Three-level flying capacitor type fractal converter

Abstract

The invention relates to a three-level flying capacitive type fractal converter. The three-level flying capacitive type fractal converter comprises an inversion module, a harmonic generation module and a fractal connector module. The inversion module comprises a three-level flying capacitance type inverter, the three-level flying capacitance type inverter is used for outputting an alternating current signal, and the alternating current signal comprises a first harmonic signal in a higher harmonic interval; the harmonic generation module comprises at least one harmonic generation inverter; the harmonic generation inverter is used for generating a second harmonic signal according to the first harmonic signal; the fractal connector module is connected with the alternating current side of the three-level flying capacitor type inverter and the alternating current side of the harmonic generation inverter, and the output end of the fractal connector module is 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 invention, the switching frequency of the three-level flying capacitor type fractal converter can be reduced, and the overall output capacity of the converter can be improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of converter technology, and in particular to a three-level flying capacitor fractal converter. BACKGROUND

[0002] With the vigorous development of new energy power generation, new power systems have higher demands for high-power power electronic converters. In the existing AC / DC converter technical solutions, the switching frequency of the three-level flying capacitor fractal converter is relatively high, usually greater than 1 kHz, which results in high switching device loss and large heat generation, thereby leading to low overall output capacity of the converter and high cost per unit capacity of the converter. Therefore, how to reduce the switching frequency of the three-level flying capacitor fractal converter at a low cost and improve the overall output capacity of the converter has become a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0003] In order to solve the above technical problems or at least partially solve the above technical problems, the present disclosure provides a three-level flying capacitor fractal converter, which can reduce the switching frequency of the three-level flying capacitor fractal converter while improving the overall output capacity of the converter.

[0004] The present disclosure provides a three-level flying capacitor fractal converter, comprising an inverter module, a harmonic generation module, and a fractal connector module.

[0005] The inverter module comprises a three-level flying capacitor inverter, and the DC side of the three-level flying capacitor inverter is connected to a first DC power supply port; wherein the three-level flying capacitor inverter is configured to output an alternating current signal; the alternating current signal comprises a first harmonic signal in a high-order harmonic interval;

[0006] The harmonic generation module comprises at least one harmonic generation inverter, and the DC side of the harmonic generation inverter is connected to a second DC power supply port; the harmonic generation inverter is configured to generate a second harmonic signal according to the first harmonic signal;

[0007] The first input end of the fractal connector module is connected to the AC side of the three-level flying capacitor inverter, the second input end of the fractal connector module is connected to the AC side of the harmonic generation inverter, and the output end of the fractal connector module is connected to an AC output port; the second harmonic signal is configured to compensate for the first harmonic signal in the fractal connector module.

[0008] Optionally, the harmonic generation module comprises n harmonic generation inverters; wherein n is a positive integer greater than 1;

[0009] The n harmonic generation inverters are respectively connected to a plurality of input ends of the fractal connector module;

[0010] 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; wherein i is a positive integer less than or equal to n;

[0011] The harmonic generating inverter is configured to generate a second harmonic signal according to a first harmonic signal in a high harmonic interval corresponding to the three-level flying capacitor type inverter.

[0012] Optionally, the three-level flying capacitor type inverter comprises three bridge arms;

[0013] Any bridge arm comprises a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, and a flying capacitor;

[0014] The first switching unit, the second switching unit, the third switching unit, and the fourth switching unit each comprise at least one semiconductor power switching unit;

[0015] The first end of the first switching unit is connected to the positive terminal of the first DC power supply port, the second end of the first switching unit and the first end of the second switching unit are connected to a first connection point, the second end of the second switching unit and the first end of the third switching unit are connected to a bridge arm midpoint, the second end of the third switching unit and the first end of the fourth switching unit are connected to a second connection point, the second end of the fourth switching unit is connected to the negative terminal of the first DC power supply port, the first end of the flying capacitor is connected to the first connection point, and the second end of the flying capacitor is connected to the second connection point;

[0016] The bridge arm midpoints of the three bridge arms are each connected to a fractal connector module.

[0017] Optionally, the first switching unit, the second switching unit, the third switching unit, and the fourth switching unit each comprise a plurality of semiconductor power switching units.

[0018] The semiconductor power switching unit comprises at least one of an IGCT, an IGBT, an IEGT, and a MOSFET.

[0019] Optionally, the plurality of semiconductor power switching units are connected in series, or the plurality of semiconductor power switching units are connected in parallel with each other.

[0020] Optionally, the semiconductor power switching unit comprises an IGCT; and the three-level flying capacitor type inverter further comprises a clamping unit.

[0021] The clamping unit is configured to limit the current change rate of the semiconductor power switching unit and limit the oscillation amplitude of the AC side output voltage of the three-level flying capacitor type inverter when the semiconductor power switching unit is turned on.

[0022] Optionally, the clamping unit comprises: a first clamping reactor, a second clamping reactor, a first clamping capacitor, a second clamping capacitor, a first clamping diode, a second clamping diode, a first clamping resistor, and a second clamping resistor.

[0023] The first end of the first clamping reactor is connected with the positive terminal of the first DC power supply port, the second end of the first clamping reactor is connected with the positive terminal of the first clamping diode, the negative terminal of the first clamping diode is connected with the first end of the first clamping capacitor, the second end of the first clamping capacitor is connected with the first end of the second clamping capacitor, the second end of the second clamping capacitor is connected with the positive terminal of the second clamping diode, the negative terminal of the second clamping diode is connected with the second end of the second clamping reactor, the first end of the second clamping reactor is connected with the negative terminal of the first DC power supply port, the first end of the first clamping resistor is connected with the first end of the first clamping reactor, the second end of the first clamping resistor is connected with the negative terminal of the first clamping diode, the first end of the second clamping resistor is connected with the first end of the second clamping reactor, and the second end of the second clamping resistor is connected with the positive terminal of the second clamping diode.

[0024] Optionally, the fractal connector module comprises: a first winding, a second winding, and at least one third winding.

[0025] The first winding, the second winding, and the at least one third winding are coupled, the first winding is connected with the AC side of the three-level flying capacitor type inverter, the second winding is connected with the AC output port, and the third winding is connected with the corresponding harmonic generating inverter.

[0026] Optionally, the first winding comprises an angle connection winding.

[0027] Optionally, the fractal connector module comprises: at least one fourth winding and at least one fifth winding.

[0028] The fourth winding is coupled with the corresponding fifth winding, the fourth winding is connected with the AC side of the three-level flying capacitor type inverter, the fifth winding is connected with the corresponding harmonic generating inverter, and the AC side of the three-level flying capacitor type inverter is connected with the AC output port.

[0029] Optionally, the fractal connector module comprises at least one connecting component.

[0030] The AC side of the three-level flying capacitor type inverter is connected with the AC side of the corresponding harmonic generating inverter in parallel through the connecting component, and the AC side of the three-level flying capacitor type inverter is connected with the AC output port.

[0031] Optionally, the fractal connector module comprises at least one series transformer.

[0032] The first input end of the series transformer is connected with the AC side of the three-level flying capacitor type inverter, the second input end of the series transformer is connected with the AC side of the corresponding harmonic generating inverter, and the output end of the series transformer is connected with the AC output port.

[0033] Optionally, the series transformer comprises a first transformer, a second transformer and a third transformer.

[0034] The first end of the first transformer is connected with the first output end of the three-level flying capacitor type inverter, the second end of the first transformer is connected with the first end of the AC output port, the third end of the first transformer is connected with the neutral point or the grounding end, and the fourth end of the first transformer is connected with the first output end of the harmonic generating inverter.

[0035] The first end of the second transformer is connected with the second output end of the three-level flying capacitor type inverter, the second end of the second transformer is connected with the second end of the AC output port, the third end of the second transformer is connected with the neutral point or the grounding end, and the fourth end of the second transformer is connected with the second output end of the harmonic generating inverter.

