JP2000232771A - Power-converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power loss, size, and cost of the clamped snubber circuit of a DC AC power-converting device used for DC transmission or the like. SOLUTION: One arm is composed by a switch group, where semiconductor switching elements 2 with a self-arc-extinguishing function, are connected in series, at least two arms are combined for composing a high-voltage power- converting device, and a snubber circuit 10 is provided at both the ends of the semiconductor switching elements 2 in a power-conversion device. In this case, in the snubber circuit 10, a series circuit consisting of a clamp diode 4 and a clamp capacitor 5 is connected at both the ends of the semiconductor switching elements 12, and a nonlinear circuit is connected to both the ends of the clamp capacitor 5. The nonlinear circuit is composed by a nonlinear resistance element or a nonlinear resistance circuit where the nonlinear resistance element and a semiconductor control element 19 are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of a power converter used for AC / DC conversion or DC / AC conversion in a power system or the like.

[0002]

2. Description of the Related Art FIGS.
FIG. 4 shows an example of a power converter shown in Japanese Patent Application Publication No. 4 (JP-A) No. 4 (1993) -204, and shows a configuration per stage when switching elements are connected in series. In the figure, 100 is a switching element, 102 is a clamp diode, 103 is a clamp capacitor, 105 is a gate control circuit, 108 is an optical fiber, 109 is a discharge resistor, 110 is a discharge control circuit,
111 is a discharge switching element. Next, the operation will be described. It is generally known that when the stages having the configuration shown in the figure are connected in series, an overvoltage occurs at both ends of the switching element 1 due to the following two causes.
One is due to variations in the turn-on or turn-off times of a large number of switching elements 1 connected in series. For example, an overvoltage is applied to an element that turns on slowly when the turn-on is performed and an element that turns off quickly when the turn-off is performed. You. The second is due to the surge energy of the inductance of the circuit, and mainly at the time of turn-off, an overvoltage is commonly applied to all stages by the back electromotive force of the inductance. In the configuration shown in FIG. 22, the clamp diode 102, the clamp capacitor 103, the discharge resistor 109, the discharge control circuit 110, and the discharge switching element 111 form a clamp-type snubber circuit, and the operation will be described below. When the above-mentioned overvoltage occurs,
The voltage flows into the clamp capacitor 103 to prevent a rise in the voltage applied to both ends of the switching element.
The charge flowing into the clamp capacitor 103 is prevented from flowing backward by the clamp diode 2. At this time, the voltage of the clamp capacitor 103 temporarily increases. The charge of the clamp capacitor 103 is discharged through a discharge resistor 109 by a discharge switching element 111 that is switched by a signal output from a discharge control circuit 110. Thus, the voltage of the clamp capacitor 103 is reduced to a certain value.
If this constant value is matched in each series stage, an excessive voltage will not be applied to the switching element 1 even if surge energy flows. An advantage of such a clamp-type snubber circuit (Japanese Patent Publication No. 7-83617) is that only the inflowing surge energy is consumed as a loss, so that there is no waste. In the CRD snubber circuit as shown in FIG.
It is widely known that there is a problem that the efficiency of the device cannot be increased because the loss of charging / discharging to a value obtained by dividing the total applied DC voltage by the number of series is added to the surge energy and consumed by the discharge resistor 109. .

[0003]

In the prior art, the discharge switching element 111 is used to discharge the clamp capacitor 103, so that the discharge control circuit 110 becomes complicated. That is, since the voltage of the clamp capacitor 103 must be discharged until it reaches a certain voltage value, a circuit for detecting the value and a voltage comparison circuit are required. In addition, a stabilized power supply circuit for operating such a circuit is required. Further, since the gate voltage of the discharge switching element 111 needs to change a value corresponding to turning on / off, the driving power increases and the capacity of the stabilized power supply circuit also increases. In the case where an active circuit such as a voltage comparison circuit is provided, there is a problem that noise generated by switching or the like is easy to ride, and the reliability may be reduced.

The present invention has been made to solve the above-mentioned problems, and has as its object to simplify the configuration of a clamp-type snubber circuit and to reduce the size and stabilize it.

[0005]

According to a first aspect of the present invention, there is provided a power conversion device, wherein one arm is constituted by a group of switches in which semiconductor switching elements having a self-extinguishing function are connected in series, and the arm is composed of at least two switches. A high-voltage power converter is configured by combining the two or more, and a snubber circuit is provided at both ends of the semiconductor switching element, wherein the snubber circuit includes a series connection of a clamp diode and a clamp capacitor at both ends of the semiconductor switching element. A circuit is connected, and a non-linear circuit is connected in parallel to both ends of the clamp capacitor. The non-linear circuit comprises a non-linear resistance element or a non-linear resistance circuit using a non-linear resistance element and a semiconductor control element.

According to a second aspect of the present invention, in the power conversion device according to the first aspect, the nonlinear circuit includes:
It is connected to both ends of the semiconductor switching element via an impedance element.

According to a third aspect of the present invention, in the power conversion device according to the first or second aspect, the non-linear resistance element includes a zener diode, an arrester, or a varistor.

According to a fourth aspect of the present invention, in the power conversion device according to the first or second aspect, the non-linear resistance circuit using the semiconductor control element includes a semiconductor control element having a control electrode for discharging; A non-linear resistance element connected in parallel between the first main electrode on the high voltage side and the control electrode of the semiconductor element for discharge, and between the control electrode and the second main electrode on the low voltage side of the semiconductor element for discharge; And a resistor that is connected in parallel.

According to a fifth aspect of the present invention, in the power conversion device according to the fourth aspect, a capacitor is provided between a connection point between the clamp capacitor and the impedance element and a control electrode of the discharge semiconductor control element. Connected.

