Inverter control device

Abstract

This inverter control device: switches, in each carrier cycle, the state of a three-phase inverter among four kinds of use vectors such that the number of switching times is minimized; switches one basic space vector included in the four kinds of use vectors to a different basic space vector every 60-degree electrical angle; and switches a zero vector, which is used at the first timing of each carrier cycle, between two kinds of zero vectors every 60-degree electrical angle. When six electrical angles per one cycle of the inverter at the time of basic space vector switching are regarded as 0, 60, 120, 180, 240, and 300 degrees, six electrical angles per one cycle of the inverter at the time of zero vector switching become the angles obtained by adding, to the six electrical angles at the time of the basic space vector switching, the same prescribed angle of not less than 15 degrees but less than 45 degrees.

Description

Inverter control device

[0001] The present disclosure relates to an inverter control device that controls a three-phase inverter by space vector modulation.

[0002] Patent Document 1 discloses an inverter control device that controls a three-phase inverter having upper arm switches and lower arm switches connected in series for each phase by space vector modulation.

[0003] Special Publication No. 6-32593

[0004] When controlling a three-phase inverter using space vector modulation, if the initial state of the three-phase inverter in each carrier cycle is always set to the same zero vector, the locus of the voltage vector in each inverter cycle will become asymmetrical, which will increase the unbalance rate of the output voltage of the three-phase inverter and increase the pulsation of the output current of the three-phase inverter.

[0005] An object of the present disclosure is to suppress pulsation in the output current of a three-phase inverter.

[0006] A first aspect of the present disclosure is an inverter control device that controls a three-phase inverter (10) having upper arm switches (11 to 13) and lower arm switches (14 to 16) connected in series to each other for each phase by space vector modulation, the inverter control device setting an inverter period to an integer multiple of a carrier period, and in each carrier period, switching a state of the three-phase inverter (10) to four use vectors including two adjacent basic space vectors of six basic space vectors and zero vectors, a first zero vector and a second zero vector, so as to minimize the number of switching operations, selecting the four use vectors from the six basic space vectors, the first zero vector, and the second zero vector by the space vector modulation for each period that is an integer multiple of half the carrier period, calculating lengths of the selected four use vectors, and setting a general shape of a locus of a voltage vector in each inverter period that indicates the state of the three-phase inverter (10) as a circle. a zero vector used at the first timing of each carrier cycle between the first zero vector and the second zero vector at every 60 electrical degrees; and six electrical angles per inverter cycle at the time of basic space vector switching for switching one basic space vector used at the first timing of each carrier cycle between the first zero vector and the second zero vector in the order of drawing the circular locus are regarded as 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees, and the six electrical angles per inverter cycle at the time of zero vector switching for switching the zero vector used at the first timing of each carrier cycle between the first zero vector and the second zero vector are angles obtained by adding a common predetermined angle of 15 degrees or more and less than 45 degrees to each of the six electrical angles at the time of basic space vector switching.

[0007] In the first aspect, distortion of the locus of the voltage vector in each inverter cycle can be suppressed, thereby reducing the unbalance rate of the output voltage of the three-phase inverter (10) and suppressing pulsation of the output current of the three-phase inverter (10).

[0008] A second aspect of the present disclosure is characterized in that, in the first aspect, when the six electrical angles at the time of the basic space vector switching are considered to be 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees in the order in which the circular locus is drawn, the six electrical angles at the time of the zero vector switching are 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees.

[0009] In the second mode, the locus of the voltage vector in each inverter period can be made symmetrical.

[0010] A third aspect of the present disclosure is characterized in that, in the first or second aspect, when the state of the three-phase inverter (10) is represented by a vector (xyz) where x indicates a state of a U-phase, y indicates a state of a V-phase, z indicates a state of a W-phase, a value of 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, and when the electrical angle when one of the basic space vectors included in the four types of use vectors is switched and the other basic space vector is a vector (100) is considered to be 0 degrees, a period during which the zero vector used at the first timing of each carrier cycle becomes a vector (000) starts at an electrical angle obtained by adding the predetermined angle to 0 degrees and continues for a period of 60 electrical degrees.

