JP2011130517A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein, a scale-up and a cost increase occur in a power converter when a regenerative power consumption means or power supply regenerating means from an electric motor is provided for each DC power supply in a multi-level inverter. <P>SOLUTION: Provided is the power converter in which a power consumption means or power regenerating means is connected to only between potentials equivalent to an intermediate potential of a DC voltage, and in which an interlock is formed on a switching of the multi-level inverter so that regenerative power from the electric motor is charged only to a capacitor connected between the potentials to which the power consumption means or power regenerating means is connected in decelerating the electric motor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power conversion technique for converting alternating current into a plurality of direct currents and converting the plurality of direct currents into alternating current by a multilevel inverter, and more particularly to a technical field of driving an alternating current motor by a multilevel inverter.

  A three-level inverter is known as an inverter that converts power from direct current to alternating current having a plurality of voltage levels. A multi-level inverter is known as an inverter having a voltage level exceeding three levels.

  FIG. 4 shows a configuration diagram of one phase of the four-level inverter described in Patent Document 1. Between the DC positive electrode P and the negative electrode N, a series circuit of reverse conduction switches Q1a to Q4a configured by connecting a controllable device such as IGBT and a diode in reverse parallel and a series circuit of capacitors C1a to C3a are connected in parallel. Is done. A reverse conduction switch Q5a is connected between a connection point between the reverse conduction switches Q1a and Q2a and a connection point (potential V2a) between the capacitors C1a and C2a, and a connection point between the reverse conduction switches Q3a and Q4a and the capacitor C2a. A reverse conduction switch Q6a is connected between the connection point to C3a (potential V2a), and the connection point between the reverse conduction switches Q2a and Q3a is an AC output U. By controlling on / off of the reverse conduction switches Q1a to Q6a, the output potential of the inverter can output a voltage having four levels V1a, V2a, V3a, and V4a in a half cycle period in descending order of potential.

  FIG. 5 is a circuit configuration diagram for one phase of an inverter circuit that is theoretically equivalent to the 5-level inverter described in Patent Document 2. In FIG. In the inverter of this configuration, an AC voltage having five levels of potentials V1b to V5b can be output with respect to the above-described four-level inverter, so that an AC voltage with less harmonics can be obtained and the capacity can be easily increased. There is.

JP 2006-87257 A JP 2007-31451 A

  A marine electric propulsion device or the like has a feature that the braking power required to operate the motor as a generator to decelerate the electric power required to drive the motor may be about 1/10. Therefore, when an electric motor is driven using an inverter, a DC voltage is generally generated from an AC power source using a diode rectifier, and braking power is consumed by a resistor using a resistance chopper connected to a DC intermediate circuit during braking. There are many. A circuit configuration example of the resistance chopper is shown in FIG. A power semiconductor switch Q (for example, IGBT), a resistor R, and a diode D connected in parallel to the resistor R are provided.

  By the way, ship electric propulsion devices have been put to practical use up to a capacity exceeding 10 MW, and a multi-level inverter that can easily increase the voltage and capacity is considered to be one of power converters suitable for ship electric propulsion. In addition, the multi-level inverter has a drawback that the voltage of the capacitor connected between a plurality of potentials tends to be unbalanced (see, for example, Japanese Patent Laid-Open No. 11-332252), but if a diode rectifier is connected to each capacitor, The above problems can be solved because each capacitor voltage is clamped to the output voltage of the diode rectifier.

  A method of connecting the resistance chopper between potentials having the largest voltage difference of the DC circuit, that is, between the positive electrode P and the negative electrode N in FIG. 4 or FIG. However, this method has a problem that the DC voltage rises during braking and the diode rectifier is opened, making it difficult to balance the capacitor voltages. In order to solve this problem, a method of connecting a resistance chopper between each DC potential can be considered. However, this method has a problem that the number of parts of the resistance chopper increases and the apparatus becomes large and expensive. .

