Method, apparatus and computer device for grid-connected control of a flyback converter

Abstract

This application relates to a method, apparatus, and computer device for controlling grid connection of a flyback converter. The method includes: obtaining grid connection parameters of the flyback converter and upper and lower frequency limits of a power switch in the flyback converter; determining a number of resonant valleys of the power switch based on the grid connection parameters and the upper and lower frequency limits; obtaining a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; and controlling the power switch based on the switching frequency. Application of this method improves safety.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to a Chinese patent application bearing application number 2024101100072 and entitled "Method, apparatus and computer device for controlling grid connection of flyback converter," filed with the State Intellectual Property Office of the People's Republic of China on January 26, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of electric circuits, and more particularly to a method, apparatus and computer device for grid-connected control of a flyback converter. [Background technology]

[0003] Flyback converters are widely used due to their features such as electrical isolation at high frequencies, simple structure, and low cost. Flyback converters include boundary conduction mode (BCM) and discontinuous conduction mode (DCM).

[0004] When a flyback converter operates in BCM, the switching frequency of the power switch is very high during light loads, such as when the grid voltage is at the zero crossing point, resulting in very large switching losses. On the other hand, when a flyback converter operates in DCM with a fixed switching frequency, the current stress on the power switch becomes very large during heavy loads, such as when the grid voltage reaches its peak value. Therefore, the current switching frequency control method has a problem of insufficient safety. Summary of the Invention [Problem to be solved by the invention]

[0005] Based on this, in order to address the above technical problems, there is a need to provide a grid-connected control method, apparatus and computer device for a flyback converter that improves safety. [Means for solving the problem]

[0006] In a first aspect, the present application provides a grid-connected control method for a flyback converter, the grid-connected control method for a flyback converter comprising: Obtaining grid connection parameters of the flyback converter, upper and lower frequency limits of the power switch in the flyback converter; Identifying a number of resonant valleys of the power switch based on the grid connection parameters, an upper frequency limit, and a lower frequency limit; obtaining a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; and controlling the power switch based on the switching frequency.

[0007] In a second aspect, the present application further provides a grid-connected control device for a flyback converter, the grid-connected control device for a flyback converter comprising: a first acquisition module used to acquire grid connection parameters of the flyback converter, an upper frequency limit and a lower frequency limit of a power switch in the flyback converter; a first identification module used to identify the number of resonant valleys of the power switch based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; a second identification module used to obtain a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; and a control module used to control the power switch based on the switching frequency.

[0008] In a third aspect, the present application further provides a computer device including a memory and a processor, wherein a computer program is stored in the memory, and the steps of any of the above methods are performed when the processor executes the computer program.

[0009] In a fourth aspect, the present application further provides a computer-readable recording medium storing a computer program, which, when executed by a processor, performs the steps of any of the above methods.

[0010] In a fifth aspect, the present application further provides a computer program product including a computer program that, when executed by a processor, performs the steps of any of the above methods. [Effects of the Invention]

[0011] The above-mentioned method, apparatus, and computer device for controlling grid connection of a flyback converter obtain grid connection parameters of the flyback converter and upper and lower frequency limits of the power switches in the flyback converter, and determine the number of resonant valleys of the power switches based on the grid connection parameters and the upper and lower frequency limits. The switching frequency of the power switches is then determined based on the grid connection parameters and the number of resonant valleys, and the power switches can be controlled based on the switching frequency. Furthermore, since the number of resonant valleys is determined based on the upper and lower frequency limits, the determined switching frequency can be greater than or equal to the lower switching frequency limit and less than or equal to the upper switching frequency limit, thereby solving the problem of excessively high switching losses in the prior art due to excessively high switching frequencies. Furthermore, the flyback converter can operate at a variable switching frequency, which prevents large current stress and improves safety.

[0012] In order to more clearly explain the embodiments of the present invention or the technical solutions of the prior art, the drawings necessary for describing the embodiments or the prior art will be briefly described. The drawings described below are only the embodiments of the present invention, and it is clear that those skilled in the art can obtain drawings of other embodiments based on these drawings without any creative efforts. [Brief explanation of the drawings]

[0013] [Figure 1] This is a topology configuration of a two-stage flyback converter. [Figure 2] FIG. 1 is a schematic diagram of boundary conduction mode. [Figure 3] FIG. 1 is a schematic diagram of a discontinuous conduction mode. [Figure 4] FIG. 1 is a diagram illustrating an application environment of a grid connection control method for a flyback converter according to an embodiment of the present application. [Figure 5] FIG. 1 is a flowchart illustrating a grid-connected control method for a flyback converter according to an embodiment of the present application. [Figure 6] FIG. 10 is a flowchart illustrating a process for determining a switching frequency in an embodiment of the present application. [Figure 7] FIG. 10 illustrates another flowchart for determining a switching frequency in accordance with an embodiment of the present application. [Figure 8] 1 is a schematic diagram illustrating the principle of a valley switch in an embodiment of the present application. [Figure 9] FIG. 10 shows a flowchart for determining the number of resonance valleys in an embodiment of the present application. [Figure 10] FIG. 10 is a flowchart illustrating a method for controlling a switching frequency in an embodiment of the present application. [Figure 11] 1 is a schematic diagram of a control process according to an embodiment of the present application; [Figure 12] FIG. 10 illustrates yet another flowchart for determining a switching frequency in accordance with an embodiment of the present application. [Figure 13] 1 is a schematic diagram illustrating a process of a grid-connected control method for a flyback converter according to an embodiment of the present application; FIG. [Figure 14] FIG. 10 is a diagram showing the effect of a simulation according to an embodiment of the present invention. [Figure 15] FIG. 1 is a schematic diagram illustrating power parameters according to an embodiment of the present application. [Figure 16] 1 is a configuration block diagram of a grid connection control device for a flyback converter according to an embodiment of the present application. [Figure 17] FIG. 1 is a diagram illustrating the internal configuration of a computer device according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0014] In order to clarify the purpose, technical solution and advantages of the present application, the present application will be described in detail below with reference to the accompanying drawings and examples. Note that the specific examples described in this specification are only for the purpose of interpreting the present application and are not intended to limit the present application.

[0015] Flyback converters are widely used in the field of electrical circuits because they can provide isolation between the input and output stages. Hereinafter, a two-stage flyback converter will be described as an example, and the principles of other types of flyback converters are similar, so they will not be repeated here.

[0016] 1 is a topology diagram of a two-stage flyback converter. As shown in FIG. 1, a flyback converter 100 includes a first stage structure 101 and a second stage structure 102. The first stage structure 101 includes a power supply P1, a filter capacitor C in and a flyback converter. The power source P1 may include, but is not limited to, a photovoltaic panel. The flyback converter includes a power switch S1, a transformer T1, and a diode D1.

[0017] Also, the filter capacitor C inis connected to the input end of the flyback converter, and the power switch S1 controls the energy transfer of the flyback topology to reduce second harmonic currents caused by instantaneous power imbalance between the power source and the power grid. If the power source P1 is a photovoltaic panel, the first stage structure 101 can further realize maximum power point tracking (MPPT).

