JP2009284762A - Countermeasure device against instantaneous voltage drop/power failure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress variations in a forcible arc-extinguishing time of a thyristor switch as much as possible without depending on the magnitude of a DC voltage of a DC power supply of an inverter. <P>SOLUTION: A countermeasure device against instantaneous voltage drop/power failure includes a thyristor switch 5 connected between an AC power supply 1 and a load 3 and an inverter 8 connected to the load 3 and the thyristor switch 5 via an injection transformer 6 and having a DC power supply 7. The countermeasure device forcibly arc-extinguishes the thyristor by using an inverter output voltage based on a forcible arc-extinguishing pulse command value if an instantaneous voltage drop occurs in the AC power supply 1. The countermeasure device includes a processing section 17 for generating the forcible arc-extinguishing pulse command value, and the processing section 17 performs control so that the forcible arc-extinguishing pulse command value is set again from the polarity of the electric current of the thyristor at the point in time after a pre-determined time elapses from the start of forcible arc-extinguishing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention, for example, when an instantaneous voltage drop occurs in an AC power supply such as a commercial power supply, the voltage drop of the AC power supply is compensated for by the AC output voltage of the inverter based on the DC voltage of the inverter DC power supply. Relates to the device.

  In recent years, with the widespread use of various control devices using CPUs, problems due to instantaneous voltage drop of AC power supplies such as commercial power supplies due to lightning strikes have become a problem. For this reason, in critical load facilities such as bank online, traffic control, computer control, industrial manufacturing equipment, and power supplies for measurement and control, the instantaneous voltage drop generated in the AC power supply is detected quickly, and the power supply voltage is applied to the load equipment. In order to supply power, an instantaneous voltage drop / power failure countermeasure device that compensates for the voltage drop of the AC power supply is installed.

  The present applicant has previously proposed various instantaneous voltage drop / power failure countermeasure devices that compensate for the voltage drop of the AC power supply when an instantaneous voltage drop occurs (see, for example, Patent Documents 1 to 3).

  These instantaneous voltage drop / power failure countermeasure devices include a thyristor switch connected between an AC power supply and a load, and an inverter having a DC power supply connected to the load and the thyristor switch via an injection transformer. When an instantaneous voltage drop occurs, the thyristor switch is forcibly extinguished and turned off, and the voltage drop of the AC power supply is compensated with the output voltage of the inverter based on the DC voltage of the DC power supply.

  In this type of instantaneous voltage drop / power failure countermeasure device, when an instantaneous voltage drop occurs in the AC power supply, the polarity of the load current is determined, and the thyristor switch is forcibly extinguished and turned off. However, when an instantaneous voltage drop occurs in the AC power supply, an erroneous determination of the polarity of the load current occurs, and the thyristor switch is not forcibly extinguished, and an overcurrent may flow through the inverter. As described above, when an overcurrent flows through the inverter due to an erroneous determination of the polarity of the load current, the overcurrent protection function is activated, the inverter is forcibly stopped, and voltage compensation cannot be performed (see Patent Document 1).

  Therefore, the instantaneous voltage drop countermeasure device disclosed in Patent Document 1 reliably prevents malfunction of the overcurrent protection function when an instantaneous voltage drop of the AC power supply occurs, and forcibly extinguishes the thyristor switch to compensate the voltage by the inverter. When an overcurrent flows through the inverter, the pause means for stopping the inverter is operated for a predetermined time, and after the operation of the pause means is stopped, the thyristor switch is forcibly extinguished. If overcurrent continues to flow through the inverter after that, the pause means operates again to execute forced extinction of the thyristor switch. This is repeated, the number of operations of the suspension means is counted, and if the inverter overcurrent disappears before the count value reaches a predetermined value, the overcurrent protection function does not malfunction by forcibly extinguishing the thyristor switch. Thus, voltage compensation by the inverter is reliably performed. In addition, when the count value of the number of operations of the suspension means reaches a predetermined value, the inverter is forcibly stopped so that the overcurrent protection function is normally operated.

