JP4893152B2 - Space vector modulation 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, a space vector whose size and phase change from moment to moment. The present invention relates to a space vector modulation method that expresses each input / output and selects a basic vector to be used and calculates a duty.

  This type of AC-AC direct conversion device that has existed in the past switches a bidirectional switch using a self-extinguishing semiconductor element at high speed, and converts a single-phase or multi-phase AC input to power of an arbitrary voltage or frequency. FIG. 1 shows a basic configuration of a conversion device for conversion. An input filter (InputFilter) 2 and an AC-AC direct conversion circuit 3 having bidirectional switches S1 to S9 are inserted in the R, S, and T phases of the three-phase AC power source 1, and both are controlled by a controller (controller) 4. By performing PWM control of the direction switch at a frequency sufficiently higher than the power supply frequency, an AC output of U, V, and W controlled to an arbitrary voltage or frequency is obtained while directly applying an input voltage to a load Load such as a motor. The bidirectional switch may be configured by using a plurality of unidirectional switches as shown in the figure.

  Here, the control method of the AC-AC direct conversion device is roughly divided into two systems, a virtual DC link type (indirect conversion method) and a direct AC-AC conversion type. The virtual DC link system is devised so that the virtual input converter and the virtual output inverter can be controlled independently considering a virtual DC link, and is similar to the configuration of a conventional current source PWM converter + voltage source PWM inverter. , The idea of control becomes easier. On the other hand, there is a constraint that six switching patterns in which the phases on the input side and the output side are all 1: 1 and are connected to different phases do not occur. In the direct AC-AC conversion type, there is no restriction on the above switching pattern.

  In addition, as a modulation method for generating a switching pattern for PWM control, there are mainly a carrier comparison method and a space vector method. The carrier comparison method generates a switching pattern by comparing the size of a triangular wave carrier and a sine wave. As a carrier comparison method applied to the virtual DC link method, a virtual inverter carrier is generated from a virtual converter carrier and a virtual PWM pulse. Thus, there has been proposed a technique in which the number of times of PWM control switching is reduced to the same number to reduce switching loss and noise and improve the output voltage control accuracy (see, for example, Patent Document 1).

  This is an AC-AC direct conversion device that uses a virtual DC link type modulation method based on carrier comparison, and adjusts the magnitude of the output voltage by controlling the magnitude of the virtual DC voltage of the virtual converter using the PAM (Pulse Amplitude Modulation) method. In the virtual inverter, a method of controlling only the output frequency has also been proposed (for example, see Non-Patent Document 1). In this control method, when the output voltage is in a low output region, a pulse with a small voltage height difference is used, so that the pulse width can be made wider than a pulse with a large voltage height difference. Also, the common mode voltage varies with reference to the input intermediate phase voltage. As a result, harmonics of the output voltage and common mode voltage can be reduced.

  The space vector method is a method of selecting an instantaneous space vector according to the output voltage command value of the AC-AC direct conversion device, and the switching pattern is determined by this selection. An AC-AC converter that employs this space vector method has also been proposed (see, for example, Non-Patent Document 2). In this space vector method, a harmonic vector is selected by combining the rotation vector, maximum single vibration vector, and zero vector so as to approach the command value locus of the magnetic flux linkage number vector integrated over time. An output voltage waveform with a small component can be obtained, and magnetic noise and torque ripple when driving an induction motor can be reduced during high voltage output.

