JP2014011908A - Power converter and detection method for open-circuit failure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting a failure of a switching element of a power converter for supplying electric power to each phase of an AC motor/generator and further identifying a failed point when the switching element has an open-circuit failure.SOLUTION: The present invention gives a firing command to IGBTs Q1-Q6 one by one while AC motor/generator 10 is rotating, detects the presence/absence of a current flow with current detectors 22a, 22b, 22c during firing command application and, in the absence of a current flow, the IGBT which has applied a firing command is determined to have an open-circuit failure.

Description

  The present invention relates to detection of an open fault of a power converter, and more particularly to an open fault detection method for detecting a fault of a switching element used in a power converter and specifying a fault location.

  Conventionally, several fault detection methods for switching elements used in power converters have been proposed. Switching element failure modes can be broadly classified into two types: short-circuit faults and open-circuit faults. Patent Document 1 proposes a method of determining the detection of switching element open-circuit faults from the peak value of the current flowing through the power converter. ing. Patent Document 2 proposes a method for detecting a short-circuit fault in a switching element and further identifying a switching element in which a short-circuit fault has occurred.

JP 2010-246182 A JP 2009-278791 A

  In Patent Document 1, since a multi-phase power converter uses a plurality of switching elements, failure detection is not possible until a faulty one is specified from among the plurality of switching elements.

  Further, in Patent Document 2, only when a switching element in a power converter has a short-circuit failure, it is a means that can identify a failure from a plurality of switching elements, and when a switching element has an open failure, the failed element is specified. There was room to devise a specific method for cases.

  In view of the above, an object of the present invention is to provide a method for detecting a failure of a switching element when a switching element of a power converter has an open failure, and further specifying a failure location.

  Supplying electric power to each phase of the AC motor / generator, switching elements connected in series in two upper and lower stages and controlled to be individually ignited, and current flowing through each phase of the AC motor / generator A power converter having a current detector for detecting rotation for determining whether the rotational speed of the AC motor / generator is within a predetermined range when the AC motor / generator is rotated by an external force; Speed determination means, and a current value determination means for giving an ignition command to the switching element when the rotation speed is in a predetermined range and determining whether the detection value of the current detector has reached a predetermined threshold value It is characterized by that.

  Also, power is supplied to each phase of the AC motor / generator, and the switching elements are connected in series in the upper and lower stages and controlled to be individually ignited, and flow through each phase of the AC motor / generator. A power converter having a current detector for detecting a current, wherein when the AC motor / generator is rotated by an external force, an ignition command is given to the switching element of the power converter, and the current detection When the detected value of the converter reaches a predetermined threshold value, the switching failure of the power converter is determined to be detected by the switching element.

  According to the open fault detection method for the AC motor / generator control power converter using the present invention, the open fault of the switching element is detected in a state where the AC motor / generator is freely rotated after the failure of the power converter, This has the effect of specifying and determining whether or not the power converter can be restarted and identifying the cause of failure early.

It is the whole structure of an AC motor / generator control device. This is a short-circuit current waveform that flows when an ignition command is applied to the IGBT. It is the figure which showed the flow of the open failure detection process.

  In the present invention, a rotating machine that functions as an AC motor or a generator is referred to as an AC motor / generator. FIG. 1 shows an overall configuration diagram of an AC motor / generator control device including an AC motor / generator, a power converter, and peripheral devices thereof including a failure detection device according to the present embodiment. In this apparatus, the AC motor / generator 10, the power converter 20 connected to the AC motor / generator 10, the battery / capacitor 30 for supplying power to the power converter 20, and the voltage of the battery / capacitor 30 are boosted. And a control device 50 for controlling the power converter 20 and the DC conversion circuit 40.

  The power converter 20 is provided with current detectors 22a, 22b, and 22c that detect currents flowing in the respective phases of the AC motor / generator 10, and the AC motor / generator 10 has a speed detector 60 that detects a rotational speed. The signals of the current detectors 22a, 22b, 22c and the speed detector 60 are input to the control device 50.

The power converter 20 has an IGBT (Insulated Gate) which is a switching element capable of controlling a large current.
Bipolar transistors) Q1 to Q6 are connected in series up and down, and diodes D1 to D6 are connected in parallel with the IGBT, and are configured as arm modules 21a to 21f for each phase.

  The controller 50 gives ignition commands to the IGBTs Q1 to Q6, operates the power converter, and operates the AC motor / generator 10.

  The DC conversion circuit 40 is connected to the power converter 20 via the smoothing capacitor 23. The DC conversion circuit 40 monitors the voltage value between the terminals of the smoothing capacitor 23 and supplies power to the power converter 20 or charges the battery / capacitor 30 in accordance with the operation of the power converter 20.

  If the ignition command is given only to IGBT Q1 when the AC motor / generator 10 is rotating, a circuit through the IGBT Q1 and the diodes D2, D3 is formed by the induced voltage generated by the rotation of the AC motor / generator. Flows. FIG. 2 shows current signals detected by the current detectors 22a, 22b, and 22c when the AC motor / generator 10 is turned on and the IGBT Q1 is ignited.

  As described above, when the ignition command is given to any of the IGBTs Q1 to Q6 while the AC motor / generator 10 is rotating, a circuit is formed through the IGBT and the diode that gave the ignition command, and the AC motor / Current flows using the induced voltage generated from the generator as a power source.

