Grid-connected control method and apparatus for flyback converter, and computer device

Abstract

The present application relates to a grid-connected control method and apparatus for a flyback converter, and a computer device. The method comprises: acquiring grid-connected parameters of a flyback converter, and an upper frequency limit and a lower frequency limit of a power switch in the flyback converter; determining the number of resonant troughs of the power switch on the basis of the grid-connected parameters, the upper frequency limit, and the lower frequency limit; then obtaining the switching frequency of the power switch on the basis of the grid-connected parameters and the number of the resonant troughs; and controlling the power switch on the basis of the switching frequency. The method can improve the safety.

Description

Grid-connected control method, device and computer equipment for flyback converter

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2024101100072, filed on January 26, 2024, entitled “Grid-connected control method, device and computer equipment for flyback converter”, the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of circuit technology, and in particular to a grid-connected control method, device, and computer equipment for a flyback converter. Background Art

[0004] Flyback converters are widely used due to their high-frequency electrical isolation, simple structure, and low cost. Flyback converters can be divided into two types: Boundary Conduction Mode (BCM) and Discontinuous Conduction Mode (DCM).

[0005] If the flyback converter operates in BCM, the switching frequency of the power switch is very high at light loads, such as when the grid voltage crosses zero, resulting in significant switching losses. If the flyback converter operates in DCM with a fixed switching frequency, the current stress on the power switch can be significant at heavy loads, such as when the grid voltage reaches its peak. Therefore, current switching frequency control methods have a low safety issue.

[0006] Summary of the Invention

[0007] Based on this, it is necessary to provide a grid-connected control method, device and computer equipment for a flyback converter that can improve safety in order to address the above technical issues.

[0008] In a first aspect, the present application provides a grid-connected control method for a flyback converter, comprising:

[0009] Obtain the grid-connected parameters of the flyback converter and the upper and lower frequency limits of the power switch in the flyback converter;

[0010] Determine the number of resonance valleys of the power switch based on grid-connected parameters, upper and lower frequency limits;

[0011] According to the grid-connected parameters and the number of resonance valleys, the switching frequency of the power switch is obtained;

[0012] The power switches are controlled according to the switching frequency.

[0013] In a second aspect, the present application further provides a grid-connected control device for a flyback converter, comprising:

[0014] A first acquisition module is used to obtain the grid-connected parameters of the flyback converter and the upper and lower frequency limits of the power switch in the flyback converter;

[0015] A first determining module is used to determine the number of resonance valleys of the power switch according to the grid connection parameters, the upper frequency limit and the lower frequency limit;

[0016] A second determination module is used to obtain a switching frequency of the power switch according to the grid connection parameters and the number of resonance valleys;

[0017] The control module is used to control the power switch according to the switching frequency.

[0018] In a third aspect, the present application further provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any of the above methods when executing the computer program.

[0019] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of any of the above methods when executed by a processor.

[0020] In a fifth aspect, the present application also provides a computer program product, comprising a computer program, which implements the steps of any of the above methods when executed by a processor.

[0021] The above-described flyback converter grid-connected control method, device, and computer device obtain the flyback converter's grid-connected parameters and the upper and lower frequency limits of the power switch in the flyback converter, and determine the number of resonance valleys of the power switch based on the grid-connected parameters, the upper and lower frequency limits. Therefore, after obtaining the switching frequency of the power switch based on the grid-connected parameters and the number of resonance valleys, the power switch can be controlled based on the switching frequency. Furthermore, because the number of resonance valleys is determined based on the upper and lower frequency limits, the determined switching frequency can be no less than the lower switching frequency limit and no greater than the upper switching frequency limit. This solves the existing problem of high switching losses caused by excessively high switching frequencies. Furthermore, the flyback converter operates at a variable switching frequency, which does not cause significant current stress and improves safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] FIG1 is a topological structure of a two-stage flyback converter;

[0024] FIG2 is a schematic diagram of critical conduction mode;

[0025] FIG3 is a schematic diagram of the discontinuous conduction mode;

[0026] FIG4 is an application environment diagram of a grid-connected control method for a flyback converter according to an embodiment of the present application;

[0027] FIG5 is a flow chart of a grid-connected control method for a flyback converter according to an embodiment of the present application;

[0028] FIG6 is a schematic diagram of a flow chart for determining a switching frequency in an embodiment of the present application;

[0029] FIG7 is a schematic diagram of another flow chart for determining a switching frequency according to an embodiment of the present application;

[0030] FIG8 is a schematic diagram of the principle of a valley switch in an embodiment of the present application;

[0031] FIG9 is a schematic diagram of a process for determining the number of resonance valleys according to an embodiment of the present application;

[0032] FIG10 is a schematic diagram of a flow chart of controlling a switching frequency in an embodiment of the present application;

[0033] FIG11 is a schematic diagram of a control process in an embodiment of the present application;

[0034] FIG12 is a schematic diagram of another flow chart for determining a switching frequency according to an embodiment of the present application;

[0035] FIG13 is a schematic diagram of a process of a grid-connected control method for a flyback converter according to an embodiment of the present application;

[0036] FIG14 is a simulation effect diagram of an embodiment of the present application;

[0037] FIG15 is a schematic diagram of an electric power parameter in an embodiment of the present application;

[0038] FIG16 is a structural block diagram of a grid-connected control device for a flyback converter according to an embodiment of the present application;

[0039] FIG17 is a diagram showing the internal structure of a computer device in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0041] Flyback converters are widely used in circuits because they provide insulation isolation between the input and output stages. The following uses a two-stage flyback converter as an example. The principles of other flyback converters are similar and will not be further elaborated here.

[0042] FIG1 is a topology structure of a two-stage flyback converter. As shown in FIG1 , the 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 The flyback converter includes a power switch S1, a transformer T1, and a diode D1.

[0043] Among them, the filter capacitor C in Connected to the flyback converter's input, power switch S1 controls the flyback topology's energy transfer, mitigating second harmonic currents caused by transient power imbalances between the power source and the grid. When power source P1 is a photovoltaic panel, first-stage structure 101 can also implement maximum power point tracking (MPPT).

[0044] The second stage structure 102 includes a bus capacitor C bus , a full-bridge inverter circuit composed of thyristors D2 to D5 and the power grid E1. Among them, the output voltage of the flyback converter, the bus capacitor C bus The absolute value of the voltage of the transformer is equal to the grid voltage. s The high-frequency components in are filtered by the grid inductance Lg.

[0045] Please continue to refer to Figure 1. When the power switch S1 is turned on, the primary side current i p Starts to rise linearly. Once the primary side current i p Rising to the peak current I of the primary side of the flyback converter pp , the power switch S1 is turned off. The magnetizing inductance of transformer T1 is L m , the supply voltage of power supply P1 is expressed as V pv , according to the inductor current equation, the on-time of the power switch S1 is T on The following formula (1) is satisfied.

[0046] 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 primary side magnetizing inductance is transferred to the secondary side through the transformer T1, and the secondary current i s Linearly decreases, the secondary voltage of the transformer is equal to the grid voltage v grid The absolute value of .

[0047] Let the transformer turns ratio be N sp , the secondary current i of diode D1 s The time required to fall to zero is T f The following formula (2) is satisfied.

[0048] Ideally, in order to reduce total harmonic distortion, the grid current Ix ird It is a sinusoidal curve and has the same phase angle θ as the grid voltage grid In a single switching cycle T of the power switch S1 sw The average value of the secondary side diode current should be equal to the instantaneous value of the grid current.

