Motor drive control device

Abstract

To provide a motor drive control device capable of restoring phase current detection of a motor in a three-level inverter from current of a DC portion of an inverter while realizing downsizing / cost reduction.SOLUTION: The motor drive control device comprises: an intermediate potential end side semiconductor switch 113u which is provided between an intermediate potential end of a DC power supply apparatus 101 and an input terminal of a three-phase motor 103; and first current detection means 105 provided between the intermediate potential end of the DC power supply apparatus 101 and the intermediate potential end side semiconductor switch 113u. Phase current information of the three-phase motor 103 is restored based on a plurality of current values detected by the first current detection means 105 during a period in which combinations of phases in an ON state of the intermediate potential end side semiconductor switch 113u turning on / off the intermediate potential end of the DC power supply apparatus 101 and the input terminal of the three-phase motor 103 are different, within one period of a carrier signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive control device. [Background technology]

[0002] Patent Document 1 discloses a three-level inverter circuit that includes a DC power supply device that has a positive electrode, a negative electrode, and a neutral point and outputs DC power, and a plurality of semiconductor switching elements that inversely converts the DC power supplied from the DC power supply device into AC power and supplies three-phase AC power to a load.

[0003] The power conversion device configured with this three-level inverter circuit includes a first auxiliary capacitor connected in parallel to a first smoothing capacitor connected between the positive pole and neutral point of the three-level inverter circuit, a second auxiliary capacitor connected in parallel to a second smoothing capacitor connected between the neutral point and negative pole of each of the U, V, and W phases of the three-level inverter circuit, current detection means for detecting the current flowing through the first and second auxiliary capacitors, and detection means for detecting the detection signal detected by the current detection means.

[0004] As a result, when a DC short circuit fault occurs between the positive pole and neutral point of the power conversion device, or between the neutral point and negative pole, the short circuit current flowing through the auxiliary capacitor can be detected by the current detection means, and the signal can be detected by the detection means, thereby detecting the occurrence of a DC short circuit fault. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-70258 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a motor drive control device that can restore the phase current detection of a motor in a three-level inverter from the current in the DC portion of the inverter while achieving miniaturization and cost reduction. [Means for solving the problem]

[0007] A motor drive control device according to the present disclosure includes a DC power supply device having a high potential end, a low potential end, and an intermediate potential end and outputting DC power; a plurality of arms respectively provided between the DC power supply device and each input terminal of a three-phase motor; a group of semiconductor switches provided on each of the plurality of arms and comprising a high potential end side semiconductor switch for turning on / off the high potential end and the input terminal of the three-phase motor, an intermediate potential end side semiconductor switch for turning on / off the intermediate potential end and the input terminal of the three-phase motor, and a low potential end side semiconductor switch for turning on / off the low potential end and the input terminal of the three-phase motor; first current detection means provided between the intermediate potential end and the group of semiconductor switches; second current detection means provided between the low potential end and the group of semiconductor switches; and a control circuit, wherein the control circuit detects each desired AC voltage target value within a range of the DC voltage of the DC power supply and a current that varies between the high potential end and the intermediate potential end at a frequency sufficiently higher than the frequency of the AC voltage. The high potential end semiconductor switch, the intermediate potential end semiconductor switch, and the low potential end semiconductor switch are on / off controlled using a first carrier signal and a second carrier signal that changes between the intermediate potential end and the low potential end in the same time cycle, and desired AC voltages are controlled to be output from each input terminal of the three-phase motor according to the on / off ratio, and when the first current detection means or the second current detection means detects an excessive current, it is determined that an excessive current is flowing through any of the high potential end side semiconductor switch, the intermediate potential end side semiconductor switch, and the low potential end side semiconductor switch, and the high potential end side semiconductor switch, the intermediate potential end side semiconductor switch, and the low potential end side semiconductor switch are turned off, and phase current information of the three-phase motor is restored based on a plurality of current values ​​detected by the first current detection means during periods in which the intermediate potential end side semiconductor switch is in an on state for different phase combinations within one cycle of the carrier signal. [Effects of the Invention]

