Power conversion device

Abstract

To achieve highly reliable current abnormality diagnosis at low cost in a power conversion device including multiple power conversion units.SOLUTION: A power conversion device includes a first power conversion unit as a master unit and another power conversion unit as a slave unit, each power conversion unit includes a temperature detector, the master unit includes a control unit, and the control unit of the master unit has a function of reading a temperature monitor value of the slave unit detected by the temperature detector of the slave unit and executing a protection function of the power conversion device when the temperature monitor value is at or above a threshold value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] A protection technology for a power conversion device is disclosed in Patent Document 1. This is a power conversion device that performs a protection function in the event of an abnormality by monitoring the operating state from the output data of each power conversion unit during parallel operation of the power conversion devices.

[0003] The heat generation temperature of a power module used as a frequency conversion unit of a power conversion device can be calculated roughly from the power loss calculated according to the output current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020-152813 Summary of the Invention [Problem to be solved by the invention]

[0005] When a current detector is provided for each power conversion unit as in Patent Document 1, there is a problem that the cost of the power conversion device increases.

[0006] However, if current detectors are simply not provided for some of the power conversion units in order to reduce costs, abnormality detection becomes impossible, which reduces the reliability of the power conversion device.

[0007] Furthermore, since the abnormality diagnosis in Patent Document 1 is performed on an individual power conversion unit basis, if an abnormality occurs in the microcontroller or current detector, it becomes impossible to detect the abnormality in the power conversion unit in which the abnormality occurred, which creates another inherent problem of reducing the reliability of the power conversion device.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to realize highly reliable current abnormality diagnosis at low cost in a power conversion device made up of a plurality of power conversion units. [Means for solving the problem]

[0009] An example of a means for solving the above problem is as follows.

[0010] A power conversion device comprising a first power conversion unit as a master device and other power conversion units as slave devices, each power conversion unit having a temperature detector, the master device having a control unit, and the control unit of the master device having the function of reading the temperature monitor value of the slave device detected by the temperature detector of the slave device, and executing a protection function of the power conversion device if the temperature value is above a threshold. [Effects of the Invention]

[0011] According to the present invention, highly reliable current abnormality diagnosis can be realized at low cost in a power conversion device made up of a plurality of power conversion units.

[0012] Further means and effects of the present invention will become apparent throughout the entire specification below. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a schematic front view of a starting panel unit equipped with a power conversion device according to an embodiment of the present invention. [Figure 1B] 1 is a schematic right side view of a starting panel unit equipped with a power conversion device according to an embodiment of the present invention. FIG. [Figure 2] 1 is a diagram showing a schematic configuration of a power conversion device according to the present invention; [Figure 3] FIG. 10 is a flowchart illustrating an abnormality detection function according to an embodiment of the present invention. [Figure 4] FIG. 10 is a flowchart illustrating an abnormality detection function according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings as needed. [Example]

[0015] Fig. 1 is a schematic diagram of a starting panel 1 equipped with a power conversion device. Fig. 1A is a schematic front view, and Fig. 1B is a schematic right side view.

[0016] The power conversion device 2 mounted on this starting panel 1 is composed of two units, a power conversion unit 3 and a power conversion unit 4. Each power conversion unit is connected in parallel to a power source (not shown) via a terminal block.

[0017] The power conversion unit 3 and the power conversion unit 4 are mainly composed of a circuit board 21, a microcomputer 26 serving as a control unit, a diode module 22 serving as a DC conversion unit that converts the power input from the AC power supply RST into DC, a power module 23 serving as a frequency conversion unit that converts the DC current into a desired frequency, a smoothing capacitor 24, and cooling fins 25 for cooling the diode module 22 and the power module 23.

[0018] Fig. 2 is a diagram showing the general configuration of a power conversion device. 5 is an external motor driven by the power converter. Note that the motor is an example of an output target or drive target of the power converter, and is not limited to a motor.

[0019] The system includes power conversion units 3 and 4 connected in parallel, and shares the power required to drive motor 5. Each power conversion unit converts the input power it receives and supplies it to the stator coil of motor 5. Power conversion unit 3, which is the master unit in this embodiment, is equipped with a CT (Current Transformer) as a current detector 34 that detects the output current, but power conversion unit 4, which is the slave unit, is not equipped with one. In this embodiment, of the power conversion units 3 and 4 connected in parallel, power conversion unit 3 is the master unit and power conversion unit 4 is the slave unit.

[0020] Each power conversion unit has a temperature detector 33 located near the power module to monitor the temperature of the cooling fin 25 for overheat protection and to detect abnormal ambient temperatures. An example of the temperature detector 33 is a thermistor. The heat generation temperature of a power module can be roughly calculated from the power loss calculated according to its output current, and the relationship between the output current and the module heat generation temperature tends to be similar. If the output current of power conversion unit 4 is abnormally high compared to the output current of power conversion unit 3, the monitored temperature value on the power conversion unit 4 side will deviate upward, just as with the output current. On the other hand, if the output current of power conversion unit 4 is abnormally low compared to the output current of power conversion unit 3, the monitored temperature value of power conversion unit 4 will deviate downward, just as with the output current.