[0036] The first end of the third transformer is connected with the third output end of the three-level flying capacitor type inverter, the second end of the third transformer is connected with the third end of the AC output port, the third end of the third transformer is connected with the neutral point or the grounding end, and the fourth end of the third transformer is connected with the third output end of the harmonic generating inverter.

[0037] Optionally, the series transformer comprises a first single-phase winding, a second single-phase winding, a third single-phase winding and a sixth winding.

[0038] The first single-phase winding, the second single-phase winding and the third single-phase winding are coupled to the sixth winding; the first end of the first single-phase winding is connected with the first output end of the three-level flying capacitor type inverter, and the second end of the first single-phase winding is connected with the first end of the AC output port; the first end of the second single-phase winding is connected with the second output end of the three-level flying capacitor type inverter, and the second end of the second single-phase winding is connected with the second end of the AC output port; the first end of the third single-phase winding is connected with the third output end of the three-level flying capacitor type inverter, and the second end of the third single-phase winding is connected with the third end of the AC output port; and the sixth winding is connected with the first output end of the harmonic generating inverter, the second output end of the harmonic generating inverter and the third output end of the harmonic generating inverter.

[0039] Optionally, the three-level flying capacitor type fractal converter further comprises a first filter and / or a second filter.

[0040] The plurality of input ends of the first filter are electrically connected with the AC side of the three-level flying capacitor type inverter, and the output end of the first filter is electrically connected with the first input end of the fractal connector module.

[0041] The plurality of input ends of the second filter are electrically connected with the alternating current side of the corresponding harmonic generation inverter, and the output end of the second filter is electrically connected with the corresponding second input end in the fractal connector module.

[0042] The present disclosure provides a three-level flying capacitor type fractal converter, which comprises an inverter module, a harmonic generation module and a fractal connector module. The inverter module comprises a three-level flying capacitor type inverter, and the direct current side of the three-level flying capacitor type inverter is connected with a first direct current power supply port; wherein the three-level flying capacitor type inverter is used to output an alternating current signal; the alternating current signal comprises a first harmonic signal in a high-order harmonic interval; the harmonic generation module comprises at least one harmonic generation inverter, and the direct current side of the harmonic generation inverter is connected with a second direct current power supply port; the harmonic generation inverter is used to generate a second harmonic signal according to the first harmonic signal; the first input end of the fractal connector module is connected with the alternating current side of the three-level flying capacitor type inverter, the second input end of the fractal connector module is connected with the alternating current side of the harmonic generation inverter, and the output end of the fractal connector module is connected with an alternating current output port; the second harmonic signal is used to compensate the first harmonic signal in the fractal connector module. When the three-level flying capacitor type inverter module adopts a lower switching frequency switching device, the three-level flying capacitor type inverter will generate the first harmonic signal. The present disclosure additionally provides the harmonic generation inverter, which generates the second harmonic signal according to the first harmonic signal generated by the three-level flying capacitor type inverter and outputs the second harmonic signal to the fractal connector module. Since the waveforms of the second harmonic signal and the first harmonic signal are opposite, the second harmonic signal can offset the same part in the first harmonic signal as the second harmonic signal, so as to compensate the first harmonic signal in the fractal connector module by the second harmonic signal, so that the maximum power output by the converter is improved, that is, the output capacity of the converter is improved. Therefore, the present disclosure can reduce the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0044] Figure 1 A structure schematic diagram of a three-level flying capacitor type fractal converter provided by the embodiments of the present disclosure.

[0045] Figure 2 A structure diagram of still another three-level flying-capacitor type fractal converter is provided for an embodiment of the present disclosure.

[0046] Figure 3 A structure diagram of a three-level flying-capacitor type inverter is provided for an embodiment of the present disclosure.

[0047] Figure 4 A structure diagram of a first switch unit is provided for an embodiment of the present disclosure.

[0048] Figure 5 A structure diagram of still another first switch unit is provided for an embodiment of the present disclosure.

[0049] Figure 6 A structure diagram of a semiconductor power switch unit is provided for an embodiment of the present disclosure.

[0050] Figure 7 A structure diagram of still another semiconductor power switch unit is provided for an embodiment of the present disclosure.

[0051] Figure 8 A structure diagram of still another semiconductor power switch unit is provided for an embodiment of the present disclosure.

[0052] Figure 9 A structure diagram of still another semiconductor power switch unit is provided for an embodiment of the present disclosure.

[0053] Figure 10 A structure diagram of still another three-level flying-capacitor type fractal converter is provided for an embodiment of the present disclosure.

[0054] Figure 11 A structure diagram of still another three-level flying-capacitor type fractal converter is provided for an embodiment of the present disclosure.

[0055] Figure 12 A structure diagram of still another three-level flying-capacitor type fractal converter is provided for an embodiment of the present disclosure.

[0056] Figure 13 A structure diagram of still another three-level flying-capacitor type fractal converter is provided for an embodiment of the present disclosure.

[0057] Figure 14 A structure diagram of a series transformer is provided for an embodiment of the present disclosure.

[0058] Figure 15 A structure diagram of still another series transformer is provided for an embodiment of the present disclosure.

[0059] Figure 16 A structure diagram of a harmonic generation inverter is provided for an embodiment of the present disclosure. DETAILED DESCRIPTION

[0060] Features and exemplary embodiments of various aspects of the present application will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without some or all of these specific details. The description of the embodiments is merely illustrative of the present application.

[0061] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The embodiments will be described in detail below with reference to the accompanying drawings.

[0062] It should be noted that, in this document, the terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Also, the terms "comprises", "comprising", or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but also includes other elements not explicitly listed, or further includes elements inherent in such a process, method, article, or apparatus. Without more limitations, the element defined by the statement "comprises" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0063] It should be understood that, when describing the structure of a component, when one layer, one region is referred to as being "on" or "above" another layer, another region, it can mean being directly on or above the other layer, another region, or containing other layers or regions therebetween. And if the component is turned over, the one layer, one region will be "under" or "below" the other layer, another region.

[0064] It should be understood that the term "and / or" used herein is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing together, and B existing alone. In addition, the character " / " in this document generally represents an "or" relationship between the front and rear associated objects.

[0065] In the embodiments of the present application, the term "electrically connected" can mean that two components are directly electrically connected, or can mean that two components are electrically connected via one or more other components.

[0066] In the embodiments of the present application, the first node, the second node and the third node are only defined for the convenience of describing the circuit structure, and the first node, the second node and the third node are not an actual circuit unit.

[0067] Various modifications and changes can be made to the present application in matters of form and details without departing from the spirit and scope of the application, which will be apparent to one skilled in the art. Therefore, the present application is intended to cover all modifications and changes as falling within the scope of the corresponding claims (claimed technical solutions) and their equivalents. It should be noted that the embodiments provided in the present application can be combined with each other without contradiction.

[0068] With the vigorous development of new energy power generation, the demand for high-power power electronic converters is increasing in new power systems. In the existing AC-DC converter technical solutions, the switching frequency of the three-level flying capacitor fractal converter is usually higher than 1 kHz, which results in high switching device loss and large heat generation, thereby leading to low overall output capacity of the converter and high cost of the converter per unit capacity.

[0069] In conventional technology, if the output capacity of the three-level flying capacitor fractal converter is to be expanded, a plurality of three-level flying capacitor fractal converters are usually connected in parallel, and the increase in the number of three-level flying capacitor fractal converters leads to an increase in the cost of the converter. If the switching frequency of the three-level flying capacitor fractal converter is to be reduced, a larger inductor-capacitor filter is usually required to filter out the high-order harmonic signals generated due to the reduction in the switching frequency. Since the converter with low switching frequency generates larger harmonic signals, a larger passive filter needs to be provided, which also leads to a substantial increase in the cost of the converter.

