JP5971685B2 - Power converter - Google Patents

Description

  Embodiments described herein relate generally to a power conversion device in which chopper circuits and inverter circuits having different rated DC voltages and different capacitor capacities are connected in series.

  A power conversion apparatus that combines a plurality of inverters and outputs the output by gradation control is used, for example, in a voltage fluctuation compensator that monitors voltage fluctuations such as an instantaneous voltage drop of a power system and compensates for the voltage drop.

  A conventional power converter is connected to a power system in series and includes a plurality of inverter circuits that output a compensation voltage with either positive or negative polarity. Each inverter circuit is provided with a full-bridge inverter composed of four semiconductor switching elements with diodes connected in antiparallel and a charging capacitor serving as an energy source.

  The charging capacitor is charged with a DC voltage from an external power source, and the charged DC voltage is converted to AC and output to a load. Moreover, a steady short circuit switch is provided in parallel at the output terminal of each inverter circuit. The charging capacitors in each inverter circuit are charged with different voltages by the charging diode and the charging transformer.

  In addition to the conventional technology as described above, AC terminals of a plurality of inverters having different rated voltages are connected in series, and a DC / DC converter is used to supply a charging current, and the DC capacitors of each inverter are set to different voltage values. A power converter for charging is also known.

JP 2002-359928 A JP 2005-130562 A JP 2011-109801 A

  In such a conventional power converter, the AC sides of a plurality of independent single-phase inverters are connected in series, and each charging capacitor on the DC input side of each single-phase inverter is charged with a different voltage. The Each charging capacitor is charged with a voltage by a charging diode, a charging resistor, and a secondary winding of the charging transformer provided independently, and the primary winding of the charging transformer is connected to the power system.

  Therefore, a plurality of charging capacitors that are input to each single-phase inverter are each provided with a charging circuit, and the number of charging circuits increases as the number of series of single-phase inverters increases. There was a problem that it was necessary.

  On the other hand, in the charging method of the power conversion device using the DC / DC converter, the DC / DC converter is used only for charging, so there is a drawback that the number of parts of the device increases. Further, since a DC / DC converter is used, there is a problem that only a direct current can be used as a power source.

  It is an object of the present invention to obtain a power conversion device that individually charges each DC capacitor constituting a chopper circuit and an inverter circuit by adopting a method of charging through a resistor. Another object of the present invention is to obtain a power conversion device to which a power supply can be applied regardless of whether it is DC or AC.

The power converter of this embodiment has the following configuration.
(1) A full-bridge connection of a plurality of switching elements, an inverter circuit having a DC capacitor to be charged connected to the plurality of switching elements, a power source for charging a DC capacitor provided in the inverter circuit, It is a power conversion device having a charging resistor that limits a current when a DC capacitor is charged and a short-circuit switch connected in parallel with the charging resistor.

(2) The inverter circuit is connected to the charging power source in a plurality of stages, and the rated DC voltage and the capacitor capacity of the DC capacitor to be charged in each stage of the inverter circuit are different from each other in at least some of the inverter circuits. It is different from the rated DC voltage and capacitor capacity of the inverter circuit.

(3) The plurality of switching elements provided in each inverter circuit is provided with a control device that independently turns on / off each switching element.

(4) Instead of the inverter circuit, a power conversion device having a chopper circuit having a DC capacitor to be charged connected in parallel with a plurality of switching elements is also an embodiment of the present invention.

The circuit diagram which shows the power converter device of 1st Embodiment. The circuit diagram which shows the 1st charge path | route of the upper side capacitor in 1st Embodiment. The circuit diagram which shows the 2nd charge path | route of the upper side capacitor in 1st Embodiment. The circuit diagram which shows the charge path | route of the lower capacitor | condenser in 1st Embodiment. The circuit diagram which shows the power converter device of 2nd Embodiment. The circuit diagram which shows the charge path | route of each capacitor | condenser in 2nd Embodiment. The circuit diagram which shows the charge path | route of each capacitor | condenser in the state which turned on the specific switching element in 2nd Embodiment. A circuit diagram showing an example of a charge course of a 3rd embodiment. The circuit diagram which shows the other example of the charge path | route of 3rd Embodiment. A circuit diagram showing an example of a charge course of a 4th embodiment. A circuit diagram showing an example of a charge course of a 5th embodiment. A circuit diagram showing an example of a charge course of a 6th embodiment.