[0011] A fourth aspect of the present disclosure is characterized in that, in the first or second aspect, when a state of the three-phase inverter (10) is represented by a vector (xyz) where x indicates a state of a U-phase, y indicates a state of a V-phase, z indicates a state of a W-phase, a value of 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, when the electrical angle when one of the four types of use vectors is switched and the other basic space vector is vector (100) is considered to be 0 degrees, a period during which the zero vector used at the first timing of each carrier cycle is vector (111) starts at an electrical angle obtained by adding the predetermined angle to 0 degrees and continues for a period of 60 electrical degrees.

[0012] A fifth aspect of the present disclosure is characterized in that, in the second aspect, when the state of the three-phase inverter (10) is represented by a vector (xyz) in which x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state in which the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state in which the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, when one of the four types of usage vectors is switched and the electrical angle when the other basic space vector is vector (100) is considered to be 0 degrees, the zero vector used at the first timing of each carrier cycle during a period in which the electrical angle is 30 degrees to 90 degrees becomes vector (000).

[0013] A sixth aspect of the present disclosure is characterized in that, in the first aspect, when the state of the three-phase inverter (10) is represented by a vector (xyz) where x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, when the electrical angle when one of the basic space vectors included in the four types of use vectors is switched and the other basic space vector is vector (100) is considered to be 0 degrees, the zero vector used at the first timing of each carrier cycle during a period when the electrical angle is 30 degrees to 90 degrees becomes vector (111).

[0014] A seventh aspect of the present disclosure is any one of the first to sixth aspects, characterized in that, when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value that is higher than the median of an operating frequency range of the three-phase inverter (10), the inverter period is set to an integer multiple of the carrier period.

[0015] In the seventh aspect, when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value higher than the median of the operating frequency range of the three-phase inverter (10), the effect of suppressing pulsation of the output current of the three-phase inverter (10) can be obtained.

[0016] An eighth aspect of the present disclosure is an inverter control device that controls a three-phase inverter (10) having upper arm switches (11 to 13) and lower arm switches (14 to 16) connected in series with each other for each phase by space vector modulation, characterized in that the inverter period is an integer multiple of the carrier period, and the triangular wave used as the carrier wave is switched between a triangular wave starting with a positive slope and a triangular wave starting with a negative slope every 60 electrical degrees.

[0017] In the eighth aspect, the locus of the voltage vector in each inverter cycle can be made symmetrical, thereby reducing the unbalance rate of the output voltage of the three-phase inverter (10) and suppressing pulsation of the output current of the three-phase inverter (10).

[0018] A ninth aspect of the present disclosure is the eighth aspect, wherein in each carrier cycle, a state of the three-phase inverter (10) is switched to four types of use vectors including two types of adjacent basic space vectors out of six types of basic space vectors and a first zero vector and a second zero vector which are zero vectors, so as to minimize the number of switchings, and the three-phase inverter (10) is switched to a vector (xyz) where x indicates a state of a U phase, y indicates a state of a V phase, z indicates a state of a W phase, a value 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on. When the state of data (10) is represented, if the basic space vector having a longer time duration in the carrier cycle of one of the two types of basic space vectors included in the four types of usage vectors is either (001), (010), or (100), a triangular wave starting with one of a positive and a negative slope is used as the carrier wave, whereas when the basic space vector having a longer time duration in the carrier cycle of one of the two types of basic space vectors included in the four types of usage vectors is either (011), (101), or (110), a triangular wave starting with the other of a positive and a negative slope is used as the carrier wave.

[0019] A tenth aspect of the present disclosure is the eighth or ninth aspect, characterized in that, when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value higher than the median of an operating frequency range of the three-phase inverter (10), the inverter period is set to an integer multiple of the carrier period.

[0020] The tenth aspect of the present disclosure can obtain an effect of suppressing pulsation of the output current of the three-phase inverter (10) when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value that is higher than the median of the operating frequency range of the three-phase inverter (10).

