Inverter device that has a function for detecting a defect in a power component, and method for detecting a defect in a power component

Abstract

Inverter unit (100) comprising the following: a converter (1) comprising a plurality of power components configured to convert an alternating voltage supplied by a power supply (20) into a direct voltage and output the direct voltage; a DC link capacitor (2) connected to an output side of the inverter (1); a voltage detector (3) configured to detect a voltage of the DC link capacitor (2); a charging circuit (4) arranged between the inverter (1) and the DC link capacitor (2), configured to charge the DC link capacitor (2); a charging circuit control device (5) configured to control a first switch (42) connected in parallel with a charging resistor (41) in the charging circuit (4); a current detector (6) configured to detect a current flowing between the inverter (1) and the DC link capacitor (2); a switch-on control device (7) configured to control the switching on of the power components of the inverter (1); a second switch (8) configured to connect or disconnect the power supply (20) and inverter (1); a power supply monitor (9) configured to control the switching of the second switch (8) and to monitor a connection state between the power supply (20) and the inverter (1) by detecting a voltage to be input into the inverter (1); a threshold adjuster (10) configured to set a first threshold or a second threshold to determine the presence or absence of a defect in the power components, and a fault detector (11) configured to determine the presence or absence of a fault in the power components by comparing a current flowing when the power component of the inverter (1) is switched on using electrical charge of the DC-link capacitor (2) immediately after the second switch (8) has disconnected the power supply (20) from the inverter (1) and the second switch (8) has been switched off, with the first threshold or the second threshold.

Description

STATE OF THE ART 1. Field of the invention

[0001] The present invention relates to a converter device having a function for detecting a defect in a power component, and a method for detecting a defect in the power component. 2. Description of the related technology

[0002] A common method for driving a motor using a motor drive device involves converting an alternating current (AC) voltage supplied by a main power supply into a direct current (DC) voltage using a converter containing a power transistor (power component). This DC voltage is then further converted back into an AC voltage to drive the motor using an inverter. If the power transistor is faulty, supplying AC current from the main power supply to the power transistor can damage the motor drive device. Therefore, before supplying AC current from the main power supply to the converter, it is essential to check for the presence or absence of a fault in the power transistor.

[0003] Methods for detecting a power transistor defect in an inverter have been reported (for example, unexamined Japanese patent publication (Kokai) No. JP H08-80056A). In the conventional method for detecting a power transistor defect, an inverter has current detectors, the number of which is at least one less than the number of power transistor pairs, to detect the amounts of current flowing through the motor windings. In this method, prior to the operation, the power transistors are switched on and off in specific sequences and combinations while a low voltage is applied to the inverter containing the power transistor. The current detectors detect currents flowing through the motor windings of each phase.Whether a power transistor is defective, and which power transistor is defective, is determined based on the current levels, the switching sequence, and combinations thereof. JP H11-332 257 A discloses an inverter in which safety is ensured by preventing damage caused by a short-circuited power element. The presence or absence of a short circuit in the element is determined by a decision circuit and a control unit based on a change in current. An alarm is triggered upon detection of a fault. BRIEF SUMMARY OF THE INVENTION

[0004] In the case of an inverter device, inputting a switch-on signal into power components while they are switched on can cause a short circuit and can damage the inverter device.

[0005] An inverter device according to an embodiment of this disclosure comprises: an inverter having a plurality of power components configured to convert an alternating voltage supplied by a power supply into a direct voltage and to output the direct voltage; a DC link capacitor connected to an output side of the inverter; a voltage detector configured to detect the voltage of the DC link capacitor; a charging circuit arranged between the inverter and the DC link capacitor, configured to charge the DC link capacitor; a charging circuit control device configured to control a first switch connected in parallel with a charging resistor in the charging circuit; and a current detector configured to detect a current flowing between the inverter and the DC link capacitor.a power-on control device configured to control the power-on of the inverter's power components; a second switch configured to connect or disconnect between the power supply and the inverter; a power supply monitor configured to control the switching of the second switch and to monitor the connection status between the power supply and the inverter by detecting a voltage input to the inverter;a threshold adjuster configured to set a first threshold or a second threshold to determine the presence or absence of a power component defect, and a defect detector configured to determine the presence or absence of a power component defect by comparing a current flowing to the inverter's power component upon switching on, using the electrical charge of the DC-link capacitor, immediately after the second switch has disconnected the power supply from the inverter and the second switch has been turned off, with the first threshold or the second threshold.