  The present invention has been devised to solve the above-mentioned problem. A resistance chopper is provided only in a DC circuit between specific potentials to reduce the number of parts, and a regenerative power from a motor is provided to a capacitor to which a resistance chopper is not connected. The purpose is to avoid the problem that the capacitor voltage becomes overvoltage by providing an interlock that controls the inverter so that is not charged.

  In order to solve the above-mentioned problem, in the first invention, one or a plurality of transformers whose secondary windings are insulated from each other, and an AC input are connected to one of the secondary windings, Three or more odd number of diode rectifiers in which each DC output is connected in series, a capacitor connected between each DC output of the diode rectifier, and a plurality of voltages connected to the DC output of the odd number of diode rectifiers In a power conversion device including a multi-level inverter that generates alternating current having a level, an even number of direct current potentials generated by the odd number of diode rectifiers are first, second, ..., when referred to as the 2n-th DC potential, power consumption means for consuming power only between the n-th and (n + 1) -th DC potential, or power regeneration means for regenerating power to an AC power source It is characterized by providing.

  According to a second aspect of the present invention, in the first aspect, the load driven by the multilevel inverter is an AC motor, and the multilevel inverter includes first to fourth controllable devices and diodes connected in reverse parallel. A reverse conduction switch is sequentially connected in series between a positive electrode and a negative electrode, a connection point between the second reverse conduction switch and the third reverse conduction switch is an AC output terminal, and the first reverse conduction switch A fifth reverse conduction switch between a connection point between the second reverse conduction switch and the second DC potential; a connection point between the third reverse conduction switch and the fourth reverse conduction switch; A four-level inverter in which a plurality of one-phase switch circuits each connected with a sixth reverse conduction switch between the third DC potential and connected in parallel, when the AC motor is decelerated, Off at least the first and the fourth reverse conducting switch phase partial switching circuit, characterized in that on the reverse conducting switch of the fifth and the sixth.

  In the third invention, one or a plurality of transformers whose secondary windings are insulated from each other, an AC input is connected to one of the secondary windings, and each DC output is connected in series 4 A plurality of even-numbered diode rectifiers, capacitors connected between the respective DC outputs of the diode rectifiers, and a multi-level that is connected to the DC outputs of the even-numbered diode rectifiers and generates an alternating current having a plurality of voltage levels. In the power conversion device including the inverter, the odd number of DC potentials generated by the even number of diode rectifiers are the first, second,..., 2n + 1 DC potentials in order from the highest potential. Power consumption means for consuming power only between the DC potentials between n and n + 1 and between n + 1 and n + 2, or power regeneration for regenerating power to an AC power source Characterized in that it comprises a stage.

  In a fourth aspect based on the third aspect, the load driven by the multilevel inverter is an AC motor, and the multilevel inverter includes first to sixth controllable devices and diodes connected in antiparallel. Are connected in series between a positive electrode and a negative electrode, and a connection point between the third reverse conduction switch and the fourth reverse conduction switch is an AC output terminal, and the first reverse conduction switch And a connection point between the second reverse conduction switch and the second reverse conduction switch, and a connection point between the second reverse conduction switch and the third reverse conduction switch. And an eighth reverse conduction switch between the third and the third DC potential, and an eighth reverse conduction switch between the fourth DC conduction point and the fifth reverse conduction switch and the third DC potential. 9 reverse conduction switch, the fifth Five levels of a plurality of one-phase switch circuits connected in parallel to each of the tenth reverse conduction switches between the connection point between the reverse conduction switch and the sixth reverse conduction switch and the fourth DC potential When the AC motor is decelerated, the inverter turns off at least the first and sixth reverse conduction switches and turns on the seventh and tenth reverse conduction switches of the one-phase switch circuit. It is characterized by that.

  In a fifth invention, the power consuming means in any one of the first to fourth inventions comprises a semiconductor switch, a resistor connected in series with the semiconductor switch, and a diode connected in parallel to the resistor. It is characterized by.

