JP2017017942A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion apparatus which supplies a line-to-line voltage with no distortion to a three-phase AC load by reducing a 3m-th harmonic wave component without using a complicated control block.SOLUTION: In the power conversion apparatus, bypass switches are connected between output terminals of single-phase output cells which are connected in series for each phase. When all the cells are sound, all the switches are turned off and an AC output voltage of each phase is controlled to be a first AC voltage for which the 3m-th harmonic wave component ((m) is a natural number) is superposed on a fundamental wave component. If a single-phase output cell belonging to a first phase circuit is broken down, a switch between the output terminals of that cell is turned on and when outputting a line-to-line voltage equal to or higher than a predetermined value, output voltages of second and third phase circuits are controlled to be a voltage for which the first AC voltage and a second AC voltage are added, a phase of at least one of the first and second AC voltages being different from that of the fundamental wave component, magnitudes of both the voltages being equal and a phase difference therebetween being an electric angle 60°.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power converter that outputs a three-phase AC voltage using a plurality of single-phase output cells.

Conventionally, by providing a series connection circuit of multiple single-phase output cells for three phases, high-voltage three-phase alternating current is output, and when any single-phase output cell fails, a healthy single-phase output cell is used. For example, Patent Document 1 discloses a power conversion device that continues operation.
FIG. 11 is a circuit configuration diagram of a single-phase output cell described in Patent Document 1. In FIG. 11, 100 is a single-phase output cell, 110 is a rectifier circuit to which a three-phase AC voltage is input, 120 is a capacitor series circuit of a DC intermediate circuit, and 130 is a single-phase two-level circuit composed of semiconductor switching elements Q _{1 to} Q _4. the inverter circuit, 140 a bypass circuit for the inter-output terminal of the inverter circuit 130 is bypassed (shorted), 151 and 152 output terminals of the single-phase AC voltage, 200 PWM control the switching element _Q 1 to Q ₄ of the inverter circuit 130 It is a control circuit for turning on and off by.

FIG. 12 shows a power converter configured by connecting a plurality of the single-phase output cells 100. In FIG. 12, 300 is a three-phase AC power source, and 400 is a power transformer, and A _{1 to} A ₅ , B _{1 to} B ₅ , and C _{1 to} C ₅ connected to the power transformer 400 are respectively described above. This corresponds to the single-phase output cell 100. Hereinafter, it is assumed that using the _{A 1 ~A 5, B 1 ~B} 5, C 1 ~C 5 as the sign of the single-phase output cell.

The output terminals of the single-phase output cells A _{1 to} A ₅ are connected in series between the common connection point N and the input terminal A of the load 500 such as a three-phase motor. Similarly, the single-phase output cells B _{1 to} B _5, the output terminals of the single-phase output cells C _{1 to} C ₅ are also connected in series between the common connection point N and the input terminals B and C, respectively.
Thereby, a three-phase alternating voltage is applied to the load 500 from the power converter.

In Patent Document 1, for example, when the A-phase single-phase output cells A4 and A5 fail, the output terminals of the single-phase output cells A4 and A5 are short-circuited by the bypass circuit 140 of FIG. Thus, the line voltages V _AC , V _BA , V _CB are obtained by shifting the phase difference of the output voltage of each phase from 120 ° electrical angle to 132.5 °, 95 °, 132.5 °, respectively. A technique for maintaining the phase difference of 120 ° at 120 ° is described. This technique is referred to as a first conventional technique.

That is, when the A-phase single-phase output cells A4 and A5 fail, the other B-phase and C-phase can be short-circuited between the output terminals of two single-phase output cells, for example, B4, B5, C4, and C5. The phase differences among the line voltages V _AC , V _BA , and V _CB can be maintained at 120 ° (see FIG. 4 of Patent Document 1), but the output voltage and line voltage of each phase are greatly reduced.
On the other hand, when the single-phase output cells A4 and A5 are out of order, when operating with the phase difference of the output voltage of each phase kept at 120 ° without short-circuiting the output terminals of the single-phase output cells of the other phases Therefore, the phase difference between the line voltages V _AC , V _BA , and V _CB is shifted from 120 ° (see FIG. 3 of Patent Document 1), and the load 500 is adversely affected.
Therefore, in the first prior art described above, the phase difference between the line voltages V _AC , V _BA , and V _CB is set to 120 by shifting the phase difference of the output voltage of each phase from 120 ° as shown in FIG. While maintaining at ° C, the output voltage drop is suppressed as much as possible to prevent the voltage utilization rate from falling.

