Three-level direct current converter

Abstract

The converter comprises a three-level inverter, a resonance circuit, a transformer and a rectifier, the resonance circuit comprises a first resonance circuit and a second resonance circuit, the alternating current side of the three-level inverter is connected with a primary side coil of the transformer through the first resonance circuit, and the alternating current side of the three-level inverter is connected with a secondary side coil of the transformer through the second resonance circuit. The first resonance circuit is arranged between the inverter and the primary side of the transformer, the alternating current side of the rectifier is connected with the secondary side coil of the transformer through the second resonance circuit, and the alternating current side of the rectifier is connected with the secondary side coil of the transformer through the second resonance circuit. The current of the switching tubes in the inverter and the rectifier can be effectively reduced when the switching tubes are turned off, so that the loss of the switching tubes can be effectively reduced; besides, by adopting the three-level inverter, the level number of the voltage signal output by the inverter can be effectively increased, and the harmonic content in the output voltage signal can be effectively reduced.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and in particular relates to a three-level DC converter. Background Art

[0002] With the continuous development of the economy, the demand for electricity is growing faster and faster. At the same time, problems such as energy shortage and environmental protection are becoming increasingly prominent. The application of new energy power generation technologies represented by wind power generation and solar power generation is becoming more and more mature. New energy power generation technology will usher in a prosperous development in the future. These new energy sources are usually scattered and far away from the power user center. Generally, DC transmission is used to transmit new energy. Since different distribution systems usually require power supply of different voltage levels, DC converters are required for voltage conversion.

[0003] Existing DC converters generally include an inverter, a transformer and a rectifier. The input power supply voltage is converted through the inverter circuit, the transformer and the rectifier to supply power to the corresponding load. Since the inverter circuit and the rectifier are usually provided with a switch tube, when the switch tube in the inverter and the rectifier is turned off, the switch tube loss is large due to the large turn-off current. In addition, since the existing DC converter generally adopts a two-level inverter, the number of levels of the voltage signal output by the inverter is small, and the harmonic content in the output voltage signal is large. Summary of the invention

[0004] The purpose of the present application is to provide a three-level DC converter; the three-level DC converter provided by the present application can effectively reduce the current of the switching tubes in the inverter and the rectifier when they are turned off, thereby effectively reducing the loss of the switching tubes, effectively increasing the number of levels of the voltage signal output by the inverter, and effectively reducing the harmonic content in the output voltage signal.

[0005] The technical solutions provided by this application are as follows: A three-level DC converter, comprising: a three-level inverter, a resonant circuit, a transformer and a rectifier, wherein the resonant circuit comprises a first resonant circuit and a second resonant circuit; The AC side of the three-level inverter is connected to the primary coil of the transformer through the first resonant circuit; The AC side of the rectifier is connected to the secondary coil of the transformer through the second resonant circuit; The three-level inverter is used to convert the input first DC voltage signal into a multi-level first AC voltage signal and output it when receiving the first driving signal; The first resonant circuit is used to provide a resonant current for the three-level inverter to reduce the current of the switch tube in the three-level inverter when it is turned off; The rectifier is used to convert the input first AC voltage signal into a second DC voltage signal and output it when receiving the second driving signal; The second resonant circuit is used to provide a resonant current for the rectifier to reduce the current of the switch tube in the rectifier when it is turned off.

[0006] Optionally, the first resonant circuit includes a first resonant capacitor and a first resonant inductor, and the second resonant circuit includes a second resonant capacitor and a second resonant inductor; the first end of the AC side of the three-level inverter is connected to the first end of the first resonant capacitor; the second end of the first resonant capacitor is connected to the first end of the first resonant inductor; The second end of the first resonant inductor is connected to the first end of the primary coil of the transformer; the second end of the AC side of the three-level inverter is connected to the second end of the primary coil of the transformer; The first end of the second resonant inductor is connected to the first end of the secondary coil of the transformer; the second end of the second resonant inductor is connected to the first end of the second resonant capacitor; the second end of the second resonant capacitor is connected to the first end of the AC side of the rectifier; the second end of the secondary coil of the transformer is connected to the second end of the AC side of the rectifier.

[0007] Optionally, the converter includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a first clamping diode, a second clamping diode, a third clamping diode and a fourth clamping diode; The first end of the first switch tube is connected to the first end of the fifth switch tube and serves as the first end of the DC side of the three-level inverter; The anode of the first clamping diode is connected to the cathode of the second clamping diode, the anode of the third clamping diode and the cathode of the fourth clamping diode, and serves as the second end of the DC side of the three-level inverter; The second end of the fourth switch tube is connected to the second end of the eighth switch tube and serves as the third end of the DC side of the three-level inverter; The second end of the first switch tube is connected to the cathode of the first clamping diode and the first end of the second switch tube; The second end of the fifth switch tube is connected to the cathode of the third clamping diode and the first end of the sixth switch tube; the second end of the second switch tube is connected to the first end of the third switch tube and serves as the first output end of the three-level inverter, and is connected to the first end of the first resonant capacitor; The second end of the sixth switch tube is connected to the first end of the seventh switch tube and serves as the second output end of the three-level inverter, and is connected to the second end of the primary coil of the transformer; The second end of the third switch tube is connected to the anode of the second clamping diode and the first end of the fourth switch tube; The second end of the seventh switch tube is connected to the anode of the fourth clamping diode and the first end of the eighth switch tube.