[0049] The instantaneous value of the grid current |i grid |Satisfies the following formula (3).

[0050] Furthermore, the flyback converter includes a critical conduction mode and a discontinuous conduction mode. FIG2 is a schematic diagram of the critical conduction mode. As shown in FIG2 , in the critical conduction mode, the power switch S1 is s Figure 3 is a schematic diagram of the discontinuous conduction mode. As shown in Figure 3, in the discontinuous conduction mode, the power switch S1 is turned on immediately when the transformer secondary current i s After it drops to 0, it will be opened again after a certain dead time.

[0051] In Figures 2 and 3, T on Indicates the on-time of the power switch S1, T off Indicates the turn-off time of the power switch S1, T f Indicates the fall time of the power switch S1, which is used to indicate the transformer secondary current i s The time required for the power to fall to 0. The dead time is equal to the off time T off . V GS Represents the gate-source voltage of the power switch S1. The peak current I pp and the peak current I sp All are represented by dotted lines.

[0052] It should be noted that the conduction time T is determined in formula (1) and formula (2) onand fall time T f The method is applicable to critical conduction mode and discontinuous conduction mode, that is, as long as the peak current I pp If it is determined, the conduction time T on and fall time T f It can be confirmed.

[0053] The following is an introduction using the critical conduction model as an example. In the critical conduction mode, once the transformer secondary current i s When the power switch S1 is turned on immediately, the off time of the power switch S1 is T off Equal to the fall time T f The switching period T of the power switch S1 in critical conduction mode swBCM It can be expressed as the following formula (4).

[0054] Combining equations (1)(2)(3)(4), we can determine the peak current I of the primary side in critical conduction mode. ppBCM As shown in formula (5).

[0055] Among them, P ref is the grid-connected power reference value, that is, the effective power of the grid, P ref The peak value of the grid voltage V m and the peak value of the grid current I m Determine as follows (6).

[0056] Combining formulas (1)(2)(4)(5), we can determine the switching frequency f of the power switch S1 in critical conduction mode: swBCM As shown in formula (7).

[0057] According to formula (7), if the flyback converter operates in critical conduction mode, at light load, such as when the grid voltage is near zero, due to sin(θ grid ) is 0, the denominator in formula (7) is very small, so the switching frequency of the power switch S1 will be very high, resulting in a large switching loss of the power switch.

[0058] The following is an introduction using the discontinuous conduction mode as an example. In the discontinuous conduction mode, since the power switch S1 is in the transformer secondary current i s After falling to 0, it will be turned on again after a certain dead time is extended. Therefore, the power switch S1 is turned off for a long time. off Equal to the fall time T f and resonance valley time T d , that is, T off =T f +Td In other words, the dead time includes the fall time T f and resonance valley time T d .

[0059] Furthermore, in the discontinuous conduction mode, the switching period T of the power switch S1 is swDCM It can be expressed as the following formula (8).

[0060] If the flyback converter operates in discontinuous conduction mode with a fixed switching frequency f const Operation, the switching period of the power switch S1 is T const As shown in formula (9).

[0061] Combining equations (1)(2)(3)(8)(9), we can determine the peak current I in the discontinuous conduction mode with a fixed frequency. pp As shown in the following formula (10).

[0062] According to formula (10), if the flyback converter operates in discontinuous conduction mode with a fixed frequency, when the load is heavy, such as when the grid voltage is at its peak, due to sin(θ grid ) is 1, the peak current I pp will be very high and the current stress on the power switch S1 may increase to unacceptable levels.

[0063] Therefore, it can be seen that the existing switching frequency control method has the problem of low security. Therefore, it is necessary to provide a switching frequency control method to address the above technical problems. The following will introduce the switching frequency control method.

[0064] FIG4 is an application environment diagram 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, tablet computers, and portable wearable devices. The portable wearable devices may be smart watches, smart bracelets, head-mounted devices, etc. Of course, the controller 401 may also include, but is not limited to, at least one of a central processing unit (CPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), or other programmable logic devices.

[0065] Figure 5 is a flow chart of a grid-connected control method for a flyback converter in an embodiment of the present application. In an exemplary embodiment, as shown in Figure 5 , a grid-connected control method for a flyback converter is provided, which is described by taking the method applied to the controller in Figure 4 as an example, and includes the following S501 to S503.

[0066] S501 , obtaining grid-connected parameters of a flyback converter, and a frequency upper limit and a frequency lower limit of a power switch in the flyback converter.

[0067] In this embodiment, the upper limit of the switching frequency f max and the switching frequency lower limit f min The value can be pre-set and stored in the controller, or sent to the controller by other devices, or input by the user, and this embodiment is not limited thereto. max Used to limit the maximum switching frequency of the power switch S1, the switching frequency lower limit f min Used to limit the minimum switching frequency of the power switch S1.

[0068] In some embodiments, the upper switching frequency limit f max and the switching frequency lower limit f min It is usually determined by the hardware such as power semiconductors and transformers in the flyback converter.

[0069] Grid-connected parameters refer to the power parameters in the flyback converter. Grid-connected parameters may include the power parameters corresponding to the flyback converter during application. For example, grid-connected parameters may include the power supply voltage V pv , the magnetizing inductance L of the transformer in the flyback converter m , the peak current I of the primary side of the flyback converter pp , the phase angle θ of the grid voltage grid wait.

[0070] Optionally, the controller may obtain the grid-connected parameters from the flyback converter through a sensor, or may receive the grid-connected parameters sent by other devices or input by users.

[0071] S502: Determine the number of resonance valleys of the power switch according to the grid connection parameters, the upper frequency limit, and the lower frequency limit.

[0072] Please continue to refer to Figure 1. When the power switch S1 is closed and the transformer secondary current i s After decreasing to zero, the magnetizing inductance L of transformer T1 m and the parasitic capacitance C of the power switch S1 oss A resonant energy storage circuit will be formed. The resonant energy storage energy is in the excitation inductance L m and parasitic capacitance C ossUntil the next time the power switch S1 is turned on. During this period, due to the impedance in the resonant loop, the drain-source voltage V DS Oscillates with a sinusoidal damped waveform, and the corresponding resonant period of oscillation is T r As shown in formula (10).

[0073] Furthermore, when the drain-source voltage V DS When the primary side current i p The drain-source voltage V DS At the bottom of the valley, the primary side current i p Therefore, if the drain-source voltage V DS Turning on the power switch S1 at the bottom of the valley can make the instantaneous current zero and the voltage minimum at the moment of opening, so as to minimize the single switching loss. Among them, the valley is a resonant period T r The point corresponding to the minimum value of the resonant voltage.

[0074] Furthermore, due to the resonance period T r It can affect the single switching cycle of the power switch S1, thereby affecting the switching frequency f of the power switch S1. sw Therefore, in this embodiment, the controller can control the number m of resonance valleys of the power switch S1 and control the switching frequency of the power switch by adjusting the number m of resonance valleys.

[0075] Among them, there are n resonance periods T in the number m of resonance valleys. r , n is the number of resonant cycles, and the relationship between n and m is n = m - 1. That is, when n = 0, the number of resonant valleys m = 1; when n = 1, the number of resonant valleys m = 2; and when n = 2, the number of resonant valleys m = 3. It can be understood that the number of resonant cycles is a natural number.

