Controller for power converter

• US 6,151,227 A
• Filed: 08/04/1998
• Issued: 11/21/2000
• Est. Priority Date: 08/04/1997
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Miguchi, Yasuhiko, Mizutani, Mami
• Primary Examiner(s): Han, Jessica
• Application Number:
  US09/128,660
• Time in Patent Office: 840 Days
• Field of Search: 363/16, 363/17, 363/27, 363/28, 363/65, 363/71, 363/72, 363/95, 363/96, 363/98, 363/132, 363/136, 363/41, 363/42, 363/43
• US Class Current: 363/41
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters

Abstract

The controller for a power converter of the present invention:

calculates the range number in which the voltage command vector for a multi-level converter is present;

rotates the voltage command vector through a specified angle;

performs coordinate transformation of that vector to a vector in an oblique coordinate system which takes the vector in the a axis direction and a vector which has been rotated through a specified angle anti-clockwise from the a axis as two unit vectors;

splits the converter output-enabled portion of the vector diagram of the -30 degrees +30 degrees range of the spatial vector diagram in which output vector is positioned, which has undergone oblique coordinate transformation, into square-shape patterns so that the outputs vector is positioned in the upper left/the lower right/both the lower left and upper right of each square-shape pattern;

splits any square-shape pattern which holds the output vector in both its lower left and its upper right into two triangular domains by a segment which joins the upper left vertex and the lower right vertex;

judges in which square-shape pattern/triangular domain in the domain-split oblique coordinate system diagram the voltage command vector which has undergone oblique coordinate transformation is present; and

selects, rotates through a specified angle and calculates the output vector which corresponds to that domain.

Claims

1. A controller for a power converter comprising:

n converters which convert DC power to AC power, n being an integer greater than 1, each of which includes bridge-connecting self-extinguishing type switching elements, and feedback diodes which are respectively connected to each said self-extinguishing type switching element,

n transformers for respectively inputting the outputs of said n number converters, and connecting with an AC load by connecting in series the secondary sides of said n number transformers, and being provided with;

means for providing a voltage command vector of an AC output voltage of said power converter;

means for providing all output vectors of said AC output voltages which said power converter can generate;

output vector selection means for selecting said output vectors according to said voltage command vector; and

control means for controlling conductive states of said self-extinguishing type switching elements according to output vectors selected by said output vector selection means,

wherein a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees to 150 degrees, 150 degrees to 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges,

said output vector selection means comprising;

(a) a calculate means for calculating said range number in which said voltage command vector is present;

(b) a rotate means for rotating said voltage command vector through a specified angle;

(c) a coordinate convert means for performing coordinate transformation of said rotated voltage command vector to a vector in an oblique coordinate system which takes a first vector in the -30 degrees direction and a second vector in the 30 degrees direction of the rectangular coordinate system as two unit vectors;

(d) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors of said -30 degrees to +30 degrees range, of a spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting any square-shape pattern which holds said output vector in both said lower left and said upper right, into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(e) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in either said square-shape pattern domain or said triangular domain in said oblique coordinate system diagram which has been split into said domains; and

(f) a select means for selecting said output vector corresponding to said square-shape pattern domain or said triangular domain according to results of said judgement; and

(g) a calculation means for calculating an output vector which is rotated through a specified angle as said selected output vector.

2. A controller for a power converter comprising:

n converters which convert DC power to AC power, n being an integer greater than 1, each of which includes bridge-connecting self-extinguishing type switching elements, and feedback diodes which are respectively connected to each said self-extinguishing type switching element,

n transformers for respectively inputting the outputs of said n number converters, and connecting with an AC load by connecting in series the secondary sides of said n number transformers, and being provided with;

means for providing a voltage command vector of an AC output voltage of the said power converter;

means for providing all output vectors of said AC output voltages which the said power converter can generate;

output vector selection means for selecting said output vectors according to said voltage command vector; and

control means for controlling conductive states of said self-extinguishing type switching elements according to output vectors selected by the said output vector selection means,

wherein a spatial vector diagram is split into 6 range;

30 degrees, 30 degrees to 90 degrees, 90 degrees to 150 degrees, 150 degrees to 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges,

said output vector selection means comprising;

(a) a calculate means for calculating said range number in which said voltage commend vector is present;

(b) a rotate means for rotating said voltage command vector through a specified angle;

(c) a coordinate convert means for performing coordinate transformation of said rotated voltage command vector to a vector in an oblique coordinate system which takes a first vector in the -30 degrees direction and a second vector in the 30 degrees direction of the rectangular coordinate system as two unit vectors;

(d) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors, of said -30 degrees to +30 degrees range of a spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting each square-shape pattern into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(e) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in a triangular domain in said oblique coordinate system diagram which has been split into said domains;

(f) a select means for selecting said output vector corresponding to said triangular domain according to results of said judgement; and

(g) a calculation means for calculating an output vector which is rotated through a specified angle as said selected output vector.