[0070] Therefore, the present disclosure provides a three-level flying capacitor fractal converter. After reducing the switching frequency of the three-level flying capacitor fractal converter, a harmonic generation inverter generates a second harmonic signal according to a first harmonic signal generated by the three-level flying capacitor fractal inverter, and a fractal connector module compensates the first harmonic signal with the second harmonic signal, so that the ability of the converter to output maximum power is improved, that is, the output capacity of the converter is improved. Therefore, the present disclosure does not need to additionally provide a plurality of three-level flying capacitor fractal converters and passive filters, so as to reduce the switching frequency of the three-level flying capacitor fractal converter and improve the output capacity of the converter at a low cost.

[0071] The embodiments will be described in detail below with reference to the accompanying drawings.

[0072] Figure 1 A structure diagram of a three-level flying capacitor fractal converter provided in the embodiments of the present disclosure is shown in Figure 1As shown, the three-level flying-capacitor type fractal converter comprises an inverter module 10, a harmonic generation module 20 and a fractal connector module 30.

[0073] The inverter module 10 comprises a three-level flying-capacitor type inverter 100, the DC side of the three-level flying-capacitor type inverter 100 being connected with the first DC power supply port 41; wherein the three-level flying-capacitor type inverter 100 is used to output an alternating current signal; the alternating current signal comprises a first harmonic signal in a high-order harmonic interval.

[0074] Specifically, each phase bridge arm of the three-level flying-capacitor type inverter 100 is provided with a flying capacitor, and by controlling the on-off of a plurality of switching devices in each phase bridge arm, a first level, a second level and a third level with different voltage sizes are generated in each phase bridge arm, that is, a three-level voltage signal is generated in each phase bridge arm, and finally the line voltage output by the three-level flying-capacitor type inverter 100 is an alternating current signal, and the voltage signal output by the three-level flying-capacitor type inverter 100 is closer to a sine wave than the two-level inverter used in the conventional technology. The alternating current signal comprises a first harmonic signal in a high-order harmonic interval, which can be, for example, a third harmonic interval, a fifth harmonic interval, etc. The three-level flying-capacitor type inverter 100 can be used to realize decoupling control of DC voltage and bidirectional transmission of power, and therefore can be used as an inverter or a rectifier.

[0075] For example, the switching frequency of the switching unit in the three-level flying-capacitor type inverter 100 is less than 500Hz, and the switching unit can adopt any one of, for example, 50Hz, 150Hz, 250Hz, 350Hz and 450Hz, thereby generating a fundamental signal of 50Hz or other frequencies. Since the switching frequency of the switching unit is low, the device loss in the three-level flying-capacitor type inverter 100 can be reduced, thereby being able to output greater power, and further improving the unit capacity and reducing the cost of the three-level flying-capacitor type inverter 100.

[0076] The harmonic generation module 20 comprises at least one harmonic generation inverter 200, the DC side of the harmonic generation inverter 200 being connected with the second DC power supply port 42; the harmonic generation inverter 200 is used to generate a second harmonic signal according to the first harmonic signal; wherein the second harmonic signal is used to compensate for the first harmonic signal in the fractal connector module 30.

[0077] For example, the harmonic generation inverter 200 can be, for example, any one of a two-level inverter, a three-level inverter, a five-level inverter, a multi-level inverter, a modular multi-level inverter, a cascaded H-bridge inverter, or a plurality of inverters in series or parallel connection or a plurality of switching devices in series or parallel connection.

[0078] Since the harmonic generating inverter 200 is only used to generate the second harmonic signal and is not used to generate the fundamental signal, the capacity of the harmonic generating inverter 200 is small, so that the manufacturing cost of the harmonic generating inverter 200 is low. Compared with the way of using multiple groups of three-level flying capacitor type fractal converters in parallel and setting passive filters for harmonic filtering in the conventional technology, the way of using the harmonic generating inverter 200 to generate the second harmonic signal to compensate for the first harmonic signal in the present disclosure is lower in cost.

[0079] The first input end of the fractal connector module 30 is connected with the alternating current side of the three-level flying capacitor type inverter 100, the second input end of the fractal connector module 30 is connected with the alternating current side of the harmonic generating inverter 200, and the output end of the fractal connector module 30 is connected with the alternating current output port 43.

[0080] For example, the three-level flying capacitor type inverter 100 includes multiple switching units, by reducing the switching frequency of each switching unit, the device loss of the switching unit of the three-level flying capacitor type inverter 100 can be reduced, so that the three-level flying capacitor type inverter 100 can output more power. And after reducing the switching frequency of the switching unit, the three-level flying capacitor type inverter 100 will output the first harmonic signal in the high-order harmonic interval.

[0081] The three-level flying capacitor type inverter 100 is used to generate the first harmonic signal and the fundamental signal at the alternating current side, and adjust the amplitude and phase angle of the fundamental wave to realize power conversion between alternating current and direct current. The harmonic generating inverter 200 is used to generate the second harmonic signal at the alternating current side, and the second harmonic signal is a high-frequency harmonic signal. The alternating current side of the three-level flying capacitor type inverter 100 and the alternating current side of the harmonic generating inverter 200 are connected through the fractal connector module 30, so that the first harmonic signal and the second harmonic signal are coupled with each other in the fractal connector module 30 to realize harmonic cancellation, thereby realizing the compensation of the second harmonic signal to the first harmonic signal, and finally generating a standard sine waveform.

[0082] As an example, continue to refer to Figure 1The harmonic generation module 20 includes a harmonic generation inverter 200, which is configured to generate a second harmonic signal according to a first harmonic signal generated by the three-level flying capacitor type inverter 100. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor type inverter 100 are output to the fractal connector module 30, and the second harmonic signal generated by the harmonic generation module 20 is also output to the fractal connector module 30. Since the signal waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal with the same value as the second harmonic signal, thereby realizing the compensation of the second harmonic signal to the first harmonic signal in the fractal connector module 30. Since the harmonic signal is compensated, the loss caused by the harmonic signal is also reduced, thereby enhancing the ability of the three-level flying capacitor type fractal converter to output the maximum power and improving the output capacity of the three-level flying capacitor type fractal converter. Therefore, the disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter.

[0083] As another example, Figure 2 Another structure schematic diagram of a three-level flying capacitor type fractal converter provided by the embodiment of the disclosure is shown in FIG. 6. Figure 2As shown, the harmonic generation module 20 includes three harmonic generation inverters 200, the three harmonic generation inverters 200 are connected with the fractal connector module 30, and the switching frequencies of the three harmonic generation inverters 200 are different, so that different second harmonic signals can be generated according to the different first harmonic signals generated by the three-level flying capacitor type inverter 100 in different high-order harmonic intervals. For example, in the case that the three-level flying capacitor type inverter 100 can generate the first harmonic signal in the third harmonic interval, the first harmonic signal in the fifth harmonic interval, and the first harmonic signal in the seventh harmonic interval, the three harmonic generation inverters 200 can respectively generate the corresponding second harmonic signal in the third harmonic interval, the second harmonic signal in the fifth harmonic interval, and the second harmonic signal in the seventh harmonic interval. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor type inverter 100 are output to the fractal connector module 30, and the second harmonic signal generated by the harmonic generation module 20 is also output to the fractal connector module 30. Since the signal waveform of the second harmonic signal is opposite to the signal waveform of the corresponding first harmonic signal, the second harmonic signal can offset the part in the corresponding first harmonic signal that has the same value as the second harmonic signal, that is, the compensation of the second harmonic signal to the first harmonic signal is realized in the fractal connector module 30. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, so that the ability of the three-level flying capacitor type fractal converter to output the maximum power is enhanced, and the output capacity of the three-level flying capacitor type fractal converter is improved. Therefore, the present disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter.

