Light load control method, device and equipment of optical storage preceding-stage LLC resonant converter and medium

Abstract

The invention relates to the technical field of power electronic control, in particular to a light load control method, device, equipment and medium for an optical storage preceding-stage LLC resonant converter, and the method comprises the steps: carrying out the difference between an output voltage and a voltage reference value of a frequency loop, and inputting the difference into a PI controller of the frequency loop; the sawtooth carrier wave and the modulation wave are intersected to generate a driving signal of a primary side switch tube, the driving signal is compared with an output limiting amplitude, and whether a frequency loop is in a saturated state is judged; the difference between the output voltage and the voltage reference value of the intermittent ring is input into a PI controller of the intermittent ring to generate an output value; comparing the output value with a preset threshold value, and judging whether the intermittent ring is in a saturated state or not; according to whether the frequency loop and the intermittent loop are in the saturation state or not, the operation condition of the LLC resonant converter is judged, the input voltage range of the LLC resonant converter is widened by setting the intermittent control loop and adopting intermittent control under the light load condition, and the problem that the voltage gain of traditional frequency conversion control is too high under the light load condition is effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of power electronic control technology, and in particular to a light load control method, device, equipment and medium for a pre-photovoltaic storage LLC resonant converter. Background Art

[0002] With the development of power electronics technology, the requirements for the working efficiency and power density of power converters are getting higher and higher. Increasing the switching frequency can effectively reduce the volume of inductive components in the converter, but increasing the switching frequency brings higher switching losses and reduces the conversion efficiency; LLC resonant converters have more and more applications in photovoltaic storage systems, DC microgrids, ship power systems, etc. due to their high efficiency, small size and easy soft switching.

[0003] In existing research, LLC resonant converters often use pulse frequency modulation (PFM) to adjust the output voltage. However, under light load conditions, the voltage gain of traditional frequency conversion control is large, which greatly limits the input voltage range of the converter and makes it difficult to meet the application requirements of a wide range of input voltages for photovoltaic storage systems. Intermittent control (PWM-burst) can widen the input voltage range to a certain extent, but the existing solutions still have disadvantages such as large output voltage ripple and low efficiency.

[0004] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0005] The present invention provides a light-load control method, device, equipment and medium for a photovoltaic storage front-stage LLC resonant converter, thereby effectively solving the problems in the background technology.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a light load control method of a photovoltaic storage front-stage LLC resonant converter, designing two voltage closed loops, including a frequency loop and an intermittent loop, the frequency loop is used for frequency conversion control to output a switch tube drive signal, and the intermittent loop is used to determine whether to enter an intermittent control working condition, including the following steps:

[0007] Subtracting the output voltage from the voltage reference value of the frequency loop to obtain a first voltage difference value, inputting the first voltage difference value into a PI controller of the frequency loop, and setting an output limit;

[0008] Generate a sawtooth carrier according to the PI controller output of the frequency loop, wherein the sawtooth carrier intersects with the modulation wave to generate a driving signal for the primary switch tube;

[0009] The driving signal is compared with the output amplitude limit to determine whether the frequency loop is in a saturated state;

[0010] Subtracting the output voltage from the voltage reference value of the intermittent ring to obtain a second pressure difference value, and inputting the second pressure difference value into the PI controller of the intermittent ring to generate an output value of the PI controller;

[0011] The output value is compared with a preset threshold value to determine whether the intermittent loop is in a saturated state;

[0012] The operating condition of the LLC resonant converter is determined according to whether the frequency loop and the intermittent loop are in a saturated state, thereby generating switch tube drive signals with different characteristics to realize the control of the LLC resonant converter.

[0013] Furthermore, the output limit of the frequency loop PI controller is set to a maximum count number, the upper limit of the output limit corresponds to the maximum count number of the minimum switching frequency, and the lower limit of the output limit corresponds to the maximum count number of the maximum switching frequency.

[0014] Further, it is determined whether the driving signal reaches the set upper limit or the lower limit. If so, the frequency loop is in a saturated state; if not, the frequency loop is in an unsaturated state.

[0015] Furthermore, the sawtooth carrier is generated according to a counting method, and the output voltage is adjusted according to the switching frequency and voltage gain at different frequencies corresponding to different outputs.

[0016] Furthermore, the duty cycle of the driving signal of the switch tube is fixed, and the amplitude of the modulated wave is 0.5 times the amplitude of the sawtooth carrier.