Furthermore, although the modulation method is not a space vector, the direct current AC / AC conversion type AC-AC direct conversion device reduces the waveform distortion by appropriately selecting 27 switching patterns using the space vector ( For example, refer nonpatent literature 3).
JP 2005-168198 A PAM control method of matrix converter based on virtual AC / DC / AC conversion system, 2005 IEEJ Industrial Application Conference, 1-43, 1-203-1-206 Akio Ishiguro, Takeshi Furuhashi, Muneaki Ishida, Shigeru Okuma, Yoshiki Uchikawa: “Method of controlling the output voltage of a PWM controlled cycloconverter using a space vector”, Electrical Theory D, Vol. 110, no. 6, pp. 655-663 (1990) P. Mutschler, M.M. Marks: “A Direct Control Method for Matrix Converters” IEEE trans. on Industrial Electronics. Vol 49, No. 2, p362- (2002)

  For example, in Patent Document 1 and Non-Patent Document 1, the modulation method is the carrier comparison method, which improves the control accuracy of the output voltage, or reduces the harmonics of the output voltage or the common mode voltage. The process of generating a switching pattern is different in the space vector method in which the transition of the size can be grasped by the behavior of the space vector, and cannot be applied.

  In Non-Patent Document 2, although the output voltage harmonics can be reduced and the torque ripple of the motor load at high output can be reduced, the input current cannot be controlled to an arbitrary sine wave. The waves become very big. Therefore, this method is limited to applications where the input is not connected to the system power supply. Also, the output voltage error and the common mode voltage cannot be reduced in the low output region.

  On the other hand, although Non-Patent Document 3 uses direct torque control / direct power control / switching control rule, etc., it is necessary to detect not only the output current but also the input current in order to perform direct switching control of the input / output current. In addition, there are switching patterns in which the voltage error and phase difference of the basic vector become large. In this case, the control becomes slow, the number of times of switching and the switching sequence are wasted, and it is not suitable for high-speed control, and the low output area Output voltage error and common mode voltage cannot be reduced.

  The object of the present invention is a modulation method using a space vector method, which is different from the carrier comparison method and the process of generating a switching pattern, and can reduce output voltage error, harmonics of input / output voltage, and common mode voltage. Another object of the present invention is to provide a space vector modulation method for an AC-AC direct conversion device capable of suppressing pulsation of input and output magnetic flux vectors.

  The present invention for solving the above problems is characterized by the following method.

(1) A space vector modulation method for an AC-AC direct conversion device that PWM-controls a bidirectional switch of an AC-AC direct converter from a multiphase AC power supply by modulation using a direct AC / AC conversion type space vector,
The state of the vector in which the line voltage of the polyphase AC output is expanded on the two-phase stationary αβ axis, the single vibration vector axis in which the phase of the sector where the line voltage command value vector Vo * exists is delayed on the X axis, The advancing single vibration vector axis is defined as the Y axis, and the maximum vectors VXmax and VYmax, the intermediate vectors VXmid and VYmid, the minimum vectors VXmin and VYmin, and the intermediate voltages of the phase voltages are defined on the respective axes. The zero vector Vz and one rotation vector Vrot existing in the sector are set as basic vectors, and the eight basic vectors divide the sector into eight regions D1 to D8.
The three basic vectors used for PWM control are determined depending on which of the regions D1 to D8 the line voltage command value vector Vo * is in, and the three basic vectors are determined from the line voltage command vector value Vo *. The duty of a vector is determined and used as a space vector.

  (2) The basic vector is always determined using a vector having a phase difference of 60 degrees or less and an instantaneous basic vector close to the magnitude of the line voltage command value vector Vo *.

  (3) As a basic vector switching state transition condition for determining each of the regions D1 to D8, <condition 1> switching for each output phase, <condition 2> no direct commutation between the input maximum phase and the minimum phase. <Condition 3> Space vectors D4 to D7 that do not have a transition pattern that can satisfy each condition for reducing the common mode voltage are collectively configured using the above three types of vectors VXmid, VYmid, and Vz. It is characterized by.

  (4) Regions D2, D3, and D5 in which there are no transition patterns that can clear the condition that there is no direct commutation between the input maximum phase and the minimum phase as the switching state transition conditions of the basic vectors that determine the regions D1 to D8. Of these, the regions D2 and D3 are integrated to select another basic vector using the rotation vector, and the region D5 is used to select another basic vector using the rotation vector.

