JP2004120930A - Fault detection device of power conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fault detection device of a power conversion element of high reliability that is less susceptible to the strain and cut of a power supply voltage. <P>SOLUTION: The fault detection device is used in a private power generation system that controls power by using a plurality of power conversion elements connected in series and a motor drive system, and detects the fault of the power conversion element by connecting a resistor and an operation detection circuit to the power conversion element. A voltage correction circuit, which corrects the operation state of the element from the voltage waveform of the power conversion element corresponding to the magnitude and the frequency of the power voltage, and a frequency correction circuit are arranged to detect the failure of the power conversion circuit, and a malfunction due to the strain and cut of the voltage is prevented, thus surely grasping the situation of the fault of the power conversion element relative to the change of the power supply voltage and the change of the frequency. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a failure detection device for a power conversion element that controls power used in a private power generation system or a motor drive system.
[0002]
[Prior art]
2. Description of the Related Art In a power generation system, a motor drive system, and the like, a required rated voltage is secured and used by connecting power conversion elements having a low rated voltage in series in multiple stages. A conventional failure detection device (see Japanese Patent Publication No. 59-4942) in which power conversion elements are connected in series in multiple stages will be described with reference to FIG.
[0003]
5, are connected thyristor elements _{1 1} as a power conversion device, 1 2 _... a multistage, the SCR _{1 1,} 1 2 _... operation state of, each thyristor element _{1 1,} 1 2 _... ends of resistance _{2 1} and the light-emitting element _{3 1,} resistor _{2 2} and the light-emitting element _{3 2,} ... are connected in parallel, respectively, the light-emitting elements _{3 1,} 3 2 _... each optical fiber _{4 1} light emitted in, 4 2 _... a Are transmitted to the light receiving elements 5 ₁ , 5 _2, ..., And the failure determination circuit 6 determines the failure of the thyristor element based on the signal.
[0004]
As described above, when the thyristor elements are connected in series in multiple stages and used, if all of the series elements do not perform the same operation, the voltage shared by each element is lost. For example, a short-circuit failure of one element may cause an overvoltage of another element and increase the accident, so that it is necessary to constantly monitor the operation status of each element.
[0005]
Hereinafter, a conventional thyristor element failure detection method will be described with reference to the failure detection device of FIG.
If SCR 1 ₁ is ON, but the divided voltage across the thyristor element is not generated, the thyristor element 1 ₁ in the case of OFF, compared supply voltage voltage divided to the thyristor number of stages is applied Is done. That is, no current flows to the light emitting element 3 ₁ when thyristor element 1 ₁ is ON, but the signal is not transmitted, since the thyristor element 1 ₁ is divided voltage appears across the thyristor element in the state of OFF , current flows to the light-emitting element 3 _1, transmitted to the next-stage light receiving element 5 ₁ its signal via an optical fiber 4 _1. Similarly, the operation of each thyristor element 1 ₂ ... Is detected by the same operation.
[0006]
As described above, the ON / OFF signals of all the thyristor elements are collected in the failure determination circuit 6. In the failure determination circuit 6, if all the elements are operating at the same timing, the thyristor elements are normal and operate in reverse. If there is a different thyristor element, the thyristor is in an abnormal state, and it is determined that the thyristor element has failed.
[0007]
[Problems to be solved by the invention]
As described above, the conventional failure detection device has a circuit configuration in which the ON / OFF state of the power conversion element is simply transmitted by light to thereby determine whether or not the power conversion element is abnormal. Since the detection of the ON / OFF state of the power conversion element becomes unstable due to the occurrence of the distortion or cut of the power supply voltage, there are many malfunctions and there is a problem in reliability. Also, if some of the power conversion elements in the multi-stage are short-circuited and fail, if the power is not noticed due to poor detection accuracy, the shared voltage of the other power conversion elements will increase and the power conversion elements will become overvoltage, It was feared that even the power conversion element would break down and the damage would increase.