[0021] FIG. 1 is a circuit diagram showing the configuration of an inverter device including an inverter control device according to a first embodiment of the present disclosure. FIG. 2 is an explanatory diagram illustrating fundamental space vectors and zero vectors of a three-phase inverter. FIG. 3 is a timing chart showing a carrier wave, three-phase switching signals, and the state of the three-phase inverter. FIG. 4 is an explanatory diagram showing the outline of the trajectory of a voltage vector indicating the state of the three-phase inverter in each inverter cycle, and the fundamental space vector included in the use vector. FIG. 5 is an explanatory diagram showing the trajectory of the voltage vector in parts I to IV of FIG. 4. FIG. 6 is a diagram corresponding to FIG. 4 of a second embodiment.

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses.

[0023] 1 shows an inverter device (1) including a three-phase inverter (10) and an inverter control device (20) according to a first embodiment of the present disclosure that controls the three-phase inverter (10).

[0024] The three-phase inverter (10) has upper arm switches (11-13) and lower arm switches (14-16) connected in series to each other for each phase. In other words, the three-phase inverter (10) has three switching legs connected between a positive voltage side power supply line (31) and a negative voltage side power supply line (32). Each switching leg is formed by connecting one upper arm switch (11-13) and one lower arm switch (14-16) in series to each other. In each of the three switching legs, the midpoint between the upper arm switches (11-13) and the lower arm switches (14-16) is connected to a coil of each phase (u-phase, v-phase, w-phase coil) of a motor, which is a load. A free wheel diode (FD) is connected in anti-parallel to each of the upper arm switches (11-13) and the lower arm switches (14-16). The three-phase inverter (10) converts direct current into alternating current by switching operations of upper arm switches (11 to 13) and lower arm switches (14 to 16) and supplies the alternating current to the motor.

[0025] As shown in FIG. 2 , the three-phase inverter (10) can take eight vector (voltage vector) states V0 to V7. Here, x indicates the U-phase state, y indicates the V-phase state, and z indicates the W-phase state. A value of 1 indicates a state in which the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state in which the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on. When the vectors V0 to V7 are expressed as (xyz), vector V0 is (000), vector V1 is (001), vector V2 is (010), vector V3 is (011), vector V4 is (100), vector V5 is (101), vector V6 is (110), and vector V7 is (111). Vectors V0 and V7 are zero vectors, and hereinafter correspond to the first zero vector and the second zero vector, respectively. Vector V1, vector V2, vector V3, vector V4, vector V5, and vector V6 are six types of basic space vectors. Adjacent vectors in FIG. 2 are hereinafter referred to as "adjacent vectors." In FIG. 2, vector V1 and vector V3 are adjacent to each other. Vector V3 and vector V2 are adjacent to each other. Vector V2 and vector V6 are adjacent to each other. Vector V6 and vector V4 are adjacent to each other. Vector V4 and vector V5 are adjacent to each other. Vector V5 and vector V1 are adjacent to each other.

[0026] The inverter control device (20) outputs a U-phase switching signal (Su), a V-phase switching signal (Sv), and a W-phase switching signal (Sw) to control the three-phase inverter (10). When the U-phase switching signal (Su) is at a high level, the upper arm switch (11) is turned off and the lower arm switch (14) is turned on in the U-phase. On the other hand, when the U-phase switching signal (Su) is at a low level, the upper arm switch (11) is turned on and the lower arm switch (14) is turned off in the U-phase. When the V-phase switching signal (Sv) is at a high level, the upper arm switch (12) is turned off and the lower arm switch (15) is turned on in the V-phase. On the other hand, when the V-phase switching signal (Sv) is at a low level, the upper arm switch (12) is turned on and the lower arm switch (15) is turned off in the V-phase. When the W-phase switching signal (Sw) is at a high level, the upper arm switch (13) is turned off and the lower arm switch (16) is turned on in the W-phase. On the other hand, when the W-phase switching signal (Sw) is at a low level, the upper arm switch (13) is turned on and the lower arm switch (16) is turned off in the W-phase.