  Also, in the instantaneous voltage drop countermeasure device, when an instantaneous voltage drop occurs in an AC power supply, the inverter is extinguished for a certain period determined by the pulse width of the forced extinguishing pulse of the thyristor switch regardless of the magnitude of the load current. The forced extinguishing output voltage of the inverter continues to be applied to the thyristor switch. Therefore, when the current flowing through the thyristor switch is small and the thyristor switch is turned off by applying voltage for a short time, the inverter is extinguished even after the thyristor switch is extinguished, and the voltage application of unnecessary forced extinguishing output is continued. The voltage is supplied to the load, and the load voltage increases (see Patent Documents 2 and 3).

  Therefore, in the instantaneous voltage drop countermeasure device disclosed in Patent Document 2, when an instantaneous voltage drop occurs in an AC power supply, a forced extinguishing output voltage based on an arc extinguishing drive of an inverter by a forced extinguishing pulse of a thyristor switch is applied. When the voltage at both ends of the thyristor switch is detected and the thyristor switch is turned off by the forced extinction based on the forced arc extinguishing output voltage and the voltage at both ends is generated, the pulse output from the inverter disappears. As a result, the application of the forced extinguishing output voltage of the inverter stops at the same time that the thyristor switch is forcibly extinguished, preventing an increase in load voltage due to the application of an unnecessary forced extinguishing output voltage after forced extinguishing. is doing.

  The instantaneous voltage drop countermeasure device disclosed in Patent Document 3 detects the current flowing through the thyristor switch as an instantaneous value when the instantaneous voltage drop occurs in the AC power supply, and sets the output period of the forced extinction pulse of the thyristor switch. It is variably set to a length suitable for the magnitude of the current instantaneous value. Thus, since the output period of the pulse signal is set to the minimum necessary period for the forced extinction of the thyristor switch, an increase in the load voltage due to the application of an unnecessary forced extinguishing output voltage is prevented.

Japanese Patent No. 2773214 Japanese Patent Laid-Open No. 5-68351 JP-A-5-115136

  By the way, as described above, the conventional instantaneous voltage drop countermeasure devices disclosed in Patent Documents 1 to 3 are connected to the thyristor switch connected between the AC power source and the load, and the load and the thyristor switch through the injection transformer. Connected to an inverter having a DC power supply. When an instantaneous voltage drop occurs in the AC power supply, a forced extinguishing pulse of a thyristor switch generated by the DC voltage of the inverter DC power supply is sent from the inverter through an injection transformer. After being applied to the switch and forcibly extinguishing the thyristor switch to turn it off, the voltage drop of the AC power supply is compensated by the output voltage of the inverter based on the DC voltage of the DC power supply.

  However, the DC voltage of the DC power supply of the inverter is not always constant, and the amplitude of the forced extinction pulse of the thyristor switch increases or decreases depending on the magnitude of the charging voltage, resulting in variations. In general, the larger the amplitude of the forced extinguishing pulse, the shorter the forced extinguishing time of the thyristor switch and the faster the thyristor switch can be turned off. Therefore, if there is a variation in the amplitude of the forced extinction pulse as described above, a variation occurs in the forced extinction time of the thyristor switch, and it becomes difficult to stabilize the forced extinction of the thyristor switch.

  Therefore, the present invention has been proposed in view of the above-mentioned problems, and the object of the present invention is to vary the forced extinction time of the thyristor switch without depending on the magnitude of the DC voltage of the DC power supply of the inverter. An object of the present invention is to provide an instantaneous voltage drop / power failure countermeasure device that can be suppressed as much as possible.

  As technical means for achieving the above object, the present invention relates to a thyristor switch connected between an AC power supply and a load, and an inverter having a DC power supply connected to the load and the thyristor switch via an injection transformer. And an instantaneous voltage drop / power failure countermeasure device that forcibly extinguishes the thyristor with the inverter output voltage based on the forced arc extinction pulse command value when an instantaneous voltage drop occurs in the AC power supply. A processing unit that generates a value, and the processing unit controls to reset the forced extinguishing pulse command value from the polarity of the thyristor current at a certain time after the start of forced extinguishing. And

  In the present invention, the processing unit that generates the forced extinguishing pulse command value performs control so that the forced extinguishing pulse command value is reset from the polarity of the thyristor current at that time after a lapse of a certain time from the start of forced extinguishing. As a result, variation in forced extinguishing time of the thyristor switch can be suppressed, increase in load voltage after forced extinguishing of the thyristor can be suppressed, and reliability in forced extinguishing of the thyristor can be improved. it can.

