CN216598978U

CN216598978U - Inner tube protection circuit of ANPC circuit, converter and inverter

Info

Publication number: CN216598978U
Application number: CN202123450188.4U
Authority: CN
Inventors: 杨远钢; 杜建林
Original assignee: Suzhou Huichuan Control Technology Co Ltd
Current assignee: Suzhou Huichuan Control Technology Co Ltd
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-05-24
Anticipated expiration: 2031-12-31

Abstract

The utility model discloses an inner tube protection circuit, converter and dc-to-ac converter of ANPC circuit, the inner tube protection circuit of ANPC circuit includes two sets of active clamp circuit, and the input of two sets of active clamp circuit is connected with the collecting electrode of two inner tubes respectively, and the output is connected with the gate pole of two inner tubes respectively; the voltage between the collector electrodes and the emitter electrodes of the two inner tubes is greater than or equal to an overvoltage threshold value, so that the charges of the collector electrodes of the inner tubes flow to a gate electrode to delay the turn-off speed of the inner tubes; and is turned off when the voltage between the collector and emitter of the inner tube is below an overvoltage threshold. The utility model discloses the inner tube of protecting the ANPC circuit is not by the output ability that the excessive pressure damaged on the basis that has improved the switch tube as far as possible, has promoted product property ability.

Description

Inner tube protection circuit, converter and dc-to-ac converter of ANPC circuit

Technical Field

The utility model relates to a power electronic technology field especially relates to an inner tube protection circuit, converter and dc-to-ac converter of ANPC circuit.

Background

The ANPC topology is an improved NPC topology, and a switching tube is respectively incorporated at the position of a clamping diode on the basis of an NPC-I structure. The current circulation path is controlled by adjusting the switch mode, so that the loss balance of a power device is realized, and the output power and the efficiency of the converter are improved.

The topology of the ANPC is shown in fig. 1, and includes six IGBT (Insulated Gate Bipolar Transistor) switching tubes T1 to T6 and diodes provided at both ends of the six switching tubes, respectively. One modulation method is as follows: the switching tubes T1, T4, T5 and T6 are high-frequency tubes, namely, work in a high-frequency (for example, several KHz to tens of KHz) switching frequency working state; t2 and T3 are power frequency tubes, namely working states of working at power frequency (50Hz) switching frequency. The modulation mode can control the mutual switching of the current conversion loops, fully utilize the output current of each tube, balance loss and save temperature.

Fig. 2 and 3 are commutation loops of P-O and N-O of the ANPC in the modulation mode, and it can be seen from the figure that the commutation loops are both inside the same half-bridge module, and the commutation loops are small; however, when commutation is performed at zero, as shown in fig. 4, the commutation loop exists between different modules, and the commutation loop is large, and when commutation is performed at zero crossing, the switching logic performs commutation generally by switching the inner tubes T2 and T3.

Through experimental measurement, when the small loop carries out commutation, the stray inductance is 45-70 nH, and when the large loop carries out commutation, the stray inductance is 340-370 nH. When the off speed of the IGBT is high under a large noise, a large instantaneous current spike occurs, and at this time, the voltage Vce between the collector and emitter of the inner tubes T2 and T3 may exceed the withstand voltage of the IGBT, and the inner tubes may be easily damaged.

At present, the common solution is to increase the resistance of the gate turn-off resistors of the two inner tubes to reduce the IGBT turn-off speed. However, when Vce is small, the turn-off speed of the IGBT is still reduced by the turn-off resistance, and this brings unnecessary IGBT switching loss, so that the switching loss of the IGBT switching tube is large.

SUMMERY OF THE UTILITY MODEL

A primary object of the present invention is to provide an inner tube protection circuit, a converter and an inverter for an ANPC circuit, which are designed to solve the problem of large switching loss of a switching tube when the inner tube of an ANPC topology circuit is protected.

