Interleaved flyback inverter, low-power optimization method thereof and photovoltaic equipment

Abstract

The invention relates to an interleaved flyback inverter, a low power optimization method thereof and a photovoltaic device comprising such an interleaved flyback inverter. The interlaced flyback inverter comprises a pre-stage circuit structure and a post-stage circuit structure, the pre-stage circuit structure comprises a first flyback circuit and a second flyback circuit which are connected in parallel, and the first flyback circuit comprises a switch S1. The inverter further comprises a control unit, the control unit comprises a low-power optimization module, and when the inverter is in a low-power working condition, the second flyback circuit in the pre-stage circuit structure is turned off and the low-power optimization module is started in a DCM mode. And the low power optimization module is configured to: determine a DCM duty cycle and a DCM period of a switch S1 of a first flyback circuit in the pre-stage circuit structure; utilizing the determined DCM duty ratio and DCM period to respectively update a register comparison value and a register period of the control unit for frequency conversion control; and enabling a first flyback circuit in the pre-stage circuit structure based on the updated register comparison value and the register period.

Description

Technical Field

[0001] The present disclosure relates to the field of photovoltaic technology, and more particularly to an interleaved flyback inverter and a low-power optimization method thereof, and a photovoltaic device including such an interleaved flyback inverter. Background Art

[0002] In recent years, with the increasing depletion of fossil energy and the intensification of the greenhouse effect, the future society is facing a huge energy crisis and environmental deterioration risk. In order to meet this challenge, countries around the world have begun to develop new power generation technologies such as photovoltaics, wind turbines, and fuel cells. Photovoltaic solar power generation has become a research hotspot because of its simple acquisition method, high energy conversion rate, and simple equipment installation. The photovoltaic inverter is an important component that converts the direct current generated by the photovoltaic module into alternating current and integrates the electrical energy into the power grid.

[0003] As for the grid-connected micro photovoltaic inverters in photovoltaic inverters, most products on the market are currently implemented based on the parallel interleaved flyback inverter topology. The structure of this type of inverter mainly includes two parts: the front-stage circuit and the rear-stage circuit. Among them, the front-stage circuit is composed of a master-slave two-bridge flyback topology, and the rear-stage circuit is connected to the grid by a single H-bridge. The traditional control method of this type of structure is to control it through a mixed control mode of BCM (Boundary Current Modulation) variable frequency and DCM (Discontinuous Current Modulation) fixed frequency. However, due to the large energy consumption of the power switch during DCM fixed frequency control, this control method will result in high power consumption and low energy conversion efficiency when DCM fixed frequency is implemented under low power output conditions. Summary of the invention

[0004] In order to achieve power reduction when a micro inverter is running at low power, thereby achieving the purpose of reducing switching losses and improving product efficiency, the present disclosure provides an improved interleaved flyback inverter and a low-power optimization method thereof, as well as a photovoltaic device including such an interleaved flyback inverter, by adding a low-power optimization module to a control unit of the interleaved flyback inverter.

[0005] According to one aspect of the present disclosure, an interleaved flyback inverter is provided. The interleaved flyback inverter may include a front-stage circuit structure and a rear-stage circuit structure, wherein the front-stage circuit structure is connected to a photovoltaic module and is used to output a direct current signal to the rear-stage circuit structure, and the rear-stage circuit structure is used to convert the direct current signal into an alternating current signal, wherein the front-stage circuit structure includes a first flyback circuit and a second flyback circuit connected in parallel, and the first flyback circuit includes a switch S 1The interleaved flyback inverter may further include a control unit, wherein the control unit includes a low-power optimization module. When the interleaved flyback inverter is in a low-power operating condition, the second flyback circuit in the front-stage circuit structure may be turned off in the DCM mode and the low-power optimization module may be enabled, and the low-power optimization module may be configured to: determine the switch S of the first flyback circuit in the front-stage circuit structure; 1 The invention relates to a method for realizing a control system for controlling a frequency conversion control of a first flyback circuit in a first stage circuit structure and a control system for controlling a frequency conversion control of a first flyback circuit in a first stage circuit structure. The method comprises: determining a DCM duty cycle and a DCM cycle; updating a register comparison value and a register period of the control unit for frequency conversion control using the determined DCM duty cycle and the DCM period; and enabling the first flyback circuit in the first stage circuit structure based on the updated register comparison value and the register period.

[0006] According to another aspect of the present disclosure, a photovoltaic device is provided, which may include the interleaved flyback inverter described in the present disclosure or may be connected to the interleaved flyback inverter described in the present disclosure.

[0007] According to yet another aspect of the present disclosure, a low-power optimization method for an interleaved flyback inverter is provided. The interleaved flyback inverter may include a front-stage circuit structure and a rear-stage circuit structure, wherein the front-stage circuit structure is connected to a photovoltaic module and is used to output a direct current signal to the rear-stage circuit structure, and the rear-stage circuit structure is used to convert the direct current signal into an alternating current signal, wherein the front-stage circuit structure includes a first flyback circuit and a second flyback circuit connected in parallel, and the first flyback circuit includes a switch S 1 The low-power optimization method may include, when the interleaved flyback inverter is in a low-power operating condition, in a DCM mode: shutting down the second flyback circuit in the front-stage circuit structure and enabling a low-power optimization module of a control unit of the interleaved flyback inverter; determining, by the low-power optimization module, the switch S of the first flyback circuit in the front-stage circuit structure. 1 The low-power optimization module uses the determined DCM duty cycle and DCM cycle to respectively update the register comparison value and register cycle used by the control unit for variable frequency control; and the low-power optimization module enables the first flyback circuit in the previous stage circuit structure based on the updated register comparison value and register cycle.

[0008] According to yet another aspect of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium stores instructions, and when the instructions are executed by a processor, the steps of the interleaved flyback inverter low-power optimization method described in the present disclosure are implemented.