  The instantaneous voltage drop / power failure countermeasure device according to the present invention can be applied to either a parallel compensation system in which an injection transformer is connected in parallel to an AC power supply or a series compensation system in which an injection transformer is connected in series to an AC power supply. It is.

  The inverter constituting the instantaneous voltage drop / power failure countermeasure device of the present invention can be constituted by either a three-phase full bridge or three single-phase full bridges. The three-phase full-bridge inverter consists of six switching elements, and the three single-phase full-bridge inverters combine three single-phase full bridges composed of four switching elements. It consists of 12 switching elements. Therefore, regardless of the type of parallel compensation method or series compensation method described above, when using an inverter with a three-phase full-bridge configuration, the number of parts can be reduced compared to using an inverter with a single-phase full-bridge configuration. I can plan.

  According to the present invention, variation in the forced extinguishing time of the thyristor switch can be suppressed by changing the pulse pattern of the forced extinguishing pulse command value, and an increase in the load voltage after the forced extinguishing of the thyristor switch is also achieved. Can be suppressed. As a result, the forced extinction of the thyristor switch can be stabilized and the reliability can be improved.

In the embodiment of the present invention, it is a schematic configuration diagram showing an instantaneous voltage drop / power failure countermeasure device of a parallel compensation system in which an injection transformer is connected in parallel to an AC power supply. It is a schematic block diagram which shows the instantaneous voltage drop and power failure countermeasure apparatus of the series compensation system by which injection transformer was connected in series with AC power supply in other embodiment of this invention. It is a block block diagram of the process part which makes variable the amplitude of a forced extinction pulse command value according to the direct-current voltage value of direct-current power supply, and controls it so that the amplitude becomes equivalently constant. FIG. 4 is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply occurs for explaining control by the processing unit of FIG. 3. It is a block block diagram of the process part which controls so that the amplitude of a forced extinction pulse command value may be set to 0 when an inverter output current exceeds an overcurrent level. It is for demonstrating control by the process part of FIG. 5, and is an operation | movement waveform diagram of each part at the time of the instantaneous voltage drop generation | occurrence | production of alternating current power supply. It is a block block diagram of the process part which produces | generates the correction amount which makes a thyristor electric current 0, and makes the inverter output voltage which added the correction amount to the load voltage a forced extinction pulse command value. FIG. 8 is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply is generated, for explaining control by the processing unit of FIG. 7. It is a block block diagram of the process part which controls to reset a forced arc-extinguishing pulse command value from the polarity of the thyristor current at the time after a fixed time has passed since the start of forced arc-extinguishing. It is for demonstrating control by the process part of FIG. 9, and is an operation | movement waveform diagram of each part at the time of the instantaneous voltage drop generation | occurrence | production of alternating current power supply. It is a block block diagram of the processing part which synthesize | combines the two-phase forced arc-extinguishing pulse command value from which the polarity of a thyristor current differs, and controls to forcefully extinguish all three-phase thyristors. It is for demonstrating control by the process part of FIG. 11, and is an operation | movement waveform diagram of each part at the time of the instantaneous voltage drop generation | occurrence | production of alternating current power supply. It is a block block diagram of the process part which controls so that the remaining two-phase forced arc-extinguishing pulse command value is fixed when any one-phase thyristor current becomes zero. FIG. 14 is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply occurs to explain control by the processing unit of FIG. 13. It is a block block diagram of the process part which controls to invert the one-phase forced arc-extinguishing pulse command value when any one-phase thyristor current becomes zero. FIG. 16 is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply occurs to explain control by the processing unit of FIG. 15.

  An embodiment of the instantaneous voltage drop / power failure countermeasure device according to the present invention will be described in detail below. 1 and 2 show schematic configurations of two types of instantaneous voltage drop / power failure countermeasure devices. FIG. 1 shows a parallel compensation type instantaneous voltage drop / power failure countermeasure device in which an injection transformer is connected in parallel to an AC power source. FIG. 2 shows a series compensation type instantaneous voltage drop / power failure countermeasure device in which an injection transformer is connected in series to an AC power source. In addition, the same referential mark is attached | subjected about the part which is common in the instantaneous voltage drop / blackout countermeasure apparatus of FIG. 1 and FIG.