[0018] The second stage structure 102 includes a bus capacitor C bus , a full-bridge inverter circuit configured with thyristors D2 to D5 and a power grid E1. Also, the output voltage of the flyback converter and the bus capacitor C bus The absolute value of the voltage of the transformer is equal to the voltage of the power grid. s The high frequency components at are filtered by the power grid inductance Lg.

[0019] Still referring to Figure 1, when the power switch S1 is turned on, the primary current i p starts to rise linearly. The primary current i p is the peak current I pp When the voltage rises to equal to L, the power switch S1 is turned off. m The supply voltage of power supply P1 is V pv Based on the inductance current equation, the conduction time T on satisfies the following formula (1).

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[0020] When the power switch S1 is turned off, the diode D1 on the secondary side of the transformer is turned on. The energy in the magnetizing inductance on the primary side is transferred to the secondary side through the transformer T1, and the secondary current i flows through the diode D1 on the secondary side. s decreases linearly, and the transformer secondary voltage reaches the power grid voltage v gridThe absolute value of the transformer turns ratio is N sp The secondary current of the diode D1 is i s The time required for T to fall to 0 f satisfies the following formula (2).

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[0021] Ideally, to reduce the total harmonic distortion, the power grid current I gird is a sinusoidal curve and has the same phase angle θ as the voltage of the power grid. grid A single switching period T of the power switch S1 sw Within the , the average value of the secondary diode current should be equal to the instantaneous value of the grid current. grid | satisfies the following formula (3).

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[0022] Furthermore, the flyback converter includes a boundary conduction mode and a discontinuous conduction mode. Figure 2 is a schematic diagram of the boundary conduction mode. As shown in Figure 2, in the boundary conduction mode, the power switch S1 controls the secondary current i s As soon as the current i drops to zero, the power switch S1 is turned on. s After it drops to 0, it is turned on again after a certain dead time has elapsed. In Figures 2 and 3, T on indicates the conduction time of the power switch S1, and T off indicates the off time of the power switch S1, and T f T f indicates the fall time of the power switch S1, and the fall time is the secondary current i s The dead time is the time required for the off time T off is equal to V GSindicates the gate-source voltage of the power switch S1. The peak current I pp and the peak current I on the secondary side of the flyback converter sp are all indicated by dashed lines.

[0023] In addition, in equations (1) and (2), the conduction time T on and descent time T f The method for determining the peak current I of the primary side is applicable to the boundary conduction mode and the discontinuous conduction mode. pp Once is specified, the conduction time T on and descent time T f can be identified.

[0024] The following explanation will be given using the critical conduction model as an example. In the critical conduction mode, the secondary current i s decreases to 0, the power switch S1 is immediately turned on, so that the off-time T off is the descent time T f The switching period T swBCM can be expressed as the following equation (4).

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[0025] By combining equations (1), (2), (3), and (4), the peak current I on the primary side in boundary conduction mode is ppBCM can be determined as shown in the following equation (5).

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[0026] Also, P ref is the reference value of the grid-connected power, i.e., the active power of the power grid, and P ref is expressed as the peak voltage V of the power grid, as shown in the following equation (6). m and the peak value of the power grid current i m It is identified by:

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[0027] By combining equations (1), (2), (4), and (5), the switching frequency f of the power switch S1 in boundary conduction mode is given by equation (7). swBCM can be identified.

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[0028] As can be seen from equation (7), when the flyback converter operates in boundary conduction mode, at light load, for example, when the grid voltage is near the zero crossing point, sin(θ grid ) is 0, the denominator in equation (7) becomes very small, the switching frequency of the power switch S1 becomes very high, and the switching loss of the power switch becomes very large.

[0029] In the following, the discontinuous conduction mode will be described as an example. In the discontinuous conduction mode, the power switch S1 controls the secondary current i s After the power switch S1 falls to 0, a certain dead time elapses and the power switch S1 is turned on again. off is the descent time T f and the resonance valley time T d is equal to T off =T f +T d In other words, the dead time is the fall time T f and the resonance valley time T d Includes:

[0030] Furthermore, in discontinuous conduction mode, the switching period T swBCM can be expressed as the following equation (8).

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[0031] The flyback converter operates at a fixed switching frequency f in discontinuous conduction mode. const When the power switch S1 operates at const is as shown in the following equation (9).

number

[0032] By combining equations (1), (2), (3), (8), and (9), the peak current I in discontinuous conduction mode at a fixed frequency is given by equation (10) below. pp can be identified.

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[0033] As can be seen from equation (10), when a flyback converter operates in discontinuous conduction mode with a fixed frequency, sin(θ grid ) is 1, so the peak current I pp is very high, the current stress on the power switch S1 may increase to unacceptable levels.

[0034] As can be seen, the conventional switching frequency control method has a problem of insufficient safety. Therefore, it is necessary to provide a switching frequency control method to address the above technical problems. The switching frequency control method will be described below.

[0035] 4 illustrates an application environment of the grid-connected control method for a flyback converter according to an embodiment of the present application. The flyback converter 100 communicates with a controller 401. The controller 401 may be, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices. The portable wearable device may be, for example, a smart watch, a smart bracelet, or a headset. The controller 401 may include, but is not limited to, at least one of a central processing unit (CPU), a digital signal processing (DSP), a field-programmable gate array (FPGA), or other programmable logic devices.

[0036] FIG. 5 is a flowchart illustrating a grid-connected control method for a flyback converter according to an embodiment of the present application. In one exemplary embodiment, a grid-connected control method for a flyback converter is provided as shown in FIG. 5, which is described as being applied to the controller in FIG. 4, and includes the following steps S501 to S503. In S501, the grid connection parameters of the flyback converter, the upper and lower frequency limits of the power switch in the flyback converter are obtained.

[0037] In this embodiment, the upper limit of the switching frequency f max and the lower limit of the switching frequency f min The upper limit of the switching frequency f may be a value that is preset and stored in the controller, may be a value that is sent to the controller by another device, or may be a value that is input by the user, and the present embodiment is not limited to these. max is used to limit the maximum switching frequency of the power switch S1, and the lower limit of the switching frequency f min is used to limit the minimum switching frequency of power switch S1.

[0038] In some embodiments, the upper switching frequency limit f max and the lower limit of the switching frequency f min is usually determined by the hardware in the flyback converter, such as power semiconductors, transformers, etc.

[0039] The grid connection parameters indicate power parameters in the flyback converter. The grid connection parameters may include corresponding power parameters in the application process of the flyback converter, such as the supply voltage V pv , transformer excitation inductance L in a flyback converter m , the peak current I of the primary side of the flyback converter pp , the phase angle θ of the power grid voltage grid It may also include the following.

[0040] Optionally, the controller may obtain grid connection parameters from the flyback converter via sensors, and may also receive grid connection parameters entered or transmitted by other devices or users.

[0041] In S502, the number of resonant valleys of the power switch is determined based on the grid connection parameters, the upper frequency limit and the lower frequency limit.

[0042] Continuing to refer to FIG. 1, when the power switch S1 is turned off and the transformer secondary current i s After decreasing to 0, the magnetizing inductance L of transformer T1 m and the parasitic capacitance C of the power switch S1 oss form a resonant energy storage circuit. The resonant stored energy is stored in the magnetizing inductance L until the next time the power switch S1 is turned on. m and parasitic capacitance C oss During this period, the drain-source voltage V of the power switch S1 is alternating betweenDS vibrates with a sinusoidal decay waveform, and the corresponding resonant period is T r is as shown in the following equation (11).

