Three-level NPC type fractal converter

Abstract

The invention discloses a three-level NPC type fractal converter, and relates to the technical field of AC / DC converters. The three-level NPC type fractal converter comprises: an inversion module comprising a three-level NPC type inverter, the three-level NPC type inverter being used for outputting an alternating current signal, the alternating current signal comprising a first harmonic signal in a higher harmonic interval; the harmonic generation module comprises at least one harmonic generation inverter, and the harmonic generation inverter is used for outputting a corresponding second harmonic signal according to the first harmonic signal; the first input end of the fractal connector module is electrically connected with the alternating current side of the three-level NPC type inverter, at least one second input end of the fractal connector module is correspondingly and electrically connected with the alternating current side of the at least one harmonic generation inverter, and the output end of the fractal connector module is electrically connected with the alternating current output port; the second harmonic signal is used to compensate the first harmonic signal within the fractal connector module. According to the embodiment of the invention, the harmonic signal of the three-level NPC type inverter can be compensated.

Description

Technical Field

[0001] This application belongs to the field of AC / DC converter technology, and particularly relates to a three-level NPC type fractal converter. Background Technology

[0002] With the transformation of the global energy structure and the widespread application of new energy sources, especially wind and solar power, power electronics technology plays an increasingly important role in new energy power generation systems. As a core component of these systems, the performance of inverters directly affects the operating efficiency, stability, and energy conversion quality of the power system.

[0003] With the booming development of new energy power generation, the demand for high-power power electronic converters in new power systems is increasing. Three-level converters, compared to two-level converters, introduce a zero level, thus possessing better harmonic characteristics and a higher equivalent switching frequency. Commonly used three-level converters in engineering mainly include three-level neutral point clamped (NPC) converters and three-level active neutral point clamped (ANPC) converters. Among them, NPC-type three-level converters include I-type NPC three-level converters and T-type NPC three-level converters. Currently, NPC-type three-level converters are widely used in engineering.

[0004] However, in existing AC / DC converter technologies, the switching frequency of three-level converters based on three-level NPC inverters is relatively high, resulting in high losses and heat generation in the switching devices, leading to low overall output capacity and high cost per unit capacity. Therefore, how to effectively reduce the switching frequency of three-level NPC inverters and improve the overall output capacity of the converter has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This application provides a three-level NPC type fractal converter, which can effectively compensate for the harmonic signals of the three-level NPC type fractal converter, thereby helping to reduce the switching frequency of the three-level NPC type inverter and improve the overall output capacity of the converter.

[0006] In a first aspect, embodiments of this application provide a three-level NPC-type fractal converter, which includes:

[0007] The inverter module includes a three-level NPC inverter, the DC side of which is electrically connected to the first DC power supply port, and the three-level NPC inverter is used to output an AC signal, which includes the first harmonic signal in the higher harmonic range.

[0008] The harmonic generation module includes at least one harmonic generation inverter. The DC side of any harmonic generation inverter is electrically connected to the corresponding second DC power supply port. The corresponding harmonic generation inverter is used to output a corresponding second harmonic signal according to the first harmonic signal.

[0009] The fractal connector module has a first input terminal electrically connected to the AC side of a three-level NPC inverter, at least one second input terminal of the fractal connector module electrically connected to the corresponding AC side of at least one harmonic generation inverter, and an output terminal of the fractal connector module electrically connected to an AC output port.

[0010] The second harmonic signal is used to compensate for the first harmonic signal within the fractal connector module.

[0011] In some possible implementations, the number of harmonic generation inverters in the harmonic generation module is 1;

[0012] The alternating current signal includes n first harmonic signals corresponding to n higher harmonic intervals, where n is greater than or equal to 1 and n is a positive integer.

[0013] The harmonic generation inverter is used to output n second harmonic signals, and the n second harmonic signals correspond one-to-one with the n first harmonic signals.

[0014] In some possible implementations, the number of harmonic generation inverters in the harmonic generation module is n, where n is greater than 1 and n is a positive integer;

[0015] The AC sides of the n harmonic generation inverters are electrically connected to the n second input terminals of the fractal connector module, respectively.

[0016] The switching frequency of the switching device of the i-th harmonic generator inverter is greater than the switching frequency of the switching device of the (i-1)-th harmonic generator inverter, 1 < i ≤ n, where i is a positive integer;

[0017] The alternating current signal includes n first harmonic signals corresponding to n higher harmonic intervals. The n harmonic generator inverter is used to output n second harmonic signals, and the n second harmonic signals correspond one-to-one with the n first harmonic signals.

[0018] In some possible implementations, the switching frequency of any harmonic generating inverter is greater than the switching frequency of a three-level NPC inverter.

[0019] A three-level NPC inverter includes at least one supporting capacitor and a three-phase inverter bridge.

[0020] In some possible implementations, the AC side of a three-level NPC inverter includes three single-phase AC output terminals;

[0021] The three-phase inverter bridge includes a first bridge arm branch, a second bridge arm branch, and a third bridge arm branch disposed between the first DC power supply ports;

[0022] The first bridge arm branch includes the midpoint of the first bridge arm, the second bridge arm branch includes the midpoint of the second bridge arm, and the third bridge arm branch includes the midpoint of the third bridge arm. The midpoints of the first, second, and third bridge arms are electrically connected to the corresponding three single-phase AC output terminals.

[0023] At least one supporting capacitor is connected in series between the first DC power supply ports.

[0024] In some possible implementations, the three-level NPC inverter is a three-level I-type NPC structure;

[0025] The first bridge arm branch includes a first switch unit, a second switch unit, a third switch unit and a fourth switch unit connected in series between the first DC power supply ports. The second switch unit and the third switch unit are electrically connected to the midpoint of the first bridge arm.

[0026] The second bridge arm branch includes a fifth switch unit, a sixth switch unit, a seventh switch unit, and an eighth switch unit connected in series between the first DC power supply ports. The sixth switch unit and the seventh switch unit are electrically connected to the midpoint of the second bridge arm.

[0027] The third bridge arm branch includes a ninth switch unit, a tenth switch unit, an eleventh switch unit, and a twelfth switch unit connected in series between the first DC power supply ports. The tenth switch unit and the eleventh switch unit are electrically connected together at the midpoint of the third bridge arm.

[0028] The three-phase inverter bridge also includes: a first diode, a second diode, a third diode, a fourth diode, a fifth diode, and a sixth diode;

[0029] The cathode of the first diode is electrically connected to the first node, and the anode of the first diode is electrically connected to the neutral point. The cathode of the second diode is electrically connected to the neutral point, and the anode of the second diode is electrically connected to the second node. The cathode of the third diode is electrically connected to the third node, and the anode of the third diode is electrically connected to the neutral point. The cathode of the fourth diode is electrically connected to the neutral point, and the anode of the fourth diode is electrically connected to the fourth node. The cathode of the fifth diode is electrically connected to the fifth node, and the anode of the fifth diode is electrically connected to the neutral point. The cathode of the sixth diode is electrically connected to the neutral point, and the anode of the sixth diode is electrically connected to the sixth node.

[0030] The first node is the common point of the first and second switch units; the second node is the common point of the third and fourth switch units; the third node is the common point of the fifth and sixth switch units; the fourth node is the common point of the seventh and eighth switch units; the fifth node is the common point of the ninth and tenth switch units; and the sixth node is the common point of the eleventh and twelfth switch units.

[0031] In some possible implementations, the three-level NPC inverter is a three-level T-type NPC structure;

[0032] The first bridge arm branch includes a thirteenth switch unit and a fourteenth switch unit connected in series between the first DC power supply ports. The thirteenth switch unit and the fourteenth switch unit are electrically connected to the midpoint of the first bridge arm.

[0033] The second bridge arm branch includes a fifteenth switch unit and a sixteenth switch unit connected in series between the first DC power supply ports, and the fifteenth switch unit and the sixteenth switch unit are electrically connected to the midpoint of the second bridge arm.

[0034] The third bridge arm branch includes a seventeenth switch unit and an eighteenth switch unit connected in series between the first DC power supply ports. The seventeenth switch unit and the eighteenth switch unit are electrically connected to the midpoint of the third bridge arm.

[0035] The three-phase inverter bridge also includes: the nineteenth switching unit, the twentieth switching unit, the twenty-first switching unit, the twenty-second switching unit, the twenty-third switching unit, and the twenty-fourth switching unit;

[0036] The first terminal of the nineteenth switch unit is electrically connected to the midpoint of the first bridge arm, the second terminal of the nineteenth switch unit is electrically connected to the second terminal of the twentieth switch unit, and the first terminal of the twentieth switch unit is electrically connected to the neutral point.

[0037] The first terminal of the twenty-first switch unit is electrically connected to the midpoint of the second bridge arm, the second terminal of the twenty-first switch unit is electrically connected to the second terminal of the twenty-second switch unit, and the first terminal of the twenty-second switch unit is electrically connected to the neutral point.

[0038] The first terminal of the 23rd switch unit is electrically connected to the midpoint of the third bridge arm, the second terminal of the 23rd switch unit is electrically connected to the second terminal of the 24th switch unit, and the first terminal of the 24th switch unit is electrically connected to the neutral point.

[0039] In some possible implementations, the three-phase inverter bridge includes multiple switching units, each of which includes multiple semiconductor power switching units; the semiconductor power switching units include at least one of IGCT, IGBT, IEGT, and MOSFET.

[0040] In any given switching unit, multiple semiconductor power switching units are connected in series.

[0041] And / or, multiple semiconductor power switching units in any switching unit are connected in parallel with each other.

[0042] In some possible implementations, the semiconductor power switching unit in any switching unit includes an IGCT;

[0043] The three-level NPC inverter also includes a clamping circuit disposed between the first DC power supply ports.

[0044] In some possible implementations, at least one supporting capacitor includes a first supporting capacitor and a second supporting capacitor.

[0045] The first terminal of the first supporting capacitor is electrically connected to the positive terminal of the first DC power supply port, the second terminal of the first supporting capacitor and the first terminal of the second supporting capacitor are respectively electrically connected to the neutral point, and the second terminal of the second supporting capacitor is electrically connected to the negative terminal of the first DC power supply port.

[0046] In some possible implementations, the fractal connector module includes: a first winding, at least one second winding, and a third winding;

[0047] The first winding, at least one second winding, and the third winding are coupled together;

[0048] The first winding is electrically connected to the AC side of the three-level NPC inverter, at least one second winding is electrically connected to the AC side of at least one harmonic generating inverter, and the third winding is electrically connected to the AC output port.

[0049] In some possible implementations, the first winding includes a delta winding, any second winding includes a star winding or a delta winding, and the third winding includes a star winding or a delta winding.

[0050] In some possible implementations, the fractal connector module includes at least one fourth winding and at least one fifth winding;

[0051] The fourth winding is coupled to the corresponding fifth winding. The fourth winding is electrically connected to the AC side of the three-level NPC inverter. The fifth winding is electrically connected to the AC side of the corresponding harmonic generation inverter. The AC side of the three-level NPC inverter is electrically connected to the AC output port.