[0009] According to yet another aspect of the present disclosure, a computer program product is provided, wherein the computer program product comprises instructions, and when the instructions are executed by a processor, the steps of the interleaved flyback inverter low-power optimization method described in the present disclosure are implemented.

[0010] These and other aspects and features of the present disclosure will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to be able to understand the present disclosure in detail, a more specific description of the present disclosure briefly summarized above can be obtained by reference to the embodiments, some of which are shown in the accompanying drawings. In order to facilitate understanding, similar reference numerals have been used as much as possible to indicate similar elements common to the various figures. However, it should be noted that the drawings only show typical embodiments of the present disclosure and therefore should not be considered to limit the scope of the present disclosure, as the present disclosure may allow other equivalent embodiments. In the accompanying drawings:

[0012] Figure 1 A typical topology diagram of an interleaved flyback microinverter according to an embodiment of the present disclosure is shown.

[0013] Figure 2 A reference curve diagram of primary peak current at different output powers according to an embodiment of the present disclosure is shown.

[0014] Figure 3 A schematic diagram showing the corresponding relationship between the primary peak current reference and the main switching frequency of a traditional micro inverter is shown.

[0015] Figure 4 A block diagram of an exemplary low power optimization control strategy according to an embodiment of the present disclosure is shown.

[0016] Figure 5 A schematic diagram of switching between a low power optimization module and a BCM and DCM hybrid control module according to an embodiment of the present disclosure is shown.

[0017] Figure 6 A schematic diagram showing the corresponding relationship between the primary peak current reference calculated by open loop and the main switch frequency of the interleaved flyback inverter according to an embodiment of the present disclosure is shown.

[0018] Figure 7 A schematic flow chart of a low-power optimization method for an interleaved flyback inverter according to an embodiment of the present disclosure is shown.

[0019] Figure 8 A schematic flow chart of an overall control strategy of an interleaved flyback inverter according to an embodiment of the present disclosure is shown. The control strategy includes Figure 7 Low power optimization method.

[0020] It is contemplated that elements of one embodiment of the disclosure may be beneficially applied to other embodiments without further recitation. DETAILED DESCRIPTION

[0021] The specific embodiments of the present disclosure are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but it should be understood by those skilled in the art that the present disclosure can be implemented without some or all of these specific details, and therefore the present disclosure is not limited to the specific embodiments disclosed below. On the other hand, no specific description of well-known processes or procedures, etc., is provided to avoid unnecessarily obscuring the present disclosure.

[0022] Furthermore, it is to be appreciated that the various embodiments shown in the figures are illustrative and that the figures are not necessarily drawn to scale.

[0023] The present disclosure uses specific words to describe the embodiments of the present disclosure. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present disclosure. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different locations of the present disclosure does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of the present disclosure may be appropriately combined.

[0024] In the present disclosure, unless otherwise specified, the technical terms or scientific terms used in the claims and the specification shall have the usual meanings understood by ordinary technicians in the technical field to which the present disclosure belongs. "First", "second", "(a)", "(b)", "(c)", "(d)", and similar expressions used in the present disclosure and the claims do not indicate any order, quantity or importance, but are only used to distinguish different components. In addition, similar words such as "include" or "comprise" mean that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalent elements, and do not exclude other elements or objects. Similar words such as "connect" or "connected" are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections. In addition, in the present disclosure, the use of similar words such as "about" or "approximately" means within the range of ±10% of the nominal value.

[0025] The technology described in the present disclosure may be implemented at least in part in hardware, software, firmware, or any combination thereof. The terms "processor", "processing circuit", "controller", "control unit", "control module", or similar terms used in the present disclosure may include, but are not limited to, one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuits, and any combination of such components embodied in a programmer. The term "low power" used in the present disclosure should be understood as the common meaning recognized by those skilled in the art. In some exemplary embodiments, low power may be, for example, less than 100W, for example, 50W.

[0026] Exemplary embodiments of the present disclosure are described in more detail below in conjunction with the accompanying drawings. It should be noted that the present disclosure can be applied to all interleaved parallel flyback topologies.

[0027] Reference now Figure 1 , Figure 1 A typical topology diagram of an example interleaved flyback microinverter 100 according to one or more embodiments of the present disclosure is shown. The inverter 100 may include a front-stage circuit structure 110 and a rear-stage circuit structure 120. The front-stage circuit structure 110 may be connected to a photovoltaic module PV. The front-stage circuit structure 110 may be used to output a direct current signal to the rear-stage circuit structure 120. The rear-stage circuit structure 120 may be used to convert a direct current signal received from the front-stage circuit structure 110 into an alternating current signal.

[0028] The front stage circuit structure 110 may include a first flyback circuit and a second flyback circuit connected in parallel. The first flyback circuit may include a switch S 1 The second flyback circuit may include a switch S 2 . In some embodiments, the structures of the first flyback circuit and the second flyback circuit may be the same. In other embodiments, the structures of the first flyback circuit and the second flyback circuit may be different. In some embodiments, the first flyback circuit and the second flyback circuit may work interchangeably. In other embodiments, it may be specified that the first flyback circuit is a master bridge circuit and the second flyback circuit is a slave bridge circuit. In addition, the post-stage circuit structure 120 may be an H-bridge circuit.

[0029] Figure 2 A reference curve graph 200 of primary peak current at different output powers according to one or more embodiments of the present disclosure is shown. In the application of the inverter, a suitable control strategy can be selected according to actual working conditions and requirements, and the working parameters of the master bridge and the slave bridge can be optimized to improve the efficiency and performance of the inverter. Figure 2 As shown in the figure, under the traditional control strategy, the inverter limitIn this state, when a mixed control strategy of BCM and DCM is adopted, the dual-path interleaved flyback BCM control is started under heavy load, and the master-slave bridge and the slave bridge work simultaneously; under light load and medium load conditions, only the master bridge works; especially under light load, only the single-path DCM mode operates.