In order to achieve the above object, the present invention provides an inner tube protection circuit of an ANPC circuit, which includes six switching tubes and six diodes, wherein each switching tube is connected in reverse with one diode; the six switch tubes are respectively a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube, a collector of the first switch tube is connected with the positive electrode of a bus, an emitter of the fourth switch tube is connected with the negative electrode of the bus, an emitter of the first switch tube is connected with collectors of the second switch tube and the fifth switch tube, a collector of the fourth switch tube is connected with emitters of the third switch tube and the sixth switch tube, the emitter of the fifth switch tube and the collector of the sixth switch tube are both connected to the midpoint of the bus, and the emitter of the second switch tube and the collector of the third switch tube are connected together to form a bridge arm end; the first switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube work in a working state with high switching frequency, and the second switching tube and the third switching tube work in a working state with power frequency;

the inner tube protection circuit of the ANPC circuit comprises two groups of active clamping circuits,

the input end of the active clamping circuit is connected with the collector of the second switching tube, and the output end of the active clamping circuit is connected with the gate of the second switching tube; the voltage between the collector and the emitter of the second switching tube is greater than or equal to an overvoltage threshold, so that the charge of the collector of the second switching tube flows to the gate to delay the turn-off speed of the second switching tube; the voltage between the collector and the emitter of the second switch tube is cut off when the voltage is lower than the overvoltage threshold value;

the input end of the other group of the active clamping circuits is connected with the collector electrode of the third switching tube, and the output end of the other group of the active clamping circuits is connected with the gate electrode of the third switching tube; the voltage of the collector and the emitter of the third switching tube is greater than or equal to the overvoltage threshold, so that the charge of the collector of the third switching tube flows to the gate to delay the turn-off speed of the third switching tube; and is cut off when the voltage between the collector and the emitter of the third switching tube is lower than the overvoltage threshold value.

Optionally, the active clamp circuit includes a clamp unit and an anti-reverse-flow unit; the active clamping circuit comprises a clamping unit and a voltage-resistant reverse-pouring unit; the first end of the clamping unit is the input end of the active clamping circuit, the second end of the clamping unit is connected with the first end of the voltage backflow prevention unit, and the second end of the voltage backflow prevention unit is the output end of the active clamping circuit;

the clamping unit is used for conducting when the voltage between the first end and the second end of the clamping unit exceeds an overvoltage threshold value, and clamping the voltage between the first end and the second end at a first safe voltage.

Optionally, the clamping unit comprises a clamping device; the first end of the clamping device is the first end of the clamping unit, and the second end of the clamping device is the second end of the clamping unit;

the voltage backflow prevention unit comprises a diode; the anode of the diode is the first end of the voltage-proof reverse-flow unit, and the cathode of the diode is the second end of the voltage-proof reverse-flow unit.

Optionally, the clamping device is a transient voltage suppression diode, a bidirectional transient suppression diode, or a voltage regulator tube.

Optionally, the inner tube protection circuit of the ANPC circuit further includes two driving units;

the first end of a driving unit is connected with the gate pole of the second switching tube, and the second end of the driving unit is connected with the emitter of the second switching tube;

the first end of the other driving unit is connected with the gate electrode of the third switching tube, and the second end of the other driving unit is connected with the emitter electrode of the third switching tube.

Optionally, the driving unit comprises a resistor and a capacitor; the first end of the resistor is connected with the first end of the capacitor, and the second end of the resistor is connected with the second end of the capacitor; the common end connected with the first end of the resistor and the first end of the capacitor is the first end of the driving unit, and the common end connected with the second end of the resistor and the second end of the capacitor is the second end of the driving unit.

In addition, in order to achieve the above object, the present invention further provides a converter, comprising an ANPC circuit and an inner tube protection circuit of the ANPC circuit; the inner tube protection circuit of the ANPC circuit is used for respectively protecting the inner tubes when two ends of the two inner tubes of the ANPC circuit are in overvoltage; the inner tube protection circuit of the ANPC circuit is configured as the inner tube protection circuit of the ANPC circuit described above.