  In a sixth invention, the power regeneration means in any one of the first to fourth inventions comprises: an inverter that converts direct current into alternating current; and a transformer primary winding connected to the alternating current output of the inverter. And the secondary winding of the transformer is connected to an AC power source.

  In a seventh invention, the power regeneration means in any one of the first to fourth inventions connects a semiconductor switch in reverse parallel to a capacitor that absorbs regenerative power and a diode of a rectifier in which a DC output is connected in parallel. It is characterized by that.

The present invention relates to a power converter including a plurality of diode rectifiers that generate DC voltages having a plurality of DC potentials and a multi-level inverter that receives the DC voltages of the diode rectifiers. A power consuming means or a power regeneration means is connected only between them. In addition, when the motor driven by the multilevel inverter is decelerated by generating braking torque, the regenerative power from the motor is charged only to the capacitor connected between the electric power consumption means or the potential connected to the power regeneration means. As described above, an interlock is provided in the switching of the multilevel inverter.
As a result, the capacitor voltage can be clamped to a predetermined voltage regardless of the drive mode or braking mode with a small number of power absorption means or power regeneration means, so that the power conversion device can be protected from overvoltage, and more compact and inexpensive power conversion is possible. Equipment can be provided.

It is a circuit block diagram which shows the 1st Example of this invention. It is a circuit block diagram which shows the 2nd Example of this invention. It is a circuit block diagram which shows the 3rd Example of this invention. It is a circuit block diagram which shows the 4th Example of this invention. A circuit example for one phase of a conventional four-level inverter is shown. A circuit example for one phase of a conventional 5-level inverter is shown. It is a circuit diagram which shows an example of a power consumption means.

  An essential point of the present invention is an intermediate potential of a DC voltage in a power converter including a plurality of diode rectifiers that generate DC voltages having a plurality of DC potentials and a multi-level inverter that receives the DC voltages of the diode rectifiers. When power consumption means or power regeneration means is connected only between the corresponding potentials and the motor driven by the multi-level inverter is decelerated by generating braking torque, the potential between the power consumption means or power regeneration means is connected. An interlock is provided in the switching of the multilevel inverter so that only the connected capacitor is charged with regenerative power from the motor.

FIG. 1 shows a first embodiment of the present invention. This is a 4-level inverter configuration that creates waveforms with four potentials during a half cycle period of AC output.
The converter unit that converts alternating current to direct current includes a transformer 1a including secondary windings that output three sets of three-phase voltages insulated from an alternating current power source, and these secondary windings are connected to an alternating current input terminal, respectively. The three diode rectifiers 21a to 23a whose DC outputs are connected in series and the capacitors C1a to C3a connected between the DC output terminals of the diode rectifiers. With this configuration, DC potentials V1a to V4a are generated. A capacitor C1a is connected between the DC potentials V1a and V2a, a capacitor C2a is connected between the DC potentials V2a and V3a, and a capacitor C3a is connected between the DC potentials V3a and V4a. Here, instead of the transformer 1a, three two-winding (primary and secondary) transformers may be used.

  The multi-level (four-level) inverter unit that converts direct current to alternating current is composed of a phase switch circuit 31a for one phase composed of reverse conducting switches Q1a to Q6a composed of controllable devices (IGBTs) in which diodes are connected in antiparallel. The three-phase phase switch circuits 31a to 33a constitute a three-phase multilevel inverter. A series circuit of reverse conduction switches Q1a to Q4a is provided between the DC potentials V1a and V4a, a reverse conduction switch Q5a is provided between the connection point of the reverse conduction switches Q1a and Q2a and the DC potential V2a, and the reverse conduction switches Q3a and Q4a are provided. The reverse conduction switch Q6a is connected between the connection point between the first terminal and the DC potential V3a. A connection point between the reverse conduction switches Q2a and Q3a is an AC output terminal. The AC motor 4a is connected to the AC output terminals of the phase switch circuits 31a to 33a of the respective phases. In addition, a resistance chopper 5a for regenerating regenerative power from the electric motor is connected in parallel with the capacitor C2a.