[0030] BCM and DCM can be control strategies that are selected and optimized according to different working conditions and requirements. BCM has higher power density and is not complicated to control, which is suitable for higher power application scenarios. DCM is a control method with simple control and zero current shutdown characteristics, which is suitable for low power occasions.

[0031] exist Figure 2 In the embodiment shown, the predetermined output power threshold P limit Including P limit1 and P limit2 When the inverter output power is greater than P limit1 When the inverter is under heavy load, its primary peak current reference curve is as follows: Figure 2 As shown in the upper curve. When the output power is less than P limit1 and greater than P limit2 When the inverter is in medium load condition, its primary peak current reference curve is as follows: Figure 2 As shown in the middle curve. When the output power is less than P limit2 When the inverter is in light load condition, its primary peak current reference curve is as follows: Figure 2 As shown in the lower graph.

[0032] Understandable, P. limit1 and P limit2 The specific value of can be set by those skilled in the art according to specific application scenarios and is not limited in the present disclosure.

[0033] Now turn to Figure 3 , Figure 3 A schematic diagram 300 is shown showing the corresponding relationship between the primary peak current reference and the main switching frequency of a conventional micro inverter. Figure 3 The curves (a) and (c) on the left represent the inverter under medium load conditions; and Figure 3 The curves (b) and (d) on the right represent the inverter under light load conditions. Specifically, Figure 3 The curve diagram (a) in FIG. 1 represents the primary peak current reference curve of the inverter under medium load conditions, and the curve diagram (c) represents the curve change of the main switch frequency corresponding to the current reference in the curve diagram (a). Figure 3The curve (b) in FIG. 1 shows the primary peak current reference curve of the inverter under light load conditions, and the curve (d) shows the curve change of the main switch frequency corresponding to the current reference in the curve (b). Figure 3 It can be seen from the curves (c) and (d) that when the traditional micro inverter operates in DCM mode under low power conditions, its switching frequency is constant.

[0034] The inventors found that when the micro-inverter is operating in DCM mode under low power conditions, the power of the micro-inverter can be reduced by changing the DCM frequency at regular intervals, thereby reducing switching losses and improving product efficiency. Therefore, the inventors proposed an interleaved flyback inverter that implements a low-power optimization control strategy. Figure 4-Figure 7 A further detailed description is given.

[0035] Figure 4 An exemplary low power optimization control strategy block diagram 400 of the interleaved flyback inverter 100 according to one or more embodiments of the present disclosure is shown. In some embodiments of the present disclosure, the low power optimization control loop 400 may include an MPPT (Maximum Power Point Tracking) module 410, a PI (Proportional Integral) controller 420, and a control unit 430. The control unit 430 may further include a low power optimization module 4310 and a BCM and DCM hybrid control module 4320.

[0036] The MPPT module 410, the PI controller 420, and the control unit 430 may include hardware, software, and / or firmware implementations. In some embodiments, the MPPT module 410, the PI controller 420, and the control unit 430 may include, for example, a central control chip. In some embodiments, the MPPT module 410, the PI controller 420, and the control unit 430 may include program codes that may implement corresponding operations when executed. In some embodiments, the MPPT module 410, the PI controller 420, and the control unit 430 may be implemented in the front-stage circuit structure 110 of the interleaved flyback inverter 100. In some embodiments, the MPPT module 410, the PI controller 420, and the control unit 430 may be implemented outside the interleaved flyback inverter 100 or its front-stage circuit structure 110. In some embodiments, the MPPT module 410, the PI controller 420, and the control unit 430 may be partially implemented in the front-stage circuit structure 110 of the interleaved flyback inverter 100, and partially implemented outside the interleaved flyback inverter 100 or its front-stage circuit structure 110.

[0037] exist Figure 4 In the embodiment shown, the MPPT module 410 can receive the current I output by the photovoltaic module PV pv and voltage U pv , and generate the reference voltage U through calculation ref For sending to the comparator. The comparator can be further combined with U pv To generate a comparison result and send the comparison result to the PI controller 420. The PI controller 420 can thereby generate a PI output current I m * and sends it to the control unit 430. The control unit 430 can further combine the phase lock flag |sin(ωt)| from the phase lock loop to perform BCM / DCM control (for example, through PWM (Pulse Width Modulation)) and output the reference current I ref .

[0038] Reference now Figure 7 , Figure 7 A schematic flow chart of a low power optimization method 700 of an interleaved flyback inverter 100 according to one or more embodiments of the present disclosure is shown to implement DCM frequency conversion control when the inverter 100 is in a DCM mode under low power conditions. The method 700 may include, when the inverter 100 is in a low power condition and in a DCM mode: shutting down the second flyback circuit in the front-stage circuit structure 110 of the inverter 100 and enabling the low power optimization module 4310 of the control unit 430 of the inverter 100 (step 710); determining, by the low power optimization module 4310, the switch S of the first flyback circuit in the front-stage circuit structure 110 of the inverter 100 1 DCM duty cycle DCM and DCM period Prd DCM (Step 720); The low power optimization module 4310 uses the determined DCM duty cycle Duty DCM and DCM period Prd DCM The control unit 430 of the inverter 100 updates the register comparison value and register period for frequency conversion control respectively (step 730); and the low power optimization module 4310 enables the first flyback circuit in the front-stage circuit structure 110 of the inverter 100 based on the updated register comparison value and register period (step 740).

[0039] In some embodiments, the registered comparison value may be stored in, for example, a cmp register of an EPWM chip, and the registered period may be stored in, for example, a period register of the EPWM chip.