[0008] Optionally, it further includes: a first supporting capacitor and a second supporting capacitor; A first end of the first supporting capacitor is connected to a first end of a DC side of the three-level inverter; The second end of the first supporting capacitor is connected to the second end of the DC side of the three-level inverter and the first end of the second supporting capacitor; The second end of the second supporting capacitor is connected to the third end of the DC side of the three-level inverter.

[0009] Optionally, the rectifier includes: a ninth switch tube, a tenth switch tube, an eleventh switch tube and a twelfth switch tube; The first end of the ninth switch tube is connected to the first end of the eleventh switch tube; the second end of the ninth switch tube is connected to the first end of the tenth switch tube and serves as the first end of the AC side of the rectifier and the second end of the second resonant capacitor; the second end of the eleventh switch tube is connected to the first end of the twelfth switch tube and serves as the second end of the AC side of the rectifier and the second end of the secondary coil of the transformer; the second end of the tenth switch tube is connected to the second end of the twelfth switch tube.

[0010] Optionally, the rectifier also includes: a filter capacitor and a filter resistor; the first end of the filter capacitor and the first end of the filter resistor are connected to the first end of the ninth switch tube and the first end of the eleventh switch tube, and serve as the first end of the DC side of the rectifier; the second end of the filter capacitor and the second end of the filter resistor are connected to the second end of the tenth switch tube and the second end of the twelfth switch tube, and serve as the second end of the DC side of the rectifier.

[0011] Optionally, it further includes: a Buck-Boost conversion circuit, wherein the Buck-Boost conversion circuit includes a thirteenth switch tube, a fourteenth switch tube and a smoothing reactor; the first end of the thirteenth switch tube is connected to the first end of the DC side of the rectifier as the first end of the Buck-Boost conversion circuit; the second end of the thirteenth switch tube is connected to the first end of the fourteenth switch tube and the first end of the smoothing reactor; the second end of the smoothing reactor is used as the second end of the Buck-Boost conversion circuit; The second end of the fourteenth switch tube is connected to the second end of the DC side of the rectifier and serves as the third end of the Buck-Boost conversion circuit.

[0012] Optionally, it also includes: a fuse; The fuse is connected to a first end of the DC side of the three-level inverter and a first end of the first supporting capacitor.

[0013] Optionally, it further includes a first current sensor, a second current sensor, a first voltage sensor, a second voltage sensor, a third voltage sensor and a fourth voltage sensor; The first end of the first current sensor is connected to the fuse; the second end of the first current sensor is connected to the first end of the DC side of the three-level inverter, the first end of the first voltage sensor and the first end of the first supporting capacitor; the second end of the first voltage sensor is connected to the first end of the second voltage sensor, the second end of the first supporting capacitor, the first end of the second supporting capacitor and the second end of the DC side of the three-level inverter; The second end of the second voltage sensor is connected to the second end of the second supporting capacitor and the third end of the DC side of the three-level inverter; The first end of the third voltage sensor is connected to the first end of the DC side of the rectifier and the first end of the Buck-Boost conversion circuit; the second end of the third voltage sensor is connected to the second end of the DC side of the rectifier and the third end of the Buck-Boost conversion circuit; the first end of the fourth voltage sensor is connected to the second end of the Buck-Boost conversion circuit and the first end of the second current sensor; The second terminal of the fourth voltage sensor is connected to the third terminal of the Buck-Boost conversion circuit.

[0014] Optionally, it further includes: a controller, the controller being connected to the driving ends of the first to fourteenth switch tubes, the first current sensor, the second current sensor, and the first to fourth voltage sensors; The controller is used to obtain a first current signal collected by the first current sensor, a second current signal collected by the second current sensor, and a first voltage signal to a fourth voltage signal collected by the first voltage sensor to the fourth voltage sensor, and control the duty cycle of the thirteenth switch tube and the fourteenth switch tube according to the third voltage signal, the fourth voltage signal, the first preset voltage value and the second preset voltage value, and control the phase shift angle of the first switch tube to the twelfth switch tube according to the third voltage signal, the first preset voltage value, the first current signal, the second current signal, the first voltage signal and the second voltage signal.