[0076] Optionally, the controller may calculate the number of resonance valleys of the power switch S1 when the switching frequency of the power switch S1 is not greater than the upper frequency limit and not less than the lower frequency limit according to the grid-connected parameters of the flyback converter.

[0077] In some embodiments, the controller can pre-calculate and store a mapping relationship between different grid-connected parameters and different numbers of resonance valleys based on the grid-connected parameters, the upper frequency limit, and the lower frequency limit. This mapping relationship indicates the number of resonance valleys corresponding to when the switching frequency of the power switch S1 is not less than the lower frequency limit and not greater than the upper frequency limit when operating with the grid-connected parameters. The controller can then use this mapping relationship to determine the number of resonance valleys of the power switch.

[0078] In an exemplary embodiment, optionally, the above S502 may be implemented in the following manner:

[0079] According to the grid-connected parameters, the upper frequency limit and the lower frequency limit, the number of resonance valleys of the power switch in each control stage is determined.

[0080] First, the controller determines each control phase, each of which has a specific duration. Each control phase can be periodic or aperiodic. The number of resonant valleys in each control phase can vary.

[0081] Optionally, the controller may determine the number m of resonance valleys in each control phase at the start of the control phase. For example, t0 to t1 is control phase 1, t1 to t2 is control phase 2, and t2 to t3 is control phase 3. The controller may determine the number m0 of resonance valleys at t0, the number m1 of resonance valleys at t1, the number m2 of resonance valleys at t2, and so on.

[0082] Furthermore, the controller can adjust the switching frequency based on the grid parameters and the upper limit of the switching frequency f max and the switching frequency lower limit f min , determining the number of resonance valleys for the power switch S1 in each control phase. For example, at the start of each control phase, the controller may determine, based on the grid-connected parameters at the start, the number of resonance valleys for the power switch S1 so that the switching frequency of the power switch S1 is not greater than the upper frequency limit and not less than the lower frequency limit.

[0083] Since the number of resonance valleys of the power switch in each control stage can be determined according to the grid connection parameters, the upper frequency limit and the lower frequency limit, the number of resonance valleys can be determined efficiently and accurately using each control stage.

[0084] S503 : Obtain the switching frequency of the power switch according to the grid connection parameters and the number of resonance valleys.

[0085] Optionally, after determining the number of resonance valleys of the power switch S1, the controller may determine the resonance valley time T of the power switch S1 according to the number of resonance valleys. d , and determine the conduction time T according to the grid parameters on and fall time T f , and T on +T f +T d The reciprocal of is used as the switching frequency of the power switch S1.

[0086] In an exemplary embodiment, based on determining the number of resonance valleys of the power switch in each control stage, the above-mentioned S503 may optionally be implemented in the following manner:

[0087] According to the grid-connected parameters and the number of resonance valleys in each control stage, the switching frequency of the power switch in each control stage is obtained.

[0088] Continuing with the above example, the controller can determine the switching frequency of the power switch S1 from t0 to t1 based on the number of resonance valleys m0 and the grid-connected parameters, determine the switching frequency of the power switch S1 from t1 to t2 based on the number of resonance valleys m1 and the grid-connected parameters, determine the switching frequency of the power switch S1 from t2 to t3 based on the number of resonance valleys m2 and the grid-connected parameters, and so on.

[0089] It is understandable that, since some parameters of the grid-connected parameters may change over time, when the number of resonance valleys is constant, the switching frequency of the power switch at different times in the same control phase may also change.

[0090] Since the switching frequency of the power switch in each control stage is determined efficiently and accurately based on the number of resonance valleys according to the grid connection parameters and the number of resonance valleys in each control stage, the switching frequency of the power switch in each control stage can be determined efficiently and accurately based on the number of resonance valleys.

[0091] S504: Control the power switch according to the switching frequency.

[0092] Furthermore, after determining the switching frequency of power switch S1, power switch S1 can be controlled based on the switching frequency. In other words, the controller can control power switch S1 to switch on and off based on the switching frequency determined in S503. It is understood that after controlling power switch S1 based on the switching frequency, the switching frequency of power switch S1 can be no less than the lower switching frequency limit and no greater than the upper switching frequency limit.

[0093] In the above-described flyback converter grid-connected control method, the flyback converter grid-connected parameters and the upper and lower frequency limits of the power switch in the flyback converter are obtained, and the number of resonance valleys of the power switch is determined based on the grid-connected parameters, the upper and lower frequency limits. Therefore, after obtaining the switching frequency of the power switch based on the grid-connected parameters and the number of resonance valleys, the power switch can be controlled based on the switching frequency. Furthermore, because the number of resonance valleys is determined based on the upper and lower frequency limits, the determined switching frequency can be no less than the lower switching frequency limit and no greater than the upper switching frequency limit. This solves the problem of high switching losses caused by excessively high switching frequencies in the prior art. Furthermore, the flyback converter operates at a variable switching frequency, which does not cause significant current stress and improves safety.

[0094] Figure 6 is a flowchart of determining the switching frequency in an embodiment of the present application. In an exemplary embodiment, as shown in Figure 6, the above-mentioned "obtaining the switching frequency of the power switch in each control stage based on the grid-connected parameters and the number of resonance valleys in each control stage" includes S601 to S602.

[0095] S601 : For each control stage, determine the resonance valley time of the current control stage according to the number of resonance valleys in the current control stage.

[0096] In this embodiment, the resonance valley time T d The resonant period T r It is expressed as the following formula (12). It can be seen that the number of resonance cycles n is different, and the number of resonance valleys m is different. The resonance valley time T of the power switch S1 is d It will also be different.

[0097] Then, the controller can determine the resonance valley time of the current control stage according to the number of resonance valleys in the current control stage. Taking control stage 1 as an example, assuming m0 = 8, the controller can determine the resonance valley time T of the power switch S1 according to the number of resonance valleys m0. d =(7+1 / 2)T r .

[0098] S602 : For each control stage, based on the resonance valley time and grid-connected parameters of the current control stage, obtain the switching frequency of the power switch in the current control stage.

[0099] Continuing with the above example, the controller determines the resonance valley time T of control phase 1 d After that, the resonance valley time T of the control stage 1 can be used to d and grid-connected parameters, calculate the switching frequency of the power switch S1 in control phase 1.

[0100] It is understandable that the control phase may include at least one switching frequency corresponding to a moment. For example, the control phase 1 includes moments 1 to 5, and according to the resonance valley time T d The grid-connected parameters corresponding to time 1 can determine the switching frequency at time 1. According to the resonance valley time T d The grid-connected parameters corresponding to time 2 can determine the switching frequency at time 2, ... According to the resonance valley time T d The grid-connected parameters corresponding to time 5 can determine the switching frequency at time 5, and so on.

[0101] The same applies to other control stages, which will not be described in detail below.

[0102] In the above embodiment, since the resonance valley time of the current control stage can be determined according to the number of resonance valleys in the current control stage for each control stage, and the switching frequency of the power switch in the current control stage can be obtained based on the resonance valley time and the grid-connected parameters of the current control stage, the switching frequency of the power switch can be controlled by the resonance valley time, and the switching frequency is made not less than the lower limit of the switching frequency and not greater than the upper limit of the switching frequency, thereby improving the control efficiency and accuracy.

