Power limiting method, device and grid-connected system for flyback converter

Abstract

The present application relates to a power limiting method, device and grid-connected system for a flyback converter, wherein the method includes: sampling the DC voltage and grid voltage of the flyback converter; calculating the power limiting value based on the DC voltage and the grid voltage; obtaining the maximum output power of a DC battery assembly, the DC battery assembly being connected to the flyback converter; comparing the power limiting value and the maximum output power, and if the maximum output power is greater than the power limiting value, taking the power limiting value as the target output power; generating a modulation signal based on the target output power to control the turn-on time of the switch tube of the flyback converter. Through the present application, it is possible to avoid overcurrent on the primary side of the flyback circuit, realize the control of the output power amplitude, thereby reducing the large energy impact caused by power mutation and improving the stress of components.

Description

Technical Field

[0001] The present application relates to the technical field of flyback converters, and in particular to a power limiting method, device and grid-connected system for a flyback converter. Background Art

[0002] Flyback converter is a switching power supply widely used in AC / DC and DC / DC conversion. It provides insulation isolation between the input stage and the output stage, and has the advantages of simple structure and wide application.

[0003] Power control is an important control function of the flyback converter system. Traditional flyback converter power control methods mostly use PI controllers with good accuracy, which can achieve zero-error tracking. However, it is easy to trigger the primary side overcurrent problem of the flyback circuit under the conditions of grid voltage changes, DC voltage jitter, power factor angle changes, etc., and the control effect is not ideal.

[0004] With respect to the primary side overcurrent problem of the flyback circuit existing in the related art, no effective solution has been proposed yet. Summary of the invention

[0005] In this embodiment, a power limiting method, device and grid-connected system of a flyback converter are provided to solve the problem of primary-side overcurrent in the flyback circuit in the related art.

[0006] In a first aspect, a power limiting method for a flyback converter is provided in this embodiment, and the method includes:

[0007] Sampling the DC voltage and the grid voltage of the flyback converter; calculating the power limit value based on the DC voltage and the grid voltage;

[0008] Obtaining a maximum output power of a DC battery assembly, wherein the DC battery assembly is connected to the flyback converter;

[0009] comparing the power limit value and the maximum output power, and if the maximum output power is greater than the power limit value, taking the power limit value as the target output power;

[0010] A modulation signal is generated based on the target output power to control the turn-on time of the switch tube of the flyback converter.

[0011] In some embodiments, the sampling of the DC voltage and the grid voltage of the flyback converter includes:

[0012] Sampling the initial DC voltage and the initial grid voltage of the flyback converter based on a digital-to-analog converter;

[0013] The initial DC voltage and the initial grid voltage are filtered to obtain a DC voltage and a grid voltage.

[0014] In some embodiments, filtering the initial DC voltage and the initial grid voltage to obtain the DC voltage and the grid voltage includes:

[0015] Based on a sliding window, the initial DC voltage and the initial grid voltage are filtered to obtain a DC voltage and a grid voltage; wherein the sliding window is a power frequency window.

[0016] In some embodiments, the calculating the power limit value based on the DC voltage and the grid voltage includes:

[0017] Obtain preset hardware design parameters and power factor angle;

[0018] A power limit value is calculated based on the hardware design parameters, the power factor angle, the DC voltage, and the grid voltage.

[0019] In some of the embodiments, the hardware design parameters include: primary side peak current and transformer turns.

[0020] In some embodiments, obtaining the maximum output power of the DC battery assembly includes:

[0021] The maximum output power of the DC battery module is calculated based on the perturbation and observation method of maximum power point tracking.

[0022] In some embodiments, before generating a modulation signal based on the target output power to control the on-time of the switch tube of the flyback converter, the method further includes:

[0023] If the maximum output power is not greater than the power limit value, the maximum output power is used as the target output power.