Japanese Patent Application Laid-Open No. H10-228561 describes that the operation similar to that of the first prior art can be realized using the control block shown in FIG. This technique is referred to as a second conventional technique.
In the second prior art, as shown in FIG. 14, gains K _A , K _B , and K _C that can be adjusted in magnitude to sine wave voltage commands V _A ^* , V _B ^* , and V _C ^* for each phase are respectively set. The voltage commands U _A ^* , U _B ^* , and U _C ^* are generated by multiplication, and the maximum value and the minimum value are selected by the maximum value selection unit 601 and the minimum value selection unit 602, respectively. Then, an average value of the maximum value and the minimum value is obtained by the adder 603 and the divider 604, and this average value is subtracted from the original voltage commands U _A ^* , U _B ^* , U _C ^* by the adders 605 to 607. By doing so, each phase voltage command E _A ^* , E _B ^* , E _C ^* for PWM calculation is generated.

In this prior art, for example, when several single-phase output cells in the A phase fail and the output terminals are short-circuited, the number of faults (in other words, a healthy single-phase output cell in the A phase) increasing only the gain K a of the a-phase depending on the number). As a result, the peak value of U A * becomes larger than the peak values of U B * and U C * , and the average value of the maximum value and the minimum value is used as the original voltage command U A * , U B * , U C. * the result of subtracting from, * phase voltage command E a, E B *, the phase difference E C * is deviated from 120 °, is substantially equal peak value.
The vector diagram of the output voltage of each phase at this time is in a state where the position of the base point N is shifted upward from the center of the equilateral triangle, as in FIG. 13, and the phase difference of the line voltages V AC , V BA , V CB Can be maintained at 120 °.

Furthermore, in Patent Document 2, when x single-phase output cells out of a plurality of single-phase output cells connected in series in a certain phase fail, the output terminals are short-circuited and all other phases are also connected. A control method is described in which the operation of the single-phase output cell is continued and the phase difference of the output voltage of each phase is shifted from the original electrical angle of 120 ° to be θ _VU , θ _WV , θ _UW as shown in FIG. Has been. In FIG. 15, N ′ is the base point of each phase output voltage vector when the phase difference is 120 ° before the failure occurs, and N is the base point of each phase output voltage vector after the phase difference is shifted. . This technique is referred to as a third conventional technique.
Also in this prior art, the output voltage of each phase can be increased compared to the case where the output terminals of x single-phase output cells are short-circuited in the other phases in accordance with the failure occurrence phase. It is possible to keep the voltage phase difference at 120 °.

Japanese Patent Laid-Open No. 2000-60142 / Patent No. 4553167 (paragraphs [0005] to [0007], [0013], [0020], FIG. 1a, FIG. 1b, FIG. 5a, FIG. 7) Japanese Patent Laying-Open No. 2011-250534 / Japanese Patent No. 5676919 (paragraphs [0015] to [0029], FIGS. 3 to 6 etc.)

In the power conversion devices described in Patent Literatures 1 and 2 and the like, in order to increase the line voltage of the three-phase output when all the single-phase output cells are healthy, In addition to the fundamental wave component, it is often performed to superimpose a third m-order harmonic component (m is a natural number). In Equation 1, ω is the angular frequency of the fundamental wave, A1 is the amplitude of the fundamental wave component, A3m is the amplitude of the third mth harmonic component, B1 is the phase of the fundamental wave component, and B3m is the third mth harmonic component. The phase represents the phase, and θ is a value shifted from each other by 120 ° in the three phases.

The third m-order harmonic component of Equation 1 is equal as shown in Equation 2 when θ = 0 ° and θ = 120 °, for example. For this reason, only the fundamental wave component that does not include the third mth harmonic component can be left in the line voltage obtained by subtracting the two phase voltages.
[Formula 2]
A3m · sin {3m (ωt + B3m + 120 °)} = A3m · sin {3m (ωt + B3m + m × 360 °)} = A3m · sin {3m (ωt + B3m)}

  However, in the first prior art and the third prior art, the phase difference between the output voltages of the respective phases is not 120 °. Therefore, when the third m-order harmonic component is superimposed on the phase voltage, as described by Expression 2. The third m-order harmonic component cannot be canceled out by the line voltage, and there is a problem that the third m-order harmonic component is superimposed on the line voltage to cause voltage distortion.

Further, according to the second prior art, by controlling according to the control block of FIG. 13 when the unit output cell is healthy, as a result, it is possible to superimpose a third m-order harmonic component such as Equation 1 on the phase voltage. In addition, the output voltage applied to the load 500 can be increased.
However, when a failure occurs in a single-phase output cell and the output terminals are short-circuited and the operation is continued with another single-phase output cell, paragraph [0028] of Patent Document 1 states “... As in the first and second prior arts, it is impossible to cancel the third-order harmonic component with the line voltage and Supply voltage is distorted.
For this reason, in Patent Document 1, the third mth harmonic component included in the line voltage is canceled using the control block shown in FIG. In FIG. 16, reference numeral 608 denotes a divider, 609 denotes an integrator, and other portions are denoted by the same reference numerals as those in FIG.

