JP5012309B2 - Switching pattern switching method for AC-AC direct conversion device - Google Patents

Description

  The present invention relates to an AC-AC direct conversion device (matrix converter) that obtains a multi-phase output converted into an arbitrary voltage or frequency from a multi-phase AC power source, and particularly at the time of sector transition in a virtual indirect space vector modulation system. The present invention relates to a switching pattern switching method of an AC-AC direct conversion device that optimizes a switching pattern.

  This type of AC-AC direct conversion device that has existed in the past switches high-speed bidirectional switches using self-extinguishing semiconductor elements, and can switch from single-phase or multi-phase power supply AC to any frequency and size. 1 is a conversion device that directly converts power into a power source, and is configured as shown in FIG.

  FIG. 1 shows a basic configuration of a three-phase / three-phase AC-AC direct conversion device. A three-phase AC power source 1 includes an input filter unit 2 including a reactor and a capacitor and nine bidirectional switches (Sru to Srw, Ssu to Ssw). , Stu to Stw), it is connected to an arbitrary load 4 via a semiconductor power conversion unit 3 configured by the following.

  Nine bidirectional switches Sru to Srw, Ssu to Ssw, and Stu to Stw are not limited to the detailed configuration method, such as when configured with 18 reverse blocking IGBTs or combining a semiconductor element such as a normal IGBT and a diode. However, it is comprised with the switching element which can transfer electric power bidirectionally.

  In addition, as shown in FIG. 1, hereinafter, the power three phases are RST phases and the output three phases are UVW phases.

  A method of simultaneously converting the input current and the output current into a sine wave by the space vector modulation method using the nine bidirectional switches of the AC-AC direct conversion device configured as described above is disclosed in Non-Patent Documents 1 and 2, for example. Are listed.

  Basic control methods for AC-AC direct conversion devices can be broadly divided into those based on direct AC / AC conversion (direct type) and those controlled based on a virtual articulated converter having a virtual DC link (virtual indirect). Shape).

  The method of Non-Patent Document 2 is based on a virtual indirect type that has been used for a long time. As shown in FIG. 2, a virtual PWM rectifier and an inverter are considered and controlled independently. As a control method, a space vector modulation method for controlling a PWM inverter that has been conventionally used is applied. In FIG. 2, the nine bidirectional switches Sru to Srw, Ssu to Ssw, Stu to Stw of the semiconductor power conversion unit 3 are twelve virtual switches Srp, Srn, Ssp, Ssn, Stp, Stn, Sup, Sun, Svp. , Svn, Swp, Swn are equivalently replaced.

  FIG. 3 shows the definition of space vectors on the input side and output side. In FIG. 3A, the input side space vector is PWM controlled to match the current command value Ii * using i1 and i6 (for example, if i1, virtual switches Srp and Ssn in FIG. 2 are turned on). .

  Since the magnitude of the input current depends on the load, only the phase is given as a command value, and control is performed so that the maximum circular locus is always drawn. When it is desired to set the power factor to 1, it is sufficient to match the power supply voltage phase.

  In FIG. 3B, the output side space vector is similarly PWM controlled using v1 (PNN) and v2 (PPN) so as to match the output voltage command value Vo * (for example, if v1 (PNN)). , The virtual switches Sup, Svn, Swn in FIG. 2 are turned on).

  Since the virtual DC voltage Vpn used for controlling the inverter can be determined by the power supply voltage phase on the input side, the output voltage controls both magnitude and phase.

FIG. 4 shows an example in which a space vector in one arbitrary sector and its output time (duty) are defined. As indicated by the mathematical expressions in the figure, the duties d _A and d _{B of} the virtual rectifier and the duties d _X and d _Y of the virtual inverter are multiplied and synthesized to obtain the duty and switching pattern of the AC-AC direct conversion device. (See Non-Patent Documents 1 and 2.)

  In the above virtual indirect space vector modulation method, five pulses are output in one PWM control cycle to make the input / output waveform sinusoidal. The output order of the pulses is preferably arranged in consideration of the switching frequency, loss, harmonics, and the like.

  Here, the input and output sectors are defined by dividing the space as shown in FIG. In the case of the input current space vector in FIG. 5A, the sector 1 is set when the phase of the input current command vector is 0 degrees to 30 degrees, and the sector 2 is set between 30 degrees and 60 degrees. Similarly, if it continues over 360 degree | times, 12 sectors of 1-12 can be defined with a phase. In the case of the output voltage command vector shown in FIG. 5B, six sectors can be defined every 60 degrees.