[0052] In some possible implementations, the fractal connector module includes: at least one connecting component;

[0053] The AC side of the three-level NPC inverter is electrically connected to the AC side of the corresponding harmonic generation inverter through a connecting component, so that the AC side of the three-level NPC inverter and the AC side of the corresponding harmonic generation inverter are connected in parallel.

[0054] The AC side of the three-level NPC inverter is electrically connected to the AC output port.

[0055] In some possible implementations, the fractal connector module includes at least one series transformer;

[0056] The first input terminal of the series transformer is electrically connected to the AC side of the three-level NPC inverter, the second input terminal of the series transformer is electrically connected to the AC side of the corresponding harmonic generation inverter, and the output terminal of the series transformer is electrically connected to the AC output port.

[0057] In some possible implementations, the series transformer includes: a first transformer, a second transformer, and a third transformer;

[0058] The first terminal of the first transformer is electrically connected to the first terminal of the AC side of the three-level NPC inverter; the second terminal of the first transformer is electrically connected to the first terminal of the AC output port; the third terminal of the first transformer is electrically connected to the neutral point or ground terminal; and the fourth terminal of the first transformer is electrically connected to the first terminal of the AC side of the harmonic generation inverter.

[0059] The first terminal of the second transformer is electrically connected to the second terminal of the AC side of the three-level NPC inverter; the second terminal of the second transformer is electrically connected to the second terminal of the AC output port; the third terminal of the second transformer is electrically connected to the neutral point or ground terminal; and the fourth terminal of the second transformer is electrically connected to the second terminal of the AC side of the harmonic generation inverter.

[0060] The first terminal of the third transformer is electrically connected to the third terminal of the AC side of the three-level NPC inverter. The second terminal of the third transformer is electrically connected to the third terminal of the AC output port. The third terminal of the third transformer is electrically connected to the neutral point or ground terminal. The fourth terminal of the third transformer is electrically connected to the third terminal of the AC side of the harmonic generation inverter.

[0061] In some possible implementations, the series transformer includes: a first single-phase winding, a second single-phase winding, a third single-phase winding, and a sixth winding;

[0062] The first single-phase winding, the second single-phase winding, and the third single-phase winding are electrically coupled to the sixth winding;

[0063] The first end of the first single-phase winding is electrically connected to the first end of the AC side of the three-level NPC inverter, and the second end of the first single-phase winding is electrically connected to the first end of the AC output port.

[0064] The first end of the second single-phase winding is electrically connected to the second end of the AC side of the three-level NPC inverter, and the second end of the second single-phase winding is electrically connected to the second end of the AC output port.

[0065] The first end of the third single-phase winding is electrically connected to the third end of the AC side of the three-level NPC inverter, and the second end of the third single-phase winding is electrically connected to the third end of the AC output port.

[0066] The sixth winding is electrically connected to the first terminal, the second terminal, and the third terminal of the AC side of the corresponding harmonic generator inverter.

[0067] In some possible implementations, the three-level NPC-type fractal converter further includes:

[0068] The first filter has its first end electrically connected to the AC side of the three-level NPC inverter, and its second end electrically connected to the first input end of the fractal connector module.

[0069] And / or, a second filter, the first end of which is electrically connected to the AC side of the corresponding harmonic generation inverter, and the second end of which is electrically connected to the corresponding second input end in the fractal connector module.

[0070] This application provides a three-level NPC-type fractal converter, which includes an inverter module, a harmonic generation module, and a fractal connector module. The inverter module includes a three-level NPC-type inverter, whose DC side is electrically connected to a first DC power supply port. The three-level NPC-type inverter outputs an AC signal, which includes a first harmonic signal within the higher harmonic range. The harmonic generation module includes at least one harmonic generation inverter, whose DC side is electrically connected to a corresponding second DC power supply port. The corresponding harmonic generation inverter outputs a corresponding second harmonic signal based on the first harmonic signal. The first input terminal of the fractal connector module is electrically connected to the AC side of the three-level NPC-type inverter. At least one second input terminal of the fractal connector module is electrically connected to the corresponding AC side of at least one harmonic generation inverter. The output terminal of the fractal connector module is electrically connected to an AC output port. The second harmonic signal is used to compensate for the first harmonic signal within the fractal connector module.

[0071] As described above, the harmonic generation inverter generates a second harmonic signal based on the first harmonic signal generated by the three-level NPC inverter, and outputs the second harmonic signal to the fractal connector module. This allows the second harmonic signal to compensate for the first harmonic signal within the fractal connector module, reducing or even eliminating harmonics in the output electrical signal from the converter to the AC output port. Therefore, based on the harmonic compensation functions of the harmonic generation module and the fractal connector module, the switching devices of the three-level NPC inverter can operate at a lower switching frequency with lower switching losses. This lower switching frequency operation allows for increased output capacity, significantly reducing the cost per unit capacity of the inverter while effectively ensuring the reliability and performance of the output signal. Attached Figure Description

[0072] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0073] Figure 1 This is a schematic diagram of the structure of a three-level NPC type fractal converter provided in one embodiment of this application;

[0074] Figure 2 This is a schematic diagram of the structure of a three-level NPC-type fractal converter provided in another embodiment of this application;

[0075] Figure 3 This is a schematic diagram of the structure of a three-level NPC inverter provided in one embodiment of this application;

[0076] Figure 4 This is a schematic diagram of the structure of a three-level NPC inverter provided in another embodiment of this application;

[0077] Figure 5 This is a schematic diagram of the structure of a switching unit provided in an embodiment of this application;

[0078] Figure 6 This is a schematic diagram of the structure of a switching unit provided in another embodiment of this application;

[0079] Figure 7 This is a schematic diagram of the structure of a semiconductor power switching unit provided in an embodiment of this application;

[0080] Figure 8 This is a schematic diagram of the structure of a semiconductor power switching unit provided in another embodiment of this application;

[0081] Figure 9This is a schematic diagram of the structure of a semiconductor power switching unit provided in another embodiment of this application;

[0082] Figure 10 This is a schematic diagram of the structure of a semiconductor power switching unit provided in another embodiment of this application;

[0083] Figure 11 This is a schematic diagram of the structure of a three-level NPC inverter provided in another embodiment of this application;

[0084] Figure 12 This is a schematic diagram of the structure of a fractal connector module provided in one embodiment of this application;

[0085] Figure 13 This is a schematic diagram of the structure of a fractal connector module provided in another embodiment of this application;

[0086] Figure 14 This is a schematic diagram of the structure of a fractal connector module provided in another embodiment of this application;

[0087] Figure 15 This is a schematic diagram of the structure of a fractal connector module provided in another embodiment of this application;

[0088] Figure 16 This is a schematic diagram of the structure of a series transformer provided in one embodiment of this application;

[0089] Figure 17 This is a schematic diagram of the structure of a series transformer provided in another embodiment of this application;

[0090] Figure 18 This is a schematic diagram of the structure of a three-level NPC type fractal converter provided in another embodiment of this application;

[0091] Figure 19 This is a schematic diagram of the structure of a harmonic generation inverter provided in one embodiment of this application. Detailed Implementation

[0092] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0093] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0094] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0095] It should be noted that the transistors in the embodiments of this application can be either N-type or P-type transistors. For N-type transistors, the on-state level is high and the off-state level is low. That is, when the gate of an N-type transistor is high, its first and second terminals are connected; when the gate of an N-type transistor is low, its first and second terminals are off. For P-type transistors, the on-state level is low and the off-state level is high. That is, when the control terminal of a P-type transistor is low, its first and second terminals are connected; when the control terminal of a P-type transistor is high, its first and second terminals are off. In specific implementations, the gate of each transistor is used as its control terminal. Furthermore, depending on the signal and type of the gate of each transistor, its first terminal can be used as the source and its second terminal as the drain, or vice versa. No distinction is made here. Additionally, the on-state and off-state levels in the embodiments of this invention are general terms. The on-state level refers to any level that enables the transistor to conduct, and the off-state level refers to any level that enables the transistor to turn off / become off.

[0096] In the embodiments of this application, the term "electrical connection" can refer to a direct electrical connection between two components, or it can refer to an electrical connection between two components via one or more other components.

[0097] In the embodiments of this application, the first node, the second node, and the third node are defined only for the convenience of describing the circuit structure, and the first node, the second node, and the third node are not actual circuit units.

[0098] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the embodiments provided in this application can be combined with each other without contradiction.

[0099] Before describing the technical solutions provided in the embodiments of this application, in order to facilitate understanding of the embodiments of this application, this application first specifically explains the problems existing in the related technologies:

[0100] As mentioned earlier, in existing AC / DC converter technology solutions, the switching frequency of converters based on three-level NPC inverters is relatively high, usually greater than 1kHz, which results in high losses and high heat generation of switching devices, leading to low overall output capacity of the converter and high cost per unit capacity of the converter.

[0101] The inventors of this application have discovered that, in traditional technical solutions, increasing the output capacity of the converter requires multiple three-level NPC converters connected in parallel, leading to a significant increase in overall cost. Alternatively, if traditional technical solutions increase output capacity by reducing the converter switching frequency and decreasing switching device losses, the three-level NPC inverter will generate significant high-order harmonic components. Larger inductor-capacitor filters are needed to passively filter out these high-order harmonic components. Since the harmonic components generated at lower switching frequencies are large, larger passive filters are required, resulting in a rapid increase in cost and also affecting the converter's output performance.

[0102] As a result, current three-level NPC inverters have a high switching frequency, leading to high losses in switching devices, high heat generation, low overall output capacity, and high cost per unit capacity. Therefore, how to effectively reduce the switching frequency of three-level NPC inverters and improve the overall output capacity of the inverter has become a technical problem that urgently needs to be solved by those skilled in the art.

[0103] In view of the above, in order to solve the problems of the prior art, this application provides a three-level NPC type fractal converter. It should be noted that the embodiments provided in this application are not intended to limit the scope of this application.

[0104] The three-level NPC type fractal converter 100 provided in the embodiments of this application will be introduced first below. Figure 1 This is a schematic diagram of the structure of a three-level NPC-type fractal converter 100 provided in one embodiment of this application. Figure 1 As shown, this application embodiment provides a three-level NPC type fractal converter 100, which includes:

[0105] The inverter module 10 includes a three-level NPC type inverter 11. The DC side of the three-level NPC type inverter 11 is electrically connected to the first DC power supply port. The three-level NPC type inverter 11 is used to output an AC signal, which includes the first harmonic signal in the higher harmonic range.

[0106] The harmonic generation module 20 includes at least one harmonic generation inverter 21. The DC side of any harmonic generation inverter 21 is electrically connected to the corresponding second DC power supply port. The corresponding harmonic generation inverter 21 is used to output a corresponding second harmonic signal according to the first harmonic signal.

[0107] The fractal connector module 30 has a first input terminal electrically connected to the AC side of the three-level NPC inverter 11, at least one second input terminal of the fractal connector module 30 electrically connected to the AC side of at least one harmonic generating inverter 21, and an output terminal of the fractal connector module 30 electrically connected to the AC output port.