[0015] Compared with the prior art, the present application provides a three-level DC converter, comprising: a three-level inverter, a resonant circuit, a transformer and a rectifier, wherein the resonant circuit comprises a first resonant circuit and a second resonant circuit, the AC side of the three-level inverter is connected to the primary coil of the transformer through the first resonant circuit, and the AC side of the rectifier is connected to the secondary coil of the transformer through the second resonant circuit. The three-level inverter is used to convert an input first DC voltage signal into a multi-level first AC voltage signal and output it when receiving a first drive signal. The first resonant circuit is used to provide a resonant current for the three-level inverter to reduce the current of the switch tube in the three-level inverter when it is turned off. The rectifier is used to When receiving the second drive signal, the input first AC voltage signal is converted into a second DC voltage signal and output. The second resonant circuit is used to provide a resonant current for the rectifier to reduce the current of the switch tube in the rectifier when it is turned off. In the present application, by setting a first resonant circuit between the inverter and the primary side of the transformer, and setting a second resonant circuit between the secondary side of the transformer and the rectifier, the current of the switch tube in the inverter and the rectifier when it is turned off can be effectively reduced, thereby effectively reducing the loss of the switch tube; in addition, by adopting a three-level inverter, the number of levels of the voltage signal output by the inverter can be effectively increased, and the harmonic content in the output voltage signal can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A structural block diagram of a three-level DC converter disclosed in an embodiment of the present application; Figure 2A circuit diagram of a three-level DC converter disclosed in an embodiment of the present application; Figure 3 This is a working diagram of the three-level inverter disclosed in the embodiment of the present application when outputting +U level; Figure 4 This is a working schematic diagram of the three-level inverter disclosed in the embodiment of the present application when outputting +U / 2 level; Figure 5 This is a working schematic diagram of the three-level inverter disclosed in the embodiment of the present application when outputting a 0 level; Figure 6 This is a working schematic diagram of the three-level inverter disclosed in the embodiment of the present application when outputting -U / 2 level; Figure 7 This is a working schematic diagram of the three-level inverter disclosed in the embodiment of the present application when outputting -U level; Reference numerals: 100 - three-level DC converter; 110-three-level inverter; 120-resonant circuit; 130-transformer; 140-rectifier; 150-Buck-Boost conversion circuit; 161-first current sensor; 162-second current sensor; 171-first voltage sensor; 172-second voltage sensor; 173-third voltage sensor; 174-fourth voltage sensor; 121-first resonant circuit; 122-second resonant circuit; Cr1-first resonant capacitor; Lr1-first resonant inductor; Cr2-second resonant capacitor; Lr2-second resonant inductor; Cp1-first support capacitor; Cp2-second support capacitor; Dc1-first clamping diode; Dc2-second clamping diode; Dc3-third clamping diode; Dc4-fourth clamping diode; F1-fuse; G1-first switch tube; G2-second switch tube; G3-third switch tube; G4-fourth switch tube; G5-fifth switch tube; G6-sixth switch tube; G7-seventh switch tube; G8-eighth switch tube; G9-ninth switch tube; G10-tenth switch tube; G11-eleventh switch tube; G12-twelfth switch tube; G13-thirteenth switch tube; G14-fourteenth switch tube; LMV-smoothing reactor; C5-filter capacitor; R1-filter resistor; KP1-electronic switch. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] It should be noted that when an element is referred to as being "fixed on" or "set on" another element, it can be directly on the other element or indirectly set on the other element; when an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0020] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" and "several" mean two or more, unless otherwise clearly and specifically defined.

[0022] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0023] like Figure 1As shown, a three-level DC converter 100 includes: a three-level inverter 110, a resonant circuit 120, a transformer 130 and a rectifier 140, wherein the resonant circuit 120 includes a first resonant circuit 121 and a second resonant circuit 122; the AC side of the three-level inverter 110 is connected to the primary coil of the transformer 130 through the first resonant circuit 121; the AC side of the rectifier 140 is connected to the secondary coil of the transformer 130 through the second resonant circuit 122; the three-level inverter 110 is used to receive a first drive signal , converting the input first DC voltage signal into a multi-level first AC voltage signal and outputting it; the first resonant circuit 121 is used to provide a resonant current for the three-level inverter 110 to reduce the current of the switch tube in the three-level inverter 110 when it is turned off; the rectifier 140 is used to convert the input first AC voltage signal into a second DC voltage signal and output it when receiving the second drive signal; the second resonant circuit 122 is used to provide a resonant current for the rectifier 140 to reduce the current of the switch tube in the rectifier 140 when it is turned off.

[0024] In this embodiment, the three-level DC converter 100 can be a three-level bidirectional DC converter, that is, the power supply voltage can be input from the DC side of the inverter and output from the DC side of the rectifier 140 after conversion, or the power supply voltage can be input from the DC side of the rectifier 140 and output from the DC side of the inverter after conversion.

[0025] In this embodiment, when the switch tube in the three-level inverter 110 is turned off, the first resonant circuit 121 can provide a resonant current for the three-level inverter 110, which can reduce the current flowing through the switch tube itself when the switch tube in the three-level inverter 110 is turned off, so that the current flowing through the switch tube is close to zero, so that the switch tube is soft-turned off, and the turn-off loss of the switch tube can be effectively reduced. When the switch tube in the rectifier 140 is turned off, the second resonant circuit 122 can provide a resonant current for the rectifier 140, which can reduce the current flowing through the switch tube when the switch tube in the rectifier 140 is turned off, so that the current flowing through the switch tube is close to zero, so that the switch tube is soft-turned off, and the turn-off loss of the switch tube is reduced.

[0026] In this embodiment, when receiving the first driving signal, the three-level inverter 110 can convert the input first DC voltage signal into a multi-level (such as five-level) first AC voltage signal and output it. Compared with the two-level voltage signal outputted by the two-level in the prior art, the number of levels of the voltage signal outputted by the inverter can be effectively increased, and the harmonic content in the output voltage signal can be effectively reduced.