[0006] A method for detecting a defect in a power component according to the embodiment of this disclosure is a method for detecting a defect in an inverter device comprising: an inverter having a plurality of power components configured to convert an alternating voltage supplied by a power supply into a direct voltage and output the direct voltage; a DC link capacitor connected to an output side of the inverter; a current detector configured to detect a current flowing between the inverter and the DC link capacitor; and a switch configured to connect or disconnect the power supply and the inverter.The procedure comprises the following: connecting the power supply to the inverter by closing the switch; charging the DC-link capacitor; after the connection and charging steps, controlling the switch to an open state to disconnect the power supply from the inverter; detecting a current flowing between the inverter and the DC-link capacitor immediately after the power supply has been disconnected from the inverter, and determining the presence or absence of a power component failure by comparing the detected current with a first threshold or a second threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The tasks, features, and advantages of the present invention will become clearer from the following description of a preferred embodiment in conjunction with the accompanying drawings. The drawings show: isFig. 1 a block diagram of an inverter device according to an embodiment, is Fig. 2 a drawing showing an example of a current path when fault detection is performed in the inverter device according to the embodiment; is Fig. 3 a flowchart of a defect detection process in the event of an interruption by a method for detecting a defect of the inverter device according to the embodiment, and is Fig. 4 a flowchart of a short-circuit defect detection process by a method for detecting a defect in the inverter device according to a modification example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A converter device that has the function of detecting a defect in a power component and a method for detecting a defect in the power component according to the present invention are described below with reference to the drawings. However, the technical scope of protection of the present invention is not limited to its embodiments, but includes the invention described in claims and its equivalents.

[0009] A converter device that has the function of detecting a defect in a power component according to an embodiment of this disclosure is described. Fig. Figure 1 is a block diagram of a converter device according to one embodiment. A converter device 100 comprises a DC link capacitor 2, a voltage detector 3, a charging circuit 4, a charging circuit control device 5, a current detector 6, a switch-on control device 7, a switch 8, a power supply monitor 9, a threshold adjuster 10, and a fault detector 11.

[0010] The inverter has a plurality of (for example, six) power components (Tr1 to Tr6). The inverter 1 selectively switches on the power components (Tr1 to Tr6) such that an alternating voltage supplied by a power supply 20 is converted into a direct voltage, which is to be output in order to carry out a power regeneration process. As in Fig. As shown in Figure 1, a plurality (for example, six) of diodes (D1 to D6) are preferably connected to the power components (Tr1 to Tr6) in an antiparallel configuration. The power components (Tr1 to Tr6) can be transistors, FETs, IGBTs, etc.

[0011] The DC link capacitor 2 is connected to the output side of the inverter 1. The DC link capacitor 2 smooths the DC voltage output by the inverter 1. The smoothed DC voltage is supplied to a motor drive device (not shown).

[0012] The voltage detector 3 detects the voltage of the DC-link capacitor 2. More precisely, a voltage sensor 31, connected between both terminals of the DC-link capacitor 2, detects the voltage across the DC-link capacitor 2 and sends a detection result to the voltage detector 3. The voltage of the DC-link capacitor 2 received by the voltage detector 3 is output to the fault detector 11.

[0013] The charging circuit 4, which is arranged between the inverter 1 and the DC-link capacitor 2, charges the DC-link capacitor 2. When the DC-link capacitor 2 is charged, a switch 42 of the charging circuit 4 is switched off. The DC-link capacitor 2 is therefore charged via a charging resistor 41, while a large current flow into the DC-link capacitor 2 is prevented.

[0014] The charging circuit control device 5 controls the switch 42, which is connected in parallel with the discharge resistor 41 in the charging circuit. As described above, the charging circuit control device 5 switches off the switch 42 when the DC-link capacitor 2 is charged. After the DC-link capacitor 2 has finished charging, the charging circuit control device 5 switches on the switch 42. If a fault is detected in the power components as described below, the charging circuit control device 5 switches off the switch 42 so that no excessive current flows through the power components.

[0015] The current detector 6 detects a current flowing between the inverter 1 and the DC-link capacitor 2. More precisely, a current sensor 61 is provided between the inverter 1 and the DC-link capacitor 2, and the current value detected by the current sensor 61 is sent to the current detector 6. The current value received by the current detector 6 is output to the fault detector 11.

[0016] The switch-on control device 7 controls the switching on of the power components (Tr1 to Tr6) of the inverter 1. The inverter 1 selectively switches on the power components (Tr1 to Tr6) in accordance with a signal from the switch-on control device 7 in order to convert an AC voltage supplied by the power supply 120 into a DC voltage to be output and to perform a power regeneration process.