  Then, sector modes are defined as shown in Table 1 from the sectors of the input current space vector and the output voltage space vector of FIG.

  When the input sector is 1, 4, 5, 8, 9, 12, the output sector is 1, 3, 5 or when the input sector is 2, 3, 6, 7, 10, 11, the output sector is 2, 4, If it is 6, sector mode 1 (sm1) is set, and when the input sector is 1, 4, 5, 8, 9, 12, the output sector is 2, 4, 6, or the input sector is 2, 3, 6, 7, 10, If the output sector is 1, 3 or 5 at 11, the sector mode 2 (sm2) is defined.

  Based on these definitions and discrimination of the input sector evenness, switching transition patterns are defined as shown in Table 2.

The duty in Table 2 means the space vector pulse and output time of duty d _AX (= d _A × d _X ) defined in FIG. The same applies to the other d _AY , d _BX , d _BY and d _Z.

  In Table 2, it means that switching is performed while folding both vectors v1 → v2 → v3 → v4 → v5 or vectors v5 → v4 → v3 → v2 → v1 in this order. If switching is performed in this order, each phase is switched at the time of pulse switching, so that the number of times of switching can be minimized without simultaneously switching two or more phases.

The above arrangement of the pulse arrangement order is basically the conventional technique already disclosed in Non-Patent Documents 1 and 2.
Y. Tadano, S .; Urushibata, M .; Nomura, Y. et al. Sato, andM. Ishida: “Direct Space Vector PWM Strategies for Three-Phase to Three-Phase Matrix Converter”, IEEE Proc. of the 4th Power Convergence Conference (PCC-Nagoya / Japan), April, 2007, LS4-1-3, pp. 1064-1071 (2007) “Space Vector Modulated Three-Phase to Three-Phase Matrix Converter with Input Power Factor Correction” L. Huber et al. IEEE trans. On Industry Applications, vol. 31, no. 6,1995

  However, the pattern arrangement is optimized only within one control period, and can be minimized when there is no change in the sector in the definition of FIG. 5, but this is not the case when the sector transitions. That is, the moment when the sector in which the input current command value or the output voltage command value exists shifts corresponds to the moment when the magnitude relationship between the instantaneous values of the input power supply voltage R phase, S phase, and T phase switches. In such a case, the above simple loop switching is not necessarily optimized.

  For example, when the output sector defined in FIG. 5 is “1”, consider the moment when the input sector changes from “12 → 1”. The large / medium / small relationship of the input power supply voltage at this time is Vr> Vs> Vt, and the large / medium / small relationship of the output voltage command value is Vu> Vv> Vw. Table 3 shows the relationship between the vectors of the five PWM pulses and the duty.

  In Table 3, for example, “RSS” means a switching pattern that connects the R phase to the U phase, the S phase to the V phase, and the S phase to the W phase. The upper part of Table 3 is for input sector 12 and output sector 1, and the lower part is for input sector 1 and output sector 1. The moment the sector changes, the pattern moves from the upper level to the lower level. In the loop switching, the vector v1 → v2 → v3 → v4 → v5 → (update) → v5 → v4 → v3 → v2 → v1 → (update) → v1 → v2 →... This is when v1 or v5.

  For example, when transitioning from the upper stage to the lower stage of Table 3 at v1, the switching pattern changes from “RSS” to “RTT”, and the V phase and the W phase change simultaneously. If v5 is updated, “TTT” → “SSS” and all three phases are switched simultaneously. That is, it can be seen that the simple folding switching method does not always minimize the number of switching times during a sector transition transition.

  As for other sector transition patterns, there may occur a case where optimization is not performed in v1 → update → v1, v5 → update → v5.

  The present invention solves the above-described problems, and an object of the present invention is to provide a switching pattern switching method for an AC-AC direct conversion device in which the number of switching operations during a sector transition transition is reduced.

  The invention according to claim 1 for solving the above-mentioned problem is that the duty of the space vector of the input-side virtual rectifier and the space vector of the output-side virtual inverter in the AC-AC direct conversion device having a plurality of bidirectional switches. A switching pattern switching method for an AC-AC direct conversion device that synthesizes a duty, generates a plurality of switching patterns in which five space vectors are arranged per control cycle, and PWM-controls the bidirectional switch based on the switching patterns. A region where the input current command value vector and the output voltage command value vector exist, each of which is configured by dividing the input and output side space vectors into a plurality of spaces, is defined as an input sector, and the input sector and output Two sector modes are defined from the combination of sectors, and the input and output sectors And based on the sector mode, performs a process of determining a switching pattern for reducing the number of switching, is characterized by the PWM controlling said bidirectional switch by a switching pattern the determined.