[0027] Compared with the prior art, the present application provides a three-level DC converter 100, including: a three-level inverter 110, a resonant circuit 120, a transformer 130 and a rectifier 140, wherein the resonant circuit 120 includes a first resonant circuit 121 and a second resonant circuit 122, the AC side of the three-level inverter 110 is connected to the primary coil of the transformer 130 through the first resonant circuit 121, and the AC side of the rectifier 140 is connected to the secondary coil of the transformer 130 through the second resonant circuit 122. The three-level inverter 110 is used to convert the input first DC voltage signal into a multi-level first AC voltage signal and output it when receiving a first drive signal, and the first resonant circuit 121 is used to provide a resonant current for the three-level inverter 110 to reduce the switching tube in the three-level inverter 110 when it is turned off. The rectifier 140 is used to convert the input first AC voltage signal into a second DC voltage signal and output it when receiving the second drive signal. The second resonant circuit 122 is used to provide a resonant current for the rectifier 140 to reduce the current of the switch tube in the rectifier 140 when it is turned off. In the present application, by setting the first resonant circuit 121 between the inverter and the primary side of the transformer 130, and setting the second resonant circuit 122 between the secondary side of the transformer 130 and the rectifier 140, the current of the switch tube in the inverter and the rectifier 140 when it is turned off can be effectively reduced, thereby effectively reducing the loss of the switch tube; in addition, by adopting the three-level inverter 110, the number of levels of the voltage signal output by the inverter can be effectively increased, and the harmonic content in the output voltage signal can be effectively reduced.

[0028] like Figure 2As shown, as an implementation mode, in the embodiment of the present application, the first resonant circuit 121 includes a first resonant capacitor Cr1 and a first resonant inductor Lr1, and the second resonant circuit 122 includes a second resonant capacitor Cr2 and a second resonant inductor Lr2; the first end of the AC side of the three-level inverter 110 is connected to the first end of the first resonant capacitor Cr1; the second end of the first resonant capacitor Cr1 is connected to the first end of the first resonant inductor Lr1; the second end of the first resonant inductor Lr1 is connected to the first end of the primary coil of the transformer 130; the second end of the AC side of the three-level inverter 110 is connected to the second end of the primary coil of the transformer 130; the first end of the second resonant inductor Lr2 is connected to the first end of the secondary coil of the transformer 130; the second end of the second resonant inductor Lr2 is connected to the first end of the second resonant capacitor Cr2; the second end of the second resonant capacitor Cr2 is connected to the first end of the AC side of the rectifier 140; the second end of the secondary coil of the transformer 130 is connected to the second end of the AC side of the rectifier 140. In this embodiment, when the switch tube in the three-level inverter 110 is turned off, the first resonant capacitor Cr1 and the first resonant inductor Lr1 can provide a resonant current for the three-level inverter 110, which can reduce the current flowing through the switch tube itself when the switch tube in the three-level inverter 110 is turned off, so that the current flowing through the switch tube is close to zero, so that the switch tube can be soft-turned off, which can effectively reduce the turn-off loss of the switch tube. When the switch tube in the rectifier 140 is turned off, the second resonant capacitor Cr2 and the second resonant inductor Lr2 can provide a resonant current for the rectifier 140. Current can reduce the current flowing through the switch tube in the rectifier 140 when it is turned off, so that the current flowing through the switch tube is close to zero, so that the switch tube can be soft-turned off and the turn-off loss of the switch tube can be reduced. By adopting a mutually symmetrical first resonant circuit 121 and a second resonant circuit 122, relative to the asymmetrical resonant circuit 120, the symmetrical resonant circuit 120 is conducive to the bidirectional conversion of the converter 100, and it is easier to realize the soft shutdown of the switch tube, and the soft shutdown of the switch tube is realized by utilizing the resonance process of the magnetizing inductance and the capacitor of the transformer 130.

[0029] like Figure 2As shown, as an implementation mode, in the embodiment of the present application, the converter 100 includes: a first switch tube G1, a second switch tube G2, a third switch tube G3, a fourth switch tube G4, a fifth switch tube G5, a sixth switch tube G6, a seventh switch tube G7, an eighth switch tube G8, a first clamping diode Dc1, a second clamping diode Dc2, a third clamping diode Dc3 and a fourth clamping diode Dc4; a first end of the first switch tube G1 is connected to a first end of the fifth switch tube G5, and serves as a first end of the DC side of the three-level inverter 110; an anode of the first clamping diode Dc1 is connected to a cathode of the second clamping diode Dc2, an anode of the third clamping diode Dc3 and a cathode of the fourth clamping diode Dc4, and serves as a second end of the DC side of the three-level inverter 110; a second end of the fourth switch tube G4 is connected to a second end of the eighth switch tube G8, and serves as a third end of the three-level inverter 110. The third end of the DC side of the inverter 110; the second end of the first switch tube G1 is connected to the cathode of the first clamping diode Dc1 and the first end of the second switch tube G2; the second end of the fifth switch tube G5 is connected to the cathode of the third clamping diode Dc3 and the first end of the sixth switch tube G6; the second end of the second switch tube G2 is connected to the first end of the third switch tube G3 and serves as the first output end of the three-level inverter 110, and is connected to the first end of the first resonant capacitor Cr1; the second end of the sixth switch tube G6 is connected to the first end of the seventh switch tube G7 and serves as the second output end of the three-level inverter 110, and is connected to the second end of the primary coil of the transformer 130; the second end of the third switch tube G3 is connected to the anode of the second clamping diode Dc2 and the first end of the fourth switch tube G4; the second end of the seventh switch tube G7 is connected to the anode of the fourth clamping diode Dc4 and the first end of the eighth switch tube G8.