According to a sixth aspect of the present invention, in the power converter according to the first or second aspect, the nonlinear resistance circuit is configured by using at least two or more semiconductor control elements connected in series. Things.

In a power converter according to a seventh aspect of the present invention, in the configuration according to the first or second aspect, the non-linear circuit using the semiconductor control element includes a semiconductor control element with a control electrode for discharging and the semiconductor control element. A series body of the first impedance and the second impedance connected in parallel between the first main electrode on the high voltage side and the second main electrode on the low voltage side of the control element, and a series connection point of the series body and the A non-linear resistance element having a threshold voltage characteristic is connected to a control electrode of a semiconductor control element.

In a power converter according to an eighth aspect of the present invention, in the configuration according to the seventh aspect, the two impedance elements each include a parallel circuit of a first resistor and a first capacitor, and a second resistor. It consists of a parallel circuit with a second capacitor, and has the same CR time constant.

According to a ninth aspect of the present invention, in the power conversion apparatus according to the ninth aspect, the two impedance elements each include a parallel circuit of a first resistor and a first capacitor, and a second resistor. It is composed of a parallel circuit with a second capacitor. The CR time constant of the first resistor and the first capacitor is reduced by the CR of the second resistor and the second capacitor.
The impedance is made larger than a time constant, and an impedance composed of the first resistor and the first capacitor is connected to the first main electrode side of the semiconductor control element.

According to a tenth aspect of the present invention, in the power converter, one arm is formed by a switch group in which semiconductor switching elements having a self-extinguishing function are connected in series, and at least two or more of the arms are combined to achieve a high power conversion device. In a power converter comprising a voltage power converter and a snubber circuit provided at both ends of the semiconductor switching element, the snubber circuit connects a series circuit of a clamp diode and a clamp capacitor between main electrodes of the semiconductor switching element. A discharge switch at both ends of the clamp diode, a series circuit of a constant voltage element such as a zener diode and an impedance element connected to both ends of the clamp capacitor, and a series connection point of the impedance element and the constant voltage element. Semiconductor switching element having the self-extinguishing function Connected to the control electrode of which are connected to the gate drive circuit through a current control element the control electrode.

According to a eleventh aspect of the present invention, in the power converter according to the tenth aspect, a gate speed-up switch is provided at both ends of the current limiting element.

According to a twelfth aspect of the present invention, there is provided a power conversion apparatus comprising a switch group in which semiconductor switching elements having a self-extinguishing function are connected in series as one arm, and combining at least two or more arms to provide a high voltage. In a power converter that constitutes an AC / DC converter and performs DC power transmission using at least the AC / DC converter on the power receiving side, snubber circuits are provided at both ends of the semiconductor switching elements, and the snubber circuit is connected to both ends of the semiconductor. Is connected to a series circuit of a clamp diode and a clamp capacitor, and both ends of the clamp capacitor are each formed of a non-linear resistance circuit using a non-linear resistance element or a semiconductor control element, and power is supplied to the power transmission side of the power conversion device. During the period when the DC voltage of the transmission line rises, the power conversion device on the power receiving side It is intended to several times switching.

According to a thirteenth aspect of the present invention, in the power conversion device according to the twelfth aspect, when the power is supplied to the power transmission side of the power conversion device during a period in which the DC voltage on the power transmission side increases. The power conversion device on the power receiving side is configured to alternately switch between the high voltage side arm groups and the low voltage side arm groups.

According to a fourteenth aspect of the present invention, in the power conversion apparatus according to the twelfth aspect, when the power on the power transmission side is turned on, the power conversion apparatus on the power reception side is connected to an inductance component of the power conversion apparatus. And the capacitor is repeatedly conducted for a time shorter than half the resonance cycle of the capacitor.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram showing a basic configuration of a power conversion device for switching from AC to DC or from DC to AC in a power system or the like. Reference numerals 1a to 1f denote series valves each having a plurality of semiconductor switching elements connected in series. Each of the series valves 1a to 1f is referred to herein as an arm. FIG.
Connects the internal circuits of the series valves 1a to 1f
Only the steps are shown.

2 is a GCT (Gate Commutate).
d Thyrister), and 3 is a diode. GTO, IGBT, SIT, FE besides GCT
Semiconductor switching elements having a self-extinguishing function, such as T and bipolar transistors, can also be used. When power is supplied from the AC side to the DC side, each series valve mainly functions as a rectifying element through the diode 3 to constitute a three-phase rectifier as a whole. To obtain a DC voltage higher than the AC voltage, for example, when the V-W voltage is positive, 1
The GCT of the b-valve is made conductive and the diode of 1a and 1b
And the GCT, a short circuit is configured to store electromagnetic energy in an inductance (not shown) of the AC side, and then released to transmit power to the DC side in a manner that the electromagnetic energy is superimposed on the AC voltage. With such an operation, a step-up rectifier can be realized. These operations have been widely known. Next, D
When converting from C to AC, roughly, the conduction phase is shifted by 180 ° C. between the vertical connections of each series valve, and the respective valves connected to V, W, and U are shifted by 120 ° in phase. By driving, three-phase AC power can be supplied to the AC side. At this time, by changing the duty of the conduction time width, AC
Power to the side can be controlled. recently,
For harmonic countermeasures, there is also a type in which the PWM operation is further performed by switching within the conduction time of one valve to make the voltage waveform of the converter supplied to the AC side closer to a sine wave as much as possible. is there.