In addition, in order to achieve the above object, the present invention also provides an inverter, comprising an ANPC circuit and an inner tube protection circuit of the ANPC circuit; the inner tube protection circuit of the ANPC circuit is used for respectively protecting the inner tubes when two ends of the two inner tubes of the ANPC circuit are in overvoltage; the inner tube protection circuit of the ANPC circuit is configured as the inner tube protection circuit of the ANPC circuit described above.

The utility model arranges active clamping circuits between the collecting electrodes and gate poles of two inner tubes of ANPC circuit, namely the second switch tube and the third switch tube; taking the second switch tube as an example, when the tube closing speed is too high and the voltage Vce between the collector and the emitter reaches the overvoltage threshold, the active clamping circuit acts to reinject the collector charges to the G level, so that the second switch tube is turned on again, the turn-off speed of the second switch tube is delayed, the transient current spike is reduced, and the voltage between the collector and the emitter is reduced; when Vce is reduced to be smaller than an overvoltage threshold value, the active clamping circuit restores the blocking state, namely is cut off, and the switching tube is cut off under the action of a cut-off level. Therefore, the active clamping circuit works when the inner tube of the ANPC circuit is possibly damaged due to the fact that Vce is too high, and the two switching tubes are protected; when Vce is smaller, the switching-off speed of the switching tube is not influenced, and the switching loss of the switching tube is not influenced, so that the output capacity of the switching tube is improved to the greatest extent, and the product performance is indirectly improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic diagram of a prior art ANPC topology;

FIGS. 2-3 are schematic diagrams of P-O and N-O commutation loops of the ANPC topology of FIG. 1;

FIG. 4 is a schematic diagram of a zero commutation loop of the ANPC topology of FIG. 1;

fig. 5 is a block diagram of an embodiment of an inner tube protection circuit of the ANPC circuit of the present invention;

fig. 6 is a schematic circuit diagram of the embodiment of fig. 5.

The objects, features and advantages of the present invention will be further described with reference to the accompanying drawings.

The reference numbers illustrate:

reference numerals	Name (R)	Reference numerals	Name (R)
				100	ANPC circuit	T1～T6	First to sixth switching tubes
10	Active clamping circuit	Z1	Clamping device
				20	Clamping unit	Z2	Second clamping device
21	Anti-reverse-irrigation unit	Z3	Third clamping device
				30	Drive unit	Z4	Fourth clamping device
T2_C	Collector of the second switch tube	Z5	Diode with a high-voltage source
				T2_E	Emitter of second switch tube	C1	Capacitor with a capacitor element
T2_G	Gate pole of second switch tube	R1	Resistance (RC)

Detailed Description

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

It should be noted that all the directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the motion situation, etc. in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit ly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions in the embodiments may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

The utility model provides an inner tube protection circuit of ANPC circuit, refer to FIG. 5, the ANPC circuit includes six switch tubes and six diodes, wherein, each switch tube is in reverse parallel with a diode; the six switching tubes are respectively a first switching tube T1, a second switching tube T2, a third switching tube T3, a fourth switching tube T4, a fifth switching tube T5 and a sixth switching tube T6, the collector of the first switching tube T1 is connected with the positive pole DC + of the bus, the emitter of the fourth switching tube T4 is connected with the negative pole DC of the bus, the emitter of the first switching tube T1 is connected with the second switching tube T2 and the collector of the fifth switching tube T5, the collector of the fourth switching tube T4 is connected with the emitters of the third switching tube T3 and the sixth switching tube T6, the emitter of the fifth switching tube T5 and the collector of the sixth switching tube T6 are connected with the bus, and the emitter of the second switching tube T2 and the collector of the third switching tube T3 are connected together to form a bridge arm end OUT; in an embodiment, the first switch tube T1, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 of the ANPC circuit all operate in an operating state where the switching frequency is high frequency, and the second switch tube T2 and the third switch tube T3 operate in an operating state where the switching frequency is power frequency;