  The instantaneous voltage drop / power failure countermeasure device shown in FIGS. 1 and 2 is installed in a load power supply path 4 between an AC power source 1 such as a commercial power source and a load 3 connected via a load transformer 2.

  This instantaneous voltage drop / power failure countermeasure device is connected between an AC power source 1 and a load 3, and includes a thyristor switch 5 including a pair of thyristors 5 a and 5 b connected in reverse parallel to a load power supply path 4, and a load 3. The thyristor switch 5 is connected via an injection transformer 6 and connected to the load feed path 4 via an inverter 8 having a DC power supply 7 and an instrument transformer 9 provided on the AC power supply side of the thyristor switch 5. The reference voltage generation unit 10 and the power supply abnormality detection unit 11, the load voltage control unit 13 connected to the load power supply path 4 through the instrument transformer 12 provided on the load side of the thyristor switch 5, and the inverter 8 The main part is composed of the gate pulse generator 14 for performing arc extinction driving or compensation driving.

  The inverter 8 may have either a three-phase full-bridge configuration configured with six switching elements or a combination of three single-phase full bridges configured with four switching elements. In the case of a single-phase full-bridge configuration, a total of 12 switching elements are used, so that the three-phase full-bridge configuration is simpler in either the parallel compensation method or the series compensation method. The number of parts can be reduced as compared with the case of the phase full bridge configuration. As the DC power source 7, a large-capacity capacitor or the like is used.

  The reference voltage generation unit 10 and the power supply abnormality detection unit 11 monitor the presence or absence of an instantaneous voltage drop of the AC power supply 1. The reference voltage generation unit 10 generates a reference sine wave voltage based on the power supply voltage of the AC power supply 1. The power supply abnormality detection unit 11 compares the power supply voltage of the AC power supply 1 with the reference sine wave voltage from the reference voltage generation unit 10. When the power supply voltage of the AC power supply 1 is normal, the thyristor switch 5 is turned on based on the ignition signal output from the power supply abnormality detection unit 11, and the power supply voltage of the AC power supply 1 is changed to the thyristor switch 5 and the load transformer. 2 to load 3. On the other hand, when the power supply voltage of the AC power supply 1 is abnormal, that is, when an instantaneous voltage drop of the AC power supply 1 occurs, the thyristor switch 5 is turned off based on the arc extinguishing signal output from the power supply abnormality detection unit 11.

  Further, the load voltage control unit 13 outputs the output voltage command value of the inverter 8 from the load voltage detected from the load power supply path 4 through the instrument transformer 12 and the reference voltage output from the reference voltage generation unit 10 described above. Is transmitted to the gate pulse generator 14. The gate pulse generator 14 generates a gate pulse signal based on the output voltage command value output from the load voltage controller 13, and drives the inverter 8 with the gate pulse signal.

  In the instantaneous voltage drop / power failure countermeasure device of this embodiment, the main part including the thyristor switch 5, the inverter 8, the reference voltage generator 10, the power supply abnormality detector 11, the load voltage controller 13, and the gate pulse generator 14 is used. In addition, a DC voltage detection unit 15 connected to the DC side of the inverter 8, an AC current detection unit 16 connected to the AC side of the inverter 8, and a forced extinction pulse command value for forcibly extinguishing the thyristor switch 5 A processing unit 17 to be generated, and a control switching unit 18 that switches between the processing unit 17 and the load voltage control unit 13 are provided.

  In the processing unit 17, the input side is connected to the DC voltage detection unit 15 and the AC current detection unit 16, and the output side is connected to one switching terminal 18 a of the control switching unit 18. The other switching terminal 18b of the control switching unit 18 is connected to the output of the load voltage control unit 13 described above.

  In the instantaneous voltage drop / power failure countermeasure device having the above configuration, when the power supply voltage of the AC power supply 1 is normal, the power supply abnormality detection unit 11 compares the reference voltage output from the reference voltage generation unit 10 with the power supply voltage. It is determined that the voltage is normal, and the thyristor switch 5 is turned on based on the ignition signal output from the power supply abnormality detection unit 11. When the thyristor switch 5 is turned on, the power supply voltage of the AC power supply 1 is supplied to the load 3 via the thyristor switch 5 and the load transformer 2.