Such a power converter is effective, for example, in the case where power is exchanged bidirectionally in a DC power transmission system or the like. However, since the voltage is generally several tens of kV, the series valve 1 is not shown in FIG. As shown in (1), the voltage is increased by connecting a number of elements in series. FIG. 3 is a diagram including the snubber circuit according to the first embodiment of the present invention. In FIG. 3, reference numeral 11 denotes a series stage which is a unit of series connection, reference numeral 10 denotes a clamp type snubber circuit, reference numeral 12 denotes a driving gate circuit, reference numeral 4 denotes a snubber diode, reference numeral 5 denotes a clamp capacitor, and reference numeral 6 denotes an impedance element such as a resistor. Zener diode which is a non-linear resistance element, 8 is a resistor, 9 is an IGBT
And 13 is a signal input such as an optical fiber. The semiconductor control element 9 is IG
Although a BT is shown as an example, the same effect can be obtained if the current can be controlled by a voltage to a control terminal such as a bipolar transistor or an FET. 14 is a series valve 1
This is the inductance that exists in series each time. The zener diode 7 is connected between a main electrode (drain, collector, etc.) on the high voltage side (in the case of an N-type semiconductor element) of the semiconductor control element 9 and a control electrode (gate, base, etc.), and the resistor 8 has a low voltage. It is connected between the side main electrode (source, emitter, etc.) and the control electrode. The semiconductor control element 9 operates as an analog amplifier, amplifies and transmits the voltage-current characteristics of the zener diode 7 between the output-side main electrodes, and enables output of a large current. Further, by connecting the impedance elements 6 in series, there is an advantage that the discharge start voltage and the voltage-current slope can be set arbitrarily. Further, since the output terminal of the discharge current is one end of the zener diode for detecting the voltage, there is an advantage that the clamp capacitor is never excessively discharged below the zener voltage. This guarantees that power efficiency does not decrease due to useless charging and discharging.

FIGS. 4 and 5 show the configuration per stage and the operation of the clamp circuit. Reference numeral 15 denotes an inductance replaced per stage of an n-stage series valve. In particular, at the time of turn-off, the charge corresponding to the power flowing in due to the turn-off shift and the surge energy of the inductance 15 flows into Cs. It rises due to this charge. The voltage ΔV is as follows.

[0023]

(Equation 1)

(Here, τ is the time lag between the serial stages, Io is the current when off) The charge Q flowing into the clamp capacitor Cs is as follows: Q = ΔVCs (2) Therefore, the value of the charging voltage Vs of the clamp capacitor 5 becomes steady by discharging the charge Q before the time when the Q flows again. Control element 9
Is connected through a zener diode having the value of the zener voltage Vz. When both ends of the control element 9 exceed Vz, a current flows through the zener diode 7 and a voltage is generated in the resistor 8 so that the current flows through the control element 9. Flows. With such a configuration, since Vz is amplified in an analog manner at both ends of the control element 9, the control element 9 always stays near Vz.
As a result, as shown in FIG. 5, the operation region between Vs and is indicated by an arrow in the figure, and the off-state voltage Vo for one stage
When the voltage rises by ΔV due to the electric charge Q, a voltage of Vo + ΔV / 2−Vz is applied to both ends of the impedance element 6 on average. As described above, by using the analog voltage amplifier including the zener diode 7 and the IGBT in the discharge circuit of the Cs charge, a voltage clamp element having a large capacity is generally formed using a zener diode having a small power capacity. it can. In the figure, Vz is selected to be smaller than Vo, but this advantage is as follows. First, under the condition that the electric charge Q does not flow at all or the condition is small, the current flows through the resistor 6 by the voltage of Vo−Vz, so that the off-state impedance of one stage is reduced and the off-state voltage division in the valve is equalized. Help. In addition, for example, Vo is generally selected to be 2 kV or more.
High voltage zener diodes are expensive. If Vz is made smaller than Vo, the range of selection of the zener diode 7 is widened. The second disadvantage is that a loss always occurs between the resistor 6 and the control element 9 even when Q does not flow in or when Q is small. To avoid this loss, Vz should be Vo
Or set slightly higher than Vo. By doing so, wasteful loss does not occur even if the value of the impedance element 6 is made sufficiently small, so that more charges can be released and even when Q is large, it is possible to cope with the case.

By such an operation, the destruction of the switching element 2 can be reliably suppressed while minimizing useless loss as much as possible, so that the reliability of the device is reliably improved.

In the description of FIGS. 4 and 5, the total voltage Vz by the zener diode 7 is analogously amplified by the control element 9. However, instead of the zener diode, a constant voltage semiconductor such as an arrester or a varistor (non-linear) is used. The same effect can be obtained with the element.

Embodiment 2 As shown in FIG. 6, the same effect can be obtained by directly connecting a non-linear resistance element 90 such as a large-capacity zener diode, arrester or varistor without using the semiconductor control element 9.

Embodiment 3 If the withstand voltage of the control element 9 is not sufficiently high, FIG.
(A) As shown in FIG.
It may be configured in a stage series. By doing so,
Since the breakdown voltage of the IGBT is the sum of the breakdown voltages of the IGBTs 9a and 9b, a sufficiently high breakdown voltage can be obtained. Further, as shown in FIG. 7B, a portion including the clamp capacitor 5 and the impedance element 6 may be connected in two stages in series. As a result, a low withstand voltage clamp capacitor can be used, and cost can be reduced.

With such a configuration, any of the low-voltage, inexpensive elements can be provided with a reliable clamping function, and the switching element 2 can be prevented from being damaged by voltage.