in one set of the active clamp circuits 10, the input end is connected to the collector of the second switching tube T2, and the output end is connected to the gate of the second switching tube T2; the transistor T2 is used for enabling the charge of the collector to flow to the gate when the voltage between the collector and the emitter of the second switch tube T2 is larger than or equal to an overvoltage threshold value so as to delay the turn-off speed of the second switch tube T2; cut off when the voltage between the collector and the emitter of the second switching tube T2 is lower than the overvoltage threshold;

the input end of the other group of the active clamp circuits 10 is connected with the collector electrode of the third switch tube T3, and the output end is connected with the gate electrode of the third switch tube T3; when the collector-emitter voltage of the third switching tube T3 is greater than or equal to the over-voltage threshold, the transistor is operated to make the charge of the collector of the third switching tube T3 flow to the gate to delay the turn-off speed of the third switching tube T3; and is cut off when the voltage between the collector and the emitter of the third switching tube T3 is lower than the overvoltage threshold value.

The overvoltage threshold can be set in conjunction with an actual circuit, for example, six switching transistors of the ANPC circuit are 1200V-withstand IGBTs, and then the overvoltage threshold of the active clamp 10 can be set to 1060V.

The ANPC circuit of the circuit structure has two modulation modes, one of which is that the first switching tube T1, the fourth switching tube T4, the fifth switching tube T5 and the sixth switching tube T6 all work in a working state where the switching frequency is the power frequency, and the second switching tube T2 and the third switching tube T3 work in a working state where the switching frequency is the high frequency; in the modulation mode, when a module is designed, the T1, T4, T5 and T6 tubes can be selected as low-conduction-loss tubes, and the T2 and T3 adopt high-speed switching devices, such as MOS, SIC and the like; however, because the topological commutation loop is large, when a half-bridge module is used for building a circuit, stray inductance of the loop is difficult to process, so that the topological commutation loop is not suitable for a high-power converter, and excessive discussion is not performed in the scheme.

In this embodiment, a modulation mode is another, the first switching tube T1, the fourth switching tube T4, the fifth switching tube T5, and the sixth switching tube T6 all operate in an operating state where the switching frequency is high frequency, and the second switching tube T2 and the third switching tube T3 operate in an operating state where the switching frequency is power frequency. Wherein, the high frequency can be changed according to the actual circuit, such as 3.2KHz to more than ten KHz. The switching tube can also be selected according to actual requirements, such as IGBT. The IGBT will produce a certain voltage spike when normally turned off, but the value is not too high. However, when the inner tube of the ANPC circuit commutates at zero and when the converter is overloaded or the bridge arms are short-circuited, the voltage spikes generated in these cases are very high, and the IGBT risks being damaged.

The active clamp circuit 10, by detecting Vce, does not work when it is normal and works when it is too high, and can clamp the collector potential of the IGBT so that it does not reach too high level, delay the turn-off of the IGBT, and limit di/dt and voltage spikes, so as to avoid the voltage spikes generated when turn-off are too high or too steep, and thus the IGBT is threatened.

Specifically, when the switching speed of the second switching tube T2 is too fast, the voltage Vce between the collector and the emitter reaches the overvoltage threshold, the active clamp circuit 10 connected to the second switching tube acts to inject the charge of the collector back into the G stage of the second switching tube T2, so that the second switching tube T2 is turned on again, and the switching-off speed of the second switching tube T2 is slowed down; when the Vce voltage decreases, the active clamp circuit 10 resumes the blocking state, and the G-level charge continues to be drawn away from the second switch transistor T2 under the action of the turn-off level, so that the second switch transistor T2 is turned off. The principle of the third switching tube T3 is the same, when the tube closing speed of the third switching tube T3 is too fast, the voltage Vce between the collector and the emitter reaches the overvoltage threshold, the active clamp circuit 10 connected to the third switching tube acts to reinject the charge of the collector into the G stage of the third switching tube T3, so that the third switching tube T3 can be turned on again, and the turn-off speed of the third switching tube T3 is delayed; when the Vce voltage decreases, the active clamp circuit 10 resumes the blocking state, and the G-level charge continues to be pumped away from the third transistor T3 under the action of the turn-off level, so that the third transistor T3 is turned off.