[0103] Figure 7 is another flowchart of determining the switching frequency in an embodiment of the present application. In an exemplary embodiment, as shown in Figure 7, the above-mentioned S602 of "obtaining the switching frequency of the power switch in the current control stage based on the resonant valley time and grid-connected parameters in the current control stage" includes S701 to S702.

[0104] S701, determining the on-time and the fall-time of the current control phase according to the grid-connected parameters.

[0105] In this embodiment, according to formula (1) and formula (2), it can be seen that after the grid-connected parameters are determined, the on-time T of the power switch S1 can be determined. on and fall time T f Therefore, the controller can use equations (1) and (2) to determine the conduction time T of the power switch S1 in the current control stage according to the grid-connected parameters. on and fall time T f .

[0106] Similarly, the on-time and fall-off time of the current control phase will change with the grid-connected parameters. For example, the on-time T corresponding to time 1 in control phase 1 is on The conduction time T corresponding to time 2 on May be different.

[0107] S702 , obtaining a switching frequency of the power switch in the current control phase according to the on-time, the fall-off time, and the resonance valley time in the current control phase.

[0108] Continuing with the control phase 1 as an example, the controller can determine the on-time T in the control phase 1 on , Fall time T f and resonance valley time T d The sum of T on +T f +T d , and T on +T f +T d The reciprocal of is used as the switching frequency of the power switch S1 in control phase 1.

[0109] FIG8 is a schematic diagram of the principle of a valley switch in an embodiment of the present application. As shown in FIG8 , the peak current I pp If the on-time T of the power switch S1 is determined, the on-time T of the power switch S1 can be determined. on and fall time T f , and then the resonance valley time T of the power switch S1 can be controlled by adjusting the resonance valley number m of the power switch d , to control the single switching cycle of the power switch S1, thereby controlling the switching frequency of the power switch S1. For the sake of convenience, the number of resonance valleys m below is represented by the number of resonance cycles n. For example, in Figure 8, the resonance valley time T when the number of resonance cycles n = 2 d >Resonance valley time T when the number of resonance cycles n = 1 d >Resonance valley time T when the number of resonance cycles n = 0 d .

[0110] In the above embodiment, the on-time and fall-off time of the current control stage are determined based on the grid-connected parameters, and the switching frequency of the power switch in the current control stage is obtained based on the on-time, fall-off time and resonance valley time of the current control stage. In this way, the switching frequency of the power switch in the current control stage is obtained based on the resonance valley time and grid-connected parameters of the current control stage, thereby improving the control efficiency of the switching frequency.

[0111] In an exemplary embodiment, the above-mentioned “obtaining the switching frequency of the power switch in each control stage according to the grid-connected parameters and the number of resonance valleys in each control stage” can also be implemented as follows:

[0112] Using the first objective formula, according to the number of resonance valleys in the current control phase and the grid-connected parameters, the switching frequency of the power switch in the current control phase is obtained;

[0113] The first objective formula is:

[0114] Among them, the grid-connected parameters include L m , I pp 、P ref ,θ grid 、V pv 、V m 、N sp and C oss ;

[0115] f sw Indicates the switching frequency, L m Represents the magnetizing inductance of the transformer in the flyback converter, I ppRepresents the peak current of the primary side of the flyback converter, n represents the number of resonant cycles of the flyback converter, n = m-1, m represents the number of resonant valleys, C1 = P ref sin 2 (θ grid ), P ref represents the effective power of the grid connected to the flyback converter, θ grid Represents the phase angle of the grid voltage of the power grid, V pv Represents the supply voltage of the flyback converter, V m Indicates the peak value of the grid voltage, N sp Indicates the turns ratio of the transformer in the flyback converter, C oss Represents the parasitic capacitance of the power switch.

[0116] In this embodiment, by combining equations (1), (2), (3), (8), and (12), we can obtain the following equation (13).

[0117] C1, C2, and C3 in formula (13) satisfy the following formula (14).

[0118] Furthermore, the switching frequency f of the power switch S1 can be determined by combining equations (1), (2), (8), and (13). sw As shown in formula (15).

[0119] Among them, formula (15) is also the first target formula, which establishes the switching frequency f sw The number of resonant cycles n and peak current I pp In other words, the first objective formula is equivalent to establishing the switching frequency f sw The number of resonance valleys m and peak current I pp Therefore, through the first target formula, the switching frequency of the power switch in the current control stage can be controlled according to the number of resonance valleys of the power switch and the grid-connected parameters in the current control stage. For example, in control stage 1, n=m0-1 in formula (15) is used to determine the switching frequency f of the power switch S1 in control stage 1. sw .

[0120] In the above embodiment, since the first target formula can be used to obtain the switching frequency of the power switch in the current control stage according to the number of resonance valleys and the grid-connected parameters in the current control stage, the efficiency of determining the switching frequency is improved.

[0121] Figure 9 is a flow chart of determining the number of resonance valleys in an embodiment of the present application. In an exemplary embodiment, as shown in Figure 9, the above-mentioned "determining the number of resonance valleys of the power switch in each control stage based on the grid-connected parameters, the upper frequency limit and the lower frequency limit" includes S901 to S902.

[0122] S901 : When the grid voltage is at a zero-crossing point, determine the number of multiple candidate resonance valleys according to grid connection parameters, an upper frequency limit, and a lower frequency limit.

[0123] Optionally, when the grid voltage is at a zero-crossing point, the controller can determine θ based on equation (15): grid =0°, and the switching frequency f sw Not less than the lower limit of switching frequency f min And not greater than the upper limit of switching frequency f max The number of multiple candidate resonance valleys.

[0124] S902 : Determine, from the candidate resonance valley numbers, the number of resonance valleys in the control phase corresponding to when the grid voltage is at a zero-crossing point.

[0125] After determining multiple candidate resonance valley numbers, the controller can determine, from the candidate resonance valley numbers, the number m0 of resonance valleys in the first control phase when the voltage crosses zero. For example, if the candidate resonance valley numbers are 8, 7, 6, 5, 4, and 3, respectively, the computer device can determine that the number of resonance valleys in control phase 1 can be any of 8, 7, 6, 5, 4, and 3.

[0126] In some embodiments, since the grid current is also very small when the grid voltage is near the zero crossing point, in order to reduce the switching frequency f by extending the dead time sw , thereby reducing the switching loss at light load, the controller can use the largest number of resonance valleys among the candidate resonance valley numbers as the number of resonance valleys in the first control stage.

[0127] In the above embodiment, when the grid voltage is at a zero-crossing point, multiple candidate resonance valley numbers are determined based on the grid-connected parameters, the upper frequency limit, and the lower frequency limit. The number of resonance valleys in the control phase corresponding to the grid voltage at a zero-crossing point is determined from each candidate resonance valley number. Therefore, when the grid voltage is at a zero-crossing point, the multiple candidate resonance valley numbers determined can ensure that the switching frequency of the power switch is not less than the lower switching frequency limit and not greater than the upper switching frequency limit, eliminating the problem of high switching losses in the prior art caused by excessively high switching frequencies.

[0128] In an exemplary embodiment, optionally, the step of “determining the number of multiple candidate resonance valleys according to the grid connection parameters, the upper frequency limit, and the lower frequency limit” in S901 above can be implemented as follows:

[0129] Using the second objective formula, the number of multiple candidate resonance valleys is determined according to the grid connection parameters, the upper frequency limit, and the lower frequency limit;

[0130] The second objective formula is:

[0131] In this embodiment, based on formula (15), it can be determined that the grid voltage is at the zero-crossing point, that is, θ grid When it approaches 0, the switching frequency f of the power switch S1 sw As shown in formula (16).