[0027] The inverter control device (20) controls the three-phase inverter (10) by space vector modulation. When the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value higher than the median of the operating frequency range (operable frequency range) of the three-phase inverter (10), the inverter control device (20) sets the inverter period of the three-phase inverter (10) to an integer multiple of the carrier period. Note that, even when the frequency of the output voltage of the three-phase inverter (10) is equal to or lower than the predetermined value, the inverter control device (20) may set the inverter period of the three-phase inverter (10) to an integer multiple of the carrier period. Alternatively, when the frequency of the output voltage of the three-phase inverter (10) is equal to or lower than the predetermined value, the inverter control device (20) may not control the inverter period of the three-phase inverter (10) to an integer multiple of the carrier period. This simplifies the control algorithm.

[0028] As shown in FIG. 3 , the inverter control device (20) switches the state of the three-phase inverter (10) to four use vectors, including two adjacent basic space vectors among six basic space vectors and a first zero vector and a second zero vector, in each carrier cycle so as to minimize the number of switching operations. The inverter control device (20) selects the four use vectors from the six basic space vectors, the first zero vector, and the second zero vector by the space vector modulation every period that is an integer multiple of half the carrier cycle, and calculates the lengths of the selected four use vectors. In FIG. 3 , the state of the three-phase inverter (10) is switched to vectors V4 and V6, which are basic space vectors, and vectors V0 and V7, which are zero vectors, in each carrier cycle. When switching the state of the three-phase inverter (10) between basic space vectors, the inverter control device (20) switches the state of only one phase. For example, as shown in FIG. 3 , when switching the state of the three-phase inverter (10) between vector V4 and vector V6, the inverter control device (20) switches only the state of the V phase, indicated by the value of y. Furthermore, when switching the state of the three-phase inverter (10) between the basic space vector and the zero vector, the inverter control device (20) switches only the state of one phase. For example, as shown in FIG. 3 , when switching the state of the three-phase inverter (10) between vector V4 and vector V0, the inverter control device (20) switches only the state of the U phase, indicated by the value of x. Furthermore, when switching the state of the three-phase inverter (10) between vector V6 and vector V7, the inverter control device (20) switches only the state of the W phase, indicated by the value of z. In this way, when switching the state of the three-phase inverter (10) between basic space vectors and when switching the state of the three-phase inverter (10) between the basic space vectors and the zero vector, the inverter control device (20) switches only the state of one phase, thereby minimizing the number of switching operations.

[0029] Furthermore, as shown in FIG. 4 , the inverter control device (20) determines that the approximate shape of the locus of the voltage vector indicating the state of the three-phase inverter (10) in each inverter cycle is a circle. FIG. 4 shows two types of basic space vectors included in four types of use vectors in each of six 60-degree ranges obtained by dividing a 360-degree electrical angle into six. The inverter control device (20) selects one basic space vector included in the four types of use vectors by the space vector modulation so as to switch it to a different basic space vector every 60 degrees of electrical angle. Specifically, in part I, the inverter control device (20) switches the basic space vectors included in the use vectors from vectors V4 and V5 to vectors V4 and V6. Similarly, in part III, the inverter control device (20) switches the basic space vectors included in the use vectors from vectors V4 and V6 to vectors V2 and V6.

[0030] The inverter control device (20) controls the three-phase inverter (10) by space vector modulation so that the state of the three-phase inverter (10) at the beginning of each of a plurality of consecutive carrier cycles becomes a zero vector. Hereinafter, "each carrier cycle" means each of the plurality of consecutive carrier cycles.

