Power conversion device and current detection device

Abstract

To provide a power conversion device and a current detection device capable of improving resistance to failure of a current sensor with a simpler configuration.SOLUTION: A power conversion device includes a main circuit unit that converts three-phase AC power, six current sensors, two for each phase of a three-phase AC current flowing through the main circuit unit, that detect magnitude of the current of each phase of the three-phase AC current, and a control device that controls operation of power conversion by the main circuit unit. The control device includes a failure detection unit that detects failure of the six current sensors, and the failure detection unit performs an in-phase current value check to check whether or not the two current sensors of the in-phase are normal and a three-phase current value check to check whether or not the detection values of the three current sensors of the respective phases are equilibrium, and detects the current sensor whose abnormality is detected in the in-phase current value check and whose imbalance is detected in the three-phase current value check as the failed current sensor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a power conversion device and a current detection device. [Background technology]

[0002] There is a power conversion device that includes a main circuit section that performs at least one of conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power, a plurality of current sensors that detect the magnitude of current of each phase of the three-phase AC current flowing in the main circuit section, and a control device that controls the operation of the main circuit section.

[0003] The control device controls the operation of the main circuit unit based on the current values ​​detected by each current sensor. Therefore, if only one current sensor is provided for each phase of the three-phase AC current, if any of the current sensors fails, the main circuit unit cannot be controlled appropriately. Therefore, in this case, the control device stops the power conversion operation by the main circuit unit in response to detection of a current sensor failure.

[0004] Therefore, it has been proposed to provide three or more current sensors for each phase of the three-phase AC current.The control device determines the current value of each phase of the three-phase AC current from the current values ​​of the three or more current sensors by a method such as taking a majority vote or an intermediate value from the current values ​​of the three or more current sensors.

[0005] As a result, even if any of the three or more current sensors fails, the remaining normal current sensors can obtain appropriate current values, thereby improving resistance to current sensor failure. Even if any of the three or more current sensors fails, the main circuit unit can continue to operate, improving the operational continuity of the main circuit unit.

[0006] However, a configuration in which three or more current sensors are provided for each phase of a three-phase AC current leads to an increase in the number of parts of the power conversion device, an increase in manufacturing costs, etc. For this reason, it is desirable to improve the resistance to current sensor failures with a simpler configuration for a power conversion device.

[0007] In addition, there is a current detection device that includes a plurality of current sensors that detect the magnitude of the current of each phase of a three-phase AC current. Similarly, in such a current detection device, it is desirable to improve the resistance to failure of the current sensors with a simpler configuration. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2017-103919 A Summary of the Invention [Problem to be solved by the invention]

[0009] The embodiments provide a power conversion device and a current detection device that can improve resistance to failure of a current sensor with a simpler configuration. [Means for solving the problem]

[0010] According to this embodiment, a power conversion device is provided that includes a main circuit unit that performs at least one of converting three-phase AC power to DC power and converting DC power to three-phase AC power, six current sensors, two for each phase of the three-phase AC current flowing through the main circuit unit, that detect the magnitude of the current of each phase of the three-phase AC current, and a control device that controls the power conversion operation by the main circuit unit based on the six current values ​​acquired by the six current sensors, wherein the control device has a fault detection unit that detects faults in the six current sensors based on the six current values, and the fault detection unit performs a common-phase current value check to confirm whether two current sensors of the same phase among the six current sensors are normal or not, and a three-phase current value check to confirm whether the detection values ​​of the three current sensors of each phase among the six current sensors are balanced or not, and detects a current sensor among the six current sensors that is detected as abnormal in the common-phase current value check and that is detected as unbalanced in the three-phase current value check as a faulty current sensor. Effect of the Invention

[0011] In the present embodiment, a power conversion device and a current detection device are provided that can improve resistance to failure of a current sensor with a simpler configuration. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram illustrating a power conversion device according to a first embodiment. [Diagram 2] 4 is a table illustrating an example of an operation of a failure detection unit according to the first embodiment. [Diagram 3] 4 is a table illustrating an example of an operation of a failure detection unit according to the first embodiment. [Figure 4] 4 is a table illustrating an example of an operation of a failure detection unit according to the first embodiment. [Diagram 5] 4 is a table illustrating an example of an operation of a failure detection unit according to the first embodiment. [Figure 6] FIG. 11 is a block diagram illustrating a current detection device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed description thereof will be omitted as appropriate.

