetermined AC voltage. On the other hand, when a power failure is detected by the power failure detector 21, the relay circuit Ry is switched to a cut-off state, the main conversion device 4b is disconnected from the AC power supply system 1 side, and the transformation function unit 14c of the backup circuit 14 is operated to Switching arm series connection that configures the inverter so that the voltage across the capacitor series connection CA is controlled to the specified voltage Vdc using the energy of 14a and the supply voltage to the load 2 is a predetermined AC voltage. PWM control is performed on each of the switching elements Sw and Sz of the unit SA2. When a power failure is detected, the PWM control of the switching elements Su and Sx of the switching arm series connection part SA1 constituting the rectifier circuit is stopped, the switching element Su is shut off, and the switching element Sx is held in the conductive state.

FIG. 2 is a flowchart illustrating an example of a processing procedure of arithmetic processing of the control unit 22.
The control unit 22 reads the detection result of the power failure detector 21, and if a power failure is not detected, the control unit 22 proceeds from step S1 to step S2 and maintains the relay circuit Ry in the conductive state (ON). Then, the process proceeds to step S3, where each switching element constituting the rectifying unit 11 is PWM-controlled to perform a rectifying operation, and each switching element constituting the inverter unit 13 is PWM-controlled to perform an inverter operation.

On the other hand, when a power failure is detected, the process proceeds from step S1 to step S5, and the relay circuit Ry is switched to the cut-off state (OFF). Then, the process proceeds to step S6, and among the switching elements constituting the rectifying unit 11, the switching element Sx is held in the conductive (ON) state and the switching element Su is held in the cutoff (OFF) state.
Next, the process proceeds to step S7, where each switching element constituting the inverter unit 13 is PWM controlled to operate as an inverter, and the transformer function unit 14c of the backup circuit 14 is operated, and the voltage across the capacitor series connection unit CA is set to the specified voltage. Maintain at Vdc.

Next, in the uninterruptible power supply 4 of FIG. 1, a resonance path that occurs during a power failure operation is described.
FIG. 3 shows a resonance path by simplifying the configuration of the uninterruptible power supply 4 of FIG.
As shown in FIG. 3, the relay circuit Ry maintains a cutoff state during a power failure operation.
If the switching elements Su and Sx of the switching arm series connection part SA1 that performs the rectifying operation during a power failure operation are both held in a cut-off state (since the cut-off state is held, in FIG. And Sx are described in terms of output capacitance (capacitor)), capacitor C1, normal mode reactor L1, switching element Su, switching element Sw, reactor L2, capacitor C2, and the path to capacitor C1, normal mode reactor L1, switching element Sx Resonance paths are formed, which are composed of capacitors Cdc2 and Cdc1, and a path to the switching element Sw.

Since the smallest capacitor in the resonance path is the output capacitance of the switching elements Su and Sx, the resonance frequency is mainly determined by the output capacitance of the switching elements Su and Sx and the inductances of the reactors L1 and L2. Is done. At the resonance frequency set in this way, a large current flows, which causes an increase in conduction noise.
FIG. 4 shows stray capacitance generated in the system of FIG. 1 during a power failure operation.

  For example, between the two fixed terminals of the relay circuit Ry inserted in the R-phase power line and between the two fixed terminals of the relay circuit Ry inserted in the S-phase power line Thus, stray capacitances cc1 and cc2 are formed. Further, since the reactor has a winding structure, stray capacitance with the surroundings is easily formed. For this reason, the stray capacitance cc3 is formed between the normal mode reactor L1 and the ground such as the housing.

  Further, a stray capacitance cc4 is formed between the collector side of the lower switching element Sx constituting the switching arm series connection portion SA1 of the rectifying unit 11 and a ground such as a cooling fin or a housing (not shown). Similarly, a stray capacitance cc5 is formed between the collector side of the lower switching element Sz constituting the switching arm series connection portion SA2 of the inverter unit 13 and a cooling fin (not shown) or the ground on the housing side.

For this reason, not only the load 2 side but also the conduction noise on the AC power supply system 1 side may increase through stray capacitances formed in various places in FIG.
Here, in the present invention, as shown in FIG. 1, during the power failure operation, in the switching arm series connection part SA1 of the rectifying part 11, the upper switching element Su is kept in the cut-off state and the lower switching element Sx is kept in the conductive state. ing.
For this reason, the path that conducts the switching element Sx becomes dominant, and the path that conducts the output capacitance of the switching elements Su and Sx disappears.

