Converter device with a function for detecting a short-circuit defect, and method for detecting a short-circuit defect in a converter device

Abstract

Converter device (101) comprising: a rectifier circuit (1) that converts and outputs an alternating current voltage supplied by a power source (10) into a direct current voltage; a DC link capacitor (2) connected to the output side of the rectifier circuit (1); a voltage detection section (3) that detects the voltage of the DC link capacitor (2); a switching section (4) that connects or disconnects the power source (10) and the rectifier circuit (1); a switching actuation section (5) that monitors irregularities in a motor drive device comprising the converter device (101) and an inverter device connected to the converter device (101) and transmits instructions to the switching section;a current source monitoring section (6) that detects the voltage applied to the rectifier circuit (1) and monitors the state of the connection between the current source (10) and the rectifier circuit (1); a threshold setting section (7) that sets a threshold for determining the presence or absence of a short-circuit defect; and a short-circuit defect detection section (8) that determines that a short-circuit defect has occurred in the converter device (101) when the voltage of the DC link capacitor (2), detected immediately after the current source (10) is disconnected from the rectifier circuit (1) by the switching section (4), is at most the threshold value, wherein the threshold setting section (7) is configured to adjust the threshold value depending on the magnitude of the DC voltage output by the rectifier circuit (1).

Description

Background of the Invention Field of the Invention

[0001] The present invention relates to a converter device having the function of detecting a short-circuit defect, and a method for detecting a short-circuit defect in a converter device. Description of the prior art

[0002] As a method of driving a motor by a motor driving device, a method in which a motor is driven after an AC voltage inputted from a main power source is converted into a DC voltage by a converter and this is converted into an AC voltage by an inverter is well known. In addition, a DC link capacitor is usually provided to smooth the DC voltage output from the converter. If the AC power is applied from the main power source in a state where an abnormality has occurred in the main circuit or the AC link capacitor, there is a risk that the motor drive device will be damaged. For example, when the main power source is turned on in a state where the DC link capacitor is short-circuited, since a large current flows in the converter, there is a risk that the motor drive device will be damaged. Therefore, it is important to detect whether or not the DC link capacitor is short-circuited before the AC power is applied from the main power source.

[0003] Heretofore, a motor drive device provided with the function of detecting an abnormality in the DC link portion has been known (see, for example, Patent Laid-Open No. 2014-217085). This conventional motor drive device includes a converter section that converts an AC voltage inputted from a main power source into a DC voltage; a DC link section that rectifies the DC voltage output from the converter section; an inverter section that converts the DC voltage rectified by the DC link section into an AC voltage by semiconductor switching elements to drive a motor; a voltage application section that is formed independently of the main power source and applies a voltage to the DC link; a voltage detection section that detects the voltage of the DC link section after the voltage is applied by the voltage application section; and an abnormality determination section that detects the presence or absence of an abnormality in the DC link section based on measured values ​​of the voltage over a certain period of time detected by the voltage detection section and a rate of change of the voltage over time. Summary of the Invention

[0004] However, in the conventional motor drive device, it is necessary to form a voltage application section independent of the power source.

[0005] A converter device according to an embodiment of the present disclosure includes a converter that converts an AC voltage supplied from a power source into a DC voltage and outputs it; a DC link capacitor connected to the output side of the converter; a voltage detection section that detects the voltage of the DC link capacitor; a switching section that connects or disconnects the power source and the converter; a shift operation section that monitors abnormalities of a motor drive device including the converter device and an inverter device connected to the converter device and transmits instructions to the shift section; a power source monitoring section that detects the voltage input to the converter and monitors the state of connection between the power source and the converter; a threshold value setting section that sets a threshold value for determining the existence or nonexistence of a short-circuit defect; and a short-circuit defect detection section that determines that a short-circuit defect has occurred when the voltage of the DC link capacitor is at most the threshold value immediately after the switching section disconnects the power source from the converter.