[0108] The second harmonic signal is used to compensate for the first harmonic signal within the fractal connector module 30.

[0109] Specifically, for example, the three-level NPC inverter 11 includes multiple switching units. By reducing the switching frequency of each switching unit, the device losses of the switching units of the three-level NPC inverter 11 can be reduced, thereby enabling the three-level NPC inverter 11 to output greater power.

[0110] In this embodiment, the switching devices in the three-level NPC inverter 11 operate at a relatively low switching frequency, typically less than 500Hz, 100Hz, or 150Hz, but can also be 200Hz, 250Hz, 300Hz, 350Hz, 400Hz, or 450Hz, to generate a 50Hz fundamental voltage and fundamental current. After the switching frequency of the switching unit decreases, the three-level NPC inverter 11 outputs an AC signal, which includes the fundamental signal and the first harmonic signal in the higher harmonic range.

[0111] By reducing the switching frequency of the switching devices in the three-level NPC inverter 11, device losses are reduced, thereby enabling the output of greater power. Compared with traditional technical solutions, the capacity can be increased by several times, which significantly reduces the cost per unit capacity of the three-level NPC inverter 11 and improves economic efficiency.

[0112] The harmonic generation module 20 described above may include one or more harmonic generation inverters 21. For example, the harmonic generation inverter 21 may be a two-level inverter topology, a three-level inverter topology, a five-level inverter topology, a multi-level inverter topology (number of levels > 5, seven levels, nine levels, etc.), a modular multi-level inverter topology, or a cascaded H-bridge inverter topology, etc., or it may be a series-parallel connection of various inverters or a series-parallel connection of switching devices.

[0113] In this embodiment, the harmonic generation inverter 21 can be used only to generate the second harmonic signal within the corresponding higher harmonic range, and is not used to generate the fundamental signal. Therefore, the capacity of the harmonic generation inverter 21 is very small, typically less than one-tenth the capacity of the three-level NPC inverter 11, resulting in lower manufacturing costs. Compared to conventional technologies that use multiple sets of three-level NPC inverters 11 and passive filters, this application uses the harmonic generation inverter 21 to increase the overall capacity of the converter, achieving lower costs.

[0114] In one example, all switching devices in the harmonic generation inverter 21 operate at a high switching frequency, typically greater than 1500Hz. The harmonic generation inverter 21 monitors the first harmonic signal component generated by the three-level NPC inverter 11 in real time and provides it as a control command value to the controller of the harmonic generation inverter 21, thereby controlling the output waveform of the harmonic generation inverter 21 to be the corresponding second harmonic signal that is opposite to that of the three-level NPC inverter 11.

[0115] The first input terminal of the fractal connector module 30 is electrically connected to the AC side of the three-level NPC inverter 11, and at least one second input terminal of the fractal connector module 30 is electrically connected to the corresponding AC side of at least one harmonic generating inverter 21. The output terminal of the fractal connector module 30 is electrically connected to the AC output port. The second harmonic signal can compensate for the first harmonic signal within the fractal connector module 30.

[0116] In this way, the harmonic voltage and harmonic current generated by the three-level NPC inverter 11 and the harmonic generating inverter 21 are canceled out by the fractal connector module 30, so that the voltage and current output to the AC output port of the fractal connector module 30 are mainly fundamental voltage and fundamental current components. The fractal connector module 30 achieves the effect of canceling out harmonic voltage and harmonic current components.

[0117] In this embodiment, both the first and second DC power supply ports include positive and negative connection terminals. The first and second DC power supply ports are DC power supply ports that can be connected to equipment with DC power supply ports, such as rectifiers, energy storage devices, and MPPT (Maximum Power Point Tracking) devices, and are responsible for transmitting DC power. The AC output port includes three connection terminals: phase A, phase B, and phase C.

[0118] In a three-level NPC-type fractal converter 100 according to an embodiment of this application, the inverter module 10 and the harmonic generation module 20 respectively construct the power frequency fundamental wave and high-frequency harmonics, and construct a sinusoidal voltage waveform through fractal coupling on the AC side. The main function of the inverter module 10 is to output the fundamental voltage / current and adjust its amplitude and phase angle to achieve AC / DC power conversion. The main function of the harmonic generation module 20 is to output harmonic voltage or harmonic current opposite to that of the inverter module 10 to compensate for the harmonic components generated by the inverter module 10. The output waveforms of the inverter module 10 and the harmonic generation module 20 are coupled together through the fractal connector module 30 to achieve harmonic cancellation and construct a standard sinusoidal waveform.

[0119] As described above, the harmonic generation inverter 21 in the harmonic generation module 20 generates a second harmonic signal based on the first harmonic signal generated by the three-level NPC type inverter 11 in the inverter module 10, and outputs the second harmonic signal to the fractal connector module 30. This allows the first harmonic signal to be compensated by the second harmonic signal within the fractal connector module 30, thereby reducing or even eliminating the harmonics of the output electrical signal from the converter to the AC output port.

[0120] Thus, in a three-level NPC type fractal converter 100 according to an embodiment of this application, there is no need to increase the output capacity or filter out harmonics by additionally setting up multiple sets of costly three-level NPC type inverters 11 or passive filters. Through the harmonic compensation effect based on the harmonic generation module 20 and the fractal connector module 30, the switching devices of the three-level NPC type inverter 11 in the inverter module 10 can directly operate at a lower switching frequency, resulting in low switching device losses. In this way, by operating the three-level NPC type inverter 11 at a low switching frequency, the output capacity of the converter can be increased, thereby significantly reducing the cost per unit capacity of the inverter, while effectively ensuring the reliability and performance of the output signal.

[0121] Please continue reading Figure 1 Optionally, according to some embodiments of this application, the number of harmonic generation inverters 21 in the harmonic generation module 20 is 1;

[0122] The alternating current signal includes n first harmonic signals corresponding to n higher harmonic intervals, where n is greater than or equal to 1 and n is a positive integer.

[0123] The harmonic generation inverter 21 is used to output n second harmonic signals, and the n second harmonic signals correspond one-to-one with the n first harmonic signals.

[0124] As an example, see further. Figure 1 The harmonic generation module 20 includes a harmonic generation inverter 21, which generates a corresponding second harmonic signal based on the first harmonic signal generated by the three-level NPC inverter 11. The fundamental signal and the first harmonic signal generated by the three-level NPC inverter 11 are output to the fractal connector module 30, and the corresponding second harmonic signal generated by the harmonic generation module 20 is also output to the fractal connector module 30.

[0125] Taking n=1 as an example, if the first harmonic signal is, for example, the 3rd harmonic signal, then the corresponding second harmonic signal generated by the harmonic generation inverter 21 is also the 3rd harmonic signal. Taking n=3 as an example, if the AC signal generated by the three-level NPC inverter 11 includes three first harmonic signals: the 3rd harmonic signal, the 5th harmonic signal, and the 7th harmonic signal, then the number of corresponding second harmonic signals generated by the harmonic generation inverter 21 is also 3, including the 3rd harmonic signal, the 5th harmonic signal, and the 7th harmonic signal.

[0126] In this way, the second harmonic signal can compensate for the corresponding first harmonic signal within the fractal connector module 30. Because the harmonic signal is compensated, the losses caused by the harmonic signals in the three-level NPC type inverter 11 are also reduced, thereby increasing the output power and output capacity of the three-level NPC type fractal converter 100. Therefore, this embodiment achieves both a reduction in the switching frequency of the three-level NPC type fractal converter 100 and an increase in the converter's output capacity.

[0127] Figure 2 This is a schematic diagram of the structure of a three-level NPC-type fractal converter 100 provided in another embodiment of this application. Figure 2 As shown, optionally, according to some embodiments of this application, the number of harmonic generation inverters 21 in the harmonic generation module 20 is n, where n is greater than 1 and n is a positive integer;

[0128] The AC sides of the n harmonic generation inverters 21 are electrically connected to the n second input terminals of the fractal connector module 30, respectively.

[0129] The switching frequency of the switching device of the i-th harmonic generator inverter 21 is greater than the switching frequency of the switching device of the (i-1)-th harmonic generator inverter 21, 1 < i ≤ n, where i is a positive integer;

[0130] The alternating current signal includes n first harmonic signals corresponding to n higher harmonic intervals. The n harmonic generator inverter 21 is used to output n second harmonic signals, and the n second harmonic signals correspond one-to-one with the n first harmonic signals.

[0131] The first harmonic generating inverter 21 to the nth harmonic generating inverter 21 can be a two-level inverter topology, a three-level inverter topology, a five-level inverter topology, a multi-level inverter topology (number of levels > 5, seven-level, nine-level, etc.), a modular multi-level inverter topology, or a cascaded H-bridge inverter topology, etc., without strict limitations. The switching frequency of the switching devices in the first harmonic generating inverter 21 to the nth harmonic generating inverter 21 increases with the inverter number, and the switching frequency is higher than that of the harmonic generating inverter 21 with a smaller number. It is used to assist the harmonic generating inverter 21 with a smaller number and to compensate for the higher-order harmonic voltages and harmonic currents generated by the three-level NPC type inverter 11, which are difficult for the harmonic generating inverter 21 with a smaller number to compensate.

[0132] For example, let's take an n=3 value as an example. See [link / reference] Figure 2 The harmonic generation module 20 includes three harmonic generation inverters 21, which are respectively connected to the three second input terminals of the fractal connector module 30. The switching frequency of the switching device of the third harmonic generation inverter 21 is higher than that of the second harmonic generation inverter 21, which in turn is higher than that of the first harmonic generation inverter 21. Therefore, the third harmonic generation inverter 21 is used to compensate for the highest-order harmonic signal, the first harmonic generation inverter 21 is used to compensate for the lowest-order harmonic signal, and the second harmonic generation inverter 21 is used to compensate for the intermediate-order harmonic signals.

[0133] Taking n=3 as an example, the AC signal generated by the three-level NPC inverter 11 includes three first harmonic signals: the 3rd harmonic signal, the 5th harmonic signal, and the 7th harmonic signal. The third harmonic generating inverter 21 is used to generate the corresponding second harmonic signal of the 7th harmonic interval based on the first harmonic signal of the 7th harmonic interval. The second harmonic generating inverter 21 is used to generate the corresponding second harmonic signal of the 5th harmonic interval based on the first harmonic signal of the 5th harmonic interval. The first harmonic generating inverter 21 is used to generate the corresponding second harmonic signal of the 3rd harmonic interval based on the first harmonic signal of the 3rd harmonic interval.

[0134] It should be added that, in comparison Figure 1 and Figure 2 In both examples, when the first harmonic signal generated by the three-level NPC inverter 11 is the same, Figure 2The second harmonic signal generated by the inverter 21 with multiple harmonic generation and Figure 1 When only one harmonic generator inverter 21 is used, the total amount of the second harmonic signal generated is the same. Therefore, when multiple harmonic generator inverters 21 are used, the total capacity of n harmonic generator inverters 21 is the same as that of using only one harmonic generator inverter 21. However, since the capacity of a single harmonic generator inverter 21 is reduced, the manufacturing cost of a single harmonic generator inverter 21 is significantly reduced. Therefore, using multiple harmonic generator inverters 21 results in lower cost.

