JP2008206321A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter that detects an abnormality of a branched main circuit including switching elements regardless of the presence or the absence of a fuse. <P>SOLUTION: A power converter supplies a desired output current to a load 3. The power converter includes at least one conversion arm 2X, which is composed by connecting branched main circuits, respectively including a plurality of switching elements Th1, Th2, and Th3, in parallel, each temperature detection means T1, T2, and T3 that directly or indirectly detects a temperature of each switching element Th1, Th2, and Th3, and a main circuit abnormality determination means 4 for detecting an abnormality of each branched main circuit respectively including the switching elements Th1, Th2, and Th3 while using a detected temperature of each element detected by each temperature detection means T1, T2, and T3 as input. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power converter, and more particularly, to a power converter having a conversion arm in which branch main circuits including a plurality of switching elements are connected in parallel.

In a power converter for outputting a large current, a plurality of switching elements may be connected in parallel. And when a switching element causes a short circuit failure, a fuse is also inserted in series with each switching element for the purpose of protecting the power conversion device. In such a power conversion device, for example, when a fuse deteriorates and becomes non-conductive, a current flows in a series circuit (hereinafter referred to as a branch main circuit) of a normal fuse and a switching element among switching elements connected in parallel. There is a problem of concentration. However, in a power converter that handles a large current, it is often difficult to detect the non-conducting abnormality by detecting the current of each branch main circuit. On the other hand, a proposal has been made to reliably protect the power conversion device by detecting the temperature of the fuse of each branch main circuit (see, for example, Patent Document 1).
JP 2004-248390 A (page 3-4, FIG. 1)

  In the branch main circuit in which a fuse is provided in series with each switching element, a non-conducting abnormality of the switching element can be detected, but the technique disclosed in Patent Document 1 is formed with switching elements connected in parallel. There is a problem that it is difficult to detect a non-conducting abnormality of the switching element when only one fuse is provided in series with respect to the conversion arm, or when no fuse is provided in the arm.

  The present invention has been made in view of the above problems, and an object thereof is to provide a power conversion device capable of detecting an abnormality of a branch main circuit including a switching element regardless of the presence or absence of a fuse. .

  In order to achieve the above object, a power conversion device according to the present invention includes at least one branch main circuit including a plurality of switching elements connected in parallel in a power conversion device that supplies a desired output current to a load. A conversion arm; temperature detection means for directly or indirectly detecting the temperature of each of the switching elements; and a main circuit for detecting an abnormality of the branch main circuit with the detected temperature of each switching element by the temperature detection means as an input An abnormality determination means is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the power converter device which can detect the abnormality of the branch main circuit containing a switching element irrespective of the presence or absence of a fuse.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, the power converter concerning Example 1 of the present invention is explained with reference to FIG.1 and FIG.2. FIG. 1 is a circuit configuration diagram of a power conversion apparatus according to Embodiment 1 of the present invention. FIG. 1 shows an example in which a thyristor element is used as a switching element, and three of these are connected in parallel to form a three-phase thyristor rectifier circuit.

  The AC voltage supplied from the three-phase AC power source 1 is supplied to the positive conversion arms 2U, 2V, and 2W and the negative conversion arms 2X, 2Y, and 2Z that constitute the three-phase bridge. This three-phase bridge is a three-phase thyristor rectifier circuit, and its DC output is fed to the DC load facility 3.

  Each conversion arm uses a thyristor element as a switching element and is connected in parallel with each other. However, since all have the same circuit configuration, only the conversion arm 2X is shown with its internal configuration. . Each thyristor element is supplied with a gate pulse from a control circuit (not shown) to adjust the output current.

  The conversion arm 2X includes a parallel circuit of thyristor elements Th1, Th2, and Th3. Fuses F1, F2, and F3 are connected in series to each of the thyristor elements Th1, Th2, and Th3 to form three branch main circuits. The fuses F1, F2, and F3 may be combined into one conversion arm fuse, or may be omitted.

  Temperature detectors T1, T2, and T3 are attached to the thyristor elements Th1, Th2, and Th3, respectively, and these temperature detection signals are given to the main circuit abnormality determination circuit 4.

  FIG. 2 is a structural diagram showing a mounting state of the thyristor element Th1 of the conversion arm 2X. The thyristor element Th1 is mounted in close contact with the cooling fin Fin, and the cooling water flowing in from the inlet pipe P1 passes through the inside of the cooling fin Fin to perform heat exchange, and the cooling water after the heat exchange is supplied from the outlet pipe P2. It is configured to flow out. A temperature detector T1 is embedded in a portion where the thyristor element Th1 and the cooling fin Fin are joined. In addition, if the thyristor element Th1 in which the temperature detector T1 is embedded in the vicinity of the internal junction is used, a more accurate temperature detection becomes possible.

