JP2006230168A - Electric power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power converter which suppresses an increase in a switching element loss, while suppressing a surge voltage by an active gate drive technology. <P>SOLUTION: A snubber circuit discharges through a snubber resistance 14 during a switching element 9 or a flywheel 10 is turned on, and an electric charge of a snubber capacitor 13 becomes zero. The switching element 9 starts an off operation in this state, and if its collector current rapidly decreases, a main current flowing through the switching element 9 till that time commutates to a snubber diode 12 and the snubber capacitor 13. If gate resistance 3 is made sufficiently low in such a state, the collector current of the switching element 9 decreases very quickly, so that a turn-off loss of the switching element 9 is made very small, and a rate of voltage rise is suppressed to be a certain value by an operation of the snubber circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power converter.

  Power converters using power switching elements are steadily expanding their application range as the capacity and speed of switching elements increase. As such power switching elements, IGBTs and MOSFETs, which are MOS gate type switching elements, have recently expanded their application fields.

  IGBTs and MOSFETs are non-latching switching elements that do not self-continue in an on / off state, and have a great advantage in that high controllability by gate driving is possible as compared with latching switching elements such as thyristors. This non-latching switching element can suppress surge voltage and surge current by gate control even during turn-on and turn-off switching transients, and can freely control the current and voltage gradient during switching transients. Is possible.

  As an application example utilizing the characteristics of such a non-latching type switching element, there is a multi-series high-voltage converter based on an active gate driving technique. A multi-series high-voltage converter is a high-voltage converter that can be used for high-voltage applications such as a power system by connecting a large number of elements having a limited withstand voltage in series. However, the multi-series high-voltage converter has a problem in that a large variation in voltage sharing occurs due to a slight shift in switching timing between a large number of elements connected in series. Active gate drive technology has been proposed as a countermeasure against this.

  A gate driving circuit based on this active gate driving technique is shown in FIG. 8, 1a and 1b are gate power supplies, 2 and 5 are voltage amplifiers, 3 is gate resistance, 4a and 4b are voltage dividing resistors, 6 is a control current source, 7 is a capacitor, 8 is a diode, and 9 is for power. The switching element 10 represents a flywheel diode. A gate electrode, which is a control input terminal of the switching element 9, is connected to the voltage amplifier 2 through the gate resistor 3 and is also connected to the output of the control current source 6. The input of the control current source 6 is connected to the output of the voltage amplifier 5. A voltage between the collector and the emitter of the switching element 9 divided by the voltage dividing resistors 4a and 4b is applied to the input of the voltage amplifier 5. In this circuit, in a normal operation state, the switching element 9 performs an on / off operation in accordance with a gate signal applied via the voltage amplifier 2, but when a surge voltage is generated when the switching element 9 is turned off, the control current source The output current from 6 increases. The gate voltage of the switching element 9 increases due to the current flowing from the control current source 6 to the gate terminal of the switching element 9, thereby increasing the collector current of the switching element 9, and as a result, the collector voltage of the switching element 9 decreases. . In this circuit, the surge voltage of the switching element 9 is suppressed by such an operation.

  However, the proposed technique is a method of suppressing the generation of a surge voltage by performing feedback control of the main voltage Vce of the switching element in the gate drive circuit. In this method, there is an advantage that the circuit configuration is simple in that no main circuit element other than the switching element is required, but on the other hand, since the switching element has to share all of the loss, the element loss Another problem remains that increases. This problem will be described.

  When the switching element switches, a switching loss occurs. Turn-on loss occurs at turn-on, and turn-off loss occurs at turn-off. The value of this loss strongly depends on the voltage rise rate at turn-off and the current rise rate at turn-on. It is known to do. In simple terms, the switching loss is inversely proportional to the rate of increase.

  On the other hand, the voltage rise rate and current rise rate during switching are closely related to the electromagnetic interference generated by the power converter, and it is known that the greater the rate of increase, the more likely it is to damage peripheral electrical equipment. ing. For example, when the power converter is a voltage type inverter that drives an electric motor, the surge voltage applied to the motor terminal voltage increases as the voltage rise rate of the pulse voltage at the output terminal of the inverter increases, and the insulation deterioration of the electric motor is reduced. It is well known that it will be accelerated.

  Therefore, in the gate drive circuit based on the proposed active gate drive technology, if there is no main circuit element other than the switching element, suppress the voltage rise rate and current rise rate during switching in order to suppress electromagnetic interference. If this is the case, the loss of the switching element inevitably increases, and this increase in the element loss has a problem that the output capacity of the power converter decreases and the cost of the converter increases.