[0135] Optionally, according to some embodiments of this application, the switching frequency of any harmonic generating inverter 21 is greater than the switching frequency of the three-level NPC type inverter 11.

[0136] In this embodiment, the switching frequency of any harmonic generating inverter 21 is greater than the switching frequency of the three-level NPC inverter 11. All switching devices in the three-level NPC inverter 11 operate at a lower switching frequency, typically less than 500Hz, thereby generating a fundamental voltage and current of 50Hz. All switching devices in the harmonic generating inverter 21 operate at a higher switching frequency, typically greater than 1500Hz.

[0137] Thus, by reducing the switching frequency of the switching devices in the three-level NPC inverter 11, device losses are reduced, thereby enabling the output of greater power. The harmonic generation inverter 21 is only used to generate the second harmonic signal within the corresponding higher harmonic range and is not used to generate the fundamental signal. Therefore, the capacity of the harmonic generation inverter 21 is very small, resulting in a lower manufacturing cost. This significantly reduces the cost per unit capacity of the converter and improves economic efficiency.

[0138] Optionally, according to some embodiments of this application, such as Figure 3 or Figure 4 As shown, the AC side of the three-level NPC inverter 11 includes three single-phase AC output terminals (e.g., phase A, phase B, and phase C single-phase AC output terminals).

[0139] The three-level NPC type inverter 11 includes at least one supporting capacitor and a three-phase inverter bridge. The three-phase inverter bridge includes a first bridge arm branch, a second bridge arm branch and a third bridge arm branch disposed between the first DC power supply ports.

[0140] The first bridge arm branch includes the midpoint A of the first bridge arm, the second bridge arm branch includes the midpoint B of the second bridge arm, and the third bridge arm branch includes the midpoint C of the third bridge arm. The midpoints A, B, and C of the first bridge arm are electrically connected to the three single-phase AC output terminals respectively.

[0141] At least one supporting capacitor is connected in series between the first DC power supply ports.

[0142] Optionally, more specifically, such as Figure 3 As shown, the three-level NPC inverter 11 is a three-level I-type NPC structure;

[0143] The first bridge arm branch includes a first switch unit 111, a second switch unit 112, a third switch unit 113 and a fourth switch unit 114 connected in series between the first DC power supply ports. The second switch unit 112 and the third switch unit 113 are electrically connected to the midpoint A of the first bridge arm.

[0144] The second bridge arm branch includes a fifth switch unit 115, a sixth switch unit 116, a seventh switch unit 117 and an eighth switch unit 118 connected in series between the first DC power supply ports. The sixth switch unit 116 and the seventh switch unit 117 are electrically connected to the midpoint B of the second bridge arm.

[0145] The third bridge arm branch includes a ninth switch unit 119, a tenth switch unit 120, an eleventh switch unit 121 and a twelfth switch unit 122 connected in series between the first DC power supply ports. The tenth switch unit 120 and the eleventh switch unit 121 are electrically connected to the midpoint C of the third bridge arm.

[0146] The three-phase inverter bridge also includes: first diode D1, second diode D2, third diode D3, fourth diode D4, fifth diode D5 and sixth diode D6;

[0147] The cathode of the first diode D1 is electrically connected to the first node N1, and the anode of the first diode D1 is electrically connected to the neutral point N. The cathode of the second diode D2 is electrically connected to the neutral point N, and the anode of the second diode D2 is electrically connected to the second node N2. The cathode of the third diode D3 is electrically connected to the third node N3, and the anode of the third diode D3 is electrically connected to the neutral point N. The cathode of the fourth diode D4 is electrically connected to the neutral point N, and the anode of the fourth diode D4 is electrically connected to the fourth node N4. The cathode of the fifth diode D5 is electrically connected to the fifth node N5, and the anode of the fifth diode D5 is electrically connected to the neutral point N. The cathode of the sixth diode D6 is electrically connected to the neutral point N, and the anode of the sixth diode D6 is electrically connected to the sixth node N6.

[0148] The first node N1 is the common point of the first switch unit 111 and the second switch unit 112; the second node N2 is the common point of the third switch unit 113 and the fourth switch unit 114; the third node N3 is the common point of the fifth switch unit 115 and the sixth switch unit 116; the fourth node N4 is the common point of the seventh switch unit 117 and the eighth switch unit 118; the fifth node N5 is the common point of the ninth switch unit 119 and the tenth switch unit 120; and the sixth node N6 is the common point of the eleventh switch unit 121 and the twelfth switch unit 122.

[0149] When the three-level NPC inverter 11 is a three-level type I NPC structure, the switching devices included in the switching unit of the three-level NPC inverter 11 operate at a low switching frequency, usually less than 500Hz (typical values ​​are 50Hz, 100Hz, 150Hz, and can also be 200Hz, 250Hz, 300Hz, 350Hz, 400Hz or 450Hz). The main purpose is to generate a 50Hz fundamental voltage and fundamental current, thereby reducing switching losses and increasing output capacity by operating at a low frequency.

[0150] In practical operation, the control terminals of the first switch unit 111, the second switch unit 112, the third switch unit 113, the fourth switch unit 114, the fifth switch unit 115, the sixth switch unit 116, the seventh switch unit 117, the eighth switch unit 118, the ninth switch unit 119, the tenth switch unit 120, the eleventh switch unit 121, and the twelfth switch unit 122 are all electrically connected to the corresponding controller. The pulse width modulation signal output by the controller controls the conduction and cutoff of each of the above switch units, thereby enabling the three-level NPC inverter 11 to output the corresponding AC signal.

[0151] It should be understood that, considering the diversity of existing inverter bridge driving methods, the specific driving principles of the first switching unit 111, the second switching unit 112, the third switching unit 113 and the fourth switching unit 114, the fifth switching unit 115, the sixth switching unit 116, the seventh switching unit 117 and the eighth switching unit 118, as well as the ninth switching unit 119, the tenth switching unit 120, the eleventh switching unit 121 and the twelfth switching unit 122 in the three-phase inverter bridge will not be explained in detail in this embodiment.

[0152] Optionally, more specifically, such as Figure 4 As shown, the three-level NPC inverter 11 is a three-level T-type NPC structure;

[0153] The first bridge arm branch includes a thirteenth switch unit 123 and a fourteenth switch unit 124 connected in series between the first DC power supply ports. The thirteenth switch unit 123 and the fourteenth switch unit 124 are electrically connected to the midpoint A of the first bridge arm.

[0154] The second bridge arm branch includes a fifteenth switch unit 125 and a sixteenth switch unit 126 connected in series between the first DC power supply ports. The fifteenth switch unit 125 and the sixteenth switch unit 126 are electrically connected to the midpoint B of the second bridge arm.

[0155] The third bridge arm branch includes a seventeenth switch unit 127 and an eighteenth switch unit 128 connected in series between the first DC power supply ports. The seventeenth switch unit 127 and the eighteenth switch unit 128 are electrically connected to the midpoint C of the third bridge arm.

[0156] The three-phase inverter bridge also includes: the nineteenth switching unit 129, the twentieth switching unit 130, the twenty-first switching unit 131, the twenty-second switching unit 132, the twenty-third switching unit 133, and the twenty-fourth switching unit 134;

[0157] The first end of the nineteenth switch unit 129 is electrically connected to the midpoint A of the first bridge arm, the second end of the nineteenth switch unit 129 is electrically connected to the second end of the twentieth switch unit 130, and the first end of the twentieth switch unit 130 is electrically connected to the neutral point N.

[0158] The first end of the twenty-first switch unit 131 is electrically connected to the midpoint B of the second bridge arm, the second end of the twenty-first switch unit 131 is electrically connected to the second end of the twenty-second switch unit 132, and the first end of the twenty-second switch unit 132 is electrically connected to the neutral point N.

[0159] The first end of the twenty-third switch unit 133 is electrically connected to the midpoint C of the third bridge arm, the second end of the twenty-third switch unit 133 is electrically connected to the second end of the twenty-fourth switch unit 134, and the first end of the twenty-fourth switch unit 134 is electrically connected to the neutral point N.

[0160] When the three-level NPC inverter 11 is a three-level T-type NPC structure, the switching devices in the three-level NPC inverter 11 operate at a low switching frequency, usually less than 500Hz (typical values ​​are 50Hz, 100Hz, 150Hz, and can also be 200Hz, 250Hz, 300Hz, 350Hz, 400Hz or 450Hz). The main purpose is to generate a 50Hz fundamental voltage and fundamental current, thereby reducing switching losses and increasing output capacity through low-frequency switching operation.

[0161] In practical operation, the control terminals of the thirteenth switch unit 123, fourteenth switch unit 124, fifteenth switch unit 125, sixteenth switch unit 126, seventeenth switch unit 127, eighteenth switch unit 128, nineteenth switch unit 129, twentieth switch unit 130, twenty-first switch unit 131, twenty-second switch unit 132, twenty-third switch unit 133, and twenty-fourth switch unit 134 are all electrically connected to the corresponding controller. The pulse width modulation signal output by the controller controls the on and off states of each switch unit, thereby enabling the three-level NPC inverter 11 to output the corresponding AC signal. It should be understood that, considering the diversity of existing inverter bridge driving methods, the specific driving principle of the switch units in the three-phase inverter bridge will not be elaborated in this embodiment.

[0162] Optionally, according to some embodiments of this application, in conjunction with Figure 3 or Figure 4 As shown, the three-phase inverter bridge includes multiple switching units, and each of the multiple switching units includes multiple semiconductor power switching units 110; the semiconductor power switching unit 110 includes at least one of IGCT, IGBT, IEGT and MOSFET.

[0163] In any given switching unit, multiple semiconductor power switching units 110 are connected in series.

[0164] And / or, multiple semiconductor power switching units 110 in any switching unit are connected in parallel with each other.

[0165] In practical applications, combined with Figure 3 or Figure 4 As shown, when the three-level NPC inverter 11 is a three-level I-type NPC structure, or when the three-level NPC inverter 11 is a three-level T-type NPC structure, the three-phase inverter bridge includes multiple switching units. The multiple switching units are set with different connection methods to form different three-level NPC structures.

[0166] Each of the multiple switching units includes multiple semiconductor power switching units 110. Each semiconductor power switching unit 110 may consist of at least one switching device and a freewheeling diode connected in reverse parallel. When the switching device is turned on, the current direction from positive to negative is from the first terminal to the second terminal of the corresponding switching unit. Furthermore, each semiconductor power switching unit 110 may also include other auxiliary devices such as resistors and capacitors according to actual needs. This application does not strictly limit the internal structure of the semiconductor power switching units.