In the control block of FIG. 16, the values obtained by the feedback loop including the integrator 609 are subtracted from the sine wave voltage commands V _A ^* , V _B ^* , and V _C ^* , and the gains K _A , K _B , and K _C are respectively obtained. The voltage commands U _A ^* , U _B ^* , and U _C ^* are multiplied to generate a complicated feedback control system as compared with FIG. 14, and there is a problem that adjustment is required. It was.

  Therefore, the problem to be solved by the present invention is that when a line voltage larger than the case of only the fundamental wave component is output by superimposing the third mth harmonic component on the phase voltage, a complicated control block is not required. An object of the present invention is to provide a power conversion device that can output a line voltage without distortion by reducing the third mth harmonic component.

According to the present invention, the phase of the fundamental component of the output voltage of each phase is shifted by 120 ° to match the phase circuit in which the number of healthy single-phase output cells is minimized due to the failure among the three phase circuits. A balanced voltage (first AC voltage) is used, and for a voltage higher than the balanced voltage, a three-phase AC voltage (first AC voltage) is obtained by performing an operation equivalent to V connection by two phase circuits other than the failed phase circuit. 2), and the power converter as a whole is added to the first and second AC voltages to be output.
As shown in FIGS. 13 and 15, such a voltage generation method is such that the output voltage phase of each cell in one phase circuit is all made equal, and the voltage vector of the phase circuit is controlled to be in a straight line. This is fundamentally different from the conventional technology that maximizes.
In the present invention, regarding the balanced first AC voltage generated by the three phase circuits (first to third phase circuits), even when the third mth harmonic component is superimposed on the fundamental wave component as the phase voltage. Thus, it is possible to output a larger line voltage than when the phase voltage is only the fundamental wave component without causing distortion in the line voltage. In addition, when a voltage higher than a predetermined value that can be output by the phase circuit to which the failed single-phase output cell belongs is output, an operation equivalent to V connection is performed by two phase circuits other than the phase circuit to which the failed single-phase output cell belongs. Since the second AC voltage equivalent to the case of adding is added, a line voltage without voltage distortion can be generated as a result of the addition.

That is, according to the first aspect of the present invention, all AC output terminals of N single-phase output cells (N is a natural number of 2 or more) for converting a DC voltage into a single-phase AC voltage by the operation of the semiconductor switching element are connected in series. The first to third phase circuits corresponding to three phases are connected in common and the other ends are connected to the input terminals of the three-phase AC load, respectively. In the power conversion apparatus, a bypass switch is connected between the output terminals of the single-phase output cell, the switch of the healthy single-phase output cell that is not faulty is turned off, and the phase circuit In the power conversion device in which the semiconductor switching element is controllable so that the output voltage becomes a first AC voltage in which a third m harmonic component (m is a natural number) is superimposed on a fundamental wave component,
When L single-phase output cells belonging to the first phase circuit (L is a natural number less than N) have failed, all the switches between the output terminals of the failed L single-phase output cells are turned on,
The first AC voltage is output from the first to third phase circuits up to a predetermined value of the voltage that can be output by the first phase circuit,
When outputting a voltage exceeding the predetermined value from the second and third phase circuits,
The output voltages of the second and third phase circuits are
A fundamental wave component in which at least one phase is different from the first alternating voltage and the fundamental wave of the first alternating voltage, the magnitudes of both are equal, and the phase difference between them is an electrical angle of 60 °. It controls so that it may become the voltage which added the 2nd alternating current voltage which has.

The invention according to claim 2 is the power conversion device according to claim 1, wherein the voltage of the fundamental wave component added as the second AC voltage is the fundamental wave component of the AC output voltage of the first phase circuit. The second phase circuit has a phase difference of + 150 ° in terms of electrical angle, and the third phase circuit has a phase difference of −150 ° in terms of electrical angle with respect to the phase.
In the present invention, when the voltage is generated by the operation equivalent to the V connection of the second and third phase circuits, a phase difference of ± 150 ° is provided with respect to the fundamental wave component of the AC output voltage of the first phase circuit. Thus, the phase of the fundamental component of the phase voltage (first AC voltage) balanced between the three phases before adding the second AC voltage and the phase of the three-phase voltage generated by the operation equivalent to V connection Can be matched. Thereby, compared with the case where both phases do not correspond, the voltage when adding the 1st, 2nd alternating voltage can be enlarged.