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[0043] Furthermore, the drain-source voltage V of the power switch S1 DS When decreases, the primary current i p The drain-source voltage V of the power switch S1 is negative. DS At the bottom of the valley, the primary current i p changes from a negative value to 0. Therefore, the drain-source voltage V of the power switch S1 DS When the power switch S1 is turned on at the bottom of the valley, the instantaneous current at the moment of turning on can be made zero and the voltage can be minimized, thereby minimizing the switching loss in one time. r This is the point corresponding to the minimum value of the resonant voltage at

[0044] Furthermore, the resonance period T r affects one switching period of the power switch S1, thereby changing the switching frequency f sw Therefore, in this embodiment, the controller controls the number m of resonance valleys of the power switch S1, and by adjusting the number m of resonance valleys, the switching frequency of the power switch can be controlled.

[0045] Also, for the number of resonance valleys m, there are n resonance periods T r where n is the number of resonance periods, and the relationship between n and m is n=m-1. That is, when n=0, the number of resonance valleys m=1, when n=1, the number of resonance valleys m=2, and when n=2, the number of resonance valleys m=3. It is understood that the number of resonance periods is a natural number.

[0046] Optionally, the controller can calculate the number of resonant valleys of the power switch S1 when the switching frequency of the power switch S1 is less than or equal to the upper frequency limit and greater than or equal to the lower frequency limit based on the grid connection parameters of the flyback converter.

[0047] In some embodiments, the controller may pre-calculate and store a mapping relationship between different grid connection parameters and different numbers of resonant valleys based on the grid connection parameters, an upper frequency limit, and a lower frequency limit, the mapping relationship indicating the corresponding number of resonant valleys when the switching frequency of the power switch S1 is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit when operating with the grid connection parameters. Further, the controller may use the mapping relationship to identify the number of resonant valleys of the power switch.

[0048] As an example, in one embodiment, the above-mentioned S502 can be optionally implemented in the following manner.

[0049] Based on the grid connection parameters, upper and lower frequency limits, the number of resonant valleys of the power switch at each control stage is identified.

[0050] First, the controller identifies each control step, where each control step includes a fixed time length, and each control step may be periodic or aperiodic, and the number of resonant valleys at different control steps may be different.

[0051] Optionally, the controller can identify the number of resonant valleys m in a control phase at the start time of that control phase. Illustratively, t0-t1 is control phase 1, t1-t2 is control phase 2, and t2-t3 is control phase 3, and the controller can identify the number of resonant valleys m0 at t0, the number of resonant valleys m1 at t1, the number of resonant valleys m2 at t2, and so on.

[0052] In addition, the controller determines the grid connection parameters, the upper switching frequency limit f maxand the lower limit of the switching frequency f min For example, at a start time of each control stage, the controller can determine the number of resonant valleys of the power switch S1 based on the grid connection parameters at the start time, when the switching frequency of the power switch S1 is less than or equal to the upper frequency limit and greater than or equal to the lower frequency limit.

[0053] Based on the grid connection parameters, the upper frequency limit and the lower frequency limit, the number of resonance valleys of the power switch at each control stage can be determined, so that each control stage can be used to determine the number of resonance valleys efficiently and accurately.

[0054] In S503, the switching frequency of the power switch is obtained based on the grid connection parameters and the number of resonant valleys.

[0055] Optionally, after determining the number of resonant valleys of the power switch S1, the controller may determine a resonant valley time T of the power switch S1 based on the number of resonant valleys. d and determine the conduction time T based on the grid connection parameters. on and descent time T f Identify and T on =T f +T d The reciprocal of this can be used as the switching frequency of the power switch S1.

[0056] In one exemplary embodiment, after specifying the number of resonance valleys of the power switch at each control stage, the above-mentioned S503 can be optionally implemented in the following manner.

[0057] Based on the grid connection parameters and the number of resonance valleys at each control stage, the switching frequency of the power switch at each control stage is obtained.

[0058] Continuing with the example above, the controller may determine the switching frequency of power switch S1 from t0 to t1 based on the number of resonant valleys m0 and the grid connection parameters, determine the switching frequency of power switch S1 from t1 to t2 based on the number of resonant valleys m1 and the grid connection parameters, determine the switching frequency of power switch S1 from t2 to t3 based on the number of resonant valleys m2 and the grid connection parameters, and so on.

[0059] As can be seen, some of the grid connection parameters vary with time, so that for a constant number of resonant valleys the switching frequency of the power switches also varies at different times during the same control phase.

[0060] Since each control stage is based on the grid connection parameters and the number of resonant valleys at each control stage, the switching frequency of the power switch at each control stage can be efficiently and accurately determined based on the number of resonant valleys.

[0061] In S504, the power switch is controlled based on the switching frequency.

[0062] Furthermore, after determining the switching frequency of the power switch S1, the controller can control the power switch S1 based on the switching frequency. That is, the controller can control the power switch S1 to turn on and off based on the switching frequency determined in S503. It can be understood that after controlling the power switch S1 based on the switching frequency, the switching frequency of the power switch S1 can be equal to or greater than the switching frequency lower limit and equal to or less than the switching frequency upper limit.

[0063] In the above-mentioned grid connection control method for a flyback converter, the grid connection parameters of the flyback converter and the upper and lower frequency limits of the power switches in the flyback converter are obtained, and the number of resonant valleys of the power switches is determined based on the grid connection parameters, the upper and lower frequency limits. The switching frequency of the power switches is then obtained based on the grid connection parameters and the number of resonant valleys, and the power switches can be controlled based on the switching frequency. Furthermore, the number of resonant valleys is determined based on the upper and lower frequency limits, so that the determined switching frequency can be greater than or equal to the lower switching frequency limit and less than or equal to the upper switching frequency limit. This solves the problem of excessively high switching frequencies in the prior art, resulting in large switching losses. Furthermore, the flyback converter operates at a variable switching frequency, which prevents large current stress and improves safety.

[0064] FIG. 6 is a flowchart illustrating a process for determining a switching frequency in an embodiment of the present application. In one exemplary embodiment, as shown in FIG. 6, the above-mentioned step of "obtaining a switching frequency of a power switch at each control stage based on grid connection parameters and the number of resonance valleys at each control stage" includes steps S601 to S602.

[0065] In S601, for each control step, the resonance valley time at the current control step is determined based on the number of resonance valleys at the current control step.

[0066] In this embodiment, the resonance valley time T d is the resonance period T r As can be seen from this, when the number of resonance periods n is different, the number of resonance valleys m is different, and the resonance valley time T d are also different.

[0067] Furthermore, the controller can determine the resonant valley time T of the power switch S1 based on the number of resonant valleys in the current control stage. Taking control stage 1 as an example, where m0=8, the controller can determine the resonant valley time T of the power switch S1 based on the number of resonant valleys m0. d =(7+1 / 2)T r can be identified.