  As described above, according to the present invention, a direct AC-AC conversion type AC-AC direct conversion apparatus using a space vector modulation method can reduce output voltage error, reduce harmonics of input / output voltage, and common mode voltage. Can be reduced, or the pulsation of the input / output magnetic flux vector can be suppressed.

The three-phase input and three-phase output AC-AC direct conversion device shown in FIG. 1 will be described as an example. Considering the switching condition that does not cause short circuit of the input power supply and discontinuity of the output current, the nine bidirectional switches are limited to the combination of 27 (3 ³ ) patterns shown in Table 1.

  In Table 1, each vector (hereinafter referred to as a basic vector) existing on a space vector will be described. S1, S2, and S3 are groups of simple vibration vectors that are switched using only two phases out of three phases, R1. Is a group of counterclockwise rotation vectors, R2 is a group of clockwise rotation vectors, and Z is a group of zero vectors whose output voltage is always zero.

  Therefore, in order to operate the AC-AC direct conversion device of FIG. 1 normally, it is necessary to select and control an arbitrary state from the 27 patterns. Therefore, when these 27 switching patterns are developed on a stationary αβ axis of two phases from three-phase AC by three-phase / two-phase conversion, the space vector of the output voltage can be expressed as shown in FIG. Example of phase voltage phase θ = 15 degrees), a modulation method using a direct AC-AC conversion type space vector applied to the present invention will be briefly described below. .

  With reference to the line voltage Vuv between the outputs UV of the AC-AC direct conversion device as a stationary α-axis direction, a space vector of the output voltage as shown in FIG. 2 is constructed. FIG. 2 shows an example in which the input phase voltage phase θ is 15 degrees. In the AC-AC direct conversion device, 27 basic vectors fluctuate depending on the phase state and magnitude of the instantaneous input voltage, and the input voltage is three-phase AC. In the case of a power supply, the space vector also fluctuates in synchronization with the power supply frequency (for example, 50 Hz / 60 Hz). This point is different from normal inverter control (the space vector used in the normal inverter is a hexagon having a fixed length and phase because the input voltage is DC).

  Further, in the method of virtually controlling the direct current link in the alternating current to alternating current direct conversion device, it can be considered separately from the virtual converter and the virtual inverter, so the hexagonal fixed length is individually set on the input side and the output side. A fixed phase space vector can be used. Therefore, although the control is simplified and facilitated as before, the virtual DC link needs to connect the input phase and the output phase with virtually two lines, so all three input phases and three output phases are used. The connection states (six switching states of STATEs 19 to 24 in Table 1) cannot be expressed. Therefore, in the present invention, in order to make effective use of these six switching states, control is considered by a direct AC / AC conversion type modulation method using a space vector.

The basic vectors described above are divided into six groups as shown in Table 1, and the group of simple vibration vectors with the phase angle of 30 degrees as the positive axis is the simple vibration vector S1, and the phase angle of 150 degrees as the positive axis. A single vibration vector S2, a single vibration vector S3 having a phase angle of 270 degrees as a positive axis, a rotation vector R1 having a maximum length and rotating counterclockwise, and a rotation vector R2 having a constant length and rotating clockwise And the zero vector Z fixed at the hexagonal center zero, divided into the above six groups. Each of these basic vectors depends on the phase θ of the input voltage, that is, varies in synchronization with the angular velocity ω _{i of the} input voltage. The length of the vector (hexagonal size) corresponds to the magnitude of the input line voltage.

On the other hand, the space vector of the input current can be defined in the same way. FIG. 3 shows a space vector of the input current when the output current phase φ = 15 degrees, and the input R-phase current is based on the stationary α axis. AC-AC direct conversion devices (such as matrix converters that control switching of switches at a frequency sufficiently higher than the power supply frequency) perform output voltage control in the manner of a voltage-type inverter that performs PWM control by chopping up the input voltage. The control is similar to a current source converter that performs PWM control by chopping an output current (load current) assuming an inductive load. Accordingly, the space vector of the input current is expressed by a basic vector that varies depending on the output current phase φ, that is, the angular velocity ω _{o of the} output current. Further, the length of the vector depends on the load (the magnitude of the output current) at that time.