[0006] A method for detecting a short-circuit defect in a converter device according to an embodiment of the present disclosure is a method for detecting a short-circuit in a converter device that includes a converter that converts an AC voltage supplied from a power source into a DC voltage and outputs; a DC link capacitor connected to the DC output side of the converter; a voltage detection section that detects the voltage of the DC link capacitor; a switching section that controls supply of the AC voltage from the power source to the converter; and a switching operation section that monitors abnormalities of a motor drive device including the converter device and an inverter device connected to the converter device and gives instructions to the switching section, wherein the switching section is brought into an off state by the switching operation section and the power source is disconnected from the converter, when any abnormality occurs during the operation of the motor drive apparatus, the voltage of the DC link capacitor is detected by the switching section from the converter immediately after the power source is disconnected, and it is determined that the abnormality that occurred previously is caused by a short-circuit defect of the main circuit when the detected voltage of the DC link capacitor is at most a threshold. Simple explanation of the drawings

[0007] The objects, features and advantages of the present invention will become more clear from the following description of embodiments in connection with the accompanying drawings. In these accompanying drawings is figure 1 is a structural view of a converter device according to an embodiment; is figure 2 is a flow chart for explaining the sequence of detecting a short-circuit defect by the short-circuit defect detection method of the converter device according to an embodiment; is figure 3 is a graph showing the change with time in the voltage of the DC link capacitor when the main circuit of the converter device is in the normal state; and is figure 4 is a graph showing the change with time in the voltage of the DC link capacitor when the main circuit of the converter device has a short-circuit defect. Detailed explanation of the invention

[0008] A converter device having the function of detecting a short-circuit defect and a method of detecting a short-circuit defect in a converter device according to the present invention will be explained below with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these modes but extends to the inventions specified in the claims and their equivalents.

[0009] First, the converter device having the short-circuit defect detection function according to an embodiment of the present disclosure will be explained. figure 1 is a structural view showing the converter device according to the embodiment. The converter device 101 according to the embodiment comprises a converter 1 , a DC link capacitor 2, a voltage detecting section 3, a switching section 4 , a switch operation section 5, a power source monitoring section 6 , a threshold setting section 7 , and a short-circuit defect detection section 8.

[0010] The shifter 1 converts one from a power source 10 supplied AC voltage into a DC voltage and outputs it. For example, the converter can be implemented as a three-phase full-wave rectifier circuit constructed by six diodes.

[0011] The DC link capacitor 2 is on the output side of the converter 1 connected. The DC link capacitor 2 smooths that from the converter 1 output DC voltage.

[0012] The voltage detection section 3 detects the voltage of the DC link capacitor 2 . The voltage of the DC link capacitor 2 detected by the voltage detection section 3 is output to the short-circuit defect detection section 8 .

[0013] The switching section 4 connects or disconnects the power source 10 and the converter 1 . Here includes the switching section 4 three switches that control each phase of the power source 10 , which is a three-phase AC power source. In figure 1 shows an example using a three-phase AC power source as the power source 10 is used, but the power source is not limited to a three-phase AC power source but may be a single-phase AC power source.

[0014] The shift operation section 5 detects the state of a motor drive device including the converter device and an inverter device connected to the converter device, and when an abnormality occurs in these elements, quickly sends a command to the switching section 4 and brings the switching section 4 to an off state.

[0015] The power source monitoring section 6 detects those in the converter 1 introduced voltage and monitors the connection status between the power source 10 and the converter 1 . Through the power source monitoring section 6 the state of the switching section 4 is notified to the short-circuit defect detecting section 8 . For the switching section 4 an electromagnetic contactor or the like can be used.

[0016] If the switching section 4 is brought into the closed state (on state) by an instruction from the switch operation section 5, becomes the power source 10 with the converter 1 connected and becomes the converter 1 supplied an AC voltage. The shifter 1 converts the AC voltage into a DC voltage, and the DC voltage is applied to the DC link capacitor 2, and after its charging is done, the motor drive device comes into the operable state.

[0017] If the switching section 1 on the other hand, by an instruction from the shift operation section 5 is brought into the open state (off state), the converter1 from the power source 1 Cut.

[0018] The threshold setting section 7 sets a threshold V TH for determining the presence or absence of a short circuit defect. The threshold V TH may be a voltage between the voltage of the DC link capacitor detected when the DC link capacitor 2 is in the normal state and the voltage of the DC link capacitor detected when the main circuit of the converter device has a short-circuit defect. Consequently, V th on the magnitude of the detected voltage of the converter 1 away. The threshold value setting section 7 can be configured to set the threshold value V TH based on a signal from the outside. By overwriting the threshold value, there is the advantage that defect detection adapted to the conditions of use becomes possible.