[0008]
Furthermore, in order to confirm the malfunction of the failure detection, the operation of the power converter must be stopped and the characteristics of each element must be individually confirmed, which is inefficient. In addition, there is a case where stopping the power converter itself is not allowed in the system, which is a problem.
[0009]
The present invention (corresponding to claims 1 to 3) has been made to solve the above problems, and an object of the present invention is to provide a highly reliable power conversion element failure detection device that is not affected by power supply voltage distortion or cutout. Is to provide.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a failure detection device for a power conversion element according to claim 1 of the present invention is applied to a private power generation system or a motor drive system that controls power using a plurality of power conversion elements connected in series. In the failure detection device used for detecting a failure of the power conversion element by connecting a resistor and an operation detection circuit to each of the power conversion elements, an operation state of the power conversion element is determined based on a voltage waveform of the power conversion element. A voltage correction circuit and a frequency correction circuit for correcting according to the magnitude and frequency are provided, and a failure of the power conversion element is detected.
[0011]
According to a second aspect of the present invention, in the failure detection device for a power conversion element according to the first aspect, all operations of the plurality of power conversion elements connected in series are constantly monitored, and power conversion having different operations is performed therein. When an element is detected, the detected operation is further corrected according to the magnitude and frequency of the power supply voltage, and then a failure is determined.
[0012]
According to a third aspect of the present invention, in the failure detection device for a power conversion element according to the first or second aspect, a main shaft drive power generation system of a ship is used instead of the private power generation system or the motor drive system, and Voltage and frequency correction for two types of waveforms, a voltage waveform on the converter side that generates power and a voltage waveform on the inverter side that classifies power to the motor, which is a load, according to the magnitude and frequency of the voltage A selection circuit is provided to detect a failure of the power conversion element.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a failure detection device according to a first embodiment (corresponding to claims 1 and 2) of the present invention. The configuration different from the conventional failure detection device of FIG. And the frequency correction circuit 8, and then connecting the light emitting element 3, the failure determination circuit 6 is further provided with a voltage / frequency correction circuit 9, the power supply voltage detection circuit 10 and the power supply frequency detection circuit 11 , And the other configurations are the same. Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted.
[0014]
Since the present embodiment is configured as described above, the operating state of the thyristor element 1 is transmitted to the light emitting element 3 via the resistor 2 and the voltage correction circuit 7, and further via the frequency correction circuit 8. The power supply voltage detection circuit 10 detects the voltage value of the power supply, transmits the signal to the voltage correction circuit 7, and changes the threshold value for converting the operation state of the thyristor into an ON / OFF signal according to the power supply voltage. This operation is shown in FIG.
[0015]
FIG. 2 is a diagram for explaining the correction by the power supply voltage in the failure detection device of FIG. 1. In converting the voltage generated at both ends of the thyristor element 1 into the ON / OFF state of the element, the correction by the power supply voltage is performed. The method is shown.
[0016]
As shown in the figure, in order to convert the thyristor element into an ON / OFF signal using a voltage generated at both ends of the thyristor element, a constant voltage threshold V1 is determined and the conversion is performed. When the power supply voltage is large, the state of the element can be detected with a delay of t1 time from the actual waveform. Conversely, when the power supply voltage is low, the element is detected with a time delay t2 larger than the actual waveform when converted at the same threshold V1. Is detected. When the power supply voltage is low, the slope of the waveform of the power supply voltage crossing the threshold value V1 becomes gentle, so that the time delay t2 tends to be very unstable, resulting in malfunction of failure detection. Further, if the threshold value is lowered from the beginning, noise is detected, which causes a malfunction, which is a problem.
[0017]
Therefore, in the present embodiment, when the power supply voltage is low, the threshold value V2 is similarly decreased, and the slope of the waveform that intersects the threshold value is increased to increase the stability of the ON / OFF state detection of the element. It is intended to increase.