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[0068] In S602, for each control stage, obtain the switching frequency of the power switch at the current control stage based on the resonant valley time at the current control stage and the grid connection parameters.

[0069] Continuing with the example above, the controller determines the resonant valley time T d After identifying the resonance valley time T d and based on the grid connection parameters, the switching frequency of the power switch S1 at control stage 1 can be calculated.

[0070] It is understood that a control stage can include a switching frequency corresponding to at least one time. For example, control stage 1 includes times 1 through 5 and includes a resonant valley time T d Based on the grid connection parameters corresponding to time 1 and time 2, the switching frequency at time 1 is determined, and the resonant valley time T d and the grid connection parameters corresponding to time 2, determine the switching frequency at time 2, and the resonant valley time T d Based on the grid connection parameters corresponding to time 5 and time 6, the switching frequency at time 5 can be determined and can be estimated in the same manner thereafter.

[0071] The other control steps are similar and will not be repeated below.

[0072] In the above embodiment, for each control stage, the resonant valley time for the current control stage is determined based on the number of resonant valleys for the current control stage, and the switching frequency of the power switch for the current control stage can be obtained based on the resonant valley time for the current control stage and the grid connection parameters. Therefore, the switching frequency of the power switch is controlled according to the resonant valley time, so that the switching frequency is greater than or equal to the lower limit of the switching frequency and less than or equal to the upper limit of the switching frequency, thereby improving control efficiency and accuracy.

[0073] FIG. 7 is a diagram showing another flowchart for determining a switching frequency in an embodiment of the present application. In one embodiment, as shown in FIG. 7, “obtaining a switching frequency of a power switch in a current control stage based on a resonant valley time and a grid connection parameter in the current control stage” in the above S602 includes S701 to S702.

[0074] In S701, the on-time and off-time of the current control stage are determined based on the grid connection parameters.

[0075] In this embodiment, as is clear from equations (1) and (2), after the grid connection parameters are identified, the conduction time T on and descent time T f Therefore, the controller can determine the conduction time T of the power switch S1 in the current control stage based on the grid connection parameters using equations (1) and (2). on and descent time T f can be identified.

[0076] Similarly, the conduction time and fall time for the current control stage vary with the grid connection parameters. For example, the conduction time T on is the conduction time T corresponding to time 2 on may differ from the above.

[0077] In S702, the switching frequency of the power switch in the current control stage is obtained based on the conduction time, fall time and resonance valley time in the current control stage.

[0078] Continuing with the control stage 1 as an example, the controller determines the conduction time T on , descent time T f and the resonance valley time T d and T on +T f +T d Identify and T on +T f +T d The reciprocal of the value can be used as the switching frequency of the power switch S1 in the control stage 1.

[0079] FIG. 8 is a schematic diagram illustrating the principle of the valley switch in the embodiment of the present application. As shown in FIG. 8, the peak current I pp is specified, the conduction time T on and descent time T f Furthermore, by adjusting the number m of resonance valleys of the power switch, the resonance valley time T d , which controls one switching period of the power switch S1 and further controls the switching frequency of the power switch S1. For simplicity of explanation, hereinafter, the number of resonance valleys m is expressed using the number of resonance periods n. For example, in FIG. 8, when the number of resonance periods n=2, the resonance valley time T d >Resonance valley time T when the number of resonance periods n=1 d >Resonance valley time T when the number of resonance periods n=0 d is.

[0080] In the above embodiment, the conduction time and fall time at the current control stage are determined based on the grid connection parameters, and the switching frequency of the power switch at the current control stage is obtained based on the conduction time, fall time and resonant valley time at the current control stage. In this way, the switching frequency of the power switch at the current control stage is obtained based on the resonant valley time at the current control stage and the grid connection parameters, and the control efficiency of the switching frequency is improved.

[0081] In one exemplary embodiment, the above-mentioned "obtaining the switching frequency of the power switch at each control stage based on the grid connection parameters and the number of resonance valleys at each control stage" can be further realized in the following manner.

[0082] Using the first target formula, the switching frequency of the power switch at the current control stage is obtained according to the number of resonance valleys at the current control stage and the grid connection parameters.

[0083]

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[0084] In this embodiment, when equations (1), (2), (3), (8), and (12) are solved simultaneously, the following equation (13) can be obtained.

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[0085] C1, C2, and C3 in the formula (13) satisfy the following formula (14).

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[0086] Furthermore, by simultaneously solving equations (1), (2), (8), and (13), the switching frequency f of the power switch S1 is given by the following equation (15): sw can be identified.

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[0087] Furthermore, equation (15) is the first target equation, and the switching frequency f sw and the number of resonant periods n and peak current I pp In other words, the first objective equation is to establish the relationship between the switching frequency f sw and the number of resonance valleys m and peak current I pp Therefore, the first target equation can control the switching frequency of the power switch in the current control stage based on the number of resonance valleys of the power switch in the current control stage and the grid connection parameters. For example, in control stage 1, when n=m0-1 in equation (15), the switching frequency f of the power switch S1 in control stage 1 is sw Identify.

[0088] In the above embodiment, the first target formula is used to obtain the switching frequency of the power switch at the current control stage based on the number of resonance valleys at the current control stage and the grid connection parameters, thereby improving the efficiency of identifying the switching frequency.

[0089] FIG. 9 is a flowchart illustrating the process of determining the number of resonance valleys in an embodiment of the present application. In one embodiment, as shown in FIG. 9, the above-mentioned process of "determining the number of resonance valleys of the power switch at each control stage based on the grid connection parameters, the upper frequency limit, and the lower frequency limit" includes steps S901 to S902.

[0090] In S901, when the voltage of the power grid is at a zero crossing point, a number of candidate resonant valleys is identified based on the grid connection parameters, the upper frequency limit, and the lower frequency limit.

[0091] Optionally, when the grid voltage is at the zero crossing point, the controller can adjust θ grid =0° and switching frequency fsw is the lower limit of the switching frequency f min or higher or upper switching frequency limit f max A number of candidate resonant valleys can be identified that is:

[0092] In S902, the number of resonance valleys at the control stage corresponding to when the voltage of the power grid is at the zero crossing point is identified from the number of each candidate resonance valley.

[0093] Furthermore, after identifying the number of candidate resonant valleys, the controller can identify the number of resonant valleys m0 in the first control stage when the voltage is at the zero crossing point from each of the candidate resonant valleys. Illustratively, the numbers of candidate resonant valleys may be 8, 7, 6, 5, 4, and 3, respectively, and the computing device may determine that the number of resonant valleys in control stage 1 is any one of 8, 7, 6, 5, 4, and 3.

[0094] In some embodiments, when the grid voltage is near the zero crossing point, the grid-tied current is also small, so the switching frequency f sw To reduce the switching loss at light loads by lowering the value of the resonant valley, the controller may set the maximum number of resonant valleys among the number of candidate resonant valleys as the number of resonant valleys in the first control step.

[0095] In the above embodiment, when the voltage of the power grid is at a zero-crossing point, a number of candidate resonant valleys is identified based on the grid connection parameters, the upper frequency limit, and the lower frequency limit, and the number of resonant valleys at the control stage corresponding to the voltage of the power grid at the zero-crossing point is identified from each number of candidate resonant valleys. Therefore, when the voltage of the power grid is at a zero-crossing point, the number of the identified candidate resonant valleys can all be such that the switching frequency of the power switch is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit, thereby solving the problem of excessively high switching losses caused by the switching frequency in the prior art.