[0017] Furthermore, the output value is compared with the preset threshold to determine whether the output value reaches the upper limit or lower limit of the preset threshold. If so, the intermittent ring is in a saturated state; if not, the intermittent ring is in an unsaturated state.

[0018] Further, the determining the operating condition of the LLC resonant converter includes:

[0019] When the frequency loop and the intermittent loop are both in an unsaturated state, the LLC resonant converter is in normal operation;

[0020] When the frequency loop is in negative saturation and the intermittent loop is in an unsaturated state, the LLC resonant converter operates in a negative saturation condition;

[0021] When the frequency loop and the intermittent loop are both in a saturated state, the LLC resonant converter operates in an intermittent operating state.

[0022] Further, under the normal operating condition, the LLC resonant converter adjusts the switching frequency through frequency conversion control to control the output voltage at the voltage reference value of the frequency loop;

[0023] Under the negative saturation condition, the output of the frequency loop PI controller is stabilized at the lower limit of the output amplitude limit, the switching frequency is limited to the maximum switching frequency, and the gain is at the minimum value;

[0024] Under the intermittent working condition, in the case where the load is too light and the input voltage is too high, the drive signal is turned off when the intermittent loop PI controller outputs negative saturation, and the output voltage is dynamically stabilized at the voltage reference value of the intermittent loop.

[0025] The present invention also includes a light load control device for a photovoltaic storage front-stage LLC resonant converter, characterized in that the above method is used, including:

[0026] A frequency loop input unit, used for obtaining a first voltage difference value by subtracting the output voltage from the voltage reference value of the frequency loop, inputting the first voltage difference value into the PI controller of the frequency loop, and setting the output limit;

[0027] A signal conversion unit, used for generating a sawtooth carrier according to the PI controller output of the frequency loop; the sawtooth carrier intersects with the modulation wave to generate a driving signal for the primary switch tube;

[0028] A frequency loop comparison unit, used for comparing the drive signal with the output limit, and determining whether the frequency loop is in a saturated state;

[0029] An intermittent loop input unit, used for obtaining a second voltage difference value by subtracting the output voltage from the voltage reference value of the intermittent loop, and inputting the second voltage difference value into the PI controller of the intermittent loop to generate an output value of the PI controller;

[0030] An intermittent ring comparison unit, used to compare the output value with a preset threshold value to determine whether the intermittent ring is in a saturated state;

[0031] The operating condition judging unit is used to judge the operating condition of the LLC resonant converter according to whether the frequency loop and the intermittent loop are in a saturated state, thereby generating switch tube driving signals with different characteristics to realize the control of the LLC resonant converter.

[0032] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.

[0033] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0034] The beneficial effects of the present invention are:

[0035] By setting an intermittent control loop and taking intermittent control under light load conditions, the input voltage range of the LLC resonant converter is widened. This effectively solves the problem of excessive voltage gain of traditional LLC variable frequency control under light load conditions, and sets negative saturation conditions to further widen the input voltage range.

[0036] Compared with the traditional intermittent control method using voltage hysteresis, the dual-loop control design ensures the efficient operation of the LLC resonant converter under light load and normal load conditions, effectively suppresses the output voltage ripple, reduces losses, and improves conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a flow chart of a light load control method of a front-stage LLC resonant converter of a photovoltaic storage device;

[0039] Figure 2 It is the topological structure diagram of full-bridge LLC resonant converter;

[0040] Figure 3 This is the control block diagram of the full-bridge LLC resonant converter;

[0041] Figure 4 It is a flow chart of a light load control method of a LLC resonant converter before a photovoltaic storage device;

[0042] Figure 5 It is the output voltage and primary switch tube driving waveform under intermittent working condition;

[0043] Figure 6 This is the output voltage waveform after load shedding;

[0044] Figure 7 It is a structural schematic diagram of a light-load control device of a pre-photovoltaic storage LLC resonant converter;

[0045] Figure 8 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0047] like Figures 1 to 6 As shown in the figure: A light load control method for a photovoltaic storage front-stage LLC resonant converter is designed with two voltage closed loops, including a frequency loop and an intermittent loop. The frequency loop is used for frequency conversion control of the output switch tube drive signal, and the intermittent loop is used to determine whether to enter the intermittent control condition. Figure 1 As shown, the following steps are included:

[0048] S10: The sampled output voltage V out The voltage reference value V of the frequency loop ref1 The first pressure difference is obtained by difference, and the first pressure difference is input into the PI controller of the frequency loop, and the output limit is set; it should be noted that the amplitude of the limit here should not be fixed, but should be set according to the switching frequency range. In this embodiment, according to the component parameter design, the resonant frequency is about 90kHz. In order to make the main operating frequency of the LLC resonant converter near the resonant frequency, the switching frequency range is set to 60k-160kHz in this embodiment;

[0049] S20: generating a sawtooth carrier according to the PI controller output of the frequency loop, and the sawtooth carrier intersects with the modulation wave to generate a driving signal for the primary switch tube;

[0050] S30: Compare the driving signal with the output limit to determine whether the frequency loop is in a saturated state;

[0051] S40: The sampled output voltage V out The voltage reference value V of the intermittent loop ref2 The second pressure difference value is obtained by differential calculation, and the second pressure difference value is input into the PI controller of the intermittent loop to generate an output value of the PI controller;

[0052] S50: Compare the output value with the preset threshold value to determine whether the intermittent loop is in a saturated state;

[0053] S60: judging the operating condition of the LLC resonant converter according to whether the frequency loop and the intermittent loop are in a saturated state, thereby generating switch tube driving signals with different characteristics to realize the control of the LLC resonant converter.

[0054] The operating condition of the LLC resonant converter is determined by the saturation state of the frequency loop and the intermittent loop PI controller outputs, and switch tube drive signals with different characteristics are generated. The LLC resonant converter used in this embodiment is as follows: Figure 2As shown, the primary side is a full-bridge inverter circuit, which is composed of four MOS tubes; the secondary side is a full-bridge uncontrolled rectifier circuit, which is composed of four diodes; the core part is the resonant cavity, which is composed of the resonant inductor L r , resonant capacitor C r , Excitation inductance L m The resonance between the components can realize zero-voltage turn-on of the primary MOSFET and zero-current turn-off of the secondary diode, thus reducing converter losses and improving conversion efficiency.

[0055] If the frequency loop enters the saturation state, it means that the system can no longer further optimize the output by adjusting the frequency. At this time, it can enter the intermittent mode or maintain the current operating state; if the intermittent loop enters the saturation state, it indicates that the control under light load has reached its limit. The system will maintain the intermittent mode, or automatically exit the intermittent mode when the load changes and resume normal operation; the dual-loop control design ensures the efficient operation of the LLC resonant converter under light load and normal load conditions, and reduces energy consumption through the intermittent mode under light load.

[0056] By designing the frequency loop and the intermittent loop, the output of the converter can be accurately controlled under light load conditions to reduce energy loss. At the same time, under light load, the switching frequency is reduced through intermittent control conditions, which reduces the number of times the switch tube is turned on and off, reducing switching losses. In addition, reducing switching actions can also reduce the heat loss of the switch tube and other power devices and extend the service life of the devices. Through the dual closed-loop control of the frequency loop and the intermittent loop, it can ensure that the system maintains an efficient and stable operating state even under light load. The judgment of the saturation state further prevents the system from becoming unstable under extreme conditions, improving the safety and reliability of the system.

[0057] The input voltage range of the LLC resonant converter is broadened, effectively solving the problem of excessive voltage gain of traditional frequency conversion control under light load conditions; and a negative saturation condition is set to further broaden the input voltage range.

[0058] Compared with the traditional intermittent control method using voltage hysteresis, it effectively suppresses the output voltage ripple, reduces the loss and improves the conversion efficiency.

[0059] As a preferred embodiment of the above embodiment, in step S10, the output limit of the frequency loop PI controller is set to the maximum count number, the upper limit of the output limit corresponds to the maximum count number of the minimum switching frequency, and the lower limit of the output limit corresponds to the maximum count number of the maximum switching frequency; in this embodiment, the sampling interval is selected as 1 / 24000000, and the upper limit of the output limit link is set to 400 and the lower limit is set to 150 accordingly.

[0060] The design of the limiting link keeps the output of the PI controller within a stable range, especially under light-load conditions. It can prevent the switching frequency from being too low, resulting in a decrease in system efficiency, or from being too high, resulting in an increase in switching losses. Therefore, it can more effectively adapt to load changes under light-load conditions.