  Here, attention is paid to the difference between the space vector of the output voltage in FIG. 2 and the space vector of the input current in FIG. The grouping shown in Table 1 corresponds to the types of basic vectors forming the output voltage space vector of FIG. 2, and does not correspond to the input current of FIG. FIG. 4 shows an example in which the space vector (left) of the input current is compared with the space vector (right) of the output voltage (when the input voltage phase θ = 15 degrees and the output current phase φ = 15 degrees). The group of basic vectors that oscillate with the output voltage space vector in FIG. 4B is expanded into the same length of the basic vector in the input current space vector in FIG. 4A. In the load condition / phase condition of FIG. 4, the simple vector S1 axis in the direction of 30 degrees in the basic vector of the output voltage is expanded to the maximum length basic vector in each of the six directions on the input side (see FIG. 4). IRTT, iSTT, iSRR, iTRR, iTSS, iRSS). The rotation vector is represented by a fixed-length vector as in the output side although it rotates according to the output current phase and the axis reference is shifted.

  A direct AC-AC conversion type space vector modulation system according to an embodiment of the present invention will be described below.

(Embodiment 1)
Based on the above-described conventional direct AC / AC conversion type space vector modulation system, a technique giving the highest priority to error reduction in output voltage will be described below.

  FIG. 5 shows a sector defined for a space vector of a direct AC / AC conversion type output voltage. Here, the case where the output line voltage command vector exists in the output sector “1” (phase −30 degrees to +30 degrees) in the drawing will be described as an example. FIG. 6 is an enlarged view showing the state of the basic vector (single vibration vector, rotation vector, and zero vector) in the output sector “1”. In FIG. 6, a single vibration vector axis whose phase is delayed assuming that the phase advances counterclockwise is defined as an X axis, and a single vibration vector axis which is advanced is defined as a Y axis. The subscript is max, the middle one is mid, and the minimum is min (VXmax, VXmid, VXmin, VYmax, VYmid, VYmin). For the purpose of reducing the common mode voltage, the zero vector Vz uses a phase that is an intermediate voltage of the input phase voltage (for example, the instantaneous value relationship of the three-phase input phase voltage is Vr (R phase voltage)> Vs (S When phase voltage)> Vt (T phase voltage), zero vector Sz using S phase is used as zero vector Vz (STATE 26 in Table 1 is used).

  Moreover, in the space vector of the output voltage by the direct AC-AC conversion type, the rotation vector Vrot always exists in each sector one by one in any situation. Of the 27 switching patterns shown in Table 1, one of the eight basic vectors (VXmax, VXmid, VXmin, VYmax, VYmid, VYmin, Vrot, Vz) is applied depending on the phase of the input voltage. become.

  In Non-Patent Document 2, as a method that can reduce the phase difference between the voltage command value vector Vo * and the basic vector to be used most, three types of a single phase of a vibration vector (VXmax or VYmax), a rotation vector Vrot, and a zero vector Vz are used. Use to modulate. Note that VXmax and VYmax are selected by comparing the phase of Vrot with the phase of the voltage command value vector Vo *. When Vo * is advanced in the counterclockwise direction, VYmax is selected. When V * max is delayed, VXmax is selected. Have chosen to use. In other words, by always using a basic vector having a phase difference smaller than 60 degrees, the adverse effect on the motor magnetic flux vector locus = torque pulsation can be reduced as much as possible.

  On the other hand, in this embodiment, the space vector is modulated using three basic vectors out of eight, and paying attention to the voltage drop of the PWM pulse to be output, the harmonic reduction of the output line voltage is given top priority. Yes.