[0019] The short circuit defect detection section 8 determines that a short-circuit defect has occurred in the converter device when the voltage of the DC link capacitor 2 immediately after disconnection of the power source 10 and the converter 1 upon an instruction from the shift operation section 5 through the shift section 4 at most the threshold V TH amounts to. The short-circuit defect detecting section 8 can also be configured to notify the occurrence of an abnormality by a lamp or an alarm signal or the like when a short-circuit defect has been detected. Thereby, an operator can recognize that a short-circuit defect has occurred and prevent the power supply of the converter device from being turned on again, so that secondary damage caused by the turning on of the power supply again can be prevented in advance.

[0020] On the output side of the converter 1 a snubber circuit 9 can also be formed. By forming the snubber circuit 9, the transient high voltage generated at the time of breaking the switching portion 4 can be absorbed.

[0021] Next, the method of detecting a short-circuit defect using a converter device according to an embodiment will be explained. figure 2 is a flowchart for explaining the sequence of short-circuit defect detection by the short-circuit defect detection method of the converter device according to an embodiment. First, the shift operation portion 5 the shift section in step S101 4 beginning to close, causing the converter 1 and the power source 10 get connected. As a result, one of the power source 10 AC voltage supplied to the converter 1 is converted into a DC voltage and output to the DC link capacitor 2 .

[0022] Next, in step S102, the DC link capacitor 2 is charged and the motor drive device becomes operable.

[0023] Then the shift operation section monitors 5 in step S103, whether an abnormality has not occurred in the motor drive device including the converter device and the inverter device connected to the converter device. When the shift operation section 5 detects an anomaly, it issues a command to the switching section 4 off to put it in the off state.

[0024] Next comes the switching section 4 in step S104 by the command from the shift operation section 5 into the off state and become the power source 10 and the converter 1 separately. When they are separated, the voltage detection section detects 3 the voltage V DC of the DC link capacitor 2 immediately after disconnection of the power source 10 from the converter 1 . The power source monitoring section 6 notifies the short-circuit defect detecting section 8 that the switching section 4has entered the OFF state, and the short-circuit defect detecting section 8 obtains the result of detection of the voltage V immediately after receiving this notification DC of the DC link capacitor 2 from the voltage detection section 3.

[0025] Then the short-circuit defect detection section determines 8 in step S105 whether the voltage V DC of the DC link capacitor 2 is less than the threshold value V TH is or not. figure 3 is a graph showing the change with time in the voltage of the DC link capacitor when the main circuit of the converter device is in the normal state. It is assumed that the shift operation section 5 at the time t 1 detects any abnormality in the motor drive device and the shift section 4 controls so that this enters the off state, so that the power source 10 from the converter 1 is separated. For the main circuit of the converter device in the normal state, it is assumed that the motor driving device is running until time t 1 worked normally and the voltage V DC of the DC link capacitor 2 V 1 fraud. At the time t 1 becomes the power source 10 from the converter 1 disconnected and a discharge from the DC link capacitor 2 started, and takes the voltage V DC slowly off. At the time t 2 right after time t 1 , to which the switching portion 4 has come into the off state, is in the DC link capacitor 2 electric charge is still stored and the voltage of the DC link capacitor changes 2 generally for a few seconds hardly. When the short-circuit defect detection section 8 at time t 2 the value of the voltage V DC from the voltage detection section 3 obtained, the voltage V DC at this time t 2 a value slightly less than V 1 , but greater than the threshold V TH is. Consequently, it is determined that the voltage V DC of the DC link capacitor 2 at least the threshold V TH is , and the short-circuit defect detecting section 8 determines in step S106 that the abnormality that has previously occurred is not due to a short-circuit defect of the main circuit of the converter device 101 caused and at least the main circuit is in the normal state.

