JP2008048529A - Spatial vector modulation method of ac-ac direct converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control input and output waveforms to sine waves while reducing a common mode voltage and harmonics of input and output voltages and suppressing pulsation. <P>SOLUTION: The PWM control of a bi-directional switch of a three-phase/three-phase AC-DC direct converter 3 is performed by a direct AC-AC conversion type spatial vector modulation method. The state of a basic vector obtained by developing a line voltage of a three-phase AC output on a two-phase static αβ axis is four simple oscillation vectors VXmax, VXmid, VYmax and VYmid and one zero vector Vz, and the duty is determined from input current command values Iiα*, Iiβ*, output line voltage command values Volα*, Volβ*, and an input voltage detection value Vi and an output current detection value Io developed on the static αβ axis. The selection of three simple oscillation vectors, a zero vector Vz and a rotation vector Vrot, and the selection of two rotation vectors, a zero vector Vz and two simple oscillation vectors inserted between two rotation vectors are also included. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 common mode voltage cannot be reduced.

  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 is slow, the number of times of switching and the switching sequence are wasted, and it is not suitable for high-speed control. Cannot be reduced.

  The object of the present invention is a modulation method using a space vector method in which a process for generating a switching pattern is different from that of a carrier comparison method, and can reduce harmonics of an input / output voltage and a common mode voltage, or an input / output magnetic flux. An 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 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 among these, four simple vibration vectors VXmax, VXmid, VYmax, VYmid and one zero vector Vz are selected.
The selected five basic vectors, the input current command value Ii * and the output line voltage command value Vol * on the stationary αβ axis, are input current command values Iiα * and Iiβ *, and the output line voltage command value Volα *. , Volβ *, the input voltage detection value Vi, and the output current detection value Io, the duty of the five basic vectors is obtained and the input and output waveforms are simultaneously converted into a sine wave.

(2) 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 supply by modulation using a direct AC / AC conversion type space vector,
The vector state 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 vector Vo * exists is delayed, and the X axis advance The simple 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 zero that is the intermediate voltage of the phase voltages. A vector Vz and a rotation vector Vrot that exists in one sector are set as basic vectors, and three simple vibration vectors, zero vector Vz, and rotation vector Vrot are selected among them.
The selected five basic vectors, the input current command value Ii * and the output line voltage command value Vol * on the stationary αβ axis, are input current command values Iiα * and Iiβ *, and the output line voltage command value Volα *. , Volβ *, the input voltage detection value Vi, and the output current detection value Io, the duty of the five basic vectors is obtained and the input and output waveforms are simultaneously converted into a sine wave.

(3) 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 vector state 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 vector Vo * exists is delayed, and the X axis advance The simple 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 zero that is the intermediate voltage of the phase voltages. A vector Vz and one rotation vector Vrot existing in the sector are set as basic vectors, and two rotation vectors, a zero vector Vz, and two simple vibration vectors sandwiched between two rotation vectors are selected. ,
The selected five basic vectors, the input current command value Ii * and the output line voltage command value Vol * on the stationary αβ axis, are input current command values Iiα * and Iiβ *, and the output line voltage command value Volα *. , Volβ *, the input voltage detection value Vi, and the output current detection value Io, the duty of the five basic vectors is obtained and the input and output waveforms are simultaneously converted into a sine wave.

  (4) In the switching state of the selected five basic vectors, a switch switching transition pattern is determined so that the number of switching times is minimized.

  (5) In the switching state of the selected five basic vectors, the switch switching transition pattern is determined so as to prevent the direct commutation between the maximum phase and the minimum phase while minimizing the number of times of switching.

  (6) The duty is calculated using a Moore-Penrose generalized inverse matrix.

  (7) For the calculation of the duty, a valid solution can be obtained when the solution of the generalized inverse matrix of Moore-Penrose is negative or when the added value of the duty of the five basic vectors is not 1. The selection of the basic vector is switched until it is determined.

  (8) The duty calculation is characterized in that a solution of the Moore-Penrose generalized inverse matrix is developed in advance in a table to reduce a calculation load.

  (9) The duty is calculated by calculating the input current command value Iiα * by a coefficient comparison between the output current detection value Io and the input current command values Iiα * and Iiβ * instead of the output current detection value Io. , Iiβ * is obtained.