[0014] (First embodiment) FIG. 1 is a block diagram illustrating a power conversion device according to a first embodiment. As shown in FIG. 1, the power conversion device 10 includes a main circuit unit 12, a control device 14, and six current sensors 21-26.

[0015] The main circuit section 12 performs at least one of conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power. More specifically, the three-phase AC power is symmetrical three-phase AC power. The main circuit section 12 has, for example, a transformer 30 and three converters 31 to 33. The transformer 30 has a primary winding and a secondary winding. The secondary winding is magnetically coupled to the primary winding. The primary winding of the transformer 30 is connected to a power system of the three-phase AC power. The secondary winding of the transformer 30 is connected to each of the converters 31 to 33. In other words, each of the converters 31 to 33 is connected to the power system via the transformer 30.

[0016] Each of the converters 31 to 33 is provided between each phase of a power system of three-phase AC power. For example, if the phases of the power system are U phase, V phase, and W phase, converter 31 is provided between the U phase and the V phase, converter 32 is provided between the V phase and the W phase, and converter 33 is provided between the W phase and the U phase. In other words, each of the converters 31 to 33 is delta-connected to the power system.

[0017] Each of the converters 31 to 33 has, for example, a plurality of full-bridge-connected switching elements and a charge storage element connected to the DC end of each switching element. Each of the converters 31 to 33 converts three-phase AC power of the power system into DC power by switching each switching element, stores the DC power in the charge storage element, and converts the DC power stored in the charge storage element into three-phase AC power and supplies it to the power system.

[0018] The main circuit unit 12 suppresses fluctuations in the voltage of the power system, for example, by supplying reactive power to the power system. In this example, the power conversion device 10 is a reactive power compensation device.

[0019] However, the power conversion device 10 is not limited to a reactive power compensator, and may be any power conversion device that performs at least one of conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power. The power conversion device 10 may be, for example, a power conversion device that converts DC power to three-phase AC power and supplies it to a load, or a power conversion device that converts three-phase AC power to DC power and supplies it to a load. The configuration of the main circuit unit 12 is not limited to the above, and may be any configuration that can perform at least one of conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power.

[0020] The six current sensors 21-26 detect the magnitude of current of each phase (magnitude of phase current) of the three-phase AC current flowing through the main circuit unit 12. Each of the current sensors 21-26 detects, for example, the magnitude of current of each phase of the three-phase AC current supplied from the main circuit unit 12 to the power system (load), or the magnitude of current of each phase of the three-phase AC current supplied from the power system to the main circuit unit 12. However, the current detected by each of the current sensors 21-26 is not limited to the above and may be any three-phase AC current flowing through the main circuit unit 12.

[0021] Two current sensors 21-26 are provided for each phase of the three-phase AC current flowing through the main circuit section 12. As a result, each of the current sensors 21-26 obtains two current values ​​for each phase that indicate the magnitude of the current of each phase of the three-phase AC current flowing through the main circuit section 12.

[0022] For example, current sensor 21 acquires a current value Iua representing the magnitude of the U-phase current, current sensor 22 acquires a current value Iub representing the magnitude of the U-phase current, current sensor 23 acquires a current value Iva representing the magnitude of the V-phase current, current sensor 24 acquires a current value Ivb representing the magnitude of the V-phase current, current sensor 25 acquires a current value Iwa representing the magnitude of the W-phase current, and current sensor 26 acquires a current value Iwb representing the magnitude of the W-phase current.

[0023] The current sensors 21 to 26 input the six acquired current values ​​Iua, Iub, Iva, Ivb, Iwa, and Iwb to the control device 14.

[0024] Each of the current sensors 21-26 includes, for example, a sensor body 21a-26a that detects the magnitude of a current and acquires a current value, and a communication unit 21b-26b that transmits the current value acquired by the sensor body 21a-26a to the control device 14. The sensor body 21a-26a detects the magnitude of a current flowing through, for example, an electric wire, by magnetic coupling. The sensor body 21a-26a is, for example, a current transformer. However, the configuration of each of the current sensors 21-26 is not limited to the above, and may be any configuration that can appropriately acquire the current values ​​Iua, Iub, Iva, Ivb, Iwa, and Iwb that represent the magnitude of the current of each phase of the three-phase AC current flowing through the main circuit unit 12.

[0025] The control device 14 controls the power conversion operation by the main circuit section 12. The control device 14 controls the power conversion operation by the main circuit section 12, for example, by controlling the switching of each switching element provided in each converter 31-33 of the main circuit section 12.