[0084] In some embodiments, the harmonic generation module includes n harmonic generation inverters; wherein n is a positive integer greater than 1.

[0085] The n harmonic generation inverters are respectively connected with the multiple input ends of the fractal connector module.

[0086] The switching frequency of the switching device of the i-th harmonic generation inverter is greater than the switching frequency of the switching device of the i-1-th harmonic generation inverter; wherein i is a positive integer less than or equal to n.

[0087] The harmonic generation inverter is used to generate a second harmonic signal according to a first harmonic signal in a corresponding high-order harmonic interval of a three-level flying capacitor type inverter.

[0088] For example, n is taken as 3 for introduction. Continue to refer to Figure 2The harmonic generation module 20 includes three harmonic generation inverters 200, the three harmonic generation inverters 200 are connected with the multiple input ends of the fractal connector module 30 respectively, the switching frequency of the switching device of the third harmonic generation inverter 200 is greater than the switching frequency of the switching device of the second harmonic generation inverter 200, and the switching frequency of the switching device of the second harmonic generation inverter 200 is greater than the switching frequency of the switching device of the first harmonic generation inverter 200. Therefore, the third harmonic generation inverter 200 is used for compensating the highest order harmonic signal, the first harmonic generation inverter 200 is used for compensating the lowest order harmonic signal, and the second harmonic generation inverter 200 is used for compensating the intermediate order harmonic signal. For example, in the case that the three-level flying capacitor type inverter 100 can generate the first harmonic signal in the third harmonic interval, the first harmonic signal in the fifth harmonic interval and the first harmonic signal in the seventh harmonic interval, the third harmonic generation inverter 200 is used for generating the second harmonic signal in the corresponding seventh harmonic interval according to the first harmonic signal in the seventh harmonic interval, the second harmonic generation inverter 200 is used for generating the second harmonic signal in the corresponding fifth harmonic interval according to the first harmonic signal in the fifth harmonic interval, and the first harmonic generation inverter 200 is used for generating the second harmonic signal in the corresponding third harmonic interval according to the first harmonic signal in the third harmonic interval. Each harmonic generation inverter 200 is only used for generating the second harmonic signal in the corresponding harmonic interval, and does not need to generate the second harmonic signal in other harmonic intervals. Therefore, in the case of using multiple harmonic generation inverters 200, the total capacity of each harmonic generation inverter 200 is the same as the capacity of using only one harmonic generation inverter 200. However, due to the reduction of the capacity of the single harmonic generation inverter 200, the manufacturing cost of the single harmonic generation inverter 200 is greatly reduced. Therefore, compared with using only one harmonic generation inverter 200, the cost of using multiple harmonic generation inverters 200 for harmonic compensation is lower.

[0089] In some embodiments, Figure 3 A structural schematic diagram of a three-level flying capacitor type inverter provided by the embodiments of the present disclosure is shown in FIG. 1. Figure 3 As shown in FIG. 1, the three-level flying capacitor type inverter 100 includes three bridge arms 50.

[0090] Any bridge arm 50 includes a first switching unit 110, a second switching unit 120, a third switching unit 130, a fourth switching unit 140, and a flying capacitor C0.

[0091] The first switching unit 110, the second switching unit 120, the third switching unit 130 and the fourth switching unit 140 each include at least one semiconductor power switching unit.

[0092] The first end of the first switch unit 110 is connected with the positive end of the first DC power supply port 41, the second end of the first switch unit 110 is connected with the first end of the second switch unit 120 at the first connection point A, the second end of the second switch unit 120 is connected with the first end of the third switch unit 130 at the bridge arm midpoint B, the second end of the third switch unit 130 is connected with the first end of the fourth switch unit 140 at the second connection point C, the second end of the fourth switch unit 140 is connected with the negative end of the first DC power supply port 41, the first end of the flying capacitor C0 is connected with the first connection point A, and the second end of the flying capacitor C0 is connected with the second connection point C.

[0093] The bridge arm midpoints B of the three bridge arms 50 are connected with the fractal connector module 30.

[0094] For example, the control end of the first switch unit 110, the control end of the second switch unit 120, the control end of the third switch unit 130 and the control end of the fourth switch unit 140 are connected with a control module (not shown in the figure), and the pulse width modulation signals output by the control module control the conduction and turn-off of the first switch unit 110, the second switch unit 120, the third switch unit 130 and the fourth switch unit 140 respectively, so as to realize that each phase bridge arm 50 outputs the first level, the second level and the third level with different voltage sizes.

[0095] Taking one of the three bridge arms 50 as an example, the power supply voltage of the first DC power supply port 41 is U. When the first switch unit 110 and the second switch unit 120 are turned on, and the third switch unit 130 and the fourth switch unit 140 are turned off, the bridge arm midpoint B outputs the first level of voltage U. When the first switch unit 110 and the third switch unit 130 are turned on, and the second switch unit 120 and the fourth switch unit 140 are turned off, the bridge arm midpoint B outputs the second level of voltage . When the second switch unit 120 and the fourth switch unit 140 are turned on, and the first switch unit 110 and the third switch unit 130 are turned off, the bridge arm midpoint B outputs the second level of voltage . When the third switch unit 130 and the fourth switch unit 140 are turned on, and the first switch unit 110 and the second switch unit 120 are turned off, the bridge arm midpoint B outputs the third level of voltage 0. By controlling the conduction of the three bridge arms 50, the line voltage output by the three-level flying capacitor type inverter 100 is a multi-level voltage signal with voltage U, 0, -U, and finally an alternating current signal is output on the alternating current side.

[0096] Furthermore, the first switching unit 110, the second switching unit 120, the third switching unit 130, and the fourth switching unit 140 all include semiconductor power switching units. By reducing the switching frequency of the semiconductor power switching units, the device losses of each switching unit of the three-level flying capacitor inverter can be reduced, thereby enabling the three-level flying capacitor inverter to output greater power.

[0097] In some embodiments, the first switching unit, the second switching unit, the third switching unit, and the fourth switching unit each include a plurality of semiconductor power switching units.

[0098] The semiconductor power switching unit includes at least one of the following: integrated gate commutated thyristor (IGCT), insulated gate bipolar transistor (IGBT), injection enhanced gate transistor (IEGT), and metal-oxide-semiconductor field-effect transistor (MOSFET).

[0099] In some embodiments, multiple semiconductor power switch units are connected in series.

[0100] For example, Figure 4 This is a schematic diagram of the structure of a first switching unit provided in an embodiment of the present disclosure. The first switching unit, the second switching unit, the third switching unit, and the fourth switching unit may be the same or different. This embodiment uses the first switching unit as an example for description. Figure 4 As shown, the first switching unit includes multiple semiconductor power switching units 111 connected in series. Since the multiple semiconductor power switching units 111 are connected in series, the high voltage resistance capability of the first switching unit can be enhanced.

[0101] In some embodiments, multiple semiconductor power switching units are connected in parallel with each other.

[0102] For example, Figure 5 This is a schematic diagram of another first switching unit provided in an embodiment of the present disclosure. The first switching unit, second switching unit, third switching unit, and fourth switching unit may be the same or different. This embodiment uses the first switching unit as an example for description. Figure 5 As shown, the first switching unit includes multiple semiconductor power switching units 111 connected in parallel. Since the multiple semiconductor power switching units 111 are connected in parallel, the current carrying capacity of the first switching unit can be enhanced.

[0103] Figure 6 This is a schematic diagram of the structure of a semiconductor power switching unit provided in an embodiment of the present disclosure, as shown below. Figure 6 As shown, the semiconductor power switching unit includes a first resistor R1, a first capacitor C1, a first switch S1, and a second switch S2. The first terminal of the first resistor R1 is connected to the first terminal of the first capacitor C1, and the second terminal of the first resistor R1 is connected to the second terminal of the first capacitor C1. The first terminal of the first capacitor C1 is connected to the first terminal of the first switch S1, and the second terminal of the first switch S1 is connected to the first terminal of the second switch S2. The second terminal of the second switch S2 is also used to connect to an adjacent preceding semiconductor power switching unit, and the second terminal of the second switch S2 is also used to connect to an adjacent following semiconductor power switching unit. The first switch S1 can be one of an IGCT, IGBT, IEGT, and MOSFET, and the second switch S2 can be one of an IGBT, IEGT, MOSFET, and diode.