[0040] When executing step 720, the low power optimization module 4310 may be configured to first determine the switch S of the first flyback circuit in the front-stage circuit structure 110 of the inverter 100. 1 The current switching frequency Fs DCM (DCM mode). In some embodiments, the DCM switching frequency Fs can be calculated according to the following formula (1): DCM : F DCM =α+β*sin(ωt) (1) Among them, Fs DCM represents the switching frequency of the interleaved flyback inverter when it is operating in DCM mode under low power conditions, sin(ωt) represents the grid phase output by the phase-locked loop, and α and β are constants. In an embodiment, α and β can be based on one or more of the following parameters: maximum switching frequency limit, minimum switching frequency limit, inverter conversion efficiency, and similar parameters. In one example, α can be 10000, and β can be 70000.

[0041] Then, the low power optimization module 4310 can be configured to adjust the DCM switching frequency Fs based on the determined DCM switching frequency Fs. DCM To calculate the DCM reference current I output by the control unit 430 ref_DCM In some embodiments, the DCM reference current I can be calculated according to the following formula (2): ref_DCM : Among them, I ref_DCM It indicates the reference current currently output by the control unit when the interleaved flyback inverter is operating in DCM mode under low power conditions, I ac Indicates the AC grid current after conversion from the reference current currently output by the MPPT module, V ac Indicates the AC grid voltage, Fs DCM Indicates the switching frequency of the inverter, L p represents the inductance of the transformer, and sin(ωt) represents the grid phase output by the phase-locked loop.

[0042] Next, the low power optimization module 4310 can be configured to calculate the DCM reference current I ref_DCM To calculate the switch S of the first flyback circuit in the front-stage circuit structure 110 of the inverter 100 1 DCM opening time T on_DCM In some embodiments, the DCM opening time T can be calculated according to the following formula (3): on_DCM : Among them, T on_DCM Indicates that the interleaved flyback inverter is in DCM mode under low power conditions. 1 The opening time, L p Indicates the inductance of the transformer, I ref_DCM Indicates the reference current currently output by the control unit, and V pv Indicates the input voltage of the photovoltaic module PV.

[0043] Next, the low power optimization module 4310 can be configured to calculate the DCM on-time T based on the calculated DCM on-time T on_DCM To calculate the switch S of the first flyback circuit in the front-stage circuit structure 110 of the inverter 100 1 DCM duty cycle DCM In some embodiments, the DCM duty cycle Duty can be calculated according to the following formula (4): DCM : Duty DCM = time_scale * T on_DCM (4) Among them, Duty DCM Indicates that the interleaved flyback inverter is in DCM mode under low power conditions. 1 The duty cycle, T on_DCM Indicates switch S 1 The on-time of the pulse width modulation is represented by time_scale. In one example, the specific value of time_scale may be 50000000.

[0044] In addition, during the calculation process of step 720, the low power optimization module 4310 may also be configured to calculate the DCM switching frequency Fs based on the determined DCM switching frequency Fs. DCM To calculate the switch S of the first flyback circuit in the front-stage circuit structure 110 of the inverter 100 1 DCM cycle Prd DCM In some embodiments, the DCM period Prd can be calculated according to the following formula (5): DCM : Among them, Prd DCM Indicates that the interleaved flyback inverter is in DCM mode under low power conditions. 1 The period, Fs DCM represents the current switching frequency of the inverter, and time_scale represents the time scale of the pulse width modulation. In an example, the specific value of time_scale can be 50000000.

[0045] Thus, the execution of step 720 obtains the DCM duty cycle Duty required for the subsequent execution of step 730. DCM and DCM period Prd DCM .

[0046] Although the steps and sub-steps of the low-power optimization method of the present invention are described in the above order, the execution of the steps and sub-steps of the low-power optimization method of the present invention should not be limited to the above order. On the contrary, some steps or sub-steps of the low-power optimization method of the present invention can be executed in an order different from the above order or simultaneously. In some alternative embodiments, certain steps or sub-steps may not be executed. In addition, any step or sub-step of the low-power optimization method of the present invention can be executed with a module, a unit, a circuit or any other suitable technical means for executing these steps or sub-steps.

[0047] By implementing a low power optimization method in an interleaved flyback inverter (e.g. Figure 7 The method 700 shown in FIG. 7 can realize DCM frequency conversion control when the inverter is in DCM mode operation under low power conditions, such as Figure 6 shown. Figure 6 and Figure 3 Similar. Compared to Figure 3 For the conventional microinverter shown in the graphs (a)-(d), Figure 6 The differences between the graphs (a)-(d) of the inverter implemented according to the embodiment of the present invention are: Figure 6 The switching frequency of the main switch operating in DCM mode in the curves (c) and (d) is also distributed in a curve, which indicates that DCM variable frequency control is achieved.

[0048] Next reference Figure 8 The overall control strategy 800 of the interleaved flyback inverter 100 is described, including the above reference Figure 7 A low power optimized control strategy is described.

[0049] The control strategy 800 begins by determining whether the inverter control is enabled (box 810). If it is determined that the inverter control is not yet enabled ("no" branch), the phase-lock flag may be set and the BCM / DCM control may be disabled (box 820), and then the control strategy 800 may end. If it is determined in box 810 that the inverter control is enabled ("yes" branch), it may be further determined whether the AC phase is near the zero crossing point (box 830). In some embodiments, the reference to "AC phase is near the zero crossing point" may refer to the result calculated by the phase-locked loop being within plus or minus 2 degrees.

[0050] If it is determined in box 830 that the AC phase is near the zero crossing point ("yes" branch), the BCM / DCM control can be disabled, the phase lock flag is set, and the MPPT loop control is performed (box 840), and then the control strategy 800 can end. If it is determined in box 830 that the AC phase is not near the zero crossing point ("no" branch), for example, the calculation result of the phase-locked loop is greater than 2 degrees, it can be further determined whether the zero crossing phase lock flag is set (box 850).

[0051] It will be appreciated that in embodiments where BCM / DCM control is enabled, the BCM / DCM control may be performed via PWM, for example.