  According to a second aspect of the present invention, in the first aspect, the process for determining the switching pattern is arranged at one end of the generated switching pattern during a transition in which the sector mode does not change and the input sector shifts. When the switching pattern is updated at the timing of the space vector, the space vector placed at the other end of the switching pattern used for the next PWM control is transferred to the space vector placed at the other end of the switching pattern. When the switching pattern is updated at this timing, the switching process at the time of updating is performed to shift to the space vector arranged at one end of the switching pattern used for the next PWM control.

  According to a third aspect of the present invention, in the first aspect, the process of determining the switching pattern is performed in a mode in which the number of times of switching is two by updating the switching pattern during a transition in which the output sector shifts. While maintaining the sector state before the transition, the switching pattern before the update is turned back and PWM control is performed, and then the sector maintenance is released and arranged at the end of the switching pattern used for the next PWM control without switching. It is characterized in that one control cycle delay process for shifting to the space vector is performed.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the process of determining the switching pattern does not perform the one control cycle delay process when two or more output sectors are transferred.

  According to a fifth aspect of the present invention, in the first aspect, the process of determining the switching pattern is performed by the generated switching during a transition in which an output sector shifts and an input sector shifts from an odd sector to an even sector. A normal update process is performed in which the space vector arranged at one end of the pattern is shifted to the space vector arranged at the same end of the switching pattern used for the next PWM control, and the output sector is The switching process at the time of updating according to claim 2 is performed at the time of transition when the input sector shifts from an even sector to an odd sector.

  According to a sixth aspect of the present invention, in the fifth aspect, the process of determining the switching pattern is a transition time when the output sector is shifted and the input sector is shifted from the odd sector to the even sector, and the switching pattern is determined. In the mode in which the number of times of switching is 3 by updating, the one control cycle delay process according to claim 3 is performed instead of the normal update process.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the duty of the vector of the switching pattern before the update among the switching patterns is compared with the first carrier wave, and the next PWM A switching signal for performing the PWM control is obtained by comparing a duty of a vector of a switching pattern used for control with a second carrier wave that is 180 degrees out of phase with the first carrier wave. It is a feature.

(1) According to the first to seventh aspects of the present invention, in the AC-AC direct conversion device, at the time of transition when the input sector shifts (the moment when the sector where the input current command value vector exists shifts, that is, the input power supply voltage The moment when the large, medium, and small relations of the instantaneous values of the R phase, S phase, and T phase are switched), or when the output sector transitions (the moment when the sector where the output voltage command value vector exists transitions, that is, the output voltage U phase, V The switching frequency can be reduced at the moment when the large / medium / small relationship between the command values of the phase and the W phase is switched. As a result, switching loss can be reduced.
(2) According to the invention described in claim 2, the switching frequency at the time of transition can be reduced by performing the switching process at the time of transition when the sector mode does not change and the input sector shifts. .
(3) According to the invention described in claim 3, although one control cycle delay process is performed, a delay of one control cycle is temporarily generated at the time of transition of the output sector, but the number of switching times is zero. Can be migrated at a time.
(4) According to the invention described in claim 4, the output voltage command value vector changes suddenly due to a sudden load fluctuation or a step change of the torque command / speed command value, and two or more output sectors change transiently. In this case, since the one control cycle delay process is not performed, the transient response at the time of the sudden change can be given priority although the number of times of switching occurs once or twice.
(5) According to the invention described in claim 5, by performing the normal update process or the update time switching process at the time of transition in which the input sector and the output sector simultaneously shift, the number of times of switching at the time of the transition can be reduced. it can.
(6) According to the invention described in claim 6, by performing one control cycle delay process, the transition pattern in which the number of times of switching is three can be completely eliminated, and the number of times of switching can be reduced. At the same time, it is possible to reduce the pulsating component of current and voltage due to the simultaneous switching of the three phases.
(7) According to the invention described in claim 7, when PWM control is performed by the carrier comparison method, the same effects as in the above (1) to (6) can be obtained, and the number of times of switching can be reduced at the time of sector transition. Can be reduced.

  Hereinafter, the AC-AC direct conversion device will be described as an embodiment of the present invention with reference to the drawings as a matrix converter that PWM-controls the bidirectional switch, but the present invention is limited to the following embodiments. It is not a thing.

