JPS60200769A - Power converter - Google Patents

Abstract

PURPOSE:To turn OFF in a safely operating range by inserting a current conversion rate limiter to the input side of a power converter, and discharging stored energy of a surge voltage absorber when the converter is turned OFF. CONSTITUTION:A current change rate limiter in which a reactor 13 and a diode 14 are connected in parallel is inserted to between a power converter 2 in which self-extinguishing elements are connected in a bridge and a DC power source 1. Further, an electric valve 16 is connected through a current limiting impedance 17 with both ends of a capacitor 5 which forms a surge voltage absorber. When an overcurrent is detected by an overcurrent detector 8, the valve 16 is closed to discharge the stored energy of the capacitor 5, and the elements in the converter 2 are turned OFF after a time slightly delayed by a relay 18.

Description

[Detailed description of the invention]

[Technical Field of the Invention] This invention relates to a power conversion device using self-extinguishing elements such as transistors and gate turn-off switches.
The present invention relates to a receptacle and a force converter equipped with a protection circuit that can reliably turn off a self-arc-extinguishing element within a safe operation range in the event of a failure such as a short circuit accident. [Technical background of the invention and its problems] FIG. 1 shows an example of a circuit diagram of a power conversion device having a power conversion circuit using a self-extinguishing element in the power conversion section. In the circuit shown in FIG. 1, a transistor is used as a self-converting element, and the power conversion circuit is configured as a transistor bridge. Overcurrent protection of the transistors constituting the transistor inverter in the circuit of FIG. 1 will be explained. The DC power supplied from the DC power supply 1 is converted into AC by the transistor bridge 2, and is supplied to the 9-load electric power @7. Here, transistor bridge 2 is transistor 2
] , 22 , 23 , 24 , 25 , 26 and diodes 31 , 32 , 33 , 34 , 35 , 36 inserted between the collector and emitter of this transistor.
It consists of Furthermore, a surge voltage absorbing circuit including a diode 3, a capacitor 5, and a resistor 4 is connected in parallel to the input side of the transistor bridge 20. The surge box-pressure absorption circuit is for absorbing surge voltage during commutation of the transistor bridge 2, and recently it has been connected to the input side (DC side) of the transistor bridge 2, as shown in Figure 1. This is the general configuration of Therefore, the transistors constituting the bridge 2 are used without being connected to a snubber circuit. , the DC side current is detected by a current detector 6, and when the current level flowing through the inverter 2 becomes excessive, this is detected by an overcurrent detector 8 and a detection signal is output. This detection signal is inputted to the AND circuit jO together with the transistor bridge control signal 9, and operates to turn off all transistors forming the pulley switch 2 when an overcurrent is detected. AND circuit 10
The output drives each transistor in the bridge 2 via the drive circuit 11 to perform DC/AC conversion. ℃・If we consider the case where a load short-circuit accident occurs at point 12 (hereinafter referred to as the accident point), the DC power source l
This is equivalent to connecting the transistors 21 and 26 through a series circuit. In any case, it cannot be expected that the voltage will be equally distributed and applied to the two transistors 21 and 26. Especially at the moment of turn-off, the unbalance becomes large, and the transistor often deteriorates beyond its safe operating range. When the collector-emitter voltage Vaax (SO8) is 1000 V or higher, there is little margin in the reverse bias safe operation area, so if a short circuit occurs when the voltage of the DC power supply J increases, conventional protection circuits will prevent transistor deterioration. In some cases, it was not possible to prevent this. Figure 2 is a diagram for explaining the safe operating area in the event of a short-circuit accident of a transistor (al is the equivalent circuit in the event of a short-circuit). Changes in collector box current, current C, and collector-emitter VOR when a pulsed base angle: current ■B is supplied to transistor 21, DC t, and source 1 are short-circuited by transistor 21. The waveform diagram is shown in Figure 2 (bL