[0024] In a second aspect, a power limiting device for a flyback converter is provided in this embodiment, and the device includes:

[0025] A voltage sampling module, used for sampling the DC voltage and the grid voltage of the flyback converter; and calculating the power limit value based on the DC voltage and the grid voltage;

[0026] A power tracking module, used to obtain the maximum output power of a DC battery assembly, the DC battery assembly being connected to the flyback converter;

[0027] A power comparison module, used for comparing the power limit value with the maximum output power, and if the maximum output power is greater than the power limit value, taking the power limit value as the target output power;

[0028] The flyback operation module is used to generate a modulation signal based on the target output power to control the turn-on time of the switch tube of the flyback converter.

[0029] In a third aspect, the present application further provides a grid-connected system, comprising: a flyback converter, a DC battery assembly and a power grid; the flyback converter comprises a switch tube, a transformer, a first diode and a controller;

[0030] The DC battery assembly is connected to the primary coil of the transformer through the switch tube;

[0031] The secondary coil of the transformer is connected to the power grid through the first diode;

[0032] The controller is connected to the switch tube, and the controller is used to execute the steps of the power limiting method of the flyback converter of the first aspect.

[0033] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the power limiting method of the flyback converter described in the first aspect is implemented.

[0034] Compared with the related art, the power limiting method, device and grid-connected system of the flyback converter provided in this embodiment, by sampling the DC voltage and grid voltage of the flyback converter; calculating the power limiting value based on the DC voltage and the grid voltage; obtaining the maximum output power of a DC battery assembly, which is connected to the flyback converter; comparing the power limiting value and the maximum output power, if the maximum output power is greater than the power limiting value, using the power limiting value as the target output power; generating a modulation signal based on the target output power to control the turn-on time of the switch tube of the flyback converter, which can avoid overcurrent on the primary side of the flyback circuit and achieve control of the output power amplitude, thereby reducing the large energy impact caused by power mutation and improving the stress of components.

[0035] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0037] Figure 1 A hardware structure block diagram of a terminal of a power limiting method for a flyback converter in one embodiment;

[0038] Figure 2 is a schematic flow chart of a power limiting method for a flyback converter in one embodiment;

[0039] Figure 3 A schematic diagram of the structure of a grid-connected system in one embodiment;

[0040] Figure 4 FIG. 4 is a structural block diagram of a power limiting device of a flyback converter in an embodiment.

[0041] Figure numerals: 10, flyback converter; 20, DC battery assembly; 30, power grid; 41, voltage sampling module; 42, power tracking module; 43, power comparison module; 44, flyback operation module. DETAILED DESCRIPTION

[0042] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0043] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with general skills in the technical field to which this application belongs. The words "one", "a", "the", "these" and the like in this application do not indicate a quantitative limitation, and they may be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone. Generally, the character " / " indicates that the objects associated with each other are in an "or" relationship. The terms "first", "second", "third", etc. in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0044] The method embodiment provided in this embodiment can be executed in a terminal, a computer or a similar computing device. For example, running on a terminal, Figure 1 FIG. 1 is a hardware structure block diagram of a terminal of the power limiting method of the flyback converter of this embodiment. Figure 1 As shown, the terminal may include one or more ( Figure 1 Only one is shown in the figure) a processor 102 and a memory 104 for storing data, wherein the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA. The above terminal may also include a transmission device 106 and an input and output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the above terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations shown.

[0045] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the power limiting method of the flyback converter in this embodiment. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, to implement the above method. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories may be connected to the terminal via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0046] The transmission device 106 is used to receive or send data via a network. The above network includes a wireless network provided by the communication provider of the terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (Radio Frequency, referred to as RF) module, which is used to communicate with the Internet wirelessly.