  As described above, according to the present invention, the input / output waveform can be controlled to a sine wave, an output current sensor or the like is not required, and the calculation load can be reduced. Further, the harmonic switching of the input / output voltage, the common mode voltage, and the pulsation can be suppressed by the optimized switching of the bidirectional switch.

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)
When a technique such as Non-Patent Document 2 is used to control the improvement of the output line voltage waveform and the switching frequency and the common mode voltage, the input current is a sine wave although the harmonics are suppressed by the switching frequency reduction. If it is a grid interconnection system, it will adversely affect the power system. Therefore, the method is limited to an application that is not a grid-connected system or a system that requires some device that reduces harmonics separately.

  In the present embodiment, a method is proposed in which the input and output waveforms are simultaneously converted to a sine wave by a direct AC / AC conversion type space vector modulation method.

  In Non-Patent Document 2, only the output is subjected to space vector modulation using three basic vectors. By adjusting the basic vectors of the three output voltages, the components of the output voltage in the static α-axis direction and β-axis direction are extracted, and the pulse output time (duty addition value) of the three basic vectors is equal to the calculation cycle time T. It is controlled to become.

  On the other hand, in order to control the input current, two degrees of freedom for controlling the α-axis direction and the β-axis direction on the input side are further necessary. Therefore, in order to arbitrarily control both input and output waveforms, it is necessary to control a total of five basic vectors. In the definition of sector division of the input and output space vectors shown in FIG. 5, the sector where the input phase command value θIi * exists is “1”, and the sector where the output line voltage command value Vol * exists is “1”. This will be described below as a representative example.

  FIG. 6 defines a total of eight simple vibration vectors, rotation vectors, and zero vectors for the output-side space vector sector “1”. As shown in the figure, a single vibration vector X axis and a Y axis are defined, and a rotation vector direction axis is an R axis. With respect to the X axis and the Y axis, there are three vectors in one sector, so the subscripts of max, mid, and min are given in descending order of instantaneous values (VXmax, VXmid, VXmin, VYmax, VYmid, VYmin). Only one rotation vector direction axis (R axis) exists in one sector, and is set as a rotation vector Vrot. The zero vector Vz is expressed using an intermediate phase of the input phase voltage (for example, if the relationship of the magnitude of the input phase voltage is a relationship of R> S> T, the switching of Table 1 is performed because the S phase is the intermediate phase). State Z2: The connection state of the bidirectional switch uses SSS, and the intermediate phase used for the zero vector Vz is determined by the area of the input sector “1-12” where the input phase command value θIi * exists (input sector 3, 4, 9, 10 → RRR, 1, 2, 7, 8 → SSS, 5, 6, 11, 12 → TTT). By setting the intermediate phase of the input phase voltage to the zero vector Vz, the phase that is the voltage reference for the waveform control on the output side is always the intermediate phase, so that the common mode voltage can be reduced. In addition, for the simple vibration vector and the rotation vector, the switching state and the magnitude / phase of the vector are determined from the input sector region where the input phase command value θIi * exists and its phase state.

Incidentally, in order to convert the input / output waveform into a sine wave, it is necessary to select five out of the eight basic vectors defined in FIG. 6 and perform space vector modulation. There are ₈ C ₅ = 56 patterns of basic vector selection patterns within one sector, and modulation control is performed by selecting a basic vector from among these so that the input / output waveform is a sine wave.

  In the present embodiment, five basic vectors VXmax, VXmid, VYmax, VYmid, and zero vector Vo * Vz are always used as the selection method of the five basic vectors. Since this method is composed of only four single vibration vectors having a good voltage utilization rate and zero vector without using the rotation vector Vrot, as a result, as in the conventional virtual DC link type space vector modulation method, A vibration vector and one zero vector. FIG. 7 shows an input / output basic vector selection state of this embodiment, taking as an example the case of the input phase voltage phase θ = 15 degrees and the output current phase φ = 15 degrees (each input / output command is , In the sector area indicated by diagonal lines). On both the input side and the output side, there are five basic vectors in a space within a phase difference of 60 degrees across the command value vector (voltage command value vector Vo * and input phase command value θIi *) region.