  On the other hand, when an instantaneous voltage drop occurs in the AC power supply 1, the power supply abnormality detection unit 11 compares the reference voltage with the power supply voltage to determine that the power supply voltage is abnormal, and is output from the power supply abnormality detection unit 11. The thyristor switch 5 is turned off based on the arc extinguishing signal. The DC voltage detector 15 detects the DC voltage of the DC power supply 7 of the inverter 8, and the optimum forced extinguishing pulse for forcibly extinguishing the thyristor switch 5 by the processing unit 17 based on the DC voltage of the DC power supply 7. Generate a command value.

  At this time, the control switching unit 18 is switched to the contact 18a to which the processing unit 17 is connected. An optimum forced extinguishing pulse command value for forcibly extinguishing the thyristor switch 5 is output to the gate pulse generating unit 14 via the control switching unit 18, and the inverter 8 is turned off by the output from the gate pulse generating unit 14. Arc drive. The thyristor switch 5 is turned off by the arc extinguishing drive of the inverter 8.

  After the thyristor switch 5 is turned off, the control switching unit 18 is switched to the contact 18b to which the load voltage control unit 13 is connected. As a result, the load voltage control unit 13 generates an output voltage command value of the inverter 8 from the load voltage and the reference voltage and outputs the output voltage command value to the gate pulse generation unit 14. The output from the gate pulse generation unit 14 compensates the inverter 8. To drive.

  When the thyristor switch 5 is turned off by forced extinction, the processing unit 17 makes the amplitude of the forced extinguishing pulse command value variable according to the DC voltage value of the DC power source 7 output from the DC voltage detection unit 15, Control is performed so that the amplitude of the forced extinction pulse command value is equivalently constant regardless of the DC voltage value of the power supply 7.

  FIG. 3 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 4 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

In this processing unit 17, the voltage command value preset by the command value setting unit 21 is divided by the charging voltage value output from the DC voltage detection unit 15, and its coefficient K _V (= 0 to 1) is divided into pulses. By multiplying the forced extinguishing pulse command value generated by the generating unit 23, the amplitude of the forced extinguishing pulse command value is made variable. As a result, the amplitude of the forced extinguishing pulse command value is equivalently constant regardless of the magnitude of the DC voltage value of the DC power supply 7 (see the lowest extinction pulse command value e in FIG. 4). ).

  As described above, the processing unit 17 makes the amplitude of the forced extinction pulse command value variable, and controls the amplitude of the forced extinction pulse command value to be equivalently constant regardless of the magnitude of the DC voltage of the DC power supply 7. By doing so, variation in the forced extinguishing time of the thyristor switch 5 can be suppressed, and an increase in load voltage after the thyristor forced extinguishing can also be suppressed.

  It is also possible to add an overcurrent protection function of the inverter 8 to the processing unit 17. The overcurrent protection function of the inverter 8 is to prevent a problem that the inverter 8 stops (trips) due to the overcurrent when the overcurrent flows through the inverter 8 while the thyristor switch 5 is forcibly extinguished. is there. The overcurrent detection of the inverter 8 is performed by the alternating current detection unit 16 shown in FIGS. 1 and 2, and the forced extinguishing pulse command value is controlled by the processing unit 17 based on the output of the alternating current detection unit 16.

  FIG. 5 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 6 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

  In this processing unit 17, the absolute value of the inverter output current detected by the above-described alternating current detection unit 16 is calculated by the calculation unit 31, and the absolute value and the current upper limit value preset by the upper limit value setting unit 32 are calculated. Are compared by the determination unit 34.

Result of comparison in the determination unit 34, is smaller than the absolute value of the current upper limit value, the current detection value is not over-current level, as a coefficient K _I described above, forced extinguishing generated by the pulse generator 33 The amplitude of the pulse command value is output to the gate pulse generator 14 as it is. On the other hand, if greater than the absolute value of the current upper limit value, the current detection value is overcurrent level, as 0 a coefficient K _I described above, by the amplitude of the forced extinguishing pulse command value to zero, the The forced arc-extinguishing pulse command value is narrowed down (the forced arc-extinguishing pulse command value is set to a 50% duty pulse) and output to the gate pulse generator 14 (the lowest stage in FIG. reference). Thereby, the inverter 8 can be protected against the occurrence of overcurrent, and the overcurrent capability of the inverter 8 can be reduced.