3. A controller for a power converter comprising:

n converters which convert DC power to AC power, n being an integer greater than 1, each of which includes bridge-connecting self-extinguishing type switching elements, and feedback diodes which are respectively connected to each said self-extinguishing type switching element,

n transformers for respectively inputting the outputs of said n number converters, and connecting with an AC load by connecting in series the secondary sides of said n number transformers, and being provided with;

means for providing a voltage command vector of an AC output voltage of the said power converter;

means for providing all output vectors of said AC output voltages which the said power converter can generate;

output vector selection means for selecting said output vectors according to said voltage command vector; and

control means for controlling conductive states of said self-extinguishing type switching elements according to output vectors selected by said output vector selection means,

wherein a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees to 150 degrees, 150 degrees to 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges,

said output vector selection means comprising;

(a) a calculate means for calculating said range number in which said voltage command vector is present;

(b) a coordinate convert means for performing coordinate transformation of said command vector to a vector in an oblique coordinate system which takes a vector in a first specified angular direction and a vector in a second specified angular direction as two unit vectors;

(c) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors, of 60-degree range in which said voltage command vector is present within a spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting each square-shape pattern which holds said output vector in both said lower left and said upper right into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(d) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in either said square-shape pattern domain or said triangular domain in said oblique coordinate system diagram which has been split into said domains; and

(e) a select means for selecting said output vector corresponding to said square-shape domain or a triangular domain according to results of said judgement.

4. A controller for a power converter comprising:

n converters which convert DC power to AC power, n being an integer greater than 1, each of which includes bridge-connecting self-extinguishing type switching elements, and feedback diodes which are respectively connected to each said self-extinguishing type switching element,

n transformers for respectively inputting the outputs of said n number converters, and connecting with an AC load by connecting in series the secondary sides of said n number transformers, and being provided with;

means for providing a voltage command vector of an AC output voltage of the said power converter;

means for providing all output vectors of said AC output voltages which the said power converter can generate;

output vector selection means for selecting said output vectors according to said voltage command vector; and

control means for controlling conductive states of said self-extinguishing type switching elements according to output vectors selected by the said output vector selection means,

wherein a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees to 150 degrees, 150 degrees to 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges,

said output vector selection means comprising;

(a) a calculate means for calculating said range number in which said voltage command vector is present;

(b) a coordinate convert means for performing coordinate transformation of said command vector to a vector in an oblique coordinate system which takes a vector in a first specified angular direction and a vector in a second specified angular direction as two unit vectors;

(c) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors, of the 60-degree range in which said voltage command vector is present within a spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting each square-shape pattern into two triangular domains by a segment which joins a upper left vertex and a lower right vertex;

(d) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in any triangular domain in said oblique coordinate system diagram which has been split into the said domains; and

(e) a select means for selecting said output vector corresponding to said triangular domain according to results of said judgement.

5. A controller for a power converter comprising a split power source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units,

3 sets of series circuits, composed by connecting in series (2×

n) self-extinguishing type switching elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, and having converted voltage output terminals which output voltages which are converted from the voltage of said DC voltage source from between a nth self-extinguishing type switching element and a (n+1)th self-extinguishing type switching element from a positive side of said DC voltage source, and connecting said converted voltage output terminals to an AC load, and being provided with;

means for providing a voltage command vector of an AC output voltage of said power converter;

a device which provides all the output vectors of the AC output voltages which the said power converter can generate;

output vector selection means for selecting said output vectors according to said voltage command vector; and

control means for controlling conductive states of said self-extinguishing type switching elements according to said output vectors selected by said output vector selection means,

wherein a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees to 150 degrees, 150 degrees to 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges, said output vector selection means comprising;

(a) a calculate means for calculating said range number in which said voltage command vector is present;

(b) a rotate means for rotating said voltage command vector through a specified angle;

(c) a coordinate convert means for performing coordinate transformation of said rotated voltage command vector to a vector in an oblique coordinate system which takes a first vector in the -30 degrees direction and a second vector in the 30 degrees direction of the rectangular coordinate system as two unit vectors;

(d) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors, of -30 degrees to +30 degrees range of said spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting any square-shape pattern which holds said output vector in both said lower left and said upper right, into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(e) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in either said square-shape pattern domain or said triangular domain in said oblique coordinate system diagram which has been split into said domains;

(f) a select means for selecting said output vector corresponding to said square-shape pattern domain or said triangular domain according to results of said judgement; and

(g) a calculation means for calculating an output vector which is rotated through a specified angle as said selected output vector.