  The space vector duty calculation (space vector modulation) using the five basic vectors selected as described above can be calculated by a geometrically solving method using a triangular formula or the like, or a method of calculating an inverse matrix.

  Hereinafter, a method for calculating an inverse matrix will be described as an example of the duty calculation. As described above, after selecting the five basic vectors, Iiα * and Iiβ * obtained by expanding the input current command value Ii * on the static αβ axis of the input side space vector are given, and the output line voltage command value Vo * is obtained. The output gives Vol α * and Vol β * expanded on the static αβ axis of the space vector. For convenience, the five basic vectors “VXmax, VXmid, VYmax, VYmid, Vz” are “V1, V2, V3, V4, V5” on the output side and “I1, I2, I3, I4, I5” on the input side. Redefine (example: Fig. 8). For each input / output, the five basic vectors are decomposed into stationary αβ axes, and “I1α, I2α, I3α, I4α, I5α”, “I1β, I2β, I3β, I4β, I5β”, “V1α, V2α, V3α, V4α, V5α. “V1β, V2β, V3β, V4β, V5β”. The duty of the five basic vectors to be obtained is “d1, d2, d3, d4, d5”, and these added values are d1 + d2 + d3 + d4 + d5 = 1. Therefore, the equation (1) can be derived from the above.

  Here, the output line voltage command value Vol * may be arbitrarily given according to the load to be driven, but the input current command value Ii * is output in accordance with the principle of the AC-AC direct conversion device. It depends on the load current to be determined. Therefore, the magnitude of the input current command value Ii * cannot be controlled independently of the magnitude of the output voltage command value Vol *. Therefore, the input phase command θ *, which is the relationship that the three-phase instantaneous active power between the input and output of the AC-AC direct conversion device is equal, and the difference of the input current phase with respect to the input phase voltage phase (θIi−θVi) is input side. From the conditions for adjusting the reactive power of, simultaneous equations relating to Iiα * and Iiβ * are derived as in equation (2).

  Vi is an input phase voltage detection value, Vo * is an output voltage command phase voltage, and Io is an output current detection value, which are converted into αβ-axis components.

  Solving equation (2) yields equation (3). Using information on input phase voltage detection value Vi, output line voltage command value Vol *, and output current detection value Io, the left side of equation (1) Iiα * and Iiβ * can be calculated computationally.

  Vil is an input line voltage.

  From the above procedure, the duties d1 to d5 of the five basic vectors can be obtained as shown in equation (4) by calculating the inverse matrix of equation (1).

  In this embodiment, a direct AC-AC conversion type space-vector-modulation AC-AC direct conversion device is provided by means for determining five basic vectors and calculating a duty (space vector modulation) by the above-described procedure. With this, both input and output waveforms can be controlled to sine waves simultaneously. Although the control block of the control apparatus 4 in this embodiment is shown in FIG. 9, the control block which is not related to this control content itself, such as commutation control, is abbreviate | omitted.

(Embodiment 2)
In the present embodiment, a method is proposed in which any five basic vectors are selected as in the first embodiment, and the input / output waveform can be controlled to a sine wave without using the output current detection value Io. That is, only the input phase voltage detection value Vi is used, and the output is open loop control.

  The procedure up to the duty calculation is the same as that in the first embodiment, except that the output current detection values Ioα and Ioβ in the equation (3) are not used. First, “I1α, I2α, I3α, I4α, I5α” and “I1β, I2β, I3β, I4β, I5β” in the coefficient matrix of the equation (1) are all converted into relational expressions of Ioα and Ioβ, and the coefficients are compared. Hereinafter, the switching state (I1 = RSS, I2 = RSR, I3 = RTT, I4 = RTR, I5 = SSS) in FIG. 7 will be described as a representative example by paying attention to the expression relating to the third row Ioα in the expression (1). . When formula (1) in this state is expanded, it can be expressed as formula (5).

  Regardless of the switching state applied to I1 to I5, it can be expressed by the coefficients of the detected output current values Ioα and Ioβ developed on the stationary αβ axis as shown in equation (5). By substituting Iiα * in equation (3) for the left side Iiα * in equation (5), the left and right sides can be compared with coefficients of Ioα and Ioβ, respectively, so that the output current detection values Ioα and Ioβ can be eliminated, and equation (6) Can guide you.