[0052] If it is determined in box 850 that the zero-crossing phase-locked flag is not set ("No" branch), the control strategy 800 can end. If it is determined in box 850 that the zero-crossing phase-locked flag is set ("Yes" branch), the BCM switching frequency Fs of the interleaved flyback inverter 100 in the BCM mode can be further determined. BCM (Block 860). Next, the determined BCM switching frequency Fs may be determined. BCM Is it greater than the predetermined frequency threshold f limit (Block 870). In some embodiments, the predetermined frequency threshold f limit It can be determined based on product efficiency and total harmonic content THD (Total Harmonic Distortion) of current. In one example, the predetermined frequency threshold f limit It can be 350kHz.

[0053] If the BCM switching frequency Fs is determined in block 870 BCM Less than or equal to the predetermined frequency threshold f limit (“No” branch), it can be determined that the inverter 100 is not in a low-power condition. When the inverter 100 is not in a low-power condition, the BCM and DCM hybrid control module 4320 of the control unit 430 of the inverter 100 can limit the BCM duty cycle Duty in the BCM mode. BCM (Block 880), and update the register comparison value and the register period and enable the second flyback circuit in the front stage circuit structure 110 of the inverter 100 based on the updated register comparison value and the register period (Block 890). BCM Greater than a predetermined frequency threshold f limit (“Yes” branch), it can be determined that the inverter 100 is in a low power condition and its low power optimization module 4310 is enabled, and further execution can be performed Figure 7 The low power optimization method shown (such as Figure 8 as shown in point A in the figure).

[0054] After the low power optimization module 4310 or the BCM and DCM hybrid control module 4320 completes the control task, the control strategy 800 may flow to the end.

[0055] Figure 5 Conceptually shows Figure 8 The implementation of the blocks 860, 870 and their two branches. Figure 5 As shown, a switching device K1 may be provided between the low power optimization module 4310 and the BCM and DCM hybrid control module 4320. When the condition of "determined BCM switching frequency>predetermined frequency threshold" in block 870 is met (e.g., Figure 5 Fs shown in BCM >350kHz), the switching device K1 can connect the low power optimization module 4310 to the BCM and DCM hybrid control module 4320 to enable the function of the low power optimization module 4310. When this condition is not met, the switching device K1 can disconnect the connection between the low power optimization module 4310 and the BCM and DCM hybrid control module 4320 or keep it disconnected to use the function of the BCM and DCM hybrid control module 4320.

[0056] In control strategy 800, the BCM switching frequency Fs is used BCM In the control stage, the BCM switching frequency Fs of the inverter 100 in the BCM mode can be determined in block 860 by the example process described below: BCM :

[0057] First, the BCM reference current I currently output by the control unit 430 of the inverter 100 can be determined. ref_BCM In some embodiments, the BCM reference current I can be calculated according to the following formula (6): ref_BCM : Among them, I ref_BCM It represents the reference current output by the control unit when the interleaved flyback inverter operates in BCM mode, I ac Indicates the AC grid current after the reference current currently output by the MPPT module is converted, V ac represents the AC grid voltage, sin(ωt) represents the grid phase output by the phase-locked loop, V pv Represents the input voltage of the photovoltaic module PV, and N sp Represents the turns ratio of the transformer.

[0058] Alternatively, since the output power P o =I ac *V acTherefore, the above formula (6) can be transformed into the following formula (7), which can also be used to calculate the BCM reference current I ref_BCM : Among them, I ref_BCM It represents the reference current output by the control unit when the interleaved flyback inverter operates in BCM mode, P o represents the power output to the grid, sin(ωt) represents the grid phase output by the phase-locked loop, V pv Indicates the input voltage of the photovoltaic module PV, N sp represents the turns ratio of the transformer, and V ac Indicates the AC grid voltage.

[0059] Then, the BCM reference current I ref_BCM To calculate the BCM switch on time T of the inverter 100 on_BCM and BCM switch off time T off_BCM In some embodiments, the BCM switch on time T can be calculated according to the following equations (8) and (9): on_BCM and BCM switch off time T off_BCM : Among them, T on_BCM represents the switch on time of the interleaved flyback inverter when operating in BCM mode, L p Indicates the inductance of the transformer, I ref_BCM Indicates the reference current currently output by the control unit, and V pv Represents the input voltage of the photovoltaic module PV. Among them, T off_BCM represents the switch off time of the interleaved flyback inverter when operating in BCM mode, N sp Indicates the turns ratio of the transformer, L p Indicates the inductance of the transformer, I ref_BCM Indicates the reference current currently output by the control unit, V ac represents the AC grid voltage, and sin(ωt) represents the grid phase output by the phase-locked loop.

[0060] Then, based on the calculated BCM switch on time T on_BCM and BCM switch off time T off_BCM To calculate the BCM switching period Prd of the inverter 100 BCM In some embodiments, the BCM period Prd can be calculated according to the following formula (10): BCM : Prd BCM = time_scale*(Ton_BCM +T off_BCM ) (10) Among them, Prd BCM represents the switching period of the interleaved flyback inverter when operating in BCM mode, T on_BCM and T off_BCM They respectively represent the switch on time and the switch off time when the inverter operates in the BCM mode, and time_scale represents the time scale of the pulse width modulation. In an example, the specific value of time_scale can be 50000000.

[0061] Next, based on the calculated BCM switching period Prd BCM To calculate the BCM switching frequency Fs of the inverter 100 in the BCM mode BCM In some embodiments, the BCM switching frequency Fs can be calculated according to the following formula (11): BCM : Among them, Fs BCM Indicates the current switching frequency of the interleaved flyback inverter when it is operating in BCM mode, Prd BCM represents the switching period of the interleaved flyback inverter when operating in the BCM mode, and time_scale represents the time scale of the pulse width modulation. In an example, the specific value of time_scale may be 50000000.