[0047] In this embodiment, a power limiting method for a flyback converter is provided. Figure 2 is a flow chart of the power limiting method of the flyback converter of this embodiment, which can be applied to Figure 3 In the grid-connected system shown, the system includes: a flyback converter 10, a DC battery assembly 20 and a power grid 30; the flyback converter 10 includes a switch tube Q1, a transformer T, a first diode D1 and a controller. The DC battery assembly 20 is connected to the primary coil Lp of the transformer T through the switch tube Q1. The secondary coil Ls of the transformer T is connected to the power grid 30 through the first diode. The controller is connected to the switch tube Q1, and the controller is used to execute the steps of the power limiting method of the flyback converter 10. Its working principle is: when the switch tube Q1 of the flyback converter 10 is turned on, the energy provided by the DC battery assembly 20 is stored in the transformer T, and when the switch tube Q1 is turned off, the energy in the transformer T is released to the power grid 30.

[0048] like Figure 2 As shown, the power limiting method of the flyback converter includes the following steps:

[0049] Step S210: sampling the DC voltage and the grid voltage of the flyback converter 10; and calculating the power limit value based on the DC voltage and the grid voltage.

[0050] Specifically, according to the characteristics and requirements of the flyback converter 10, a suitable voltage sampling method is selected. Available methods include pulse sampling, adaptive sampling, etc. According to the sampling method, a corresponding sampling circuit is selected. For example, a resistor divider circuit is a simple and commonly used voltage sampling circuit, which uses a resistor network to divide the input voltage to obtain a sampling signal proportional to the input voltage. During a specific working cycle of the flyback converter 10, a DC voltage signal is captured by a sampling circuit. The sampled voltage signal is subjected to necessary processing, such as filtering, amplification, etc., to improve the accuracy and reliability of the data. And the processed data is converted into a digital signal for subsequent analysis and processing. Similarly, according to the characteristics and requirements of the grid voltage, a suitable sampling strategy is formulated, including determining parameters such as sampling frequency and sampling point. Select equipment suitable for grid voltage sampling, such as voltage transformers, sampling modules, etc. These devices should have the characteristics of high precision and high reliability. During a specific cycle of the grid voltage, the voltage signal is captured by a sampling device.

[0051] Specifically, the power limit value is calculated by deriving the relationship between the DC voltage, the grid voltage and the maximum power transmitted by the flyback circuit, with the maximum power transmitted by the flyback circuit as a boundary.

[0052] Step S220 , obtaining the maximum output power of the DC battery assembly 20 , wherein the DC battery assembly 20 is connected to the flyback converter 10 .

[0053] Specifically, one end of the flyback converter 10 is connected to the DC battery assembly 20, and the other end is connected to the external power grid 30. The DC battery assembly 20 can be a DC power source such as a wind power generation assembly or a photovoltaic power generation assembly. Taking the photovoltaic panel as an example, there is a complex relationship between the temperature and the total resistance of the photovoltaic panel, so its output efficiency has a nonlinear relationship, which can be represented by a current-voltage characteristic curve. By constantly tracking the maximum power point of the photovoltaic panel, the efficiency of grid-connected power generation can be guaranteed.

[0054] Step S230, comparing the power limit value and the maximum output power, if the maximum output power is greater than the power limit value, taking the power limit value as the target output power.

[0055] Specifically, since the power limit value is determined based on the maximum power transmitted by the flyback converter 10, when the maximum output power of the DC battery assembly 20 is greater than the power limit value, the power is limited to avoid the primary current of the flyback converter 10 from exceeding the limit, thereby improving system stability.

[0056] Correspondingly, if the maximum output power is not greater than the power limit value, the maximum output power is used as the target output power. When the maximum output power is not greater than the power limit value, there is no primary side overcurrent problem, and the maximum output power can be directly used to control the flyback converter 10 to improve the efficiency of grid-connected power generation.

[0057] Step S240 , generating a modulation signal based on the target output power to control the on-time of the switch tube of the flyback converter 10 .