In the scheme, active clamping circuits are respectively arranged between the collectors and gates of the second switching tube T2 and the third switching tube T3; taking the second switching tube T2 as an example, when the switching speed is too fast and the voltage Vce between the collector and the emitter reaches the overvoltage threshold, the active clamp circuit 10 acts to reinject the collector charge to the G stage, so that the second switching tube T2 is turned on again, thereby slowing the switching speed of the second switching tube T2, reducing the transient current spike, and reducing the voltage between the collector and the emitter; when Vce decreases to be less than the overvoltage threshold, the active clamp circuit 10 recovers the blocking state, i.e., is turned off, and the switching tube is turned off under the action of the turn-off level. Therefore, the active clamping circuit 10 works when the inner tube of the ANPC circuit is possibly damaged due to the fact that Vce is too high, and the switching tube is protected; the switching tube does not work when Vce is small, the turn-off speed of the switching tube is not influenced, and the switching loss of the switching tube is not influenced, so that the output capacity of the switching tube is improved as much as possible, the product performance is indirectly improved, the overvoltage protection capacity of the inner tube is improved, and the safety of a circuit is improved.

Further, referring to fig. 6, fig. 6 illustrates an active clamp circuit 10 connected to the second switch transistor T2, where the active clamp circuit 10 includes a clamp unit 20 and a voltage-leakage-preventing unit 21; the first end of the clamping unit 20 is the input end of the active clamping circuit 10, the second end of the clamping unit is connected with the first end of the voltage backflow prevention unit 21, and the second end of the voltage backflow prevention unit 21 is the output end of the active clamping circuit 10;

the clamping unit 21 is configured to conduct when a voltage between the first terminal and the second terminal thereof exceeds an overvoltage threshold, and clamp the voltage between the first terminal and the second terminal at a first safe voltage.

The first end of the clamping unit 20 is connected with a collector C of the IGBT, and the second end of the clamping unit 20 is connected with a gate pole G of the IGBT through the anti-reverse-filling unit 20; the value of the first safety voltage may be set according to the actual circuit, e.g. the first safety voltage is the same as the value of the overvoltage threshold.

When the Vce of the switching tube reaches an overvoltage threshold value, the clamping unit 20 works to clamp the Vce of the IGBT at a first safe voltage; when Vce is lower than the overvoltage threshold, the clamping unit 20 stops operating so as not to affect the normal operation of the IGBT. By arranging the anti-reverse-filling unit 20, the situation that the clamping unit 20 is conducted under the action of the voltage of the gate pole G to pull down the voltage of the gate pole G when the IGBT is normally switched on can be prevented.

Further, the structures of the clamping unit 20 and the anti-reverse-filling unit 21 may be set according to actual needs, for example, the clamping unit 20 includes a clamping device Z1; the first terminal of the clamping device Z1 is the first terminal of the clamping cell 20, and the second terminal of the clamping device Z1 is the second terminal of the clamping cell 20; the voltage backflow prevention unit 21 includes a diode Z5; the anode of the diode Z5 is the first end of the voltage-proof back-flow unit 21, and the cathode of the diode Z5 is the second end of the voltage-proof back-flow unit 21.

The clamping device Z1 may be a single device or may be formed by connecting a plurality of devices in series. For example, clamp device Z1 may also be connected in series with a second clamp device Z2, a third clamp device Z3, and a fourth clamp device Z4. The diode Z5 may be a normal diode, a zener diode or a bidirectional transient voltage suppressor diode, and is not limited herein.