Conversely, when the upper switching element Su is kept in a conducting state and the lower switching element Sx is kept in a shut-off state during a power failure operation, the path through which the switching element Su is conducted becomes dominant, and the switching element Su , The path for conducting the output capacitance of Sx disappears.
As described above, by setting either the switching element Su or Sx to the conductive state, the path for conducting the output capacitance of the switching elements Su, Sx disappears. For this reason, it is possible to suppress an increase in conduction noise caused by the switching elements Su and Sx not performing a switching operation during a power failure operation.

Further, even if the resonance circuit that conducts the output capacitance of the switching element of the switching arm series connection portion SA1 disappears, resonance mainly occurs between the reactors L1 and L2 and the capacitors C1 and C2 that constitute the filter circuit. However, the resonance frequency in this case is lower than the resonance frequency in the resonance circuit that conducts the output capacitance of the switching elements Su and Sx of the switching arm series connection part SA1 shown in FIG. It is not a big problem because it is close to the filter resonance.
Therefore, it is possible to reduce the conduction noise during a power failure operation by adopting the above configuration, and it is possible to more easily realize an uninterruptible power supply that can reduce the conduction noise during a power failure operation to a regulation value or less. it can.

  Further, as shown in FIG. 1, during the power failure operation, the switching element Sx on the low voltage side is maintained in the conductive state and the switching element Su on the high voltage side is in the cut-off state in the switching arm series connection portion SA1. Here, in the case of the switching arm series connection part SA1, the emitter terminal of the switching element Su on the high voltage side fluctuates at a high frequency, whereas the emitter terminal of the switching element Sx on the low voltage side has a stable potential. In many cases, the potential of the emitter terminal of the switching element Sx is used as the reference potential of the control unit 22. In such a case, it is easier to keep the switching element Sx on the low voltage side in the conducting state than to keep the switching element Su on the high voltage side in the conducting state.

In particular, when the power source for driving the switching element Su on the high voltage side is configured by a bootstrap, it is difficult to keep the switching element Su on the high voltage side in a conductive state for a long time.
Therefore, as shown in FIG. 1, during a power failure operation, the low-voltage switching element Sx is kept in a conductive state and the high-voltage switching element Su is kept in a cut-off state. Can be easily reduced.

In the above embodiment, as shown in FIG. 1, the case where the relay circuit Ry is interposed between the input filter 4a and the LC filter circuit composed of the normal mode reactor L1 and the capacitor C1 has been described. This is not a limitation.
For example, a general noise filter applied to the input filter 4a has a configuration including a common mode choke coil 31, a line capacitor 32, and ground capacitors 33 and 34 as shown in FIG.

In this case, the relay circuit Ry for cutting off the AC power supply system 1 side at the time of the power failure operation is inserted in the middle of the elements constituting the input filter 4a. For example, the line capacitor 32 and the common mode choke coil 31 are connected to each other. Or between the common mode choke coil 31 and the grounding capacitor. In this case as well, a resonance path through the components of the input filter 4a is generated as described above.
However, even when the relay circuit Ry is inserted in the middle of the general noise filter as shown in FIG. 5, as shown in FIG. 1, during the power failure operation, the low voltage of the switching arm series connection part SA1. By setting the switching element Sx on the side to the conductive state and the switching element Su on the high voltage side to the cutoff state, it is possible to reduce the conduction noise during the power failure operation.

  In other words, as shown in FIG. 1, at the time of a power failure operation, only one of the switching elements constituting the switching arm series connection part of the rectification part that becomes a factor for forming a resonance path is held in a conductive state, and the switching arm series connection part Since the resonance path formed via the switching elements constituting the circuit is not formed, it is assumed that an LC filter circuit, a noise filter, or the like that can form a resonance path together with the switching arm series connection portion is connected. However, the formation of the resonance path can be avoided, that is, the generation of the conduction noise accompanying the generation of the resonance path can be avoided.

  In the above embodiment, as shown in FIG. 1, the main converter 4b includes an LC filter circuit including a normal mode reactor L1 and a capacitor C1, a rectifying switching arm series connection SA1, and a DC intermediate voltage generating unit. Although the case where it comprises the filter circuit which consists of the capacitor | condenser serial connection part CA of this, the switching arm serial connection part SA2 for inverters, the reactor L2, and the capacitor | condenser C2 was demonstrated, it does not restrict to this.