[0058] Specifically, the power of the flyback converter 10 is related to the conduction time of the switch tube thereof, and a PWM modulation signal is generated according to the target output power after being limited to avoid overcurrent of the flyback converter 10 .

[0059] In this embodiment, the DC voltage and the grid voltage of the flyback converter 10 are sampled; the power limit value is calculated based on the DC voltage and the grid voltage; the maximum output power of the DC battery assembly 20 is obtained, and the DC battery assembly 20 is connected to the flyback converter 10; the power limit value and the maximum output power are compared, and if the maximum output power is greater than the power limit value, the power limit value is used as the target output power; a modulation signal is generated based on the target output power to control the turn-on time of the switch tube of the flyback converter 10, which can avoid overcurrent on the primary side of the flyback circuit and achieve control of the output power amplitude, thereby reducing the large energy impact caused by power mutation and improving the stress of components.

[0060] In some embodiments, based on the above step S210, sampling the DC voltage and the grid voltage of the flyback converter 10 specifically includes the following steps:

[0061] Step S211 : sampling the initial DC voltage and the initial grid voltage of the flyback converter 10 based on the digital-to-analog converter.

[0062] Step S212, filtering the initial DC voltage and the initial grid voltage to obtain a DC voltage and a grid voltage.

[0063] Specifically, the digital-to-analog converter ADC converts continuous analog DC signals and analog AC signals into discrete digital signals. This is usually done through four steps: sampling, holding, quantization, and encoding. The acquired digital signal can then be filtered to smooth the signal and reduce the impact of noise. The DC power supply and grid voltage can both be filtered using a sliding window algorithm, or they can each use a different filtering algorithm, such as median filtering, limiting filtering, etc.

[0064] In some embodiments, based on the above step S212, filtering the initial DC voltage and the initial grid voltage to obtain the DC voltage and the grid voltage specifically includes:

[0065] Based on the sliding window, the initial DC voltage and the initial grid voltage are filtered to obtain the DC voltage and the grid voltage; wherein the sliding window is an industrial frequency window.

[0066] Specifically, sliding window filtering is an effective digital filtering method that can be used to smooth DC and AC signals. It smoothes data or removes noise by performing statistical operations (such as mean, median, etc.) on the data within a fixed-size window. This window slides over the data sequence, moving one or more data points each time, and then recalculates the data operation results within the window.

[0067] A larger window can smooth data and remove noise more effectively, but may cause signal delay and distortion; a smaller window may not completely remove noise, but can retain more signal details. The power frequency window refers to the time window corresponding to the power frequency cycle of the power grid. Selecting the power frequency window can ensure that the filter's smoothing of the power grid signal does not introduce additional frequency components or distortion.

[0068] In some embodiments, based on the above step S210, the power limit value is calculated based on the DC voltage and the grid voltage, which specifically includes the following steps:

[0069] Step S213, obtaining preset hardware design parameters and power factor angle.

[0070] Step S214, calculating the power limit value based on the hardware design parameters, the power factor angle, the DC voltage and the grid voltage.

[0071] Specifically, the hardware design parameters include the primary peak current i mp And the number of transformer turns N. The power limit value P is calculated as follows:

[0072] ;

[0073] Among them, p c equal:

[0074] ;

[0075] In the formula, i mp is the primary peak current, N is the number of transformer turns, p θ is the power factor angle, V dc is the DC voltage, U m is the grid voltage.

[0076] The power limit value derivation process is as follows:

[0077] Assume that the current effective value of the grid voltage is U m , the effective value of the current is I m , the power factor angle is θc , grid voltage phase angle θ g .

[0078] Then the instantaneous value of the grid voltage u g and the instantaneous value of the grid current i g for:

[0079] ;

[0080] ;

[0081] Instantaneous power p g for:

[0082] ;

[0083] Instantaneous power p g Take the extreme value p gm hour:

[0084] ;

[0085] ;

[0086] The instantaneous power p in one power frequency cycle g Take the integral to get the effective value p rms :

[0087] ;

[0088] Extreme value p gm With the effective value p rms The relationship is:

[0089] .