[0026] The control device 14 controls the power conversion operation by the main circuit unit 12 based on the six current values ​​Iua, Iub, Iva, Ivb, Iwa, and Iwb acquired by the six current sensors 21-26. For example, the control device 14 determines the magnitude of reactive power to be supplied to the power system based on the acquired current values ​​Iua, Iub, Iva, Ivb, Iwa, and Iwb, and controls the operation of the main circuit unit 12 so as to output the determined magnitude of reactive power. However, the method of controlling the main circuit unit 12 by the control device 14 is not limited to the above, and any control method may be used depending on the configuration of the main circuit unit 12, etc.

[0027] When each of the current sensors 21-26 is operating normally, the control device 14 controls the operation of the main circuit unit 12 by, for example, adopting the current value of one of the two current sensors of each phase, which is determined in advance. Furthermore, when each of the current sensors 21-26 is operating normally, the control device 14 may, for example, calculate an average value of the current values ​​of the two current sensors of each phase, and control the operation of the main circuit unit 12 based on the calculated average value. The method of controlling the main circuit unit 12 based on the current values ​​of the two current sensors provided in each phase may be any method that can appropriately control the operation of the main circuit unit 12 based on each current value.

[0028] The control device 14 has a failure detection unit 40 that detects failure of each of the current sensors 21-26 based on the current values ​​Iua, Iub, Iva, Ivb, Iwa, and Iwb acquired from each of the current sensors 21-26.

[0029] The fault detection unit 40 detects faults in the current sensors 21-26 by two checking methods, a common-phase current value check and a three-phase current value check. In detecting faults in the current sensors 21-26, the fault detection unit 40 divides the six current sensors 21-26 into two groups, an A system and a B system. For example, the fault detection unit 40 classifies the current sensors 21, 23, and 25 into the A system group and the current sensors 22, 24, and 26 into the B system group.

[0030] The in-phase current value check is a method for checking whether two in-phase current sensors among the six current sensors 21 to 26 are normal. The fault detection unit 40 sets a first threshold value ε1 for the current values ​​of the two in-phase current sensors. When the absolute value of the difference between the current values ​​of the two in-phase current sensors is equal to or greater than the first threshold value ε1, the fault detection unit 40 detects an abnormality in one of the two in-phase current sensors. The current values ​​of the two in-phase current sensors are, for example, instantaneous values. However, the current values ​​of the two in-phase current sensors may be maximum values ​​or effective values. The current values ​​of the two in-phase current sensors may be any values ​​that allow appropriate comparison of the detection values ​​of the two current sensors.

[0031] The two current sensors in the same phase are in a normal state when the absolute value of the difference between the current values ​​of the two current sensors in the same phase is less than the first threshold value ε1. The abnormal state of one of the two current sensors in the same phase is when the absolute value of the difference between the current values ​​of the two current sensors in the same phase is equal to or greater than the first threshold value ε1. The first threshold value ε1 may be set appropriately depending on, for example, the detection accuracy of each of the current sensors 21-26. In other words, the fault detection unit 40 detects an abnormality in one of the two current sensors in the same phase when an error exceeding the allowable error occurs in the current values ​​of the two current sensors in the same phase.

[0032] Specifically, the fault detection unit 40 determines that the current sensors 21, 22 are normal when |Iua-Iub|<ε1 is satisfied, and determines that one of the current sensors 21, 22 is abnormal when |Iua-Iub|≧ε1 is satisfied. The fault detection unit 40 determines that the current sensors 23, 24 are normal when |Iva-Ivb|<ε1 is satisfied, and determines that one of the current sensors 23, 24 is abnormal when |Iva-Ivb|≧ε1 is satisfied. The fault detection unit 40 then determines that the current sensors 25, 26 are normal when |Iwa-Iwb|<ε1 is satisfied, and determines that one of the current sensors 25, 26 is abnormal when |Iwa-Iwb|≧ε1 is satisfied.

[0033] The three-phase current value check is a method for checking whether or not the detection values ​​of the three current sensors of each phase among the six current sensors 21 to 26 are balanced.