  The processing unit 17 that generates the forced arc-extinguishing pulse command value generates a correction amount that sets the thyristor current to 0, and uses the inverter output voltage obtained by adding the correction amount to the load voltage as the forced arc-extinguishing pulse command value.

  FIG. 7 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 8 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

  The processing unit 17 calculates the difference between the thyristor current command value (= 0) preset by the command value setting unit 41 and the thyristor current detection value output from the current transformer 19, and based on the difference, calculates the thyristor. A correction amount generating unit 42 generates a correction amount for setting the current to 0, and outputs a forced extinguishing pulse command value obtained by adding the correction amount to the load voltage to the gate pulse generating unit 14 (the lowest stage in FIG. (Refer to arc extinction pulse command value e).

  In this way, by generating a correction amount that makes the thyristor current 0, and using the inverter output voltage obtained by adding the correction amount to the load voltage as the forced extinction pulse command value, the variation in the forced extinction time of the thyristor switch 5 is varied. And an increase in load voltage after forced extinction of the thyristor can also be suppressed.

  The processing unit 17 that generates the forced extinguishing pulse command value performs control so as to reset the forced extinguishing pulse command value from the polarity of the thyristor current at a certain time after the start of forced extinguishing.

  FIG. 9 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 10 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

  In this processing unit 17, after setting the first forced extinguishing pulse command value, when a certain time (retry time) has elapsed from the start of forced extinguishing by the internal timer 51, the forced extinguishing pulse command value is determined from the polarity of the thyristor current. If the polarity of the thyristor current is not changed, if the polarity of the thyristor current is not changed, the forced extinguishing pulse command value is output as it is to the gate pulse generator 14 and if the polarity of the thyristor current is changed. The second forced extinguishing pulse command value is reset, and the forced extinguishing pulse command value reset by the pulse generating unit 53 is output to the gate pulse generating unit 14 (the lowest stage in FIG. 10, forced extinguishing) (Refer to the pulse command value e). The retry time is preset by the time setting unit 54.

  In this way, after a certain period of time has elapsed since the start of forced extinguishing, control is performed to reset the forced extinguishing pulse command value from the polarity of the thyristor current at that time, thereby reducing the variation in the forced extinguishing time of the thyristor switch. It is possible to suppress the increase in the load voltage after forced extinction of the thyristor and to improve the reliability of the thyristor in forced extinction.

  When the injection transformer 6 (see FIGS. 1 and 2) interposed between the load 3 and the thyristor switch 5 and the inverter 8 is configured by Y-Δ or Δ-Y connection, a forced extinguishing pulse command value is generated. The processing unit 17 performs control so that all the three-phase thyristors are equivalently forcibly extinguished by synthesizing two-phase forced extinction pulse command values having different thyristor current polarities.

  FIG. 11 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 12 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

  In the processing unit 17, the amplitude of the two-phase forced extinguishing pulse command value having different thyristor current polarities is set as it is, and a rectangular wave pulse (with a duty ratio of 50) generated by the pulse generating unit 61 is used. %) Is multiplied by one forced arc-extinguishing pulse command value generated by the pulse generating unit 63a, and the rectangular wave pulse inverted by the inverting unit 64 is multiplied by the other forced extinguishing unit generated by the pulse generating unit 63b. Multiply the arc pulse command value. Then, by adding these two-phase forced extinction pulse command values, a compulsory extinction pulse command value for forcibly extinguishing all three-phase thyristors is output to the gate pulse generator 14 (the maximum in FIG. 12). (See lower, forced extinction pulse command value e).

  In this way, by compiling two-phase forced extinguishing pulse command values having different thyristor current polarities and equivalently controlling all the three-phase thyristors to be extinguished, forced extinction of the thyristor switch 5 is performed. Variations in time can be suppressed, and an increase in load voltage after forced extinction of thyristors can also be suppressed.