[0008] The motor drive control device according to the present disclosure can achieve miniaturization and cost reduction, while restoring the phase current detection of the motor in a three-level inverter from the current in the DC portion of the inverter. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block circuit diagram showing the overall configuration of a motor drive control device according to a first embodiment. [Figure 2] 1 is a circuit block diagram showing a configuration of a control circuit according to a first embodiment; [Figure 3] 1 is a flowchart showing a processing procedure of a control circuit according to the first embodiment; [Figure 4] 1 is a flowchart showing a processing procedure for restoring three-phase currents in a control circuit according to the first embodiment. [Figure 5] FIG. 1 is a waveform diagram showing the relationship between a first on / off pattern of the semiconductor switch and an intermediate potential end current in the first embodiment. [Figure 6] A waveform diagram showing a current detection method different from that shown in FIG. 5. [Figure 7] Waveform diagram showing a current detection method different from that shown in FIGS. 5 and 6. [Figure 8] FIG. 10 is a waveform diagram showing the relationship between a second on / off pattern of the semiconductor switch and an intermediate potential end current in the first embodiment. [Figure 9] A waveform diagram showing a current detection method different from the current detection method in FIG. 8. [Figure 10] 10 is a circuit block diagram showing the configuration of a control circuit according to a second embodiment. [Figure 11] 10 is a waveform diagram showing the relationship between the on / off pattern of the semiconductor switch and the current of each part in the second embodiment. [Figure 12] 10 is a waveform diagram showing the relationship between other on / off patterns of the semiconductor switch and the currents of the various parts in the second embodiment. [Figure 13] 10 is a waveform diagram before correction with a corrected on / off pattern of a semiconductor switch according to the third embodiment. [Figure 14]10 is a waveform diagram showing the relationship between the corrected on / off pattern of the semiconductor switch and the current of each part in the third embodiment. [Figure 15] 10 is a waveform diagram showing the relationship between other corrected on / off patterns of the semiconductor switch and the currents of the various parts in the third embodiment. [Figure 16] 10 is a waveform diagram showing the relationship between other corrected on / off patterns of the semiconductor switch and the currents of the various parts in the third embodiment. [Figure 17] FIG. 10 is a waveform diagram showing the relationship between the first on / off pattern of the semiconductor switch and the intermediate potential end current in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that formed the basis of this disclosure) Hereinafter, embodiments will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

[0011] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to FIGS.

[0013] [1-1.Configuration] [1-1-1. Configuration of the motor drive control device] In FIG. 1, the high potential end, intermediate potential end, and low potential end of the DC power supply device 101 are connected to the input terminals of the three-phase motor 103 via a u-phase arm 102u, a v-phase arm 102v, and a w-phase arm 102w, respectively.

[0014] A current sensor 105, which is a first current detection means, is provided on the output side from the intermediate potential terminal, and is capable of detecting input / output current from the intermediate potential terminal.

[0015] Similarly, a shunt resistor 106 as a second current detection means is inserted on the output side from the low potential end, making it possible to detect the input / output current from the low potential end.

[0016] The u-phase arm 102u is provided with a high potential end side semiconductor switch 111u which turns on / off between the high potential end and the u-phase input terminal of the three-phase motor 103, an intermediate potential end side semiconductor switch 113u which turns on / off between the intermediate potential end and the u-phase input terminal of the three-phase motor 103, and a low potential end side semiconductor switch 112u which turns on / off between the low potential end and the u-phase input terminal of the three-phase motor 103.

[0017] Similarly, the V-phase arm 102v and the W-phase arm 102w are provided with a high potential end side semiconductor switch (not shown) that turns on / off between the high potential end and the input terminal of the three-phase motor 103, an intermediate potential end side semiconductor switch (not shown) that turns on / off between the intermediate potential end and the input terminal of the three-phase motor 103, and a low potential end side semiconductor switch (not shown) that turns on / off between the low potential end and the input terminal of the three-phase motor 103.

[0018] By combining the on / off states of a group of semiconductor switches consisting of multiple semiconductor switches, any voltage within the voltage range of the DC power supply device 101 can be supplied to each input terminal (u-phase, v-phase, w-phase) of the three-phase motor 103.

[0019] Regarding the on / off of the multiple semiconductor switches provided in the u-phase arm 102u, the v-phase arm 102v, and the w-phase arm 102w, there is a requirement that multiple semiconductor switches within the same arm must not be in the on state at the same time.

[0020] For example, if the high potential end side semiconductor switch 111u and the intermediate potential end side semiconductor switch 113u are turned on at the same time, the high potential end and the intermediate potential end of the output terminals of the DC power supply device 101 will be short-circuited, causing a large current to flow, which may exceed the allowable current of the high potential end side semiconductor switch 111u and the intermediate potential end side semiconductor switch 113u, and may lead to destruction of the high potential end side semiconductor switch 111u and the intermediate potential end side semiconductor switch 113u.

[0021] The same thing happens when the intermediate potential end semiconductor switch 113u and the low potential end semiconductor switch 112u are turned on simultaneously, or when the high potential end semiconductor switch 111u and the low potential end semiconductor switch 112u are turned on simultaneously.

[0022] In such a case, a large current due to a short circuit can be detected by using the current sensor 105 as the first current detection means and the shunt resistor 106 as the second current detection means.