[0034] Fault detection unit 40 calculates, for example, an effective value of the current of each phase of the three-phase AC current based on the current values ​​of the current sensors 21 to 26. Fault detection unit 40 calculates, for example, an effective value |Iua| of the U-phase current based on the current value Iua of current sensor 21, an effective value |Iub| of the U-phase current based on the current value Iub of current sensor 22, an effective value |Iva| of the V-phase current based on the current value Iva of current sensor 23, an effective value |Ivb| of the V-phase current based on the current value Ivb of current sensor 24, an effective value |Iwa| of the W-phase current based on the current value Iwa of current sensor 25, and an effective value |Iwb| of the W-phase current based on the current value Iwb of current sensor 26.

[0035] After calculating each of the effective values ​​|Iua|, |Iub|, |Iva|, |Ivb|, |Iwa|, |Iwb|, the fault detection unit 40 extracts the maximum and minimum values ​​from each of the effective values ​​|Iua|, |Iva|, |Iwa| of the three current sensors 21, 23, 25 in the A system group, and extracts the maximum and minimum values ​​from each of the effective values ​​|Iub|, |Ivb|, |Iwb| of the three current sensors 22, 24, 26 in the B system group.

[0036] After extracting the maximum and minimum values ​​of each effective value, the fault detection unit 40 calculates the difference between the maximum and minimum values. Then, the fault detection unit 40 sets a second threshold value ε2 for the difference between the maximum and minimum values.

[0037] The fault detection unit 40 detects that the detection values ​​of the three current sensors 21, 23, 25 in the A group are not balanced when the difference between the maximum and minimum effective values ​​of the three current sensors 21, 23, 25 in the A group is equal to or greater than the second threshold value ε2. Similarly, the fault detection unit 40 detects that the detection values ​​of the three current sensors 22, 24, 26 in the B group are not balanced when the difference between the maximum and minimum effective values ​​of the three current sensors 22, 24, 26 in the B group is equal to or greater than the second threshold value ε2.

[0038] The effective values ​​of the currents of each phase of a symmetrical three-phase AC current are substantially the same under normal conditions. Therefore, as described above, when the difference between the maximum and minimum effective values ​​of the three current sensors of each phase is equal to or greater than the second threshold value ε2, it can be considered that the detection values ​​of the three current sensors of each phase are unbalanced.

[0039] Specifically, when the maximum effective value of each of the three current sensors 21, 23, 25 in the A system group is defined as Max{|Iua|, |Iva|, |Iwa|} and the minimum effective value of each of the three current sensors 21, 23, 25 in the A system group is defined as Min{|Iua|, |Iva|, |Iwa|}, the fault detection unit 40 determines that the detection values ​​of the three current sensors 21, 23, 25 in the A system group are balanced when the following equation is satisfied. Max{|Iua|, |Iva|, |Iwa|}-α×Min{|Iua|, |Iva|, |Iwa|}<ε2

[0040] The fault detection unit 40 determines that the detection values ​​of the three current sensors 21, 23, 25 in the group A are unbalanced when the following formula is satisfied. Max{|Iua|, |Iva|, |Iwa|}-α×Min{|Iua|, |Iva|, |Iwa|}≧ε2

[0041] Similarly, when the maximum effective value of the three current sensors 22, 24, 26 in the B system group is defined as Max{|Iub|, |Ivb|, |Iwb|} and the minimum effective value of the three current sensors 22, 24, 26 in the B system group is defined as Min{|Iub|, |Ivb|, |Iwb|}, the fault detection unit 40 determines that the detection values ​​of the three current sensors 22, 24, 26 in the B system group are balanced when the following equation is satisfied. Max{|Iub|, |Ivb|, |Iwb|}-α×Min{|Iub|, |Ivb|, |Iwb|}<ε2

[0042] Then, the fault detection unit 40 determines that the detection values ​​of the three current sensors 22, 24, 26 in the group of system B are unbalanced when the following formula is satisfied. Max{|Iub|, |Ivb|, |Iwb|}-α×Min{|Iub|, |Ivb|, |Iwb|}≧ε2

[0043] As shown in the above formulas, when calculating the difference between the maximum and minimum effective values, the fault detection unit 40 corrects the minimum value by multiplying the minimum value by the correction value α. The correction value α can be calculated, for example, from the zero-phase component of the three-phase AC current. The fault detection unit 40 calculates the correction value α from, for example, the zero-phase component, and corrects the minimum value based on the calculated correction value α. This makes it possible to more appropriately check whether the detection values ​​of the three current sensors for each phase are balanced.