[0104] Figure 7 A schematic diagram of another semiconductor power switching unit provided in this disclosure embodiment is shown below. Figure 7 As shown, the semiconductor power switching unit includes a first Zener diode D1, a first diode D2, a second resistor R2, a second capacitor C2, and a third switch S3. The negative terminal of the first Zener diode D1 is connected to the first terminal of the second resistor R2, the first terminal of the second capacitor C2, and the negative terminal of the first diode D2. The positive terminal of the first Zener diode D1 is connected to the second terminal of the second resistor R2, the second terminal of the second capacitor C2, and the second terminal of the third switch S3. The first terminal of the third switch S3 is connected to the positive terminal of the first diode D2. The first terminal of the third switch S3 is also used to connect to the adjacent preceding semiconductor power switching unit, and the second terminal of the third switch S3 is also used to connect to the adjacent following semiconductor power switching unit. The third switch S3 can be one of IGCT, IGBT, IEGT, and MOSFET.

[0105] Figure 8 A schematic diagram of another semiconductor power switching unit provided in this disclosure embodiment is shown below. Figure 8As shown, the semiconductor power switching unit includes a third resistor R3, a third capacitor C3, and a fourth switch S4. The first terminal of the third resistor R3 is connected to the first terminal of the third capacitor C3, and the second terminal of the third resistor R3 is connected to the second terminal of the third capacitor C3. The first terminal of the third capacitor C3 is connected to the first terminal of the fourth switch S4, and the second terminal of the fourth switch S4 is connected to the second terminal of the third capacitor C3. The first terminal of the fourth switch S4 is also used to connect to the adjacent preceding semiconductor power switching unit, and the second terminal of the fourth switch S4 is also used to connect to the adjacent following semiconductor power switching unit. The fourth switch S4 can be one of IGCT, IGBT, IEGT, and MOSFET.

[0106] Figure 9 A schematic diagram of another semiconductor power switching unit provided in this disclosure embodiment is shown below. Figure 9 As shown, the semiconductor power switching unit includes a fourth resistor R4, a fifth resistor R5, a second diode D3, a fourth capacitor C4, and a fifth switch S5. The first terminal of the fourth resistor R4 is connected to the first terminal of the fifth resistor R5, the positive terminal of the second diode D3, and the first terminal of the fifth switch S5. The second terminal of the fourth resistor R4 is connected to the second terminal of the fourth capacitor C4 and the second terminal of the fifth switch S5. The second terminal of the fifth resistor R5 is connected to the negative terminal of the second diode D3 and the first terminal of the fourth capacitor C4. The first terminal of the fifth switch S5 is also used to connect to the adjacent preceding semiconductor power switching unit, and the second terminal of the fifth switch S5 is also used to connect to the adjacent following semiconductor power switching unit. The fifth switch S5 can be one of IGCT, IGBT, IEGT, and MOSFET.

[0107] In some embodiments, see continue to see Figure 3 When the semiconductor power switching unit includes an IGCT, the three-level flying capacitor inverter 100 also includes a clamping unit.

[0108] The clamping unit includes: a first clamping reactor L1, a second clamping reactor L2, a first clamping capacitor C5, a second clamping capacitor C6, a first clamping diode D4, a second clamping diode D5, a first clamping resistor R6, and a second clamping resistor R7.

[0109] The first end of the first clamping reactor L1 is connected with the positive terminal of the first DC power supply port 41, the second end of the first clamping reactor L1 is connected with the positive terminal of the first clamping diode D4, the negative terminal of the first clamping diode D4 is connected with the first end of the first clamping capacitor C5, the second end of the first clamping capacitor C5 is connected with the first end of the second clamping capacitor C6, the second end of the second clamping capacitor C6 is connected with the positive terminal of the second clamping diode D5, the negative terminal of the second clamping diode D5 is connected with the second end of the second clamping reactor L2, the first end of the second clamping reactor L2 is connected with the negative terminal of the first DC power supply port 41, the first end of the first clamping resistor R6 is connected with the first end of the first clamping reactor L1, and the second end of the first clamping resistor R6 is connected with the negative terminal of the first clamping diode D4; the first end of the second clamping resistor R7 is connected with the first end of the second clamping reactor L2, and the second end of the second clamping resistor R7 is connected with the positive terminal of the second clamping diode D5.

[0110] It should be noted that the clamping unit includes the first clamping reactor L1, the second clamping reactor L2, the first clamping capacitor C5, the second clamping capacitor C6, the first clamping diode D4, the second clamping diode D5, the first clamping resistor R6, and the second clamping resistor R7, and the connection relationship between the first clamping reactor L1, the second clamping reactor L2, the first clamping capacitor C5, the second clamping capacitor C6, the first clamping diode D4, the second clamping diode D5, the first clamping resistor R6, and the second clamping resistor R7 is only an example, which is not specifically limited herein.

[0111] Specifically, the clamping unit is used to limit the current change rate when the semiconductor power switch unit is turned on, and can limit the oscillation amplitude of the three-level flying capacitor type inverter AC side output voltage.

[0112] In some embodiments, the three-level flying capacitor type inverter further includes a support capacitor unit, and the support capacitor unit includes at least one support capacitor.

[0113] For example, continuing to refer to Figure 3 The support capacitor unit includes a first support capacitor C7 and a second support capacitor C8. The first end of the first support capacitor C7 is connected with the positive terminal of the first DC power supply port 41, the second end of the first support capacitor C7 is connected with the first end of the second support capacitor C8, and the second end of the second support capacitor C8 is connected with the negative terminal of the first DC power supply port 41. The first support capacitor C7 and the second support capacitor C8 are both used to stabilize the DC bus voltage provided by the first DC power supply port 41, so as to avoid the sudden change of the DC bus voltage.

[0114] In some embodiments, continuing to refer to Figure 3The three-level flying capacitor type inverter further comprises a first filter U1, a plurality of input ends of the first filter U1 are connected with the bridge arm midpoints B of the respective bridge arms 50, and an output end of the first filter U1 is connected with the first input end of the fractal connector module 30.

[0115] For example, the first filter U1 can be a passive filter composed of an inductor and a capacitor, or can be one of an L filter, an LC filter, an LCL filter, and an LCLL filter. The first filter U1 is used to filter out interference signals in the fundamental wave signal output by the bridge arm midpoints B of the respective bridge arms 50.

[0116] In some embodiments, Figure 10 A structure schematic diagram of another three-level flying capacitor type fractal converter provided by the embodiment of the present disclosure is shown in FIG. 3. Figure 10 As shown in FIG. 3, the fractal connector module 30 comprises a first winding 311, a second winding 312, and at least one third winding 313.

[0117] The first winding 311, the second winding 312, and the at least one third winding 313 are coupled and connected, the first winding 311 is connected with the alternating current side of the three-level flying capacitor type inverter 100, the second winding 312 is connected with the alternating current output port 43, and the third winding 313 is connected with the corresponding harmonic generation inverter 200.