[0023] For example, if the high potential end semiconductor switch 111u and the intermediate potential end semiconductor switch 113u are simultaneously in an on state, the current sensor 105 can detect that a large current is flowing.

[0024] Furthermore, if the high potential end side semiconductor switch 111u and the low potential end side semiconductor switch 112u are simultaneously on, or if the intermediate potential end side semiconductor switch 113u and the low potential end side semiconductor switch 112u are simultaneously on, the shunt resistor 106 can detect that a large current is flowing.

[0025] The above has been described regarding the U-phase arm, but even in the V-phase arm or W-phase arm, a current sensor (not shown) as a first current detection means and a shunt resistor (not shown) as a second current detection means are provided in the loop through which a large current flows due to a short circuit, and by using these, it is possible to detect a short circuit caused by multiple semiconductor switches being turned on simultaneously in the same arm.

[0026] If a short circuit is detected, measures are taken to protect the semiconductor switches, such as turning off all of the semiconductor switches. As described above, by using the current sensor 105 and the shunt resistor 106, it is possible to prevent the semiconductor switches from being destroyed by being turned on simultaneously.

[0027] Next, we will explain the relationship between the three-phase motor 103 and current. For example, if the intermediate potential end side semiconductor switch 113u is in the on state in the u-phase of the three-phase motor, the current sensor 105 detects the current flowing through the u-phase of the three-phase motor 103.

[0028] However, if the intermediate potential end side semiconductor switches (not shown) of other phases of the three-phase motor 103, such as the v phase and the w phase, are also turned on, the current sensor 105 detects the total value of the currents flowing through the phases, among the input terminals (u phase, v phase, w phase) of the three-phase motor 103, whose intermediate potential end side semiconductor switches are turned on.

[0029] For example, in the u-phase arm 102u, the v-phase arm 102v, and the w-phase arm 102w, the current flowing through the u-phase of the three-phase motor 103 can be detected from the output result of the current sensor 105 in a section where only the intermediate potential end side semiconductor switch 113u of the u-phase arm 102u is in the on state among the semiconductor switches on the intermediate potential end side.

[0030] In addition, if the semiconductor switch 113u on the intermediate potential end side of the u-phase arm 102u and the semiconductor switch (not shown) on the intermediate potential end side of the v-phase arm 102v are simultaneously in the on state, the output result of the current sensor 105 will be the sum of the current flowing through the u-phase of the three-phase motor 103 and the current flowing through the v-phase of the three-phase motor 103.

[0031] However, if the intervals for these current detections are short, the values ​​of the currents flowing through each input terminal (u phase, v phase, w phase) of the three-phase motor 103 during that interval are considered to be constant. Therefore, taking advantage of the fact that the total value of the currents flowing through each input terminal (u phase, v phase, w phase) of the three-phase motor 103 is zero, the total value of the currents flowing through the u phase of the three-phase motor 103 and the currents flowing through the v phase of the three-phase motor 103 is the sign-inverted value of the currents flowing through the w phase of the three-phase motor 103.

[0032] Then, the v-phase current value of the three-phase motor 103 can be calculated from the u-phase current value of the three-phase motor 103 and the w-phase current value of the three-phase motor 103. In this way, the three-phase current of the three-phase motor 103 can be restored.

[0033] [1-1-2. Control circuit configuration] FIG. 2 is a circuit block diagram of the control circuit 104 in FIG.

[0034] The control circuit 104 is composed of a microcomputer (CPU) 301, a current sensor AD converter 302, a three-level three-phase PWM generator 303, a first AD conversion start timer 304, a second AD conversion start timer 305, and an inverter carrier generator 306.

[0035] In the microcomputer 301, the current information of the three-phase motor 103 is restored using the converted value in the current sensor AD converter 302, and based on the voltage command of the three-phase motor 103, a three-level three-phase PWM signal is created by a three-level three-phase PWM generator 303 and an inverter carrier generator 306, and the signal is used to control the on / off of the semiconductor switches in the u-phase arm 102u, the v-phase arm 102v, and the w-phase arm 102w.

[0036] On the other hand, the current sensor AD converter 302 receives instructions on the timing to start AD conversion from a first AD conversion start timer 304 and a second AD conversion start timer 305 , which are controlled by the microcomputer 301 .

[0037] The timing is based on the carrier signal of the inverter carrier generator 306, and based on this reference, the processes from the current restoration process in the microcomputer 301 to the voltage command output for the three-phase motor 103 are also executed.

[0038] [1-1-3. Control procedure] Fig. 3 is a processing procedure diagram showing an outline of the control procedure in the control circuit 104 of Fig. 1. The processing of Fig. 3 is executed at regular intervals to ensure control performance and stability.