  As described above, all the values except for d1 to d5 to be obtained are known numbers, and Iiβ * can be similarly obtained. Thus, when expressed in a matrix format including the row relating to Vo *, equation (7) is obtained.

  Here, Kva1 to Kva5 are Kvaan (coefficient: n = 1 to 5) · Vi1a + Kvabn (coefficient: n = 1 to 5) · Vi1b, respectively. Kvb1 to Kvb5 are Kvban (coefficient: n = 1 to 5) · Vi1a + Kvbbn (coefficient: n = 1 to 5) · Vi1b, respectively. n is a vector number 1 to 5, d1 to d5 are space vector duties using five basic vectors, Volα * and Volβ * are output line voltage commands, and Iixx (Iia: Ioα in the equation for obtaining Iiα *) The coefficient to be multiplied, Iiab: the coefficient to be multiplied by the Ioβ term of the expression for obtaining Iiα *, Iiba: the coefficient to be multiplied by the Ioα term of the expression for obtaining Iiβ *, and Iibb: the coefficient to be multiplied to the Ioβ term of the expression for obtaining Iiβ *) The current command calculated value (substitute from equation (3)), Kixx1 to Kixx5 (xx is aa, ab, ba, bb) are coefficients.

  Since the duty factor matrix is a 7 × 5 non-square matrix as shown in Equation (7), the duty is calculated as shown in Equation (8) using the Moore-Penrose generalized inverse matrix calculation method.

  Note that “+” in the duty factor inverse matrix means a generalized inverse matrix of Moore-Penrose.

  The above is the procedure of duty calculation (space vector modulation). According to the present embodiment, compared to the first embodiment, a direct AC-AC conversion type AC-AC direct conversion device including a means capable of calculating a duty without detecting an output current is obtained. A simple output current sensor or the like is not required, and the input / output waveforms can be converted into sine waves simultaneously. The control block of the control apparatus 4 in this embodiment is shown in FIG.

  This method is not limited to the 5-vector selection method (VXmax, VXmid, VYmax, VYmid, Vz) as in the first embodiment. Therefore, this duty calculation method is established even for other vector selections (can also be applied to selection methods of other embodiments described later).

(Embodiment 3)
The Moore-Penrose generalized inverse matrix of the second embodiment is often complicated in terms of algorithm implementation, and computation may take time. In view of this, in this embodiment, calculation formulas are preliminarily formed into a pattern table for all combinations of five basic vectors assumed, and the calculation algorithm is simplified and speeded up.

  Usually, when solving the Moore-Penrose generalized inverse matrix, the singular value decomposition method is often used, but here the Moore− is based on the premise that the duty factor matrix of Equation (7) is the maximum column rank. Calculation is performed using the expression (9) from the Penrose condition.

  A is a duty factor matrix, AT is a transpose matrix of A, and A + is a Moore-Penrose generalized inverse matrix of A.

  Therefore, when the rank of the duty factor matrix is 5, Expression (7) can be expressed as Expression (10).

  Each coefficient Kxxx (Kvaan, Kvabn, Kvban, Kvbbn) in equation (10) is substituted with the coefficients of any five selected basic vectors, but the combination of selecting five patterns from a total of 27 patterns of switching states is The number of patterns is determined in advance according to the control policy. For example, when the basic vectors “VXmax, VXmid, VYmax, VYmid, Vz” are always selected as in the first embodiment, 12 patterns are provided for each sector (sector 1 to sector 6) of the space vector on the output side. Since it exists, it is limited to the combination of a total of 72 patterns. In addition, depending on the basic vector selection pattern, there may be the same coefficient, so the number of combinations can be further reduced.

  Therefore, in the present embodiment, a basic vector selection pattern limited according to the control policy as described above is derived in advance, and in each case, the operational expression shown in Expression (10) is expanded into a table, and then the Moore-Penrose generalized inverse matrix operation is performed. This is a direct AC-AC conversion type AC-AC direct conversion device provided with duty calculation means for simplifying the above. Although the number of branches for selecting an arithmetic expression increases, the selection itself is only sector discrimination of the input / output space vector, reducing the computational load after branching, improving operational reliability, and reducing CPU performance and cost. It leads to. FIG. 11 shows a control block of the control device 4 in the present embodiment.