  Hereinafter, embodiments of a power conversion device according to the present invention will be described with reference to the drawings.

1. First Embodiment A first embodiment will be described with reference to FIG. This embodiment includes a diode-clamped full-bridge inverter 1 having a charging capacitor, a charging resistor 2 that limits a current when the capacitor is charged, a short-circuit switch 3 that short-circuits the charging resistor after charging, a single-phase AC power supply 4, and a power conversion device Is composed of a reactor 5 linked to a single-phase AC power source 4.

  The full-bridge inverter 1 includes eight switching elements (hereinafter referred to as elements) sw001 to 004, sw011 to 014, four clamp diodes (hereinafter referred to as diodes) d001, d002, d011, and d012, and upper and lower direct currents. This is a three-level inverter composed of capacitors c001 and c002 and capable of outputting three voltage levels in one phase.

  As the elements sw001 to 004 and sw011 to 014, a semiconductor device using silicon carbide or gallium nitride, an IGBT, a MOS-FET, or the like according to a DC voltage or a load current is used. Each of the elements sw001 to 004 and sw011 to 014 has a freewheeling diode (not indicated in the figure) connected in reverse parallel.

  The full bridge inverter 1 is provided with a control device for independently turning on and off these elements sw001 to 004 and sw011 to 014. In addition, since the control apparatus for turning on / off each element which comprises the inverter circuit used for a power converter device independently is a well-known technique as shown in FIG. 1, FIG. 2 of patent document 2. This embodiment does not particularly explain.

  The upper and lower DC capacitors c001 and c002 are charged by the power output from the single-phase AC power supply 4 by energy storage means (corresponding to a conventional charging capacitor) of the power converter. The energy accumulated in the DC capacitors c001 and c002 is output as an alternating current to a load side (not shown) by turning on and off each element provided in the full bridge inverter 1.

  In the present embodiment, as the first stage of the full-bridge inverter 1, the first upstream elements sw001 and sw002 and the first downstream elements sw011 and sw012 are located between the positive potential point P and the negative potential point N. Connected in series. Similarly, as the second stage of the full-bridge inverter 1, the second upstream elements sw003 and sw004 and the second downstream elements sw013 and sw014 are arranged in parallel with each element of the first stage. In addition, the positive potential point P and the negative potential point N are connected in series.

  The diodes d001 and d002 are connected in series between the connection point of the first upstream elements sw001 and sw002 and the connection point of the first downstream elements sw003 and sw004. The diodes d011 and d012 are connected in series between the connection point of the second upstream elements sw011 and sw012 and the connection point of the second downstream elements sw013 and sw014. The connection point of the diodes d001 and d002 connected in series and the connection point of the diodes d011 and d012 connected in series are connected to each other.

  Between the positive potential point P and the negative potential point N, an upper DC capacitor c001 and a downstream DC capacitor c002 are connected in series. The upper DC capacitor c001 and the downstream DC capacitor c002 connected in series with respect to the first-stage elements sw001, sw002, sw011 and the second-stage elements sw003, sw004, sw013, sw014 Connected in parallel. The connection point of the upper DC capacitor c001 and the downstream DC capacitor c002 is connected to the connection points of the diodes d001, d002, d011, and d012.

  The charging resistor 2 is connected to an intermediate point between the elements sw002 and sw003 serving as an input unit of the full bridge inverter 1. An intermediate point between the elements sw012 and sw013 is an output part of the full-bridge inverter 1, and this part is connected to the single-phase AC power source 4.