[0039] The certain time is the inverter carrier cycle shown in Fig. 2. In the process for each inverter carrier cycle, in process 401, the current value obtained by AD conversion performed in the previous cycle is read, and in process 402, the current of the three-phase motor 103 is restored according to the PWM pattern in the previous cycle. The detailed restoration procedure is shown in Fig. 4 and will be described later.

[0040] Next, in process 403, current feedback control is performed to maintain the rotation speed at a desired value. The current feedback control calculates the voltage to be applied to the three-phase motor 103 so that the detected current value approaches the current command.

[0041] Next, in process 404, the pulse width is converted to the pulse width of the inverter, and in process 405, the microcomputer 301 sets the pattern and timer value of the AD conversion start timer from the pulse width pattern (PWM pattern) so that the current sensor 105, which is the first current detection means, can detect the current value.

[0042] By setting in this way, as a result of outputting the PWM pattern, information on the current value detected by the current sensor 105 serving as the first current detection means is stored in the microcomputer 301.

[0043] 4 is a processing procedure diagram showing details of process 402. In process 501, the previous PWM pattern is referenced to check which phase current information the two AD conversion results, the first AD conversion value and the second AD conversion value, stored in the microcomputer 301, correspond to.

[0044] Next, in process 502, the two AD conversion results, the first AD conversion value and the second AD conversion value, stored in the microcomputer 301 are read out, and in process 503, they are stored as the detected current of the phase.

[0045] Then, in step 504, the currents of the remaining phases are calculated and stored as the detected output currents of those phases.

[0046] As a result, all of the detected current information for the three phases (u-phase, v-phase, w-phase) is stored, which means that the phase current information of the three-phase motor 103 can be restored.

[0047] [1-2. Control] The operation of the motor drive control device configured as above will now be described.

[0048] FIG. 5 is a timing waveform diagram showing three voltage commands applied to the three-phase motor 103, in which the high-voltage phase has a higher potential than the DC midpoint, the medium-voltage phase has a slightly lower potential than the DC midpoint, and the low-voltage phase also has a lower potential than the DC midpoint and is lower than the medium-voltage phase.

[0049] In order to distinguish between high-voltage phases, medium-voltage phases, and low-voltage phases, those related to the high-voltage phase are shown with solid lines, those related to the medium-voltage phase with dashed lines, and those related to the low-voltage phase with dashed lines.

[0050] The high-voltage phase output of the motor drive control device generates a desired output voltage by turning on / off the high-potential end side semiconductor switch and the intermediate potential end side semiconductor switch of the high-voltage phase.

[0051] Specifically, the "voltage command (high voltage phase)" and "high-middle PWM carrier" in the figure are compared, and if the "voltage command (high voltage phase)" is higher than the "high-middle PWM carrier", the semiconductor switch on the high potential end is turned on, and if the "voltage command (high voltage phase)" is lower than the "high-middle PWM carrier", the semiconductor switch on the middle potential end is turned on.

[0052] At this time, the low potential end semiconductor switch is always off. Similarly, the outputs of the medium voltage phase and low voltage phase of the DC power supply device 101 generate desired output voltages by turning on / off the medium potential end semiconductor switch and low potential end semiconductor switch of the corresponding phase.

[0053] Specifically, the "voltage command (medium voltage phase)" or "voltage command (low voltage phase)" in the figure is compared with the "medium-low PWM carrier," and if the "voltage command (medium voltage phase)" or "voltage command (low voltage phase)" is higher than the "medium-low PWM carrier," the semiconductor switch on the medium potential end of that phase is turned on, and if the "voltage command (medium voltage phase)" or "voltage command (low voltage phase)" is lower than the "medium-low PWM carrier," the semiconductor switch on the low potential end of that phase is turned on. At this time, the semiconductor switch on the high potential end of that phase is always off.

[0054] The voltage information output by the current sensor 105 provided on the output side from the intermediate potential terminal when the semiconductor switches are controlled in this manner will be described below.

[0055] The current flowing to each input terminal (u phase, v phase, w phase) of the three-phase motor 103 flows through the semiconductor switches of the three phases (u phase, v phase, w phase) that are turned on. Therefore, while the semiconductor switches on the intermediate potential end side of the three phases (u phase, v phase, w phase) are turned on, current flows between the intermediate potential end of the DC power supply device 101 and each input terminal (u phase, v phase, w phase) of the three-phase motor 103.

[0056] If the semiconductor switches of multiple phases are on, the sum of the currents of the multiple phases flows through the intermediate potential terminal. Based on this, the waveform at the bottom of the figure shows the current flowing into or out of the intermediate potential terminal as detected by the current sensor 105.