[0132] For example, at t0, the grid voltage is at a zero-crossing point. Then, at t0, the controller sets f min <Formula (16)<f max By solving the problem, the number of candidate resonance valleys can be determined.

[0133] Further optionally, after obtaining the number of candidate resonant valleys based on the solution of formula (16), the controller can take the smallest positive integer among the number of candidate resonant valleys as the number of resonant valleys in the control stage corresponding to when the grid voltage is at the zero crossing point.

[0134] In the above embodiment, since the second target formula can be used to determine the number of candidate resonance valleys according to the grid connection parameters, the upper frequency limit, and the lower frequency limit, the efficiency of determining the number of candidate resonance valleys is improved.

[0135] Figure 10 is a flow chart of a method for controlling the switching frequency in an embodiment of the present application. In an exemplary embodiment, as shown in Figure 10 , the above-mentioned "determining the number of resonant valleys of the power switch in each control stage based on the grid-connected parameters, the upper frequency limit, and the lower frequency limit" includes S1001 to S1002.

[0136] S1001 , determining a switching frequency in a current control phase according to the number of resonance valleys in a previous control phase.

[0137] In this embodiment, combined with formula (15), it can be seen that when the number of resonance valleys is constant, as sin(θ grid ) increases, the switching frequency f of the power switch S1 sw Will gradually decrease, therefore, in order to make the switching frequency f of the power switch S1 sw Not less than the lower limit of switching frequency f min And not greater than the upper limit of switching frequency f maxThe controller determines the switching frequency of the current control stage based on the number of resonance valleys in the previous control stage. Alternatively, the controller can determine the switching frequency of the current control stage based on the grid-connected parameters of the current control stage.

[0138] For example, the controller calculates the number of resonance valleys in control stage 1 as m0 at time t0 , and for control stage 2 , the controller may continue to determine the switching frequency of control stage 2 according to the number of resonance valleys m0 in control stage 1 .

[0139] S1002: If the switching frequency of the current control stage is less than the frequency lower limit or greater than the frequency upper limit, the number of resonance valleys of the previous control stage is adjusted to obtain the number of resonance valleys of the current control stage.

[0140] In this embodiment, when the switching frequency of the current control stage is less than the frequency lower limit or greater than the frequency upper limit, it means that if the number of resonance valleys of the previous control stage is used, the switching frequency of the current control stage will not meet the requirements. Therefore, in order to make the switching frequency of the current control stage not less than the frequency lower limit and not greater than the frequency upper limit, the controller will adjust the number of resonance valleys of the previous control stage to obtain the number of resonance valleys of the current control stage.

[0141] Optionally, the controller can increase or decrease the number of resonance valleys of the previous control stage with a certain compensation until the switching frequency is calculated based on the adjusted number of resonance valleys to be not less than the lower frequency limit and not greater than the upper frequency limit, and the adjusted number of resonance valleys can be used as the number of resonance valleys of the current control stage.

[0142] It should be noted that the switching frequency in the current control phase is less than the frequency lower limit or greater than the frequency upper limit, including: the switching frequency is less than the frequency lower limit or greater than the frequency upper limit at any moment in the current control phase.

[0143] S1003: If the switching frequency of the current control stage is not less than the frequency lower limit and not greater than the frequency upper limit, the number of resonance valleys of the previous control stage is used as the number of resonance valleys of the current control stage.

[0144] In this embodiment, if the switching frequency of the current control stage is not less than the lower frequency limit and not greater than the upper frequency limit, then the number of resonance valleys of the previous control stage can be continued to be used, so that the switching frequency of the current control stage is not less than the lower frequency limit and not greater than the upper frequency limit. Therefore, in order to ensure that the switching frequency of the current control stage is not less than the lower frequency limit and not greater than the upper frequency limit, the number of resonance valleys of the previous control stage can be used as the number of resonance valleys of the current control stage.

[0145] It should be noted that the switching frequency in the current control stage is not less than the frequency lower limit and not greater than the frequency upper limit, including: the switching frequency at each moment in the current control stage is not less than the frequency lower limit and not greater than the frequency upper limit.

[0146] FIG11 is a schematic diagram of a control process in an embodiment of the present application. The upper diagram in FIG11 shows the peak current I of the primary side of the flyback converter. pp As for the situation changing over time, the lower diagram in FIG11 shows the situation that the switching frequency of the power switch S1 changes over time.

[0147] Continuing with the above example, t0 is the grid voltage zero crossing point. At t0, the controller sets f min <Formula (16)<f max The solution is performed and it is determined that the number of resonance valleys m0 in the control phase 1 is 8, and the number of resonance periods n0 is 7.

[0148] In the process of t0~t1, due to sin(θ grid ) increases, the switching frequency f of the power switch S1 sw Will gradually decrease. At t1, if the operation continues with the number of resonance valleys m0 = 8, the switching frequency f of the power switch S1 sw <Switching frequency lower limit f min , the controller reduces m0 to obtain m1 at time t1, for example, m1=m0-2=6, and the number of resonant cycles n1=5.

[0149] In the process of t1 to t2, due to sin(θ grid ) increases, the switching frequency f of the power switch S1 sw Will gradually decrease. At t2, if the operation continues with the number of resonance valleys m1 = 6, the switching frequency f of the power switch S1 sw <Switching frequency lower limit f min , the controller reduces m1 to obtain m2 at time t2, for example, m2=m1-2=4, at which time the number of resonant cycles n2=3, and so on.

[0150] It should be noted that the above example uses a reduction of 2 each time. When adjusting the number of resonance valleys in the previous control stage, different values ​​may be reduced each time. This embodiment is not limited thereto.

[0151] In the above embodiment, the switching frequency of the current control stage is determined based on the number of resonance valleys in the previous control stage. If the switching frequency of the current control stage is less than the lower frequency limit or greater 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. If the switching frequency of the current control stage is not less than the lower frequency limit and not greater 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 ensured to be neither less than the lower frequency limit nor greater than the upper frequency limit, thereby improving safety.

[0152] In an exemplary embodiment, optionally, the step of “adjusting the number of resonance valleys in the previous control stage to obtain the number of resonance valleys in the current control stage” in S902 can be implemented as follows:

[0153] If the phase angle θ grid If it is located at [k×180°, k×180°+90°], the number of resonance valleys in the current control stage is reduced to determine the number of resonance valleys in the next control stage.

[0154] If the phase angle θ grid If it is not located at [k×180°, k×180°+90°], the number of resonance valleys in the current control stage is increased to determine the number of resonance valleys in the next control stage.

[0155] In this embodiment, k is a natural number, and the phase angle θ of the grid voltage is grid Usually it changes sinusoidally, the peak current I pp Refer to Figure 11, it can be seen that taking a 360° as an example, at the phase angle θ grid When the angle 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 and phase angle θ grid Change in the same direction, on the contrary, the peak current I pp and phase angle θ grid Reverse change.

[0156] At the peak current I pp and phase angle θ grid In the case of same direction change, the switching frequency f of power switch S1 sw It will gradually decrease, so it is necessary to reduce the number of resonance valleys to shorten the resonance valley time T of the power switch. d , thereby increasing the switching frequency f of the power switch S1 sw . Then, at the phase angle θ gridWhen the angle is [k×180°, k×180°+90°], the controller reduces the number of resonance valleys in the current control phase to determine the number of resonance valleys in the next control phase. The number of resonance valleys in the previous control phase may be reduced by a first preset value.