[0096] In one exemplary embodiment, optionally, the above-mentioned step S901 "identifying the number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit" can be realized in the following manner.

[0097] A second target formula is used to identify the number of candidate resonance valleys based on the grid connection parameters, upper frequency limit, and lower frequency limit.

[0098] The second objective formula is as follows:

number

[0099] In this embodiment, based on equation (15), the voltage of the power grid passes through the zero crossing point, that is, θ grid As the switching frequency f of power switch S1 approaches 0, sw is as shown in equation (16).

number

[0100] For example, at time t0, the voltage of the power grid passes through the zero crossing point, and at time t0, the controller min <Formula (16) <f max By solving as above, the number of candidate resonance valleys can be identified.

[0101] Furthermore, optionally, after finding a solution based on equation (16) and obtaining the number of candidate resonant valleys, the controller may set the smallest positive integer among the number of candidate resonant valleys as the number of resonant valleys at the control stage corresponding to when the voltage of the power grid is at the zero crossing point.

[0102] In the above embodiment, a second target formula can be used to identify the number of candidate resonance valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit, thereby improving the efficiency of identifying the number of candidate resonance valleys.

[0103] FIG. 10 is a flowchart illustrating a method for controlling the switching frequency in an embodiment of the present application. In one exemplary embodiment, as shown in FIG. 10, the above-described step of "determining the number of resonant valleys of the power switch at each control stage based on the grid connection parameters, the upper frequency limit, and the lower frequency limit" includes steps S1001 to S1002.

[0104] In S1001, the switching frequency in the current control stage is determined based on the number of resonance valleys in the previous control stage.

[0105] In this embodiment, as can be seen from equation (15), when the number of resonance valleys is constant, sin(θ grid ) increases, the switching frequency f sw As the switching frequency f of the power switch S1 decreases, sw is the lower limit of the switching frequency f min or higher or upper switching frequency limit f max The controller determines the switching frequency at the current control stage based on the number of resonant valleys at the previous control stage, so that: Optionally, the controller can determine the switching frequency at the current control stage based on grid connection parameters at the current control stage.

[0106] Illustratively, the controller calculates that the number of resonant valleys in control stage 1 at time t0 is m0, and for control stage 2, the controller can subsequently determine the switching frequency of control stage 2 based on the number of resonant valleys m0 in control stage 1.

[0107] In S1002, if the switching frequency at the current control stage is lower than the lower frequency limit or higher than the upper frequency limit, adjust the number of resonance valleys at the previous control stage to obtain the number of resonance valleys at the current control stage.

[0108] In this embodiment, if the switching frequency in the current control stage is smaller than the lower frequency limit or larger than the upper frequency limit, reusing the number of resonant valleys in the previous control stage will prevent the switching frequency in the current control stage from meeting the requirements. Therefore, in order to ensure that the switching frequency in the current control stage is greater than the lower frequency limit and less than the upper frequency limit, the controller adjusts the number of resonant valleys in the previous control stage to obtain the number of resonant valleys in the current control stage.

[0109] Optionally, the controller may take the adjusted number of resonant valleys as the number of resonant valleys in the current control stage, provided that the controller can increase or decrease the number of resonant valleys in the previous control stage with a certain compensation until it calculates that the switching frequency is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit based on the adjusted number of resonant valleys.

[0110] Note that the switching frequency in the current control stage being lower than the lower frequency limit or higher than the upper frequency limit includes the case where the switching frequency at any time in the current control stage is lower than the lower frequency limit or higher than the upper frequency limit.

[0111] In S1003, if the switching frequency in the current control stage is equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit, the number of resonance valleys in the previous control stage is set as the number of resonance valleys in the current control stage.

[0112] In this embodiment, when the switching frequency in the current control stage is equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit, the number of resonance valleys in the previous control stage can be continued to be used, so that the switching frequency in the current control stage is equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit. Therefore, to ensure that the switching frequency in the current control stage is equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit, the number of resonance valleys in the previous control stage can be used as the number of resonance valleys in the current control stage.

[0113] The switching frequency at the current control stage being equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit includes the switching frequencies at each point in time at the current control stage being equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit.

[0114] FIG. 11 is a schematic diagram of the control process in the embodiment of the present application. The upper diagram in FIG. 11 shows the peak current I pp The diagram in the lower part of FIG. 11 shows the case where the switching frequency of the power switch S1 changes with time.

[0115] Continuing with the example above, t0 is the zero crossing point of the voltage on the power grid, and at time t0, the controller min <Formula (16) <f max By solving as above, the number of resonance valleys in control stage 1 is determined to be m0=8, and the number of resonance periods is then n0=7.

[0116] During the process from t0 to t1, sin(θ grid ) increases, the switching frequency f sw gradually decreases, and at time t1, if the number of resonance valleys m0=8 continues to operate, the switching frequency f of the power switch S1 sw < Switching frequency lower limit f min If so, the controller reduces m0 at time t1 to obtain m1, for example, m1=m0-2=6, and then the number of resonance periods n1=5.

[0117] During the period t1 to t2, sin(θ grid ) increases, the switching frequency f sw gradually decreases, and at time t2, if the number of resonant valleys m1=6 continues to operate, the switching frequency f sw < Switching frequency lower limit f minIf so, the controller reduces m1 at time t2 to obtain m2, for example, m2=m1-2=4, where the number of resonance periods n2=3, and so on.

[0118] In the above, an example was given in which the value is decreased by 2 each time, but when adjusting the number of resonance valleys in the previous control stage, a different value may be decreased each time, and this embodiment is not limited to this.

[0119] In the above embodiment, the switching frequency in the current control stage is determined based on the number of resonance valleys in the previous control stage, and if the switching frequency in the current control stage is lower than the lower frequency limit or higher than the upper frequency limit, the number of resonance valleys in the previous control stage is adjusted to obtain the number of resonance valleys in the current control stage, and if the switching frequency in the current control stage is equal to or higher than the lower frequency limit and lower than the upper frequency limit, the number of resonance valleys in the previous control stage is used as the number of resonance valleys in the current control stage. In this way, the switching frequency of the power switch can be made to be equal to or higher than the lower frequency limit and lower than the upper frequency limit, thereby improving safety.

[0120] In one embodiment, as an example, the option in S902 above of "adjusting the number of resonance valleys in the previous control step to obtain the number of resonance valleys in the current control step" can be realized in the following manner.

[0121] phase angle θ grid is in [k × 180°, k × 180° + 90°], the number of resonance valleys in the current control step is reduced, and the number of resonance valleys in the next control step is identified.

[0122] phase angle θ grid is not in [k×180°, k×180°+90°], the number of resonance valleys in the current control step is increased to identify the number of resonance valleys in the next control step.