[0057] From the first timing (a) to timing (b) in the waveform diagram, the semiconductor switch on the intermediate potential end side of the high-voltage phase is on, so current of the high-voltage phase is input and output from the intermediate potential end.

[0058] On the other hand, from timing (b), the semiconductor switch on the intermediate potential end side of the medium-voltage phase is turned on, so that the medium-voltage phase current is also input and output from the intermediate potential end. Similarly, from timing (c), the semiconductor switch on the intermediate potential end side of the low-voltage phase is turned on, so that the low-voltage phase current is also input and output from the intermediate potential end.

[0059] That is, from timing (a) to timing (b), the current of the high-voltage phase is detected, from timing (b) to timing (c), the sum of the currents of the high-voltage phase and the medium-voltage phase (i.e., the sign-inverted value of the current value of the low-voltage phase) is detected, from timing (c) to timing (d), the current of the medium-voltage phase is detected, and from timing (d) to timing (e) at the center of the waveform diagram, the sum of the currents of the medium-voltage phase and the low-voltage phase (i.e., the sign-inverted value of the current of the high-voltage phase) is detected.

[0060] Therefore, by reading the values ​​of the current sensor 105 between timings (c) and (d) and at timing (e) using the current sensor AD converter 302 of the control circuit 104, the motor current of the medium voltage phase and the motor current of the low voltage phase can be determined.

[0061] Furthermore, the current value of the remaining phase can be obtained from the two phase current values. That is, the phase currents of the three-phase motor 103 can be restored using only the input / output current information at the intermediate potential end.

[0062] The timing for reading the value of the current sensor 105 is not limited to the case shown in Figure 5, but the phase current of the three-phase motor 103 can also be restored by reading the current information at the timing shown in Figure 6 or Figure 7, and the control program designer can select the timing as appropriate.

[0063] FIG. 8 is a timing waveform diagram similar to FIG. 5, and shows the case where the three applied voltage commands to the three-phase motor 103 are such that the high-voltage phase and the medium-voltage phase are at a potential higher than the midpoint, and the low-voltage phase is at a potential lower than the midpoint.

[0064] From the first timing (a) to timing (b) in the waveform diagram, the semiconductor switch on the intermediate potential end side of the high-voltage phase is on, so current of the high-voltage phase is input and output from the intermediate potential end.

[0065] On the other hand, from timing (b) to timing (c), all the semiconductor switches on the intermediate potential end side are turned off, and therefore there is no detection from the current sensor 105.

[0066] Similarly, from timing (c) to timing (d), only the semiconductor switch on the intermediate potential end side of the low voltage phase is turned on, and current sensor 105 can detect the phase current of the low voltage phase.

[0067] Furthermore, during the period from timing (d) to timing (e), the semiconductor switches on the intermediate potential end side of the medium voltage phase and low voltage phase are on, and current sensor 105 can detect the sum of the currents of the medium voltage phase and the low voltage phase, i.e., the sign-inverted value of the current of the high voltage phase.

[0068] In the end, for example, if the output of current sensor 105 is read by current sensor AD converter 302 of control circuit 104 during the period from timing (c) to timing (d) and the period from timing (d) to timing (e), the motor current of the medium voltage phase and the motor current of the low voltage phase can be detected.

[0069] The motor currents of the remaining phases can then be calculated from the detected currents. In other words, the phase current information of the three-phase motor 103 can be restored using only the input / output current information of the intermediate potential end.

[0070] As in the case of Figure 5, the timing for reading the value of the current sensor 105 is not limited to the case shown in Figure 8, but the phase current of the three-phase motor 103 can also be restored by reading the current information at the timing shown in Figure 9, and the control program designer can select this as appropriate.

[0071] As has been explained so far with several pulse patterns, when at least two output voltages are realized in part by combining the voltage at the intermediate potential end with other voltages, and the combination ratios of the potential ends other than the intermediate potential end to realize these two output voltages do not match, the currents of the two phases can be separated from the input / output current information of the intermediate potential end, and as a result, the currents of all three phases can be detected.

[0072] Furthermore, even if one of the two voltages is realized only from the voltage at the intermediate potential end, the currents of the two phases can be separated, and as a result, all the currents of the three phases can be detected.

[0073] If the amplitude of the output AC voltage is larger than expected, the input / output current at the mid-potential end will become zero, but this can be easily avoided by preventing the output of a voltage with an amplitude larger than expected in advance.

[0074] Furthermore, a method that can be used even when a voltage with an amplitude greater than expected is output will be described in the second embodiment.