[0062] In an alternative embodiment, instead of controlling according to the switching frequency, the control strategy 800 can control according to the output power. In an embodiment, equations (7)-(11) can be combined to obtain the following equation (12): Among them, P o_BCM Fs represents the power output of the interleaved flyback inverter when operating in BCM mode. BCM Indicates the switching frequency of the inverter when it operates in BCM mode, L p Indicates the inductance of the transformer, N sp Represents the turns ratio of the transformer, V ac represents the AC grid voltage, sin(ωt) represents the grid phase output by the phase-locked loop, and V pv Indicates the input voltage of the photovoltaic module PV.

[0063] In the embodiment, according to formula (12), based on the predetermined frequency threshold f for judging whether the inverter 100 is in a low power condition, limit Further calculation of similar predetermined power threshold P limit The predetermined power threshold Plimit It can also be used to determine whether the inverter 100 is in a low-power condition. As shown in the following formula (13):

[0064] As described above, according to the predetermined frequency threshold f limit Compared with the embodiment of making judgment, according to the predetermined power threshold P limit The steps of the alternative embodiment for making the determination are substantially the same, except that in block 870 the determined BCM output power P is determined. o_BCM Is it less than or equal to the predetermined power threshold P? limit .

[0065] In practice, the inventors tested the efficiency of the interleaved flyback inverter with low power optimization of the present invention at 50w and 90w respectively. The test results show that at low power of 50w and 90w, the control strategy of the present invention improves the efficiency of the inverter by about 3%, and the weighted average efficiency can reach about 94% or more.

[0066] According to an embodiment of the present disclosure, a computer-readable medium may be further provided, on which instructions are stored, and when the instructions are executed by a processor, the steps of the interleaved flyback inverter low-power optimization method of the present disclosure are implemented. The computer-readable medium may include, but is not limited to, a non-transient tangible arrangement of items manufactured or formed by a machine or device, including storage media, such as: a hard disk; any other type of disk, including a floppy disk, an optical disk, a read-only compact disk memory (CD-ROM), a read-write compact disk memory (CD-RW), and a magneto-optical disk; semiconductor devices, such as read-only memory (ROM), random access memory (RAM) such as dynamic random access memory (DRAM) and static random access memory (SRAM), erasable programmable read-only memory (EPROM), flash memory, electrically erasable programmable read-only memory (EEPROM); phase change memory (PCM); a magnetic card or an optical card; or any other type of medium suitable for storing electronic instructions. The computer-readable medium may be installed in an imaging device, or in a separate control device or computer that remotely controls the imaging device.

[0067] According to an embodiment of the present disclosure, a computer program product may be further provided. The computer program product includes instructions. When the instructions are executed by a processor, the steps of the interleaved flyback inverter low-power optimization method of the present disclosure are implemented.

[0068] The following provides a number of exemplary embodiments of the present disclosure. Various details in the examples can be used in one or more embodiments of the present disclosure, and can be appropriately combined with each other to form a unique embodiment.

[0069] Example 1 is an interleaved flyback inverter. The interleaved flyback inverter may include a front-stage circuit structure and a rear-stage circuit structure, wherein the front-stage circuit structure is connected to a photovoltaic module and is used to output a DC signal to the rear-stage circuit structure, and the rear-stage circuit structure is used to convert the DC signal into an AC signal, wherein the front-stage circuit structure includes a first flyback circuit and a second flyback circuit connected in parallel, and the first flyback circuit includes a switch S 1 The interleaved flyback inverter may further include a control unit, wherein the control unit includes a low-power optimization module. When the interleaved flyback inverter is in a low-power operating condition, the second flyback circuit in the front-stage circuit structure may be turned off in DCM mode and the low-power optimization module may be enabled, and the low-power optimization module may be configured to: determine the switch S of the first flyback circuit in the front-stage circuit structure. 1 The invention relates to a method for realizing a control system for controlling a frequency conversion control of a first flyback circuit in a first stage circuit structure and a control system for controlling a frequency conversion control of a first flyback circuit in a first stage circuit structure. The method comprises: determining a DCM duty cycle and a DCM cycle; updating a register comparison value and a register period of the control unit for frequency conversion control using the determined DCM duty cycle and the DCM period; and enabling the first flyback circuit in the first stage circuit structure based on the updated register comparison value and the register period.

[0070] Example 2 includes the interleaved flyback inverter according to Example 1, wherein the determination of the DCM duty cycle may further include: when the interleaved flyback inverter is in a low power condition, the low power optimization module in the DCM mode is configured to: determine the switch S of the first flyback circuit in the front stage circuit structure; 1 The DCM switching frequency is determined; based on the determined DCM switching frequency, the DCM reference current output by the control unit is calculated; based on the calculated DCM reference current, the switch S is calculated. 1 and calculating the DCM duty cycle based on the calculated DCM on time.

[0071] Example 3 includes the interleaved flyback inverter according to Example 1 or 2, wherein the determination of the DCM period may further include when the interleaved flyback inverter is in a low power condition, the low power optimization module in the DCM mode is configured to: determine the switch S of the first flyback circuit in the front stage circuit structure; 1 and calculating the DCM period based on the determined DCM switching frequency.

[0072] Example 4 includes the interleaved flyback inverter according to any one of Examples 1-3, wherein the control unit may further include a BCM and DCM hybrid control module.

[0073] Example 5 includes the interleaved flyback inverter of Example 4, wherein the BCM and DCM hybrid control module may be configured to determine a BCM switching frequency of the interleaved flyback inverter in a BCM mode.

[0074] Example 6 includes the interleaved flyback inverter according to Example 4 or 5, wherein the control unit can be configured to determine that the interleaved flyback inverter is in the low power operating condition when the determined BCM switching frequency is greater than a predetermined frequency threshold.

[0075] Example 7 includes the interleaved flyback inverter according to any one of Examples 4-6, wherein the control unit can be configured to determine that the interleaved flyback inverter is not in the low-power operating condition when the determined BCM switching frequency is less than or equal to a predetermined frequency threshold.