  Hereinafter, the internal configuration of the main circuit abnormality determination circuit 4 in FIG. 1 will be described.

  The temperature signals obtained from the temperature detectors T1, T2, and T3 are input to the comparison circuits CP1, CP2, and CP3, respectively, and are compared with the comparison reference REF provided in common. The outputs of the comparison circuits CP1, CP2, and CP3 are input to the abnormality determination circuits Fa1, Fa2, and Fa3, respectively. The abnormality determination circuits Fa1, Fa2, and Fa3 perform abnormality determination of the thyristor elements Th1, Th2, and Th3, respectively, based on the outputs of the comparison circuits CP1, CP2, and CP3, and give the determination results to the control processing circuit Ct.

  Next, the operation will be described. A case is assumed where, during operation of the three-phase thyristor rectifier circuit shown in FIG. 1, a disconnection of the fuse F1 of the conversion arm 2X or an abnormality occurs in the ignition circuit of the thyristor element Th1. Any failure causes no current to flow through the thyristor element Th1, and the temperature of the thyristor element Th1 decreases. Due to the abnormality of the series circuit including the thyristor element Th1 (hereinafter referred to as the abnormality of the Th1 branch main circuit), the currents of the sound thyristor elements Th2 and Th3 increase 1.5 times. Since the amount of heat generated by the semiconductor element is approximately proportional to the square of the current, the amount of heat generated by the thyristor elements Th2 and Th3 is approximately doubled. In this way, the abnormality determination circuits Fa1, Fa2 and the fact that the temperature of the thyristor element Th1 has decreased by a predetermined value or more than the comparison reference REF and the temperature of the thyristor elements Th2 and Th3 has increased by a predetermined value or more by the comparison reference REF. An abnormality of the thyristor element Th1 circuit can be detected by making a determination using Fa3 and calculating and analyzing the determination result using the control processing circuit Ct.

  Similarly, when an abnormality occurs in both the Th1 circuit and the Th2 circuit, the temperature of the thyristor elements Th1 and Th2 is lower than the comparison reference REF, and the temperature of the thyristor element Th3 is higher than the comparison reference REF. It is possible to detect both abnormalities in the circuit. In summary, the following branch main circuit abnormality can be detected corresponding to the determination results of the abnormality determination circuits Fa1, Fa2, and Fa3.

T1 <REF, T2 <REF, T3 <REF--Th1-Th3 branch main circuit normal T1 <REF, T2> REF, T3> REF--Th1 branch main circuit abnormality T1> REF, T2 <REF, T3> REF --- Th2 branch main circuit error T1> REF, T2> REF, T3 <REF --- Th3 branch main circuit error T1 <REF, T2 <REF, T3> REF --- Th1 & Th2 branch main circuit error T1> REF , T2 <REF, T3 <REF --- Th2 & Th3 branch main circuit error T1 <REF, T2> REF, T3 <REF --- Th3 & Th1 branch main circuit error In the above detection, tradeoff between detection delay and detection accuracy However, for example, by appropriately selecting the time constant for abnormality determination of the abnormality determination circuits Fa1, Fa2, and Fa3 from the protection coordination curve of the thyristor element, etc. This problem can be solved. Further, as the protection operation by the output signal of the control processing circuit Ct, it is conceivable to output only an alarm, stop the apparatus, or continue the operation by reducing the output according to the needs of the application system.

  By performing the above determination of the branch main circuit abnormality in the other conversion arms in the same manner, it is possible to determine the main circuit abnormality as the power conversion device and perform a protection operation based on the determination.

  FIG. 3 is a circuit configuration diagram of the power conversion apparatus according to the second embodiment of the present invention. In the second embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The second embodiment is different from the first embodiment in that the comparison reference REF in the main circuit abnormality determination circuit 4A is changed according to the value of the current command IREF.

  The thyristor elements Th1, Th2, and Th3 have their gate firing angles controlled in accordance with the current command IREF. Therefore, when the current command IREF is reduced, the energization period is shortened and the temperature of the thyristor element is lowered. Therefore, when the current command IREF is reduced, if the comparison reference REF is decreased approximately in proportion to the square of the current reference IREF, the thyristor circuit can be operated even in a region where the output of the power converter is smaller than the rated output. An abnormality can be detected, and the detection accuracy of the main circuit abnormality determination circuit 4A is improved.

  FIG. 4 is a circuit configuration diagram of the power conversion apparatus according to the third embodiment of the present invention. In the third embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The third embodiment differs from the first embodiment in that, in the main circuit abnormality determination circuit 4B, an average value calculation circuit ME is provided instead of the current reference IREF, and the average value calculation circuit ME is detected from the temperature detectors T1, T2, and T3. This is a point configured to calculate an average value of the obtained temperature signals.