[0157] At the peak current I pp and phase angle θ grid In the case of reverse change, the switching frequency f of the power switch S1 sw It will gradually increase, so it is necessary to increase the number of resonance valleys to increase the resonance valley time T of the power switch. d , thereby reducing the switching frequency f of the power switch S1 sw . Then, at the phase angle θ grid If the angle is not [k×180°, k×180°+90°], the controller increases the number of resonance valleys in the current control phase to determine the number of resonance valleys in the next control phase. The number of resonance valleys in the previous control phase may be increased by a second preset value.

[0158] In the above embodiment, k is a natural number, and the power grid is connected to the flyback converter. When the phase angle of the power grid voltage is between [k×180°, k×180°+90°], the number of resonance valleys in the current control phase is reduced to determine the number of resonance valleys in the next control phase. When the phase angle is not between [k×180°, k×180°+90°], the number of resonance valleys in the current control phase is increased to determine the number of resonance valleys in the next control phase. Therefore, by adjusting the number of resonance valleys in the previous control phase to obtain the number of resonance valleys in the current control phase, the number of resonance valleys in the current control phase can be made not less than the lower frequency limit and not greater than the upper frequency limit.

[0159] FIG12 is a flowchart of another method for determining a switching frequency in an embodiment of the present application. In an exemplary embodiment, as shown in FIG12 , the above-mentioned grid-connected control method of the flyback converter further includes S1201 to S1202 .

[0160] S1201, determining the switching frequency of the power switch within a preset period according to the switching frequency of the power switch; the preset period is a preset multiple of the power frequency period.

[0161] In this embodiment, the power frequency refers to the frequency of the mains electricity. Taking 50 Hz as an example, the power frequency period can be 0.02 seconds. The preset multiple can be any number greater than 0, such as 1 / 2 or 1 / 4, or 1 or 2.

[0162] Taking 1 / 4 of the power frequency cycle as an example, please continue to refer to Figure 11. Continuing the above example, the controller executes according to the above process. During the process of t3 to t4, due to sin(θ grid ) increases, the switching frequency f of the power switch S1 sw Will gradually decrease. At t4, if the operation continues with the resonance valley number m3, the switching frequency f of the power switch S1 sw <Switching frequency lower limit f min , the controller reduces n3 to get n4 at time t4, and operates based on the number of resonance valleys m4 during t4 to t5 until θ grid =90°, sin(θ grid )=1, at this time, the number of resonance valleys in the current control stage is the smallest. In this way, the 1 / 4 power frequency cycle adjustment is completed.

[0163] S1202 : Determine the switching frequency of the power switch in each control phase according to the switching frequency of the power switch in a preset period.

[0164] Continuing with the above example, since the switching frequency of the power switch within 1 / 4 of the power frequency cycle is determined, and the power frequency cycle has regularity, the switching frequency of the power switch in each control stage can be determined based on the switching frequency of the power switch within the preset cycle. For example, the switching frequency of the power switch at the phase angle θ can be determined by symmetry, replication, etc. grid The switching frequency within each control phase in 360°.

[0165] Please continue to refer to Figure 11, the controller can adjust the phase angle θ grid The switching frequency of the power switch in the first 1 / 4 power frequency cycle is symmetrically processed to obtain the phase angle θ grid The switching frequency of the power switch when the angle is between 90° and 180°.

[0166] Furthermore, the controller can replicate the phase angle θ grid The switching frequency of the power switch in the first 1 / 2 power frequency cycle is copied to obtain the phase angle θ. grid The switching frequency of the power switch when the angle is between 180° and 360°.

[0167] In the above embodiment, the preset period is a preset multiple of the power frequency period. Since the switching frequency of the power switch within the preset period can be determined based on the switching frequency of the power switch, and the switching frequency of the power switch in each control stage can be determined based on the switching frequency of the power switch within the preset period, the switching frequency of the power switch in each control stage can be determined efficiently and accurately.

[0168] FIG13 is a process diagram of a grid-connected control method for a flyback converter according to an embodiment of the present application. In an exemplary embodiment, the controller may execute the method according to the following process.

[0169] S1301: Obtain grid-connected parameters of the flyback converter, and an upper frequency limit and a lower frequency limit of a power switch in the flyback converter.

[0170] S1302: When the grid voltage is at a zero-crossing point, determine the number of multiple candidate resonance valleys using a second target formula according to grid connection parameters, an upper frequency limit, and a lower frequency limit.

[0171] S1303: Determine the number of resonance valleys in the control phase corresponding to when the grid voltage is at a zero-crossing point from the number of candidate resonance valleys.

[0172] S1304: Determine the switching frequency of the current control stage according to the number of resonance valleys in the previous control stage.

[0173] S1305: If the switching frequency of the current control stage is less than the frequency lower limit or greater than the frequency upper limit, the number of resonance valleys of the previous control stage is adjusted to obtain the number of resonance valleys of the current control stage.

[0174] S1306: If the switching frequency of the current control stage is not less than the frequency lower limit and not greater than the frequency upper limit, the number of resonance valleys of the previous control stage is used as the number of resonance valleys of the current control stage.

[0175] S1307 , using the first target formula, according to the number of resonance valleys in the current control phase and the grid-connected parameters, obtain the switching frequency of the power switch in the current control phase.

[0176] S1308 : Determine the switching frequency of the power switch within a preset period according to the switching frequency of the power switch.

[0177] S1309 , determining the switching frequency of the power switch in each control stage according to the switching frequency of the power switch in a preset period.

[0178] S1310, controlling the power switch according to the switching frequency.

[0179] Steps S1301 to S1310 can be referred to in the above embodiment and will not be repeated here. This embodiment provides an efficiency optimization control method for an extended soft switching range based on a flyback converter. Based on the mathematical model of the flyback converter's multi-valley switching, the calculation process and control method for the peak current reference and switching frequency used for switch control are provided. The flyback converter operates in discontinuous conduction mode, and the number of valleys when the power switch is turned on is calculated based on the grid-connected power and the preset switching frequency range.

[0180] Table 1 provides simulation parameters for a flyback converter. The power switch frequency was simulated and verified using the parameters in Table 1. To adjust the switching frequency of power switch S1 between an upper limit of 250 kHz and a lower limit of 190 kHz, n = 7 and m = 8 are calculated at the grid voltage zero crossing point according to Equation (16). As the instantaneous power increases, when the switching frequency calculated by Equation (15) reaches 190 kHz, n switches to 4 and m to 5. Then, when the switching frequency reaches the lower limit of 190 kHz, n switches to 2, 1, and 0, respectively, and so on.

[0181] Table 1 Simulation parameters

[0182] FIG14 is a simulation effect diagram of an embodiment of the present application. FIG14 (a) to FIG14 (e) respectively show the driving signal of the power switch S1 and the drain-source voltage V of the power switch S1 under different numbers of resonance cycles n, that is, different numbers of resonance valleys m. DS It can be understood that the waveforms in the upper part of Figure 14 (a) to Figure 14 (e) are schematic waveforms of the driving signal, and the waveforms in the lower part of Figure 14 (a) to Figure 14 (e) are schematic waveforms of the drain-source voltage V DS As shown in FIG14 , according to the control method of this embodiment, valley switching in the resonance period is achieved under all different load conditions of n=0, 1, 2, 4, and 7.