[0118] For example, the first winding 311 can be a star-connected winding or an angle-connected winding, the second winding 312 can be a star-connected winding or an angle-connected winding, and the third winding 313 can be a star-connected winding or an angle-connected winding. After the switching frequency of the switching unit in the three-level flying capacitor type inverter 100 is reduced, the three-level flying capacitor type inverter 100 generates a first harmonic signal in a high-order harmonic interval. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor type inverter 100 are output to the first winding 311, and the second harmonic signal generated by the harmonic generation inverter 200 according to the first harmonic signal is output to the second winding 312. Since the signal waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal with the same value as the second harmonic signal, thereby realizing the compensation of the second harmonic signal to the first harmonic signal. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, thereby enhancing the maximum power output capability of the three-level flying capacitor type fractal converter and improving the output capacity of the three-level flying capacitor type fractal converter. Finally, the generated fundamental wave signal is output to the alternating current output port 43 through the third winding 313. Therefore, the present disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter.

[0119] In the case that the harmonic generation module 20 includes a plurality of harmonic generation inverters 200, the fractal connector module 30 includes the same number of third windings 313, the plurality of third windings 313 are connected with the corresponding harmonic generation inverters 200, and are coupled with other windings, so that the second harmonic signals of different high-order harmonic intervals generated by different harmonic generation inverters 200 can be introduced into the fractal connector module 30, thereby being able to compensate the first harmonic signals of different high-order harmonic intervals.

[0120] In some embodiments, the first winding 311 includes a delta winding.

[0121] Specifically, the delta winding can eliminate the first harmonic signals in the third harmonic interval, so that the harmonic generation inverter 200 only needs to generate the second harmonic signals of the high-order harmonic intervals other than the third harmonic interval, thereby reducing the capacity of the harmonic generation inverter 200, and thus reducing the manufacturing cost of the three-level flying capacitor type fractal converter.

[0122] In some embodiments, Figure 11 Another structure schematic diagram of a three-level flying capacitor type fractal converter provided by the embodiments of the present disclosure is shown in FIG. 6. Figure 11 As shown in FIG. 6, the fractal connector module 30 includes at least one fourth winding 321 and at least one fifth winding 322.

[0123] The fourth winding 321 is coupled with the corresponding fifth winding 322, the fourth winding 321 is connected with the alternating current side of the three-level flying capacitor type inverter 100, the fifth winding 322 is connected with the corresponding harmonic generation inverter 200, and the alternating current side of the three-level flying capacitor type inverter 100 is connected with the alternating current output port 43.

[0124] For example, the fourth winding 321 can be a star winding or a delta winding, and the fifth winding 322 can be a star winding or a delta winding. After the switching frequency of the switching unit in the three-level flying capacitor type inverter 100 is reduced, the three-level flying capacitor type inverter 100 generates the first harmonic signals in the high-order harmonic interval. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor type inverter 100 are output to the fourth winding 321, and the second harmonic signal generated by the harmonic generation inverter 200 according to the first harmonic signal is output to the fifth winding 322. In the case that the voltage level between the alternating current side of the three-level flying capacitor type inverter 100 and the alternating current side of the harmonic generation inverter 200 does not match, the parallel transformer composed of the fourth winding 321 and the fifth winding 322 can match the voltage level between the alternating current side of the three-level flying capacitor type inverter 100 and the alternating current side of the harmonic generation inverter 200.

[0125] Since the signal waveform of the second harmonic signal is opposite to the signal waveform of the first harmonic signal, the second harmonic signal can cancel the part of the first harmonic signal with the same value as the second harmonic signal, thereby realizing the compensation of the second harmonic signal to the first harmonic signal. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, thereby enhancing the ability of the three-level flying capacitor type fractal converter to output maximum power and improving the output capacity of the three-level flying capacitor type fractal converter. Therefore, the present disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter.

[0126] In the case where the harmonic generation module 20 includes a plurality of harmonic generation inverters 200, the fractal connector module 30 includes the same number of fourth windings 321 and fifth windings 322, the plurality of fourth windings 321 are connected with the corresponding three-level flying capacitor type inverters 100, the plurality of fifth windings 322 are connected with the corresponding harmonic generation inverters 200, and the plurality of fourth windings 321 are also coupled with the corresponding fifth windings 322, thereby realizing the introduction of the second harmonic signals of different high-order harmonic intervals generated by different harmonic generation inverters 200 into the fractal connector module 30, so as to compensate the first harmonic signals of different high-order harmonic intervals.

[0127] In some embodiments, Figure 12 Another structure schematic diagram of a three-level flying capacitor type fractal converter is provided by the present disclosure, as shown in Figure 12 The fractal connector module 30 includes at least one connecting component 323.

[0128] The alternating current side of the three-level flying capacitor type inverter 100 is connected with the alternating current side of the corresponding harmonic generation inverter 200 through the connecting component 323, so that the alternating current side of the three-level flying capacitor type inverter 100 is connected in parallel with the alternating current side of the corresponding harmonic generation inverter 200; and the alternating current side of the three-level flying capacitor type inverter 200 is connected with the alternating current output port 43.

[0129] The first harmonic signal in the high harmonic range is generated by the three-level flying capacitor inverter 100 when the switching frequency of the switching unit in the three-level flying capacitor inverter 100 is reduced. The three-level flying capacitor inverter 100 and the harmonic generating inverter 200 are connected in parallel in the fractal connector module 30 through the connecting component 323. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor inverter 100 are output to the fractal connector module 30. The second harmonic signal generated by the harmonic generating inverter 200 according to the first harmonic signal is output to the fractal connector module 30. The second harmonic signal compensates the first harmonic signal at the connection between the three-level flying capacitor inverter 100 and the harmonic generating inverter 200 connected through the connecting component 323. The voltage levels of the alternating current side output voltage of the three-level flying capacitor inverter 100 and the alternating current side output voltage of the harmonic generating inverter 200 are matched.

[0130] Since the signal waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal with the same value as the second harmonic signal, thereby realizing the compensation of the second harmonic signal to the first harmonic signal. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, thereby enhancing the ability of the three-level flying capacitor fractal converter to output maximum power and improving the output capacity of the three-level flying capacitor fractal converter. Therefore, the disclosure realizes the reduction of the switching frequency of the three-level flying capacitor fractal converter while improving the output capacity of the converter.

[0131] In some embodiments, Figure 13 Another structure schematic diagram of a three-level flying capacitor fractal converter is provided in the disclosure, Figure 13 As shown, the fractal connector module 30 includes at least one series transformer 330.

[0132] The first input end of the series transformer 330 is connected with the alternating current side of the three-level flying capacitor inverter 100. The second input end of the series transformer 330 is connected with the alternating current side of the corresponding harmonic generating inverter 200. The output end of the series transformer 330 is connected with the alternating current output port 43.

[0133] For example, after the switching frequency of the switching unit in the three-level flying capacitor type inverter 100 is reduced, the three-level flying capacitor type inverter 100 generates a first harmonic signal in a high-order harmonic interval. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor type inverter 100 are output to the series transformer 330, and the second harmonic signal generated by the harmonic generation inverter 200 according to the first harmonic signal is also output to the series transformer 330. Since the signal waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal with the same value as the second harmonic signal, thereby realizing the compensation of the first harmonic signal by the second harmonic signal. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, thereby enhancing the ability of the three-level flying capacitor type fractal converter to output maximum power and improving the output capacity of the three-level flying capacitor type fractal converter. The finally generated fundamental wave signal is output to the AC output port 43 through the series transformer 330. Therefore, the present disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter.

[0134] In the case where the harmonic generation module 20 includes a plurality of harmonic generation inverters 200, the fractal connector module 30 includes the same number of series transformers 330, and the plurality of series transformers 330 are connected with the corresponding harmonic generation inverters 200 and connected with the AC side of the three-level flying capacitor type inverter 100, thereby realizing the introduction of the second harmonic signals of different high-order harmonic intervals generated by different harmonic generation inverters 200 into the fractal connector module 30, so as to compensate the first harmonic signals of different high-order harmonic intervals.

[0135] In some embodiments, Figure 14 A structural schematic diagram of a series transformer provided by an embodiment of the present disclosure is shown in FIG. 4. Figure 14 As shown in FIG. 4, the series transformer 330 includes a first transformer 331, a second transformer 332, and a third transformer 333.