[0075] [1-3. Effects, etc.] As described above, in the first embodiment, the current sensor 105, which is the first current detection means provided on the output side from the intermediate potential end of the DC power supply 101, can detect a case where the intermediate potential end side semiconductor switch connected to the intermediate potential end of the DC power supply 101 and the high potential end side semiconductor switch connected to the high potential end of the DC power supply 101, or the low potential end side semiconductor switch connected to the low potential end, are simultaneously turned on due to a malfunction, causing a short circuit in the power supply on the DC power supply 101 side, and can also restore the instantaneous current of the three-phase motor 103. This eliminates the need to provide a detection means for directly detecting the motor current, thereby enabling the device to be made smaller and less expensive.

[0076] (Embodiment 2) [2-1. Control circuit configuration] FIG. 10 shows the configuration of the control circuit 104 in the second embodiment.

[0077] Figure 10 is different from Figure 2 in embodiment 1 in that an AD converter 1302 for shunt resistor, a third conversion start timer 1304, and a fourth conversion start timer 1305 are added to perform AD conversion on the current information of the shunt resistor 106, which is the second current detection means.

[0078] [2-2. Operating principle] The operating principle of the second embodiment will be described below with reference to FIGS.

[0079] As explained in the first embodiment, when the AC output voltage increases, the phase with the highest voltage becomes the same potential as the high potential end, the phase with the lowest voltage becomes the same potential as the low potential end, and the phase with the intermediate potential becomes the same potential as the intermediate potential end, or a potential between the high potential end and the intermediate potential end, or a potential between the low potential end and the intermediate potential end.

[0080] FIG. 11 is a waveform diagram showing the case where the medium voltage phase is at a potential between the high potential end and the intermediate potential end.

[0081] Current sensor 105, which is the first current detection means provided on the output side of the intermediate potential terminal, can only detect the current of the medium voltage phase and cannot restore the three-phase current.

[0082] Similarly, FIG. 12 is a waveform diagram showing the case where the medium voltage phase is at a potential between the low potential end and the intermediate potential end.

[0083] In this case, current sensor 105, which is the first current detection means provided on the output side of the intermediate potential terminal, can only detect the current of the medium voltage phase and cannot restore the three-phase current.

[0084] However, in the case of Figure 11, the current at the low potential end detected by shunt resistor 106, which is the second current detection means provided on the output side of the low potential end, can detect the current of the low voltage phase, and in the case of Figure 12, the current of the low voltage phase and the total current of the low voltage phase and the medium voltage phase (i.e., the current of the high voltage phase) can be detected.

[0085] That is, by combining the current value detected by current sensor 105, which is a first current detection means provided on the output side of the intermediate potential end, and the current value detected by shunt resistor 106, which is a second current detection means provided on the output side of the low potential end, it is possible to detect currents of two different phases and reconstruct three-phase current.

[0086] As in the first embodiment, current detection may be possible at timings other than the current read timings described in FIGS. 11 and 12, and the designer of the control program can select the timing as appropriate.

[0087] [2-3. Effects, etc.] As described above, in the second embodiment, the current value detected by the current sensor 105, which is the first current detecting means provided on the output side of the intermediate potential end of the DC power supply 101, and the shunt resistor 106, which is the second current detecting means provided on the output side of the low potential end of the DC power supply 101, can be used to detect a case where the intermediate potential end side semiconductor switch connected to the intermediate potential end and the high potential end side semiconductor switch connected to the high potential end, or the low potential end side semiconductor switch connected to the low potential end, are simultaneously turned on due to a malfunction, causing a short circuit in the power supply on the DC power supply 101 side, and can also restore the instantaneous current of the three-phase motor 103 over a wider voltage range than in the first embodiment.

[0088] (Embodiment 3) [3-1. Operating principle] In the first and second embodiments, it has been assumed that there is a relatively large margin in the detection time for current detection at the intermediate potential end and the low potential end.

[0089] However, when the amplitude of the output AC voltage is small, the difference between the three phase voltages becomes small, and the time width of the current flowing in and out of the intermediate potential end and low potential end also becomes small.

[0090] This may result in the possibility that the AD conversion circuit of the control circuit 104 may not be able to perform conversion with high precision.

[0091] FIG. 13 is a timing waveform diagram in the case where the voltages of the high voltage phase and the medium voltage phase are both at potentials between the intermediate potential end and the low potential end, and are very close to each other.

[0092] In this case, the three-phase current cannot be restored unless the current (high-voltage phase current) is AD converted at least within the short time between timings (b) and (c).

[0093] This is because, between timings (a) and (b), current cannot be detected by the current sensor 105 and shunt resistor 106, and between timings (c) and (e), another piece of current information (current of the low voltage phase) needs to be detected (however, there is a time gap between timings (c) and (e), making detection easy).

[0094] The same thing occurs even if the output voltage width is not small, but the output voltages of the two phases are close to each other.