[0030] In this embodiment, Figure 3 As shown, if the voltage difference between the first terminal P of the DC side of the three-level inverter 110 and the second terminal O of the DC side of the three-level inverter 110 is U / 2, the voltage difference between the second terminal O of the DC side of the three-level inverter 110 and the third terminal N of the DC side of the three-level inverter 110 is U / 2, the first switch G1, the second switch G2, the seventh switch G7 and the eighth switch G8 in the three-level inverter 110 are controlled to be closed, and the level of the first AC voltage signal output between the first terminal of the AC side of the three-level inverter 110 and the second terminal of the AC side of the three-level inverter 110 is equal to +U, as shown in FIG. Figure 4 As shown, the first switch tube G1, the second switch tube G2 and the seventh switch tube G7 in the three-level inverter 110 are controlled to be closed, and the level of the first AC voltage signal output between the first end of the AC side of the three-level inverter 110 and the second end of the AC side of the three-level inverter 110 is equal to +U / 2, as shown in FIG. Figure 5As shown, the second switch tube G2 and the seventh switch tube G7 in the three-level inverter 110 are controlled to be closed, and the level of the first AC voltage signal output between the first end of the AC side of the three-level inverter 110 and the second end of the AC side of the three-level inverter 110 is equal to 0, as shown in FIG. Figure 6 As shown, the third switch tube G3, the fifth switch tube G5 and the sixth switch tube G6 in the three-level inverter 110 are controlled to be closed, and the level of the first AC voltage signal output between the first end of the AC side of the three-level inverter 110 and the second end of the AC side of the three-level inverter 110 is equal to +U / 2, as shown in FIG. Figure 7 As shown, the third switch tube G3, the fourth switch tube G4, the fifth switch tube G5 and the sixth switch tube G6 in the three-level inverter 110 are controlled to be closed, and the level of the first AC voltage signal output between the first end of the AC side of the three-level inverter 110 and the second end of the AC side of the three-level inverter 110 is equal to +U. It can be seen that the three-level inverter 110 can convert the input first DC voltage signal into a five-level first AC voltage signal and output it. Compared with the two-level voltage signal outputted by the two-level in the prior art, the number of levels of the voltage signal outputted by the inverter can be effectively increased, and the harmonic content in the output voltage signal can be effectively reduced.

[0031] like Figure 2 As shown, as an implementation manner, in the embodiment of the present application, it also includes: a first supporting capacitor Cp1 and a second supporting capacitor Cp2; the first end of the first supporting capacitor Cp1 is connected to the first end of the DC side of the three-level inverter 110; the second end of the first supporting capacitor Cp1 is connected to the second end of the DC side of the three-level inverter 110 and the first end of the second supporting capacitor Cp2; the second end of the second supporting capacitor Cp2 is connected to the third end of the DC side of the three-level inverter 110.

[0032] In this embodiment, by setting the first support capacitor Cp1 and the second support capacitor Cp2, electric energy can be temporarily stored and released when needed to support the transient power demand of the load, and the high-order harmonics in the voltage signal can be filtered out, so as to improve the quality of the output voltage signal, allow the AC component to pass, and block the DC component, so that the output voltage is smoother. As an implementation mode, in the embodiment of the present application, the rectifier 140 includes: a ninth switch tube G9, a tenth switch tube G10, an eleventh switch tube G11 and a twelfth switch tube G12; the first end of the ninth switch tube G9 is connected to the first end of the eleventh switch tube G11; the second end of the ninth switch tube G9 is connected to the first end of the tenth switch tube G10, and serves as the first end of the AC side of the rectifier 140 and the second end of the second resonant capacitor Cr2; the second end of the eleventh switch tube G11 is connected to the first end of the twelfth switch tube G12, and serves as the second end of the AC side of the rectifier 140 and is connected to the second end of the secondary coil of the transformer 130; the second end of the tenth switch tube G10 is connected to the second end of the twelfth switch tube G12.

[0033] In this embodiment, by controlling the on and off of the ninth switch tube G9, the tenth switch tube G10, the eleventh switch tube G11 and the twelfth switch tube G12, the first AC voltage signal input from the AC side of the rectifier 140 can be effectively converted into a second DC voltage signal and output. As an implementation mode, in the embodiment of the present application, the rectifier 140 also includes: a filter capacitor C5 and a filter resistor R1; the first end of the filter capacitor C5 and the first end of the filter resistor R1 are connected to the first end of the ninth switch tube G9 and the first end of the eleventh switch tube G11, and serve as the first end of the DC side of the rectifier 140; the second end of the filter capacitor C5 and the second end of the filter resistor R1 are connected to the second end of the tenth switch tube G10 and the second end of the twelfth switch tube G12, and serve as the second end of the DC side of the rectifier 140. In this embodiment, by setting the filter capacitor C5 and the filter resistor R1, the high-frequency component in the input voltage signal can be effectively filtered out.