According to a third aspect of the present invention, in the power conversion device according to the first or second aspect, the predetermined value is a maximum output voltage {() when all the single-phase output cells belonging to the first phase circuit are healthy. N−L) / N} times.
The three-phase balanced voltage can be generated {(N−L) / N} times the maximum output voltage of the first phase circuit, so that the three-phase balanced voltage can be generated up to that voltage. For example, the output voltage can be made larger than when the predetermined value is less than {(N−L) / N}.

In the invention according to claim 4, the AC output terminals of N single-phase output cells (N is a natural number of 2 or more) for converting a DC voltage into a single-phase AC voltage by the operation of the semiconductor switching element are all connected in series. A phase circuit for a phase is configured, and one end of each of the first to third phase circuits corresponding to three phases is commonly connected, and each other end is connected to an input terminal of a three-phase AC load. A power converter,
A bypass switch is connected between the output terminals of the single-phase output cell to turn off the switch of the healthy single-phase output cell that has not failed, and the output voltage of the phase circuit becomes a fundamental wave component. In the power conversion device in which the semiconductor switching element can be controlled so as to be a first AC voltage on which a third m-order harmonic component (m is a natural number) is superimposed,
L ₁ unit (L ₁ is a natural number less than N) single-phase output cells belonging to the first phase circuit and L ₂ units (L ₂ is a natural number less than L ₁ ) single phase belonging to the second phase circuit When the output cell fails, the switches of the output terminals of all the failed single-phase output cells are turned on, and L ₂ single-phase circuits in a healthy third phase circuit in which the single-phase output cell is not broken Turn on the switch between the output terminals of the output cells,
The first AC voltage is output from the first to third phase circuits up to a predetermined value of the voltage that can be output by the first phase circuit,
When outputting a voltage exceeding the predetermined value from the second and third phase circuits,
The output voltages of the second phase circuit and the third phase circuit are:
As a fundamental wave component in which at least one phase is different from the first alternating voltage and the fundamental wave of the first alternating voltage, the magnitude of both is equal, and the phase difference between them is an electrical angle of 60 °. The second AC voltage is controlled to be a voltage obtained by adding the second AC voltage.
In the present invention, the second than the first phase circuit single phase output cell of _one L fails, the third phase circuit, (L 1 _{-L 2)} base output voltage of the single-phase output cells Thus, an operation equivalent to V-connection is possible, and a line voltage without voltage distortion can be generated.

  According to a fifth aspect of the present invention, in the power conversion device according to the fourth aspect, the fundamental wave component voltage added as the second alternating voltage is a fundamental wave component of the alternating current output voltage of the first phase circuit. The other one phase circuit has a phase difference of + 150 ° in electrical angle, and the other one phase circuit has a phase difference of −150 ° in electrical angle. An effect similar to that of the second aspect can be obtained.

The invention according to claim 6 is the power conversion device according to claim 4 or claim 5, wherein the predetermined value is a maximum output voltage of all single-phase output cells belonging to the first phase circuit in a healthy state. (N−L ₁ ) / N} times, so that the same effect as in the third aspect can be obtained.

According to the present invention, in the case where a 3m-order harmonic component is superimposed on each phase voltage to output a larger line voltage than when only the fundamental wave component is used, the 3m It is possible to output a line voltage without distortion by reducing the second harmonic component.
For this reason, for example, even when the load is a three-phase AC motor, torque ripple due to the third mth harmonic component does not occur in the output torque. Therefore, there is no risk of mechanical system vibration accompanying torque ripple, and adverse effects on the mechanical system, noise, and the like can be reduced.

It is a block diagram which shows embodiment of this invention. It is a block diagram of the control apparatus in embodiment of this invention. It is the vector diagram and waveform diagram of voltage for demonstrating operation | movement of embodiment of this invention. It is a vector diagram of a voltage for explaining operation of an embodiment of the present invention. It is a vector diagram which shows the element of the voltage vector shown in FIG.4 (b). It is a vector diagram which shows the other element of the voltage vector shown in FIG.4 (b). It is a wave form diagram of a voltage command for explaining operation of an embodiment of the present invention. It is a wave form chart of line voltage for explaining operation of an embodiment of the present invention. It is a vector diagram of a voltage for explaining operation of other embodiments of the present invention. It is a voltage vector diagram for demonstrating operation | movement of further another embodiment of this invention. 2 is a configuration diagram of a single-phase output cell described in Patent Document 1. FIG. It is a whole lineblock diagram of the power converter indicated in patent documents 1. It is explanatory drawing of a 1st prior art. It is a control block diagram which shows a 2nd prior art. It is explanatory drawing of a 3rd prior art. It is another control block diagram described in Patent Document 1.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a power conversion device according to this embodiment. In FIG. 1, U1 to U4 are U-phase single-phase output cells, and their output terminals are connected in series between a common connection point O and a U-phase terminal of a load M such as a three-phase motor. Similarly, the output terminals of the V-phase single-phase output cells V1 to V4 are connected in series between the common connection point O and the V-phase terminal of the load M, and the output terminals of the W-phase single-phase output cells W1 to W4. Are connected in series between the common connection point O and the W-phase terminal of the load M. Further, short-circuit switches SU1 to SU4, SV1 to SV4 constituting a bypass circuit are provided between the output terminals of the single-phase output cells U1 to U4, between the output terminals of the same V1 to V4, and between the output terminals of the same W1 to W4. , SW1 to SW4 are connected to each other.