  In the present invention, taking advantage of the freedom of rearrangement of the switching pattern of the space vector modulation method, the input sector and the output sector defined as shown in FIG. 5 and the sector mode defined in Table 1 defined from the combination thereof are used. Based on this, a switching pattern for reducing the number of times of switching at the sector transition transition time is determined, and the arrangement order of the switching patterns is switched.

Example 1
In this embodiment, attention is paid to the change of the sector mode and the input sector. Focusing on the example in Table 3 (an example in which the input sector changes from 12 to 1 and the output sector 1 does not change), when updating the upper stage v1 (vector arranged at one end of the switching pattern), the lower stage v5 (switching pattern When the upper-stage v5 is updated to the lower-stage v1 when the update-time switching process is performed, the switching pattern becomes RSS → SSS, TTT → RTT, both of which are U-phase switching. Become. Therefore, in this case, it can be seen that the number of times of switching can be reduced by 1 to 2 times compared to the case where simple loop switching is performed.

  As described above, when all patterns are considered at the moment when the input sector changes, the optimum transition pattern can be defined as shown in Table 4.

  Table 4 shows the optimum pattern to be shifted at each timing of v1 and v5 by integrating the change of the input sector into the change of the sector mode defined in Table 1. v1 → v1, v5 → v5 are normal folding patterns, and v1 → v5, v5 → v1 are patterns in which the way of folding is switched instantaneously.

  Since it is assumed that the input is connected to the power source, the sector transition order is: 11 → 12 → 1 → 2 → 3 →. The reverse pattern does not usually occur, but if the same table is used, it is optimized even in that case.

  In this embodiment, attention is paid at the time of transition when the input sector shifts, and switching is performed according to the optimum transition pattern of Table 4. Therefore, the number of switching can be reduced and the pulsating components of current and voltage due to simultaneous switching can be reduced.

(Example 2)
In the first embodiment, attention is paid to the change in the input sector. In this embodiment, attention is paid to the change in the output sector. For example, when the output voltage command value is in the normal rotation direction (sector transition is the order of 1 → 2 → 3 → 4 → 5 → 6 → 1 →... In FIG. 5B), the input sector 1 and the output sector 1 → 2 When attention is paid to the moment of change, the switching pattern shown in Table 5 is obtained.

  In Table 5, the upper stage is for input sector 1 and output sector 1, and the lower stage is for input sector 1 and output sector 2.

  When shifting from the upper stage to the lower stage, the number of times of switching is smaller when v1 is updated and the transition is made to v1. That is, v1 → v1: RTT → TRT (switching twice), v1 → v5: RTT → SSS (switching three times). Further, when v5 is updated, the number of times of switching is smaller when the process is shifted to v5 as it is. That is, v5 → v1: SSS → TRT (3 times switching), v5 → v5: SSS → SSS (0 times switching). Similarly, in the case of a pattern in which the output voltage command value is reversed (output sector transition is the order of 6 → 5 → 4 → 3 → 2 → 1 → 6 →... In FIG. 5B), the transition pattern remains unchanged. Good.

  From the above result, when the output sector is shifted, a normal loop pattern may be used as usual without performing any special processing. However, in this embodiment, switching that occurs at the time of forward rotation v1 update and reverse rotation v1 update. We propose a method to reduce the number of times to 1 or less. Table 6 summarizes the transition pattern when the output sector changes.

  In Table 6, the upper side (a) shows the normal rotation, and the lower side (b) shows the reverse rotation pattern. Since the portion marked with x in Table 6 is the above-described mode in which the number of times of switching is two times, the normal folding pattern v1 → while maintaining the previous sector state without shifting to the sector at this time v1 is performed (shift from v1 to v1 in the same stage). Then, for example, v1 → v2 → v3 → v4 → v5 in the same stage in Table 5 is switched, and the sector information latch is released at the timing of v5 → v5 generated with a delay of one control cycle time, and the switching frequency is 0 times. The migration is completed in the v5 update pattern that can be migrated (in Table 5, v5 → v5: SSS → SSS).

  According to the present embodiment, a delay corresponding to one control period is temporarily generated, but it is possible to shift in a pattern that does not involve switching at all (changes can be performed zero times) during a transition in which the output sector changes.