[0018]
In the voltage correction circuit 7, the thyristor ON / OFF signal whose threshold value has been corrected is transmitted to the frequency correction circuit 8, but the power supply frequency detection circuit 11 detects the frequency of the power supply and converts the signal to a frequency correction circuit. 8 to change the thyristor ON / OFF signal confirmation time according to the frequency. This operation is shown in FIG.
[0019]
FIG. 3 is a diagram for explaining correction by the power supply frequency in the failure detection device of FIG. 1, and shows a correction method by the power supply frequency in order to further improve the accuracy of the ON / OFF state of the thyristor element.
[0020]
As shown in the figure, if the waveform has a notch t4, the ON / OFF state of the element will cause erroneous reading regardless of the threshold value described above. If such a cut occurs, the next-stage failure judgment circuit 6 malfunctions. Therefore, by calculating backward from the power supply frequency and having a cut confirmation time period within a half cycle time, it is possible to improve the accuracy of failure detection. Can be.
If this confirmation time is excessively taken, each element will be damaged instead, and it is important to determine an optimal confirmation time limit according to the frequency.
[0021]
The signal corrected by the voltage correction circuit 7 and the frequency correction circuit 8 is transmitted from the light emitting element 3 to the next light receiving element 5 via the optical fiber 4, and the thyristor element having a different operation in the failure determination circuit 6 is used. If there is, it is determined that a failure has occurred. However, in order to further improve the accuracy, the voltage / frequency correction circuit 9 corrects the voltage and finally determines that the failure has occurred.
[0022]
By the way, since the ON / OFF signal of each thyristor element of the multi-stage configuration slightly shifts depending on the voltage and the frequency, the failure determination circuit 6 sometimes makes an erroneous determination. Thus, the voltage / frequency correction circuit 9 is provided for the purpose of taking in the power supply voltage and the power supply frequency detected by the power supply voltage detection circuit 10 and the power supply frequency detection circuit 11 and correcting the determination based on the above-described variation, and as described above. The malfunction can be prevented by checking the optimal time limit according to the voltage and the frequency.
[0023]
As described above, according to the present embodiment, by performing the correction according to the magnitude and frequency of the power supply voltage, it is possible to accurately cope with the distortion of the power supply voltage and the cut-off waveform. That is, the failure of the element can be determined with high accuracy at an optimum time limit.
[0024]
Although the above description has been made with reference to the example of the thyristor element, the present embodiment can be applied not only to the thyristor element but also to any power conversion element, and the same effect can be obtained.
[0025]
FIG. 4 is a configuration diagram of a main shaft drive power generation system for a marine vessel according to a second embodiment (corresponding to claim 3) of the present invention.
As shown in the figure, the present embodiment is a case where the present invention is applied to a main shaft drive power generation system for ships other than a private power generation system and a motor drive system, and a main engine 20 rotates a shaft generator 21 and a propeller 22. The electric power generated by the rotation of the shaft generator 21 is supplied to the inboard bus 25 via the converter element 23 and the inverter element 24.
[0026]
The converter / inverter is connected with a converter element failure detection device 26 and an inverter element failure detection device 27, respectively. The voltage / frequency selection circuit 28 further includes a converter element failure detection device 26 and an inverter element Is given to the failure detection device 27. Further, the failure detection device 26 for the converter element and the failure detection device 27 for the inverter element are the same as the failure detection device of the first embodiment of FIG.
[0027]
The voltage / frequency selection circuit 28 has the following functions. That is, since the divided voltage of the thyristor is affected by both the converter and the inverter, each fault detection device must be able to cope with both affected waveforms. In other words, since the voltage and frequency of the shaft generator 21 on the converter side and the voltage and frequency of the bus 25 on the inverter side are affected, the accuracy of the failure detection device can be improved in response to the voltage distortion or cut. The voltage / frequency selection circuit 28 is a circuit for selecting which of the power supply voltage and frequency of the converter and the inverter should correct the failure detection. As to which side of the converter / inverter is selected, the accuracy of fault detection can be enhanced by using the low voltage side as the reference voltage and the low frequency side as the correction reference. That is, as shown in FIG. 2, the threshold may be lowered as the voltage becomes lower. Further, as for the frequency, as shown in FIG. 3, as the frequency becomes lower, it is possible to prevent a malfunction by increasing the confirmation time.