[0061] In this embodiment, it is determined whether the driving signal reaches the set upper or lower limit. If so, the frequency loop is in a saturated state; if not, the frequency loop is in an unsaturated state. Specifically, by determining whether the driving signal reaches the upper or lower limit, it is possible to effectively prevent the system frequency from being over-regulated, and to prevent the frequency from exceeding the design range, resulting in unstable system operation or increased switching loss. This determination of the saturation state helps the system to operate stably.

[0062] Among them, in step S20, a sawtooth carrier is generated according to the counting method, and the output voltage is adjusted according to the switching frequency and voltage gain at different frequencies corresponding to different outputs. Specifically, by flexibly adjusting the frequency and gain, the system can maintain a stable output voltage under different load conditions.

[0063] In this embodiment, in step S30, the duty cycle of the driving signal of the switching tube is fixed, and the amplitude of the modulation wave is 0.5 times the amplitude of the sawtooth carrier, which helps to achieve a more stable driving signal, which will help to smooth the output voltage waveform and reduce high-frequency oscillations and electromagnetic interference (EMI).

[0064] Among them, in step S50, the output value is compared with a preset threshold to determine whether the output value reaches the upper limit or lower limit of the preset threshold. If so, the intermittent loop is in a saturated state; if not, the intermittent loop is in an unsaturated state, thereby achieving effective control of whether the LLC resonant converter enters the intermittent mode under a light load state, avoiding unnecessary frequent switching, and improving control accuracy; under light load conditions, the intermittent mode helps to reduce switching losses, and by comparing the output value with the threshold, it can avoid the converter from frequently entering unnecessary intermittent mode, thereby optimizing system efficiency, especially when the load changes little.

[0065] As a preference of the above embodiment, in step S60, Figure 3 As shown, judging the operating condition of the LLC resonant converter includes:

[0066] When both the frequency loop and the intermittent loop are in an unsaturated state, the LLC resonant converter is in normal operation;

[0067] When the frequency loop is in negative saturation and the intermittent loop is in unsaturated state, the LLC resonant converter operates in negative saturation condition;

[0068] When both the frequency loop and the intermittent loop are in saturation state, the LLC resonant converter operates in intermittent operation.

[0069] By simultaneously monitoring the saturation state of the frequency loop and the intermittent loop, the current operating mode of the LLC resonant converter can be accurately determined to ensure that under different load conditions, the system can make appropriate adjustments according to the operating conditions to avoid misjudgment or erroneous operation; when both the frequency loop and the intermittent loop are not saturated, the system is in normal operating mode; when both are saturated, the system enters intermittent working conditions. This design ensures a smooth transition from normal working conditions to intermittent working conditions, which helps to further reduce power consumption and switching losses under light load conditions and improve system efficiency. By accurately distinguishing different working conditions, frequent switching is avoided, the stability of the system is improved, and by reducing unnecessary high-frequency switching operations, the life of the switching components is extended and the reliability of the system is enhanced.

[0070] In this embodiment, if Figure 4 As shown in Figure 2, under normal operating conditions, the LLC resonant converter adjusts the switching frequency through variable frequency control to control the output voltage at the voltage reference value V of the frequency loop. ref1 ; This means that the system will continuously adjust the switching frequency to match the desired voltage output, achieving a stable output voltage;

[0071] Under negative saturation conditions, the output of the frequency loop PI controller is stabilized at the lower limit of the output limit, limiting the switching frequency to the maximum switching frequency and minimizing the gain. Compared with the traditional LLC resonant converter, the voltage input range and gain range are effectively increased.

[0072] Under intermittent working conditions, when the load is too light and the input voltage is too high, the drive signal is turned off when the intermittent loop PI controller outputs negative saturation, and the output voltage is dynamically stabilized at the voltage reference value V of the intermittent loop. ref2 , frequent switching actions can be avoided, and the output voltage fluctuation can be reduced by controlling the output voltage in a dynamic balance state.

[0073] This application is different from the traditional intermittent control method using a voltage hysteresis loop. The intermittent loop controls the output voltage at V ref2 Dynamic balance, rather than fluctuations within upper and lower limits, effectively reduces output voltage ripple and improves system stability and voltage control accuracy.