[0017] Switch 8 connects or disconnects the power supply 20 and the inverter 1. Switch 8 has three switches, each of which corresponds to one phase of the power supply 20, i.e. a three-phase AC power supply. Fig. Figure 1 shows an example of using the three-phase AC power supply as the power supply 20. However, the power supply is not limited to a three-phase AC supply, but can be a single-phase AC supply.

[0018] The power supply monitor 9 controls the switching of the switch 8 while sensing a voltage input to the inverter 1 to monitor the connection status between the power supply 20 and the inverter 1. The fault detector 11 is informed of the switching control status of the switch 8 by the power supply monitor 9. The switch 8 can be an electromagnetic switch, etc.

[0019] By closing switch 8 (setting switch 8 to a closed position), the power supply 20 is connected to the inverter 1, so that an AC voltage is supplied to the inverter 1. At this time, the inverter 1 converts the AC voltage into a DC voltage. The DC voltage is applied to the DC link capacitor 2 and charges the DC link capacitor 2.

[0020] By opening switch 8 (setting switch 8 to an open position), inverter 1 is disconnected from the power supply 20. Electrical charge that has accumulated in the DC link capacitor 2 is discharged.

[0021] The threshold setter 10 sets a first threshold I TH1 and a second threshold I TH2 one, to determine the presence or absence of a defect in the power components (Tr1 to Tr6). The first threshold I TH1is a threshold value for detecting an interruption defect in the power components (Tr1 to Tr6). The second threshold value I TH2 is a threshold value for detecting a short-circuit defect in the power components (Tr1 to Tr6). The threshold adjuster 10 can set the first threshold value I TH1 and the second threshold I TH2 Rewrite the thresholds in accordance with an externally input signal. The rewritable thresholds offer the advantage that defect detection can be performed in accordance with usage conditions.

[0022] The fault detector 11 compares a current flowing on the switching on of the power components of the inverter 1 using electrical power from the DC-link capacitor 2, immediately after the switch 8 has disconnected the power supply 20 from the inverter 1 and the switch 42 has been switched off, with the first threshold value I TH1and the second threshold I TH2 , to determine the presence or absence of a defect in the power components.

[0023] Fig. Figure 2 shows an example of a current path when fault detection is implemented in the inverter device according to the embodiment. As in Fig. As shown in Figure 2, the power components are switched on using electrical charge accumulated in the DC link capacitor 2 immediately after the power supply 20 is disconnected from the inverter 1, and a fault in the power devices is detected by the current flowing. Of the six power components (Tr1 to Tr6) of the inverter 1, power components Tr1, Tr3, and Tr5 are power components for an upper branch 101, and power components Tr2, Tr4, and Tr6 are power components for a lower branch 102. Furthermore, in the case of a 3-phase AC circuit, power components Tr4 and Tr2 can be U-phase components, power components Tr3 and Tr4 can be V-phase power components, and power components Tr5 and Tr6 can be W-phase power components. As shown in Fig. As shown in Figure 2, the power component Tr4 of the upper branch and the power component Tr2 of the lower branch of the same phase, for example the U-phase, are switched on simultaneously, and the presence or absence of an open circuit defect in the power components is determined from the current flowing. For example, if a current such as that shown by arrow A of the Fig. If the current specified in 2 flows, it is determined that the inverter device 100 is normal. On the other hand, if a current detected by the current sensor 61 is equal to or less than the first threshold I TH1 , it is determined that the inverter unit 100 has an interruption defect.

[0024] When the power-on control device 7 switches on the power components, the charging circuit control device 5 preferably controls the charging circuit 4 such that no excessive current flows through the power components. In other words, fault detection in the power components is performed by switching on the DC-link capacitor 2 and the power components (Tr1 to Tr6) of the upper and lower branches (101 and 102) immediately after the power supply 20 is disconnected from the inverter 1. At this time, the switch 42 of the charging circuit 4 is preferably off to limit the current flowing through the power components. This is because, if no current-limiting element is provided, the DC-link capacitor 2 would simply short-circuit across both terminals, and the short circuit could damage the power components (Tr1 to Tr6).

[0025] Furthermore, in accordance with the current flowing when a power component (for example, Tr1) of any upper branch 101 and lower branch 102 of the inverter 1 is switched on, the fault detector 11 can detect the presence or absence of a short-circuit fault in another power component (for example, Tr2) of the other upper branch 101 and lower branch 102. In the example of the Fig. 2. Tr4 is switched on, while Tr2 is switched off. If Tr2 is functioning normally, no current flows through Tr2, so the current sensor 61 does not detect any current. On the other hand, if the current sensor 61 detects a current I of a certain amount or more (>I TH2 ) detected, even though Tr2 is switched off, it is determined that Tr2 has a short-circuit defect.