[0076] Example 8 includes an interleaved flyback inverter according to any one of Examples 4-7, wherein the determination of the BCM switching frequency may further include the BCM and DCM hybrid control module being configured to, in the BCM mode: determine a BCM reference current output by the control unit; calculate a BCM switch on time and a BCM switch off time of the interleaved flyback inverter based on the determined BCM reference current; calculate a BCM switching cycle of the interleaved flyback inverter based on the calculated BCM switch on time and BCM switch off time; and calculate the BCM switching frequency based on the calculated BCM switching cycle.

[0077] Example 9 includes the interleaved flyback inverter of Example 4, wherein the BCM and DCM hybrid control module may be configured to determine a BCM output power of the interleaved flyback inverter in a BCM mode.

[0078] Example 10 includes the interleaved flyback inverter according to Example 4 or 9, wherein the control unit can be configured to determine that the interleaved flyback inverter is in the low-power operating condition when the determined BCM output power is less than or equal to a predetermined power threshold.

[0079] Example 11 includes the interleaved flyback inverter according to Example 4, 9 or 10, wherein the control unit can be configured to determine that the interleaved flyback inverter is not in the low power operating condition when the determined BCM output power is greater than a predetermined power threshold.

[0080] Example 12 includes the interleaved flyback inverter according to any one of Examples 1-11, wherein the first flyback circuit and the second flyback circuit have the same structure.

[0081] Example 13 includes the interleaved flyback inverter according to any one of Examples 1-12, wherein the subsequent circuit structure may be an H-bridge circuit.

[0082] Example 14 is a photovoltaic device. The photovoltaic device may include the interleaved flyback inverter according to any one of Examples 1-13 or may be connected to the interleaved flyback inverter according to any one of Examples 1-13.

[0083] Example 15 is a low-power optimization method for an interleaved flyback inverter. The interleaved flyback inverter may include a front-stage circuit structure and a rear-stage circuit structure, wherein the front-stage circuit structure is connected to a photovoltaic module and is used to output a DC signal to the rear-stage circuit structure, and the rear-stage circuit structure is used to convert the DC signal into an AC signal, wherein the front-stage circuit structure includes a first flyback circuit and a second flyback circuit connected in parallel, and the first flyback circuit includes a switch S 1 The low-power optimization method may include, when the interleaved flyback inverter is in a low-power operating condition, in a DCM mode: shutting down the second flyback circuit in the front-stage circuit structure and enabling a low-power optimization module of a control unit of the interleaved flyback inverter; determining, by the low-power optimization module, the switch S of the first flyback circuit in the front-stage circuit structure. 1 The low-power optimization module uses the determined DCM duty cycle and DCM cycle to respectively update the register comparison value and register cycle used by the control unit for variable frequency control; and the low-power optimization module enables the first flyback circuit in the previous stage circuit structure based on the updated register comparison value and register cycle.

[0084] Example 16 includes the low power optimization method according to Example 15, wherein determining the switch S of the first flyback circuit in the previous stage circuit structure 1 The DCM duty cycle may include when the interleaved flyback inverter is in a low-power condition, in the DCM mode, the low-power optimization module: determining the switch S of the first flyback circuit in the front-stage circuit structure 1 The DCM switching frequency is determined; based on the determined DCM switching frequency, the DCM reference current output by the control unit is calculated; based on the calculated DCM reference current, the switch S is calculated. 1 and calculating the DCM duty cycle based on the calculated DCM on time.

[0085] Example 17 includes the low power optimization method according to Example 15 or 16, wherein determining the switch S of the first flyback circuit in the previous stage circuit structure 1The DCM cycle may include when the interleaved flyback inverter is in a low-power condition, in the DCM mode, the low-power optimization module: determining the switch S of the first flyback circuit in the front-stage circuit structure 1 and calculating the DCM period based on the determined DCM switching frequency.

[0086] Example 18 includes the low power optimization method according to any one of Examples 15-17, wherein the control unit may further include a BCM and DCM hybrid control module.

[0087] Example 19 includes the low power optimization method according to Example 18, wherein the low power optimization method may further include determining, by the BCM and DCM hybrid control module, a BCM switching frequency of the interleaved flyback inverter in a BCM mode.

[0088] Example 20 includes the low power optimization method according to Example 18 or 19, wherein the control unit can determine that the interleaved flyback inverter is in the low power operating condition when the determined BCM switching frequency is greater than a predetermined frequency threshold.

[0089] Example 21 includes a low power optimization method according to any one of Examples 18-20, wherein the control unit can determine that the interleaved flyback inverter is not in the low power operating condition when the determined BCM switching frequency is less than or equal to a predetermined frequency threshold.

[0090] Example 22 includes a low-power optimization method according to any one of Examples 18-21, wherein determining the BCM switching frequency of the interleaved flyback inverter in the BCM mode may include, by the BCM and DCM hybrid control module in the BCM mode: determining a BCM reference current output by the control unit; calculating a BCM switch on time and a BCM switch off time of the interleaved flyback inverter based on the determined BCM reference current; calculating a BCM switching cycle of the interleaved flyback inverter based on the calculated BCM switch on time and BCM switch off time; and calculating the BCM switching frequency based on the calculated BCM switching cycle.

[0091] Example 23 includes the low power optimization method according to Example 18, wherein the low power optimization method may further include determining, by the BCM and DCM hybrid control module, a BCM output power of the interleaved flyback inverter in a BCM mode.

[0092] Example 24 includes a low power optimization method according to Example 18 or 23, wherein the control unit can determine that the interleaved flyback inverter is in the low power operating condition when the determined BCM output power is less than or equal to a predetermined power threshold.

[0093] Example 25 includes a low power optimization method according to Example 18, 23 or 24, wherein the control unit can determine that the interleaved flyback inverter is not in the low power operating condition when the determined BCM output power is greater than a predetermined power threshold.

[0094] Example 26 includes the low power optimization method according to any one of Examples 15-25, wherein the first flyback circuit and the second flyback circuit have the same structure.