[0090] In addition, according to the flyback operation formula, the maximum energy w is transmitted in the flyback continuous mode. m for:

[0091] ;

[0092] Where Lp is the primary inductance, i mp is the primary peak current.

[0093] Primary conduction time t on =Lp×i pm / V dc , where Lp is the primary inductance, i mp is the primary peak current, V dc is a DC voltage.

[0094] Secondary side conduction time t off =N×Lp×i pm / Um cos(0.5θ c ), where N is the number of transformer turns, Lp is the primary inductance, i mp is the primary peak current, U m is the grid voltage, θ c is the power factor angle.

[0095] Therefore, the maximum power p delivered by the flyback circuit is fm for:

[0096] .

[0097] To avoid the primary current exceeding the limit, the relationship must be satisfied: p fm >>p gm .

[0098] Combining the above formulas, we can deduce:

[0099] ;

[0100] Among them, p c equal:

[0101] .

[0102] Specifically, the primary peak current i mp Based on the hardware design calculation, it can be calculated in advance according to the common-mode inductance of the flyback converter and preset in the power limiting algorithm. θ It is also preset in the algorithm according to actual needs.

[0103] In this embodiment, there is no AC side current sampling, and the safe power can be derived by mathematical method, which reduces the number of detection components in the circuit and saves costs.

[0104] In some embodiments, based on the above step S220, obtaining the maximum output power of the DC battery assembly 20 specifically includes the following steps:

[0105] Step S221 , calculating the maximum output power of the DC battery assembly 20 based on the perturbation and observation method of maximum power point tracking.

[0106] Specifically, the perturbation observation method based on maximum power point tracking (MPPT) gradually approaches the maximum power point by continuously changing the output voltage (or current) of the battery and observing the resulting power changes. The following are the basic steps for calculating the maximum output power of the DC battery assembly 20 using the perturbation observation method: (1) Initialization: Select an initial voltage or current operating point and measure the power output at this time. (2) Perturbation: Apply a small voltage or current disturbance based on the current operating point. (3) Observation: Measure the power output after the disturbance. (4) Comparison and decision: If the power after the disturbance is greater than the power before the disturbance, it means that the disturbance direction is correct and the disturbance continues to be applied in this direction. If the power after the disturbance is less than the power before the disturbance, it means that the disturbance direction is wrong and the disturbance is applied in the opposite direction. (5) Iteration: Repeat steps (2)-(4) until a stop condition is met (such as the power change is less than a preset threshold, or the maximum number of iterations is reached). (6) Record results: Record the final operating point (voltage and current) and the corresponding maximum power output.

[0107] In this embodiment, the disturbance observation method of maximum power point tracking can quickly and accurately calculate the maximum output power to ensure power generation efficiency.

[0108] In some embodiments, based on the above step S240, before generating a modulation signal based on the target output power to control the turn-on time of the switch tube of the flyback converter 10, the method further includes:

[0109] Step S250: If the maximum output power is not greater than the power limit value, the maximum output power is used as the target output power.

[0110] In this embodiment, it is ensured that the primary side does not have overcurrent, and the power generation efficiency is also guaranteed at the same time.

[0111] In this embodiment, a grid-connected system is provided. Figure 3 Schematic diagram of the grid-connected system structure of this embodiment. Figure 3 As shown, the system includes: a flyback converter 10, a DC battery assembly 20 and a power grid 30; the flyback converter 10 includes a switch tube Q1, a transformer T, a first diode D1 and a controller.

[0112] The DC battery assembly 20 is connected to the primary coil Lp of the transformer T through the switch tube Q1. The secondary coil Ls of the transformer T is connected to the power grid 30 through the first diode D1. The controller is connected to the switch tube Q1, and the controller is used to execute the steps of the power limiting method of the flyback converter 10 in any of the above embodiments.