[0095] If the output voltages of the two phases are close to each other, the semiconductor switch will be turned on and off in a short time, and the current flowing through the current sensor 105 will also be switched in a short time. An example waveform is shown in FIG.

[0096] In FIG. 13, in the section from timing (a) to (b), current sensor 105 can detect the total current of the high voltage phase and the medium voltage phase, that is, the current of the low current phase.

[0097] In the interval from timing (b) to (c), the current in the medium-voltage phase can be detected. In other words, the currents in two phases can be detected and the three-phase current can be restored. However, the interval from timing (b) to (c) is short, which makes it difficult to accurately detect the current in the medium-voltage phase.

[0098] FIG. 14 is a timing waveform diagram showing the corrected waveform in the case shown in FIG.

[0099] The timing at which the semiconductor switch on the medium potential end side of the medium voltage phase turns off is corrected from (c) to (c'), and the timing at which the semiconductor switch on the medium potential end side turns on is also changed from (f) to (f').

[0100] Similarly, the timing at which the high potential end semiconductor switch of the medium voltage phase turns on is corrected from (c) to (c'), and the timing at which the high potential end semiconductor switch turns off is also changed from (f) to (f').

[0101] This allows AD conversion to be performed over the relatively long period between timings (b) and (c') without having to be performed over the short period between timings (b) and (c), thereby improving the accuracy of current detection.

[0102] In addition, in one carrier section shown in FIG. 14, the connection ratio between the intermediate potential end and the low potential end does not change, so the output voltage in this carrier section is kept constant.

[0103] Therefore, the motor current can be appropriately detected without increasing the distortion of the applied voltage.

[0104] Figure 15 is a timing waveform diagram showing a similar situation with a different voltage pattern. In this case, too, the time between timings (b) and (c) is short, as shown in Figure 16. By changing timing (c) to (c') using the same method as in Figure 14, AD conversion can be performed over a relatively long period, improving the current detection accuracy.

[0105] Moreover, changing the timing (f) to (f') does not increase distortion in the applied voltage.

[0106] [3-2. Effects, etc.] As described above, according to the third embodiment, the accuracy of current detection can be improved without changing the on / off ratio of the semiconductor switches within one carrier period, thereby realizing highly accurate drive control of the motor.

[0107] (Fourth embodiment) [4-1. Operating principle] In the second embodiment, it has been shown that by using the current value detected by the current sensor 105, which is the first current detection means provided on the output side of the intermediate potential end of the DC power supply 101, and the shunt resistor 106, which is the second current detection means provided on the output side of the low potential end of the DC power supply 101, it is possible to restore current information of the three-phase motor 103 from the current of the inverter circuit even when the output voltage of the DC power supply 101 is very large.

[0108] However, it is necessary that the detection sensitivity of the current sensor 105 as the first current detection means and the detection sensitivity of the shunt resistor 106 as the second current detection means are the same.

[0109] In the fourth embodiment, a method for relatively correcting the detection sensitivity of the current sensor 105 as the first current detection means and the shunt resistor 106 as the second current detection means is provided.

[0110] FIG. 17 shows the same output waveform as FIG. 5, but the current value of the shunt resistor 106, which was not particularly necessary when explaining the first embodiment using FIG. 5, has been added.

[0111] To detect the current value of the three-phase motor 103, the output of the current sensor 105 is read using the first and second conversions of the current sensor AD converter 302 between timings (a) and (b) and between timings (b) and (c), thereby detecting the current value of the high-voltage phase and the sum of the current values ​​of the high-voltage phase and the medium-voltage phase (which is the same as the current of the low-voltage phase with the sign reversed), and as a result, the three-phase current can be restored.

[0112] On the other hand, if the current value of the shunt resistor 106 is read by the third conversion of the AD converter 1302 for shunt resistors between timings (a) and (b), the sum of the currents of the medium voltage phase and the low voltage phase (which is the same as the current of the high voltage phase with the sign reversed) can be detected, and if the current value of the shunt resistor 106 is read by the fourth conversion of the AD converter 1302 for shunt resistors between timings (b) and (c), the current value of the low voltage phase can be detected.

[0113] That is, the current sensor 105 serving as the first current detection means and the shunt resistor 106 serving as the second current detection means can detect the same current at the same timing.

[0114] Since the detection sensitivities of the current sensor 105, which is the first current detection means, and the shunt resistor 106, which is the second current detection means, are not necessarily completely the same, it is possible to equalize the detection sensitivities during operation by using one as a reference and correcting the detection sensitivity of the other.

[0115] [4-2. Effects, etc.] This improves the current detection accuracy when using the current sensor 105 as the first current detection means and the shunt resistor 106 as the second current detection means, as presented in embodiment 2, and also improves the accuracy of control using the detected current.