[0031] The inverter control device (20) switches the triangular wave used as the carrier wave between a triangular wave starting with a positive slope and a triangular wave starting with a negative slope every 60 electrical degrees. As a result, the inverter control device (20) switches the zero vector used at the first timing of each carrier cycle between the first zero vector and the second zero vector every 60 electrical degrees. Specifically, in part II of FIG. 4 , the inverter control device (20) switches the state of the three-phase inverter (10) at the beginning of each carrier cycle from vector V0 to vector V7. Also, in part IV of FIG. 4 , the inverter control device (20) switches the state of the three-phase inverter (10) at the beginning of each carrier cycle from vector V7 to vector V0. As shown in FIG. 4 , when the six electrical angles per cycle of the three-phase inverter (10) at the time of basic space vector switching, which switches one basic space vector included in the four types of use vectors, are considered to be 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees in the order of drawing the circular locus, the six electrical angles per cycle of the three-phase inverter (10) at the time of zero vector switching, which switches the zero vector used at the first timing of each carrier cycle between the first zero vector and the second zero vector, are 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees.

[0032] In the example of Fig. 3, the inverter control device (20) switches the triangular wave used as the carrier wave from a triangular wave starting with a positive slope to a triangular wave starting with a negative slope at the timing of switching the state of the three-phase inverter (10) at the beginning of each carrier cycle, whereby the inverter control device (20) switches the state of the three-phase inverter (10) at the beginning of each carrier cycle from vector V0 to vector V7.

[0033] Furthermore, when one of the four types of use vectors is switched and the other basic space vector is vector V4, i.e., vector (100), the electrical angle is regarded as 0 degrees (part I). The inverter control device (20) sets the zero vector used at the first timing of each carrier cycle to vector V7, i.e., vector (111), during the period when the electrical angle is between 30 degrees and 90 degrees (between parts II and IV). In other words, the period when the zero vector used at the first timing of each carrier cycle is vector (111) starts at an electrical angle of 30 degrees (an angle obtained by adding 30 degrees to 0) and continues for a period of 60 electrical degrees.

[0034] Furthermore, when the basic space vector having a longer time duration in the carrier cycle among two types of basic space vectors included in the four types of usage vectors is any one of vectors V1, V2, and V4, the inverter control device (20) uses a triangular wave starting with a positive slope as the carrier wave. On the other hand, when the basic space vector having a longer time duration in the carrier cycle among two types of basic space vectors included in the four types of usage vectors is any one of vectors V3, V5, and V6, the inverter control device (20) uses a triangular wave starting with a negative slope as the carrier wave.

[0035] The functions of the inverter control device (20) are realized by a microcomputer or the like.

[0036] 5 shows vector trajectories before and after switching of the use vector in parts I, II, III, and IV. In all of parts I, II, III, and IV, the vector trajectories before and after switching of the use vector are line-symmetric. When the vector trajectory before and after switching of the use vector in part I is rotated 60 degrees counterclockwise, it becomes equal to the vector trajectory before and after switching of the use vector in part III. When the vector trajectory before and after switching of the use vector in part II is rotated 60 degrees counterclockwise, it becomes equal to the vector trajectory before and after switching of the use vector in part IV.

[0037] Therefore, according to the first embodiment, the locus of the voltage vector in each inverter cycle can be made symmetrical. This reduces the unbalance rate of the output voltage of the three-phase inverter (10) and suppresses pulsation of the output current of the three-phase inverter (10). This reduces the peak value of the output current of the three-phase inverter (10), enabling the motor to be driven more stably and reducing motor noise.

[0038] Furthermore, by simply switching the carrier wave from a triangular wave starting with a positive slope to a triangular wave starting with a negative slope at a predetermined timing, the trajectory of the voltage vector in each inverter cycle can be made symmetrical, making control easy.

[0039] Furthermore, as the frequency of the output voltage of the three-phase inverter (10) becomes higher, the number of carrier periods included in each inverter period becomes smaller, the influence of distortion per carrier period becomes greater, and pulsation becomes more likely to occur. In the first embodiment, when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value that is higher than the median of the operating frequency range of the three-phase inverter (10), the inverter period of the three-phase inverter (10) is set to an integer multiple of the carrier period, thereby reliably achieving the effect of suppressing pulsation in the output current of the three-phase inverter (10).