[0167] The aforementioned switching devices can be selected from integrated gate-commutated thyristors (IGCT), insulated gate bipolar transistors (IGBT), injection-enhanced gate transistors (IEGT), or metal-oxide-semiconductor field-effect transistors (MOSFET), etc.

[0168] In some embodiments, the above-mentioned switching unit may include multiple semiconductor power switching units 110 connected in series, in parallel, or in a combination of series and parallel. The connection methods within different switching units may be the same or different, depending on the actual circuit requirements, and are not strictly limited here.

[0169] As an example, such as Figure 5 As shown, taking a certain switching unit as an example, the switching unit includes multiple semiconductor power switching units 110 connected in series. Because the multiple semiconductor power switching units 110 are connected in series, the high voltage withstand capability of the switching unit can be enhanced. Alternatively, as another example, such as... Figure 6 As shown, taking a certain switching unit as an example, the switching unit includes multiple semiconductor power switching units 110 connected in parallel. Since multiple semiconductor power switching units 110 are connected in parallel, the current carrying capacity of the switching unit can be enhanced.

[0170] The following is combined Figures 7 to 10 The following describes some specific structural examples of the semiconductor power switching unit 110.

[0171] In some examples, such as Figure 7 As shown, the semiconductor power switching unit 110 includes a main switch S1, an auxiliary switch S2, and a module capacitor C. MS Module resistor R MS And ports. The ports of the semiconductor power switch unit 110 include both positive and negative terminals.

[0172] In specific connections, the module resistor R MS The first terminal is connected to the module capacitor C MS The first terminal is connected to the module resistor R. MS The second terminal is connected to the module capacitor C MS The second terminal is connected, and the first terminal of the auxiliary switch S2 is connected to the module capacitor C. MS The first terminal of the auxiliary switch S2 is connected to the first terminal of the main switch S1, and the second terminal of the main switch S1 is connected to the module capacitor C.MS The second end is connected. The first end of the main switch S1 serves as the positive terminal of the semiconductor power switch unit 110, and the second end of the main switch S1 serves as the negative terminal of the semiconductor power switch unit 110.

[0173] The main switch S1 can be selected from IGCT, IGBT, IEGT, or MOSFET, etc. The auxiliary switch S2 can be selected from IGBT, IEGT, MOSFET, or diode, etc. The main switch S1 can have a larger capacity than the auxiliary switch S2. For example, the main switch S1 can be selected from IGCT, and the auxiliary switch S2 can be selected from IGBT.

[0174] The above module resistor R MS It can be used to perform static voltage equalization; module capacitor C MS This can be used to achieve dynamic pressure equalization. In some possible embodiments, Figure 7 R in MS Alternatively, this setting can be omitted. Furthermore, corresponding anti-parallel diodes can be installed at both ends of the main switch S1 and the auxiliary switch S2 for freewheeling.

[0175] In other examples, such as Figure 8 As shown, the semiconductor power switching unit includes a switch S and a module capacitor C. MS Module resistor R MS The semiconductor power switch unit 110 has two terminals: a diode (D), a Zener diode (Dz), and a port. The port of the semiconductor power switch unit 110 includes both positive and negative terminals.

[0176] In the specific connection, the cathode of the Zener diode Dz and the module resistor R... MS The first terminal is connected to the module capacitor C respectively MS The first connection is between the anode of the Zener diode Dz and the module resistor R. MS The second terminal is connected to the module capacitor C respectively. MS The second terminal is connected, with the cathode of diode D connected to module capacitor C. MS The first terminal of diode D is connected to the first terminal of switch S, and the second terminal of switch S is connected to the module capacitor C. MS The second end is connected. The first end of switch S serves as the positive terminal of the semiconductor power switch unit 110, and the second end of switch S serves as the negative terminal of the semiconductor power switch unit 110.

[0177] The switch S can be selected from IGCT, IGBT, IEGT, or MOSFET, etc. The module resistor R mentioned above... MS It can be used to perform static voltage equalization; module capacitor C MSThis can be used for dynamic voltage equalization; the Zener diode Dz can be used for voltage regulation; and the diode D can be used to assist in voltage equalization control. In some possible embodiments, Figure 8 R in MS Alternatively, this setting can be omitted. Also, corresponding anti-parallel diodes can be set at both ends of switch S for freewheeling.

[0178] In some other examples, such as Figure 9 As shown, the semiconductor power switching unit 110 includes a switch S and a buffer capacitor C. S Buffer resistor R S The semiconductor power switch unit 110 has two terminals: a positive terminal and a negative terminal.

[0179] In the specific connection, the buffer capacitor C S The first terminal is connected to the buffer resistor R S The first end is connected to the buffer capacitor C. S The second terminal is connected to the buffer resistor R S The second terminal is connected, and the first terminal of switch S is connected to the buffer capacitor C. S The first terminal is connected, and the second terminal of switch S is connected to the buffer capacitor C. S The second end is connected. The first end of switch S serves as the positive terminal of the semiconductor power switch unit 110, and the second end of switch S serves as the negative terminal of the semiconductor power switch unit 110.

[0180] The switch S can be selected from IGCT, IGBT, IEGT, or MOSFET, etc. The aforementioned buffer capacitor C... S It can be used to provide buffer protection; the buffer resistor R S This can be used for static voltage equalization and current limiting protection. Additionally, corresponding anti-parallel diodes can be installed at both ends of switch S for freewheeling.

[0181] In some other examples, such as Figure 10 As shown, the semiconductor power switching unit 110 includes a switch S and a buffer capacitor C. S Buffer resistor R S Diode D, static voltage equalization resistor R d The semiconductor power switch unit 110 has two terminals: a positive terminal and a negative terminal.

[0182] In the specific connection, the static voltage equalization resistor R d The first terminal and the buffer resistor R S The first terminal is connected to the buffer resistor R. S The first terminal is connected to the buffer capacitor C S The first terminal is connected to the static equalizing resistor R. d The second terminal is connected to the buffer capacitor CS The second terminal is connected, with the anode of diode D connected to the buffer resistor R. S The first terminal is connected, with the cathode of diode D connected to the buffer resistor R. S The second terminal of switch S is connected to the anode of diode D, and the second terminal of switch S is connected to the buffer capacitor C. S The second end is connected. The first end of switch S serves as the positive terminal of the semiconductor power switch unit 110, and the second end of switch S serves as the negative terminal of the semiconductor power switch unit 110.

[0183] The switch S can be selected from IGCT, IGBT, IEGT, or MOSFET, etc. The aforementioned buffer capacitor C... S It can be used to provide buffer protection; the buffer resistor R S It can be used to provide current limiting protection; static equalizing resistor R d It can be used for static voltage equalization. Furthermore, corresponding anti-parallel diodes can be installed at both ends of switch S for freewheeling.

[0184] It should be noted that when multiple semiconductor power switch units 110 are connected in series, the positive terminal in the port of the current semiconductor power switch unit 110 is used to connect with the negative terminal in the port of the adjacent previous semiconductor power switch unit 110, and the negative terminal in the port of the current semiconductor power switch unit 110 is used to connect with the positive terminal in the port of the adjacent next semiconductor power switch unit 110.

[0185] When multiple semiconductor power switch units 110 are connected in parallel, the positive terminal of the current semiconductor power switch unit 110 is used to connect to the positive terminal of the adjacent preceding semiconductor power switch unit 110, and the negative terminal of the current semiconductor power switch unit 110 is used to connect to the negative terminal of the adjacent following semiconductor power switch unit 110. The direction from the positive terminal to the negative terminal of any semiconductor power switch unit 110 is consistent with the direction from the first end to the second end of the switch unit it belongs to.

[0186] Optionally, according to some embodiments of this application, such as Figure 11 As shown, the semiconductor power switch unit 110 in any of the switching units includes an IGCT;

[0187] The three-level NPC inverter 11 also includes a clamping circuit disposed between the first DC power supply ports.

[0188] Combination Figure 11As shown, the clamping circuit includes a first anode reactance Lbuf1, a first clamping diode Dbuf1, a first clamping resistor Rbuf1 and a first clamping capacitor Cbuf1, as well as a second anode reactance Lbuf2, a second clamping diode Dbuf2, a second clamping resistor Rbuf2 and a second clamping capacitor Cbuf2.

[0189] The first terminal of the first anode reactor Lbuf1 is connected to the positive terminal of the corresponding first DC power supply port. The second terminal of the first anode reactor Lbuf1 is connected to the anode of the first clamping diode Dbuf1. The anode of the first clamping diode Dbuf1 is connected to the first terminal of the first clamping capacitor Cbuf1. The second terminal of the first clamping capacitor Cbuf1 is connected to the neutral point N. The first terminal of the first clamping resistor Rbuf1 is connected to the first terminal of the first anode reactor Lbuf1. The second terminal of the first clamping resistor Rbuf1 is electrically connected to the cathode of the first clamping diode Dbuf1.

[0190] The first terminal of the second anode reactor Lbuf2 is connected to the negative terminal of the corresponding first DC power supply port. The second terminal of the second anode reactor Lbuf2 is connected to the cathode of the second clamping diode Dbuf2. The cathode of the second clamping diode Dbuf2 is connected to the first terminal of the second clamping capacitor Cbuf2. The second terminal of the second clamping capacitor Cbuf2 is connected to the neutral point N. The first terminal of the second clamping resistor Rbuf2 is connected to the first terminal of the second anode reactor Lbuf2. The second terminal of the second clamping resistor Rbuf2 is electrically connected to the anode of the second clamping diode Dbuf2.

[0191] In this way, the clamping circuit described above is used to limit the rate of change of current of the semiconductor power switching unit 110 when it is turned on, and to limit the oscillation amplitude of the AC side output voltage of the three-phase inverter bridge, thereby effectively realizing the clamping protection of the circuit elements.

[0192] It should be noted that the clamping circuit described above is used to protect the IGCT device, and its topology is only an example topology; other topologies are also possible. In some embodiments, if the IGCT is not included in the switching unit, the clamping circuit may not be provided in the three-level NPC inverter 11. Therefore, in the circuit topology of the three-level NPC inverter 11, whether or not a clamping circuit is provided can be flexibly selected based on the characteristics of the three-phase inverter bridge in the actual cascaded unit, and this embodiment does not impose strict limitations on it.

[0193] It should also be noted that, Figure 11The clamping circuit described above is based on the case where the three-level NPC inverter 11 has a three-level I-type NPC structure. In some other embodiments, when the three-level NPC inverter 11 has a three-level T-type NPC structure, a similar clamping circuit can also be set between the first DC power supply ports to clamp and protect the circuit elements.

[0194] Optionally, according to some embodiments of this application, such as Figure 3 , Figure 4 or Figure 11 As shown, in the three-level NPC type inverter 11, at least one supporting capacitor includes a first supporting capacitor Cbus1 and a second supporting capacitor Cbus2.

[0195] The first terminal of the first supporting capacitor Cbus1 is electrically connected to the positive terminal of the first DC power supply port, the second terminal of the first supporting capacitor Cbus1 and the first terminal of the second supporting capacitor Cbus2 are electrically connected to the neutral point, and the second terminal of the second supporting capacitor Cbus2 is electrically connected to the negative terminal of the first DC power supply port.