  In this embodiment configured as described above, by turning on / off specific elements sw002 and sw012 or sw003 and sw013, only the upper DC capacitor c001 or the lower DC capacitor c002 can be charged and input. It is possible to charge up to the maximum voltage of the single-phase AC power supply 4.

  A current path when charging the upper DC capacitor c001 using FIGS. 2 and 3 and a current path when charging the lower DC capacitor c002 are shown using FIG. In each figure, it is assumed that the short-circuit switch 3 is open and the charging current passes through the charging resistor 2.

  In the period in which the single-phase AC power supply 4 in FIG. 2 outputs the upper voltage, when the element sw002 is off and the element sw012 is on, it passes through the free wheel diodes of the elements sw001 and sw002 to the upper DC capacitor c001. A charging current flows, and the charging current is fed back to the single-phase AC power supply 4 via the diode d011 and the element sw012.

  When the element sw002 is on and the element sw012 is off in the cycle in which the single-phase AC power supply 4 in FIG. 3 outputs the lower voltage, the upper DC capacitor c001 passes through the freewheeling diodes of the elements sw011 and sw012. The charging current flows to the single-phase AC power supply 4 via the diode d001 and the element sw002.

  In the period in which the single-phase AC power supply 4 in FIG. 4 outputs the upper voltage, when the element sw003 is on and the element sw013 is off, the lower DC capacitor c002 is charged via the element sw003 and the diode d002. A current flows, and the charging current is fed back to the single-phase AC power supply 4 via the freewheeling diodes of the elements sw013 and sw014.

  Although not shown, in order to charge the lower DC capacitor c002 in the period in which the single-phase AC power supply 4 outputs the lower voltage, the element sw003 is turned off and the element sw013 is turned on.

  As described above, in the present embodiment, it is possible to switch the upper DC capacitor c001 and the lower DC capacitor c002 to be charged by turning on / off a specific element during charging. In particular, in this embodiment, since the DC capacitor to be charged can be freely selected only by turning on the charging resistor 2 and turning on / off each element, the number of members for selecting the DC capacitor can be reduced, and the circuit configuration can be reduced. Simplify. In addition, since the direction of the charging current can be freely changed by turning on and off the element, it can be applied to an AC power supply as shown in the figure.

  As a result, according to the present embodiment, it is possible to charge a specific DC capacitor or not charge a specific DC capacitor. It is also possible to control so that the DC capacitor is not excessively charged by preventing a charging current from flowing into the DC capacitor having a desired voltage. Furthermore, it becomes possible to charge one DC capacitor to be charged up to the maximum value of the input voltage.

  This embodiment can be implemented in any number of levels and any number of phases in a diode clamp inverter.

2. Second Embodiment A second embodiment will be described with reference to FIG. The present embodiment includes three single-phase inverters 6 to 8, a charging resistor 9, a short-circuit switch 10, a single-phase AC power supply 11, and a reactor 12.

  Each single-phase inverter 6-8 has four elements each having a free-wheeling diode. That is, the single-phase inverter 6 includes elements sw101, sw102, sw111, and sw122, the single-phase inverter 7 includes elements sw121, sw122, sw131, and sw132, and the single-phase inverter 8 includes elements sw141, sw142, sw151, and sw152.

  Within each single-phase inverter 6-8, the first stage two elements sw101 and sw102, sw121 and sw122, sw141 and sw142 are connected in series, and similarly, the second stage elements sw111, sw122 and sw131 sw132, sw151 and sw152 are connected in series. The two first-stage elements connected in series and the two second-stage elements connected in series are connected in parallel. DC capacitors c101, c121, and c141 are connected in parallel to the two first-stage elements and the second-stage two elements connected in parallel.

  The charging resistor 9 is connected to a connection point between the elements sw102 and sw102 that serve as an input unit of the first single-phase inverter 6. A connection point between the elements sw111 and sw112 of the first single-phase inverter 6 is an output part of the first inverter 6 and is connected to a connection point between the elements sw121 and sw122 of the second single-phase inverter 7. The connection point between the elements sw131 and sw132 of the second single-phase inverter 7 is the output part of the second inverter 7, and is connected to the connection point between the elements sw141 and sw142 of the third single-phase inverter 8. An intermediate point between the elements sw151 and sw152 of the third single-phase inverter 8 is an output part of the single-phase inverter 8, and this part is connected to the single-phase AC power supply 11.