[0026] As described above, according to this embodiment, the inverter device can determine the presence or absence of an open circuit defect and a short circuit defect of the power components based on the current flowing to the power components or element upon switching on, using electrical charge accumulated in the DC link capacitor immediately after the power supply has been disconnected from the inverter.

[0027] If an open circuit or short circuit fault in the power component is detected, the fault detector 11 can issue a notification of the occurrence of an irregularity using a lamp, an alarm signal, etc. Since the operator is thereby informed of the occurrence of the irregularity in the power components, the inverter device is prevented from being re-energized.

[0028] A method for detecting an interruption defect in power components using the inverter device according to this embodiment is now described. Fig. Figure 3 is a flowchart of a defect detection process in the method for detecting an open circuit defect in the power components of the inverter device according to the embodiment. At step S101, the power supply monitor 9 closes the switch 8 to connect the power supply 20 to the inverter 1. Therefore, an AC voltage supplied by the power supply 20 to the inverter 1 is converted into a DC voltage, and the DC voltage is output to the DC link capacitor 2.

[0029] Then, at step S102, the DC link capacitor 2 is charged. The DC link capacitor 2 is charged until the voltage across it equals the DC voltage output by the inverter 1. After this point, the motor drive device is in a functional state.

[0030] Then, at step S103, the power supply monitor 9 controls switch 8 so that it is set to the open position. While switch 42 is off, a turn-on signal is output to the power components. More precisely, the turn-on signal is output in such a way that only the power component of the upper branch and the power component of the lower branch connected to the same phase are switched on. Step S103 is preferably executed after a period of time, during which the DC-link capacitor 2 is assumed to be sufficiently charged, has elapsed since switch 8 was set to the closed position at step S101. A case in which a command, such as an emergency stop command, is entered after the motor control device, etc., has been operated, can be given as a concrete example.

[0031] Then, at step S104, the current I DCThe current flowing between inverter 1 and DC link capacitor 2 is detected. While power supply monitor 9 sets switch 8 to the open state, it informs fault detector 11 of the control signal that set switch 8 to the open state. Upon receiving this signal, fault detector 11 receives a current detection result. DC , which flows between the inverter 1 and the DC link capacitor 2, from the current detector 6.

[0032] Then, at step S105, the defect detector 11 determines whether the current I DC , which flows between the inverter 1 and the DC link capacitor 2, is greater than a first threshold value I TH1 If I DC is greater than the first threshold I TH1It is determined that the power components have no open-circuit defects. In this case, the defect detector 11 therefore determines at step S106 that the power components of the inverter unit 100 are functioning normally.

[0033] Conversely, if I DC is equal to or less than the first threshold I TH1 , it is determined that the power components have an open-circuit defect. In this case, the defect detector 11 therefore determines at step S107 that the power components of the inverter unit 100 have an open-circuit defect.

[0034] A method for detecting a short-circuit defect in a power component using the inverter device according to this embodiment is now described. Fig. Figure 4 is a flowchart of a short-circuit fault detection process by the method for detecting a short-circuit fault of the inverter device according to an amendment example of this embodiment. Steps S201 and S202 are the same as steps S101 and S102 of the open-circuit fault detection process described above. In step S203, a power component of any one of the upper branch and lower branch of the inverter 1 is switched on immediately after the power supply 20 has been disconnected from the inverter 1 and the switch 42 has been turned off. Fig. 2 For example, the upper branch of the U-phase power component Tr4 is switched on, while the other power components Tr2 to Tr6 are kept in a switched-off state.

[0035] At step S204, a current I DC The current flowing between inverter 1 and DC link capacitor 2 is measured. The measured current value I DCis sent to the defect detector 11.

[0036] Then, in step S205, it is recorded whether the current I DC is smaller than a second threshold I TH2 If the current I DC is equal to or greater than the second threshold I TH2 , in step S206 it is determined that the power component of the inverter device 100 has a short-circuit defect.

[0037] Conversely, if the current I DC is smaller than the second threshold I TH2 , it is determined that the power component of the inverter device is 100 normal.

[0038] As described above, the method for detecting a defect according to the amendment example of this embodiment can detect the presence or absence of a short-circuit defect of the power component for one of the upper branch and the lower branch of the converter in accordance with a current flowing when the power component of the upper branch and the power component of the lower branch are switched on.

[0039] The converter device, which has the function of detecting a defect in the power component and a method for detecting a defect in the power component according to the embodiment of this disclosure, allows the detection of the presence or absence of an irregularity in the power components of the converter device.

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