Embodiment 4 Next, Embodiment 4 of the present invention will be described. The inflow charge Q of the clamp capacitor 5 already described becomes very large when Io jumps up due to, for example, a short-circuit current at the time of an accident. Needs to increase the capacitance of the clamp capacitor 5. However, this leads to an increase in the size of the device. Therefore, a capacitor that transiently shares a part of the function of the clamp capacitor 5 is required. FIGS. 8 and 9 show a configuration that can cope with this, in which the function of the clamp capacitor 5 is shared by the semiconductor control element 9. Generally, elements such as IGBTs are
It is known that a considerably large current can flow instantaneously. For example, if Vz is set equal to or higher than Vo and the impedance element 6 is set smaller, a sufficient current can flow even transiently. However, most of the transient loss at this time is lost by the control element 9,
The internal temperature rises transiently. Therefore, there is a concern that the control element 9 may be broken due to a problem such as solder fatigue. Therefore, it is necessary to pay attention to the fact that a sudden loss is usually caused in a semiconductor. FIGS. 8 and 9 solve the problem, and provide a path directly connected from one side of the clamp capacitor 5 to the control element 9 by the capacitor 22 (Cp). The operation will be described. It is easy to understand that almost Vo is also applied to Cp22 immediately before the turn-off. When the charge of Q flows into the snubber circuit by turning off the semiconductor switching element 2, a part of Q is diverted to Cp22. As a result, a voltage of Io * Cp / Cs * Rg (Rg is the resistance value of the gate resistor 8) is applied to the control terminal of the control element 9. As a result, the voltage of the control element 9 decreases rapidly (V in FIG. 9B).
9) A large voltage is applied to the resistor 6. Thereby,
A large current flows through the resistor 6 and can handle a part of Q. Thereby, the charge flowing into the clamp capacitor 5 is suppressed, and the voltage rise of the clamp capacitor 5 is suppressed. As a result, even with a small clamp capacitor 5,
V is suppressed. In this case, the gate voltage of the control element 9 increases as Q increases (Io increases).
As Io is larger, a larger current flows through the impedance element 6, and the voltage of the control element 9 is naturally smaller. as a result,
The loss sharing in the transient state between the control element 9 and the resistor 6 changes, and the larger the Io, the smaller the loss sharing in the control element 9. As a result, the transient loss of the control element 9 is suppressed to a certain amount, and solder fatigue and the like hardly occur.

With such a configuration, a large current transiently flows through the impedance element 6 and the clamp capacitor 5
Is suppressed, the value of the clamp capacitor 5 can be set small, and cost reduction and size reduction can be realized. Further, the reliability of the control element 9 is also improved.

Fifth Embodiment In the above-described embodiments, a high voltage zener diode 7 is required. However, high voltage zener diodes are generally expensive. Embodiment 5 of the present invention solves this problem.
(A) and (b). In FIG. 10A, the voltage divided by the voltage dividing resistors 16a and 16b is input to the low voltage zener 70 and guided to the gate of the control element 9. Since the zener voltage is selected to be sufficiently higher than the threshold value of the control element 9, when the voltage of Vg exceeds the zena voltage, I
A current flows through the GBT 8. That is, when the voltage of Vd is V
When the size of z * (R1 + R2) / R2 is reached, the control element 9
Current will flow through the Therefore, Vd is always Vz *
It is clamped to the size of (R1 + R2) / R2, and has the same effect as the previous embodiment in which a high-voltage zener diode is inserted.

With such a configuration, it is not necessary to use an expensive high-voltage zener diode, so that the cost of the entire apparatus can be greatly reduced.

FIG. 10B shows an example in which a parallel circuit of a capacitor and a resistor is used as a voltage divider. As shown in the figure, it is generally well known that, by matching the time constants connected in parallel, an excellent voltage dividing performance is exhibited in all frequency ranges. That is, C1R1 = C2R
If it is 2, Vg = Vd * R2 / (R1 + R2). With such a configuration, the cost of the entire apparatus can be significantly reduced as in the case of a, and the voltage divider exhibits excellent characteristics in all frequency ranges, so that the reliability is improved.

Sixth Embodiment Next, a sixth embodiment of the present invention will be described. The purpose is the same as in the fourth embodiment. The Q already described is
For example, when Io jumps up due to a short-circuit current or the like at the time of an accident, it becomes very large. Therefore, in order to suppress ΔV to be small and to prevent the switching element 2 from being broken, it is necessary to increase the capacitance of the clamp capacitor 5. However, this leads to an increase in the size of the device. Therefore, a capacitor that transiently shares a part of the function of the clamp capacitor 5 is required. FIGS. 11 and 12 show a configuration that can cope with this. Generally, it is known that an element such as an IGBT can instantaneously flow a considerably large current. For example, V
If z is set equal to or higher than Vo and the impedance element 6 is set smaller, a sufficient current can flow even transiently. However, most of the transient loss at this time is lost by the control element 9, so that the internal temperature rises transiently. Therefore, there is a concern that the control element 9 may be broken due to a problem such as solder fatigue. Therefore, it is necessary to pay attention to the fact that a sudden loss is usually caused in a semiconductor. FIG. 11 solves the problem. The voltage divider is selected so that C1R1> C2R2, and by selecting C1 / C2> R2 / R1, the control terminal voltage V of the semiconductor control element 9 in the steady state.
g = Vd * R2 / (R1 + R2). Transiently, Vg = Vd * C1 / (C1 + C2). As a result, in the steady state, both ends of the control element 9 are at Vz
It is clamped at * (R1 + R2) / R2 and in the transient state is clamped at Vz * (C1 + C2) / C1. As a result, as shown in the figure, in the transient state, a large current flows through the impedance element 6, and a part of Q is diverted to the impedance element 6, so that the voltage rise of the clamp capacitor 5 is suppressed and the capacitance value is selected to be small. it can. Further, since the voltage of the control element 9 is reduced to Vz * (C1 + C2) / C1, the transient loss is reduced and solder fatigue and the like hardly occur.