[0183] FIG15 is a schematic diagram of an electric power parameter in an embodiment of the present application, FIG15 shows the grid voltage, grid current and transformer secondary current i of the flyback converter. s The principle revealed by formula (3) can also be verified in conjunction with Figure 15.

[0184] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0185] Based on the same inventive concept, embodiments of the present application further provide a flyback converter grid-connected control device for implementing the aforementioned flyback converter grid-connected control method. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of the one or more flyback converter grid-connected control device embodiments provided below can be found in the aforementioned definitions of the flyback converter grid-connected control method, and will not be further elaborated here.

[0186] FIG16 is a structural block diagram of a flyback converter grid-connected control device according to an embodiment of the present application. In an exemplary embodiment, as shown in FIG16 , a flyback converter grid-connected control device 1600 is provided, comprising: a first acquisition module 1601, a first determination module 1602, a second determination module 1603, and a control module 1604, wherein:

[0187] The first acquisition module 1601 is configured to acquire the grid-connected parameters of the flyback converter, and the upper frequency limit and the lower frequency limit of the power switch in the flyback converter.

[0188] The first determining module 1602 is configured to determine the number of resonance valleys of the power switch according to the grid connection parameters, the upper frequency limit, and the lower frequency limit.

[0189] The second determining module 1603 is configured to obtain a switching frequency of the power switch according to the grid connection parameters and the number of resonance valleys.

[0190] The control module 1604 is configured to control the power switch according to the switching frequency.

[0191] In some embodiments, the first determining module is specifically configured to:

[0192] determining the number of resonance valleys of the power switch in each control stage according to the grid-connected parameters, the upper frequency limit, and the lower frequency limit;

[0193] Obtaining the switching frequency of the power switch according to the grid-connected parameters and the number of resonance valleys includes:

[0194] The switching frequency of the power switch in each of the control stages is obtained according to the grid-connected parameters and the number of resonance valleys in each of the control stages.

[0195] In some embodiments, the first determining module is specifically configured to:

[0196] For each of the control stages:

[0197] Determining the resonance valley time of the current control stage according to the number of resonance valleys in the current control stage;

[0198] The switching frequency of the power switch in the current control phase is obtained based on the resonance valley time and the grid-connected parameters in the current control phase.

[0199] In some embodiments, the first determining module is specifically configured to:

[0200] Determining the on-time and the fall-time of the current control phase according to the grid-connected parameters;

[0201] The switching frequency of the power switch in the current control phase is obtained according to the on-time, the fall time, and the resonance valley time in the current control phase.

[0202] In some embodiments, the first determining module is specifically configured to:

[0203] Obtaining a switching frequency of the power switch in the current control phase according to the number of resonance valleys in the current control phase and the grid-connected parameters using a first target formula;

[0204] The first target formula is:

[0205] Among them, the grid connection parameters include L m , I pp 、P ref ,θ grid 、V pv 、V m 、N sp and C oss ;

[0206] f sw represents the switching frequency, L m represents the magnetizing inductance of the transformer in the flyback converter, I pp represents the peak current of the primary side of the flyback converter, n represents the number of resonant cycles of the flyback converter, n=m-1, m represents the number of resonant valleys, C1=P ref sin 2 (θ grid ), P ref represents the effective power of the grid connected to the flyback converter, θ grid represents the phase angle of the grid voltage of the grid, V pv represents the supply voltage of the flyback converter, V m Represents the peak value of the grid voltage, N sp represents the turns ratio of the transformer in the flyback converter, C oss represents the parasitic capacitance of the power switch.

[0207] In some embodiments, the first determining module is specifically configured to:

[0208] When the grid voltage is at a zero-crossing point, determining a number of multiple candidate resonance valleys according to the grid connection parameters, the upper frequency limit, and the lower frequency limit;

[0209] The number of resonance valleys in the control phase corresponding to when the grid voltage is at a zero-crossing point is determined from the number of candidate resonance valleys.

[0210] In some embodiments, the first determining module is specifically configured to:

[0211] Determining the number of the plurality of candidate resonance valleys according to the grid connection parameter, the upper frequency limit, and the lower frequency limit using a second target formula;

[0212] The second target formula is:

[0213] In some embodiments, the first determining module is specifically configured to:

[0214] Determine the switching frequency of the current control stage according to the number of resonance valleys in the previous control stage;

[0215] If the switching frequency of the current control stage is less than the frequency lower limit or greater than the frequency upper limit, adjusting the number of resonance valleys of the previous control stage to obtain the number of resonance valleys of the current control stage;

[0216] If the switching frequency of the current control stage is not less than the frequency lower limit and not greater than the frequency upper limit, the number of resonance valleys of the previous control stage is used as the number of resonance valleys of the current control stage.

[0217] In some embodiments, the apparatus further comprises:

[0218] The third determining module is configured to:

[0219] Determining the switching frequency of the power switch within a preset period according to the switching frequency of the power switch; the preset period is a preset multiple of the power frequency period;

[0220] The switching frequency of the power switch in each of the control stages is determined according to the switching frequency of the power switch in a preset period.

[0221] Each module in the aforementioned flyback converter grid-connected control device may be implemented in whole or in part via software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor in a computer device in the form of hardware, or may be stored in a memory in the computer device in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0222] Figure 17 is a diagram of the internal structure of a computer device in an embodiment of the present application. In an exemplary embodiment, a computer device is provided, which may be a server, and its internal structure may be as shown in Figure 17. The computer device includes a processor, memory, an input / output (I / O) interface, 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 is used to provide computing 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, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store relevant data. The I / O interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals via a network connection. When executed by the processor, the computer program implements a grid-connected control method for a flyback converter.

[0223] Those skilled in the art will understand that the structure shown in Figure 17 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0224] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0225] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0226] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0227] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic 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. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0228] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0229] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A grid-connected control method for a flyback converter, wherein, The method includes: Obtaining grid-connection parameters of a flyback converter, an upper frequency limit and a lower frequency limit of a power switch in the flyback converter; Determining the number of resonant valley bottoms of the power switch according to the grid-connection parameters, the upper frequency limit and the lower frequency limit; Obtaining the switching frequency of the power switch according to the grid-connection parameters and the number of resonant valley bottoms; Controlling the power switch according to the switching frequency.

2. The method according to claim 1, wherein The determining the number of resonant valley bottoms of the power switch according to the grid-connection parameters, the upper frequency limit and the lower frequency limit includes: Determining the number of resonant valley bottoms of the power switch in each control stage according to the grid-connection parameters, the upper frequency limit and the lower frequency limit; The obtaining the switching frequency of the power switch according to the grid-connection parameters and the number of resonant valley bottoms includes: Obtaining the switching frequency of the power switch in each control stage according to the grid-connection parameters and the number of resonant valley bottoms in each control stage.

3. The method according to claim 2, wherein, The obtaining the switching frequency of the power switch in each control stage according to the grid-connection parameters and the number of resonant valley bottoms in each control stage includes: For each control stage: Determining the resonant valley bottom time of the current control stage according to the number of resonant valley bottoms of the current control stage; Obtaining the switching frequency of the power switch in the current control stage based on the resonant valley bottom time of the current control stage and the grid-connection parameters.