[0123] In this embodiment, k is a natural number, and the phase angle θ of the voltage of the power grid grid is usually sinusoidally varying, with a peak current I ppAs can be seen from FIG. 11, taking 360° as an example, the phase angle θ grid When is greater than or equal to 0° and less than or equal to 90°, and greater than or equal to 180° and less than or equal to 270°, the peak current I pp is the phase angle θ grid and the peak current I pp is the phase angle θ grid changes in the opposite direction.

[0124] Peak current I pp is the phase angle θ grid When the switching frequency f of the power switch S1 changes in the same direction as sw Since the number of resonant valleys must be reduced, the resonant valley time T d and the switching frequency f of the power switch S1 is reduced. sw Furthermore, the phase angle θ grid is in [k×180°, k×180°+90°], the controller decreases the number of resonance valleys in the current control step, thereby determining the number of resonance valleys in the next control step, and may also decrease the number of resonance valleys in the previous control step by a first set value.

[0125] Peak current I pp is the phase angle θ grid When the switching frequency of the power switch S1 changes in the opposite direction, sw , the number of resonant valleys needs to be increased gradually, so that the resonant valley time T of the power switch d , which increases the switching frequency f of the power switch S1. sw Furthermore, the phase angle θ grid is not in [k×180°, k×180°+90°], the controller increases the number of resonance valleys in the current control step, thereby determining the number of resonance valleys in the next control step, and may also increase the number of resonance valleys in the previous control step by a second set value.

[0126] In the above embodiment, k is a natural number, and the power grid is connected to a flyback converter. If the phase angle of the power grid voltage of the power grid is within [k×180°, k×180°+90°], the number of resonant valleys in the current control stage is decreased to determine the number of resonant valleys in the next control stage. If the phase angle is not within [k×180°, k×180°+90°], the number of resonant valleys in the current control stage is increased to determine the number of resonant valleys in the next control stage. Therefore, after adjusting the number of resonant valleys in the previous control stage to obtain the number of resonant valleys in the current control stage, the number of resonant valleys in the current control stage can be made to be greater than the lower frequency limit and less than the upper frequency limit.

[0127] FIG. 12 illustrates another flowchart for determining a switching frequency in an embodiment of the present application. In one exemplary embodiment, as shown in FIG. 12, the grid-connected control method for a flyback converter described above further includes steps S1201 to S1202.

[0128] In S1201, a switching frequency of the power switch at a preset period is identified based on the switching frequency of the power switch, and the preset period is a period of a preset multiple of the commercial power frequency.

[0129] In this embodiment, the commercial power frequency refers to the frequency of the commercial power supply. For example, if the commercial power frequency is 50 Hz, the period of the commercial power supply may be 0.02 seconds. The preset multiple may be any number greater than 0. For example, the preset multiple may be 1 / 2 or 1 / 4, or may be 1 or 2, for example.

[0130] Taking the period of 1 / 4 commercial power frequency as an example, and still referring to FIG. 11, continuing the above example, the controller executes according to the above flow, and in the process from t3 to t4, sin(θ grid ) increases, the switching frequency f swgradually decreases, and at time t4, it continues to operate at the number of resonant valleys m3, and the switching frequency f of the power switch S1 sw < Switching frequency lower limit f min If so, the controller decreases n3 at time t4 to obtain n4, and then, during the period from t4 to t5, grid =90°, sin(θ grid ) = 1, and at this time, the number of resonance valleys in the current control stage is the smallest. In this way, the periodic adjustment of 1 / 4 commercial power frequency is completed.

[0131] In S1202, the switching frequency in each control stage of the power switch is determined based on the switching frequency of the power switch in a preset period.

[0132] Continuing with the above example, the switching frequency of the power switch is determined at a period of 1 / 4 the commercial power frequency. Since the period of the commercial power frequency has a regularity, the switching frequency of the power switch in each control stage can be determined based on the switching frequency of the power switch at a predetermined period. For example, the phase angle θ of the power switch can be determined by a processing method such as symmetry or replication. grid The switching frequency within each control step can be determined by the 360°.

[0133] Still referring to FIG. 11, the controller controls the phase angle θ grid is 0 to 90°, that is, the phase angle θ is symmetrical with respect to the switching frequency at a period of 1 / 4 of the commercial power frequency before the power switch. grid The switching frequency of the power switch when the angle is 90 to 180° can be obtained.

[0134] Furthermore, the controller controls the phase angle θ grid is 0 to 180°, that is, the phase angle θ grid The switching frequency of the power switch when the angle is 180 to 360° can be obtained.

[0135] In the above embodiment, the predetermined period is a period of a predetermined multiple of the commercial power frequency, and the switching frequency of the power switch at the predetermined period is determined based on the switching frequency of the power switch, and the switching frequency of the power switch at each control stage can be determined based on the switching frequency of the power switch at the predetermined period. In this way, the switching frequency of the power switch at each control stage can be determined efficiently and accurately.

[0136] FIG. 13 is a schematic diagram illustrating the steps of a grid-connected control method for a flyback converter in an embodiment of the present application. In one exemplary embodiment, the controller can perform the method according to the following flow:

[0137] In S1301, the grid connection parameters of the flyback converter, and the upper and lower frequency limits of the power switch in the flyback converter are obtained.

[0138] In S1302, when the voltage of the power grid is at a zero crossing point, a second target formula is used to identify the number of multiple candidate resonance valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit.

[0139] In S1303, the number of resonance valleys at the control stage corresponding to when the voltage of the power grid is at the zero crossing point is identified from the number of each candidate resonance valley.

[0140] In S1304, the switching frequency in the current control step is determined based on the number of resonance valleys in the previous control step.

[0141] In S1305, if the switching frequency in the current control stage is lower than the lower frequency limit or higher than the upper frequency limit, adjust the number of resonance valleys in the previous control stage to obtain the number of resonance valleys in the current control stage.

[0142] In S1306, if the switching frequency in the current control stage is equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit, the number of resonance valleys in the previous control stage is set as the number of resonance valleys in the current control stage.

[0143] In S1307, the first target equation is used to obtain the switching frequency of the power switch in the current control stage according to the number of resonance valleys in the current control stage and the grid connection parameters.

[0144] In S1308, the switching frequency of the power switch in a preset period is identified based on the switching frequency of the power switch.

[0145] In S1309, the switching frequency of the power switch at each control stage is determined based on the switching frequency of the power switch in a preset cycle.

[0146] In S1310, the power switch is controlled based on the switching frequency.

[0147] Steps S1301 to S1310 can be referred to in the above embodiments and will not be repeated here. As can be seen, this embodiment proposes a method for optimizing the efficiency of a flyback converter by extending the soft switching range. Based on a mathematical model of a multi-valley switch in a flyback converter, a calculation process and control method for the peak current reference and switching frequency for controlling the switch transistor are provided. The flyback converter operates in discontinuous conduction mode and calculates the number of valleys when the power switch is turned on based on the grid-connected power and a preset switching frequency range.

[0148] Table 1 provides the simulation parameters of the flyback converter, and simulation verification is performed on the frequency of the power switch according to the parameters in Table 1. To adjust the switching frequency of the power switch S1 between an upper limit of 250 kHz and a lower limit of 190 kHz, n=7 and m=8 are calculated based on equation (16) when the power grid voltage is at the zero crossing point. As the instantaneous power increases, when the switching frequency calculated by equation (15) is equal to 190 kHz, n switches to 4 and m=5. When the switching frequency reaches the lower limit of 190 kHz, n switches to 2, 1, and 0, respectively, and the same can be estimated thereafter.