The configurations of the single-phase output cells U1 to U4, V1 to V4, and W1 to W4 are all the same. For example, to describe the single-phase output cell U1 of the U-phase, by connecting the bridge circuit composed of semiconductor switching elements Q ₁ to Q ₄ of the IGBT or the like to both ends of a DC power source B, a single-phase two-level inverter is configured Yes.
The number of single-phase output cells connected in series in each phase is not limited to the illustrated example.

FIG. 2 is a block diagram of the control device in this embodiment, and supplies the desired three-phase AC voltage to the load M by controlling on / off the switching elements of the single-phase output cells U1 to U4, V1 to V4, and W1 to W4. Is to do.
In FIG. 2, failure information of each single-phase output cell is input to the cell bypass command unit 10. If no cell has failed, the cell bypass command unit 10 gives an off command to all the single-phase output cells U1 to U4, V1 to V4, W1 to W4, and all the switches SU1 to SU4 and SV1. -SV4, SW1-SW4 are opened. Further, when any single-phase output cell fails, an on command for closing and short-circuiting the switch connected between the output terminals of the cell is output from the cell bypass command unit 10.

  Further, the cell bypass command unit 10 outputs cell bypass information to the phase voltage calculation unit 20. This cell bypass information is information that identifies a single-phase output cell that has been bypassed due to a failure. Yes.

The load voltage command unit 40 in FIG. 2 outputs the amplitude command V ^* and the angular frequency command ω ^* of the three-phase AC voltage (line voltage) output to the load M.
In addition, the phase voltage calculation unit 20 sends the first AC voltage amplitude commands V _U1 ^* , V _V1 ^* , V _W1 ^{* to} the U-phase control unit 30U, the V-phase control unit 30V, and the W-phase control unit 30W ^. , Angular frequency command ω ^* , second AC voltage amplitude command V _U2 ^* , V _V2 ^* , V _W2 ^* , angular frequency command ω ^* , second AC voltage position relative to fundamental component of first AC voltage Outputs phase difference commands α _U2 ^* , α _V2 ^* , α _W2 ^* .

Here, as shown in the voltage vector diagram of FIG. 3A, the first AC voltage is a phase voltage such that the phase difference of each phase is 120 °. For example, the first AC voltage is shown in FIG. As described above, each phase voltage command having a substantially trapezoidal waveform obtained by superimposing the third m-th harmonic component (m is a natural number) on the fundamental wave component is based. The fundamental wave component of the trapezoidal wave has an advantage that it can be about 1.155 times that of a sine waveform having the same peak value. In addition, E in Fig.3 (a) shows the output voltage vector by one single phase output cell of each phase.
On the other hand, the second AC voltage is based on each phase voltage command in which the fundamental wave component is sinusoidal.
In the present embodiment, in order to increase the line voltage, when the single-phase output cell is healthy, the first conversion is performed from the power converter according to the predetermined amplitude commands V _U1 ^* , V _V1 ^* , V _W1 ^* and the angular frequency command ω ^* . An AC voltage is output, and for the second AC voltage, the amplitude commands V _U2 ^* , V _V2 ^* , and V _W2 ^* are all set to “0”, and the addition to the first AC voltage is unnecessary.

  The U-phase control unit 30U includes U-phase voltage command generation units 31U and 32U, an adder 33U, and a PWM signal generation unit 34U. The V-phase control unit 30V includes V-phase voltage command generation units 31V and 32V, an adder 33V, The PWM signal generator 34V is provided, and the W-phase controller 30W includes W-phase voltage command generators 31W and 32W, an adder 33W, and a PWM signal generator 34W.

Among these, for example, in the U-phase control unit 30U, the output of the U-phase voltage command generation unit 31U that generates a trapezoidal wave and the output of the U-phase voltage command generation unit 32U that generates a sine wave (fundamental wave component) are added. 33U is added and input to the PWM signal generator 34U as a final U-phase voltage command.
The other V-phase control unit 30V and W-phase control unit 30W are different from each other only in target phase circuits, and have the same functions as the U-phase control unit 30U.