[0136] The first end of the first transformer 331 is connected with the first output end of the three-level flying capacitor type inverter 100, the second end of the first transformer 331 is connected with the first end of the AC output port 43, the third end of the first transformer 331 is connected with the neutral point or the ground end, and the fourth end of the first transformer 331 is connected with the first output end of the harmonic generation inverter 200.

[0137] The first end of the second transformer 332 is connected with the second output end of the three-level flying capacitor inverter 100, the second end of the second transformer 332 is connected with the second end of the alternating current output port 43, the third end of the second transformer 332 is connected with a neutral point or a ground end, and the fourth end of the second transformer 332 is connected with the second output end of the harmonic generating inverter 200.

[0138] The first end of the third transformer 333 is connected with the third output end of the three-level flying capacitor inverter 100, the second end of the third transformer 333 is connected with the third end of the alternating current output port 43, the third end of the third transformer 333 is connected with a neutral point or a ground end, and the fourth end of the third transformer 333 is connected with the third output end of the harmonic generating inverter 200.

[0139] Specifically, after the switching frequency of the switching unit in the three-level flying capacitor inverter 100 is reduced, the three-level flying capacitor inverter 100 generates a first harmonic signal in a high-order harmonic interval. The fundamental wave signal generated by the three-level flying capacitor inverter 100 and the first harmonic signal are respectively output from different output ends, the second harmonic signal generated by the harmonic generating inverter 200 according to the first harmonic signal is also output through different output ends, and the harmonic signals output from different output ends of the three-level flying capacitor inverter 100 and the harmonic signals output from different output ends of the harmonic generating inverter 200 are all input into the first transformer 331, the second transformer 332 and the third transformer 333. Since the signal waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal with the same value as the second harmonic signal, thereby realizing the compensation of the second harmonic signal to the first harmonic signal. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, thereby enhancing the ability of the three-level flying capacitor inverter to output maximum power and improving the output capacity of the three-level flying capacitor inverter. Therefore, the disclosure realizes the reduction of the switching frequency of the three-level flying capacitor inverter while improving the output capacity of the inverter.

[0140] In some embodiments, Figure 15 Another structure schematic diagram of a series transformer provided by the embodiments of the disclosure is shown in FIG. 6. Figure 15 As shown in FIG. 6, 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.

[0141] The first single-phase winding 334, the second single-phase winding 335, and the third single-phase winding 336 are coupled to the sixth winding 337; the first end of the first single-phase winding 334 is connected to the first output end of the three-level flying capacitor type inverter 100, and the second end of the first single-phase winding 334 is connected to the first end of the alternating current output port 43; the first end of the second single-phase winding 335 is connected to the second output end of the three-level flying capacitor type inverter 100, and the second end of the second single-phase winding 335 is connected to the second end of the alternating current output port 43; the first end of the third single-phase winding 336 is connected to the third output end of the three-level flying capacitor type inverter 100, and the second end of the third single-phase winding 336 is connected to the third end of the alternating current output port 43; the sixth winding 337 is connected to the first output end of the harmonic generation inverter 200, the second output end of the harmonic generation inverter 200, and the third output end of the harmonic generation inverter 200.

[0142] Specifically, the sixth winding 337 can be a star-connected winding or an angle-connected winding. After the switching frequency of the switching unit in the three-level flying capacitor type inverter 100 is reduced, the three-level flying capacitor type inverter 100 generates a first harmonic signal in a high-order harmonic interval. The fundamental wave signal and the first harmonic signal generated by the three-level flying capacitor type inverter 100 are respectively output from different output ends. The second harmonic signal generated by the harmonic generation inverter 200 according to the first harmonic signal is also output through different output ends. The harmonic signals output from different output ends of the three-level flying capacitor type inverter 100 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 ends of the harmonic generation inverter 200 are all output to the sixth winding 337. Since the signal waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal that has the same value as the second harmonic signal. Thus, the second harmonic signal compensates for the first harmonic signal. Due to the reduction of the harmonic signal, the loss caused by the harmonic signal is also reduced, thereby enhancing the ability of the three-level flying capacitor type inverter to output maximum power and improving the output capacity of the three-level flying capacitor type inverter. Therefore, the disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type inverter while improving the output capacity of the inverter.

[0143] In some embodiments, the harmonic generation inverter includes one of a two-level inverter, a three-level inverter, a five-level inverter, a multi-level inverter, a modular multi-level inverter, and a cascaded H-bridge inverter.

[0144] Exemplarily, in the case that the harmonic generation inverter comprises a two-level inverter, or a three-level inverter, or a five-level inverter, the three-level flying capacitor type fractance converter further comprises a second filter. The second filter can be one of a passive filter composed of an inductor and a capacitor, an L filter, an LC filter, an LCL filter, and an LCLL filter.

[0145] Exemplarily, Figure 16 A structural schematic diagram of a harmonic generation inverter provided by an embodiment of the present disclosure is shown in FIG. 2. Figure 16 As shown in FIG. 2, the harmonic generation inverter comprises 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, a sixth semiconductor switch 216, and a detection module (not shown in the figure), and the three-level flying capacitor type fractance converter further comprises a second filter 220.

[0146] 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 comprise at least one semiconductor power switch unit.

[0147] The first end of the first semiconductor switch 211 is connected to the positive terminal of the second DC power supply port 42, and the second end of the first semiconductor switch 211 is connected to the first end of the second semiconductor switch 212 in the first bridge arm midpoint D. The second end of the second semiconductor switch 212 is connected to the negative terminal of the second DC power supply port 42.

[0148] The first end of the third semiconductor switch 213 is connected to the positive terminal of the second DC power supply port 42, and the second end of the third semiconductor switch 213 is connected to the first end of the fourth semiconductor switch 214 in the second bridge arm midpoint E. The second end of the fourth semiconductor switch 214 is connected to the negative terminal of the second DC power supply port 42.

[0149] The first end of the fifth semiconductor switch 215 is connected to the positive terminal of the second DC power supply port 42, and the second end of the fifth semiconductor switch 215 is connected to the first end of the sixth semiconductor switch 216 in the third bridge arm midpoint F. The second end of the sixth semiconductor switch 216 is connected to the negative terminal of the second DC power supply port 42.

[0150] The first bridge arm midpoint D, the second bridge arm midpoint E, and the third bridge arm midpoint F are each connected to a plurality of input terminals of the second filter 220, and the output terminal of the second filter 220 is connected to the second input terminal of the fractance connector module 30.

[0151] Specifically, the detection module is configured to detect a first harmonic signal generated by the three-level flying capacitor type inverter, and provide the first harmonic signal to a control module (not shown in the figure). The control module controls the turn-on and turn-off of 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 according to the first harmonic signal, so that 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 output a second harmonic signal with a waveform opposite to that of the first harmonic signal, and output the second harmonic signal to the fractal connector module 30 through the second filter 220. Since the waveform of the second harmonic signal is opposite to that of the first harmonic signal, the second harmonic signal can offset the part of the first harmonic signal with the same value as the second harmonic signal in the fractal connector module 30, so as to realize the compensation of the second harmonic signal to the first harmonic signal. Since the harmonic signal is reduced, the loss caused by the harmonic signal is also reduced, so that the ability of the three-level flying capacitor type fractal converter to output maximum power is enhanced, and the output capacity of the three-level flying capacitor type fractal converter is improved. Therefore, the disclosure realizes the reduction of the switching frequency of the three-level flying capacitor type fractal converter while improving the output capacity of the converter.