[0021] The microcomputer 26 reads the temperature monitor values ​​of each power conversion unit and determines that a current abnormality has occurred if the difference between the temperatures is large. If a current abnormality is determined, the microcomputer 26 executes protection (turns the output switch OFF).

[0022] Figure 3 is a flowchart of the anomaly detection function. Anomaly detection or anomaly monitoring is started in S01. Motor operation is started in S02. In S03, microcomputer 26 of control unit 32 of power conversion unit 3 reads monitored temperature value T1 of power conversion unit 3 and monitored temperature value T2 of power conversion unit 4 obtained from temperature detector 33. In S04, the temperature difference ΔT is calculated.

[0023] In S05, the microcomputer 26 compares the temperature difference ΔT with a preset temperature difference threshold value Tth, and if |ΔT|<|Tth|, the microcomputer 26 determines that the system is normal and returns to S03 to continue operation. On the other hand, if |ΔT|≧|Tth|, the microcomputer 26 detects the abnormality as a current abnormality, proceeds to S06, executes protection command 35 (output switch OFF), and ends operation in S07.

[0024] This embodiment makes it possible to detect current abnormalities without a current detector such as a CT. Furthermore, because the determination is based on the relative temperature difference between the power conversion units, even if each power conversion unit is within the allowable temperature range, it is possible to quickly detect the possibility that some kind of current abnormality has occurred in a power conversion unit that does not have a CT.

[0025] In the power conversion device of this embodiment, the current detector 34 for the output current is mounted only in the power conversion unit 3, not in the power conversion unit 4, thereby realizing a reduction in the cost of the starting panel, which is the control panel. In this way, the power conversion device of this embodiment makes it possible to realize highly reliable current abnormality diagnosis at low cost. [Example]

[0026] In the first embodiment, the microcomputer of the power conversion unit 3 acting as the master realizes an indirect current abnormality detection function by reading the temperature monitor values ​​of its own unit and the other power conversion units. In contrast, in the present embodiment, a direct current detection function is also used in addition to the indirect current abnormality detection function.

[0027] 4 is a flowchart of the anomaly detection function of the second embodiment. Anomaly detection or anomaly monitoring is started in S01. Motor operation is started in S02. When motor operation is started, the microcomputer 26 of the control unit 32 of the power conversion unit 3 reads the temperature monitor value T1 of the power conversion unit 3 and the temperature monitor value T2 of the power conversion unit 4 obtained from the temperature detector 33 in S03, and calculates the temperature difference ΔT in S04. Furthermore, the microcomputer 26 compares the temperature difference ΔT with a preset temperature difference threshold value Tth in S05, and if |ΔT|<|Tth|, returns to S03 and reads the temperature again (continues operation).

[0028] Furthermore, at the same time as reading the temperature monitor values ​​T1 and T2, the microcomputer 26 reads the current detection value from the current detector 34 of the power conversion unit 3 in S08, determines whether the output is in line with the command value in S09, and outputs the determination result. If the output is in line with the command value, the process returns to before S08 and repeats reading the current detection value.

[0029] If the command value is not met in S09, or if |ΔT|≧|Tth| in S05, the microcontroller 26 detects the abnormality as a current abnormality in S10, executes a protection command 35 (output switch OFF) in S06, and terminates operation in S07.

[0030] In the first embodiment, a current abnormality is determined based solely on the temperature of the power conversion unit, making it possible to detect a current abnormality without providing a current detector 34 such as a CT. Furthermore, because the determination is based on the relative temperature difference between the power conversion units, it is possible to quickly detect the possibility of a current abnormality occurring even if the temperature of each power conversion unit is within the allowable temperature range. In the second embodiment, it is possible to identify which power conversion unit is experiencing a current abnormality. Specifically, if the detected current value is significantly different from the command value, it is determined that a current abnormality has occurred in power conversion unit 3. Conversely, if the detected current value is substantially equal to the command value but |ΔT|≧|Tth| holds, it is determined that a current abnormality in power conversion unit 3 has not been detected, and the microcomputer 26 determines that a current abnormality has occurred in power conversion unit 4.

[0031] In this way, in addition to the features of the first embodiment, the present embodiment makes it possible to identify which power conversion unit has a fault by using the detected current value to determine whether a current abnormality has occurred.

[0032] Furthermore, the result can be displayed externally using an LED, etc. Furthermore, if each power conversion unit is provided with a protection function, it becomes possible to continue driving with a power conversion unit that has not executed protection. [Example]

[0033] The present invention can also be used in a configuration in which multiple power conversion units each have a microcomputer, read the temperature monitor value within their own unit, and each power conversion unit has an independent overheat protection function.