With such a configuration, a large current transiently flows through the impedance element 6 and the clamp capacitor 5
Is suppressed, the value of the clamp capacitor 5 can be set small, and cost reduction and size reduction can be realized. Further, the reliability of the control element 9 is also improved.

Embodiment 7 Next, a seventh embodiment will be described. An object of the present embodiment is to discharge the charge stored in the clamp capacitor 5 without using the control element 9 described above. The installation of the control element 9 requires a new area, which results in an increase in size and an increase in cost. FIGS. 13 and 14 show an embodiment for solving this, in which a reverse discharge switch 19 (SWA) is inserted in parallel with the clamp diode. Further, a gate impedance element 20, which is a current control element, is connected to an outlet from the gate circuit. Further, a voltage control type IGBT 2 a is connected to the semiconductor switching element 2. As shown in FIGS. 13 and 14, in the off state, the reverse discharge switch 19 is controlled to be in a conductive state. When the voltage of the clamp capacitor 5 increases and the current of the zener diode 7 increases, the voltage across the resistor 18 increases. Thereby, since both ends of the resistor 18 are connected between the gate and the source of the IGBT 2a, the IGBT 2a tries to flow a current. Thereby,
The charge of the clamp capacitor 5 is supplied to the reverse discharge switch 19,
It discharges through the IGBT 2a. The meaning of the current limiting element 20 composed of a resistor or the like will be described. Current limiting element 20
If there is no voltage, the voltage of Vgate is zero when the IGBT 2a is in the off state, so that no voltage is applied to the gate of the IGBT 2a even if a voltage is generated across the resistor 18.
This is because the current flowing through the zener diode 7 flows back to the gate circuit. The resistance current limiting element 20 suppresses the backflow so that a predetermined voltage is generated in the resistor 18. If the current limiting element 20 is selected to be at least not less than the value of the resistor 18, most of the voltage generated across the resistor 18 is transmitted to Vgate, so that the above-described operation can be realized. However, since the resistor is connected to the output side of the gate circuit, the rising and falling waveforms of the gate voltage naturally become gentle.

With such a configuration, the semiconductor control element 9 used up to the sixth embodiment becomes unnecessary, so that the device can be reduced in size and the cost can be greatly reduced. In addition, the current of the reverse current discharge switch 19 newly provided this time is extremely small, and almost no loss occurs.
It does not add to the size or cost.

Eighth Embodiment FIGS. 15 and 16 illustrate an eighth embodiment. In the eighth embodiment, a new gate speed-up switch 21 is provided, and the gate voltage Vgat of the semiconductor switching element is provided.
Control is performed such that the SWB 21 is in the conductive state during the time when e is H. This configuration solves the problem of the seventh embodiment, that is, the voltage of Vgate becomes gentle. Thereby, the turn-on and turn-off speeds of the IGBT 2a are increased, and the switching loss is reduced. While Vgate is H, the gate speed-up switch 21 is conducting, so that Vgate
A voltage is sharply applied to gate. On the other hand, IGBT
In the off state of 2a, since the gate speed-up switch 21 is off, the current flowing through the zener diode 7 is prevented from flowing backward by the current limiting element 20, so that Vgate is stably maintained.
Is applied.

With such a configuration, the IG
The speed of rise and fall of the gate of the BT 2a is increased, the switching loss is reduced, and the control element 9 required up to the ninth embodiment is not required. realizable.

Ninth Embodiment Next, a ninth embodiment will be described. Embodiments 9-1
1 is AC-DC and DC-A on the power transmission side and the power reception side, respectively.
The present invention relates to an initial operation of a power converter in a system for transmitting power by connecting a C converter. FIG.
7, 18 and 19 explain the ninth embodiment. FIG. 17 is a diagram showing the configuration of the entire system, FIG. 18 is a diagram showing the internal configuration of the switching arms S1 to S8 in FIG. 17, and FIG. FIG. In the figures, the same numbers have the same meanings as described above. In the figure, D is a connection of two single-phase power converters.
C shows a power transmission system, 50 is an AC power supply on the power transmission side, 40 is a closing switch SWX, 41 is a power supply side power inductance, 31 is a power transmission side DC capacitor, 32 is a transmission line inductance component, and 30 is a power reception side DC. The capacitor 33 is an inductance component of the power receiving side converter, 51
Is an inductance component of the power transmission side converter. Each of the inductance components 33 and 51 is shown as a value equivalently including what each arm has. Each arm typically has two series semiconductor switching elements (GC
T). Further, the snubber circuit is used in the first embodiment.
Is representatively shown, but similar effects can be obtained with other configurations. Further, the power converter may have three phases, and the same effect can be obtained with a three-level system.