6. A controller for a power converter comprising a split power source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units,

3 sets of series circuits, composed by connecting in series (2×

n) self-extinguishing type switching elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, and having converted voltage output terminals which output voltages which are converted from the voltage of said DC voltage source from between a nth self-extinguishing type switching element and a (n+1)th self-extinguishing type switching element from a positive side of said DC voltage source, and connecting said converted voltage output terminals to an AC load, and being provided with;

means for providing a voltage command vector of an AC output voltage of said power converter;

a rotate means for providing all output vectors of said AC output voltages which said power converter can generate;

output vector selection means for selecting said output vectors according to said voltage command vector; and

control means for controlling conductive states of said self-extinguishing type switching elements according to said output vectors selected by said output vector selection device,

wherein a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees 20 to 150 degrees, 150 degrees 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges, said output vector selection means comprising;

(a) a means for calculating said range number in which said voltage command vector is present;

(b) a rotate means for rotating said voltage command vector through a specified angle;

(c) a coordinate convert means for performing coordinate transformation of said rotated voltage command vector to a vector in an oblique coordinate system which takes a first vector in the -30 degrees direction and a second vector in the 30 degrees direction of the rectangular coordinate system as two unit vectors;

(d) a split means for splitting a converter output-enabled portion of vector diagram, which has undergone oblique transformation, using said unit vectors, of the -30 degrees--+30 degrees range of said spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting each square-shape pattern into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(e) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in said triangular domain in said oblique coordinate system diagram which has been split into said domains; and

(f) a calculation means for calculating an output vector which is rotated through a specified angle as said selected output vector.

7. A controller for a power converter comprising a split power source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units,

3 sets of series circuits, composed by connecting in series (2×

n) self-extinguishing typeswitching elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, and having converted voltage output terminals which output voltages which are converted from the voltage of said DC voltage source from between a nth self-extinguishing type switching element and a (n+1)th self-extinguishing type switching element from a positive side of said DC voltage source, and connecting said converted voltage output terminals to an AC load, and being provided with;

a means for providing a voltage command vector of an AC output voltage of said power converter;

a device which provides all the output vectors of the AC output voltages which the said power converter can generate; and

an output vector selection means for selecting said output vectors according to said voltage command vector;

a control means for controlling conductive states of said self-extinguishing type switching elements according to said output vectors selected by said output vector selection means,

wherein a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees 20 to 150 degrees, 150 degrees 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges, said output vector selection means comprising;

said output vector selection means comprising;

(a) a means for calculating said range number in 5 which said voltage command vector is present;

(b) a coordinate convert means for performing coordinate transformation of said command vector to a vector in an oblique coordinate system which takes a vector in a first specified angular direction and a vector in a second specified angular direction as two unit vectors;

(c) a split means for splitting a converter output enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors, off 60-degree range in which said voltage command vector is present within a spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting each square-shape pattern which holds said output vector in both said lower left and said upper right into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(d) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in either said square-shape pattern domain or said triangular domain in said oblique coordinate system diagram which has been split into the said domains; and

(e) a select means for selecting said output vector corresponding to said square-shape pattern domain or a triangular domain according to results off said judgement.