  The present invention has been made in view of the problems of the proposed active gate drive technology as described above, and can suppress the increase in element loss while suppressing the surge voltage by the active gate drive technology. An object is to provide a converter.

  The present invention relates to a non-latching switching element having two main electrodes, one control electrode, a snubber circuit for suppressing a voltage increase rate of the switching element, and a voltage applied between the main electrodes of the switching element. A power converter comprising: voltage detecting means for detecting the voltage; and control means for controlling a voltage applied to the control electrode or a current flowing through the control electrode in accordance with a voltage detected by the voltage detecting means. To do.

  The present invention is also applied between a non-latching switching element having two main electrodes, one control electrode, a snubber circuit for suppressing a current rise rate of the switching element, and the main electrode of the switching element. A power converter comprising: voltage detection means for detecting a voltage; and control means for controlling a voltage applied to the control electrode or a current flowing through the control electrode in accordance with a voltage detected by the voltage detection means. And

  The present invention also provides a non-latching switching element having two main electrodes, one control electrode, a first snubber circuit for suppressing a voltage increase rate of the switching element, and a current increase rate of the switching element. A second snubber circuit for suppressing, a voltage detection means for detecting a voltage applied between the main electrodes of the switching element, and a voltage applied to the control electrode in accordance with the voltage detected by the voltage detection means Or a power converter provided with the control means which controls the electric current which flows into the said control electrode makes it a summary.

  According to the present invention, the surge voltage applied to the switching element can be suppressed by applying the active gate driving technique, and the voltage increase rate and current increase rate during switching are suppressed by the snubber circuit. Regardless of the application of the active gate driving technique, an increase in switching element loss can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  (First Embodiment) FIG. 1 is a circuit diagram of a power converter according to a first embodiment of the present invention. In FIG. 1, the same or equivalent elements as those in FIG. 8 are denoted by the same reference numerals. In the present embodiment, the switching element 9 is driven by the active gate circuit 11. The internal configuration of the active gate circuit 11 is the same as that in FIG. In addition to this, in FIG. 1, a snubber circuit including a snubber diode 12 and a snubber capacitor 13 is connected in parallel to the switching element 9, and a snubber resistor 14 is connected in parallel to the snubber diode 12.

  The operation of the power converter according to the first embodiment having the above configuration will be described. The snubber circuit constituted by the snubber diode 12 and the snubber capacitor 13 discharges via the snubber resistor 14 while the switching element 9 or the flywheel diode 10 is on, and the charge of the snubber capacitor 13 becomes zero. In this state, when the switching element 9 starts to turn off and the collector current of the switching element 9 rapidly decreases, the main current that has been flowing through the switching element 9 is commutated to the snubber diode 12 and the snubber capacitor 13. If the inductance component of the snubber circuit is sufficiently small, the commutation of the main current to the snubber circuit is performed quickly, and the collector-emitter voltage of the switching element 9 is constant determined by the capacity of the snubber capacitor 13 and the value of the main current. It begins to rise slowly with a voltage rise rate. The decreasing rate of the collector current of the switching element 9 is determined by the gate resistance 3 inside the active gate circuit 11. Therefore, if the gate resistance 3 is made sufficiently small, the collector current of the switching element 9 decreases very rapidly, so that the turn-off loss of the switching element 9 can be made very small. Moreover, even in that case, the voltage increase rate can be suppressed to a certain value by the action of the snubber circuit.

  According to the present embodiment, the voltage increase rate can be suppressed by the snubber circuit at the same time while the surge voltage suppression function by the active gate circuit 11 is provided, thereby suppressing the increase in the loss of the switching element 9.

  (Second Embodiment) FIG. 2 is a circuit diagram of a power converter according to a second embodiment of the present invention. In FIG. 2, the same or equivalent components as those in FIGS. 1 and 8 are denoted by the same reference numerals. In the first embodiment, the voltage increase rate when the switching element is turned off is suppressed by the snubber circuit to reduce the turn-off loss. However, in this embodiment, the current increase rate at turn-on is suppressed by the snubber circuit. The anode reactor 15 is connected in series with the switching element 9 as a snubber circuit element.

  The operation of the power converter of the second embodiment having the above configuration will be described. If the gate resistance 3 is set to a sufficiently small value, the collector-emitter voltage of the switching element 9 rapidly decreases at turn-on. At this time, the voltage previously applied to the switching element 9 is applied to the anode reactor 15 connected in series to the element. As a result, the main circuit current slowly rises at a constant value determined by the inductance value of the anode reactor 15 and the main circuit voltage. Since the voltage of the switching element 9 is already sufficiently low when the main circuit current rises, the turn-on loss can be made very small.