Problems with the clamp type snubber circuit include the following. As described above, the clamp-type snubber circuit consumes only the inflow of the electric charge Q during the idle period, so that unnecessary power loss is small, and therefore, it is easy to set the clamp capacitor 5 large. .
However, when the clamp capacitor 5 is set large,
For example, at the start of the converter, the voltage of the clamp capacitor is zero, so the charging current of the snubber capacitor flows with the conduction of each arm, which can cause the voltage of the clamp capacitor to jump up and destroy the GCT. There is. For example, when the power receiving-side conversion device starts operating after Vdc is charged to a predetermined value, for example, S
When 5 conducts, a charging current flows through the clamp circuit of S8,
The voltage of the clamp capacitor 5 increases up to 2 * Vdc due to resonance with the inductance 33. If this voltage exceeds the withstand voltage of the GCT, the GCT naturally breaks down. Further, since the current flowing at this time is excessive, there is a possibility that noise is generated or the GCT is destroyed. Therefore, one of the issues in the clamp type snubber circuit is how to stably bring the voltage of the clamp capacitor 5 to a steady value. This embodiment solves this problem. For example, when the power transmission-side switch 40 is turned on at time to, A on the left side of the drawing that functions as a rectifier circuit is used.
The C-DC converter gradually starts charging the transmission line with a DC voltage. At this time, the rising speed of the DC capacitor 30 at the power receiving end depends on the inductance 32 of the transmission line, the inductance 51 of the power transmitting converter, and the AC inductance 4 of the power transmitting side.
1, etc., and are determined by the DC capacitor on the power transmission / reception side.
As shown in FIG. 19, the conversion device on the power receiving side
Control is performed at a high frequency so that the conversion operation is performed a plurality of times while the voltage of the capacitor rises. By such an operation, the clamp capacitor 5 of the power receiving side converter is
Is charged a plurality of times. This prevents the voltage of the clamp capacitor 5 from jumping excessively. By shifting to a normal conversion frequency operation when the power receiving side DC capacitor voltage has reached a predetermined value, an AC voltage having a predetermined frequency can be supplied to a customer.

With such a configuration, it is possible to suppress the voltage of the clamp capacitor 5 from jumping when the power transmission side is turned on, and to improve the reliability of the GCT element.
Thereby, the stability and reliability of the DC power transmission system are greatly improved.

In the ninth embodiment, the voltage of the clamp capacitor is quasi-statically increased by performing the conversion operation with the frequency increased. However, for example, the frequency is fixed and the high frequency PWM is performed. Has the same effect, but it goes without saying that it does not make sense if the rise of the power receiving DC capacitor approaches the conversion frequency.

Tenth Embodiment Next, a tenth embodiment will be described. In the ninth embodiment, when the voltage of the DC capacitor on the power receiving side rises, the operation of the converter on the power receiving side has already started. In this case, in a configuration in which the frequency is simply increased, high-frequency AC is supplied to the consumer. Supplied, there is a problem. Embodiment 10
In order to solve this problem, as shown in FIG. 20, the arm performing switching after time to has the same phase of S5 and S7 and the same phase of S6 and S8 during the voltage rising period of the power receiving side capacitor. To conduct several times. Thus, the clamp capacitor 5 can be charged without transmitting any voltage to the consumer. Since the voltage of the clamp capacitor 5 rises quasi-statically as in the twelfth embodiment, the voltage of the clamp capacitor 5 does not jump excessively. By shifting to a normal conversion frequency operation when the power receiving side DC capacitor voltage has reached a predetermined value, an AC voltage having a predetermined frequency can be supplied to a customer.

With such a configuration, it is possible to suppress the voltage of the clamp capacitor 5 from jumping when the power transmission side is turned on, and to improve the reliability of the GCT element.
Thereby, the stability and reliability of the DC power transmission system are greatly improved.

Eleventh Embodiment Next, an eleventh embodiment will be described. In the ninth and tenth embodiments, when the power transmission side is turned on, the value of the clamp capacitor 33 is controlled to reach a steady value in a quasi-static manner. This impairs the degree of freedom of the system. This embodiment solves the problem. In FIG. 21 and FIG. 22, after Vdc rises, the converter conducts S5, S7 and S6, S8 for a short time. Since the voltage of the clamp capacitor 5 tends to increase to 2 Vdc as described above in half the resonance period T between the inductance 33 of the power receiving side converter and the clamp capacitor 5, this conduction time is sufficiently longer than T / 2. Set shorter. If the conduction time is set to a value sufficiently shorter than T / 2, sufficient energy is not charged in the inductance 33, so that the voltage at which the clamp capacitor 5 jumps up when turned off can be suppressed to a small value. For example, the conduction time can be set so that the energy stored in the inductance 33 just reaches the steady-state value of the voltage of the clamp capacitor 5. Even if the conduction time is not accurate, T
If it is sufficiently shorter than / 2, the steady value is always reached by repeating this operation at least a plurality of times.

With such a configuration, even after the voltage of the DC capacitor 30 on the power receiving side has completely risen, the voltage of the clamp capacitor 5 can be maintained at a steady value without jumping up. ,
A stable and reliable DC power transmission system can be realized.

[0049]

In the power converter according to the first to fourth aspects of the present invention, one arm is constituted by a switch group in which semiconductor switching elements having a self-extinguishing function are connected in series, and at least two arms are provided. In the power converter in which a high-voltage power converter is configured by combining the above and a snubber circuit is provided at both ends of the semiconductor switching element, the snubber circuit is a series circuit of a clamp diode and a clamp capacitor at both ends of the semiconductor switching element. And a non-linear circuit is connected in parallel to both ends of the clamp capacitor. The non-linear circuit is composed of a non-linear resistance element or a non-linear resistance circuit using a non-linear resistance element and a semiconductor control element. Is simple and minimizes unnecessary losses It has the effect of it is possible to reliably suppress the breakdown of the switching elements, thereby improving the reliability of the apparatus.

In the power converter according to the fifth aspect of the present invention, since a capacitor is connected between the connection point between the clamp capacitor and the impedance element and the control electrode of the discharging semiconductor control element, The voltage rise can be suppressed, the value of the clamp capacitor can be set small, and the cost and size can be reduced. Also, the reliability of the discharge semiconductor control element is improved.

In the power converter according to claim 6 of the present invention, since the non-linear resistance circuit is configured by using at least two semiconductor control elements connected in series, the cost of a single component is reduced. The cost of the apparatus can be reduced.