[0196] In a specific implementation, the first supporting capacitor Cbus1 and the second supporting capacitor Cbus2 can be composed of a single capacitor. In other embodiments, the first supporting capacitor Cbus1 and the second supporting capacitor Cbus2 can also be composed of multiple capacitors connected in series and parallel. The first supporting capacitor Cbus1 and the second supporting capacitor Cbus2 are used to stabilize the DC bus voltage provided by the corresponding first DC power supply port and avoid sudden changes in the DC bus voltage.

[0197] Optionally, according to some embodiments of this application, such as Figure 12 As shown, the fractal connector module 30 includes: a first winding 311, at least one second winding 312, and a third winding 313;

[0198] The first winding 311, at least one second winding 312, and the third winding 313 are coupled together;

[0199] The first winding 311 is electrically connected to the AC side of the three-level NPC inverter 11, at least one second winding 312 is electrically connected to the AC side of at least one harmonic generating inverter 21, and the third winding 313 is electrically connected to the AC output port.

[0200] For example, the first winding 311 can be a star-connected winding or a delta-connected winding, the second winding 312 can be a star-connected winding or a delta-connected winding, and the third winding 313 can be a star-connected winding or a delta-connected winding.

[0201] In practice, after the switching frequency of the switching unit in the three-level NPC inverter 11 is reduced, the three-level NPC inverter 11 generates the first harmonic signal in the higher harmonic range. The fundamental signal and the first harmonic signal generated by the three-level NPC inverter 11 are output to the first winding 311, and the harmonic generation inverter 21 generates the corresponding second harmonic signal according to the first harmonic signal, which is then output to the second winding 312.

[0202] Since the waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal compensates for the first harmonic signal, thereby reducing the harmonic signal at the AC output port and reducing the loss caused by the harmonic signal. This enhances the maximum power output capability of the three-level NPC fractal converter 100 and increases the output capacity of the three-level NPC fractal converter 100. The final generated fundamental signal is output to the AC output port through the third winding 313.

[0203] When the harmonic generation module 20 includes multiple harmonic generation inverters 21, the fractal connector module 30 includes the same number of second windings 312. The multiple second windings 312 are connected to the corresponding harmonic generation inverters 21 and coupled to other windings. This allows the second harmonic signals of different higher harmonic ranges generated by different harmonic generation inverters 21 to be introduced into the fractal connector module 30, thereby enabling the compensation of the first harmonic signals of different higher harmonic ranges.

[0204] Alternatively, according to some embodiments of this application, please continue to refer to... Figure 12 The first winding 311 includes a delta winding, any second winding 312 includes a star winding or a delta winding, and the third winding 313 includes a star winding or a delta winding.

[0205] Specifically, the fractal connector module 30 has a corner winding connected to the three-level NPC inverter 11, meaning the first winding 311 includes a corner winding. This inherently eliminates the third harmonic component. Therefore, the harmonic generation inverter 21 only needs to generate the second harmonic signal in the higher harmonic ranges other than the third harmonic range. In other words, the harmonic generation inverter 21 only needs to compensate for and cancel higher harmonics above the fifth order. Thus, connecting the corner winding in the fractal connector module 30 to the three-level NPC inverter 11 can reduce the capacity of the harmonic generation inverter 21, helping to reduce the cost of the harmonic generation inverter 21 in the three-level NPC fractal converter 100.

[0206] Optionally, according to some embodiments of this application, such as Figure 13 As shown, the fractal connector module 30 includes at least one fourth winding 321 and at least one fifth winding 322;

[0207] The fourth winding 321 is coupled to the corresponding fifth winding 322. The fourth winding 321 is electrically connected to the AC side of the three-level NPC inverter 11. The fifth winding 322 is electrically connected to the AC side of the corresponding harmonic generation inverter 21. The AC side of the three-level NPC inverter 11 is electrically connected to the AC output port.

[0208] For example, the fourth winding 321 can be either a star-connected winding or a delta-connected winding, and the fifth winding 322 can be either a star-connected winding or a delta-connected winding. Figure 13 The indication in the image does not serve a limiting function.

[0209] In practical implementation, after the switching frequency of the switching unit within the three-level NPC inverter 11 decreases, the three-level NPC inverter 11 generates the first harmonic signal within the higher harmonic range. The fundamental signal and the first harmonic signal generated by the three-level NPC inverter 11 are output to the fourth winding 321, and the second harmonic signal generated by the harmonic generating inverter 21 based on the first harmonic signal is output to the fifth winding 322. When there is a voltage level mismatch between the AC side output voltage of the three-level NPC inverter 11 and the AC side output voltage of the harmonic generating inverter 21, the voltage level between the AC side of the three-level NPC inverter 11 and the AC side of the harmonic generating inverter 21 can be matched by a parallel transformer composed of the fourth winding 321 and the fifth winding 322.

[0210] Since the waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal compensates for the first harmonic signal, thereby reducing the harmonic signal at the AC output port and reducing the loss caused by the harmonic signal. This enhances the maximum power output capability of the three-level NPC fractal converter 100 and increases the output capacity of the three-level NPC fractal converter 100. The final generated fundamental signal is then output to the AC output port.

[0211] When the harmonic generation module 20 includes multiple harmonic generation inverters 21, the fractal connector module 30 includes the same number of fourth windings 321 and fifth windings 322. The multiple fourth windings 321 are electrically connected to the AC side of the three-level NPC type inverter 11, and the multiple fifth windings 322 are electrically connected to the corresponding multiple harmonic generation inverters 21. The multiple fourth windings 321 are also coupled to the corresponding fifth windings 322. This allows the second harmonic signals of different higher harmonic ranges generated by different harmonic generation inverters 21 to be introduced into the fractal connector module 30, thereby compensating for the first harmonic signals of different higher harmonic ranges.

[0212] Optionally, according to some embodiments of this application, such as Figure 14As shown, the fractal connector module 30 includes: at least one connecting component;

[0213] The AC side of the three-level NPC inverter 11 is electrically connected to the AC side of the corresponding harmonic generating inverter 21 through a connecting component, so that the AC side of the three-level NPC inverter 11 and the AC side of the corresponding harmonic generating inverter 21 are connected in parallel.

[0214] The AC side of the three-level NPC inverter 11 is electrically connected to the AC output port.

[0215] In this embodiment, the connecting component is, for example, a connecting harness. When the voltage levels between the AC side of the three-level NPC inverter 11 and the AC side of the harmonic generating inverter 21 are matched, the AC side of the three-level NPC inverter 11 is directly connected to the AC side of the harmonic generating inverter 21 within the fractal connector module 30 to form a parallel structure, thereby saving transformer costs.

[0216] Optionally, according to some embodiments of this application, such as Figure 15 As shown, the fractal connector module 30 includes at least one series transformer 330;

[0217] The first input terminal of the series transformer 330 is electrically connected to the AC side of the three-level NPC inverter 11, the second input terminal of the series transformer 330 is electrically connected to the AC side of the corresponding harmonic generation inverter 21, and the output terminal of the series transformer 330 is electrically connected to the AC output port.

[0218] In practice, after the switching frequency of the switching unit in the three-level NPC inverter 11 is reduced, the three-level NPC inverter 11 generates the first harmonic signal in the higher harmonic range. The fundamental signal and the first harmonic signal generated by the three-level NPC inverter 11 are output to the series transformer 330, and the second harmonic signal generated by the harmonic generation inverter 21 based on the first harmonic signal is also output to the series transformer 330.

[0219] The second harmonic signal compensates for the first harmonic signal through the series transformer 330, thereby reducing the harmonic signal at the AC output port and reducing the losses caused by the harmonic signal. This enhances the maximum power output capability of the three-level NPC type fractal converter 100 and increases the output capacity of the three-level NPC type fractal converter 100. Finally, the generated fundamental signal is output to the AC output port through the series transformer 330.

[0220] When the harmonic generation module 20 includes multiple harmonic generation inverters 21, the fractal connector module 30 includes the same number of series transformers 330. The multiple series transformers 330 are connected to the corresponding harmonic generation inverters 21 and connected to the AC side of the three-level NPC type inverter 11 connected in series. This allows the second harmonic signals of different higher harmonic ranges generated by different harmonic generation inverters 21 to be introduced into the fractal connector module 30, thereby enabling the compensation of the first harmonic signals of different higher harmonic ranges.

[0221] Optionally, according to some embodiments of this application, such as Figure 16 As shown, the series transformer 330 includes: a first transformer 331, a second transformer 332, and a third transformer 333;

[0222] The first terminal of the first transformer 331 is electrically connected to the first terminal of the AC side of the three-level NPC inverter 11.

[0223] The second terminal of the first transformer 331 is electrically connected to the first terminal of the AC output port, the third terminal of the first transformer 331 is electrically connected to the neutral point or ground terminal, and the fourth terminal of the first transformer 331 is electrically connected to the first terminal of the AC side of the harmonic generating inverter 21.

[0224] The first terminal of the second transformer 332 is electrically connected to the second terminal of the AC side of the three-level NPC inverter 11.

[0225] The second terminal of the second transformer 332 is electrically connected to the second terminal of the AC output port, the third terminal of the second transformer 332 is electrically connected to the neutral point or ground terminal, and the fourth terminal of the second transformer 332 is electrically connected to the second terminal of the AC side of the harmonic generation inverter 21.

[0226] The first terminal of the third transformer 333 is electrically connected to the third terminal of the AC side of the three-level NPC inverter 11. The second terminal of the third transformer 333 is electrically connected to the third terminal of the AC output port. The third terminal of the third transformer 333 is electrically connected to the neutral point or ground terminal. The fourth terminal of the third transformer 333 is electrically connected to the third terminal of the AC side of the harmonic generation inverter 21.

[0227] like Figure 16As shown, the first transformer 331, the second transformer 332, and the third transformer 333 are single-phase, dual-winding transformers. One winding of the first transformer 331 is connected to the A-phase terminal of the AC output port and the A-phase terminal of the AC side of the three-level NPC inverter 11, respectively. The other winding is connected to the A-phase terminal of the AC side of the harmonic generator inverter 21 and ground, respectively. This connection method realizes the series connection of the A-phase of the AC side of the three-level NPC inverter 11 and the harmonic generator inverter 21, and connects it to the A-phase of the AC output port. The second transformer 332 and the third transformer 333 are used for the series connection of the B-phase and C-phase of the AC side of the three-level NPC inverter 11 and the harmonic generator inverter 21, respectively, and are connected to the B-phase and C-phase of the AC output port.

[0228] In practice, after the switching frequency of the switching unit in the three-level NPC inverter 11 is reduced, the three-level NPC inverter 11 generates the first harmonic signal in the higher harmonic range. The fundamental signal and the first harmonic signal generated by the three-level NPC inverter 11 are output from different output terminals. The second harmonic signal generated by the harmonic generation inverter 21 based on the first harmonic signal is also output through different output terminals. The harmonic signals output from different output terminals of the three-level NPC inverter 11 and the harmonic signals output from different output terminals of the harmonic generation inverter 21 are all output to the first transformer 331, the second transformer 332, and the third transformer 333.