Show K. Immediately after the transistor 21 starts turning off at time t1, the collector-emitter pressure VOID increases, and at that point the collector current LO is also large, so it exceeds the safe operating area, and the transistor diagram (C) shows the safety in the case of a short circuit. FIG. 3 is a characteristic diagram showing an example of an operating region. Collector current IC
If the current is less than 100% of the transistor, the transistor is ■. (SO8) can enter 100% voltage, but in the event of an accident, the collector is normally open and the current is about 400 to 500% of the transistor rating, so the withstand voltage Vcwx (sus) at this time is 60 to 70L1. ). For this reason, if the voltage of the DC type #j1 is high, the transistor cannot be completely protected from short-circuit accidents, and if it is necessary to ensure reliability, the DC power supply voltage must be lowered, or the transistor may be connected in parallel with a resistor. A diode connected in series with a snubber was used for each transistor. In the former case, the output voltage of the inverter becomes insufficient because the transistors are used with derating. Therefore, in this case, there is a disadvantage that a load motor having a standard voltage cannot be used as a load motor. In the latter case, the snubber loss becomes large and the transistor bridge is easily connected to the large snubber capacitor (number μ
If the transistor is not connected to the transistor (approximately F), it will not be possible to absorb the surge voltage that occurs when turning off an overcurrent, and furthermore, switching the transistor at several kHz will result in a very large switching loss. Therefore, this latter circuit is not practical in circuits where the switching frequency is high.
When a 'A current is generated due to a load smoke path or a grounding accident, the self-extinguishing elements that make up the inverter are turned off, without increasing switching loss, and the inverter bridge's DC power supply voltage remains as high as possible for safe operation. It is an object of the present invention to provide a voltage conversion device that can be turned off within a range. [Summary of the Invention] In order to achieve the above object, the present invention provides a power conversion circuit whose input side is connected to a DC power supply and whose output side is connected to a load, and uses a self-extinguishing element in the power conversion section, and this power conversion circuit. A surge voltage absorption circuit connected in parallel to the input side of the circuit,
In a power converter device comprising a protection circuit that turns off the self-extinguishing element when a current flowing through the power converter circuit exceeds a predetermined value, an input side 1 of the power converter circuit and the DC power source are connected to each other. a current conversion rate limiting circuit inserted in series between them; and a current limiting impedance connected to a part of the surge voltage absorption circuit to limit at least a portion of the electrical energy accumulated in the surge voltage absorption circuit when a surge voltage occurs. Embodiments of the Invention The present invention is characterized in that it is provided with an electric valve that discharges electricity through the electric valve, and a means for causing the on-timing of the electric valve to precede the off-timing of the self-arc-extinguishing element. will be explained in detail based on examples.Third
The figure is a circuit diagram showing one embodiment of the present invention. Note that the first
The same parts as shown in the figures are given the same reference numerals, and the explanation thereof will be omitted. A current change rate limiting circuit including a reactor 13 and a diode 14 connected in parallel is inserted between the DC circuit between the DC power source 1 and the transistor bridge 2. Further, an electric valve such as a transistor 16 is connected to both ends of the capacitor 5 constituting the surge voltage absorption circuit via a current limiting impedance such as a resistor 17. The overcurrent detection circuit 8 then detects a short circuit or grounding accident on the load side, and drives the pace of the transistor 16 via the one-shot circuit 15.