  According to the present embodiment, the current rise rate can be suppressed by the snubber circuit while the surge voltage suppression function by the active gate circuit 11 is provided, thereby suppressing an increase in the loss of the switching element 9.

  (Third Embodiment) In the second embodiment, energy stored in the anode reactor 15 is not particularly taken into consideration, but an anode reactor having a large inductance value is used in order to suppress the current increase rate to a low value. When 15 is used, the energy becomes a turn-off loss of the switching element 9. The third embodiment of the present invention is characterized in that when the anode reactor 15 having a large inductance value is used, the countermeasure for the turn-off loss is taken.

  FIG. 3 is a circuit diagram of a power converter according to the third embodiment of the present invention. In FIG. 3, the same or equivalent components as those in FIGS. 1, 2, and 8 are denoted by the same reference numerals. In FIG. 3, a snubber circuit in which a snubber diode 12 and a snubber resistor 14 are connected in series is connected to the anode reactor 15 in parallel, and a snubber capacitor 13 is connected in parallel to the snubber resistor 14.

  The operation of the power converter of the third embodiment having the above configuration will be described. The action of suppressing the turn-on loss of the switching element 9 by the anode reactor 15 is the same as that of the second embodiment, but the action when the switching element 9 is turned off is different from that of the second embodiment. When the switching element 9 is turned off, the current that has been flowing to the anode reactor 15 until then flows into the snubber resistor 14 and the snubber capacitor 13 through the snubber diode 12. While the snubber diode 12 is conducting, the voltage across the snubber capacitor 13 is applied to the anode reactor 15 in the opposite direction, so that the current in the anode reactor 15 decreases and eventually the current in the anode reactor 15 becomes zero. The snubber diode 12 is turned off and the energy transferred to the snubber capacitor 13 is consumed by the snubber resistor 14. In the present embodiment, the snubber capacitor 13 is used, but this is not always necessary. In many cases, the use of only the snubber resistor 14 can achieve the purpose.

  According to the present embodiment, it is possible to suppress an increase in turn-on loss of the switching element 9 by suppressing the current increase rate by the snubber circuit while having the function of suppressing the surge voltage by the active gate circuit 11. Moreover, the turn-off loss of the switching element 9 is not increased by the energy stored in the snubber circuit.

  (Fourth Embodiment) In the first to third embodiments, the loss of only one of the turn-on side and the turn-off side is reduced. However, both of them can be performed simultaneously. . The power converter according to the fourth embodiment of the present invention is characterized in that the loss on both the turn-on side and the turn-off side of the switching element is reduced. FIG. 4 is a circuit diagram of a power converter according to the fourth embodiment of the present invention. In FIG. 4, the same or equivalent components as those in FIGS. 1 to 3 and FIG. 8 are denoted by the same reference numerals. In FIG. 4, a snubber circuit including a snubber diode 12, a snubber capacitor 13, and a snubber resistor 14 is connected in parallel to the switching element 9, and an anode reactor 15 is connected in series to the switching element 9.

  The operation of the power converter of the fourth embodiment having the above configuration will be described. The action of suppressing the turn-on loss of the switching element 9 by the anode reactor 15 and the action of suppressing the loss at the turn-off of the switching element 9 by the snubber diode 12 and the snubber capacitor 13 are almost the same as those of the previous embodiments. . However, the processing of the energy accumulated in the anode reactor 15 is different. In the case of the present embodiment, when the switching element 9 is turned off, the snubber capacitor 13 is charged by the commutated main current, and the overcharged state is assumed. Thus, when a positive voltage is applied to the anode reactor 15 and a negative voltage is applied to the anode reactor 15, the energy of the anode reactor 15 is transferred to the snubber capacitor 13.

  According to the present embodiment, the turn-on loss and the turn-off loss of the switching element 9 are increased by simultaneously suppressing the voltage rise rate and the current rise rate by the snubber circuit while providing the surge voltage suppression function by the active gate circuit 11. Can also be suppressed.

  (Fifth Embodiment) In the first to fourth embodiments, the energy stored in the snubber circuit is consumed by the snubber resistor 14 in synchronization with the switching of the switching element 9. In most cases, this is sufficient, but it is desirable to regenerate the power converter power source without consuming the snubber energy at the snubber resistor 14 in order to improve the efficiency of the power converter and simplify the cooling. The power converter according to the fifth embodiment of the present invention is characterized in that the snubber energy is regenerated to the power source of the power converter without being consumed by the resistor.