  In the present embodiment, when the DC capacitor voltage of the single-phase inverter 6 reaches a desired voltage, the devices sw101 and sw103 or sw102 and sw104 are turned on so that the DC capacitor c101 of the single-phase inverter 6 is not charged. It is possible to Similarly, the other single-phase inverters 7 and 8 can be configured not to charge the DC capacitors c121 and c141.

  The charging path before and after the DC capacitor voltage of the single-phase inverter 6 reaches a desired voltage will be described with reference to FIGS. 6 and 7.

  In FIG. 6, when the DC capacitor voltage of the single-phase inverters 6 to 8 does not reach the desired voltage, if all the elements of each single-phase inverter are turned off, the charging current is returned to each element of each single-phase inverter. All of the DC capacitors c101, c121, c141c are charged via the diode, and then returned to the single-phase AC power supply 11.

  In FIG. 7, when the DC capacitor voltage of the single-phase inverter 6 reaches a desired voltage, the element sw111 of the single-phase inverter 6 is turned on so that the charging current does not charge the DC capacitor c101 of the single-phase inverter 6. Return to the single-phase AC power supply 11. Thus, it is possible to charge the DC capacitors of the other single-phase inverters 7 and 8 without charging the DC capacitors of the single-phase inverter 6 that has reached a desired voltage by turning on a specific switching element. .

  Similarly to the above, according to the present embodiment, on / off of each element is appropriately switched even in the case of the other single-phase inverters 7 and 8 and when the voltage output from the single-phase AC power supply is in the reverse direction. Thus, the desired DC capacitor can be charged or stopped.

  In this embodiment, the number of single-phase inverters connected in series is set to 3, but the number of single-phase inverters connected in series is specified by turning on a specific switching element in the same manner as described above, regardless of the number of stages. It is possible not to charge the DC capacitor. The diode clamp type single-phase inverter shown in the first embodiment can also be used as the inverter circuit of the present embodiment.

3. Third Embodiment A third embodiment will be described with reference to FIGS. As shown in FIG. 8, this embodiment includes six single-phase inverters 13 to 18 and a three-phase AC power supply 25. Charging resistors 19 to 21, short-circuit switches 22 to 24, and reactors 26 to 28 are connected to each phase of the three-phase AC source power supply 25.

  Two of the six single-phase inverters 13 to 18 are connected to each phase of the three-phase AC power source 25. That is, two of the three single-phase inverters of the second embodiment shown in FIG. 5 are connected to each phase of the three-phase AC power supply 25. Therefore, the connection configuration of the four elements and DC capacitors provided in each single-phase inverter 13 to 18 is the same as that of the second embodiment, and the description thereof is omitted.

  In the present embodiment, as shown in FIG. 5, three single-phase inverters may be connected to each phase of the three-phase AC power supply 25. The diode clamp type single-phase inverter shown in the first embodiment can also be used as the inverter circuit of the present embodiment.

  In this embodiment, when the direction of the voltage of the three-phase AC power supply 25 is the direction of the arrow, if all the elements of the single-phase inverters 13 to 18 are turned off, the single-phase inverters 13 to 18 are provided. All DC capacitors can be charged.

  For example, by turning on the elements sw221, sw213, sw231, and sw253 so that the DC capacitors of the single-phase inverters 14 to 16 and 18 are not charged, the DC capacitors of the single-phase inverters 13 and 17 that are being charged are three-phase AC power supplies. It is possible to charge up to a maximum of 25 line voltages.

  On the other hand, even when the single-phase inverters to be charged in FIG. 9 are 15 and 18, the elements sw203, sw213, sw231, and sw243 are turned on so as not to charge the DC capacitors of the single-phase inverters 13, 14, 16, and 17. Similarly, it is possible to charge up to the maximum value of the line voltage of the three-phase AC power supply 25.