[0149] (Simulation parameters) [Table 1]

[0150] 14A to 14E are simulation results of the embodiment of the present invention. The results are shown in Figs. 14A to 14E, respectively, for different resonance periods n, i.e., different numbers m of resonance valleys, and show the drive signal of the power switch S1 and the drain-source voltage V of the power switch S1. DS As can be seen, the upper waveforms in Fig. 14(a) to Fig. 14(e) are schematic diagrams of the waveforms of the drive signals, and the lower waveforms in Fig. 14(a) to Fig. 14(e) are schematic diagrams of the drain-source voltage V DS 14, according to the control method of this embodiment, valley switching can be achieved in all different load conditions of n=0, 1, 2, 4, and 7 in the resonance period.

[0151] FIG. 15 is a schematic diagram of power parameters in an embodiment of the present application, and FIG. 15 shows the voltage of the flyback converter power grid, the grid-connected current, and the secondary current i s The principle disclosed in equation (3) can also be verified by referring to FIG.

[0152] Although the steps shown in the flowcharts according to the above-described embodiments are shown in the order indicated by the arrows, it should be understood that the steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they may be executed in other orders. Furthermore, at least some of the steps in the flowcharts according to the above-described embodiments may include multiple steps or multiple stages, and these steps or stages do not necessarily have to be executed and completed simultaneously, but may be executed at different times. The execution order of these steps or stages is also not necessarily executed consecutively, and they may be executed alternately or sequentially with other steps or at least some of the steps or stages included in other steps.

[0153] Based on the same inventive concept, the embodiments of the present application further provide a grid-connected control device for a flyback converter for implementing the above-mentioned grid-connected control method for a flyback converter. The means for solving the problem provided by the device are similar to those described in the above-mentioned method. Therefore, for specific limitations of one or more embodiments of the grid-connected control device for a flyback converter provided below, reference may be made to the limitations of the above-mentioned grid-connected control method for a flyback converter, and these limitations will not be repeated here.

[0154] FIG. 16 is a block diagram of a grid-connected control device of a flyback converter according to an embodiment of the present application. In one embodiment, as shown in FIG. 16, a grid-connected control device 1600 of a flyback converter is provided, which includes: a first acquisition module 1601, a first determination module 1602, a second determination module 1603, and a control module 1604;

[0155] The first obtaining module 1601 is for obtaining grid connection parameters of the flyback converter, the upper frequency limit and the lower frequency limit of the power switch in the flyback converter.

[0156] The first identification module 1602 is for identifying the number of resonant valleys of the power switch based on the grid connection parameters, the upper frequency limit and the lower frequency limit.

[0157] The second identification module 1603 is for obtaining the switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys.

[0158] The control module 1604 is for controlling the power switch based on the switching frequency.

[0159] In some embodiments, the first identification module also specifically: determining a number of resonant valleys of the power switch at each control stage based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; obtaining a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; and deriving a switching frequency of the power switch at each of the control stages based on the grid connection parameters and the number of resonant valleys at each of the control stages.

[0160] In some embodiments, the first identification module also specifically: For each of said control steps, determining a resonant valley time for the current control stage based on the number of resonant valleys for the current control stage; A switching frequency of the power switch at the current control stage is obtained based on a resonant valley time at the current control stage and the grid connection parameters.

[0161] In some embodiments, the first identification module also specifically: determining a conduction time and a fall time for the current control stage based on the grid connection parameters; A switching frequency of the power switch at the current control stage is obtained based on the conduction time at the current control stage, the fall time, and the resonant valley time.

[0162] In some embodiments, the first identification module also specifically: A first target equation is used to obtain a switching frequency of the power switch at the current control stage based on the number of resonance valleys at the current control stage and the grid connection parameters.

[0163]

number

[0164] In some embodiments, the first identification module also specifically: When the voltage of the power grid is at a zero crossing point, identifying a number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; From the number of each of the candidate resonance valleys, the number of resonance valleys at the control stage corresponding to when the voltage of the power grid is at a zero crossing point is identified.

[0165] In some embodiments, the first identification module may also include: utilizing a second target equation to identify a number of the plurality of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; The second target formula is as follows:

number

[0166] In some embodiments, the first identification module also specifically: Identifying the switching frequency at the current control stage based on the number of resonant valleys at the previous control stage; if the switching frequency at the current control stage is less than the lower frequency limit or greater than the upper frequency limit, adjust the number of resonance valleys at the previous control stage to obtain the number of resonance valleys at the current control stage; If the switching frequency in the current control stage is equal to or greater than the lower frequency limit and equal to or less than the upper frequency limit, the number of resonance valleys in the previous control stage is set to the number of resonance valleys in the current control stage.

[0167] In some embodiments, the apparatus also further comprises a third identification module; The third identification module is Identifying a switching frequency of the power switch at a preset period based on a switching frequency of the power switch, the preset period being a period of a commercial power supply frequency that is a preset multiple of the commercial power supply frequency; The switching frequency of the power switch at each of the control stages is determined based on the switching frequency of the power switch at a preset period.

[0168] Each module of the grid-tied controller for a flyback converter described above may be realized in whole or in part by software, hardware, or a combination thereof. Each module may be implemented in hardware form or may exist independently of the processor of a computer device, and may be stored in the memory of a computer device in software form, which the processor can invoke to perform the operations corresponding to each module.

[0169] FIG. 17 is a diagram illustrating the internal configuration of a computer device according to an embodiment of the present application. In one embodiment, a computer device capable of functioning as a server is provided. The internal configuration is shown in FIG. 17. The computer device includes a processor, a memory, an input / output interface (I / O), and a communication interface. The processor, memory, and I / O interface are connected via a system bus, and the communication interface is connected to the system bus via the I / O interface. The processor of the computer device provides calculation and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the execution of the operating system and computer programs in the non-volatile storage medium. The database of the computer device stores relevant data. The I / O interface of the computer device is for exchanging information between the processor and an external device. The communication interface of the computer device is for communicating with an external terminal via a network connection. The computer program, when executed by a processor, implements a method for grid-tied control of a flyback converter.

[0170] As will be understood by those skilled in the art, the structure shown in Figure 17 is merely a block diagram of a portion of the structure according to the solution of the present application, and does not limit the computer device to which the present invention is applicable. A specific computer device may include more or fewer components than those shown in the figure, or may combine certain components or have a different component arrangement.

[0171] In one embodiment, a computer device is provided that includes a memory and a processor, the memory storing a computer program that, when executed by the processor, performs the steps of each of the method embodiments described above.

[0172] In one embodiment, a computer-readable recording medium is provided having stored thereon a computer program that, when executed by a processor, performs the steps of each of the method embodiments described above.

[0173] In one embodiment, a computer program product is provided that includes a computer program that, when executed by a processor, performs the steps of each of the method embodiments described above.