  As in the third embodiment, it is possible to reduce the offset error by calculating the average value of the temperature detector output using the average value calculation circuit ME and using it as a comparison reference. Therefore, in the third embodiment, particularly when the number of thyristor elements connected in parallel is large and the increase in the current of the healthy circuit when one circuit is abnormal is small, an effective abnormality can be detected.

  FIG. 5 is a circuit configuration diagram of a power conversion apparatus according to Embodiment 4 of the present invention. In the fourth embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The difference between the fourth embodiment and the first embodiment is that, in the main circuit abnormality determination circuit 4C, the comparison circuit CP1A detects the temperature detected by the temperature detector T1, the temperature detected by the temperature detector T2, and the temperature detected by the temperature detector T1. The detection temperature of the detector T3 is compared, and the abnormality determination circuit Fa1A is configured to output a Th1 circuit abnormality based on the two comparison results. Similarly, the comparison circuits CP2A and CP3A also compare the detected temperatures of the temperature detectors T2 and T3 with the other two detection temperatures, respectively, and the abnormality determination circuits Fa2A and Fa3A receive these comparison results to determine whether the Th2 circuit is abnormal or the Th3 circuit. Each abnormality is output to the control processing circuit Ct.

  As in the fourth embodiment, it is possible to detect an abnormality with high accuracy by performing a relative comparison with the detector output of another parallel circuit.

  In this case, not only the circuit current does not flow at all due to the disconnection of the fuse F1 in the branch main circuit or the firing circuit abnormality of the thyristor Th1, but there is a difference in the flow characteristics between the parallel circuits due to the aging characteristic change of the thyristor Th1. Therefore, the present invention can also be applied to the detection of the unbalance of the shunt flow caused by this.

  FIG. 6 is a circuit configuration diagram of the power conversion device according to the fifth embodiment of the present invention. In each part of the fifth embodiment, the same parts as those in the circuit configuration diagram of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. The fifth embodiment differs from the first embodiment in that in the main circuit abnormality determination circuit 4D, the comparison circuit CP1 compares the detection temperature of the temperature detector T1 with the detection temperature of the temperature detector T2, and the abnormality determination circuit Fa1B. Is a configuration that outputs a Th1 or Th2 circuit abnormality based on the comparison result. Similarly, the comparison circuits CP2 and CP3 also compare the detected temperatures of the temperature detectors T2 and T3 with the detected temperatures of the temperature detectors T3 and T1B, respectively, and the abnormality determination circuits Fa2B and Fa3B receive these comparison results to determine whether the Th2 circuit is abnormal or The Th3 circuit abnormality, Th3 circuit abnormality or Th1 circuit abnormality is output to the control processing circuit Ct.

  As described above, according to the configuration in which the temperatures of two adjacent thyristor elements in the conversion arm are compared, simplified abnormality detection is possible under the condition that two or more circuits do not become abnormal at the same time. Therefore, in the case of a system configuration in which the apparatus is stopped when one circuit fails, the main circuit abnormality determination circuit can be simplified. In the above description, adjacent means that N (N is an integer) thyristor elements are compared with the second thyristor element, the second thyristor element, and the third thyristor element. The element means to compare with the first.

  FIG. 7 is a structural diagram illustrating a mounted state of the thyristor element Th1 of the conversion arm 2X of the power conversion apparatus according to the sixth embodiment of the present invention. Regarding the respective parts of the sixth embodiment, the same parts as those in the structural diagram showing the mounting state of the thyristor element Th1 of the conversion arm 2X of the power conversion device according to the first embodiment of the present invention shown in FIG. Is omitted. The difference between the sixth embodiment and the first embodiment is that the mounting position of the temperature detector T1 is set close to the outlet side of the semiconductor element cooling fin Fin, which is different from the position close to the thyristor element Th1.

  As shown in the sixth embodiment, the temperature of the thyristor element Th1 can be indirectly detected by detecting the temperature of the cooling water closest to the outlet side of the semiconductor element cooling fin Fin by the temperature detector T1.

  FIG. 8 is a structural diagram illustrating a mounted state of the thyristor element Th1 of the conversion arm 2X of the power conversion apparatus according to the seventh embodiment of the present invention. Regarding the respective parts of the seventh embodiment, the same parts as those of the structural diagram showing the mounting state of the thyristor element Th1 of the conversion arm 2X of the power conversion apparatus according to the first embodiment of the present invention shown in FIG. Is omitted. The difference between the seventh embodiment and the first embodiment is that the cooling method is air cooling, and the position where the temperature detector T1 is attached is close to the exit side of the semiconductor element wind cooling fin Fin1, which is different from the position close to the thyristor element Th1. Is a point.