[0044] However, the correction value α does not necessarily have to be set. The fault detection unit 40 may calculate, for example, the following formula as the difference between the maximum value and the minimum value of each effective value. Max{|Iub|, |Ivb|, |Iwb|}-Min{|Iub|, |Ivb|, |Iwb|}

[0045] In addition, the method of checking whether the detection values ​​of the three current sensors of each phase are balanced is not limited to the above. For example, in a normal state, the sum of the instantaneous values ​​of the currents of each phase of a symmetrical three-phase AC current is substantially zero. Therefore, for example, when the absolute value of the sum of the instantaneous values ​​of the three current sensors of each phase is less than a threshold, the detection values ​​of the three current sensors of each phase may be determined to be balanced, and when the absolute value is equal to or greater than the threshold, the detection values ​​of the three current sensors of each phase may be determined to be unbalanced. The method of checking whether the detection values ​​of the three current sensors of each phase are balanced may be any method that can appropriately check whether they are balanced based on the current values ​​Iua, Iub, Iva, Ivb, Iwa, and Iwb of the current sensors 21 to 26.

[0046] 2 to 5 are tables each showing a schematic example of the operation of the failure detection unit according to the first embodiment. As shown in Figures 2 to 5, the fault detection unit 40 detects, among the current sensors 21 to 26, a current sensor in which an abnormality is detected in the in-phase current value check and an imbalance is detected in the three-phase current value check as a faulty current sensor.

[0047] For example, as shown in Figure 2, if an abnormality is detected in the two current sensors 23, 24 of the V phase and an imbalance is detected in the three current sensors 21, 23, 25 of the A system group, the current sensor 23, which is used in common to both, is detected as the faulty current sensor.

[0048] When the fault detection unit 40 detects a fault in only one of the two current sensors in the same phase, it replaces the current value of the current sensor in which the fault is detected with the current value of the other current sensor that is normal among the two current sensors in the same phase.

[0049] 3, when the failure detection unit 40 detects a failure of the current sensor 23, for example, it replaces the current value Iva of the current sensor 23 with the current value Ivb of the other current sensor 24 of the same V phase. As a result, in the control device 14, when only one of the two current sensors of the same phase fails, the main circuit unit 12 can continue the power conversion operation based on the current value of the other normal current sensor.

[0050] The fault detection unit 40 detects a fault in only one of the two current sensors in one phase, replaces the current value of the current sensor in which the fault is detected with the current value of the other current sensor in the same phase that is normal, and then resumes detecting faults in each of the current sensors 21-26 by checking the in-phase current value and the three-phase current value.

[0051] In addition, the abnormality (failure) of each of the current sensors 21-26 may be resolved as time passes. For this reason, the failure detection unit 40, for example, replaces the current value of one of the current sensors in which a failure has been detected with the current value of the other current sensor that is normal among the two current sensors in the same phase, and checks whether the current sensor in which a failure has been detected has recovered when the failure detection of each of the current sensors 21-26 is resumed by checking the in-phase current value and the three-phase current value. The failure detection unit 40 determines that the current sensor has recovered when, for example, the difference between the current value of one of the current sensors in which a failure has been detected and the current value of the other current sensor that is normal returns to less than the first threshold value ε1. When the failure detection unit 40 confirms the recovery of the current sensor in which a failure has been detected, it returns the confirmed current sensor to a normal state and ends the replacement of the current value.

[0052] After resuming detection of faults in each current sensor 21-26 by in-phase current value checks and three-phase current value checks, if the fault detection unit 40 detects a fault in only one of the two current sensors of a different phase, it similarly replaces the current value of the one current sensor in which a fault has been detected with the current value of the other normal current sensor of the two current sensors of the same phase.

[0053] As shown in FIG. 4, the fault detection unit 40, for example, detects a fault in the V-phase current sensor 23 and replaces the current value Iva of the current sensor 23 with the current value Ivb of the other current sensor 24 of the same V-phase, and then, if it detects a fault in the U-phase current sensor 22, replaces the current value Iub of the current sensor 22 with the current value Iua of the other current sensor 21 of the same U-phase.

[0054] In this way, when only one current sensor of each phase fails among the current sensors 21-26 provided two for each phase of the three-phase AC current flowing through the main circuit unit 12, the control device 14 allows the main circuit unit 12 to continue the power conversion operation based on the current value of the other current sensor. That is, in this example, even if a total of three current sensors, one for each phase, fail, the main circuit unit 12 can continue the power conversion operation.

[0055] On the other hand, if the fault detection unit 40 resumes detecting faults in each current sensor 21-26 by checking the same phase current value and the three-phase current value, and then detects a fault in the other current sensor of the same phase, the control device 14 stops the power conversion operation by the main circuit unit 12.