[0040] (Embodiment 2) Figure 6 is a diagram corresponding to Figure 4 of embodiment 2. Here, too, when one of the basic space vectors included in the four types of use vectors is switched and the other basic space vector is vector V4, i.e., vector (100), the electrical angle is considered to be 0 degrees (part I). In this embodiment 2, the inverter control device (20) sets the zero vector used at the first timing of each carrier cycle to vector V0, i.e., vector (000), during the period when the electrical angle is between 30 degrees and 90 degrees (between parts II and IV). In other words, the period during which the zero vector used at the first timing of each carrier cycle is vector (000) starts at an electrical angle of 30 degrees (an angle obtained by adding 30 degrees to 0 degrees) and continues for a period of 60 electrical degrees.

[0041] Furthermore, when the basic space vector having a longer time duration in the carrier cycle among two types of basic space vectors included in the four types of usage vectors is any one of vectors V1, V2, and V4, the inverter control device (20) uses a triangular wave starting with a negative slope as the carrier wave. On the other hand, when the basic space vector having a longer time duration in the carrier cycle among two types of basic space vectors included in the four types of usage vectors is any one of vectors V3, V5, and V6, the inverter control device (20) uses a triangular wave starting with a positive slope as the carrier wave.

[0042] The other configurations are the same as those in the first embodiment, so detailed description thereof will be omitted.

[0043] In the first and second embodiments, when the six electrical angles at the time of switching the basic space vector are regarded as 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees in the order of drawing the circular locus, the six electrical angles per cycle of the three-phase inverter (10) at the time of switching the zero vector are 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees. However, the six electrical angles per cycle of the three-phase inverter (10) at the time of switching the zero vector are not limited to these. When the six electrical angles per cycle of the three-phase inverter (10) when the basic space vector is switched are regarded as 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees in the order of drawing the circular locus, the six electrical angles per cycle of the three-phase inverter (10) when the zero vector is switched can be set to angles obtained by adding a common predetermined angle of 15 degrees or more and less than 45 degrees to each of the six electrical angles when the basic space vector is switched, thereby suppressing distortion of the trajectory of the voltage vector in each inverter cycle. In the first embodiment, the period during which the zero vector used at the first timing of each carrier cycle is the vector (111) may start at an electrical angle obtained by adding the predetermined angle other than 30 degrees to 0 degrees and continue for a period of 60 electrical degrees. In the second embodiment, the period during which the zero vector used at the first timing of each carrier cycle is the vector (000) may start at an electrical angle obtained by adding the predetermined angle other than 30 degrees to 0 degrees and continue for a period of 60 electrical degrees.

[0044] Although the embodiments have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0045] The present disclosure is useful as an inverter control device that controls a three-phase inverter by space vector modulation.

[0046] 10 Three-phase inverter 11, 12, 13 Upper arm switch 14, 15, 16 Lower arm switch

Claims

1. An inverter control device that controls a three-phase inverter (10) having upper arm switches (11-13) and lower arm switches (14-16) connected in series for each phase by space vector modulation, wherein the inverter period is an integer multiple of a carrier period, and in each carrier period, the state of the three-phase inverter (10) is switched to four use vectors including two adjacent basic space vectors of six basic space vectors and zero vectors, first zero vector and second zero vector, so as to minimize the number of switching operations, the space vector modulation is used to select four use vectors from the six basic space vectors, the first zero vector and the second zero vector for each period that is an integer multiple of half the carrier period, and calculates lengths of the selected four use vectors, the approximate shape of a locus of a voltage vector in each inverter period that indicates the state of the three-phase inverter (10) is a circle, and the space vector modulation is used to select one basic space vector included in the four use vectors for every 60 electrical degrees so as to switch to a different basic space vector, an inverter control device which switches a zero vector used at a first timing of each carrier cycle between the first zero vector and the second zero vector every 60 electrical degrees, and when six electrical angles per inverter cycle at the time of basic space vector switching which switches one basic space vector included in the four types of use vectors are regarded as 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees in the order of drawing the circular locus, the six electrical angles per inverter cycle at the time of zero vector switching which switches the zero vector used at a first timing of each carrier cycle between the first zero vector and the second zero vector are angles obtained by adding a common predetermined angle of 15 degrees or more and less than 45 degrees to each of the six electrical angles at the time of basic space vector switching.