In a power converter according to a seventh aspect of the present invention, the non-linear circuit using the semiconductor control element includes a semiconductor control element with a control electrode for discharging and a first high-voltage side of the semiconductor control element. A series body of the first impedance and the second impedance connected in parallel between the main electrode and the second main electrode on the low voltage side, and between a series connection point of the series body and a control electrode of the semiconductor control element. Since a non-linear resistance element having a threshold voltage characteristic is connected to the, the cost of parts can be greatly reduced.

In the power converter according to claim 8 of the present invention, the two impedance elements are respectively a parallel circuit of a first resistor and a first capacitor and a second circuit of a second capacitor.
And a CR circuit having the same CR time constant. Therefore, excellent voltage dividing performance can be realized independently of the frequency, and the performance of the snubber circuit is improved.

In a power converter according to a ninth aspect of the present invention, the two impedance elements are respectively a parallel circuit of a first resistor and a first capacitor, and a second circuit.
And a parallel circuit of a second capacitor and a second capacitor.
The CR time constant by the resistor and the first capacitor is made larger than the CR time constant by the second resistor and the second capacitor,
Since the impedance formed by the first resistor and the first capacitor is connected to the first main electrode side of the semiconductor control element, the discharge current can be increased during a transient, and the voltage increase of the clamp capacitor can be suppressed. The value of the capacitor can be set small, and cost reduction and miniaturization can be realized. Further, the reliability of the semiconductor control element is also improved.

In a power converter according to a tenth aspect of the present invention, one arm is constituted by a switch group in which semiconductor switching elements having a self-extinguishing function are connected in series, and at least two or more of the arms are combined. In a power converter comprising a high-voltage power converter and a snubber circuit provided at both ends of the semiconductor switching element, the snubber circuit connects a series circuit of a clamp diode and a clamp capacitor between main electrodes of the semiconductor switching element. A discharge switch is provided at both ends of the clamp diode, and a series circuit of a constant voltage element such as a zener diode and an impedance element is connected to both ends of the clamp capacitor, and the impedance element and the constant voltage element are connected in series. A semiconductor switch having the self-extinguishing function Connected to the control electrode of the switching element, and the control electrode is connected to the gate drive circuit via the current control element, realizing a compact and low-cost device without specially providing a semiconductor control element for discharging electric charge. I do.

In the power converter according to the eleventh aspect of the present invention, since a gate speed-up switch is provided at both ends of the current limiting element, the switching loss of the semiconductor switching element can be reduced.

In a power converter according to a twelfth aspect of the present invention, a switch group in which semiconductor switching elements having a self-extinguishing function are connected in series constitutes one arm, and at least two or more of the arms are combined to provide a high voltage. In a power converter that performs DC power transmission by using the AC / DC converter at least on the power receiving side, snubber circuits are provided at both ends of the semiconductor switching elements, and the snubber circuit is a semiconductor. A series circuit of a clamp diode and a clamp capacitor is connected to both ends, and both ends of the clamp capacitor are constituted by a nonlinear resistance circuit using a nonlinear resistance element or a semiconductor control element, and power is supplied to the power transmission side of the power converter. During the period when the DC voltage of the transmission line rises, Since the multiple times the switching device, it is possible to suppress the jump of the voltage of the clamp capacitor, to prevent the breakdown of the semiconductor switching element, it is possible to obtain a stable and reliable transmission system.

According to a thirteenth aspect of the present invention, when power is supplied to the power transmission side of the power conversion device, the power conversion side power conversion side power supply side power conversion side power conversion side DC power supply voltage increases. Since the device alternately switches between the high-pressure side arm groups and the low-pressure side arm groups, it is possible to prevent generation of different frequency alternating current and the like for the customer.

In the power converter according to claim 14 of the present invention, when the power on the power transmission side is turned on, the power conversion device on the power receiving side is connected to the resonance cycle of the inductance component of the power converter and the clamp capacitor. Is repeated for less than half of the time, so that the voltage jump of the clamp capacitor can be suppressed, the destruction of the semiconductor switching element can be prevented, and a stable and reliable power transmission system can be obtained. Can supply power transmission system.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic configuration of a power conversion device of the related art and the present invention.

FIG. 2 is a diagram illustrating a configuration of a main switch unit of the power conversion device of the present invention.

FIG. 3 is a circuit diagram showing a configuration of one arm of the power conversion device of the present invention.

FIG. 4 is a diagram for explaining the configuration of the first exemplary embodiment of the present invention.

FIG. 5 is a diagram for explaining an operation of the first exemplary embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a third exemplary embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a fourth exemplary embodiment of the present invention.

FIG. 9 is a diagram illustrating the operation of the fourth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a fifth exemplary embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a sixth exemplary embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a sixth exemplary embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of a seventh exemplary embodiment of the present invention.

FIG. 14 is a diagram illustrating the operation of the seventh embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of an eighth embodiment of the present invention.

FIG. 16 is a diagram illustrating the operation of the eighth embodiment of the present invention.

FIG. 17 is a diagram illustrating a configuration of a ninth embodiment of the present invention.

FIG. 18 is a diagram showing a configuration of a ninth embodiment of the present invention.

FIG. 19 is a diagram for explaining the operation of the ninth embodiment of the present invention.

FIG. 20 is a diagram illustrating the operation of the tenth embodiment of the present invention.

FIG. 21 is a diagram illustrating the operation of the eleventh embodiment of the present invention.

FIG. 22 is a diagram illustrating the operation of the eleventh embodiment of the present invention.