[0116] In terms of accuracy of the current detection means, it is necessary that the output when the current is zero is consistent, but the well-known method of reading the current value before the motor starts is also possible. In Figure 17, if the current value of the shunt resistor 106 is read between timings (d) and (e), the detected value of the current being zero can be read, and in Figure 6, if the information of the current sensor 105 is read between timings (b) and (c), the detected value of the current being zero in the current sensor 105 can be read.

[0117] In this way, the current detection accuracy can be relatively corrected during operation, and highly accurate current control of the three-phase motor 103 can be achieved. [Industrial Applicability]

[0118] The present disclosure achieves miniaturization and cost reduction while enabling motor phase current detection in a three-level inverter to be restored from the current in the DC portion of the inverter, and is therefore applicable to household and commercial refrigeration and air conditioning equipment that uses a three-phase motor to drive a refrigerant compressor at variable speeds, such as household air conditioners and commercial air conditioners. [Explanation of symbols]

[0119] 101 DC power supply 103 Three-phase motor 104 Control circuit 105 Current sensor (first current detection means) 106 Shunt resistor (second current detection means) 102u u-phase arm 102v V-phase arm 102w w-phase arm 111u High-potential end semiconductor switch 112u Low-potential end semiconductor switch 113u Semiconductor switch at intermediate potential end 301 Microcomputer (CPU) 302 AD converter for current sensor 303 3-level 3-phase PWM generator 306 Inverter Carrier Generator

Claims

1. A DC power supply device having a high potential end, a low potential end, and an intermediate potential end and outputting DC power; a plurality of arms respectively provided between the DC power supply device and each input terminal of a three-phase AC motor; a high potential end side semiconductor switch provided on each of the plurality of arms for turning on / off the high potential end and each input terminal of the three-phase motor; an intermediate potential end side semiconductor switch for turning on / off the intermediate potential end and each input terminal of the three-phase AC motor; and a low potential end side semiconductor switch for turning on / off the low potential end and each input terminal of the three-phase AC motor. a first current detection means provided between the intermediate potential end and the semiconductor switch group; a second current detection means provided between the low potential end and the semiconductor switch group; and a control circuit, wherein the control circuit drives the three-phase AC motor with three-phase AC generated by the semiconductor switch group, and the control circuit has AC voltage target values ​​within a range of the DC voltage of the DC power supply device that drive the desired three-phase AC motor, and a frequency that is sufficiently higher than the frequency of the AC voltage, and and the intermediate potential end, and a second carrier signal that changes between the intermediate potential end and the low potential end in the same time cycle, to control the on / off of the high potential end semiconductor switch, the intermediate potential end semiconductor switch, and the low potential end semiconductor switch, so that desired AC voltages are output from each input terminal of the three-phase AC motor according to the on / off ratio, and when the first current detection means or the second current detection means detects an excessive current, it determines that an excessive current is flowing in any of the high potential end side semiconductor switch, the intermediate potential end side semiconductor switch, and the low potential end side semiconductor switch, and turns off the high potential end side semiconductor switch, the intermediate potential end side semiconductor switch, and the low potential end side semiconductor switch, and restores phase current information of the three-phase AC motor based on a plurality of current values ​​detected by the first current detection means during periods when different combinations of phases have the intermediate potential end side semiconductor switch in an on state within one cycle of the first and second carrier signals.

2. A motor drive control device as described in claim 1, characterized in that if the intermediate potential end side semiconductor switch is in the on state for only one predetermined phase within one period of the first and second carrier signals, phase current information of the three-phase AC motor is restored based on the current value detected by the first current detection means during the period when the intermediate potential end side semiconductor switch is in the on state for the predetermined phase, and the current value detected by the second current detection means during the period when the low potential end side semiconductor switch of at least one of the three phases is in the on state.

3. 2. The motor drive control device according to claim 1, wherein, when the first current detection means detects a current value during a period in which the intermediate potential end side semiconductor switch of a predetermined phase is solely in an on state, the timings at which the intermediate potential end side semiconductor switches of other phases are turned on or off are changed so that the period in which the intermediate potential end side semiconductor switch of the predetermined phase is solely in an on state is lengthened.

4. A motor drive control device as described in Claim 2, characterized in that when there is a period within one cycle of the first and second carrier signals in which the first current detection means and the second current detection means detect current values ​​of the same phase, the detection sensitivity of one current detection means is corrected based on the detection sensitivity of the other current detection means.

5. 5. The motor drive control device according to claim 1, wherein the start time for the first current detection means to detect a current value is determined from timer information for PWM driving the group of semiconductor switches for a desired output voltage of the DC power supply device.

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