  Here, when any of the IGBTs Q1 to Q6 has an open failure, a circuit is not formed because the IGBT is open even if the ignition command is given to the IGBT in which the AC motor / generator 10 has failed in the rotation state. No current flows.

  Under the use conditions in which the AC motor / generator 10 is rotated by an external force using the above phenomenon, when the power converter 20 is protected and the operation of the power converter 20 is stopped, the AC motor / generator When 10 is rotating due to external force, give an ignition command to IGBTs Q1-Q6 one by one, detect the current with current detectors 22a, 22b, 22c, and if the absolute value of the current value is above a certain threshold For example, it is determined that the IGBT to which the ignition command is given has not failed and is normal, and if the absolute value of the current value is smaller than a certain threshold value, the IGBT to which the ignition command has been given is determined to have an open failure.

  When an open failure detection point is specified by the above method, when an ignition command is given to a normal IGBT, the IGBT is in an ignition state and a short-circuit current flows, so that a brake torque is applied to the AC motor / generator 10. There is a possibility that the rotation may be hindered, and a short circuit current may cause damage to the power converter 20 and cause a secondary disaster. Therefore, as a countermeasure against this, an open failure detection process is limited.

  First, since the magnitude of the short-circuit current is proportional to the rotational speed of the AC motor / generator 10, the short-circuit current that can be detected by the current detectors 22a, 22b, and 22c so that an excessive short-circuit current does not flow. In order to flow, the restriction that the open failure detection is performed when the speed value of the speed detector 60 falls within a certain speed range is provided. The rotational speed range is determined based on the result of measuring the relationship between the rotational speed of the AC motor / generator 10 and the magnitude of the short-circuit current flowing in advance.

  The second is to limit the firing command application period of IGBTs Q1 to Q6 so as not to form a short circuit for a long time. Since the short-circuit current flows periodically, it is possible to determine whether the current has flowed by detecting a period of one short-circuit current. Since the cycle of the short-circuit current depends on the number of poles and rotation speed of the AC motor / generator 10, the ignition command application period of the IGBTs Q1 to Q6 is limited with respect to the number of poles of the AC motor / generator to be used and the above rotation speed. The optimum value is determined from the speed range of the AC motor / generator 10 provided.

  FIG. 3 shows the flow of the open fault detection process. In the failure detection process, when protection is generated in the power converter 20 and the operation of the power converter 20 is stopped, first, in step S10, the rotational speed of the AC motor / generator 10 detected by the speed detector 60 is within a predetermined range. It is determined whether or not. If the rotational speed is outside the predetermined range, the state of S10 is maintained until the rotational speed changes to the predetermined range. If the rotational speed is within a predetermined range, the process proceeds to step S11, and an ignition command is given to the IGBT Q1 for a certain period. While applying the ignition command to the IGBT, a short circuit failure is determined in step S12. In step S12, if the absolute value of the current detected by the current detectors 22a, 22b, and 22c is greater than or equal to the threshold value, it is determined that the IGBT Q1 to which the ignition command is given is normal, and if the absolute value of the current is smaller than the threshold value, It is determined that the IGBT Q1 to which the arc command is given has an open failure.

In FIG. 3, IGBT Q2 to Q6 perform the same process as IGBT Q1 to detect an open failure, and when the failure determination of IGBTs Q1 to Q6 is performed, the process ends. Even if the speed of the AC motor / generator 10 fluctuates in the middle, a process for determining whether the rotational speed of the AC motor / generator 10 is within a predetermined range before applying the ignition command of each IGBT is large. Short circuit current can be prevented from flowing.

According to the AC motor / generator control device according to the present embodiment, it is possible to detect an open failure of an IGBT used in a power converter and to identify an IGBT that has an open failure.

10 AC motor / generator 20 Power converter
21a, 21b, 21c, 21d, 21e, 21f Arm module
22a, 22b, 22c Current detector 23 Smoothing capacitor 30 Battery / capacitor 40 DC conversion circuit 50 Control device 60 Speed detector

Claims (4)

Supplying electric power to each phase of the AC motor / generator, switching elements connected in series in two upper and lower stages and controlled to be individually ignited, and current flowing through each phase of the AC motor / generator A power converter having a current detector for detecting rotation for determining whether the rotational speed of the AC motor / generator is within a predetermined range when the AC motor / generator is rotated by an external force; Speed determination means, and a current value determination means for giving an ignition command to the switching element when the rotation speed is in a predetermined range and determining whether the detection value of the current detector has reached a predetermined threshold value A power converter characterized by that. Supplying electric power to each phase of the AC motor / generator, switching elements connected in series in two upper and lower stages and controlled to be individually ignited, and current flowing through each phase of the AC motor / generator In the power converter having a current detector for detecting, when the AC motor / generator is rotated by an external force, an ignition command is given to the switching element of the power converter, and the current detector An open fault detection method for a power converter, wherein when the detected value reaches a predetermined threshold value, the switching element is determined to be an open fault. 3. The open failure detection method for an AC motor / generator control power converter according to claim 2, wherein each of the switching elements used in the power converter is individually given an ignition command to cause an open failure. An open fault detection method for a power converter characterized by specifying a switching element. 3. The open fault detection method for an AC motor / generator control power converter according to claim 2, wherein a process for determining that the rotational speed of the AC motor / generator is within a predetermined range; An open fault detection method for a power converter, characterized in that a limit is imposed on the ignition time of the power converter.

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