FIG. 23 is a configuration diagram of a conventional power converter.

FIG. 24 is a configuration diagram of a conventional power converter.

[Explanation of symbols]

1. Series valve, 2. Semiconductor switching element, 3. Diode, 4. Clamp diode, 5. Clamp capacitor, 6. Impedance element, 7. Zenadio
8 Gate resistance, 9 Semiconductor control element, 10 Snubber circuit, 11 Series stage, 12 Gate circuit, 13
Input, 14 inductance, 15 inductance per stage, 16, 18 resistance, 17, 22
Capacitor, 19 reverse discharge switch, 20 gate impedance element, 21 gate speed-up switch, 30
Power receiving side DC capacitor, 31 Power transmitting side DC capacitor, 32 Transmission line inductance, 33 Power receiving side converter inductance, 40 AC side closing switch, 41
Power transmission side power supply inductance, 50 AC power supply, 51 Power transmission side converter inductance, 90 Nonlinear resistance element.

Claims (14)

[Claims] An arm is composed of a switch group in which semiconductor switching elements having a self-extinguishing function are connected in series, and a high-voltage power converter is constructed by combining at least two of the arms. In a power converter in which a snubber circuit is provided at both ends of a switching element, the snubber circuit connects a series circuit of a clamp diode and a clamp capacitor to both ends of a semiconductor switching element, and connects a non-linear circuit in parallel to both ends of the clamp capacitor. The power conversion device is characterized in that the non-linear circuit comprises a non-linear resistance element or a non-linear resistance circuit using a non-linear resistance element and a semiconductor control element. 2. The power converter according to claim 1, wherein the nonlinear circuit is connected to both ends of the semiconductor switching element via an impedance element. 3. The power converter according to claim 1, wherein the non-linear resistance element comprises a zener diode, an arrester, or a varistor. 4. A non-linear resistance circuit using the semiconductor control element, wherein a non-linear resistance circuit having a control electrode for discharge and a first main electrode on a high voltage side of the discharge semiconductor element and a control electrode are connected in parallel. The power converter according to claim 1 or 2, further comprising: a nonlinear resistance element connected thereto; and a resistance connected in parallel between a control electrode of the discharging semiconductor element and a second main electrode on a low voltage side. . 5. The power converter according to claim 4, wherein a capacitor is connected between a connection point between the clamp capacitor and the impedance element and a control electrode of the discharge semiconductor control element. 6. The power converter according to claim 1, wherein the non-linear resistance circuit is configured using at least two or more semiconductor control elements connected in series. 7. The non-linear circuit using the semiconductor control element includes a semiconductor control element having a control electrode for discharging, a first main electrode on a high voltage side and a second main electrode on a low voltage side of the semiconductor control element. A series body of the first impedance and the second impedance connected in parallel between, and a non-linear resistance element having a threshold voltage characteristic is connected between a series connection point of the series body and a control electrode of the semiconductor control element. The power converter according to claim 1. 8. The two impedance elements each comprise a parallel circuit of a first resistor and a first capacitor and a parallel circuit of a second resistor and a second capacitor, each having the same CR time constant. The power converter according to claim 7. 9. The two impedance elements each comprise a parallel circuit of a first resistor and a first capacitor and a parallel circuit of a second resistor and a second capacitor, wherein the first resistor and the first capacitor are connected in parallel. The CR time constant by the capacitor was made larger than the CR time constant by the second resistor and the second capacitor, and the impedance formed by the first resistor and the first capacitor was connected to the first main electrode side of the semiconductor control element. The power converter according to claim 7. 10. A high-voltage power conversion device comprising a switch group in which semiconductor switching elements having a self-arc-extinguishing function are connected in series, and a high-voltage power converter is formed by combining at least two of said arms. In a power converter in which snubber circuits are provided at both ends of a switching element, the snubber circuit connects a series circuit of a clamp diode and a clamp capacitor between main electrodes of a semiconductor switching element, and a discharge switch is provided at both ends of the clamp diode. A semiconductor switching element having a self-extinguishing function by connecting a series circuit of a constant voltage element such as a zener diode and an impedance element to both ends of a clamp capacitor, and a series connection point of the impedance element and the constant voltage element. Connected to the control electrode of A power converter connected to a gate drive circuit via a control element. 11. The power converter according to claim 10, wherein a gate speed-up switch is provided at both ends of said current limiting element. 12. A switch group in which semiconductor switching elements having a self-extinguishing function are connected in series is defined as one arm,
A high-voltage AC / DC converter is configured by combining at least two or more of the arms, and in a power converter that performs DC power transmission using the AC / DC converter at least on the power receiving side, the semiconductor switching element may be provided at both ends thereof. A snubber circuit is provided, and the snubber circuit is configured by connecting a series circuit of a clamp diode and a clamp capacitor to both ends of a semiconductor, and a nonlinear resistance circuit using a nonlinear resistance element or a semiconductor control element at both ends of the clamp capacitor, When the power on the power transmission side of the power converter is turned on, during a period in which the DC voltage of the transmission line rises,
A power converter that switches the power receiving-side power converter a plurality of times. 13. The power conversion device according to claim 1, wherein when the power is supplied to the power transmission side of the power conversion device, during a period in which the DC voltage on the power transmission side increases, the power conversion device on the power reception side includes a pair of high-voltage side arms and a pair of low-voltage side arms. 13. Switching between groups alternately.
The power converter according to any one of the preceding claims. 14. When the power on the power transmission side is turned on,
13. The power conversion device according to claim 12, wherein the power reception device on the power receiving side repeatedly conducts electricity for a time shorter than half of the resonance period between the inductance component of the power conversion device and the clamp capacitor.