[0034] As an implementation mode, in the embodiment of the present application, it also includes: a Buck-Boost conversion circuit, the Buck-Boost conversion circuit includes a thirteenth switch tube G13, a fourteenth switch tube G14 and a smoothing reactor LMV; the first end of the thirteenth switch tube G13 is connected to the first end of the DC side of the rectifier 140 as the first end of the Buck-Boost conversion circuit; the second end of the thirteenth switch tube G13 is connected to the first end of the fourteenth switch tube G14 and the first end of the smoothing reactor LMV; the second end of the smoothing reactor LMV is used as the second end of the Buck-Boost conversion circuit; the second end of the fourteenth switch tube G14 is connected to the second end of the DC side of the rectifier 140 and serves as the third end of the Buck-Boost conversion circuit. In this embodiment, by controlling the conduction and shutdown of the thirteenth switch tube G13 and the fourteenth switch tube G14, the conversion of the voltage signal can be effectively realized, that is, the voltage reduction or boost is realized. In this embodiment, the Buck-Boost conversion circuit may further include an electronic switch (or relay) KP1, a first end of the electronic switch KP1 is connected to the second end of the thirteenth switch tube G13, a first end of the fourteenth switch tube G14 and a first end of the smoothing reactor LMV, and a second end of the electronic switch KP1 is connected to the second end of the fourteenth switch tube G14.

[0035] As an implementation manner, in the embodiment of the present application, it further includes: a fuse F1; the fuse F1 is connected to the first end of the DC side of the three-level inverter 110 and the first end of the first supporting capacitor Cp1.

[0036] In this embodiment, by setting a fuse F1 at the first end of the DC side of the three-level inverter 110, when the current input to the first end of the DC side of the three-level inverter 110 is too large, the fuse F1 can cut off the current by melting itself at high temperature, thereby protecting the inverter and other devices.

[0037] As an implementation manner, in the embodiment of the present application, a first current sensor 161, a second current sensor 162, a first voltage sensor 171, a second voltage sensor 172, a third voltage sensor 173 and a fourth voltage sensor 174 are further included; a first end of the first current sensor 161 is connected to the fuse F1; a second end of the first current sensor 161 is connected to a first end of the DC side of the three-level inverter 110, a first end of the first voltage sensor 171 and a first end of the first supporting capacitor Cp1; a second end of the first voltage sensor 171 is connected to a first end of the second voltage sensor 172, a second end of the first supporting capacitor Cp1, a first end of the second supporting capacitor Cp2 and a second end of the DC side of the three-level inverter 110. end is connected; the second end of the second voltage sensor 172 is connected to the second end of the second supporting capacitor Cp2 and the third end of the DC side of the three-level inverter 110; the first end of the third voltage sensor 173 is connected to the first end of the DC side of the rectifier 140 and the first end of the Buck-Boost conversion circuit 150; the second end of the third voltage sensor 173 is connected to the second end of the DC side of the rectifier 140 and the third end of the Buck-Boost conversion circuit 150; the first end of the fourth voltage sensor 174 is connected to the second end of the Buck-Boost conversion circuit and the first end of the second current sensor 162; the second end of the fourth voltage sensor 174 is connected to the third end of the Buck-Boost conversion circuit.

[0038] In this embodiment, the first current sensor 161 can collect a first current signal flowing through the first end of the DC side of the three-level inverter 110 and the first supporting capacitor Cp1, the second current sensor 162 can collect a second current signal flowing through the second end of the Buck-Boost conversion circuit, the first voltage sensor 171 can collect a first voltage signal between the two ends of the first supporting capacitor Cp1, the second voltage sensor 172 can collect a second voltage signal between the two ends of the second supporting capacitor Cp2, and the fourth voltage sensor 174 can collect a third voltage signal between the second end of the Buck-Boost conversion circuit and the third end of the Buck-Boost conversion circuit. The first current sensor 161, the second current sensor 162, the first voltage sensor 171, the second voltage sensor 172 and the fourth voltage sensor 174 can send the collected first current signal, the second current signal, the first voltage signal and the third voltage signal to the controller, so that the controller controls the first switch tube G1 to the fourteenth switch tube G14 according to the received signals.

[0039] As an implementation manner, in the embodiment of the present application, it also includes: a controller, which is connected to the driving ends of the first switch tube G1 to the fourteenth switch tube G14, the first current sensor 161, the second current sensor 162, and the first voltage sensor 171 to the fourth voltage sensor 174; the controller is used to obtain the first current signal collected by the first current sensor 161, the second current signal collected by the second current sensor 162, and the first voltage signal to the fourth voltage signal collected by the first voltage sensor 171 to the fourth voltage sensor 174, and control the duty cycle of the thirteenth switch tube G13 and the fourteenth switch tube G14 according to the third voltage signal, the fourth voltage signal, the first preset voltage value and the second preset voltage value, and control the phase shift angle of the first switch tube G1 to the twelfth switch tube G12 according to the third voltage signal, the first preset voltage value, the first current signal, the second current signal, the first voltage signal and the second voltage signal.