4). Fourth Embodiment A fourth embodiment will be described with reference to FIG. In the present embodiment, a three-phase inverter 29 having a DC capacitor c301 is connected to one end of an AC output of the power converter of each phase in the third embodiment shown in FIGS. The three-phase inverter 29 is formed by connecting a DC capacitor c301 in parallel to elements sw301 and sw302, sw303 and sw304, and sw305 and sw306 of each phase connected in series.

  In this embodiment, when the voltage of the DC capacitor c301 of the three-phase inverter 29 reaches a desired value, the DC capacitors of the three-phase inverter 29 are turned on by turning on the switching elements sw301, sw303, sw305 or sw302, sw304, sw306. It is possible not to charge c301.

  In this embodiment, a three-phase inverter is used. However, when the AC power supply is n-phase, the n-phase inverter is used to turn on a specific switching element in the same manner as described above, so that the DC capacitor of the n-phase inverter is used. It is possible not to charge. As the inverter circuit of this embodiment, the diode clamp type single-phase inverter shown in the first embodiment can also be used.

5. Fifth Embodiment A fifth embodiment will be described with reference to FIG. This embodiment includes eight DC choppers, a charging resistor 36, a short-circuit switch 37, and a DC power source 38. Four DC choppers 35a to 35d in the first stage are connected in series, and DC choppers 35a to 35d in the second stage are also connected in series. The first-stage DC choppers 34a to 34d connected in series and the second-stage DC choppers 35a to 35d are connected in parallel. A charging resistor 36, a short-circuit switch 37, and a DC power source 38 are provided in parallel with the first-stage and second-stage DC choppers.

  Each of the DC choppers 34a to 34d includes two elements sw401 and sw402 connected in series, and a DC capacitor c401 connected in parallel with these two elements. Similarly, each DC chopper 35a to 35d includes two elements sw411 and sw412 connected in series, and a DC capacitor c411 connected in parallel with these two elements.

  In this embodiment, when the voltage of the DC capacitor c401 or c411 of the DC chopper 34a or 35a reaches a desired value, the DC capacitor c401 or c411 of the DC chopper 34a or 35d is charged by turning on the element sw402 or sw412. It is possible not to do so. The same applies to the DC capacitors of the DC choppers 34b to 34d and 35b to 35d.

6). Sixth Embodiment A sixth embodiment will be described with reference to FIG. The present embodiment includes eight DC choppers, a charging resistor 36, a short-circuit switch 37, a single-phase AC power supply 39, and a reactor 40.

  Four DC choppers 35a to 35d in the first stage are connected in series, and DC choppers 35a to 35d in the second stage are also connected in series. The first-stage DC choppers 34a to 34d connected in series and the second-stage DC choppers 35a to 35d are connected in parallel. A charging resistor 36, a short-circuit switch 37, a single-phase AC power source 39, and a reactor 40 are connected to the connection point of the first-stage DC choppers 34b and 34c and the connection point of the second-stage DC choppers 35b and 35c. Yes.

  As in the fifth embodiment, each of the DC choppers 34a to 34d includes two elements sw401 and sw402 connected in series, and a DC capacitor c401 connected in parallel with these two elements. Similarly, each DC chopper 35a to 35d includes two elements sw411 and sw412 connected in series, and a DC capacitor c411 connected in parallel with these two elements.

  In the present embodiment, when the voltage of the DC capacitor c401 or c411 of the DC chopper 34a or 35a reaches a desired value, the DC capacitor of the DC chopper 34a or 35a is not charged by turning on the switching element sw402 or sw412. It is possible to do so. It should be noted that the DC capacitors of the DC choppers 34b to 34d and 35b to 35d can be controlled by appropriately turning on / off each element.

7). Other Embodiments (1) In a power conversion device in which the circuits described in the embodiments are combined, a specific DC capacitor is not charged by turning on a specific switching element, or a specific DC capacitor is It is possible to charge up to the maximum value of the input voltage.

