A direct current boost grid-connected method, system, device, apparatus, medium and product

Abstract

This application provides a DC boost grid connection method, system, device, equipment, medium, and product, relating to the field of new energy grid connection. The method employs a cascaded topology of H-bridge modules to dynamically adjust the DC voltage output of the photovoltaic array according to the light intensity to match the light conditions. Simultaneously, it dynamically adjusts the number and switching times of the H-bridge modules based on the grid voltage demand, ensuring that the peak value of the multi-level AC voltage output by the adjusted H-bridge module group matches the voltage demand. Furthermore, it actively constrains the harmonic distortion rate and amplitude fluctuation rate of the output voltage to be below preset thresholds. Without requiring a power frequency boost transformer and a large-capacity inverter, it achieves direct boost grid connection from photovoltaic DC to high-voltage AC. It also solves the voltage distortion and amplitude fluctuation problems that easily occur during the dynamic adjustment of the number of modules, improving grid-connected power quality and system operational stability, and reducing the cost of the photovoltaic DC boost grid connection system.

Description

Technical Field

[0001] This application relates to the field of new energy grid connection, and in particular to a DC boost grid connection method, system, device, equipment, medium and product. Background Technology

[0002] Photovoltaic DC boost grid connection is a technology that converts the DC power generated by a photovoltaic array into high-voltage AC power and integrates it into the power grid. Distributed photovoltaic power generation is widely used in various distributed scenarios. Developing DC boost grid connection technology that can match the characteristics of new power systems and improve the grid connection performance of distributed photovoltaics is of great significance for optimizing energy resource allocation, enhancing grid resilience and flexibility, and promoting sustainable energy development.

[0003] In existing technologies, photovoltaic arrays typically output DC power, which is then boosted by a DC voltage converter and converted into electrical energy by a high-capacity inverter equipped with a power frequency transformer. The system samples the grid voltage and current to achieve phase and frequency synchronization before connecting AC power that meets grid connection standards to the grid.

[0004] However, existing technologies suffer from high costs associated with photovoltaic DC boost grid connection. Current photovoltaic DC boost grid connection solutions generally rely on power frequency transformers and large-capacity inverters. These devices are large and complex, directly increasing the overall construction and operating costs of the system and, to some extent, limiting the economic viability and large-scale application potential of photovoltaic grid-connected systems. Summary of the Invention

[0005] This application provides a DC boost grid connection method, system, device, equipment, medium, and product to solve the problem of high cost of photovoltaic DC boost grid connection in the prior art.

[0006] In a first aspect, embodiments of this application provide a DC-DC boost grid-connected method, applied to the control terminal of a DC-DC boost grid-connected system, wherein the DC-DC boost grid-connected system further includes a photovoltaic array and an H-bridge module group, and the method includes:

[0007] The DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirements of the preset power grid are obtained.

[0008] The DC voltage is adjusted according to the light intensity to match the light intensity, thereby obtaining the adjusted DC voltage.

[0009] The number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group are adjusted according to the voltage requirement to obtain an adjusted H-bridge module group. The adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirement, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below a preset threshold during the adjustment process.

[0010] The adjusted DC voltage is converted into a multi-level AC voltage that matches the voltage requirement by the adjusted H-bridge module group, and the multi-level AC voltage is connected to the preset power grid to realize the step-up grid connection of the DC power from the photovoltaic array to the AC power from the preset power grid.

[0011] In one possible design, the photovoltaic array includes multiple photovoltaic strings, and the adjustment of the DC voltage according to the illuminance to match the illuminance, resulting in an adjusted DC voltage, includes:

[0012] The ambient temperature of the environment in which the photovoltaic array is located, the output voltage and output power of each photovoltaic string, and the current voltage value of the DC side capacitor of each H-bridge module in the H-bridge module group are obtained.

[0013] Based on the output power and the light intensity, determine the target voltage value of each photovoltaic string when it reaches the preset maximum output power under the light intensity conditions;

[0014] The target voltage value is corrected by temperature compensation based on the ambient temperature to obtain the corrected target voltage value for each photovoltaic string.

[0015] Based on the deviation between the output voltage of each photovoltaic string and the corrected target voltage value of each photovoltaic string, a voltage adjustment command is generated for each photovoltaic string; wherein, the voltage adjustment command is used to adjust the preset duty cycle of the voltage regulation unit in each photovoltaic string so that the output voltage of each photovoltaic string converges to the corrected target voltage value of each photovoltaic string.

[0016] The preset duty cycle is adjusted according to the voltage adjustment command to obtain the adjusted output voltage of each photovoltaic string, and the adjusted output voltages of each photovoltaic string are combined to obtain the adjusted DC voltage.

[0017] In one possible design, the adjustment of the number of H-bridge modules and the switching timing of the H-bridge modules in the H-bridge module group according to the voltage requirement, to obtain the adjusted H-bridge module group, includes:

[0018] Obtain the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output of the H-bridge module group;

[0019] The number of modules to be put into operation and the number of modules to be bypassed are calculated based on the voltage requirement and the peak value; wherein, the number of modules to be put into operation refers to the number of H-bridge modules in the H-bridge module group that need to be put into operation, and the number of modules to be bypassed refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed.