[0113] For details, see Figure 3, the flyback converter 10 also includes a capacitor C and a second diode D2. The positive electrode of the DC battery assembly 20 is connected to the first end of the primary coil Lp of the transformer T, the negative electrode of the DC battery assembly 20 is connected to the first end of the switch tube Q1, the second end of the switch tube Q1 is connected to the second end of the primary coil Lp of the transformer T, and the third end of the switch tube Q1 is connected to the controller for inputting a modulation signal. The first end of the switch tube Q1 is also connected to the positive electrode of the second diode D2, and the negative electrode of the second diode D2 is connected to the second end of the switch tube Q1. A capacitor C is also connected in parallel at both ends of the DC battery assembly 20. The first end of the secondary coil Ls of the transformer T is connected to the positive electrode of the first diode D1, and the second end of the secondary coil Ls of the transformer T is connected to the negative electrode of the first diode D1 as an AC output end and connected to both ends of the power grid 30.

[0114] Its working principle is: when the switch tube Q1 is turned on, the primary inductor current of the transformer T starts to rise, the first diode D1 is turned off, and the transformer T stores energy; when the switch tube Q1 is turned off, the primary inductor induced voltage of the transformer T is reversed, at this time the first diode D1 is turned on, and the energy in the transformer T supplies power to the load through the first diode D1.

[0115] In this embodiment, by controlling the output power amplitude and avoiding overcurrent on the primary side of the flyback circuit, the large energy impact caused by power mutation can be reduced, the stress of components can be improved, and there is no AC side current sampling, which reduces the number of detection components in the circuit and saves costs.

[0116] The present application is described below through preferred embodiments.

[0117] The power limit value derivation process is as follows:

[0118] Assume that the current effective value of the grid voltage is U m , the effective value of the current is I m , the power factor angle is θ c , grid voltage phase angle θ g .

[0119] Then the instantaneous value of the grid voltage u g and the instantaneous value of the grid current i g for:

[0120] ;

[0121] ;

[0122] Instantaneous power p g for:

[0123] ;

[0124] Instantaneous power p g Take the extreme value pgm hour:

[0125] ;

[0126] ;

[0127] The instantaneous power p in one power frequency cycle g Take the integral to get the effective value p rms :

[0128] ;

[0129] Extreme value p gm With the effective value p rms The relationship is:

[0130] .

[0131] In addition, according to the flyback operation formula, the maximum energy w is transmitted in the flyback continuous mode. m for:

[0132] ;

[0133] Where Lp is the primary inductance, i mp is the primary peak current.

[0134] Primary conduction time t on =Lp×i pm / V dc , where Lp is the primary inductance, i mp is the primary peak current, V dc is a DC voltage.

[0135] Secondary side conduction time t off =N×Lp×i pm / U m cos(0.5θ c ), where N is the number of transformer turns, Lp is the primary inductance, i mp is the primary peak current, U m is the grid voltage, θ c is the power factor angle.

[0136] Therefore, the maximum power p delivered by the flyback circuit is fm for:

[0137] .

[0138] To avoid the primary current exceeding the limit, the relationship must be satisfied: p fm >>p gm .

[0139] Combining the above formulas, we can deduce:

[0140] ;

[0141] Among them, p c equal:

[0142] .

[0143] Based on the above analysis, according to the primary peak current i mp , Grid voltage U m , DC voltage V dc , transformer turns N and power factor angle θ c , the maximum output power limit value at the current moment can be calculated.

[0144] The following is the program control strategy:

[0145] 1. Based on the digital-to-analog converter ADC sampling DC-AC conversion, the DC-AC is filtered using a sliding window filter, and the filter window is designed as an industrial frequency window.

[0146] 2. Calculate the DC voltage V within the power frequency cycle based on the sliding window filter dc , grid voltage effective value U m .