  FIG. 5 is a circuit diagram of a power converter according to a fifth embodiment of the present invention. In FIG. 5, the same or equivalent components as those in FIGS. 1 to 4 and 8 are denoted by the same reference numerals. In FIG. 5, a regenerative diode 16 is connected to a connection point between the snubber capacitor 13 and the snubber diode 12, and a regenerative capacitor 17 is connected between the other end of the regenerative diode 16 and one terminal of the DC main power supply 19 of the power converter. The input terminal of the regenerative converter 18 is connected in parallel with the regenerative capacitor 17, and the output terminal of the regenerative converter 18 is connected to both ends of the DC main power supply 19 of the power converter.

  The operation of the power converter of the fifth embodiment having the above configuration will be described. The charge stored in the snubber capacitor 13 at the timing when the switching element 9 is turned on flows out through the regenerative diode 16 in the direction of charging the regenerative capacitor 17. As a result, the energy stored in the snubber capacitor 13 is transferred to the regenerative capacitor 17. The regenerative converter 18 connected to both ends of the regenerative capacitor 17 regenerates energy to the DC main power supply 19 until the voltage of the regenerative capacitor 17 becomes almost zero. If the capacitance of the regenerative capacitor 17 is sufficiently larger than that of the snubber capacitor 13, the voltage of the regenerative capacitor 17 is always kept sufficiently smaller than the main voltage applied to the switching element 9. . Therefore, when the switching element 9 is turned on, the voltage of the snubber capacitor 13 is discharged to a sufficiently small voltage that is substantially the same as the voltage of the regenerative capacitor 17.

  According to the present embodiment, while the surge voltage suppression function by the active gate circuit 11 is provided, the increase in turn-off loss of the switching element 9 is also suppressed by simultaneously suppressing the voltage increase rate by the snubber circuit, and the snubber energy is reduced. It is possible to regenerate the DC main power supply 19 to improve the device efficiency.

  (Sixth Embodiment) In the fifth embodiment, the snubber energy is regenerated to the DC main power supply 19 by the regenerative converter 18, but the snubber energy can be used as the power supply for the gate circuit 11. . The sixth embodiment of the present invention is characterized in that snubber energy is used as a power source for an active gate circuit.

  FIG. 6 is a circuit diagram of a power converter according to a sixth embodiment of the present invention. In FIG. 6, the same or equivalent elements as those in FIGS. 1 to 5 and FIG. 8 are denoted by the same reference numerals. In FIG. 6, the output of the regenerative converter 18 is connected to the power supply terminal of the active gate circuit 11, and the power consumed by the active gate circuit 11 is supplied from the regenerative converter 18.

  This embodiment is particularly suitable for applications in which a large number of switching elements 9 are connected in series. The reason is as follows. The active gate circuit 11 is set to the same potential as the switching elements 9 to be driven. However, when a large number of switching elements 9 are connected in series, the potentials of the switching elements 9 are different. The power of each active gate circuit 11 must be supplied in an insulated form, and for that purpose, power is conventionally supplied to the active gate circuit 11 via a number of isolation transformers. Yes. In contrast, in the present embodiment, the regenerative converter 18 that supplies power from the snubber energy to each active gate circuit 11 is provided, so that a large isolation transformer having a higher withstand voltage than the low potential portion is not used. Thus, it is possible to supply power to the active gate circuit 11 with only a small regenerative converter 18 having a withstand voltage equivalent to one switching element, and the circuit configuration can be simplified and miniaturized.

  According to the present embodiment, while the surge voltage suppression function by the active gate circuit 11 is provided, an increase in switching loss of the switching element 9 is also suppressed by the snubber circuit, and the snubber energy is used as a power source for the active gate circuit 11. By using it, it is possible to omit an insulation transformer that was conventionally required.

  (Seventh Embodiment) In the first to sixth embodiments, the switching element 9 constitutes one arm, but the collector-emitter of the switching element 9 is driven by active gate driving. Since the voltage can be suppressed, it is possible to easily configure one arm by connecting a plurality of switching elements 9 in series. The seventh embodiment of the present invention is characterized in that a plurality of switching elements 9 are connected in series to constitute one arm.

  FIG. 7 is a circuit diagram of a power converter according to a seventh embodiment of the present invention. In FIG. 7, the same or equivalent elements as those in FIGS. 1 to 6 and FIG. 8 are denoted by the same reference numerals. In FIG. 7, a snubber diode 12 and a snubber capacitor 13 are connected to the switching elements 9 connected in series. The regenerative diode 16 is also connected in series, and a regenerative capacitor 17 is connected to the cathode terminal of the uppermost regenerative diode 16.