(2) The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Diode clamp type full bridge inverter 2 ... Charging resistor 3 ... Charging resistor short circuit switch 4 ... Single phase alternating current power supply 5 ... Reactor
sw001 ~ 306 ... Switching element
d001 ~ 016 ... Diode
c001… Upper DC capacitor
c002 ... Lower DC capacitors 6-8 ... Single phase inverter 9 ... Charging resistor 10 ... Charging resistor short circuit switch 11 ... Single phase AC power supply 12 ... Reactor 13-18 ... Single phase inverter 19-21 ... Charging resistor 22-24 ... Short circuit Switch 25 ... Three-phase AC power supply 26-28 ... Reactor 29 ... Three-phase inverter 30 ... Charging resistor 31 ... Short-circuit switch 32 ... Three-phase AC power source 33 ... Reactors 34a-34d, 35a-35d ... DC chopper 36 ... Charging resistor 37 ... Short-circuit switch 38 ... DC power supply 39 ... Single-phase AC power supply 40 ... Reactor

Claims (9)

A plurality of switching elements are connected in a full bridge, and an inverter circuit having a DC capacitor to be charged connected to the plurality of switching elements, a power source for charging a DC capacitor provided in the inverter circuit, and the DC capacitor charging In a power converter having a charging resistor that sometimes limits current and a short-circuit switch connected in parallel with this charging resistor,
A plurality of stages of the inverter circuit are connected to the power source for charging,
The rated DC voltage and capacitor capacity of the DC capacitor to be charged in the inverter circuit of each stage are different from the rated DC voltage and capacitor capacity of other inverter circuits in at least some of the inverter circuits.
A power conversion device, wherein a plurality of switching elements provided in each inverter circuit are provided with a control device for independently turning on and off each switching element.   The power converter according to claim 1, wherein the inverter circuit is a diode clamp type single-phase inverter.   The power converter according to claim 1, wherein the inverter circuit is a single-phase inverter having four switching elements connected in a full bridge and a DC capacitor to be charged connected in parallel thereto. The plurality of inverter circuits are provided for a plurality of phases,
One end of the inverter circuit of each phase is connected to each phase of the charging power source having a plurality of phases via a charging resistor and a short circuit switch,
The other end of the inverter circuit of each phase is mutually connected, The power converter device in any one of Claim 1 thru | or 3 characterized by the above-mentioned. The other end of the inverter circuit of each phase is connected to each other via each phase of the inverter composed of a plurality of phases,
The inverter composed of a plurality of phases has a plurality of switching elements for each phase, and a DC capacitor to be charged connected in parallel with the plurality of switching elements,
5. The power conversion device according to claim 4, wherein each switching element of the inverter composed of the plurality of phases is turned on and off by the control device. A plurality of switching elements connected in series , a chopper circuit having a DC capacitor to be charged connected in parallel with the plurality of switching elements, a power source for charging a DC capacitor provided in the chopper circuit, and the DC In a power converter having a charging resistor that limits a current when charging a capacitor, and a short-circuit switch connected in parallel with the charging resistor,
A plurality of stages of the chopper circuit are connected to the power source for charging,
A plurality of switching elements provided in each chopper circuit are provided with a control device for independently turning on and off each switching element. A plurality of chopper circuits of the plurality of stages are connected in parallel;
The power converter according to claim 6, wherein a DC power supply for charging, a charging resistor, and a short-circuit switch are connected in parallel to the plurality of chopper circuits connected in parallel. A plurality of chopper circuits of the plurality of stages are connected in parallel;
The power converter according to claim 6, wherein a single-phase AC power source for charging, a charging resistor, and a short-circuit switch are connected in parallel to the plurality of chopper circuits connected in parallel.   The rated DC voltage and capacitor capacity of the DC capacitor to be charged in each stage of the chopper circuit are the same as or different from the rated DC voltage and capacitor capacity of other chopper circuits in at least some chopper circuits. The power conversion device according to any one of claims 6 to 8.

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