[0074] Through variable frequency control and maximum frequency limitation under negative saturation conditions, the system is ensured to operate stably under various conditions, thereby improving the stability of the system. Under negative saturation conditions, the system can effectively increase the voltage input range and gain range, thereby expanding the application range of the system. By dynamically balancing the output voltage, the voltage fluctuation in traditional methods is reduced, thereby improving the stability and accuracy of the output voltage. Under intermittent conditions, unnecessary switching operations are avoided, thereby optimizing the energy efficiency of the system and reducing energy consumption.

[0075] Continue to refer Figure 4 , mainly including the frequency loop and the intermittent loop, which divides the working state of the converter into three conditions: normal working condition, negative saturation working condition, and intermittent working condition. When the frequency loop and the intermittent loop are not negatively saturated, the converter operates under normal conditions, and the output voltage is controlled at V ref1 ; When the frequency loop is negatively saturated and the intermittent loop is not negatively saturated, the converter operates under negative saturation conditions, and the output voltage is controlled to be the product of the input voltage and the minimum voltage gain; when both the frequency loop and the intermittent loop are negatively saturated, the converter operates under intermittent conditions, and the output voltage is controlled to be V ref2 .

[0076] In order to verify the effectiveness of the above control method, this embodiment provides a specific example, and its main parameters are shown in Table 1:

[0077] Table 1 Key parameters

[0078]

[0079]

[0080] Under intermittent working conditions, the output voltage and the switch tube drive waveform are as follows: Figure 5 As shown; the output voltage waveform of load shedding under fixed input voltage is as follows Figure 6 shown.

[0081] like Figure 5 As shown, the converter works in intermittent conditions, and the output voltage is dynamically stable at V ref2 =780V, and the voltage ripple is small, which proves that the light load control method proposed in the embodiment of the present invention has good steady-state performance.

[0082] like Figure 6 As shown, in the initial state, the load P1=10kW, the converter works in normal conditions, and at 0.15s the load is switched to P2=5kW, and the converter switching condition enters a negative saturation condition; at 0.3s the load is switched to P3=0.5kW, and the converter switching condition enters an intermittent condition. It can be seen from the figure that the voltage change is completed in a relatively short time, and the voltage fluctuation is relatively small, which proves that the sampling control method in this embodiment has better dynamic performance.

[0083] This light load control strategy is applied to LLC resonant converters, but is not limited to Figure 2 The topology shown.

[0084] The present invention also includes a light load control device for a photovoltaic storage front-stage LLC resonant converter, using the above method, such as Figure 7 As shown, including:

[0085] A frequency loop input unit, used to obtain a first voltage difference value by subtracting the output voltage from a voltage reference value of the frequency loop, input the first voltage difference value into a PI controller of the frequency loop, and set an output limit;

[0086] A signal conversion unit is used to generate a sawtooth carrier according to the output of the PI controller of the frequency loop; the sawtooth carrier intersects with the modulation wave to generate a driving signal for the primary switch tube;

[0087] The frequency loop comparison unit is used to compare the driving signal with the output limit to determine whether the frequency loop is in a saturated state;

[0088] An intermittent loop input unit, used for obtaining a second pressure difference value by subtracting the output voltage from a voltage reference value of the intermittent loop, and inputting the second pressure difference value into a PI controller of the intermittent loop to generate an output value of the PI controller;

[0089] The intermittent loop comparison unit is used to compare the output value with the preset threshold value to determine whether the intermittent loop is in a saturated state;

[0090] The operating condition judging unit is used to judge the operating condition of the LLC resonant converter according to whether the frequency loop and the intermittent loop are in a saturated state, thereby generating switch tube driving signals with different characteristics to realize the control of the LLC resonant converter.

[0091] See also Figure 8 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0092] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0093] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (Static Random Access Memory, referred to as SRAM), electrically erasable programmable read-only memory (Electrically Erasable Programmable Read-Only Memory, referred to as EEPROM), erasable programmable read-only memory (Erasable Programmable Read Only Memory, referred to as EPROM), programmable read-only memory (Programmable Red-Only Memory, referred to as PROM), read-only memory (Read-Only Memory, referred to as ROM), magnetic storage, flash memory, disk or optical disk.