  When the AC motor 4a generates braking torque, the motor operates as a generator, so that regenerative power from the AC motor 4a flows into the DC circuit. In this embodiment, the reverse conduction switches Q1a and Q4a are turned off and the reverse conduction switches Q5a and Q6a are turned on to absorb the regenerative power only by the capacitor C2a. The absorbed power is consumed as heat by the resistance of the resistance chopper 5a connected only between the DC potentials V2a and V3a corresponding to the intermediate potential of the DC circuit so that the voltage of the capacitor C2a becomes a predetermined value.

  Here, the current acting on the regenerative power from the motor is the AC motor 4a → the diode of the reverse conduction switch Q2a → the reverse conduction switch Q5a → the root of the capacitor C2a, or the capacitor C2a → the reverse conduction switch Q6a → the diode of the reverse conduction switch Q3a. → Flows along the route of the AC motor 4a. As described above, the regenerative power from the electric motor is charged only in the capacitor C2a and is consumed by the resistance chopper 5a connected to the capacitor C2a. In order to control the output potential, either the reverse conduction switch Q2a or Q3a is turned on during the above operation.

  FIG. 2 shows a second embodiment of the present invention. Instead of the resistance chopper 5a in the first embodiment, a power regenerator 6 constructed by bridge-connecting reverse conduction switches is used, and the regenerative power from the motor 4a is DC-AC converted by the power regenerator 6, and the transformer 11 It is the structure which regenerates electric power to AC power supply via. Other configurations and operations are the same as those in the first embodiment.

  FIG. 3 shows a third embodiment of the present invention. The difference between the first embodiment and the second embodiment is that instead of the resistance chopper 5a in the first embodiment and the power regenerator 6 and the transformer 11 in the second embodiment, a capacitor C2a that absorbs regenerative power and a DC output are connected in parallel. The semiconductor switch element (IGBT) is connected in antiparallel with each diode of the rectifier 22a. The circuit configuration of the bridge circuit 6a is the same as that of the power regenerator 6 configured by bridge-connecting reverse conduction switches. This circuit DC-AC converts the regenerative power from the motor 4a absorbed by the capacitor C2a, and regenerates power to the AC power source via the transformer 1a. Here, since the bridge circuit 6a operates as a rectifier when driving an electric motor and operates as an inverter when power is regenerated, a high-speed diode that can be used in an inverter circuit is required as the rectifier diode. Further, as the capacitance of the semiconductor switch element (IGBT), an element having a small capacity that only processes regenerative power can be applied.

FIG. 4 shows a fourth embodiment of the present invention. FIG. 4 shows a configuration of a five-level inverter that generates waveforms having five potentials during a half cycle period of AC output.
The converter unit for converting alternating current to direct current includes a transformer 1b including secondary windings that output four sets of three-phase voltages insulated from an alternating current power source, and these secondary windings are connected to an alternating current input terminal, respectively. The four diode rectifiers 21b to 24b whose DC outputs are connected in series and the capacitors C1b to C4b connected between the DC output terminals of the diode rectifiers. With this configuration, DC potentials V1b to V5b are generated. The capacitor C1b is between the DC potentials V1b and V2b, the capacitor C2b is between the DC potentials V2b and V3b, the capacitor C3b is between the DC potentials V3b and V4b, and between the DC potentials V4b and V5b. Are respectively connected to capacitors C4b. Here, instead of the transformer 1b, four two-winding (primary and secondary) transformers may be used.