[0174] As will be understood by those skilled in the art, implementing all or part of the steps in the above-described methods can be accomplished by instructing associated hardware with a computer program. The computer program may be stored in a non-volatile computer-readable recording medium and, when executed, may include the steps of the above-described method embodiments. Furthermore, any reference to memory, database, or other medium used in the embodiments provided herein may include at least one of non-volatile memory and volatile memory. Non-volatile memory may include read-only memory (ROM), tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. For example, and not by way of limitation, the RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database according to the embodiments provided herein may include at least one of a relational database and a non-relational database. The non-relational database may include, but is not limited to, a blockchain-based distributed database. The processor according to the embodiments provided herein may be, but is not limited to, a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, data processing logic based on quantum computing, etc.

[0175] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all combinations of the technical features in the above-described embodiments are described, but any combination of these technical features should be considered within the scope of the present specification unless there is a contradiction.

[0176] The above examples merely illustrate some embodiments of the present application, and although the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of the invention. Those skilled in the art may make minor modifications and improvements without departing from the spirit of the present application, and all of these modifications and improvements are within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined in accordance with the claims.

Claims

1. 1. A method for grid-tied control of a flyback converter, comprising: Obtaining grid connection parameters of a flyback converter, upper and lower frequency limits of a power switch in the flyback converter; determining a number of resonant valleys of the power switch based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; obtaining a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; and controlling the power switch based on the switching frequency.

2. determining a number of resonant valleys of the power switch based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; determining a number of resonant valleys of the power switch at each control stage based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; obtaining a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; 2. The method of claim 1, comprising deriving a switching frequency of the power switch at each of the control stages based on the grid connection parameters and a number of resonant valleys at each of the control stages.

3. obtaining a switching frequency of the power switch at each of the control stages based on the grid connection parameters and a number of resonance valleys at each of the control stages, for each said control step, determining a resonant valley time at said current control step based on the number of resonant valleys at said current control step; 3. The method of claim 2, comprising deriving a switching frequency of the power switch at the current control stage based on a resonant valley time at the current control stage and the grid connection parameters.

4. obtaining a switching frequency of the power switch at the current control stage based on a resonant valley time at the current control stage and the grid connection parameter, determining a conduction time and a fall time for the current control stage based on the grid connection parameters; and deriving a switching frequency of the power switch at the current control stage based on the conduction time, the fall time, and the resonant valley time at the current control stage.

5. obtaining a switching frequency of the power switch at each of the control stages based on the grid connection parameters and a number of resonance valleys at each of the control stages, 3. The method of claim 2, comprising: utilizing a first target equation to obtain a switching frequency of the power switch at the current control stage based on a number of resonant valleys at the current control stage and the grid connection parameters. However, the first target formula is as follows: [Equation 1]

6. determining a number of resonant valleys of a power switch at each control stage based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; Identifying a number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit when the voltage of the power grid is at a zero crossing point; and identifying, from each of the number of candidate resonant valleys, the number of resonant valleys at a control stage corresponding to when the voltage of the power grid is at a zero crossing point.

7. identifying a number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; 7. The method of claim 6, further comprising: utilizing a second target equation to identify the number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit. However, the second target formula is as follows: [Equation 2]

8. determining a number of resonant valleys of a power switch at each control stage based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; determining a switching frequency in a current control stage based on the number of resonant valleys in a previous control stage; If the switching frequency at the current control stage is less than the lower frequency limit or greater than the upper frequency limit, adjusting the number of resonance valleys at the previous control stage to obtain the number of resonance valleys at the current control stage. The method according to any one of claims 2 to 7, characterized in that, when the switching frequency in the current control stage is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit, the number of resonance valleys in the previous control stage is set to the number of resonance valleys in the current control stage.

9. moreover, Identifying a switching frequency of the power switch at a preset period based on a switching frequency of the power switch, the preset period being a period of a commercial power supply frequency that is a preset multiple of the period; and specifying a switching frequency of the power switch at each of the control stages based on a switching frequency of the power switch at a preset period.

10. 1. A grid-tied controller for a flyback converter, comprising: a first acquisition module used to acquire grid connection parameters of a flyback converter, an upper frequency limit and a lower frequency limit of a power switch in the flyback converter; a first identification module used to identify a number of resonant valleys of the power switch based on the grid connection parameters, the upper frequency limit, and the lower frequency limit; a second identification module used to obtain a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; a control module used to control the power switch based on the switching frequency.

11. The first determination module specifically determines the number of resonance valleys of the power switch at each control stage according to the grid connection parameters, the upper frequency limit, and the lower frequency limit; obtaining a switching frequency of the power switch based on the grid connection parameters and the number of resonant valleys; 11. The apparatus of claim 10, further comprising: deriving a switching frequency of the power switch at each of the control stages based on the grid connection parameters and a number of resonant valleys at each of the control stages.

12. The first identification module specifically includes: for each said control step, determining a resonant valley time at said current control step based on the number of resonant valleys at said current control step; The apparatus of claim 11, further comprising: obtaining a switching frequency of the power switch at the current control stage based on a resonant valley time at the current control stage and the grid connection parameters.

13. The first identification module specifically includes: determining a conduction time and a fall time for the current control stage based on the grid connection parameters; 13. The apparatus of claim 12, further comprising: deriving a switching frequency of the power switch at the current control stage based on a conduction time at the current control stage, the fall time, and the resonant valley time.

14. 12. The apparatus of claim 11 , wherein the first identification module specifically uses a first target equation to obtain a switching frequency of the power switch at the current control stage according to a number of resonance valleys at the current control stage and the grid connection parameters. However, the first target formula is as follows: [Equation 3]

15. The first identification module specifically includes: Identifying a number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit when the voltage of the power grid is at a zero crossing point; The apparatus of claim 14, further comprising: determining, from each of the number of candidate resonant valleys, the number of resonant valleys at a control stage corresponding to when the voltage of the power grid is at a zero crossing point.

16. The first identification module specifically includes:

16. The apparatus of claim 15, further comprising: utilizing a second target equation to identify the number of candidate resonant valleys based on the grid connection parameters, the upper frequency limit, and the lower frequency limit. However, the second target formula is as follows: [Equation 4]

17. The first identification module specifically includes: Identifying the switching frequency at the current control stage based on the number of resonant valleys at the previous control stage; If the switching frequency in the current control stage is less than the lower frequency limit or greater than the upper frequency limit, adjust the number of resonance valleys in the previous control stage to obtain the number of resonance valleys in the current control stage; The device described in any one of claims 11 to 16, characterized in that when the switching frequency in the current control stage is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit, the number of resonant valleys in the previous control stage is set to the number of resonant valleys in the current control stage.

18. the apparatus further includes a third identification module; The third identification module: Identifying a switching frequency of the power switch at a preset period based on a switching frequency of the power switch, the preset period being a period of a commercial power supply frequency that is a preset multiple of the commercial power supply frequency; The device according to any one of claims 11 to 16, characterized in that the switching frequency of the power switch at each of the control stages is determined based on the switching frequency of the power switch at a preset period.

19. 1. A computing device comprising: Includes memory and a processor, A computer device, characterized in that the memory stores a computer program, and when the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are performed.

20. A computer-readable recording medium storing a computer program, 10. A computer-readable recording medium, comprising the computer program, when executed by a processor, to perform the steps of the method according to any one of claims 1 to 9.

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