[Turn on 6, resistor 17
The electrical energy stored in the capacitor 5 is discharged. On the other hand, after a slight delay from the output of the overcurrent detector 8 by the relay circuit 18, the AND circuit O turns off all the transistors constituting the transistor bridge 2 to cut off the fault current. In this way, when the load is short-circuited, the voltage between the DC terminals of the transistor bridge 2 decreases due to the effect of the accelerator 13, and by detecting an overcurrent, the capacitor 5 is discharged, and the transistor of the transistor bridge 2 is turned off with the capacitor 5 discharged. Cut off the fault current within the operating area. This situation will be explained in more detail with reference to various waveform diagrams shown in FIG. At time to, the short circuit point 12 shown in FIG.
Assuming that a short-circuit accident occurs in , a short-circuit is created in which the DC power source 1 → reactor 13 → transistor 21 → transistor 26 → lightning current detector is supplied with oxygen, and the collector current IC of transistors 21 and 26 increases. However, the DC side voltage vc of the transistor bridge 2 gradually decreases due to the influence of the reactor 13 and gradually increases. At time t1, when the current reaches the overcurrent level, the overcurrent detection circuit 8 outputs an overcurrent detection signal 8. The one-shot circuit 18 receives the v8 signal and outputs the VI5 signal, turns on the transistor 16, and rapidly discharges the charge in the capacitor 5 through the resistor 17, so that the initial value of the voltage ■c of the capacitor 5 is approximately the same as the DC power supply l. However, it rapidly discharges from time t2. The overcurrent detection signal 8 becomes a failure signal VI8 via the relay circuit 18, and at the moment the transistor bridge 2
An off signal for turning off all the transistors constituting the circuit is output, but the current E starts decreasing at time t4 with a slight delay due to the delay time of the transistors. At this point, the capacitor 5 has almost completed discharging, and the voltage VOE applied to the transistor bridge 2 is
Start rising from a lower value. Therefore, safe turn-off is possible within the safe operating area of the transistor. At time t5, the transistor current o becomes below the overcurrent level and becomes 0 at time 0, so the transistor bridge 2 is safely turned on. After that, at time t7, the transistor 16 is turned off by the signal 15, and at this time too, a pot voltage is generated at the input terminal of the transistor bridge 2, but the transistor bridge 2 is completely turned off at σ], and the safe operation button is activated. There is a relationship fI in the area. At time t8, capacitor 5 matches the voltage of DC power supply 1, and reactor 1
Since the energy flowing through the diode 3 circulates through the diode 14, no surge voltage is generated. In order to reduce the surge voltage value that occurs at the moment of turning off such a large fault current and turn off the circuit, it is possible to construct a safe timekeeping circuit that always operates within the safe operating area. In addition, in consideration of grounding accidents, as shown in Figure 3,
By also connecting the diode 14 to the negative side of the DC power supply 1, the transistor can be turned off within the safe operating range while limiting the ground current. Furthermore, the relay circuit 18 explained in FIG.
Transistor bridge 2 with a turn-on time of 6
The turn-off time of the transistor in transistor 16 is
Since it is about 5 to 10 times longer than the turn-on time of , it may be omitted, and the same effect can be achieved in this case as well. FIG. 5 is a circuit diagram showing another embodiment of the invention. As shown in this figure, the AC power supply 103 and the accelerator 10
0, the voltage detection circuit 20 detects that the DC power supply voltage has increased due to the regenerated energy from the load 7. , when the value is higher than the set value, the output V2D is output and the OR circuit 21 outputs the third signal.
A logical OR with the overcurrent signal V15 explained in the figure is taken to drive the transistor I6. This makes it possible to have both the function of discharging the regenerative energy from the load 7 through the resistor 17 and the function of turning off the transistor within the safe operation button range at the time of the breakdown current as explained in FIG. FIGS. 6 and 7 are circuit diagrams showing other embodiments of the discharge circuit consisting of the current impedance 17 and the electric valve I6 constructed in FIGS. 3 and 5. As shown in FIG. 6, resistor 17 is connected to resistor 117 and capacitor 1.
18 in series and a resistor 119 connected in parallel. capacitor 11
The capacitor 8 is made to have a much larger capacity than the capacitor 5, and the time constant consisting of the resistor 117 and the capacitor 11B is set to be equal to or more than the tens of microseconds that the transistor bridge 2 takes to shut off the electric power due to an accident. Note that resistance 119