As described above, when all the single-phase output cells are healthy, the fundamental wave component to be added as the second AC voltage is unnecessary, and therefore, the amplitude commands V _U2 ^* , V _V2 ^* , V _W2 for all phases are not necessary. ^* Becomes “0”, and the outputs of the U-phase voltage command generation unit 32U, the V-phase voltage command generation unit 32V, and the W-phase voltage command generation unit 32W all become “0”. Therefore, the PWM signal generators 34U, 34V, and 34W include the trapezoidal voltage of FIG. 3B generated by the U-phase voltage command generator 31U, the V-phase voltage command generator 31V, and the W-phase voltage command generator 31W. Each command (corresponding to the first AC voltage) is input.

PWM signal generating unit 34U, 34V, 34 W is a single-phase output cell U1~U4 based on voltage command of the trapezoidal waveform, V1-V4, generates a gate signal of the switching elements _Q 1 to Q ₄ of W1~W4 . By controlling each of the switching elements Q _{1 to} Q ₄ using these gate signals, an alternating voltage in which three phases are balanced can be supplied to the load M as shown in FIG.

Next, the operation in the case where only one U-phase single-phase output cell, for example, the single-phase output cell U4 in FIG. 1 has failed (when L = 1 in claim 1) will be described.
In this case, an ON command is output to the switch SU4 from the cell bypass command unit 10 to which the failure information of the single-phase output cell U4 is input, and the output terminals of the cell U4 are short-circuited. Further, an off command is given to the other switches SU1 to SU3, SV1 to SV4, SW1 to SW4, and all of them are opened. In addition, the cell bypass command unit 10 outputs cell bypass information indicating that the output of the single-phase output cell U4 is bypassed to the phase voltage calculation unit 20.

The phase voltage calculator 20 is based on the cell bypass information and the line voltage amplitude command V ^* and the angular frequency command ω ^* sent from the load voltage command unit 40, for example, FIG. 4 (a) or (b). The second AC voltage corresponding to the amplitude command V _U1 ^{* to} V _W1 ^{* of} the first AC voltage, the fundamental wave angular frequency command ω ^* , and the V connection operation of the V phase and the W phase so that the voltage vector shown in FIG. Amplitude commands V _V2 ^* , V _W2 ^* , angular frequency command ω ^* , and second AC voltage phase difference commands α _V2 ^* , α _W2 ^* with respect to the fundamental wave component of the U-phase first AC voltage And output.
At this time, since the output of the U-phase single-phase output cell U4 is bypassed, the amplitude command V _U2 ^* of the second AC voltage for the U-phase is the same in either case of FIGS. 4 (a) and 4 (b). “0”.

Note that the magnitudes of the voltage vectors V _a V ′ and W _a W ′ in FIG. 4A are equal to E ₂ ′, and the phase difference is 60 °, and the voltage vectors V _a V, The magnitude of W _a W is equal to E ₂ and the phase difference is 60 °.
Here, the voltage vectors V _a V ′ and W _a W ′ and V _a V and W _a W in FIGS. 4A and 4B are the V-phase corresponding to the single-phase output cell U4 of the failed U-phase. The amplitude and phase angle of the output voltage vector of the single-phase output cell V4 are made different from the output voltage vectors of the other V-phase single-phase output cells V1 to V3, and the W corresponding to the U-phase single-phase output cell U4 The amplitude and phase angle of the output voltage vector of the single-phase output cell W4 of the phase are made different from the output voltage vectors of the other single-phase output cells W1 to W3 of the W phase.

The difference between FIG. 4A and FIG. 4B is that, in the case of FIG. 4A, the voltage vector V _a V ′, based on the fundamental component of the U-phase first AC voltage, The phase difference commands α _V2 ^* and α _W2 ^{* of} W _a W ′ are not ± 150 °, and in the case of FIG. 4B, the phase difference command α _V2 ^* of the voltage vector V _a V is −150 °. The phase difference command α _W2 ^{* of} the voltage vector W _a W is + 150 °.
The voltage vector shown in FIG. 4B is obtained by adding the voltage vectors shown in FIGS. That is, FIG. 5 shows all phases of single-phase output cells U1 to U3, V1 to V3, and W1 to W3 in accordance with the U phase where the number of healthy single-phase output cells is minimized (three). FIG. 6 shows the voltage vector output when the V-phase single-phase output cell V4 and the W-phase single-phase output cell W4 are operated corresponding to the V-connection. It corresponds.