8. A controller for a power converter comprising a split power source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units,

3 sets of series circuits, composed by connecting in series (2×

n) self-extinguishing type switching elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, and having converted voltage output terminals which output voltages which are converged from the voltage of said DC voltage source from between a nth self-extinguishing type switching element and a (n+1)th self-extinguishing type switching element from a positive side of said DC voltage source, and connecting said converted voltage output terminals to an AC load, and being provided with;

a means for providing a voltage command vector of an AC output voltage of said power converter;

a device which provides all the output vectors of the AC output voltages which the said power converter can generate;

an output vector selection means for selecting said output vectors according to said voltage command vector; and

a control means for controlling conductive states of said self-extinguishing type switching elements according to said output vectors selected by said output vector selection means, when a spatial vector diagram is split into 6 ranges;

30 degrees, 30 degrees to 90 degrees, 90 degrees 20 to 150 degrees, 150 degrees 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges,

said output vector selection means comprising;

(a) a means for calculating said range number in is which said voltage command vector is present;

(b) a coordinate convert means for performing coordinate transformation of said command vector to a vector in an oblique coordinate system which takes a vector in a first specified angular direction and a vector in a second specified angular direction as two unit vectors;

(c) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors, of the 60-degree range in which said voltage command vector is present within the spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting each square-shape pattern into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;

(d) a judge means judging whether said voltage command vector which has undergone oblique coordinate transformation is present in any triangular domain in said oblique coordinate system diagram which has been split into said domains; and

(e) a select means for selecting said output vector corresponding to said triangular domain according to results of said judgement.

9. A controller for a power converter for controlling said power converter by being:

constructed from multiple converters, composed by bridge-connecting self-extinguishing type switching;

elements, and multiple DC reactors, which smooth the DC currents of the said multiple converters,

composed by connecting AC terminals of the said multiple converters to an AC load in common, and connecting the said multiple DC reactors in series with a positive terminal and negative terminal of each of said multiple converters,

said controller for a power converter comprising;

a vector command means for providing a command vector for an AC output current of said power converter;

an output-enabled vector generating means for providing all output-enabled vectors of said AC output currents which said power converter can generate;

a selected vector memory means for storing said output vector last outputted by said power converter;

a domain-split vector diagram generating means for, when a domain-split vector diagram generating means creates a domain-split vector diagram that contains output-enabled vectors based on output-enabled vectors from said output-enabled vector generating means, creating said domain-split vector diagram such that said domain containing the last output vector stored in said selected vector memory means is enlarged;

a vector selecting means for discriminating in which domain of said domain-split vector diagram created by said domain-split vector diagram generating means said command vector from aid vector command means is contained, and selecting and outputting said output-enabled vector which corresponds to said domain in which said command vector is present; and

a means for controlling a conductive state of said self-extinguishing type switching elements according to said output vector selected by said vector selecting device.

10. The controller for a power converter according to claim 9, wherein:

said domains of said domain-split vector diagram, which contain said output-enabled vectors, are regular hexagonal domains.

11. The controller for a power converter according to claim 9, wherein:

said domains of said domain-split vector diagram, which contain said output-enabled vectors, are rhombus domains.

12. A controller for a power converter for controlling sail power converter by being:

constructed from multiple converters, composed by bridge-connecting self-extinguishing type switching elements and multiple-transformers to primary sides of which AC outputs of the converters are connected,

composed by connecting the secondary terminals of said multiple transformers in common to an AC load, said controller for a power converter comprising;

a vector command means for providing a command vector for an AC output current of said power converter;

an output-enabled vector generating means providing all the output-enabled vectors of said AC output currents which said power converter can generate;

a selected vector memory means for storing said output vector last outputted by said power converter;

a domain-split vector diagram generating means for, when said domain-split vector diagram generating means creates a domain-split vector diagram that contains output-enabled vectors based on output-enabled vectors from said output-enabled vector generating means, creating said domain-split vector diagram such that said domain containing the last output vector stored in said selected vector memory means is enlarged;

a vector selecting means for discriminating in which domain of said domain-split vector diagram created by said domain-split vector diagram generating means said command vector from said vector command means is contained, and selecting and outputting said output-enabled vector which corresponds to said domain in which said command vector is present; and

a means for controlling a conductive state of said self-extinguishing type switching elements according to said output vector selected by said vector selecting means.

13. The controller for a power converter according to claim 12, wherein:

said domains of said domain-split vector diagram, which contain said output-enabled vectors, are hexagonal domains.

14. The controller for a power converter according to claim 12, wherein:

said domains of said domain-split vector diagram, which contain said output-enabled vectors, are rhombus domains.

15. The controller for a power converter according to claim 12, wherein:

said domains of said domain-split vector diagram, which contain said output-enabled vectors, are rhombus domains.