Further, the clamping device Z1 is a TVS, a bidirectional TVS, or a zener. When the clamping device Z1 is a transient voltage suppression diode TVS or a voltage regulator, the cathode of the transient voltage suppression diode TVS or the voltage regulator is the first end of the clamping device Z1, and the anode is the second end of the clamping device Z1.

Based on the hardware structure, the working process of the inner tube protection circuit of the ANPC circuit can be as follows:

when the IGBT is too fast in turn-off speed and the Vce voltage reaches the threshold value of the clamping device Z1, the clamping device Z1 acts to inject charges into the stage G of the IGBT again; so as to delay the turn-off speed of the IGBT; when the Vce voltage is reduced, the clamping device Z1 restores the blocking state, and the G-level charge is continuously drawn away from the IGBT under the action of the turn-off level, so that the IGBT is turned off;

when the IGBT is normally on, the diode Z5 is in a blocking state.

In summary, based on the above hardware structure, although in engineering applications, the stray inductance of the loop is certain; an overvoltage of Vce generally occurs at higher output powers. The turn off of the IGBT is therefore independent of the clamp device Z1 when the output current does not reach the threshold of the clamp device Z1. When the output current is large and the stress of Vce reaches the active clamping threshold, the clamping device Z1 works again.

The method and the method for increasing the turn-off resistance delay the turn-off of the IGBT, but the increase of the turn-off resistance is acted when the IGBT acts every time, and the increase of the protection of the active clamping circuit only acts when the Vce actually has overvoltage, and does not act when the output power is lower. Therefore, according to the scheme, the active clamping circuit is added in the inner tube (T2 and T3) of the three-level ANPC, the Vce of the IGBT is guaranteed to be in a safety range, the output capacity of the switching tube is improved to the greatest extent on the basis that the inner tube of the ANPC circuit is protected from being damaged by overvoltage, and the product performance is improved.

Further, the inner tube protection circuit further includes two driving units 30;

a first end of a driving unit 30 is connected to the gate of the second switching transistor T2, and a second end is connected to the emitter of the second switching transistor T2;

a first terminal of another driving unit 30 is connected to a gate of the third switching transistor T3 (not shown), and a second terminal is connected to an emitter of the third switching transistor T3. The two driving units are driving circuits of the IGBT, and the switching capability of the second switching tube T2 and the third switching tube T3 is enhanced.

Further, the driving unit 30 includes a resistor R1 and a capacitor C1; a first end of the resistor R1 is connected with a first end of the capacitor C1, and a second end of the resistor R1 is connected with a second end of the capacitor C1; the common terminal of the first terminal of the resistor R1 and the first terminal of the capacitor C1 is the first terminal of the driving unit 30, and the common terminal of the second terminal of the resistor R1 and the second terminal of the capacitor C1 is the second terminal of the driving unit 30. It should be noted that the selection of the resistor R1 and the capacitor C1 need not be limited, and those skilled in the art can set the resistor R1 and the capacitor C1 by referring to the techniques commonly used in the art, and only need to implement the corresponding functions described above.

The utility model also provides a converter, which comprises an ANPC circuit and an inner tube protection circuit of the ANPC circuit; the inner tube protection circuit of the ANPC circuit is used for respectively protecting the inner tubes when two ends of the two inner tubes of the ANPC circuit are in overvoltage; the structure of the inner tube protection circuit of the ANPC circuit can refer to the above embodiments, and is not described herein again. It should be understood that, since the converter of the present embodiment adopts the technical solution of the inner tube protection circuit of the ANPC circuit, the converter has all the beneficial effects of the inner tube protection circuit of the ANPC circuit.

The utility model also provides an inverter, the inverter ANPC circuit and the inner tube protection circuit of the ANPC circuit; the inner tube protection circuit of the ANPC circuit is used for respectively protecting the inner tubes when two ends of the two inner tubes of the ANPC circuit are in overvoltage; the structure of the inner tube protection circuit of the ANPC circuit can refer to the above embodiments, and is not described herein again. It should be understood that, since the inverter of the present embodiment adopts the technical solution of the inner tube protection circuit of the ANPC circuit, the inverter has all the advantages of the inner tube protection circuit of the ANPC circuit.