(Example 3)
For the input supply voltage, when operating at 60H _Z to no 50H _Z If the commercial AC power source is large and even when the input of the distributed power supply such as a gas turbine, the input sector with a large variation of two or more sectors It is difficult for jumping to occur. On the other hand, with regard to the output voltage command value, there may be a case where two or more output sectors are generated due to a sudden load fluctuation or a step change in the torque command / speed command value (in the above embodiments, the sector is Only when it changes one by one). Examples of input sector 1 and output sectors 1 to 6 are summarized in Table 7.

  In Table 7, when v5 is updated, if it is returned as v5 → v5 as it is, it is always SSS, and the transition can be made with 0 switching times. Next, focusing on v1 update, it can be seen that when v1 → v1, the switching can be performed once or twice. Therefore, wherever the output sector flies, it can be shifted once or twice, but it is possible to select whether to limit to the transition pattern in v5 as in the second embodiment. That is, when the output sectors are shifted one by one, there is not much influence even if there is a delay of one control cycle by the one control cycle delay process of the second embodiment, but a voltage command is applied so that two or more sectors fly. In this case, since it is a mode that requires a transient response, the process of the second embodiment delayed by one control cycle is passed and switched so as to allow the occurrence of one or two switching times.

Example 4
In this embodiment, a case is considered where the input sector and the output sector change simultaneously. As described above, it is assumed that the input sector shifts one by one in the forward direction, and the output sector can jump to any sector state.

  Table 8 shows five pulse patterns extracted from input sectors 1 to 3 and output sectors 1 to 6.

  In Table 8, for example, consider a case where the input sector changes from 1 to 2 (odd sector → even sector), and the output sector is not limited from 1 to 6 from where to where.

  When v1 is updated, the transition pattern from v1 to v1 transitions from “RTT / TRT / TTR” to any one of “RRT / TRR / RTR”, and the switching frequency is either one or three times. is there. In the transition pattern of v1 → v5, the switching is always performed three times from any one of “RTT / TRT / TTR” to “SSS”. In this case, the transition pattern of v1 → v1 is selected. In addition, when v5 is updated, if v5 → v5, “SSS” → “SSS” and the number of times of switching is 0, so this transition pattern (normal update processing) is always selected.

  Next, consider a case where the input sector changes from 2 to 3 (even number sector to odd number sector), and the output sector does not limit where from 1 to 6 shifts.

  When v1 is updated, if the transition pattern is v1 → v1, the transition will be from either “RRT / TRR / RTR” to any one of “SST / TSS / STS”. It becomes. In the transition pattern from v1 to v5, one of “RRR / TRR / RTR” is shifted to “RRR” and the number of times of switching is always one. In this case, the transition pattern from v1 to v5 (switching process at the time of update) Select. Also, when v5 is updated, if v5 → v5, “SSS” → “RRR” and switching is always performed three times. Therefore, the transition pattern of v5 → v1 (switching process at update) “SSS” → “SST / TSS” / STS "is selected, and transition is always performed with one switching.

  Summarizing the above, since it can be expressed as shown in Table 9, when the input sector and the output sector are simultaneously shifted, processing is performed according to the transition pattern of Table 9.

  The upper part of Table 9 indicates that the normal update process of v1 → v1 or v5 → v5 is performed when the output sector is changed and the input sector is changed from the odd sector to the even sector, and the lower part of Table 9 is the output sector. And when the input sector is shifted from the even sector to the odd sector, the switching process at the time of updating v1 → v5 or v5 → v1 is performed.

(Example 5)
In order to avoid the possibility that the transition pattern in which the number of times of switching is 1 or 3 at the time of updating v1 in the fourth embodiment will be three times, a latch process (one control cycle) as in the second embodiment. (Delay processing) is performed, and a transition pattern is executed when v5 is updated. That is, when the input and output shift simultaneously, the processing shown in Table 10 is performed.

  In Table 10, the numbers in parentheses mean the number of switching times. Since the portion marked with X in Table 10 is a mode in which the number of times of switching is 0 or 3, the normal folding pattern v1 → while maintaining the previous sector state without shifting to the sector at this time v1 is performed (for example, v1 → v1 of the same stage in Table 8 is shifted). Then, v1 → v2 → v3 → v4 → v5 in the same stage in Table 8 is switched, and the sector information latch is released at the timing of v5 → v5 generated with a delay of one control cycle, and the transition is made with 0 switching times. Complete the migration in a v5 update pattern that can. However, since the output command value changes suddenly, it is possible to select whether or not to perform the latch processing.

  According to this embodiment, even when the input and output sectors are shifted at the same time, it is possible to always reduce the number of switching to one or less.