16. A controller for a power converter for controlling a multi-level output power converter which outputs multi-level voltages, comprising:

a vector command means for providing a command vector for an AC output current of said power converter;

an output-enabled vector generating means for providing all output-enabled vectors of said AC output currents which said power converter can generate;

a selected vector memory means for storing said output vector last outputted by said power converter;

a domain-split vector diagram generating means for, when said domain-split vector diagram generating means creates a domain-split vector diagram that contains output-enabled vectors based on output-enabled vectors from said output-enabled vector generating device, creating said domain-split vector diagram such that said domain containing the last output vector stored in said selected vector memory means is enlarged;

a vector selecting means for discriminating in which domain of said domain-split vector diagram created by said domain-split vector diagram generating means said command vector from said vector command device is contained, and selecting and outputting said output-enabled vector which corresponds to said domain in which said command vector is present; and

a means for controlling a conductive state of said self-extinguishing type switching elements according to said output vector selected by said vector selecting means.

17. The controller for a power converter according to claim 16, wherein:

said domains of said domain-split vector diagram, which contain said output-enabled vectors, are hexagonal domains.

18. A controller for a multi-level output power converter capable of outputting voltages at 4 levels or more, comprising:

a first calculate means for calculating a voltage command vector corresponding to the voltage which a power converter itself should output, based on an output current of said power converter itself;

a provide means for providing voltage actual vectors of voltages which said power converter itself is capable of outputting;

a select means for selecting said voltage actual value vector closest to said calculated voltage command vector; and

a second calculate means for calculating ON/OFF commands for said self-extinguishing elements which compose a main circuit of said power converter itself corresponding to said selected voltage actual vector.

19. A controller for multi-level output power convert according to claim 18, wherein:

said controller includes a multi-level output 3-phase power converter in which the bridge for 1 phase is composed of;

a split voltage source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units;

a series circuit, composed by connecting in series (2×

n) self-extinguishing elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, which outputs a voltage which is converted from the voltage of said DC voltage source from between the nth self-extinguishing element and the (n+1)th self-extinguishing element counting from the positive side of said DC voltage source;

at least (n-1) first clamp diodes of which the anode sides are connected to the negative sides of each split voltage source up to the (n-1)th spit voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element up to the (n-1)th self-extinguishing element from the positive side of said DC voltage source; and

(n-1) second clamp diodes of which the cathode sides are connected to the negative sides of each split voltage source to the (-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element between the n+1 )th self-extinguishing element and the (2n-1)th self-extinguishing element from the positive side of said DC voltage source.

20. A controller for multi-level output power convert according to claim 18, wherein;

said controller includes a multi-level output 3-phase power converter, comprising;

taking unit converters composed of converters which convert AC to DC power by rectification, and unit inverters, which convert said DC to AC power, as cell inverters; and

connecting a number of said cell inverters.

21. A controller for a multi-level output power converter capable of outputting voltages at 4 levels or more, comprising:

a first calculate means for calculating a voltage command vector corresponding to the voltage which a power converter itself should output, based on an output current of said power converter itself;

a means for splitting a plane, which takes the start point of said voltage actual vectors of the voltages which said power converter itself should output as its origin and in which each vector is represented by an end points of said voltage actual vectors, into domains which each contain said end point of one said voltage actual vector, and, when said end point of said voltage command vector is contained in any of those split domains, selecting said actual voltage vector indicated by said end point being contained in that domain as the voltage actual vector of the voltage which said power converter itself actually outputs; and

a second calculate means for calculating ON/OFF commands for said self-extinguishing elements which compose a main circuit of said power converter itself corresponding to said selected voltage actual vector.

22. A controller for multi-level output power convert according to claim 21, wherein:

said controller includes a multi-level output 3-phase power converter in which the bridge for 1 phase is composed of;

a split voltage source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units;

a series circuit, composed by connecting in series (2×

n) self-extinguishing elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, which outputs a voltage which is converted from the voltage of said DC voltage source from between the nth self-extinguishing element and the (n+1)th self-extinguishing element counting from the positive side of said DC voltage source;

at least (n-1) first clamp diodes of which the anode sides are connected to the negative sides of each split voltage source up to the (n-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element from the positive side of said DC voltage source; and

(n-1) second clamp diodes of which the cathode sides are connected to the negative sides of each split voltage source up to the (n-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element between the (n+1)th self-extinguishing element and the (2n-1)th self-extinguishing element from the positive side of said DC voltage source.

23. A controller for multi-level output power convert according to claim 21, wherein:

said controller includes a multi-level output 3-phase power converter, comprising

taking unit converters composed of the converters, which convert AC to DC power by rectification, and unit inverters, which convert said DC to AC power, as cell inverters; and

connecting a number of said cell inverters.