(Embodiment 4)
When the basic vectors “VXmax, VXmid, VYmax, VYmid, Vz” are always selected as in the first embodiment, the switching order within one control cycle is considered. For example, in the case of the input sector 1 and the output sector 1 as shown in FIG. 7, the basic vector to be used is in a state of separation from five switching states of RTR, RSR, RTT, RSS, and SSS. The duty calculation (space vector modulation) of these five basic vectors is switched within one control cycle, and the average value of one control cycle is controlled to be the input / output command values.

  These five switching states are preferably switched with as few phases as possible. Considering the case of FIG. 7, if one of the transition patterns of RTT → RTR → RSR → RSS → SSS or its inverse, SSS → RSS → RSR → RTR → RTT, is used, the switch is switched four times. Therefore, it is always possible to carry out every phase (four phases in total for each phase). If the arrangement is other than the above two transition patterns, the number of times of switching increases due to unnecessary switching (switching of two or more phases), leading to an increase in loss and an increase in harmonic noise. In addition, the above two transition patterns are alternately turned back every control cycle (... → RTT → RTR → RSR → RSS → SSS → SSS → RSS → RSR → RTR → RTT →...) Switching in any sector can always be optimized.

  Similarly, other sectors other than the example of FIG. 7 can always select a switching minimization pattern by deriving two transition patterns to be switched for each phase by four times of switching.

  According to the present embodiment, compared to the first to third embodiments, by determining the switch switching transition pattern so that the number of elements to be switched is minimized in the array of five switching states in one control cycle, A direct AC-AC conversion type AC-AC direct conversion device provided with duty calculation means capable of reducing switching loss is obtained.

(Embodiment 5)
The basic vector selection method of the first embodiment uses the same basic vector as a result of the conventional virtual DC link method. That is, since a rotation vector is not used, this is a switching state selection pattern that can be expressed by the virtual DC link method without using the direct AC / AC conversion type space vector modulation method. In the present embodiment, it is shown that the performance can be improved over the selection method of the first embodiment by using the rotation vector that is considered to be redundant.

FIG. 12 shows the states of the input sector 1 and the output sector 1. Unlike Embodiment 1 of FIG. 7, the switching state RTS which is the clockwise rotation vector Vrot is used. On the output space vector side, since one rotation vector Vrot always exists in one sector, that vector is always selected. Similarly to the first embodiment, the zero vector Vz using the intermediate phase of the input phase voltage capable of reducing the common mode voltage is selected. The remaining three vectors are selected from six vectors (VXmax, VXmid, VXmin, VYmax, VYmid, VYmin in FIG. 6) on the two simple vibration vector axes sandwiching the sector region, and the selection pattern is ₆ C. ₃ = 20 patterns are possible. However, the smallest vector (VXmin, VYmin) among the simple vibration vectors is a basic vector having a large phase difference with respect to the input command value on the input space vector side, and is not used for reducing the input ripple. For example, referring to the example of FIG. 12, when STT and STS on the output side are selected, a vector in the direction of 90 degrees is obtained in the input space, and a relatively large phase difference is generated with respect to the input sector area.

Therefore, the actual ₄ C ₃ = 4 pattern “RTS, SSS, RTR, RSR, RTT”, “RTS, SSS, RTR, RSR, RSS”, “RTS, SSS, RTR, RTT, RSS”, “RTS, SSS” , RSR, RTT, RSS "and their inversion patterns. Any one of the eight transition patterns including the inversion pattern may be selected and controlled. Elements that determine the pattern discrimination are the input phase θ, the output phase l, the magnitude of the output voltage command V, and the like. Have complex conditions.

  Therefore, in this embodiment, the coefficient matrix and the generalized inverse matrix of Moore-Penrose are calculated for all the eight transition patterns, and solutions for the duties d1 to d5 are obtained. If there is a pattern in which even one of the obtained duty solutions is negative or the added value of the duty solution is not 1, the switching state of the five selected basic vectors is unreasonable, and the input / output waveform is This means that it cannot be made sinusoidal.

  Therefore, such a pattern is excluded, and a pattern from which a valid solution is obtained is determined from the four patterns. The finally determined switching pattern is applied to the control of the AC-AC direct conversion device. The duty calculation method is the same as in the first to third embodiments.