  Assume that a voltage command value vector Vo * and a basic vector state as shown in FIG. 7 are given. In the method of Non-Patent Document 2, PWM control is performed using three basic vectors VXmax, Vrot, and Vz in the state of FIG. 7, but in this embodiment, the region indicated by the hatched portion in FIG. It is determined that the command value exists, and PWM control is performed using VXmax, Vrot, and VXmid.

  In the conventional method of Non-Patent Document 2, the magnitude of the voltage command value Vo * is a large drop with respect to Vz (that is, zero voltage), and the PWM pulse is also narrow and high. The output time of such a pulse is reduced due to the influence of the dead time, and it is likely to cause a voltage error. Further, since the pulse has a high peak value, the harmonics also increase.

  On the other hand, in the method of the present embodiment, instead of Vz having a large voltage drop with respect to the command value, VXmid whose voltage value is close to the voltage command value vector Vo * is used. The voltage error can be reduced as much as possible, and the peak value can be kept low, so that the harmonics of the output voltage can be minimized.

  FIG. 8 shows a state in which the areas D1 to D8 in the sector are divided using the method of the present embodiment (example of output sector “1”). When selecting three basic vectors, the highest priority is given to the reduction of voltage error from the voltage command value vector Vo *.

  FIG. 9 is an example of a flowchart for determining the regions D1 to D8 in FIG. First, a component Vo * x that decomposes the voltage command value vector Vo * in the X-axis direction and a component Vo * y that decomposes in the Y-axis direction are obtained from the voltage command value and phase information thereof. Since the line connecting VXmid and VYmid can be expressed as in equation (1) -A, it can be divided into regions by determining whether the value on the left side is larger or smaller than 1. That is, when the value on the left side is larger than 1, it is one of the regions D1 to D3, and when it is smaller than 1, it can be recognized as one of the regions D4 to D8.

  Hereinafter, in accordance with FIG. 9, when the formula (1) -B is established and the phase of the voltage command value vector Vo * is smaller than the rotation vector Vrot phase, the voltage command value vector Vo * is changed to the X axis direction and the R axis direction (R axis). : The axis based on the phase of the rotation vector Vrot) (1) If the condition -C is established, the area D2, if not, the area D3, if not, the voltage command value vector Vo * is equal to or larger than the Y-axis direction. If the expression (1) -D is established by dividing in the R-axis direction, the area D1 is not established, and the area D3, (1) -B is not established and the (1) -E expression is established. Region D5 if D8, (1) -H equation is not established and the phase of voltage command value vector Vo * is close to the X axis and equation (1) -F or (1) -G is established, region D5 D7, near the Y axis of the voltage command value vector Vo * (1) -H It is (1) if -I equation satisfied region D4, does not hold area D6, and the can divided into regions of D1 to D8. When this area division is completed, three basic vectors to be automatically used are determined. Table 2 summarizes the regions and the vectors used.

  When the three basic vectors to be used are determined according to Table 2, their duties are calculated. Considering a triangle composed of three basic vectors, it can be obtained by using a trigonometric formula or by calculating an inverse matrix. Here, as an example, a method of inverse matrix calculation is described.

  The voltage command value vector Vo * and the simple vibration vectors VXmax, VXmid, VXmin, VYmax, VYmid, VYmin, the rotation vector Vrot, and the zero vector Vz are each decomposed into values on the stationary αβ axis, and α and β are added to the subscripts. . For example, when the voltage command value vector Vo * is in the region D3, since three types of VXmid, VYmid, and Vrot are used from Table 2, the matrix equation shown in Equation (2) is established. (The duty of VXmid is d1, the duty of VYmid is d2, and the duty of Vrot is d3.)

  Since the solutions to be obtained are the duties d1, d2, and d3, they can be solved using an inverse matrix such as the equation (3).

  The above is the description of the process up to the duty calculation in the first embodiment. By selecting and using a basic vector close to the magnitude of the voltage command value, the output line voltage is compared with the method of Non-Patent Document 2. The voltage error of the PWM pulse can be reduced.