2. An inverter control device according to claim 1, wherein when the six electrical angles at the time of switching the basic space vector are regarded as 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees in the order of drawing the circular locus, the six electrical angles at the time of switching the zero vector are 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees.

3. An inverter control device according to claim 1 or 2, wherein, when the state of the three-phase inverter (10) is represented by a vector (xyz) where x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, and when the electrical angle when one of the basic space vectors included in the four types of use vectors is switched and the other basic space vector is vector (100) is considered to be 0 degrees, the period during which the zero vector used at the first timing of each carrier cycle is vector (000) starts at an electrical angle obtained by adding the predetermined angle to 0 degrees and continues for a period of 60 electrical degrees.

4. An inverter control device according to claim 1 or 2, wherein, when the state of the three-phase inverter (10) is represented by a vector (xyz) where x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, and when the electrical angle when one of the basic space vectors included in the four types of use vectors is switched and the other basic space vector is vector (100) is considered to be 0 degrees, the period during which the zero vector used at the first timing of each carrier cycle is vector (111) starts at an electrical angle obtained by adding the predetermined angle to 0 degrees and continues for a period of 60 degrees of electrical angle.

5. An inverter control device according to claim 2, wherein, when the state of the three-phase inverter (10) is represented by a vector (xyz) where x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state where the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state where the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, and when the electrical angle when one of the basic space vectors included in the four types of use vectors is switched and the other basic space vector is vector (100) is considered to be 0 degrees, the zero vector used at the first timing of each carrier cycle during a period where the electrical angle is between 30 degrees and 90 degrees becomes vector (000).

6. An inverter control device according to claim 1, wherein, when the state of the three-phase inverter (10) is represented by a vector (xyz) in which x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state in which the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state in which the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, when one of the four types of use vectors is switched and the electrical angle when the other basic space vector is vector (100) is considered to be 0 degrees, the zero vector used at the first timing of each carrier cycle during a period in which the electrical angle is between 30 degrees and 90 degrees becomes vector (111).

7. An inverter control device according to any one of claims 1 to 6, characterized in that when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value that is higher than the median value of the operating frequency range of the three-phase inverter (10), the inverter period is set to an integer multiple of the carrier period.

8. An inverter control device that controls a three-phase inverter (10) having upper arm switches (11-13) and lower arm switches (14-16) connected in series for each phase by space vector modulation, characterized in that the inverter period is an integer multiple of the carrier period, and the triangular wave used as the carrier wave is switched between a triangular wave starting with a positive slope and a triangular wave starting with a negative slope every 60 electrical degrees.

9. An inverter control device according to claim 8, wherein in each carrier cycle, the state of the three-phase inverter (10) is switched to four types of use vectors including two adjacent types of basic space vectors out of six types of basic space vectors and zero vectors, i.e., a first zero vector and a second zero vector, so as to minimize the number of switching operations; and when the state of the three-phase inverter (10) is expressed by a vector (xyz) where x indicates the state of the U phase, y indicates the state of the V phase, z indicates the state of the W phase, a value of 1 indicates a state in which the upper arm switches (11 to 13) are on and the lower arm switches (14 to 16) are off, and a value of 0 indicates a state in which the upper arm switches (11 to 13) are off and the lower arm switches (14 to 16) are on, when the basic space vector that takes up a longer time in the carrier cycle out of two types of basic space vectors included in the four types of use vectors is any one of (001), (010), or (100), a triangular wave that starts with one of a positive and a negative gradient is used as the carrier wave; and An inverter control device characterized in that, when the basic space vector having a longer time in the carrier cycle out of two types of basic space vectors included in the four types of usage vectors is either (011), (101), or (110), a triangular wave starting with the other of the positive and negative slopes is used as the carrier wave.

10. An inverter control device according to claim 8 or 9, characterized in that when the frequency of the output voltage of the three-phase inverter (10) exceeds a predetermined value higher than the median of the operating frequency range of the three-phase inverter (10), the inverter period is set to an integer multiple of the carrier period.

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