[0034] In the first and second embodiments, it is assumed that only the power conversion unit 3, which is the master device, is equipped with the control unit 32, microcomputer 26, and current detector 34. In this embodiment, the power conversion unit 4 also has the control unit 32, microcomputer 26, and current detector 34. In the first embodiment, the microcomputer of the power conversion unit 3, which is the master device, also reads the temperature monitor value of the power conversion unit 4, so the power conversion unit 3 also has an overheat protection function for the power conversion unit 4. By utilizing this, when the microcomputer of the power conversion unit 4, which is the slave device, fails, the overheat protection function can be consolidated into the master device, so that the protection function of the slave device can be continued. In addition, it is possible to reduce costs by lowering the performance of the microcomputer in the slave device, for example.

[0035] Furthermore, the present invention can be utilized even when there are three or more power conversion units. Specifically, during normal operation, each power conversion unit independently performs protection functions using its own current detection function and temperature monitoring function. However, if one of the power conversion units equipped with a microcomputer fails, the other power conversion unit to which the temperature monitor value and current detection value are transmitted functions as the master unit. In this way, the power conversion device of this embodiment can maintain its protection functions even if the microcomputer or other components fail.

[0036] The above examples illustrate the ideas and concepts of the present invention. Of course, the scope of the present invention also includes examples that are realized by combining the examples. Furthermore, as long as the disclosed ideas and concepts are used, any modifications or similar examples are also included within the scope of the present invention.

[0037] Furthermore, one example of the present invention described using the above embodiments can also be expressed as follows.

[0038] <Part 1> In the power conversion device, The system includes a first power conversion unit as a master device and another power conversion unit as a slave device, Each power conversion unit is equipped with a temperature detector; The master device includes a control unit, The control unit of the master unit is a power conversion device having a function of reading the temperature monitor value of the slave unit detected by the temperature detector of the slave unit, and executing a protection function of the power conversion device if the temperature monitor value is above a threshold value.

[0039] <Part 2> In the power conversion device <Item 1>, the protection function is a function of stopping the output of the power conversion device.

[0040] <Part 3> In <Item 1>, the control unit reads the temperature monitor value of the master device detected by a temperature detector of the power conversion unit of the master device, and if the temperature difference between the temperature monitor value of the slave device and the master device is equal to or greater than a threshold, executes a protection function of the power conversion device.

[0041] <Part 4> In any of <1> to <3>, the master unit includes a current detector; The control unit of the master device determines which power conversion unit is malfunctioning based on the temperature difference and the current value detected by the current detector.

[0042] <Part 5> In <Part 4>, A power conversion device that executes a protection function for a power conversion unit that is determined to have an abnormality.

[0043] <Part 6> In any of <1> to <3>, The slave device has the same configuration as the master device, A power conversion device in which a slave device functions as a master device when an abnormality occurs in a control unit of the master device.

[0044] <Part 7> In <Part 6>, A power conversion device that executes a protection function for a power conversion unit that is determined to have an abnormality.

[0045] <Part 8> In <Part 4>, The slave device has the same configuration as the master device, A power conversion device in which a slave device functions as a master device when an abnormality occurs in a control unit of the master device.

[0046] <No. 9> In <Part 8>, A power conversion device that executes a protection function for a power conversion unit that is determined to have an abnormality. [Explanation of symbols]

[0047] 1: Starting panel 2: Power conversion device 3: Power conversion unit (master unit) 4: Power conversion unit (slave unit) 5: Motor 21: Circuit board 22: Diode module 23: Power module 24: Smoothing capacitor 25: Cooling fin 26: Microcomputer 31: Power conversion unit 32: Control unit 33: Temperature detector 34: Current detector 35:Protection Directive

Claims

1. In the power conversion device, The power conversion system includes a first power conversion unit as a master device and another power conversion unit as a slave device, Each power conversion unit is equipped with a temperature detector; The master device includes a control unit, The control unit of the master unit is a power conversion device having a function of reading the temperature monitor value of the slave unit detected by the temperature detector of the slave unit, and executing a protection function of the power conversion device if the temperature monitor value is above a threshold value.

2. 2. The power conversion device according to claim 1, wherein the protection function is a function of stopping an output of the power conversion device.

3. 2. The power conversion device according to claim 1, wherein the control unit reads a temperature monitor value of the master device detected by a temperature detector of the power conversion unit of the master device, and executes a protection function of the power conversion device when a temperature difference between the temperature monitor value of the master device and the temperature monitor value of the slave device is equal to or greater than a threshold value.

4. In any one of claims 1 to 3, the master unit includes a current detector; The control unit of the master device determines which power conversion unit is malfunctioning based on the temperature difference and the current value detected by the current detector.

5. In claim 4, A power conversion device that executes a protection function for a power conversion unit that is determined to have an abnormality.

6. In any one of claims 1 to 3, The slave device has the same configuration as the master device, A power conversion device in which a slave device functions as a master device when an abnormality occurs in a control unit of the master device.

7. In claim 6, A power conversion device that executes a protection function for a power conversion unit that is determined to have an abnormality.

8. In claim 4, The slave device has the same configuration as the master device, A power conversion device in which a slave device functions as a master device when an abnormality occurs in a control unit of the master device.

9. In claim 8, A power conversion device that executes a protection function for a power conversion unit that is determined to have an abnormality.

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