(Example 6)
Although the above embodiments have been described for the case of applying to a general virtual indirect space vector modulation method of a matrix converter, the above processing can be similarly performed by a carrier comparison method. For example, as shown in FIG. 6, two carrier triangular wave signals that are 180 degrees out of phase with each other are prepared in advance, and at the time of sector transition, one of the two carrier waves is instantaneously switched from one to the opposite carrier wave. , V1 → v5, v5 → v1, a transition pattern (update switching process) can be formed. In addition, since the latch process (one control cycle delay process) is not limited to the space vector modulation method or the carrier comparison method, the same operation and effect can be realized by the carrier comparison method.

1 is a basic configuration diagram of an AC-AC direct conversion device to which the present invention is applied. FIG. 3 is an equivalent circuit diagram of a virtual DC link type AC-AC direct conversion device. (A) is a space vector diagram on the input virtual rectifier side, and (b) is a space vector diagram of an output virtual inverter. An input current command vector diagram and an output voltage command vector diagram. Explanatory drawing of the example of a definition of the input side sector and output side sector of a space vector. Explanatory drawing of the Example by the carrier comparison system of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Three-phase alternating current power supply, 2 ... Input filter part, 3 ... Semiconductor power converter part, 4 ... Load.

Claims (7)

In the AC-AC direct conversion device having a plurality of bidirectional switches, the space vector duty of the input-side virtual rectifier and the space vector duty of the output-side virtual inverter are combined, and five space vectors are arranged per control cycle. A switching pattern switching method for an AC-AC direct conversion device that generates a plurality of switching patterns and performs PWM control of the bidirectional switch according to the switching patterns,
A region where the input current command value vector and the output voltage command value vector exist, each defined by dividing the input and output side space vector spaces into a plurality, is defined as an output sector, and the input sector and the output sector Define two sector modes from the combination of
AC-, characterized in that, based on the input, output sector, and sector mode, a process for determining a switching pattern for reducing the number of switching is performed, and the bidirectional switch is PWM controlled by the determined switching pattern. Switching pattern switching method for AC direct conversion device. The process for determining the switching pattern includes:
When the switching mode is updated at the timing of the space vector arranged at one end of the generated switching pattern during the transition in which the sector mode does not change and the input sector shifts, the switching for the next PWM control is performed. When shifting to the space vector arranged at the other end of the pattern and updating the switching pattern at the timing of the space vector arranged at the other end of the switching pattern, one end of the switching pattern used for the next PWM control The switching pattern switching method of the AC-AC direct conversion device according to claim 1, wherein a switching process at the time of updating to shift to the arranged space vector is performed. The process for determining the switching pattern includes:
In the mode where the number of times of switching becomes 2 by updating the switching pattern at the transition when the output sector transitions, while maintaining the sector state before the transition, the switching pattern before the updating is turned back and PWM control is performed, and then 2. The control period delay processing for canceling the sector maintenance and performing a transition to a space vector arranged at an end of a switching pattern used for the next PWM control without switching is performed. Switching method of the AC-AC direct conversion device. The process for determining the switching pattern includes:
The switching pattern switching method for an AC-AC direct conversion device according to claim 3, wherein the one control cycle delay process is not performed when two or more output sectors are transferred. The process for determining the switching pattern includes:
During the transition when the output sector transitions and the input sector transitions from odd sector to even sector,
A normal update process for shifting from a space vector arranged at one end of the generated switching pattern to a space vector arranged at the same end of the switching pattern used for the next PWM control. Done
During a transition when the output sector transitions and the input sector transitions from an even sector to an odd sector,
3. The switching pattern switching method for an AC-AC direct conversion device according to claim 1, wherein the switching process at the time of update according to claim 2 is performed. The process for determining the switching pattern includes:
In the mode in which the output sector transitions and the input sector transitions from an odd sector to an even sector, and in a mode in which the number of switching is three by updating the switching pattern, the claim is replaced with the normal update process. 6. The switching pattern switching method for an AC-AC direct conversion device according to claim 5, wherein the one control cycle delay process according to claim 3 is performed.   Of the switching patterns, the duty of the vector of the switching pattern before the update is compared with the first carrier wave, and the duty of the vector of the switching pattern used for the next PWM control is 180.degree. 7. The AC-AC direct conversion device according to claim 1, wherein a switching signal for performing the PWM control is obtained in comparison with a second carrier wave whose phase is shifted by a predetermined degree. Switching pattern switching method.

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