  In this embodiment, since a rotation vector having a smaller phase difference from the command value than a simple vibration vector can be used, the pulsation of the input / output waveform can be reduced compared to the method of the first embodiment and the virtual DC link method. And a direct AC-AC conversion type AC-AC direct conversion device provided with a fundamental vector selection means capable of reducing harmonics.

(Embodiment 6)
In the present embodiment, the switching pattern in the method of the fifth embodiment is optimized. The switching states in the input sector “1” and the output sector “1” in the fifth embodiment are “RTS, SSS, RTR, RSR, RTT”, “RTS, SSS, RTR, RSR, RSS”, “RTS, SSS, RTR, Attention is paid to a case where there are eight transition patterns including “RTT, RSS”, “RTS, SSS, RSR, RTT, RSS” and inversion of these transition patterns. Now, the eight transition patterns are divided into modes as follows.

Mode 1: “RTS, SSS, RTR, RSR, RTT”
Mode 2: “RTS, SSS, RTR, RSR, RSS”
Mode 3: “RTS, SSS, RTR, RTT, RSS”
Mode 4: “RTS, SSS, RSR, RTT, RSS”
Regarding these, as in the fourth embodiment, a transition pattern is considered in which the elements to be switched are minimized within one control cycle and the switching is performed for each phase. Then, no matter how the modes 1 and 4 are rearranged, it is impossible to realize switch switching for each phase. Therefore, for mode 1 and mode 4, the zero-phase vector SSS is switched to RRR or TTT. Zero phase vectors can be replaced with each other because zero voltage is output using any of RRR, SSS, and TTT. However, in this embodiment, the common mode voltage is sacrificed.

Mode 1:
In the case of “RTS, RRR, RTR, RSR, RTT”, the transition pattern is RRR → RSR → RTR → RTS → RTT, RTT → RTS → RTR → RSR → RRR.

  In the case of “RTS, TTT, RTR, RSR, RTT”, the transition pattern is TTT → RTT → RTS → RTR → RSR, RSR → RTR → RTS → RTT → TTT.

Mode 2:
“RTS, SSS, RTR, RSR, RSS” is a transition pattern of SSS → RSS → RSR → RTR → RTS, RTS → RTR → RSR → RSS → SSS, or SSS → RSS → RTS → RTR → RSR, RSR → RTR. → RTS → RSS → SSS transition pattern may be used.

  Mode 3: “RTS, SSS, RTR, RTT, RSS” is a transition pattern of SSS → RSS → RTS → RTR → RTT, RTT → RTR → RTS → RSS → SSS.

Mode 4:
When “RTS, RRR, RSR, RTT, RSS”, the transition pattern is RRR → RSR → RSS → RTS → RTT, RTT → RTS → RSS → RSR → RRR.

  In the case of “RTS, TTT, RSR, RTT, RSS”, the transition pattern is TTT → RTT → RTS → RSS → RSR, RSR → RSS → RTS → RTT → TTT.

  As described above, in the present embodiment, when the five-vector selection method shown in the fifth embodiment is used, switching for each phase is realized by switching the zero vector to be used, and switching is performed within one control cycle. A direct AC-AC conversion type AC-AC direct conversion device having means capable of minimizing the elements is obtained.

  Note that even cases other than the sector state shown in the present embodiment can be minimized by the same operation.

(Embodiment 7)
The sixth embodiment is a direct AC-AC conversion type AC-AC direct conversion device including means for optimizing the transition pattern in consideration of only the minimization of switching frequency in the method of the fifth embodiment. However, the common mode voltage, that is, the reference for PWM control, the input phase voltage and the intermediate phase can reduce the voltage drop of the PWM pulse at the time of switching, so that switching noise and switching loss can be reduced. Become.

  Therefore, in this embodiment, in addition to the switching effect for each phase of the sixth embodiment, a switching transition pattern via the intermediate phase of the input phase voltage is given as a constraint condition. In the example of the input sector “1” and the output sector “1” in FIG. 12, since the magnitude relationship of the input phase voltage is Vr> Vs> Vt, the intermediate phase is Vs, that is, the S phase. Therefore, in order to satisfy the above-mentioned constraint conditions, a direct switching transition between the R phase and the T phase must be avoided (switching via the S phase is always performed).