[0040] In this embodiment, the first preset voltage value and the second preset voltage value are preset voltage values. The controller controls the duty ratio of the thirteenth switch tube G13 and the fourteenth switch tube G14 according to the third voltage signal, the fourth voltage signal, the first preset voltage value and the second preset voltage value. Specifically, the first difference may be obtained according to the first preset voltage value and the second preset voltage value, and the second difference may be obtained according to the third voltage signal and the fourth voltage signal. The duty ratio of the pulse signal outputted from the driving end of the thirteenth switch tube G13 and the fourteenth switch tube G14 is controlled according to the first difference and the second difference, so that the third voltage signal collected in real time after the control is equal to the first preset voltage value, and the fourth voltage signal collected in real time after the control is equal to the second preset voltage value, so as to achieve the function of stabilizing the voltage at the output end of the three-level DC converter; the controller controls the duty ratio of the thirteenth switch tube G13 and the fourteenth switch tube G14 according to the third voltage signal, the fourth voltage signal, the first preset voltage value and the second preset voltage value, and controls the duty ratio of the pulse signal outputted from the driving end of the thirteenth switch tube G13 and the fourteenth switch tube G14 according to the third voltage signal, the fourth voltage signal, the first preset voltage value and the second preset voltage value. The first switching transistor G1 to the twelfth switching transistor G12 are controlled by using a first preset voltage value and a third voltage signal, a second current signal, a first voltage signal and a second voltage signal. Specifically, a third difference may be obtained according to the first preset voltage value and the third voltage signal, a fourth difference may be obtained according to the first current signal and the second current signal, and a fifth difference may be obtained according to the first voltage signal and the second voltage signal. The phase shift angles of the first switching transistor G1 to the twelfth switching transistor G12 are controlled according to the third difference, the fourth difference and the fifth difference, so that when the energy required by the rear-end load connected to the output end of the three-level DC converter changes, the voltage output by the output end of the three-level DC converter can be controlled to remain constant and the current output by the output end of the three-level DC converter can be controlled to change to meet the energy required by the rear-end load. In addition, by controlling the phase shift angles of the first switching transistor G1 to the twelfth switching transistor G8 according to the fifth difference obtained by the first voltage signal and the second voltage signal, the positive and negative waveforms of the sine wave output from the AC side of the three-level inverter to the primary side of the transformer can be symmetrical, which can effectively reduce the risk of transformer bias.

[0041] It should be understood that the use of "system", "device", "unit" and / or "module" in this application is only a method for distinguishing different components, elements, parts, parts or assemblies at different levels. However, if other words can achieve the same purpose, the word can be replaced by other expressions.

[0042] The embodiments in this specification are described in a progressive manner, and each embodiment focuses on the For the differences between other embodiments, the same or similar parts between the embodiments may be referred to each other.

[0043] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-level DC converter, characterized in that: include: A three-level inverter, a resonant circuit, a transformer and a rectifier, wherein the resonant circuit comprises a first resonant circuit and a second resonant circuit; The AC side of the three-level inverter is connected to the primary coil of the transformer through the first resonant circuit; The AC side of the rectifier is connected to the secondary coil of the transformer through the second resonant circuit; The three-level inverter is used to convert the input first DC voltage signal into a multi-level first AC voltage signal and output it when receiving the first driving signal; The first resonant circuit is used to provide a resonant current for the three-level inverter to reduce the current of the switch tube in the three-level inverter when it is turned off; The rectifier is used to convert the input first AC voltage signal into a second DC voltage signal and output it when receiving the second driving signal; The second resonant circuit is used to provide a resonant current for the rectifier to reduce the current of the switch tube in the rectifier when it is turned off.

2. The converter according to claim 1, characterized in that The first resonant circuit includes a first resonant capacitor and a first resonant inductor, and the second resonant circuit includes a second resonant capacitor and a second resonant inductor; A first end of the AC side of the three-level inverter is connected to a first end of the first resonant capacitor; The second end of the first resonant capacitor is connected to the first end of the first resonant inductor; The second end of the first resonant inductor is connected to the first end of the primary coil of the transformer; The second end of the AC side of the three-level inverter is connected to the second end of the primary coil of the transformer; The first end of the second resonant inductor is connected to the first end of the secondary coil of the transformer; The second end of the second resonant inductor is connected to the first end of the second resonant capacitor; The second end of the second resonant capacitor is connected to the first end of the AC side of the rectifier; The second end of the secondary coil of the transformer is connected to the second end of the AC side of the rectifier.