The above is only the optional embodiment of the present invention, and not therefore the scope of the present invention is limited, all the equivalent structures or equivalent flow changes made by the contents of the specification and the drawings, or directly or indirectly applied to other related technical fields, are included in the same way in the protection scope of the present invention.

Claims

1. An inner tube protection circuit of an ANPC circuit comprises six switching tubes and six diodes, wherein each switching tube is connected with one diode in an inverted mode; the six switch tubes are respectively a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube, a collector of the first switch tube is connected with the positive electrode of a bus, an emitter of the fourth switch tube is connected with the negative electrode of the bus, an emitter of the first switch tube is connected with collectors of the second switch tube and the fifth switch tube, a collector of the fourth switch tube is connected with emitters of the third switch tube and the sixth switch tube, the emitter of the fifth switch tube and the collector of the sixth switch tube are both connected to the midpoint of the bus, and the emitter of the second switch tube and the collector of the third switch tube are connected together to form a bridge arm end; the power supply is characterized in that the first switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube work in a working state with high switching frequency, and the second switching tube and the third switching tube work in a working state with power frequency;

the input end of the active clamping circuit is connected with the collector of the second switching tube, and the output end of the active clamping circuit is connected with the gate of the second switching tube; the voltage between the collector and the emitter of the second switching tube is greater than or equal to an overvoltage threshold value, so that the charge of the collector of the second switching tube flows to the gate to delay the turn-off speed of the second switching tube; the voltage between the collector and the emitter of the second switch tube is cut off when the voltage is lower than the overvoltage threshold value;

2. The inner tube protection circuit of an ANPC circuit of claim 1, wherein the active clamp circuit comprises a clamp unit and a voltage-back-sink prevention unit; the first end of the clamping unit is the input end of the active clamping circuit, the second end of the clamping unit is connected with the first end of the voltage backflow prevention unit, and the second end of the voltage backflow prevention unit is the output end of the active clamping circuit;

3. The inner tube protection circuit of the ANPC circuit of claim 2, wherein the clamp unit comprises a clamp device; the first end of the clamping device is the first end of the clamping unit, and the second end of the clamping device is the second end of the clamping unit;

4. The inner tube protection circuit of an ANPC circuit of claim 3, wherein the clamp device is a transient voltage suppressor, a bi-directional transient voltage suppressor, or a voltage regulator tube.

5. The inner tube protection circuit of the ANPC circuit of any of claims 1-4, further comprising two drive units;

6. The inner tube protection circuit of the ANPC circuit of claim 5, wherein the drive unit comprises a resistor and a capacitor; the first end of the resistor is connected with the first end of the capacitor, and the second end of the resistor is connected with the second end of the capacitor; the common end connected with the first end of the resistor and the first end of the capacitor is the first end of the driving unit, and the common end connected with the second end of the resistor and the second end of the capacitor is the second end of the driving unit.

7. The converter is characterized by comprising an ANPC circuit and an inner tube protection circuit of the ANPC circuit; the inner tube protection circuit of the ANPC circuit is used for respectively protecting the inner tubes when two ends of the two inner tubes of the ANPC circuit are in overvoltage; the inner tube protection circuit of the ANPC circuit is configured as the inner tube protection circuit of the ANPC circuit of any of claims 1-6.

8. An inverter, characterized by comprising an ANPC circuit and an inner tube protection circuit of the ANPC circuit; the inner tube protection circuit of the ANPC circuit is used for respectively protecting the inner tubes when two ends of the two inner tubes of the ANPC circuit are in overvoltage; the inner tube protection circuit of the ANPC circuit is configured as the inner tube protection circuit of the ANPC circuit of any of claims 1-6.