[0056] As shown in Figure 5, for example, when the fault detection unit 40 replaces the current value Iva of the current sensor 23 with the current value Ivb of the current sensor 24 and resumes detecting faults in each of the current sensors 21 to 26 by checking the in-phase current value and the three-phase current value, if the control device 14 detects a fault in the V-phase current sensor 24, the control device 14 stops the power conversion operation by the main circuit unit 12.

[0057] 5, when the in-phase current value checks of the U and W phases are normal and an imbalance is detected in both the A system group and the B system group, the fault detection unit 40 detects a fault in the V phase current sensor 24. When an imbalance is detected in both the A system group and the B system group, the fault detection unit 40 detects a fault in both of the two current sensors in one phase.

[0058] As described above, in the power conversion device 10 of this embodiment, the fault detection unit 40 performs a common-phase current value check to confirm whether two current sensors of the same phase among the six current sensors 21-26 are normal, and a three-phase current value check to confirm whether the detection values ​​of the three current sensors of each phase among the six current sensors 21-26 are balanced, and detects as faulty current sensors any current sensor among the six current sensors 21-26 that is detected as abnormal in the common-phase current value check and that is detected as unbalanced in the three-phase current value check.

[0059] As a result, even when the six current sensors 21-26 are provided in pairs for each phase of the three-phase AC current, failures in the six current sensors 21-26 can be appropriately detected. Therefore, in the power conversion device 10 according to the present embodiment, an increase in the number of parts and an increase in manufacturing costs can be suppressed compared to a configuration in which three or more current sensors are provided for each phase of the three-phase AC current. In the power conversion device 10 according to the present embodiment, the resistance to failures of the current sensors can be improved with a simpler configuration. In the power conversion device 10 according to the present embodiment, the operation continuity of the main circuit unit 12 against failures of the current sensors can be improved with a simpler configuration.

[0060] In the power conversion device 10 according to the present embodiment, when the control device 14 detects a failure in only one of two current sensors of the same phase among six current sensors 21-26 provided for each phase of the three-phase AC current, the control device 14 continues the operation of power conversion by the main circuit unit 12 based on the current value of the other current sensor, and when the control device 14 detects failures in both of the two current sensors of the same phase, the control device 14 stops the operation of power conversion by the main circuit unit 12. This makes it possible to appropriately continue the operation of the main circuit unit 12 even when a failure is detected in only one of the two current sensors of the same phase, and to appropriately stop the operation of the main circuit unit 12 in response to the detection of failures in both of the two current sensors of the same phase.

[0061] In the power conversion device 10 according to the present embodiment, when the fault detection unit 40 detects a fault in only one of the two current sensors in the same phase, it replaces the current value of the one current sensor in which the fault is detected with the current value of the other current sensor in the normal state of the two current sensors in the same phase, and resumes fault detection of the six current sensors 21-26 by checking the in-phase current value and the three-phase current value, thereby enabling the main circuit unit 12 to continue the operation of power conversion based on the current value of the other normal current sensor. This allows the main circuit unit 12 to continue operation more appropriately even when a fault is detected in only one of the two current sensors in the same phase.

[0062] In the power conversion device 10 according to the present embodiment, the fault detection unit 40 replaces the current value of one of the current sensors that has detected a fault with the current value of the other current sensor that is normal, and when the fault detection of the six current sensors 21 to 26 by the in-phase current value check and the three-phase current value check is resumed, the one of the current sensors that has detected a fault is checked for recovery, and when the recovery is confirmed, the one of the current sensors is returned to a normal state and the replacement of the current value is terminated. This can further improve the resistance to faults in the current sensors. The operation continuity of the main circuit unit 12 can further be improved.

[0063] In the power conversion device 10 according to the present embodiment, the fault detection unit 40 detects an abnormality in one of the two current sensors in the same phase when the absolute value of the difference between the current values ​​of the two current sensors in the same phase is equal to or greater than a threshold value in the in-phase current value check. This makes it possible to appropriately detect an abnormality in one of the two current sensors in the same phase.

[0064] In the power conversion device 10 according to the present embodiment, the fault detection unit 40 detects that the detection values ​​of the three current sensors are not balanced when the difference between the maximum and minimum effective values ​​of the three current sensors of each phase is equal to or greater than a threshold value during a three-phase current value check. This makes it possible to appropriately detect that the detection values ​​of the three current sensors are not balanced.