  Here, regarding the four modes shown in the sixth embodiment, considering the constraint condition and considering the selection of the zero vector and the transition pattern again, the determination can be made as follows.

Mode 1:
In the case of “RTS, RRR, RTR, RSR, RTT”, the transition pattern is RRR → RSR → RTR → RTS → RTT, RTT → RTS → RTR → RSR → RRR.

Mode 2:
In the case of “RTS, SSS, RTR, RSR, RSS”, the transition pattern of SSS → RSS → RSR → RTR → RTS, RTS → RTR → RSR → RSS → SSS, or SSS → RSS → RTS → RTR → RSR, RSR → RTR → RTS → RSS → SSS transition pattern.

Mode 3:
The switching order can be considered using any of the zero vectors of “RTS, RRR, RTR, RTT, RSS”, “RTS, SSS, RTR, RTT, RSS”, “RTS, TTT, RTR, RTT, RSS”. This mode is not possible because it violates the constraints.

Mode 4:
When “RTS, RRR, RSR, RTT, RSS”, the transition pattern is RRR → RSR → RSS → RTS → RTT, RTT → RTS → RSS → RSR → RRR.

  Therefore, mode 3 should not be used in the sector area of input sector “1” and output sector “1”, but as a result, control can be performed without using mode 3 in this area range (duty valid in other modes). Therefore, the restriction condition can be satisfied by setting the mode 3 to the prohibit mode. Further, since the mode to be prohibited changes in other sector areas, the inhibition mode may be determined from the input / output sectors.

  In the present embodiment, in any input / output sector, by setting one of the four to the prohibit mode, switching for each phase and switching between the maximum phase and the minimum phase can be prevented. Furthermore, a direct AC-AC conversion type AC-AC direct conversion device having means capable of switching with low noise and low loss is obtained.

(Embodiment 8)
When the input / output space vector is in the state shown in FIG. 4 and the input command value exists in the input sector “1” and the phase of the output command value is larger than the rotation vector RTS and smaller than the RST, that is, In the case of 13 states, it is preferable to select five “RST, RTS, RTT, RSS, zero vector” having a smaller phase difference in the output space.

  Therefore, in the present embodiment, means for applying a mode using two rotation vectors across a single vibration axis in an output region where the phase difference may be smaller than 60 degrees as shown in FIG. The direct AC-AC conversion type AC-AC direct conversion device is provided. In addition, the duty calculation and the like are the same as those in the above embodiments. By using this embodiment together, further reduction of the pulsation of the output voltage can be expected.

(Embodiment 9)
Considering the switching optimization of the eighth embodiment in the same manner as in the seventh embodiment, if the following transition pattern is used, direct commutation prevention between the maximum phase and the minimum phase and switching for each phase can be realized.
“SSS → RSS → RTS → RST → RTT”, “RTT → RST → RTS → RSS → SSS”
According to the present embodiment, a direct AC-AC conversion type AC-AC direct conversion device including means capable of reducing switching loss and noise by optimizing the switching order when two rotation vectors are used. It becomes.

(Embodiment 10)
Although the Moore-Penrose generalized inverse matrix has been used in the method of the above-described embodiment, the output voltage is overmodulated, or an unexpected operation or command value is supplied, which is valid in all modes. If the duty solution cannot be obtained, the following procedure will be taken as fail-safe to avoid failure and unstable operation. It should be noted that any command value input can output any one of the 27 switching states shown in Table 1 so that input power supply short circuit prevention and output discontinuity can be avoided. When the duty command performs an unexpected operation, the input / output waveform continues to be in a transient state (causes a switching pattern transition unnecessarily, a large phase difference between the basic vectors before and after the transition, and a large variation in the vector size). There is a possibility that the operation of the AC-AC direct conversion device becomes unstable.

  (Procedure 1) First, when the duty solution cannot be obtained in the modes of the fifth and eighth embodiments, the second embodiment similar to the virtual DC link method is applied.

  (Procedure 2) If the duty solution cannot be obtained even in the above (Procedure 1), a general conventional virtual DC link type space vector modulation method is operated in parallel, and the control is switched to that control. Although it is not possible to convert the input / output into a sine wave, it is possible to perform a continuous operation (when the duty solution cannot be obtained, the virtual link type space vector modulation is not given a blank for switching control).