[0026] Next, the case where a short-circuit defect occurs in the main circuit of the converter device will be explained. figure 4 shows the change with time of the voltage of the DC link capacitor when the main circuit of the converter device has a short-circuit defect. It is assumed that the motor drive device is running until time t 0 worked normally and the voltage V DC of the DC link capacitor 2 as during the normal state V 1 fraud. If at the time t 0 short-circuit defect has occurred in the main circuit of the converter device 101, the both ends of the DC link capacitor 2 are connected with a low impedance, the electric charge in the DC link capacitor 2 suddenly decreases, and the voltage V decreases DC of the DC link capacitor 2 abruptly. As in figure 4, it is assumed here that V DC after the short-circuit defect down to V 3 has decreased. Here it is assumed that v 3 is almost 0 [V]. It is assumed that the shift operation section 5 thereafter at time t 1 detects any abnormality in the motor drive device and the shift section 4 controls so that this enters the off state, so that the power source 10 from the converter 1 is separated. If the current source 10 from the converter 1 has been disconnected and the short-circuit defect detecting section 8 at time t 2the value of the voltage V DC obtained, the voltage at that time is the voltage V 3 equal to and less than the threshold V TH . Consequently, it is determined that the voltage V DC of the DC link capacitor 2 lower than the threshold V TH , and the short-circuit defect detecting section 8 determines in step S107 that the abnormality that has occurred previously is an abnormality caused by a short-circuit defect of the main circuit of the converter device 101 is caused. In this way, in the short-circuit detection method according to the present embodiment, the fact that the voltage of the DC link capacitor suddenly decreases immediately after the power source is cut off and reaches a certain threshold at most determines that the main circuit of the traveling device becomes a short-circuit defect has occurred.

[0027] In the above explanation, the example of a case where the short-circuit defect occurred in the DC link capacitor of the main circuit of the converter device was discussed, but even in the event of a short-circuit defect occurring in the converter or the snubber circuit, the short-circuit defect is possible detect the same way.

[0028] With the converter device and the method for detecting a short-circuit defect in the converter device according to the embodiment of the present disclosure, the existence or non-existence of an abnormality in the main circuit of the converter device can be detected with a simple configuration.

Claims

[1] Converter device comprising: a converter (1) that converts an alternating current voltage supplied by a power source into a direct current voltage and outputs it; a DC link capacitor (2) connected to the output side of the converter; a voltage detection section (3) that detects the voltage of the DC link capacitor; a switching section (4) that connects or disconnects the power source and the converter; a switching actuation section (5) which monitors irregularities of a motor drive device which includes the converter device and an inverter device connected to the converter device and transmits instructions to the switching section; a power source monitoring section (6) that detects the voltage introduced into the converter and monitors the state of the connection between the power source and the converter; a threshold setting section (7) which sets a threshold for determining whether or not a short-circuit defect exists; and a short-circuit defect detection section (8) which determines that a short-circuit defect has occurred if the voltage of the DC link capacitor immediately after the power source is disconnected from the converter by the switching section is at most the threshold value. [2] Converter device according to claim 1, wherein the short-circuit defect detection section (8) reports that an irregularity has occurred in the main circuit of the converter device when it has detected a short-circuit defect. [3] Converter device according to claim 1 or 2, wherein the threshold setting section (7) can override the threshold based on an externally input signal. [4] Method for detecting a short circuit in a converter device which a converter (1) that converts an alternating current voltage supplied by a power source into a direct current voltage and outputs it; a DC link capacitor (2) connected to the DC output side of the converter; a voltage detection section (3) that detects the voltage of the DC link capacitor; a switching section (4) that controls the supply of the alternating current voltage from the power source to the converter; and a switching actuation section (5) which monitors irregularities of a motor drive device which includes the converter device and an inverter device connected to the converter device and transmits instructions to the switching section, wherein the switching actuation section (5) detects an irregularity and controls the switching section so that it enters the off state, thereby disconnecting the power source from the converter, the voltage of the DC link capacitor is detected directly after disconnecting the power source from the converter, and A short-circuit defect is determined to have occurred in a main circuit of the converter device if the detected voltage of the DC link capacitor is at most a threshold value. [5] Method for detecting a short-circuit defect in a converter device according to claim 4, wherein the short-circuit defect detection section (8) further reports that an irregularity has occurred when it has detected a short-circuit defect. [6] Method for detecting a short-circuit defect in a converter device according to claim 4 or 5, wherein the threshold setting section (7) further overrides the threshold based on an externally input signal.

Images