[0065] Second Embodiment FIG. 6 is a block diagram illustrating a current detection device according to the second embodiment. As shown in FIG. 6, the current detecting device 100 includes six current sensors 111 to 116 and a fault detecting unit 120. The current detecting device 100 includes six current sensors 111 to 116 and a fault detecting unit 120.

[0066] The six current sensors 111-116 are provided, two for each phase of the three-phase AC current, and detect the magnitude of the current of each phase of the three-phase AC current. The six current sensors 111-116 may be the same as the current sensors 21-26 described in relation to the first embodiment.

[0067] The fault detection unit 120 detects faults in the six current sensors 111-116 based on the six current values ​​acquired by the six current sensors 111-116. As with the fault detection unit 40 described in relation to the first embodiment, the fault detection unit 120 performs a common-phase current value check to check whether two current sensors of the same phase among the six current sensors 111-116 are normal, and a three-phase current value check to check whether the detection values ​​of the three current sensors of each phase among the six current sensors 111-116 are balanced, and detects, as a faulty current sensor, a current sensor that is detected as abnormal in the common-phase current value check and is detected as unbalanced in the three-phase current value check among the six current sensors 111-116.

[0068] As a result, in the current detection device 100 according to this embodiment, similarly to the power conversion device 10 of the first embodiment, it is possible to improve resistance to current sensor failure with a simpler configuration. Even when only one of the two current sensors of the same phase fails, the other current sensor that is normal can continue to appropriately detect the magnitude of the current of each phase of the three-phase AC current.

[0069] The three-phase AC currents detected by the six current sensors 111 to 116 are not limited to the three-phase AC currents flowing through the main circuit of the power conversion device, but may be any three-phase AC current. The current detection device 100 is applicable to the detection of any three-phase AC current.

[0070] The fault detection unit 120 may be provided as a separate device, or may be incorporated in another device such as a control device, like the fault detection unit 40 in the first embodiment. The power conversion device 10 in the first embodiment can also be expressed as including the current detection device 100.

[0071] The present embodiment includes the following aspects. (Appendix 1) a main circuit unit that performs at least one of conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power; six current sensors, two for each phase of the three-phase AC current flowing through the main circuit section, for detecting the magnitude of each phase of the three-phase AC current; a control device that controls an operation of converting power by the main circuit unit based on the six current values ​​acquired by the six current sensors; Equipped with the control device has a fault detection unit that detects faults in the six current sensors based on the six current values; The fault detection unit performs a common-phase current value check to check whether two current sensors of the same phase among the six current sensors are normal, and a three-phase current value check to check whether the detection values ​​of the three current sensors of each phase among the six current sensors are balanced, and detects as a faulty current sensor any current sensor among the six current sensors that is detected as abnormal in the common-phase current value check and is detected as unbalanced in the three-phase current value check.

[0072] (Appendix 2) The power conversion device described in Appendix 1, wherein when the control device detects a failure in only one of two current sensors of the same phase out of six current sensors provided, two for each phase of the three-phase AC current, the control device continues the power conversion operation by the main circuit unit based on the current value of the other current sensor, and when the control device detects a failure in both of the two current sensors of the same phase, the control device stops the power conversion operation by the main circuit unit.

[0073] (Appendix 3) A power conversion device as described in Appendix 2, wherein, when the fault detection unit detects a fault in only one of the two current sensors of the same phase, it replaces the current value of the one current sensor where the fault has been detected with the current value of the other current sensor of the two current sensors of the same phase that is normal, and resumes detection of faults in the six current sensors by the in-phase current value check and the three-phase current value check, thereby enabling the main circuit unit to continue performing power conversion operation based on the current value of the other current sensor that is normal.

[0074] (Appendix 4) The power conversion device described in Appendix 3, wherein the fault detection unit replaces the current value of the one of the current sensors in which a fault has been detected with the current value of the other current sensor which is normal, and when detection of faults in the six current sensors is resumed by the in-phase current value check and the three-phase current value check, checks whether the one of the current sensors in which a fault has been detected has recovered, and when recovery is confirmed, returns the one of the current sensors to a normal state and terminates the replacement of the current values.

[0075] (Appendix 5) The power conversion device according to any one of appendices 1 to 4, wherein the fault detection unit detects an abnormality in one of the two current sensors in the same phase when the absolute value of the difference in current values ​​between the two current sensors in the same phase is greater than or equal to a threshold value during the in-phase current value check.