  The multi-level (5-level) inverter unit that converts direct current into alternating current is composed of a phase switch circuit 31b for one phase composed of a reverse conducting switch of Q1b to Q10b composed of a controllable device (IGBT) having diodes connected in antiparallel. The three-phase phase switch circuits 31b to 33b constitute a three-phase multilevel inverter. A series circuit of reverse conduction switches Q1b to Q6b is provided between the DC potentials V1b and V5b, a reverse conduction switch Q7b is provided between the connection point of the reverse conduction switches Q1b and Q2b and the DC potential V2b, and reverse conduction switches Q2b and Q3b are provided. The reverse conduction switch Q8b is connected between the connection point between the connection point and the DC potential V3b, the reverse conduction switch Q9b is connected between the connection point between the connection point between the reverse conduction switches Q4b and Q5b and the DC potential V3b, and the reverse conduction switch Q5b and Q6b. A reverse conduction switch Q10b is connected between the connection point and the DC potential V4b. A connection point between the reverse conduction switches Q3b and Q4b is an AC output terminal. The AC motor 4b is connected to the AC output terminals of the phase switch circuits 31b to 33b of the respective phases. A resistor chopper 5b1 is connected in parallel with the capacitor C2b, and a resistor chopper 5b2 is connected in parallel with the capacitor C3b.

  Here, when AC motor 4b generates braking torque, at least reverse conduction switches Q1b and Q6b are turned off, and reverse conduction switches Q7b and Q10b are turned on. At this time, the current acting on the regenerative power from the AC motor 4b is: AC motor 4b → reverse conduction switch Q3b diode → reverse conduction switch Q2b diode → reverse conduction switch Q7b → route through the capacitor C2 or capacitor C3b → reverse. It flows in a route passing through the conduction switch Q10b → the diode of the reverse conduction switch Q5b → the diode of the reverse conduction switch Q4b → the AC motor 4b.

As described above, the regenerative power from the AC motor 4b motor is charged only in the capacitor C2b or C3b, and the regenerative power is consumed by the resistor chopper 5b1 connected in parallel to the capacitor C2b and the resistor chopper 5b2 connected in parallel to the capacitor C3b. The
In order to control the output potential, either the reverse conduction switches Q2b and Q3b or the reverse conduction switches Q4b and Q5b are turned on during the above operation. Further, instead of the resistance chopper as in the above-described embodiment, power may be regenerated in the AC power source using the power regenerator 6 shown in FIG.

In this embodiment, the resistance choppers 5b1 and 5b2 are connected only between V2b and V3b corresponding to the intermediate potential and between V3b and V4b. However, even if the resistance chopper is connected only between the DC potentials V2b and V4b. Good.
Further, similarly to the second embodiment, instead of the resistance choppers 5b1 and 5b2, a configuration in which the regenerative circuit composed of the power regenerator 6 and the transformer 11 shown in the second embodiment is connected, respectively, as in the third embodiment. The same effect can be obtained by connecting a semiconductor switch element (IGBT) in reverse parallel to the rectifier diodes of the diode rectifiers 22b and 23b.

  As patent documents similar to the present invention, Japanese Patent Laid-Open Nos. 2001-238455 and 2005-33903 are known. In these patent documents, a plurality of single-phase inverters are connected in series to form a multiple inverter. At least three resistance choppers corresponding to three phases of output are required, and the regenerative power from the AC motor is specified. The control method of the inverter that is made to flow to the location is different.

  The present invention is a technology related to the consumption of regenerative power or power supply regeneration of a multilevel inverter, and can be applied to a high-voltage power supply with low regenerative power as well as an electric propulsion device for ships.

DESCRIPTION OF SYMBOLS 1a, 1b, 11 ... Transformer 4a, 4b ... AC motor 6 ... Electric power regenerator 6a ... Bridge circuit 21a-23a, 21b-24b ... Diode rectifier Q1a-Q6a, Q1b-Q10b ... Reverse conduction switches 31a to 33a, 31b to 33b ... Phase switch circuits 5a, 5b1, 5b2 ... Resistance choppers C1a to C3a, C1b to C4b ... Capacitors

Claims (7)