[0028]
The power conversion element failure detection device of the present embodiment has the same effect as that of the first embodiment of FIG. 1 even when applied to a main shaft drive power generation system for a ship that performs power conversion between a converter and an inverter a plurality of times. Obtainable.
[0029]
In addition, the failure detection device for a power conversion device according to the present invention can accurately monitor a failure of a power supply voltage or a frequency in a private power generation system, a motor drive system, or a main shaft drive power generation system of a ship. The present invention exerts a great effect on high reliability and cost reduction of the power converter.
[0030]
【The invention's effect】
As described above, according to the present invention (corresponding to claims 1 to 3), the failure detection of the power conversion device does not malfunction due to the voltage distortion waveform or cut-off, and does not change the power supply voltage or change the frequency. Therefore, since the failure state of the power conversion element can be reliably grasped, it is possible to accurately find the abnormal power conversion element before a large accident due to the expansion of the failure occurs. In addition, since maintenance for stopping the power conversion device for the purpose of coping with malfunction of the failure detection device for the power conversion element is not required, maintenance costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a failure detection device according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a correction operation using a power supply voltage in FIG. 1;
FIG. 3 is a diagram for explaining a correction operation based on a power supply frequency in FIG. 1;
FIG. 4 is a configuration diagram of a failure detection device according to a second embodiment of the present invention.
FIG. 5 is a configuration diagram of a conventional failure detection device.
[Explanation of symbols]
1,1 _1, 1 2 _... SCR, 2,2 _1, 2 2 _... resistors, 3,3 _1, 3 2 _... light-emitting element, 4,4 _1, 4 2 _... optical fiber, _5,5 1, _{5 2} ... Light receiving element, 6: failure determination circuit, 7: voltage correction circuit, 8: frequency correction circuit, 9: voltage / frequency correction circuit, 10: power supply voltage detection circuit, 11: power supply frequency detection circuit, 20: main engine, 21 ... Shaft generator, 22: Propeller, 23: Converter element, 24: Inverter element, 25: Inboard bus, 26: Converter element failure detection device, 27: Inverter element failure detection device, 28: Voltage / frequency Selection circuit.

Claims (3)

Used in a private power generation system or a motor drive system that controls power using a plurality of power conversion elements connected in series, a failure of the power conversion element by connecting a resistor and an operation detection circuit to each of the power conversion elements. A voltage correction circuit and a frequency correction circuit for correcting the operation state of each power conversion element according to the magnitude and frequency of the power supply voltage from the voltage waveform of each power conversion element, and detecting a failure of the power conversion element. A failure detection device for a power conversion element, characterized by detecting a failure. The failure detection device for a power conversion element according to claim 1, wherein all operations of the plurality of power conversion elements connected in series are constantly monitored, and if a power conversion element having a different operation is detected therein, A failure detecting device for a power conversion element, wherein the detected operation is corrected according to the magnitude and frequency of a power supply voltage and then determined as a failure. 3. The failure detecting device for a power conversion element according to claim 1, wherein a main shaft drive power generation system of a ship is used instead of the private power generation system or the motor drive system, and a voltage on a converter side generating power from the power generator. A voltage / frequency selection circuit for correcting two types of waveforms, i.e., a waveform and a voltage waveform on an inverter side for classifying power to a motor as a load, according to the magnitude and frequency of the voltage; An apparatus for detecting a failure of a power conversion element, which detects a failure of the element.

Images