  The processing unit 17 synthesizes two-phase forced arc extinguishing pulse command values having different thyristor current polarities and equivalently controls all three thyristors to forcibly extinguish any one phase. When the thyristor current becomes zero, the remaining two-phase forced extinguishing pulse command value may be controlled to be fixed.

  FIG. 13 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 14 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

  In this processing unit 17, the amplitude of the two-phase forced extinguishing pulse command value having different thyristor current polarities is set as it is, and a rectangular wave pulse (with a duty ratio of 50) generated by the pulse generation unit 71 is used. %) Is multiplied by one forced arc-extinguishing pulse command value generated by the pulse generator 73a, and a rectangular wave pulse inverted by the inverter 74 is generated by the other forced extinction generated by the pulse generator 73b. Multiply the arc pulse command value. Then, by adding these two-phase forced extinguishing pulse command values, a compulsory extinction pulse command value for forcibly extinguishing all three-phase thyristors is output to the gate pulse generator 14. However, when any one-phase thyristor current becomes 0, the remaining two-phase forced extinguishing pulse command value is fixed with the aforementioned duty ratio set to 100% (the lowest stage in FIG. See value e).

  In this way, when two-phase forced extinguishing pulse command values having different thyristor current polarities are combined and controlled to forcibly extinguish all three phase thyristors, any one-phase thyristor current is By controlling so that the remaining two-phase forced extinguishing pulse command value is fixed when it becomes 0, the variation in the forced extinguishing time of the thyristor switch 5 is suppressed, and the load voltage after the thyristor forced extinguishing is increased. Suppression is even more certain.

    When the injection transformer 6 (see FIGS. 1 and 2) interposed between the load 3 and the thyristor switch 5 and the inverter 8 is configured by Δ-Δ or YY connection, a forced extinction pulse command value is generated. The processing unit 17 performs control so as to invert the one-phase forced extinguishing pulse command value when any one-phase thyristor current becomes zero.

  FIG. 15 shows a block configuration of the processing unit 17 for realizing the control described above. FIG. 16 is a diagram for explaining the control by the processing unit 17, and is an operation waveform diagram of each unit when an instantaneous voltage drop of the AC power supply 1 occurs. The AC power supply voltage a is sequentially from the top in the figure. , Load voltage b, thyristor current c, load current d, and forced extinction pulse command value e.

  In this processing unit 17, after the first forced extinguishing pulse command value is set by the pulse generation unit 83a, the determination unit 81 determines that any one-phase thyristor current has become 0, and at that time Then, by switching the switch 82, the one-phase forced extinguishing pulse command value is inverted and the second forced extinguishing pulse command value is reset by the pulse generator 83b, and the reset forced extinguishing command is reset. The pulse command value is output to the gate pulse generator 14 (see the lowest stage in FIG. 16, forced extinction pulse command value e).

  As described above, when one of the thyristor currents of one phase becomes 0, by controlling so that the forced extinguishing pulse command value of the one phase is reversed, the load voltage after the thyristor forced extinguishing is also increased. Can be suppressed.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the scope of the present invention. The scope of the present invention is not limited to patents. It includes the equivalent meanings recited in the claims, and the equivalent meanings recited in the claims, and all modifications within the scope.

1 AC Power Supply 3 Load 5 Thyristor Switch 6 Injection Transformer 7 DC Power Supply 8 Inverter 17 Processing Unit

Claims (3)

A thyristor switch connected between an AC power supply and a load, and an inverter having a DC power supply connected to the load and the thyristor switch via an injection transformer, when an instantaneous voltage drop occurs in the AC power supply, An instantaneous voltage drop and power failure countermeasure device that forcibly extinguishes a thyristor with an inverter output voltage based on a forced arc extinction pulse command value,
A processing unit that generates the forced extinguishing pulse command value, and the processing unit resets the forced extinguishing pulse command value from the polarity of the thyristor current at a certain time after the start of forced extinguishing. Instantaneous voltage drop / power failure countermeasure device characterized by   2. The instantaneous voltage drop / power failure countermeasure device according to claim 1, wherein the injection transformer is connected to the AC power supply by either parallel connection or series connection.   The instantaneous voltage drop / power failure countermeasure device according to claim 1, wherein the inverter is configured by one of a three-phase full bridge and three single-phase full bridges.

Images