  As shown in the seventh embodiment, the temperature of the thyristor element Th1 can be indirectly detected by detecting the temperature of the cooling air closest to the outlet side of the semiconductor element wind cooling fin Fin1 by the temperature detector T1.

The circuit block diagram of the power converter device which concerns on Example 1 of this invention. FIG. 2 is a structural diagram showing a mounting state of a thyristor element in Embodiment 1 of the present invention. The circuit block diagram of the power converter device which concerns on Example 2 of this invention. The circuit block diagram of the power converter device which concerns on Example 3 of this invention. The circuit block diagram of the power converter device which concerns on Example 4 of this invention. FIG. 5 is a circuit configuration diagram of a power conversion apparatus according to Embodiment 5 of the present invention. FIG. 9 is a structural diagram showing a mounted state of a thyristor element in Example 6 of the present invention. FIG. 9 is a structural diagram showing a mounting state of a thyristor element in Example 7 of the present invention.

Explanation of symbols

1 3-phase AC power supply 2U, 2V, 2W, 2X, 2Y, 2Z Conversion arm 3 DC load equipment 4, 4A, 4B, 4C, 4D Main circuit abnormality determination circuit Th1, Th2, Th3 Thyristor elements F1, F2, F3 Fuse T1 T2, T3 Temperature detectors CP1, CP2, CP3, CP1A, CP2A, CP3A Comparison circuits Fa1, Fa2, Fa3, Fa1A, Fa2A, Fa3A, Fa1B, Fa2B, Fa2C Fault determination circuit Ct Control processing circuit

Claims (11)

A power converter for supplying a desired output current to a load,
At least one conversion arm formed by connecting branch main circuits including a plurality of switching elements in parallel;
Temperature detecting means for directly or indirectly detecting the temperature of each of the switching elements;
A power converter comprising: main circuit abnormality determining means for determining abnormality of the branch main circuit by using the detected temperature of each switching element by the temperature detecting means as an input. The branch main circuit is:
The power conversion device according to claim 1, wherein a fuse is connected in series to each of the switching elements. The main circuit abnormality determination means includes
A plurality of comparison circuits for comparing the detection temperature of each of the switching elements and a comparison reference;
A plurality of circuit abnormality detection circuits each for determining whether or not the comparison result of each comparison circuit is an abnormal level;
The power conversion device according to claim 1, further comprising: a control processing circuit capable of performing a protection operation of the device based on a detection result of each of the circuit abnormality detection circuits.   The power conversion device according to claim 3, wherein the comparison reference is changed in accordance with an output current reference. The main circuit abnormality determination means includes
An average value calculation circuit for calculating an average value of the detected temperatures of the respective switching elements in the same conversion arm;
A plurality of comparison circuits for comparing each of the detected temperatures in the same conversion arm and the average value;
A plurality of circuit abnormality detection circuits each for determining whether or not the comparison result of each comparison circuit is an abnormal level;
The power conversion device according to claim 1, further comprising: a control processing circuit capable of performing a protection operation of the device based on a detection result of each of the circuit abnormality detection circuits. The main circuit abnormality determination means includes
A plurality of comparison circuits for comparing the detection temperature of each of the switching elements in the same conversion arm with the detection temperature of a switching element other than the switching element;
A plurality of circuit abnormality detection circuits each for determining whether or not the comparison result of each comparison circuit is an abnormal level;
The power conversion device according to claim 1, further comprising: a control processing circuit that performs a protection operation of the device based on a detection result of each circuit abnormality detection circuit. The main circuit abnormality determination means includes
A plurality of comparison circuits for comparing the detected temperature of each of the switching elements in the same conversion arm with the detected temperature of a switching element adjacent to the switching element;
A plurality of circuit abnormality detection circuits each for determining whether or not the comparison result of each comparison circuit is an abnormal level;
The power conversion device according to claim 1, further comprising: a control processing circuit capable of performing a protection operation of the device based on a detection result of each of the circuit abnormality detection circuits. The control processing circuit includes:
8. The power conversion according to claim 3, further comprising an arithmetic unit that can identify a branch main circuit in which an abnormality has occurred based on a detection result of the circuit abnormality detection circuit. 9. apparatus. The temperature detecting means includes
The power conversion device according to any one of claims 1 to 8, wherein a temperature detector is provided in the switching element or in close contact with the switching element. The temperature detecting means includes
The power converter according to any one of claims 1 to 8, wherein the power converter is provided by a temperature detector provided in a water-cooled pipe in the vicinity of a water-cooled cooling fin outlet of the switching element. The temperature detecting means includes
The power converter according to any one of claims 1 to 8, wherein a temperature detector is provided in the vicinity of the outlet of the air-cooling cooling fin of the switching element.

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