[0094] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0095] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0096] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0097] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0098] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0099] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0100] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0101] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A light load control method for a photovoltaic storage front-stage LLC resonant converter, characterized in that: Design two voltage closed loops, including a frequency loop and an intermittent loop. The frequency loop is used for frequency conversion control to output the switch tube drive signal, and the intermittent loop is used to determine whether to enter the intermittent control working condition, including the following steps: Subtracting the output voltage from the voltage reference value of the frequency loop to obtain a first voltage difference value, inputting the first voltage difference value into a PI controller of the frequency loop, and setting an output limit; Generate a sawtooth carrier according to the PI controller output of the frequency loop, wherein the sawtooth carrier intersects with the modulation wave to generate a driving signal for the primary switch tube; The driving signal is compared with the output amplitude limit to determine whether the frequency loop is in a saturated state; Subtracting the output voltage from the voltage reference value of the intermittent ring to obtain a second pressure difference value, and inputting the second pressure difference value into the PI controller of the intermittent ring to generate an output value of the PI controller; The output value is compared with a preset threshold value to determine whether the intermittent loop is in a saturated state; The operating condition of the LLC resonant converter is determined according to whether the frequency loop and the intermittent loop are in a saturated state, thereby generating switch tube drive signals with different characteristics to realize the control of the LLC resonant converter.

2. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 1 is characterized in that: The output amplitude limit of the frequency loop PI controller is set to a maximum count number, wherein the upper limit of the output amplitude limit corresponds to the maximum count number of the minimum switching frequency, and the lower limit of the output amplitude limit corresponds to the maximum count number of the maximum switching frequency.

3. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 2 is characterized in that: Determine whether the driving signal reaches the set upper limit or the lower limit, and if so, the frequency loop is in a saturated state; If not, the frequency loop is in an unsaturated state.

4. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 1 is characterized in that: The sawtooth carrier is generated according to the counting method, and the output voltage is adjusted according to the switching frequency and voltage gain at different frequencies corresponding to different outputs.

5. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 1 is characterized in that: The duty cycle of the driving signal of the switch tube is fixed, and the amplitude of the modulated wave is 0.5 times the amplitude of the sawtooth carrier.

6. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 1 is characterized in that: The output value is compared with the preset threshold value to determine whether the output value reaches the upper limit or the lower limit of the preset threshold value, and if so, the intermittent loop is in a saturated state; If not, the intermittent loop is in an unsaturated state.

7. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 1 is characterized in that: The determining the operating condition of the LLC resonant converter includes: When the frequency loop and the intermittent loop are both in an unsaturated state, the LLC resonant converter is in normal operation; When the frequency loop is in negative saturation and the intermittent loop is in an unsaturated state, the LLC resonant converter operates in a negative saturation condition; When the frequency loop and the intermittent loop are both in a saturated state, the LLC resonant converter operates in an intermittent operating state.

8. The light load control method of the LLC resonant converter before the photovoltaic storage according to claim 7 is characterized in that: Under the normal working condition, the LLC resonant converter adjusts the switching frequency through frequency conversion control to control the output voltage at the voltage reference value of the frequency loop; Under the negative saturation condition, the output of the frequency loop PI controller is stabilized at the lower limit of the output amplitude limit, the switching frequency is limited to the maximum switching frequency, and the gain is at the minimum value; Under the intermittent working condition, in the case where the load is too light and the input voltage is too high, the drive signal is turned off when the intermittent loop PI controller outputs negative saturation, and the output voltage is dynamically stabilized at the voltage reference value of the intermittent loop.

9. A light load control device for a photovoltaic storage front-stage LLC resonant converter, characterized in that: Use of the method according to any one of claims 1 to 8, comprising: A frequency loop input unit, used for obtaining a first voltage difference value by subtracting the output voltage from the voltage reference value of the frequency loop, inputting the first voltage difference value into the PI controller of the frequency loop, and setting the output limit; A signal conversion unit, used for generating a sawtooth carrier according to the PI controller output of the frequency loop; the sawtooth carrier intersects with the modulation wave to generate a driving signal for the primary switch tube; A frequency loop comparison unit, used for comparing the drive signal with the output limit, and determining whether the frequency loop is in a saturated state; An intermittent loop input unit, used for obtaining a second voltage difference value by subtracting the output voltage from the voltage reference value of the intermittent loop, and inputting the second voltage difference value into the PI controller of the intermittent loop to generate an output value of the PI controller; An intermittent ring comparison unit, used to compare the output value with a preset threshold value to determine whether the intermittent ring is in a saturated state; The operating condition judging unit is used to judge the operating condition of the LLC resonant converter according to whether the frequency loop and the intermittent loop are in a saturated state, thereby generating switch tube driving signals with different characteristics to realize the control of the LLC resonant converter.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

11. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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