[0147] 3. Obtain the maximum output power of the maximum power point tracking mppt disturbance output when connected to the grid.

[0148] 4. Based on the primary peak current i mp , Grid voltage U m , DC voltage V dc , transformer turns N and power factor angle θ c , calculate the power limit value.

[0149] 5. If the maximum output power is greater than the power limit value, the power limit value is used as the target output power. If the maximum output power is not greater than the power limit value, the maximum output power is used as the target output power.

[0150] 6. Substitute the target output power into the flyback operation to generate a PWM modulation signal.

[0151] Through this preferred embodiment, under certain conditions, such as grid voltage changes, DC voltage jitter, and power factor angle changes, the output power amplitude can be controlled to avoid overcurrent on the primary side of the flyback circuit, thereby reducing the large energy impact caused by power mutations and improving the stress of components. In addition, in this preferred embodiment, there is no AC side current sampling, and the power limit value is derived by mathematical methods, which reduces the number of detection components in the circuit and saves costs.

[0152] It should be noted that the steps shown in the above process or the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0153] In this embodiment, a power limiting device for a flyback converter is also provided, which is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. The terms "module", "unit", "subunit", etc. used below can implement a combination of software and / or hardware for a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0154] Figure 4 : is a structural block diagram of the power limiting device of the flyback converter of this embodiment, such as Figure 4 As shown, the device includes: a voltage sampling module 41 , a power tracking module 42 , a power comparison module 43 and a flyback operation module 44 .

[0155] The voltage sampling module 41 is used to sample the DC voltage and the grid voltage of the flyback converter; and calculate the power limit value based on the DC voltage and the grid voltage.

[0156] The power tracking module 42 is used to obtain the maximum output power of the DC battery assembly, and the DC battery assembly is connected to the flyback converter.

[0157] The power comparison module 43 is used to compare the power limit value and the maximum output power. If the maximum output power is greater than the power limit value, the power limit value is used as the target output power.

[0158] The flyback operation module 44 is used to generate a modulation signal based on the target output power to control the turn-on time of the switch tube of the flyback converter.

[0159] In some of the embodiments, the voltage sampling module 41 is further used to sample the initial DC voltage and the initial grid voltage of the flyback converter based on a digital-to-analog converter; filter the initial DC voltage and the initial grid voltage to obtain a DC voltage and a grid voltage.

[0160] In some of the embodiments, the voltage sampling module 41 is further used to filter the initial DC voltage and the initial grid voltage based on a sliding window to obtain a DC voltage and a grid voltage; wherein the sliding window is an industrial frequency window.

[0161] In some of the embodiments, the voltage sampling module 41 is further used to obtain preset hardware design parameters and a power factor angle; and calculate the power limit value based on the hardware design parameters, the power factor angle, the DC voltage, and the grid voltage.

[0162] In some of the embodiments, the hardware design parameters include: primary side peak current and transformer turns.

[0163] In some of the embodiments, the power tracking module 42 is further configured to calculate the maximum output power of the DC battery assembly based on a perturbation-observation method of maximum power point tracking.

[0164] In some embodiments, the power comparison module 43 is further configured to use the maximum output power as the target output power if the maximum output power is not greater than the power limit value.

[0165] It should be noted that the above modules can be functional modules or program modules, and can be implemented by software or hardware. For modules implemented by hardware, the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0166] In this embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0167] Optionally, the computer device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0168] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementation modes, and will not be repeated in this embodiment.

[0169] In addition, in combination with the power limiting method of the flyback converter provided in the above embodiments, a storage medium can also be provided in this embodiment to implement the method. The storage medium stores a computer program; when the computer program is executed by the processor, any power limiting method of the flyback converter in the above embodiments is implemented.

[0170] It should be understood that the specific embodiments described herein are only used to explain the application, rather than to limit it. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of this application.