  For example, as shown in FIGS. 6 to 8, the functions of the LC filter circuit on the input side and the output side, the single-phase rectifier circuit, and the single-phase inverter are combined, and the rectifier circuit and the inverter each have a switching arm series connection portion. If the uninterruptible power supply device having the main conversion device 4b having the configuration is used, a problem that conduction noise increases similarly during a power failure operation occurs. Therefore, even in the uninterruptible power supply device having these configurations, a resonance path is formed. By holding only one of the switching elements of the switching arm series connection portion in the conductive state in the same manner as described above, it is possible to reduce conduction noise during a power failure operation.

  The uninterruptible power supply apparatus of FIG. 6 includes a switching arm series connection SA11 including switching elements S1, S2 connected in series and diodes D1, D2 connected in antiparallel to each of the switching elements S1, S2, A smoothing capacitor Cdc connected in parallel to both ends of the switching arm series connection portion SA11, switching elements S5 and S6 connected in series, and diodes D5 and D6 connected in antiparallel to each of the switching elements S5 and S6, A rectifying unit 41 that performs a rectifying operation, a switching element S7, S8 connected in series, and a diode D7 connected in antiparallel to each of the switching elements S7, S8, Switching arm series connection part SA13 consisting of D8, and rectification part And a composed PWM inverter unit 42 from the switching arm series connecting portion SA12 Metropolitan constituting one.

  The R-phase power line is connected to the connection point between the switching elements of the switching arm series connection part SA11 via the normal mode reactor L1, and the normal mode is connected between the R-phase power line and the S-phase power line. A capacitor C1 that constitutes an LC filter circuit that suppresses an increase in the noise terminal voltage is connected to the reactor L1. The reactor L2 is connected to the connection point between the switching elements of the switching arm series connection part SA13 constituting the inverter part 42, and the other end is connected to the load 2 as an R-phase power line. A capacitor C2 is connected between the R-phase power line and the S-phase power line, and the reactor L2 and the capacitor C2 form an LC filter circuit.

  A backup circuit 14 (not shown) shown in FIG. 11 is connected between the switching arm series connection portion SA11 and the smoothing capacitor Cdc in parallel with the switching arm series connection portion SA11. The unit SA11 stops the switching operation, and the high-voltage side switching element S1 is controlled to be in a cut-off state, and the low-voltage side switching element S2 is controlled to be in a conductive state.

  Therefore, also in the case of the configuration of FIG. 6, if the switching elements S1 and S2 of the switching arm series connection portion SA11 are both held in a cut-off state during a power failure operation, the capacitors C1 and LC that constitute the LC filter circuit A path passing through the normal mode reactor L1, the switching elements S1 and S2 of the switching arm series connection part SA11 constituting the rectifying part 41, the smoothing capacitor Cdc, the switching element S7 constituting the inverter part 42, the reactor L2 and the capacitor C2. In the case of a power failure, the switching element S2 on the low-voltage side of the switching arm series connection part SA11 is in the conductive state and the switching element S1 on the high-voltage side is in the cutoff state during the power failure operation. Switching elements S1, S2 Resonance path through to disappear. Therefore, also in this case, it is possible to suppress an increase in conduction noise during a power failure operation caused by the switching element of the rectifying unit 41 not being switched and held in a cut-off state.

FIG. 7 shows the normal mode reactor L1 connected between the capacitor C1 and the switching arm series connection part SA11 constituting the rectification part 41 in FIG. 6 replaced by the switching elements of the switching arm series connection part SA13. A normal mode reactor L1 ′ is connected between the connection point and the S-phase power line.
8 is a connection point between the switching elements of the switching arm series connection part SA11, in which the reactor L2 connected between the switching arm series connection part SA13 and the capacitor C2 constituting the inverter part 42 in FIG. And a reactor L2 'between the power line and the R-phase power line.

  7 and 8, although the connection positions of the reactors L1 ′ and L2 ′ are different, each part operates in the same manner as in FIG. 6 and temporarily shuts off the switching element of the switching arm series connection part SA11 of the rectification part 41 during a power failure operation. When the state is maintained, a resonance path passing through these switching elements is formed, and as a result, conduction noise is generated. However, as in the case of FIG. 1, the switching element S2 on the low voltage side is conductive. By keeping the switching element S1 on the high voltage side in the cut-off state, the resonance path passing through the switching element disappears, so that an increase in conduction noise during a power failure operation can be suppressed.