According to FIGS. 5 and 6, since the voltages are balanced in three phases, the line voltage balanced in three phases is also output in FIG. 4B obtained by synthesizing these voltage vectors. As a result, a three-phase AC voltage without distortion can be obtained.
The voltage vector shown in FIG. 4A corresponds to the case where the voltage vector corresponding to the V connection shown in FIG. 6 is slightly rotated. Also, since the phase voltage equivalent in FIG. 6 and the phase voltage in FIG. 5 have the same voltage vector direction in all three phases, the magnitude of the voltage in FIGS. 4A and 4B is E ₂ = E _{2. 4A} , the phase difference command α _V2 ^* of the voltage vector V _a V is set to −150 ° and the phase difference command α _W2 ^{* of the} voltage vector W _a W is set as shown in FIG. When the angle is + 150 °, the line voltage can be increased. This embodiment corresponds to the invention according to claim 2.

7A shows a U-phase voltage command generation unit 31U, a V-phase voltage command generation unit 31V, and a W-phase voltage command generation unit in FIG. 2 when the voltage vector as shown in FIG. 4B is realized. An output waveform (trapezoidal wave command) of 31 W and output waveforms (additional sine wave command) of the V-phase voltage command generation unit 32V and the W-phase voltage command generation unit 32W are shown. FIG. 7B shows the output waveform of each phase adder 34U, 34V, 34W in FIG. 2 (waveform obtained by adding the trapezoidal wave command and the addition sine wave command of FIG. 7A for each phase). ing.
These waveforms are waveforms when the line voltage is maximized, and one single-phase output cell of the U phase fails in the state where the number of single-phase output cells connected in series for each phase is N = 4. Since the output terminals are bypassed, in the waveform of FIG. 7B, the peak value of the U-phase voltage command is 0.75 [PU], which is the peak value of the V-phase and W-phase voltage commands. It is 3/4 of a certain 1.0 [PU].

  FIG. 8 is a waveform diagram showing the line voltage of the load M obtained by each phase voltage command of FIG. According to FIG. 8, there is no distortion in the voltage waveform, and the magnitude thereof is 87.5% (= 1.75 / 2.00) as compared to when all the single-phase output cells are healthy.

Further, FIG. 9 is a voltage vector diagram when the number of single-phase output cells connected in series N = 4 and when two U-phase single-phase output cells fail (when L = 2 in claim 1). .
For example, when the U-phase single-phase output cells U1 and U2 fail, the cell bypass command unit 10 in FIG. 2 outputs an ON command so as to short-circuit the switches SU1 and SU2 of the cells U1 and U2, The phase voltage calculator 20 generates each command corresponding to the voltage vector in FIG. That is, for example, the phase difference command α _V2 ^* of the voltage vector V _b V by the V-phase single-phase output cells V1 and V2 is −150 °, and the phase difference of the voltage vector W _b W by the W-phase single-phase output cells W1 and W2 The command α _W2 ^{* is set} to + 150 °.

FIG. 10 shows a case where the number of serially connected single-phase output cells is N = 4, two U-phase single-phase output cells and one V-phase single-phase output cell fail (L ₁ in claim 4). = 2 and L ₂ = 1). In this case, the cell bypass command unit 10 outputs an ON command so as to short-circuit the switches of the U-phase and V-phase failed cells, and the phase voltage calculation unit 20 corresponds to each voltage vector of FIG. Generate a command. That is, for example, the phase difference command α _V2 ^* of the voltage vector V _c V by one single V-phase output cell is −150 °, and the voltage vector W _c W by one W-phase single-phase output cell is The phase difference command α _W2 ^{* is set} to + 150 °.
These embodiments correspond to the inventions according to claims 4 to 6.

In the first conventional technique shown in FIG. 13, even if the line voltage is increased by superimposing the third mth harmonic component on the phase voltage of the single-phase output cell when it is healthy, the single-phase output cell In order not to cause voltage distortion of the line voltage during bypass due to a failure, it is necessary to stop the superimposition of the third mth harmonic component.
For example, when each phase voltage waveform has a trapezoidal waveform as shown in FIG. 3B when the single-phase output cell is healthy, the fundamental wave component of the line voltage is (1) by changing this waveform to a sine waveform. /1.155). Considering this drop, if one single-phase output cell fails with the number N of cells connected in series N = 4 by the control method shown in FIG. 12, the voltage is output only up to 79% of the normal state. Can not do it.
In the case of this same condition, in the present invention, as described in the explanation of FIG. 8, the line voltage can be output up to 87.5% in the normal state, so the output voltage range in the cell bypass is shown in FIG. The conventional technology can be expanded.
Incidentally, in the above-mentioned Patent Document 2, there is no particular mention of increasing the line voltage by superimposing the third m-order harmonic component, including when healthy.

  The present invention can be used for an AC power supply apparatus that supplies a high voltage to various three-phase AC loads.