3. The converter according to claim 2, characterized in that The converter comprises: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a first clamping diode, a second clamping diode, a third clamping diode and a fourth clamping diode; The first end of the first switch tube is connected to the first end of the fifth switch tube and serves as the first end of the DC side of the three-level inverter; The anode of the first clamping diode is connected to the cathode of the second clamping diode, the anode of the third clamping diode and the cathode of the fourth clamping diode, and serves as the second end of the DC side of the three-level inverter; The second end of the fourth switch tube is connected to the second end of the eighth switch tube and serves as the third end of the DC side of the three-level inverter; The second end of the first switch tube is connected to the cathode of the first clamping diode and the first end of the second switch tube; The second end of the fifth switch tube is connected to the cathode of the third clamping diode and the first end of the sixth switch tube; The second end of the second switch tube is connected to the first end of the third switch tube and serves as the first output end of the three-level inverter, and is connected to the first end of the first resonant capacitor; The second end of the sixth switch tube is connected to the first end of the seventh switch tube and serves as the second output end of the three-level inverter, and is connected to the second end of the primary coil of the transformer; The second end of the third switch tube is connected to the anode of the second clamping diode and the first end of the fourth switch tube; The second end of the seventh switch tube is connected to the anode of the fourth clamping diode and the first end of the eighth switch tube.

4. The converter according to claim 3, characterized in that Also includes: a first supporting capacitor and a second supporting capacitor; A first end of the first supporting capacitor is connected to a first end of a DC side of the three-level inverter; The second end of the first supporting capacitor is connected to the second end of the DC side of the three-level inverter and the first end of the second supporting capacitor; The second end of the second supporting capacitor is connected to the third end of the DC side of the three-level inverter.

5. The converter according to claim 4, characterized in that The rectifier comprises: a ninth switch tube, a tenth switch tube, an eleventh switch tube and a twelfth switch tube; The first end of the ninth switch tube is connected to the first end of the eleventh switch tube; The second end of the ninth switch tube is connected to the first end of the tenth switch tube and serves as the first end of the AC side of the rectifier and the second end of the second resonant capacitor; The second end of the eleventh switch tube is connected to the first end of the twelfth switch tube, and is connected to the second end of the secondary coil of the transformer as the second end of the AC side of the rectifier; The second end of the tenth switch tube is connected to the second end of the twelfth switch tube.

6. The converter according to claim 5, characterized in that The rectifier also includes: a filter capacitor and a filter resistor; The first end of the filter capacitor and the first end of the filter resistor are connected to the first end of the ninth switch tube and the first end of the eleventh switch tube, and serve as the first end of the DC side of the rectifier; The second end of the filter capacitor and the second end of the filter resistor are connected to the second end of the tenth switch tube and the second end of the twelfth switch tube, and serve as the second end of the DC side of the rectifier.

7. The converter according to claim 6, characterized in that Also includes: A Buck-Boost conversion circuit, wherein the Buck-Boost conversion circuit includes a thirteenth switching tube, a fourteenth switching tube and a smoothing reactor; The first end of the thirteenth switch tube is connected to the first end of the DC side of the rectifier as the first end of the Buck-Boost conversion circuit; The second end of the thirteenth switch tube is connected to the first end of the fourteenth switch tube and the first end of the smoothing reactor; The second end of the smoothing reactor serves as the second end of the Buck-Boost conversion circuit; The second end of the fourteenth switch tube is connected to the second end of the DC side of the rectifier and serves as the third end of the Buck-Boost conversion circuit.

8. The converter according to claim 7, characterized in that Also includes: Fuse; The fuse is connected to a first end of the DC side of the three-level inverter and a first end of the first supporting capacitor.

9. The converter according to claim 8, characterized in that Also includes a first current sensor, a second current sensor, a first voltage sensor, a second voltage sensor, a third voltage sensor and a fourth voltage sensor; The first end of the first current sensor is connected to the fuse; The second end of the first current sensor is connected to the first end of the DC side of the three-level inverter, the first end of the first voltage sensor and the first end of the first supporting capacitor; The second end of the first voltage sensor is connected to the first end of the second voltage sensor, the second end of the first supporting capacitor, the first end of the second supporting capacitor and the second end of the DC side of the three-level inverter; The second end of the second voltage sensor is connected to the second end of the second supporting capacitor and the third end of the DC side of the three-level inverter; The first end of the third voltage sensor is connected to the first end of the DC side of the rectifier and the first end of the Buck-Boost conversion circuit; The second end of the third voltage sensor is connected to the second end of the DC side of the rectifier and the third end of the Buck-Boost conversion circuit; A first end of the fourth voltage sensor is connected to a second end of the Buck-Boost conversion circuit and a first end of the second current sensor; The second terminal of the fourth voltage sensor is connected to the third terminal of the Buck-Boost conversion circuit.

10. The converter according to claim 9, characterized in that Also includes: a controller, the controller being connected to the driving ends of the first to fourteenth switch tubes, the first current sensor, the second current sensor, and the first to fourth voltage sensors; The controller is used to obtain a first current signal collected by the first current sensor, a second current signal collected by the second current sensor, and a first voltage signal to a fourth voltage signal collected by the first voltage sensor to the fourth voltage sensor, and control the duty cycle of the thirteenth switch tube and the fourteenth switch tube according to the third voltage signal, the fourth voltage signal, the first preset voltage value and the second preset voltage value, and control the phase shift angle of the first switch tube to the twelfth switch tube according to the third voltage signal, the first preset voltage value, the first current signal, the second current signal, the first voltage signal and the second voltage signal.

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