4. The method according to claim 3, wherein, The obtaining the switching frequency of the power switch in the current control stage based on the resonant valley bottom time of the current control stage and the grid-connection parameters includes: Determining the conduction time and the falling time of the current control stage according to the grid-connection parameters; Obtaining the switching frequency of the power switch in the current control stage according to the conduction time, the falling time and the resonant valley bottom time of the current control stage.

5. The method according to claim 2, wherein The obtaining the switching frequency of the power switch in each control stage according to the grid-connection parameters and the number of resonant valley bottoms in each control stage includes: Using a first target formula to obtain the switching frequency of the power switch in the current control stage according to the number of resonant valley bottoms of the current control stage and the grid-connection parameters; The first target formula is as follows: Among them, the grid connection parameters include L m , I pp , P ref , θ grid , V pv , V m , N sp and C oss ; f sw represents the switching frequency, L m represents the magnetizing inductance of the transformer in the flyback converter, I pp represents the peak current of the primary side of the flyback converter, n represents the number of resonant cycles of the flyback converter, n = m - 1, m represents the number of resonant valleys, C1 = P ref sin 2 (θ grid ) P ref represents the active power of the power grid connected to the flyback converter, θ grid represents the phase angle of the grid voltage of the power grid, V pv represents the supply of the flyback converter Electric voltage, V m Represents the peak value of the grid voltage, N sp Represents the turns ratio of the transformer in the flyback converter, C oss Represents the parasitic capacitance of the power switch.

6. The method according to claim 5, wherein, The determining the number of resonant valley bottoms of the power switch in each control stage according to the grid-connection parameters, the upper frequency limit and the lower frequency limit includes: In the case where the grid voltage is at the zero crossing point, determining a plurality of candidate numbers of resonant valley bottoms according to the grid-connection parameters, the upper frequency limit and the lower frequency limit; Determining the number of resonant valley bottoms corresponding to the control stage when the grid voltage is at the zero crossing point from each of the candidate numbers of resonant valley bottoms.

7. The method according to claim 6, wherein, The determining a plurality of candidate numbers of resonant valley bottoms according to the grid-connection parameters, the upper frequency limit and the lower frequency limit includes: Using a second target formula to determine the plurality of candidate numbers of resonant valley bottoms according to the grid-connection parameters, the upper frequency limit and the lower frequency limit; The second target formula is as follows:

8. The method according to any one of claims 2-7, wherein The determining the number of resonant valley bottoms of the power switch in each control stage according to the grid-connection parameters, the upper frequency limit and the lower frequency limit includes: Determine the switching frequency of the current control stage according to the number of resonant valley bottoms in the previous control stage; If the switching frequency of the current control stage is less than the lower frequency limit or greater than the upper frequency limit, adjust the number of resonant valley bottoms in the previous control stage to obtain the number of resonant valley bottoms in the current control stage; If the switching frequency of the current control stage is not less than the lower frequency limit and not greater than the upper frequency limit, use the number of resonant valley bottoms in the previous control stage as the number of resonant valley bottoms in the current control stage.

9. The method according to any one of claims 2-7, wherein The method further includes: Determine the switching frequency of the power switch within a preset period according to the switching frequency of the power switch; the preset period is a preset multiple of the power frequency period; Determine the switching frequency of the power switch within each of the control stages according to the switching frequency of the power switch within the preset period.

10. A grid-connected control device for a flyback converter, wherein, The device includes: A first acquisition module, configured to acquire grid connection parameters of a flyback converter, an upper frequency limit and a lower frequency limit of the switching frequency of a power switch in the flyback converter; A first determination module, configured to determine the number of resonant valley bottoms of the power switch according to the grid connection parameters, the upper frequency limit and the lower frequency limit; A second determination module, configured to obtain the switching frequency of the power switch according to the grid connection parameters and the number of resonant valley bottoms; A control module, configured to control the power switch according to the switching frequency.

11. The device according to claim 10, wherein, The first determination module is specifically configured to: Determine the number of resonant valley bottoms of the power switch in each control stage according to the grid connection parameters, the upper frequency limit and the lower frequency limit; The obtaining the switching frequency of the power switch according to the grid connection parameters and the number of resonant valley bottoms includes: Obtain the switching frequency of the power switch in each of the control stages according to the grid connection parameters and the number of resonant valley bottoms in each of the control stages.

12. The apparatus according to claim 11, wherein, The first determination module is specifically configured to: For each of the control stages: Determine the resonant valley time of the current control stage according to the number of resonant valley bottoms of the current control stage; Based on the resonant valley time of the current control stage and the grid connection parameters, obtain the switching frequency of the power switch in the current control stage.

13. The apparatus according to claim 12, wherein, The first determination module is specifically configured to: Determine the conduction time and the falling time of the current control stage according to the grid connection parameters; According to the conduction time of the current control stage, the falling time and the resonant valley time, obtain the switching frequency of the power switch in the current control stage.

14. The device according to claim 11, wherein, The first determination module is specifically configured to: Use a first target formula to obtain the switching frequency of the power switch in the current control stage according to the number of resonant valley bottoms of the current control stage and the grid connection parameters; The first target formula is as follows: Among them, the grid connection parameters include L m , I pp , P ref , θ grid , V pv , V m , N sp and C oss ; f sw represents the switching frequency, L m represents the magnetizing inductance of the transformer in the flyback converter, I pp represents the peak current of the primary side of the flyback converter, n represents the number of resonant periods of the flyback converter, n = m - 1, m represents the number of resonant valleys, C1 = P ref sin 2 (θ grid ) P ref represents the active power of the power grid connected to the flyback converter, θ grid represents the phase angle of the grid voltage of the power grid, V pv represents the supply voltage of the flyback converter, V m represents the peak value of the grid voltage, N sp represents the turns ratio of the transformer in the flyback converter, C oss represents the parasitic capacitance of the power switch.

15. The apparatus according to claim 14, wherein The first determination module is specifically configured to: In the case where the grid voltage is at the zero crossing point, determine a plurality of candidate numbers of resonant valley bottoms according to the grid connection parameters, the upper frequency limit and the lower frequency limit; Determine the number of resonant valley bottoms corresponding to the control stage when the grid voltage is at the zero crossing point from among the candidate numbers of resonant valley bottoms.

16. The device according to claim 15, wherein, The first determination module is specifically configured to: Using a second target formula, determine the number of candidate resonant valleys according to the grid connection parameters, the upper frequency limit, and the lower frequency limit. The second target formula is as follows:

17. The device according to any one of claims 11 - 16, wherein The first determination module is specifically configured to: Determine the switching frequency of the current control stage according to the number of resonant valleys in the previous control stage. If the switching frequency of the current control stage is less than the lower frequency limit or greater than the upper frequency limit, then adjust the number of resonant valleys in the previous Control stage to obtain the number of resonant valleys in the current control stage. If the switching frequency of the current control stage is not less than the lower frequency limit and not greater than the upper frequency limit, then use the number of resonant valleys in the previous control stage as the number of resonant valleys in the current control stage.

18. The device according to any one of claims 11 - 16, wherein, The device further includes: A third determination module, configured to: Determine the switching frequency of the power switch within a preset period according to the switching frequency of the power switch; the preset period is a preset multiple of the power frequency period. Determine the switching frequency of the power switch in each of the control stages according to the switching frequency of the power switch within the preset period.

19. A computer device, comprising a memory and a processor, the memory storing a computer program, wherein, When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

20. A computer-readable storage medium having a computer program stored thereon, wherein, When the computer program is executed by the processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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