[0152] The above is only a specific embodiment of the disclosure, which enables those skilled in the art to understand or implement the disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the disclosure. Therefore, the disclosure will not be limited to these embodiments herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A three-level flying capacitor fractal converter, characterized in that, include: An inverter module includes a three-level flying capacitor inverter, wherein the DC side of the three-level flying capacitor inverter is connected to a first DC power supply port; wherein the three-level flying capacitor inverter is used to output an AC signal; the AC signal includes a first harmonic signal in the higher harmonic range; The harmonic generation module includes at least one harmonic generation inverter, the DC side of which is connected to a second DC power supply port; the harmonic generation inverter is used to generate a second harmonic signal based on the first harmonic signal. The fractal connector module has a first input terminal connected to the AC side of the three-level flying capacitor inverter, a second input terminal connected to the AC side of the harmonic generation inverter, and an output terminal 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 flying capacitor type fractal converter according to claim 1, characterized in that, The harmonic generation module includes n harmonic generation inverters; where n is a positive integer greater than 1. The n harmonic generation inverters are respectively connected to multiple input terminals of the fractal connector module; 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; where i is a positive integer less than or equal to n. The harmonic generation inverter is used to generate the second harmonic signal based on the first harmonic signal within the higher harmonic range corresponding to the three-level flying capacitor inverter.

3. The three-level flying capacitor type fractal converter according to claim 1, characterized in that, The three-level flying capacitor inverter includes three bridge arms; Each of the bridge arms includes a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, and a flying capacitor; The first switching unit, the second switching unit, the third switching unit, and the fourth switching unit each include at least one semiconductor power switching unit; The first end of the first switching unit is connected to the positive terminal of the first DC power supply port; the second end of the first switching unit is connected to the first end of the second switching unit at a first connection point; the second end of the second switching unit is connected to the first end of the third switching unit at the midpoint of the bridge arm; the second end of the third switching unit is connected to the first end of the fourth switching unit at a second connection point; the second end of the fourth switching unit is connected to the negative terminal of the first DC power supply port; the first end of the flying capacitor is connected to the first connection point; and the second end of the flying capacitor is connected to the second connection point. The midpoints of all three bridge arms are connected to the fractal connector module.

4. The three-level flying capacitor type fractal converter according to claim 3, characterized in that, The first switching unit, the second switching unit, the third switching unit, and the fourth switching unit each include a plurality of the semiconductor power switching units; The semiconductor power switching unit includes at least one of IGCT, IGBT, IEGT, and MOSFET.

5. The three-level flying capacitor type fractal converter according to claim 4, characterized in that, Multiple semiconductor power switch units are connected in series. Alternatively, multiple semiconductor power switching units may be connected in parallel with each other.

6. The three-level flying capacitor type fractal converter according to claim 3, characterized in that, The semiconductor power switching unit includes an IGCT; the three-level flying capacitor inverter also includes a clamping unit. The clamping unit is used to limit the rate of change of the current of the semiconductor power switch unit when the semiconductor power switch unit is turned on, and to limit the oscillation amplitude of the AC side output voltage of the three-level flying capacitor inverter.

7. The three-level flying capacitor type fractal converter according to claim 6, characterized in that, The clamping unit includes: a first clamping reactor, a second clamping reactor, a first clamping capacitor, a second clamping capacitor, a first clamping diode, a second clamping diode, a first clamping resistor, and a second clamping resistor; The first terminal of the first clamping reactor is connected to the positive terminal of the first DC power supply port. The second terminal of the first clamping reactor is connected to the positive terminal of the first clamping diode. The negative terminal of the first clamping diode is connected to the first terminal of the first clamping capacitor. The second terminal of the first clamping capacitor is connected to the first terminal of the second clamping capacitor. The second terminal of the second clamping capacitor is connected to the positive terminal of the second clamping diode. The negative terminal of the second clamping diode is connected to the second terminal of the second clamping reactor. The first terminal of the second clamping reactor is connected to the negative terminal of the first DC power supply port. The first terminal of the first clamping resistor is connected to the first terminal of the first clamping reactor. The second terminal of the first clamping resistor is connected to the negative terminal of the first clamping diode. The first terminal of the second clamping resistor is connected to the first terminal of the second clamping reactor. The second terminal of the second clamping resistor is connected to the positive terminal of the second clamping diode.

8. The three-level flying capacitor fractal converter according to any one of claims 1-7, characterized in that, The fractal connector module includes: a first winding, a second winding, and at least one third winding; The first winding, the second winding, and at least one of the third windings are coupled together. The first winding is connected to the AC side of the three-level flying capacitor inverter, the second winding is connected to the AC output port, and the third winding is connected to the corresponding harmonic generating inverter.

9. The three-level flying capacitor type fractal converter according to claim 8, characterized in that, The first winding includes an angle-connected winding.

10. The three-level flying capacitor fractal converter according to any one of claims 1-7, 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 connected to the AC side of the three-level flying capacitor inverter, the fifth winding is connected to the corresponding harmonic generating inverter, and the AC side of the three-level flying capacitor inverter is connected to the AC output port.

11. The three-level flying capacitor fractal converter according to any one of claims 1-7, characterized in that, The fractal connector module includes: at least one connecting component; The AC side of the three-level flying capacitor inverter is connected to the AC side of the corresponding harmonic generating inverter through the connecting component, so that the AC side of the three-level flying capacitor inverter and the AC side of the corresponding harmonic generating inverter are connected in parallel; the AC side of the three-level flying capacitor inverter is connected to the AC output port.

12. The three-level flying capacitor fractal converter according to any one of claims 1-7, characterized in that, The fractal connector module includes at least one series transformer; The first input terminal of the series transformer is connected to the AC side of the three-level flying capacitor inverter, the second input terminal of the series transformer is connected to the AC side of the corresponding harmonic generation inverter, and the output terminal of the series transformer is connected to the AC output port.

13. The three-level flying capacitor type fractal converter according to claim 12, 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 connected to the first output terminal of the three-level flying capacitor inverter, the second terminal of the first transformer is connected to the first terminal of the AC output port, the third terminal of the first transformer is connected to the neutral point or ground terminal, and the fourth terminal of the first transformer is connected to the first output terminal of the harmonic generation inverter. The first terminal of the second transformer is connected to the second output terminal of the three-level flying capacitor inverter, the second terminal of the second transformer is connected to the second terminal of the AC output port, the third terminal of the second transformer is connected to the neutral point or ground terminal, and the fourth terminal of the second transformer is connected to the second output terminal of the harmonic generation inverter. The first terminal of the third transformer is connected to the third output terminal of the three-level flying capacitor inverter, the second terminal of the third transformer is connected to the third terminal of the AC output port, the third terminal of the third transformer is connected to the neutral point or ground terminal, and the fourth terminal of the third transformer is connected to the third output terminal of the harmonic generation inverter.

14. The three-level flying capacitor type fractal converter according to claim 12, 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 coupled to the sixth winding; the first end of the first single-phase winding is connected to the first output terminal of the three-level flying capacitor inverter, and the second end of the first single-phase winding is connected to the first terminal of the AC output port; the first end of the second single-phase winding is connected to the second output terminal of the three-level flying capacitor inverter, and the second end of the second single-phase winding is connected to the second terminal of the AC output port; the first end of the third single-phase winding is connected to the third output terminal of the three-level flying capacitor inverter, and the second end of the third single-phase winding is connected to the third terminal of the AC output port; the sixth winding is connected to the first output terminal, the second output terminal, and the third output terminal of the harmonic generation inverter.

15. The three-level flying capacitor fractal converter according to any one of claims 1-7, characterized in that, Also includes: A first filter, wherein multiple input terminals of the first filter are electrically connected to the AC side of the three-level flying capacitor inverter, and the output terminal of the first filter is electrically connected to the first input terminal of the fractal connector module; And / or, a second filter, wherein multiple input terminals of the second filter are electrically connected to the AC side of the corresponding harmonic generating inverter, and the output terminal of the second filter is electrically connected to the corresponding second input terminal in the fractal connector module.

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