[0076] (Appendix 6) The power conversion device according to any one of appendices 1 to 5, wherein the fault detection unit detects that the detection values ​​of the three current sensors are not balanced when the difference between the maximum and minimum effective values ​​of the three current sensors of each phase is equal to or greater than a threshold value during the three-phase current value check.

[0077] (Appendix 7) Six current sensors, two for each phase of a three-phase AC current, for detecting the magnitude of each phase of the three-phase AC current; a fault detection unit that detects faults in the six current sensors based on six current values ​​acquired by the six current sensors; Equipped with The fault detection unit performs a common-phase current value check to check whether two current sensors of the same phase among the six current sensors are normal, and a three-phase current value check to check whether the detection values ​​of the three current sensors of each phase among the six current sensors are balanced, and detects as faulty current sensors any current sensor among the six current sensors that is detected as abnormal in the common-phase current value check and is detected as unbalanced in the three-phase current value check.

[0078] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments can be implemented in combination with each other. [Explanation of symbols]

[0079] REFERENCE SIGNS LIST 10...power conversion device, 12...main circuit section, 14...control device, 21-26...current sensor, 30...transformer, 31-33...converter, 40...fault detection section, 100...current detection device, 111-116...current sensor, 120...fault detection section

Claims

1. a main circuit unit that performs at least one of conversion from three-phase AC power to DC power and conversion from DC power to three-phase AC power; six current sensors, two for each phase of the three-phase AC current flowing through the main circuit section, for detecting the magnitude of each phase of the three-phase AC current; a control device that controls an operation of converting power by the main circuit unit based on the six current values ​​acquired by the six current sensors; Equipped with the control device has a failure detection unit that detects failures in the six current sensors based on the six current values, The fault detection unit performs a common-phase current value check to check whether two current sensors of the same phase among the six current sensors are normal, and a three-phase current value check to check whether the detection values ​​of the three current sensors of each phase among the six current sensors are balanced, and detects as a faulty current sensor any current sensor among the six current sensors that is detected as abnormal in the common-phase current value check and is detected as unbalanced in the three-phase current value check.

2. 2. The power conversion device according to claim 1, wherein, when the control device detects a failure in only one of two current sensors of the same phase out of six current sensors provided, two for each phase of the three-phase AC current, the control device continues the power conversion operation by the main circuit unit based on the current value of the other current sensor, and when the control device detects a failure in both of the two current sensors of the same phase, the control device stops the power conversion operation by the main circuit unit.

3. The power conversion device of claim 2, wherein when the fault detection unit detects a fault in only one of the two current sensors of the same phase, it replaces the current value of the one current sensor where the fault has been detected with the current value of the other current sensor of the two current sensors of the same phase that is normal, and resumes detection of faults in the six current sensors by the same-phase current value check and the three-phase current value check, thereby enabling the main circuit unit to continue performing power conversion operation based on the current value of the other current sensor that is normal.

4. The power conversion device of claim 3, wherein the fault detection unit replaces the current value of the one current sensor in which a fault has been detected with the current value of the other current sensor which is normal, and when detection of faults in the six current sensors is resumed by the in-phase current value check and the three-phase current value check, checks whether the one current sensor in which a fault has been detected has recovered, and when recovery is confirmed, returns the one current sensor to a normal state and terminates the replacement of the current values.

5. The power conversion device according to claim 1 , wherein the fault detection unit detects an abnormality in one of the two current sensors of the same phase when the absolute value of the difference between the current values ​​of the two current sensors of the same phase is equal to or greater than a threshold value during the in-phase current value check.

6. The power conversion device according to claim 1, wherein the fault detection unit detects that the detection values ​​of the three current sensors are not balanced when, during the three-phase current value check, the difference between the maximum and minimum effective values ​​of the three current sensors of each phase is equal to or greater than a threshold value.

7. six current sensors, two for each phase of a three-phase AC current, for detecting a magnitude of a current of each phase of the three-phase AC current; a fault detection unit that detects faults in the six current sensors based on six current values ​​acquired by the six current sensors; Equipped with The fault detection unit performs a common-phase current value check to check whether two current sensors of the same phase among the six current sensors are normal, and a three-phase current value check to check whether the detection values ​​of the three current sensors of each phase among the six current sensors are balanced, and detects as a faulty current sensor any current sensor among the six current sensors that is detected as abnormal in the common-phase current value check and is detected as unbalanced in the three-phase current value check.

Images