[0095] Example 27 includes the low power optimization method according to any one of Examples 15-26, wherein the subsequent circuit structure may be an H-bridge circuit.

[0096] Example 28 is a computer-readable storage medium. The computer-readable storage medium may store instructions, and when the instructions are executed by a processor, the steps of the low-power optimization method described in any one of Examples 15-27 may be implemented.

[0097] Example 29 is a computer program product. The computer program product may include instructions, and when the instructions are executed by a processor, the steps of the low power optimization method described in any one of Examples 15-27 may be implemented.

[0098] It should be noted that in order to simplify the description of this application and thus facilitate the understanding of one or more embodiments, in the foregoing description of the embodiments, multiple features are sometimes grouped into one embodiment, drawing, or description thereof. However, this description method does not mean that the subject matter of this application requires more features than those mentioned in the claims. In fact, the features of an embodiment may be less than all the features of a single embodiment disclosed above.

[0099] Although the present disclosure is described with reference to the above specific embodiments, it should be understood by those skilled in the art that the above embodiments are only illustrative and not restrictive. Those skilled in the art may make various equivalent changes, modifications or substitutions without departing from the spirit and scope of the present disclosure, and therefore these changes, modifications and substitutions all fall within the scope of protection of the claims of the present disclosure.

Claims

1. An interleaved flyback inverter, characterized in that: include: A front-stage circuit structure and a rear-stage circuit structure, wherein the front-stage circuit structure is connected to the photovoltaic module and is used to output a direct current signal to the rear-stage circuit structure, and the rear-stage circuit structure is used to convert the direct current signal into an alternating current signal, wherein the front-stage circuit structure includes a first flyback circuit and a second flyback circuit connected in parallel, and the first flyback circuit includes a switch S1; as well as a control unit, the control unit comprising a low power optimization module, Wherein, when the interleaved flyback inverter is in a low-power operating condition, the second flyback circuit in the front-stage circuit structure is turned off in a DCM mode and the low-power optimization module is enabled, and the low-power optimization module is configured to: Determining a DCM duty ratio and a DCM period of the switch S1 of the first flyback circuit in the previous stage circuit structure; Using the determined DCM duty cycle and DCM period, respectively updating the register comparison value and register period used by the control unit for variable frequency control; as well as The first flyback circuit in the previous stage circuit structure is enabled based on the updated register comparison value and the register period.

2. The interleaved flyback inverter according to claim 1, characterized in that: The determination of the DCM duty cycle further includes that when the interleaved flyback inverter is in a low power condition, the low power optimization module in the DCM mode is configured to: Determining a DCM switching frequency of the switch S1 of the first flyback circuit in the previous stage circuit structure; Calculating a DCM reference current output by the control unit based on the determined DCM switching frequency; Calculating the DCM on-time of the switch S1 based on the calculated DCM reference current; as well as The DCM duty cycle is calculated based on the calculated DCM on time.

3. The interleaved flyback inverter according to claim 1, characterized in that: The determination of the DCM period further includes that when the interleaved flyback inverter is in a low power condition, the low power optimization module is configured to: Determining a DCM switching frequency of the switch S1 of the first flyback circuit in the previous stage circuit structure; and The DCM period is calculated based on the determined DCM switching frequency.

4. The interleaved flyback inverter according to claim 1, characterized in that: The control unit further includes a BCM and DCM hybrid control module, and the BCM and DCM hybrid control module is configured to determine a BCM switching frequency of the interleaved flyback inverter in a BCM mode.

5. The interleaved flyback inverter according to claim 4, characterized in that: The control unit is configured to determine that the interleaved flyback inverter is in the low-power operating condition when the determined BCM switching frequency is greater than a predetermined frequency threshold.

6. The interleaved flyback inverter according to claim 4, characterized in that: The control unit is configured to determine that the interleaved flyback inverter is not in the low-power operating condition when the determined BCM switching frequency is less than or equal to a predetermined frequency threshold.

7. The interleaved flyback inverter according to claim 4, characterized in that: The determination of the BCM switching frequency further includes the BCM and DCM hybrid control module being configured to: Determining a BCM reference current output by the control unit; Calculating a BCM switch on time and a BCM switch off time of the interleaved flyback inverter based on the determined BCM reference current; Calculating a BCM switching period of the interleaved flyback inverter based on the calculated BCM switch on time and BCM switch off time; as well as The BCM switching frequency is calculated based on the calculated BCM switching period.

8. The interleaved flyback inverter according to claim 1, characterized in that: The first flyback circuit and the second flyback circuit have the same structure.

9. A photovoltaic device, characterized in that: The invention comprises an interleaved flyback inverter according to any one of claims 1 to 8 or is connected to an interleaved flyback inverter according to any one of claims 1 to 8.

10. A low power optimization method for an interleaved flyback inverter, characterized in that: The interleaved flyback inverter comprises a front-stage circuit structure and a rear-stage circuit structure, wherein the front-stage circuit structure is connected to the photovoltaic module and is used to output a direct current signal to the rear-stage circuit structure, and the rear-stage circuit structure is used to convert the direct current signal into an alternating current signal, wherein the front-stage circuit structure comprises a first flyback circuit and a second flyback circuit connected in parallel, wherein the first flyback circuit comprises a switch S1, and the low-power optimization method comprises: when the interleaved flyback inverter is in a low-power operating condition, in a DCM mode: Turning off the second flyback circuit in the front-stage circuit structure and enabling a low-power optimization module of a control unit of the interleaved flyback inverter; The low-power optimization module determines the DCM duty ratio and DCM period of the switch S1 of the first flyback circuit in the front-stage circuit structure; The low power optimization module uses the determined DCM duty cycle and DCM period to update the register comparison value and register period used by the control unit for variable frequency control respectively; as well as The low power optimization module enables the first flyback circuit in the previous stage circuit structure based on the updated register comparison value and register period.

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