24. A controller for a multi-level output power converter capable of outputting voltages at 4 levels or more, comprising:

a first calculate means for calculating a voltage command vector corresponding to the voltage which a power converter itself should output, based on the output current of said power converter itself;

a means for splitting a plane, which takes the start point of said voltage actual vectors of the voltages which said power converter itself should output as its origin and in which each vector is represented by the end points of said voltage actual vectors, into regular hexagonal domains which each contain the end point of one said voltage actual vector, and, when the end point of said voltage command vector is contained in any of those split domains, selecting said actual voltage vector indicated by said end point being contained in that domain as the voltage actual vector of the voltage which said power converter itself actually outputs; and

a second calculate means for calculating a ON/OFF commands for said self-extinguishing elements which compose a main circuit of said power converter itself according to said selected voltage actual vector.

25. A controller for multi-level output power convert according to claim 24, wherein:

said controller includes a multi-level output 3-phase power converter in which the bridge for 1 phase is composed of;

a split voltage source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units;

a series circuit, composed by connecting in series (2×

n) self-extinguishing elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, which outputs a voltage which is converted from the voltage of said DC voltage source from between the nth self-extinguishing element and the (n+1)th self-extinguishing element counting from the positive side of said DC voltage source;

at least (n-1) first clamp diodes of which the anode sides are connected to the negative sides of each split voltage source up to the (n-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element from the positive side of said DC voltage source; and

(n-1) second clamp diodes of which the cathode sides are connected to the negative sides of each split voltage source up to the (n-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element between the (n+1)th self-extinguishing element and the (2n-1)th self-extinguishing element from the positive side of said DC voltage source.

26. A controller for multi-level output power convert according to claim 24, wherein:

said controller includes a multi-level output 3-phase power converter, comprising

taking unit converters composed of the converters, which convert AC to DC power by rectification, and unit inverters, which convert said DC to AC power, as cell inverters; and

connecting a number of said cell inverters.

27. A controller for a multi-level output power converter capable of outputting voltages at 4 levels or more, comprising:

a first calculate means for calculating a voltage command vector corresponding to the voltage which a power converter itself should output, based on the output current of said power converter itself;

a means for splitting a plane, winch takes the start point of the voltage actual vectors of the voltages which said power converter itself should output as its origin and in which each vector is represented by the end points of said voltage actual vectors, into 6 sections in the directions of 6 types of voltage vector which the said power converter itself is capable of generating, and, using straight lines parallel to two types of voltage vector in adjacent sections, then splitting said 6 sections into rhombiform domains which each contain the end point of one said voltage actual vector, and, when an end point of said voltage command vector is contained in any of those split domains, selecting said actual voltage vector indicated by said end point being contained in that domain as the voltage actual vector of the voltage which said power converter itself actually outputs; and

a second calculate means for calculating ON/OFF commands for said self-extinguishing elements which compose a main circuit of said power converter itself corresponding to said selected voltage actual vector.

28. A controller for multi-level output power convert according to claim 27, wherein:

said controller includes a multi-level output 3-phase power converter in which the bridge for 1 phase is composed of;

a split voltage source in which a DC voltage source is split into at least n, n being an integer of 3 or more, units;

a series circuit, composed by connecting in series (2×

n) self-extinguishing elements which are connected in parallel with said DC voltage source and to each of which a diode is connected in anti-parallel, which outputs a voltage which is converted from the voltage of said DC voltage source from between the nth self-extinguishing element and the (n+1)th self-extinguishing element counting from the positive side of said DC voltage source;

at least (n-1) first clamp diodes of which the anode sides are connected to the negative sides of each split voltage source up to the (n-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element from the positive side of said DC voltage source; and

(n-1) second clamp diodes of which the cathode sides are connected to the negative sides of each split voltage source up to the (n-1)th split voltage source from the positive side of said DC voltage source, and of which the cathode sides are respectively connected to the negative terminals of each self-extinguishing element between the (n+1)th self-extinguishing element and the (2n-1)th self-extinguishing element from the positive side of said DC voltage source.

29. A controller for multi-level output power convert according to claim 27, wherein:

said controller includes a multi-level output 3-phase power converter, comprising

taking unit converters composed of the converters, which convert AC to DC power by rectification, and unit inverters, which convert said DC to AC power, as cell inverters; and

connecting a number of said cell inverters.