One or a plurality of transformers whose secondary windings are insulated from each other, and three or more odd-numbered diodes in which an AC input is connected to one of the secondary windings and each DC output is connected in series Electric power composed of a rectifier, a capacitor connected between the respective DC outputs of the diode rectifier, and a multi-level inverter connected to the DC outputs of the odd number of diode rectifiers to generate an alternating current having a plurality of voltage levels In the conversion device,
When the even number of DC potentials generated by the odd number of diode rectifiers are called the first, second,..., 2n DC potentials in order from the highest potential, the nth and n + 1th DC potentials are called. A power conversion device comprising power consumption means for consuming electric power only between stations or power regeneration means for regenerating power to an AC power source. The load driven by the multi-level inverter is an AC motor, and the multi-level inverter sequentially includes first to fourth reverse conducting switches in which a controllable device and a diode are connected in reverse parallel between a positive electrode and a negative electrode. Connected in series, a connection point between the second reverse conduction switch and the third reverse conduction switch as an AC output terminal, and a connection point between the first reverse conduction switch and the second reverse conduction switch A fifth reverse conduction switch is provided between the second direct current potential and a sixth reverse conduction switch between the third reverse conduction switch and the fourth reverse conduction switch and the third direct current potential. A four-level inverter in which a plurality of one-phase switch circuits connected in parallel are connected in parallel,
When decelerating the AC motor, at least the first and fourth reverse conduction switches of the one-phase switch circuit are turned off, and the fifth and sixth reverse conduction switches are turned on. The power conversion device according to claim 1. One or a plurality of transformers whose secondary windings are insulated from each other, and an even number of four or more diodes in which an AC input is connected to one of the secondary windings and each DC output is connected in series Power composed of a rectifier, a capacitor connected between the respective DC outputs of the diode rectifier, and a multi-level inverter connected to the DC outputs of the even number of diode rectifiers to generate an alternating current having a plurality of voltage levels In the conversion device,
When the odd number of DC potentials generated by the even number of diode rectifiers are referred to as first, second,..., 2n + 1 DC potentials in order from the highest potential, between the nth and n + 1th and A power conversion device comprising power consumption means for consuming power only between DC potentials between the (n + 1) th and (n + 2) th, or power regeneration means for regenerating power to an AC power supply. The load driven by the multi-level inverter is an AC motor, and the multi-level inverter has a first to sixth reverse conduction switch in which a controllable device and a diode are connected in reverse parallel between a positive electrode and a negative electrode. Connected sequentially in series, a connection point between the third reverse conduction switch and the fourth reverse conduction switch is used as an AC output terminal, and a connection point between the first reverse conduction switch and the second reverse conduction switch A seventh reverse conduction switch between the second direct current potential and the third direct current potential between the connection point of the second reverse conduction switch and the third reverse conduction switch and the third direct current potential. 8 reverse conduction switch, the ninth reverse conduction switch between the fourth reverse conduction switch and the fifth reverse conduction switch and the third DC potential between the fifth reverse conduction switch and the fifth reverse conduction switch. Conduction switch and the sixth reverse conduction The tenth reverse conducting switch between the fourth DC voltage of the connection point between the switches, one phase switching circuit connected respectively to a five-level inverter in which a plurality are connected in parallel,
When decelerating the AC motor, at least the first and sixth reverse conduction switches of the one-phase switch circuit are turned off, and the seventh and tenth reverse conduction switches are turned on. The power conversion device according to claim 3.   The said power consumption means is equipped with the semiconductor switch, the resistance connected in series with the said semiconductor switch, and the diode connected in parallel with the said resistance, The any one of Claims 1-4 characterized by the above-mentioned. The power converter described.   The power regeneration means comprises an inverter for converting direct current to alternating current, and a transformer primary winding connected to the alternating current output of the inverter, and connecting the secondary winding of the transformer to an alternating current power source. The power converter according to any one of claims 1 to 4, wherein The said power regeneration means connects a semiconductor switch in antiparallel with the diode of the rectifier by which the capacitor | condenser which absorbed regenerative power, and DC output were connected in parallel, The switch of Claim 1 characterized by the above-mentioned. Power conversion device.

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