Next, FIG. 9 shows an example of a three-phase three-wire uninterruptible power supply.
In the case of a three-phase three-wire system, as shown in FIG. 9, the uninterruptible power supply includes interphase capacitors C31 to C33 connected to each of the three phases and reactors L31 to L33 inserted in the power lines of each phase. An LC filter circuit that suppresses switching ripple, a rectifying unit 51, a DC intermediate voltage unit 52 including a smoothing capacitor connected in parallel with the rectifying unit 51, an inverter unit 53, and a power line for each phase And an LC filter circuit configured to include reactors L34 to L36 interposed between the capacitors and interphase capacitors C34 to C36 connected between the phases and suppressing switching ripple. Each of the rectifying unit 51 and the inverter unit 53 has a configuration in which, for example, three switching arm series connection units in which two arms each composed of a switching element and a diode connected in antiparallel thereto are connected in series are connected in parallel. Have

  In such a three-phase three-wire uninterruptible power supply device, if the switching arm series connection part of the rectifying unit 51 is held in a cut-off state during a power cut-off operation, in this case as well, the cut-off state is set as described above. A resonance path is formed via the held switching arm series connection. However, in this case as well, when only the low-voltage side switching element among the series connected switching elements of the switching arm series connection part constituting the rectifier circuit is kept in the conductive state, as in the above, The increase in conduction noise in can be suppressed.

  Here, in the case of a three-phase three-wire uninterruptible power supply, one of all three switching arm series connection parts constituting the rectification part 51 is determined by the connection position of the relay circuit Ry, the connection phase of the relay circuit, or the like. There is a case where one of the switching elements needs to be held in a conductive state and a case where only one of the switching elements needs to be held in a conductive state in one or two switching arm series connection portions.

  For example, when the transformation function unit 14c of the backup circuit 14 in FIG. 11 includes a switching arm, and the switching arm of the transformation function unit 14c and the switching arm of the rectification unit 51 are shared, Only one of the switching elements is held in the conductive state in one or two switching arm series connection portions. Although the number of common switching arms of the rectifying unit 51 and the switching arm of the transforming function unit 14c varies depending on the device configuration, all other switching arms are excluded except for a switching arm added with a function of performing power conversion by switching in the event of a power failure. Any one of the switching elements may be held in a conductive state.

  Moreover, although the case where it applied to the uninterruptible power supply apparatus was demonstrated in the said embodiment, the operation | movement of a rectification | straightening part necessarily converts an alternating current power supply input into alternating current power in a non-power failure state and a power failure state. It is not necessary to select either the state (first state) or the state where the conversion operation to DC power is stopped (second state). Any configuration that operates by selecting one of the second states can be applied.

It is a block diagram which shows an example of the uninterruptible power supply to which this invention is applied. It is a flowchart which shows an example of the process sequence of the control part of FIG. It is explanatory drawing which shows an example of a resonance path. It is explanatory drawing which shows an example of the formation position of a stray capacitance. It is an example of a noise filter. It is another example of an uninterruptible power supply. It is another example of an uninterruptible power supply. It is another example of an uninterruptible power supply. It is another example of an uninterruptible power supply. It is an example of the noise terminal voltage measurement system which makes an uninterruptible power supply a test object. It is an example of a backup circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply system 2 Load 4 Uninterruptible power supply 4a Input filter 4b Main converter 4c Output filter 11 Rectification part 12 DC intermediate voltage part 13 Inverter part 14 Backup circuit 21 Power failure detector 22 Control part SA1, SA2 Switching arm series connection part Ry relay circuit

Claims (3)

A rectifying unit capable of selecting any one of a first state in which an AC power supply input is converted into DC power and a second state in which the conversion operation to the DC power is stopped;
An inverter unit that converts direct current power to alternating current power to generate alternating current power for load supply and supplies the alternating current power for load supply to the load; and
A DC power source,
When the first state is selected by the rectifier unit, the inverter unit generates AC power for supplying the load from the DC power converted by the rectifier unit, and the second state is selected. Sometimes in the power converter configured to generate the load-supply AC power from the DC power of the DC power source,
The rectifying unit and the inverter unit each include at least one switching arm series connection unit in which two arms are connected in series, with a switching element and a diode connected in antiparallel to the switching element as one arm. ,
When the second state is selected by the rectifying unit, only one of the switching elements is held in a conductive state in at least one switching arm series connection unit of the rectifying unit. .   2. The power conversion device according to claim 1, wherein, of the two switching elements constituting the switching arm series connection part of the rectifying part, only the switching element on the low voltage side is held in a conductive state.   The rectifying unit selects the first state when it is determined that the AC power supply input is in a non-power failure state, and selects the second state when it is determined that the AC power supply input is in a power failure state. The power conversion device according to claim 1, wherein the power conversion device is a power conversion device.

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