[0229] Since the waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal compensates for the first harmonic signal, thereby reducing the harmonic signal at the AC output port and reducing the losses caused by the harmonic signal. As a result, the maximum power output capability of the three-level NPC type fractal converter 100 is enhanced, and the output capacity of the three-level NPC type fractal converter 100 is improved.

[0230] Optionally, according to some embodiments of this application, such as Figure 17 As shown, the series transformer 330 includes: a first single-phase winding 334, a second single-phase winding 335, a third single-phase winding 336, and a sixth winding 337.

[0231] The first single-phase winding 334, the second single-phase winding 335, and the third single-phase winding 336 are electrically coupled to the sixth winding 337.

[0232] The first end of the first single-phase winding 334 is electrically connected to the first end of the AC side of the three-level NPC inverter 11, and the second end of the first single-phase winding 334 is electrically connected to the first end of the AC output port.

[0233] The first end of the second single-phase winding 335 is electrically connected to the second end of the AC side of the three-level NPC inverter 11, and the second end of the second single-phase winding 335 is electrically connected to the second end of the AC output port.

[0234] The first end of the third single-phase winding 336 is electrically connected to the third end of the AC side of the three-level NPC inverter 11, and the second end of the third single-phase winding 336 is electrically connected to the third end of the AC output port.

[0235] The sixth winding 337 is electrically connected to the first terminal, the second terminal, and the third terminal of the AC side of the corresponding harmonic generating inverter 21.

[0236] like Figure 17 As shown, when the series transformer 330 is a three-phase multi-winding transformer, a single three-phase transformer is used. One side of this three-phase transformer is connected to the harmonic generation inverter 21, and this side has a three-phase star-connected or delta-connected winding. Figure 17 The diagram shows a star connection; on the other side are three independent single-phase windings, which share a single magnetic core.

[0237] In specific implementation, the sixth winding 337 can be either a star-connected winding or a delta-connected winding. After the switching frequency of the switching unit in the three-level NPC inverter 11 decreases, the three-level NPC inverter 11 generates the first harmonic signal in the higher harmonic range. The fundamental signal and the first harmonic signal generated by the three-level NPC inverter 11 are output from different output terminals. The second harmonic signal generated by the harmonic generation inverter 21 based on the first harmonic signal is also output through different output terminals. The harmonic signals output from different output terminals of the three-level NPC inverter 11 are all output to the first single-phase winding 334, the second single-phase winding 335, and the third single-phase winding 336. The harmonic signals output from different output terminals of the harmonic generation inverter 21 are all output to the sixth winding 337.

[0238] Since the waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal compensates for the first harmonic signal. As the harmonic signal is reduced, the loss caused by the harmonic signal is also reduced, thereby enhancing the maximum power output capability of the three-level NPC type fractal converter 100 and increasing the output capacity of the three-level NPC type fractal converter 100.

[0239] It should be added that, Figure 12 The multi-winding electromagnetic coupling of the fractal connector module 30 shown enables the AC output port to exhibit voltage or current source characteristics, making it suitable for various scenarios. Figure 13 or Figure 14 The parallel coupling scheme shown can help the AC output port exhibit current source characteristics. Figures 15-17The series coupling scheme shown can help the AC output port exhibit voltage source characteristics. Therefore, the specific topology selection of the fractal connector module 30 can be flexibly set according to the actual power supply characteristics of the AC output port, and no flexible restrictions are imposed here.

[0240] Accordingly, when the AC output port needs to exhibit voltage source characteristics, the harmonic signal generated by the harmonic generation inverter 21 is a harmonic voltage; when the AC output port needs to exhibit current source characteristics, the harmonic signal generated by the harmonic generation inverter 21 is a harmonic current. In this way, by directly compensating for the harmonics of the voltage or current to be exhibited, the reliability and output performance of the AC output port signal can be fully guaranteed.

[0241] Optionally, according to some embodiments of this application, such as Figure 18 As shown, the three-level NPC type fractal converter 100 also includes:

[0242] The first filter 40 has its first end electrically connected to the AC side of the three-level NPC inverter 11, and its second end electrically connected to the first input end of the fractal connector module 30.

[0243] And / or, the second filter 50, the first end of the second filter 50 is electrically connected to the AC side of the corresponding harmonic generating inverter 21, and the second end of the second filter 50 is electrically connected to the corresponding second input end in the fractal connector module 30.

[0244] For example, the first filter 40 and / or the second filter 50 can be passive filters composed of inductors and capacitors, and can be selected as one of L filter, LC filter, LCL filter and LCLL filter.

[0245] The first filter 40 is used to filter out interference signals in the AC output of the three-level NPC inverter 11, thereby helping to improve the quality of the converter output signal and also helping to reduce the cost of the harmonic generation inverter 21. The first filter 40 can be flexibly configured according to actual needs.

[0246] In the case where the harmonic generating inverter 21 includes a two-level inverter, a three-level inverter, or a five-level inverter, considering that such inverters are affected by pulse width modulation characteristics and generate higher harmonics in their high-frequency switching frequency sidebands, a second filter 50 is set in this case to filter the higher harmonics of the harmonic generating inverter 21 itself, reduce the introduction of new harmonic components, and thus improve the signal performance and quality of the AC output port.

[0247] In some embodiments, the harmonic generating inverter 21 can be a two-level inverter topology, a three-level inverter topology, a five-level inverter topology, a multi-level inverter topology (number of levels > 5, seven levels, nine levels, etc.), a modular multi-level inverter topology, a cascaded H-bridge inverter topology, etc., or it can be a structure of multiple inverters connected in series and parallel or switching devices connected in series and parallel.

[0248] For example, such as Figure 19 As shown, when the harmonic generating inverter 21 uses a two-level inverter topology, the harmonic generating inverter 21 includes a first semiconductor switch 211, a second semiconductor switch 212, a third semiconductor switch 213, a fourth semiconductor switch 214, a fifth semiconductor switch 215, and a sixth semiconductor switch 216.

[0249] The first semiconductor switch 211, the second semiconductor switch 212, the third semiconductor switch 213, the fourth semiconductor switch 214, the fifth semiconductor switch 215, and the sixth semiconductor switch 216 each include at least one semiconductor power switch unit. The specific structure of the semiconductor power switch unit can be found in the preceding text. Figures 7-10 The structure example shown.

[0250] The first end of the first semiconductor switch 211 is connected to the positive terminal of the second DC power supply port, the second end of the first semiconductor switch 211 and the first end of the second semiconductor switch 212 are connected to the midpoint D of the fourth bridge arm, and the second end of the second semiconductor switch 212 is connected to the negative terminal of the second DC power supply port.

[0251] The first end of the third semiconductor switch 213 is connected to the positive terminal of the second DC power supply port, the second end of the third semiconductor switch 213 is connected to the first end of the fourth semiconductor switch 214 at the midpoint E of the fifth bridge arm, and the second end of the fourth semiconductor switch 214 is connected to the negative terminal of the second DC power supply port.

[0252] The first end of the fifth semiconductor switch 215 is connected to the positive terminal of the second DC power supply port, the second end of the fifth semiconductor switch 215 is connected to the first end of the sixth semiconductor switch 216 at the midpoint F of the sixth bridge arm, and the second end of the sixth semiconductor switch 216 is connected to the negative terminal of the second DC power supply port.

[0253] The midpoints D of the fourth bridge arm, E of the fifth bridge arm, and F of the sixth bridge arm are all connected to the fractal connector module 30.

[0254] In specific implementation, the first harmonic signal generated by the three-level NPC type fractal converter 100 is detected, and the first semiconductor switch 211, the second semiconductor switch 212, the third semiconductor switch 213, the fourth semiconductor switch 214, the fifth semiconductor switch 215, and the sixth semiconductor switch 216 are controlled to turn on and off according to the first harmonic signal, so that the second harmonic signal with the opposite waveform to the first harmonic signal is output and output to the fractal connector module 30.

[0255] Since the waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal in the fractal connector module 30 can cancel out the part of the first harmonic signal that has the same value as the second harmonic signal. This achieves compensation of the first harmonic signal by the second harmonic signal. As the harmonic signal is reduced, the loss caused by the harmonic signal is also reduced, thereby enhancing the maximum output power capability of the three-level NPC type fractal converter 100. While reducing the switching frequency of the three-level NPC type inverter 11, the output capacity of the converter can also be increased.

[0256] It is understood that the above are all examples and do not serve as a substantial limitation on the three-level NPC type fractal converter 100 protected in this application.

[0257] It should be added that the three-level NPC type fractal converter 100 provided in this application can realize decoupled control of AC and DC voltage and bidirectional power transmission, and can be used as an inverter or a rectifier.

[0258] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0259] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0260] It should be clarified that the various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. According to the embodiments described above, these embodiments do not exhaustively describe all details, nor do they limit this application to only the specific embodiments described. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to make good use of this application and modifications based on it. This application is limited only by the claims and their full scope and equivalents.

[0261] Those skilled in the art will understand that the above embodiments are exemplary and not restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on a study of the drawings, specification, and claims, those skilled in the art should be able to understand and implement other variations of the disclosed embodiments. In the claims, the term "comprising" does not exclude other structures; the quantity refers to "one" but does not exclude multiple; the terms "first" and "second" are used to identify names and not to indicate any particular order. Any reference numerals in the claims should not be construed as limiting the scope of protection. The appearance of certain technical features in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.

[0262] This document uses specific examples to illustrate the principles and implementation methods of this application. The examples are merely for the purpose of helping to understand the method and core ideas of this application. The above are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, and the existence of an infinite number of specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the concept and technical solution of this application to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A three-level NPC-type fractal converter, characterized in that, The three-level NPC type fractal converter includes: An inverter module includes a three-level NPC inverter, wherein the DC side of the three-level NPC inverter is electrically connected to a first DC power supply port, and the three-level NPC inverter is used to output an AC signal, wherein the AC signal includes a first harmonic signal in the higher harmonic range. The harmonic generation module includes at least one harmonic generation inverter, wherein the DC side of any of the harmonic generation inverters is electrically connected to a corresponding second DC power supply port, and the corresponding harmonic generation inverter is used to output a corresponding second harmonic signal according to the first harmonic signal. The fractal connector module has a first input terminal electrically connected to the AC side of the three-level NPC inverter, at least one second input terminal of the fractal connector module electrically connected to the corresponding AC side of at least one harmonic generating inverter, and an output terminal of the fractal connector module electrically connected to the AC output port. The second harmonic signal is used to compensate for the first harmonic signal within the fractal connector module.

2. The three-level NPC-type fractal converter according to claim 1, characterized in that, The number of harmonic generation inverters in the harmonic generation module is 1; The alternating current signal includes n first harmonic signals corresponding to n higher harmonic intervals, where n is greater than or equal to 1 and n is a positive integer. The harmonic generation inverter is used to output n second harmonic signals, and the n second harmonic signals correspond one-to-one with the n first harmonic signals.