[0171] Obviously, the drawings are only some examples or embodiments of the present application. For ordinary technicians in the field, the present application can also be applied to other similar situations based on these drawings without creative work. In addition, it is understandable that although the work done in this development process may be complicated and lengthy, for ordinary technicians in the field, certain changes in design, manufacturing or production based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient content disclosed in this application.

[0172] The term "embodiment" in this application refers to a specific feature, structure or characteristic described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various locations in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. It is clearly or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.

[0173] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A power limiting method for a flyback converter, characterized in that: The method comprises: Sampling the DC voltage and the grid voltage of the flyback converter; calculating the power limit value based on the DC voltage and the grid voltage; wherein the DC voltage is the DC voltage at the input side of the flyback converter; The step of calculating the power limit value based on the DC voltage and the grid voltage includes: Obtaining preset hardware design parameters and power factor angle; calculating the power limit value based on the hardware design parameters, the power factor angle, the DC voltage and the grid voltage; the hardware design parameters include: primary peak current and transformer turns; Obtaining a maximum output power of a DC battery assembly, wherein the DC battery assembly is connected to the flyback converter; Comparing the power limit value with the maximum output power, if the maximum output power is greater than the power limit value, taking the power limit value as the target output power; A modulation signal is generated based on the target output power to control the turn-on time of the switch tube of the flyback converter.

2. The power limiting method of the flyback converter according to claim 1, characterized in that: The sampling of the DC voltage and the grid voltage of the flyback converter includes: Sampling the initial DC voltage and the initial grid voltage of the flyback converter based on a digital-to-analog converter; The initial DC voltage and the initial grid voltage are filtered to obtain a DC voltage and a grid voltage.

3. The power limiting method of the flyback converter according to claim 2, characterized in that: The filtering of the initial DC voltage and the initial grid voltage to obtain a DC voltage and a grid voltage includes: Based on a sliding window, the initial DC voltage and the initial grid voltage are filtered to obtain a DC voltage and a grid voltage; wherein the sliding window is a power frequency window.

4. The power limiting method of a flyback converter according to claim 1, characterized in that: The obtaining of the maximum output power of the DC battery assembly includes: The maximum output power of the DC battery module is calculated based on the perturbation and observation method of maximum power point tracking.

5. The power limiting method of a flyback converter according to claim 1, characterized in that: Before generating a modulation signal based on the target output power to control the on-time of the switch tube of the flyback converter, the method further includes: If the maximum output power is not greater than the power limit value, the maximum output power is used as the target output power.

6. A power limiting device for a flyback converter, characterized in that: The device comprises: A voltage sampling module, used for sampling the DC voltage and the grid voltage of the flyback converter; calculating the power limit value based on the DC voltage and the grid voltage; wherein the DC voltage is the DC voltage at the input side of the flyback converter; wherein the power limit value is calculated based on the DC voltage and the grid voltage, including: obtaining preset hardware design parameters and power factor angle; calculating the power limit value based on the hardware design parameters, the power factor angle, the DC voltage and the grid voltage; the hardware design parameters include: primary peak current and transformer turns; A power tracking module, used to obtain the maximum output power of a DC battery assembly, the DC battery assembly being connected to the flyback converter; A power comparison module, used for comparing the power limit value with the maximum output power, and if the maximum output power is greater than the power limit value, taking the power limit value as the target output power; The flyback operation module is used to generate a modulation signal based on the target output power to control the turn-on time of the switch tube of the flyback converter.

7. A grid-connected system, characterized in that: include: A flyback converter, a DC battery assembly and a power grid; the flyback converter includes a switch tube, a transformer, a first diode and a controller; The DC battery assembly is connected to the primary coil of the transformer through the switch tube; The secondary coil of the transformer is connected to the power grid through the first diode; The controller is connected to the switch tube, and the controller is used to execute the steps of the power limiting method for a flyback converter according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the power limiting method for a flyback converter according to any one of claims 1 to 5 are implemented.

Images