  In addition, the dead time (commutation time for switching the semiconductor switch) leads to reduction of voltage error due to lack of pulse output time. This is because the use of a basic vector having an instantaneous value similar to the voltage command value reduces the PWM pulse height and widens the PWM pulse width.

(Embodiment 2)
The first embodiment is a means for performing space vector modulation by reducing the voltage drop of the PWM pulse of the output line voltage to the maximum, but the phase difference of the basic vector used at that time is excluding the regions D1 and D2 in FIG. , A basic vector having a phase difference of 60 degrees is used. Such a phase difference state of the basic vectors affects the pulsation of the motor magnetic flux linkage number vector locus described in Non-Patent Document 2, that is, motor torque ripple and noise. As in the regions D1 and D2 in FIG. 8, in order to always construct a space vector with a basic vector having a phase difference of 60 degrees or less, either the X axis or the Y axis of the simple vibration vector is used while always using the rotation vector Vrot. Only one needs to be used. Based on the above, the areas can be divided as shown in FIG.

  In this embodiment, by performing space vector modulation based on the regions D1 to D6 shown in FIG. 10, a voltage command value vector Vo is used so that a vector having a phase difference of 60 degrees or less is always used and a voltage drop can be reduced as much as possible. Select a basic vector of instantaneous values close to *. The region D1 to D6 division process is shown in a decision flowchart in FIG.

  In the present embodiment, by always using a basic vector having a phase difference of 60 degrees or less, the pulsation of the flux linkage vector such as a motor load is reduced, and the magnitude of the voltage command value vector Vo * is less than the phase difference of 60 degrees. By using a basic vector close to the above, it is possible to reduce the voltage error.

(Embodiment 3)
Regarding the method of the first embodiment, focusing on the reduction of the number of switching times, consider the transition of the switching pattern of the basic vector in each region. The voltage command value vector Vo * is in the sector “1”, and the region division state as shown in FIG. 12 is taken as an example. As an element that determines the transition of the switching pattern,
<Condition 1> Switching for each output phase (Example: uvw: RTT → uvw: RSS is not possible because V phase and W phase are switched from T to S at the same time)
<Condition 2> There is no direct commutation between the maximum phase and the minimum phase of the input phase voltage. (Example: When the phase relationship of the input phase voltage is R>S> T, the intermediate phase is the S phase. Cannot be switched)
<Condition 3> Reduce common mode voltage (use zero vector composed of intermediate phase of input phase voltage, SSS if R>S> T)
The control is the above three conditions. Table 3 is an example of transition of the switching pattern in consideration of the above-described constraint conditions in each of the regions D1 to D8 in FIG. In the regions D4 to D7, there is no transition pattern that can clear the constraint condition, and the simultaneous switching of two or more phases is inevitably caused, resulting in an increase in the number of switching times and loss.

  Therefore, in this embodiment, the regions D4 to D7 do not use the STT and STS (VXmin and VYmin) in FIG. 12, and the regions D4 to D7 are collectively used as three basic vectors VXmid, VYmid, and Vz. To form a space vector. The area division at this time is as shown in FIG.

  By applying this embodiment, there is a region where the voltage error is larger than in the first embodiment, but since switching can be performed with an optimal pattern, the number of switching can be reduced, and the common mode voltage can be reduced. Thus, commutation with a large voltage drop can be prevented. Thereby, it is possible to reduce loss due to switching, reduce generated noise, suppress insulation deterioration, and suppress harmonics.

(Embodiment 4)
With regard to the method of the second embodiment as well, the transition of the basic vector switching pattern in each region is considered by focusing on the reduction in the number of switching times. The voltage command value vector Vo * is in the sector “1”, and description will be made by taking an example of the region division state as shown in FIG. As in the third embodiment, when the switching for each phase and the direct commutation prevention between the maximum phase and the minimum phase of the input voltage are set as the constraint conditions, the switching patterns of the respective regions in FIG.