  The operation of the power converter of the seventh embodiment having the above configuration will be described. When all of the switching elements 9 connected in series are turned on, the collector-emitter voltage of each element becomes substantially zero. At this time, the potentials of the positive side electrodes of the snubber capacitors 13 are all substantially equal, and the uppermost stage It becomes a potential higher than the collector potential of the switching element 9 by a voltage corresponding to one switching element. Therefore, all the regenerative diodes 16 connected in series are conducted, and the voltages of all the snubber capacitors 13 are applied to the anode reactor 15 and the regenerative capacitor 17. As a result, the electric charge of each snubber capacitor 13 flows into the regenerative capacitor 17 via the anode reactor 15 and each switching element 9, and finally everything is transferred to the regenerative capacitor 17. An input terminal of a regenerative converter 18 is connected to both ends of the regenerative capacitor 17, and energy stored in the regenerative capacitor 17 is regenerated to the DC main power supply 19 by the regenerative converter 18. By adopting such a configuration, it is not necessary to provide the regenerative converter 18 for each switching element 9, and the regenerative circuit can be simply configured.

  According to the present embodiment, the snubber circuit suppresses an increase in switching loss of the switching element 9 while having the function of suppressing the surge voltage by the active gate circuit 11, and the snubber circuit of each switching element 9 connected in series. Can be regenerated to the DC main power supply 19 by a simple regenerative circuit.

The circuit diagram of the power converter of the 1st Embodiment of this invention. The circuit diagram of the power converter of the 2nd Embodiment of this invention. The circuit diagram of the power converter of the 3rd Embodiment of this invention. The circuit diagram of the power converter of the 4th Embodiment of this invention. The circuit diagram of the power converter of the 5th Embodiment of this invention. The circuit diagram of the power converter of the 6th Embodiment of this invention. The circuit diagram of the power converter of the 7th Embodiment of this invention. The circuit diagram of the proposed power converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Gate power supply 2, 5 Voltage amplifier 3 Gate resistance 4a, 4b Voltage dividing resistance 6 Control current source 7 Capacitor 8 Diode 9 Power switching element 10 Flywheel diode 11 Active gate circuit 12 Snubber diode 13 Snubber capacitor 14 Snubber resistance 15 Anode reactor 16 Regenerative diode 17 Regenerative capacitor 18 Regenerative converter 19 DC main power supply

Claims (10)

A non-latching switching element having two main electrodes and one control electrode;
A snubber circuit for suppressing the voltage rise rate of the switching element;
Voltage detection means for detecting a voltage applied between the main electrodes of the switching element;
A power converter comprising: control means for controlling a voltage applied to the control electrode or a current flowing through the control electrode in accordance with a voltage detected by the voltage detection means. A non-latching switching element having two main electrodes and one control electrode;
A snubber circuit for suppressing a current rise rate of the switching element;
Voltage detection means for detecting a voltage applied between the main electrodes of the switching element;
A power converter comprising: control means for controlling a voltage applied to the control electrode or a current flowing through the control electrode in accordance with a voltage detected by the voltage detection means. A non-latching switching element having two main electrodes and one control electrode;
A first snubber circuit for suppressing a voltage rise rate of the switching element;
A second snubber circuit for suppressing a current rise rate of the switching element;
Voltage detection means for detecting a voltage applied between the main electrodes of the switching element;
A power converter comprising: control means for controlling a voltage applied to the control electrode or a current flowing through the control electrode in accordance with a voltage detected by the voltage detection means.   The power converter according to any one of claims 1 to 3, wherein the energy stored in the snubber circuit is consumed by a snubber resistor.   The power converter according to any one of claims 1 to 3, further comprising regenerative means for regenerating energy stored in the snubber circuit in a DC main circuit of the power converter.   The power converter according to any one of claims 1 to 3, wherein the energy stored in the snubber circuit is used as a power source for driving the gate of the switching element.   The power converter according to claim 1 or 3, wherein a circuit in which a diode and a capacitor are connected in series is connected in parallel to the switching element as a snubber circuit for suppressing a voltage increase rate of the switching element.   4. The power converter according to claim 2, wherein an inductance is connected in series to the switching element as a snubber circuit for suppressing a current increase rate of the switching element. 5.   The power converter according to any one of claims 1 to 8, wherein two or more switching elements are connected in series to constitute one arm. The energy stored in the snubber circuit connected to the two or more switching elements connected in series is collected in one capacitor each time the switching element is switched, and then the DC main circuit of the power converter The power converter according to claim 9, further comprising regenerative means for regenerating the power.

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