Q _{1 to} Q ₄ : Semiconductor switching element B: DC power supplies U1 to U4, V1 to V4, W1 to W4: Single-phase output cells SU1 to SU4, SV1 to SV4, SW1 to SW4: Switch (bypass circuit)
10: Cell bypass command unit 20: Phase voltage calculation unit 30U: U phase control unit 30V: V phase control unit 30W: W phase control unit 31U, 32U: U phase voltage command generation unit 31V, 32V: V phase voltage command generation unit 31W, 32W: W-phase voltage command generators 33U, 33V, 33W: Adder 34U: U-phase PWM signal generator 34V: V-phase PWM signal generator 34W: W-phase PWM signal generator 40: Load voltage command unit

Claims (6)

The AC output terminals of N single-phase output cells (N is a natural number of 2 or more) that converts DC voltage into single-phase AC voltage by the operation of the semiconductor switching element are connected in series to form a phase circuit for one phase. Each of the first to third phase circuits corresponding to the three-phase portion is commonly connected to each other, and the other ends are respectively connected to the input terminals of the three-phase AC load,
A bypass switch is connected between the output terminals of the single-phase output cell to turn off the switch of the healthy single-phase output cell that has not failed, and the output voltage of the phase circuit becomes a fundamental wave component. In the power conversion device in which the semiconductor switching element can be controlled so as to be a first AC voltage on which a third m-order harmonic component (m is a natural number) is superimposed,
When L single-phase output cells belonging to the first phase circuit (L is a natural number less than N) have failed, all the switches between the output terminals of the failed L single-phase output cells are turned on,
The first AC voltage is output from the first to third phase circuits up to a predetermined value of the voltage that can be output by the first phase circuit,
When outputting a voltage exceeding the predetermined value from the second and third phase circuits,
The output voltages of the second and third phase circuits are
A fundamental wave component in which at least one phase is different from the first alternating voltage and the fundamental wave of the first alternating voltage, the magnitudes of both are equal, and the phase difference between them is an electrical angle of 60 °. A power conversion device that is controlled so as to be a voltage obtained by adding the second AC voltage. In the power converter device according to claim 1,
The voltage of the fundamental wave component added as the second AC voltage is + 150 ° in electrical angle in the second phase circuit with reference to the phase of the fundamental wave component of the AC output voltage of the first phase circuit. The power converter is characterized in that the third phase circuit has a phase difference of −150 ° in electrical angle. In the power converter device according to claim 1 or 2,
The power converter according to claim 1, wherein the predetermined value is {(N−L) / N} times the maximum output voltage when all the single-phase output cells belonging to the first phase circuit are healthy. The AC output terminals of N single-phase output cells (N is a natural number of 2 or more) that converts DC voltage into single-phase AC voltage by the operation of the semiconductor switching element are connected in series to form a phase circuit for one phase. Each of the first to third phase circuits corresponding to the three-phase portion is commonly connected to each other, and the other ends are respectively connected to the input terminals of the three-phase AC load,
A bypass switch is connected between the output terminals of the single-phase output cell to turn off the switch of the healthy single-phase output cell that has not failed, and the output voltage of the phase circuit becomes a fundamental wave component. In the power conversion device in which the semiconductor switching element can be controlled so as to be a first AC voltage on which a third m-order harmonic component (m is a natural number) is superimposed,
L ₁ unit (L ₁ is a natural number less than N) single-phase output cells belonging to the first phase circuit and L ₂ units (L ₂ is a natural number less than L ₁ ) single phase belonging to the second phase circuit When the output cell fails, the switches of the output terminals of all the failed single-phase output cells are turned on, and L ₂ single-phase circuits in a healthy third phase circuit in which the single-phase output cell is not broken Turn on the switch between the output terminals of the output cells,
The first AC voltage is output from the first to third phase circuits up to a predetermined value of the voltage that can be output by the first phase circuit,
When outputting a voltage exceeding the predetermined value from the second and third phase circuits,
The output voltages of the second phase circuit and the third phase circuit are:
As a fundamental wave component in which at least one phase is different from the first alternating voltage and the fundamental wave of the first alternating voltage, the magnitude of both is equal, and the phase difference between them is an electrical angle of 60 °. And a second AC voltage. The power converter is controlled to be a voltage obtained by adding the second AC voltage. In the power converter device described in Claim 4,
The voltage of the fundamental wave component added as the second AC voltage is based on the phase of the fundamental wave component of the AC output voltage of the first phase circuit, and the electrical angle is + 150 ° in the other one phase circuit. A power converter characterized by having a phase difference of −150 ° in the remaining one phase circuit. In the power converter device according to claim 4 or 5,
The predetermined value is {(N−L ₁ ) / N} times the maximum output voltage when all the single-phase output cells belonging to the first phase circuit are healthy.

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