  In this example, since there is no switching pattern that can clear the condition in the areas D2, D3, and D5, the area division is changed as follows.

  The regions D2 and D3 are integrated and switched in the order of RTS → RSS → SSS or SSS → RSS → RTS using the RSS, RTS, and SSS vectors.

  In the region D5, switching is performed in the order of RTR → RTS → STS or STS → RTS → RTR using vectors of RTS, RTR, and STS.

  As described above, switching is optimized by selecting another basic vector that satisfies the constraint conditions while using the rotation vector (RTS).

  According to the present embodiment, the number of switching times is reduced as compared with the method of the second embodiment, and the pulsation of the flux linkage vector locus is reduced as much as possible by always using a basic vector having a phase difference of 60 degrees or less so that Flow can be prevented. This makes it possible to reduce loss, reduce generated noise, suppress insulation deterioration, and suppress harmonics.

The basic block diagram of an alternating current-alternating current direct conversion apparatus. The basic space vector diagram of output voltage. The basic space vector diagram of input current. Input side space vector diagram (a) and output side space vector diagram (b). An example of defining the “output” sector of a space vector. The state diagram of the basic space vector in the output sector “1”. Voltage command value vector and basic voltage vector state diagram. An example of areas D1 to D8 in a sector. The example of the determination flowchart of area | region D1-D8. An example of area division within a sector. The example of the determination flowchart of area | region D1-D6. An example of dividing the areas D1 to D8 in the sector. An example of area division within a sector. An example of dividing the areas D1 to D8 in the sector.

Explanation of symbols

1 AC power supply 2 Input LC filter 3 AC-AC direct conversion circuit 4 Control device

Claims (4)

A space vector modulation method for an AC-AC direct conversion device that PWM-controls a bidirectional switch of an AC-AC direct converter from a polyphase AC power source by modulation with a direct AC / AC conversion type space vector,
The state of the vector in which the line voltage of the polyphase AC output is expanded on the two-phase stationary αβ axis, the single vibration vector axis in which the phase of the sector where the line voltage command value vector Vo * exists is delayed on the X axis, The advancing single vibration vector axis is defined as the Y axis, and the maximum vectors VXmax and VYmax, the intermediate vectors VXmid and VYmid, the minimum vectors VXmin and VYmin, and the intermediate voltages of the phase voltages are defined on the respective axes. The zero vector Vz and one rotation vector Vrot existing in the sector are set as basic vectors, and the eight basic vectors divide the sector into eight regions D1 to D8.
The three basic vectors used for PWM control are determined depending on which of the regions D1 to D8 the line voltage command value vector Vo * is in, and the three basic vectors are determined from the line voltage command vector value Vo *. A space vector modulation method for an AC-AC direct conversion device, characterized in that a vector duty is determined to be a space vector.   2. The basic vector is determined using a vector having a phase difference of 60 degrees or less at all times, and an instantaneous basic vector close to the magnitude of the line voltage command value vector Vo *. Vector-to-AC direct conversion device space vector modulation method.   As a switching state transition condition of the basic vector for determining each of the regions D1 to D8, <condition 1> switching for each output phase, <condition 2> no direct commutation between the input maximum phase and the minimum phase, <condition 3> A space vector is configured by collectively using the three types of vectors VXmid, VYmid, and Vz in regions D4 to D7 that do not have transition patterns that can satisfy each condition for reducing the common mode voltage. A space vector modulation method for an AC-AC direct conversion device according to claim 1. Among the regions D2, D3, and D5 in which there is no transition pattern that can clear the condition that there is no direct commutation between the input maximum phase and the minimum phase as the switching state transition condition of the basic vector that determines each of the regions D1 to D8, 2. The region D2 and D3 are integrated to select another basic vector using the rotation vector, and the region D5 is used to select another basic vector using the rotation vector. Vector-to-AC direct conversion device space vector modulation method.

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