  (Procedure 3) If an unstable operation is caused even in the above procedure, it is determined as a failure and the operation is stopped.

The basic block diagram of an alternating current-alternating current direct conversion apparatus. The basic space vector diagram of an output voltage. The basic space vector diagram of input current. Input side space vector diagram (a) and output side space vector diagram (b). Definition example of “input side” sector and “output side” sector of space vector. The state diagram of the basic space vector in the output sector “1”. The state diagram of an input side space vector and an output side space vector. An example of redefining the space vector on the input and output sides. Control block diagram (Embodiment 1). Control block diagram (Embodiment 2). Control block diagram (Embodiment 3). The state diagram of the input sector 1 and the output sector 1. The state diagram of the input sector 1 and the output sector 1.

Explanation of symbols

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

Claims (9)

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 among these, four simple vibration vectors VXmax, VXmid, VYmax, VYmid and one zero vector Vz are selected.
The selected five basic vectors, the input current command value Ii * and the output line voltage command value Vol * on the stationary αβ axis, are input current command values Iiα * and Iiβ *, and the output line voltage command value Volα *. , Volβ *, input voltage detection value Vi, and output current detection value Io, the duty of the five basic vectors is obtained, and the input and output waveforms are simultaneously converted into a sine wave. Space vector modulation method. 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 vector state 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 vector Vo * exists is delayed, and the X axis advance The simple 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 zero that is the intermediate voltage of the phase voltages. A vector Vz and a rotation vector Vrot that exists in one sector are set as basic vectors, and three simple vibration vectors, zero vector Vz, and rotation vector Vrot are selected among them.
The selected five basic vectors, the input current command value Ii * and the output line voltage command value Vol * on the stationary αβ axis, are input current command values Iiα * and Iiβ *, and the output line voltage command value Volα *. , Volβ *, input voltage detection value Vi, and output current detection value Io, the duty of the five basic vectors is obtained, and the input and output waveforms are simultaneously converted into a sine wave. Space vector modulation method. 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 vector state 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 vector Vo * exists is delayed, and the X axis advance The simple 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 zero that is the intermediate voltage of the phase voltages. A vector Vz and one rotation vector Vrot existing in the sector are set as basic vectors, and two rotation vectors, a zero vector Vz, and two simple vibration vectors sandwiched between two rotation vectors are selected. ,
The selected five basic vectors, the input current command value Ii * and the output line voltage command value Vol * on the stationary αβ axis, are input current command values Iiα * and Iiβ *, and the output line voltage command value Volα *. , Volβ *, input voltage detection value Vi, and output current detection value Io, the duty of the five basic vectors is obtained, and the input and output waveforms are simultaneously converted into a sine wave. Space vector modulation method.   4. The AC-AC direct switching according to claim 1, wherein a switching pattern of switching is determined so that the number of switching times is minimized in the switching states of the selected five basic vectors. 5. A space vector modulation method for a converter.   The switch switching transition pattern is determined so as to prevent direct commutation between the maximum phase and the minimum phase while minimizing the number of times of switching in the switching states of the five basic vectors selected. 4. The space vector modulation method for an AC-AC direct conversion device according to any one of 3 above.   6. The space vector modulation method for an AC / AC direct conversion device according to claim 1, wherein the duty is calculated using a generalized inverse matrix of Moore-Penrose.   The calculation of the duty is basically performed until a valid solution is obtained when one of the solutions of the Moore-Penrose generalized inverse matrix is negative, or when the added value of the duties of the five basic vectors is not 1. The space vector modulation method for an AC-AC direct conversion device according to any one of claims 1 to 6, wherein selection of vectors is switched.   8. The AC-AC direct conversion according to claim 1, wherein the duty is calculated by reducing a calculation load by expanding a solution of a generalized inverse matrix of Moore-Penrose in advance in a table. Device space vector modulation method. The calculation of the duty is performed by calculating the input current command values Iiα * and Iiβ * by comparing the output current detection value Io and the input current command values Iiα * and Iiβ * instead of the output current detection value Io. The space vector modulation method for an AC-AC direct conversion device according to any one of claims 1 to 8, wherein:

Images