3. The three-level NPC-type fractal converter according to claim 1, characterized in that, The number of harmonic generation inverters in the harmonic generation module is n, where n is greater than 1 and n is a positive integer. The AC sides of the n harmonic generation inverters are electrically connected to the n second input terminals of the fractal connector module, respectively. The switching frequency of the switching device of the i-th harmonic generating inverter is greater than the switching frequency of the switching device of the (i-1)-th harmonic generating inverter, 1 < i ≤ n, where i is a positive integer; The alternating current signal includes n first harmonic signals corresponding to n higher harmonic intervals. The n harmonic generation inverter is used to output n second harmonic signals, and the n second harmonic signals correspond one-to-one with the n first harmonic signals.

4. The three-level NPC-type fractal converter according to claim 1, characterized in that, The switching frequency of any of the harmonic generating inverters is greater than the switching frequency of the three-level NPC inverter.

5. The three-level NPC-type fractal converter according to claim 1, characterized in that, The three-level NPC inverter includes at least one supporting capacitor and a three-phase inverter bridge. The AC side of the three-level NPC inverter includes three single-phase AC output terminals. The three-phase inverter bridge includes a first bridge arm branch, a second bridge arm branch, and a third bridge arm branch disposed between the first DC power supply ports; The first bridge arm branch includes the midpoint of the first bridge arm, the second bridge arm branch includes the midpoint of the second bridge arm, and the third bridge arm branch includes the midpoint of the third bridge arm. The midpoints of the first, second, and third bridge arms are electrically connected to the three single-phase AC output terminals respectively. The at least one supporting capacitor is connected in series between the first DC power supply ports.

6. The three-level NPC-type fractal converter according to claim 5, characterized in that, The three-level NPC inverter is a three-level I-type NPC structure; The first bridge arm branch includes a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit connected in series between the first DC power supply ports. The second switch unit and the third switch unit are electrically connected to the midpoint of the first bridge arm. The second bridge arm branch includes a fifth switch unit, a sixth switch unit, a seventh switch unit, and an eighth switch unit connected in series between the first DC power supply ports. The sixth switch unit and the seventh switch unit are electrically connected to the midpoint of the second bridge arm. The third bridge arm branch includes a ninth switch unit, a tenth switch unit, an eleventh switch unit, and a twelfth switch unit connected in series between the first DC power supply ports. The tenth switch unit and the eleventh switch unit are electrically connected to the midpoint of the third bridge arm. The three-phase inverter bridge also includes: a first diode, a second diode, a third diode, a fourth diode, a fifth diode, and a sixth diode; The cathode of the first diode is electrically connected to the first node, and the anode of the first diode is electrically connected to the neutral point. The cathode of the second diode is electrically connected to the neutral point, and the anode of the second diode is electrically connected to the second node. The cathode of the third diode is electrically connected to the third node, and the anode of the third diode is electrically connected to the neutral point. The cathode of the fourth diode is electrically connected to the neutral point, and the anode of the fourth diode is electrically connected to the fourth node. The cathode of the fifth diode is electrically connected to the fifth node, and the anode of the fifth diode is electrically connected to the neutral point. The cathode of the sixth diode is electrically connected to the neutral point, and the anode of the sixth diode is electrically connected to the sixth node. The first node is the common point of the first switch unit and the second switch unit; the second node is the common point of the third switch unit and the fourth switch unit; the third node is the common point of the fifth switch unit and the sixth switch unit; the fourth node is the common point of the seventh switch unit and the eighth switch unit; the fifth node is the common point of the ninth switch unit and the tenth switch unit; and the sixth node is the common point of the eleventh switch unit and the twelfth switch unit.

7. The three-level NPC-type fractal converter according to claim 5, characterized in that, The three-level NPC inverter is a three-level T-type NPC structure; The first bridge arm branch includes a thirteenth switch unit and a fourteenth switch unit connected in series between the first DC power supply ports, and the thirteenth switch unit and the fourteenth switch unit are electrically connected to the midpoint of the first bridge arm. The second bridge arm branch includes a fifteenth switch unit and a sixteenth switch unit connected in series between the first DC power supply ports, and the fifteenth switch unit and the sixteenth switch unit are electrically connected to the midpoint of the second bridge arm. The third bridge arm branch includes a seventeenth switch unit and an eighteenth switch unit connected in series between the first DC power supply ports, and the seventeenth switch unit and the eighteenth switch unit are electrically connected to the midpoint of the third bridge arm. The three-phase inverter bridge also includes: the nineteenth switching unit, the twentieth switching unit, the twenty-first switching unit, the twenty-second switching unit, the twenty-third switching unit, and the twenty-fourth switching unit; The first end of the nineteenth switch unit is electrically connected to the midpoint of the first bridge arm, the second end of the nineteenth switch unit is electrically connected to the second end of the twentieth switch unit, and the first end of the twentieth switch unit is electrically connected to the neutral point. The first end of the 21st switch unit is electrically connected to the midpoint of the second bridge arm, the second end of the 21st switch unit is electrically connected to the second end of the 22nd switch unit, and the first end of the 22nd switch unit is electrically connected to the neutral point. The first end of the 23rd switch unit is electrically connected to the midpoint of the third bridge arm, the second end of the 23rd switch unit is electrically connected to the second end of the 24th switch unit, and the first end of the 24th switch unit is electrically connected to the neutral point.

8. The three-level NPC-type fractal converter according to claim 5, characterized in that, The three-phase inverter bridge includes multiple switching units, and each of the multiple switching units includes multiple semiconductor power switching units; the semiconductor power switching units include at least one of IGCT, IGBT, IEGT and MOSFET. In any one of the semiconductor power switch units, the plurality of semiconductor power switch units are connected in series. And / or, the plurality of semiconductor power switching units in any of the said switching units are connected in parallel with each other.

9. The three-level NPC-type fractal converter according to claim 8, characterized in that, The semiconductor power switch unit in any of the aforementioned switching units includes an IGCT; The three-level NPC inverter also includes a clamping circuit disposed between the first DC power supply ports.

10. The three-level NPC-type fractal converter according to claim 5, characterized in that, The at least one supporting capacitor includes a first supporting capacitor and a second supporting capacitor; The first terminal of the first supporting capacitor is electrically connected to the positive terminal of the first DC power supply port, the second terminal of the first supporting capacitor and the first terminal of the second supporting capacitor are respectively electrically connected to the neutral point, and the second terminal of the second supporting capacitor is electrically connected to the negative terminal of the first DC power supply port.

11. The three-level NPC-type fractal converter according to any one of claims 1-10, characterized in that, The fractal connector module includes: a first winding, at least one second winding, and a third winding; The first winding, the at least one second winding, and the third winding are coupled together; The first winding is electrically connected to the AC side of the three-level NPC inverter, the at least one second winding is electrically connected to the AC side of at least one harmonic generating inverter, and the third winding is electrically connected to the AC output port.

12. The three-level NPC-type fractal converter according to claim 11, characterized in that, The first winding includes a delta winding, any second winding includes a star winding or a delta winding, and the third winding includes a star winding or a delta winding.

13. The three-level NPC-type fractal converter according to any one of claims 1-10, characterized in that, The fractal connector module includes: at least one fourth winding and at least one fifth winding; The fourth winding is coupled to the corresponding fifth winding, the fourth winding is electrically connected to the AC side of the three-level NPC inverter, the fifth winding is electrically connected to the AC side of the corresponding harmonic generating inverter, and the AC side of the three-level NPC inverter is electrically connected to the AC output port.

14. The three-level NPC-type fractal converter according to any one of claims 1-10, characterized in that, The fractal connector module includes: at least one connecting component; The AC side of the three-level NPC inverter is electrically connected to the AC side of the corresponding harmonic generating inverter through the connecting component, so that the AC side of the three-level NPC inverter and the AC side of the corresponding harmonic generating inverter are connected in parallel. The AC side of the three-level NPC inverter is electrically connected to the AC output port.

15. The three-level NPC-type fractal converter according to any one of claims 1-10, characterized in that, The fractal connector module includes at least one series transformer; The first input terminal of the series transformer is electrically connected to the AC side of the three-level NPC inverter, the second input terminal of the series transformer is electrically connected to the AC side of the corresponding harmonic generation inverter, and the output terminal of the series transformer is electrically connected to the AC output port.

16. The three-level NPC-type fractal converter according to claim 15, characterized in that, The series transformer includes: a first transformer, a second transformer, and a third transformer; The first terminal of the first transformer is electrically connected to the first terminal of the AC side of the three-level NPC inverter, the second terminal of the first transformer is electrically connected to the first terminal of the AC output port, the third terminal of the first transformer is electrically connected to the neutral point or ground terminal, and the fourth terminal of the first transformer is electrically connected to the first terminal of the AC side of the harmonic generation inverter. The first terminal of the second transformer is electrically connected to the second terminal of the AC side of the three-level NPC inverter, the second terminal of the second transformer is electrically connected to the second terminal of the AC output port, the third terminal of the second transformer is electrically connected to the neutral point or ground terminal, and the fourth terminal of the second transformer is electrically connected to the second terminal of the AC side of the harmonic generation inverter. The first terminal of the third transformer is electrically connected to the third terminal of the AC side of the three-level NPC inverter, the second terminal of the third transformer is electrically connected to the third terminal of the AC output port, the third terminal of the third transformer is electrically connected to the neutral point or ground terminal, and the fourth terminal of the third transformer is electrically connected to the third terminal of the AC side of the harmonic generation inverter.

17. The three-level NPC-type fractal converter according to claim 15, characterized in that, The series transformer includes: a first single-phase winding, a second single-phase winding, a third single-phase winding, and a sixth winding; The first single-phase winding, the second single-phase winding, and the third single-phase winding are electrically coupled to the sixth winding; The first end of the first single-phase winding is electrically connected to the first end of the AC side of the three-level NPC inverter, and the second end of the first single-phase winding is electrically connected to the first end of the AC output port. The first end of the second single-phase winding is electrically connected to the second end of the AC side of the three-level NPC inverter, and the second end of the second single-phase winding is electrically connected to the second end of the AC output port. The first end of the third single-phase winding is electrically connected to the third end of the AC side of the three-level NPC inverter, and the second end of the third single-phase winding is electrically connected to the third end of the AC output port. The sixth winding is electrically connected to the first terminal, the second terminal, and the third terminal of the AC side of the corresponding harmonic generating inverter.

18. The three-level NPC-type fractal converter according to any one of claims 1-10, characterized in that, The three-level NPC type fractal converter also includes: A first filter, the first end of which is electrically connected to the AC side of the three-level NPC inverter, and the second end of which is electrically connected to the first input end of the fractal connector module; And / or, a second filter, the first end of which is electrically connected to the AC side of the corresponding harmonic generating inverter, and the second end of which is electrically connected to the corresponding second input end in the fractal connector module.

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