is for discharging the capacitor 118. Such a configuration has the advantage that the heat capacity of the resistor 117 and the transistor 16 can be rated for a short period of time, and furthermore, the size can be reduced. In FIG. 7, a thyristor 116 is used instead of the transistor 16 as an electric valve, and a capacitor 118, a resistor 119, and a reactor 120 are used as current impedance. By connecting reactor 120 to capacitor 118 in series, reactor 1
20 and the capacitor 118, a large current is rapidly discharged from the capacitor 5, and at the same time K, sai IJ
It becomes possible to turn on the star 116. FIG. 8 is a circuit diagram showing still another embodiment of the present invention. In this case, the reactor 13 utilizes the self-impedance included in the circuit, and a special accelerator may not be attached. This can be used when the transistor bridge 20 safe operating area is slightly exceeded. By bypassing a portion of the current that has turned off the transistor bridge 2 through a series circuit of a resistor 117 and a capacitor 118, the rise in voltage is suppressed. This ensures a safe operating area for the transistors within the transistor bridge 2. Note that the connecting pin 17 in FIG. 8 is for regenerative energy discharge, and by connecting it to a circuit that does not pass through the diode 3, the current capacity can be increased by the diode 30. Furthermore, if the transistor 16 is selected appropriately, the resistor 117 can be omitted. In the above explanation, a transistor is used as a self-extinguishing element used in a power conversion circuit, but the present invention also applies when other self-extinguishing elements such as a gate turn-off transistor (GTO) are used. Needless to say, it can be applied. Furthermore, when the rectifier 101 shown in FIG. 5 is constructed using a transformer using self-arc-extinguishing elements, the same can be done by replacing the load 7 of the inverter bridge 2 shown in FIG. 3 with an AC type one. It can be made to have a certain effect. Further, as shown in FIG. 9, a method in which the capacitor 118 and the transistor 16 are connected in series to the DC side of the transistor bridge 2 has a similar effect. Note that the resistor 119 is for discharging the capacitor 118. At this time, the capacitance of the capacitor 118 is set to be within the safe operating range when the transistor 16 is turned on, so that the charging time is 50 to 10 minutes.
It is desirable to select 0μθ or less. The surge clamp capacitor 5 is as shown in FIG.
If the switching frequency of the transistor bridge 2 is low, it can be connected directly to the DC bus. [Effects of the Invention] As described above in detail based on the embodiments, according to the present invention, since the DC side voltage of the impark bridge is reduced when the inverter and main body are turned off, the inverter It is possible to turn off within the safe operating range of the self-extinguishing element constituting the bridge. Therefore, there is an advantage that a power conversion device having a highly reliable protection circuit can be realized.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional power conversion device, Fig. 2 is a diagram for explaining the waveform and safe operating area of a transistor when the load is short-circuited, and Fig. 3 is a circuit diagram showing an embodiment of the present invention. , FIG. 4 is an explanatory diagram of the operation of the circuit shown in FIG. 3, and FIGS. 5 to 9 are circuit diagrams showing other embodiments of the present invention. 1... DC power supply, 2... Transistor bridge, 5
...Capacitor, 13...Reactor, 14...
Diode, 16...Transistor, 17...Resistor, 116...Sirisk. Applicant's agent Kiyoshi Inomata Figure 1 to Figure 2 Figure 3 Figure 4 Figure 5 Figure 10; Figure 6 Figure 7

Claims (3)

[Claims] (1) A power conversion circuit whose input side is connected to a DC power supply and its output side is connected to a load, using a self-extinguishing element in the power conversion section, and a surge voltage absorption circuit connected in parallel to the input side of this t-force conversion circuit. and a protection circuit that turns off the self-arc-extinguishing element when the current flowing through the power conversion circuit exceeds a predetermined value. A current conversion rate limiting circuit inserted in series with the DC power source; and a current conversion rate limiting circuit connected to a part of the surge voltage absorption circuit, which controls at least the electrical and electrical energy accumulated in the surge voltage absorption circuit when surge suppression pressure occurs. An electric valve that discharges a portion through current limiting/impedance;
A power g-equipped monk characterized in that the on-timing of the electric valve is controlled by the self-extinguishing element. (2) The power conversion device according to claim (1), wherein the current change rate limiting circuit includes a reactor and a diode connected in parallel to the reactor. (3) The surge voltage clamp circuit includes a diode and a capacitor connected in series with the diode, and one end of the current limiting impedance is imaginary coupled to the diode and the capacitor. A power conversion device according to claim (1).