[0020] Based on the number of modules to be deployed, multiple modules to be deployed are determined from the H-bridge modules that have not been deployed in the H-bridge module group, and multiple bypass modules to be bypassed are determined from the H-bridge modules that have been deployed in the H-bridge module group.

[0021] Based on the voltage phase and the resonant frequency, determine the activation time of each module to be activated and the bypass time of each module to be bypassed.

[0022] The input operation of each module to be input is performed according to the input time, and the bypass operation of each module to be bypassed is performed according to the bypass time, so as to obtain the adjusted H-bridge module group.

[0023] In one possible design, the step of determining multiple modules to be deployed from the H-bridge modules that have not yet been deployed in the H-bridge module group based on the number of deployed modules, and determining multiple modules to be bypassed from the H-bridge modules that have already been deployed in the H-bridge module group based on the number of bypass modules, includes:

[0024] Obtain the first real-time voltage value of the DC side capacitor of the H-bridge module that is not in the H-bridge module group, and sort the H-bridge modules that are not in the H-bridge module group in ascending order according to the deviation between the first real-time voltage value and the preset reference value, and determine the H-bridge modules that are the first number of modules in the ascending order as the plurality of modules to be put into the group.

[0025] The H-bridge modules already in the H-bridge module group are arranged in descending order based on the deviation between the current voltage value and the preset reference value, and the H-bridge modules with the highest number of bypass modules in the descending order are determined as the plurality of bypass modules.

[0026] In one possible design, the step of converting the adjusted DC voltage into a multi-level AC voltage matching the voltage requirement based on the adjusted H-bridge module group includes:

[0027] Based on a preset carrier phase-shifting PWM strategy, a PWM drive signal is generated for each H-bridge module in the H-bridge module group.

[0028] The adjusted DC voltage is input to each H-bridge module, and the switching state of multiple switches in each H-bridge module is controlled according to the PWM drive signal, so that each H-bridge module converts the adjusted DC voltage into AC voltage, and obtains the AC voltage output by each H-bridge module.

[0029] The AC voltages output by each H-bridge module are superimposed to obtain the multi-level AC voltage.

[0030] In one possible design, the step of generating PWM drive signals for each H-bridge module in the H-bridge module group based on a preset carrier phase-shift PWM strategy further includes:

[0031] Obtain the DC-side capacitor voltage of the target H-bridge module; wherein, the target H-bridge module is any one of the H-bridge modules in the H-bridge module group;

[0032] Based on the deviation between the DC-side capacitor voltage of the target H-bridge module and the preset voltage equalization reference value, a voltage equalization correction amount for the target H-bridge module is generated.

[0033] The PWM drive signal for the target H-bridge module is generated based on the preset carrier phase-shift PWM strategy and the voltage equalization correction amount.

[0034] In one possible design, after generating the PWM drive signal for the target H-bridge module based on the preset carrier phase-shift PWM strategy and the voltage equalization correction, the method further includes:

[0035] The PWM drive signal is input to the target H-bridge module to adjust the duty cycle of the switches in the target H-bridge module, so that the DC-side capacitor voltage of the target H-bridge module converges to the preset voltage equalization reference value.

[0036] If the DC-side capacitor voltage of the target H-bridge module exceeds a preset fault threshold and the duration exceeds a preset time threshold under the action of the PWM drive signal, the target H-bridge module is determined to be a permanent fault, and the target H-bridge module is bypassed and replaced by a preset backup H-bridge module.

[0037] In one possible design, integrating the multi-level AC voltage into the preset power grid includes:

[0038] Obtain the state of the preset power grid;

[0039] When the preset power grid is in a state of disturbance, the frequency and phase of the multi-level AC voltage are adjusted to obtain a stable AC voltage that is synchronized with the disturbance in the preset power grid, and the stable AC voltage is then incorporated into the preset power grid.

[0040] When the preset grid state is such that the grid voltage drops, power is released through the preset energy storage module to compensate for the voltage deviation caused by the grid voltage drop, so as to obtain an AC voltage that meets the preset grid-connected continuous operation requirements, and the AC voltage that meets the preset grid-connected continuous operation requirements is connected to the preset grid; wherein, the grid voltage drops refer to the voltage of the preset grid being lower than the preset voltage rating after a preset time period.

[0041] In one possible design, the power release via a pre-set energy storage module to compensate for voltage deviations caused by grid voltage drops, thereby obtaining an AC voltage that meets the preset requirements for continuous grid-connected operation, includes:

[0042] Obtain the magnitude and duration of the voltage drop in the power grid;

[0043] Based on the drop amplitude and the drop duration, a power allocation strategy for a preset energy storage system is generated; wherein, the energy storage system includes a capacitor and a lithium battery, the capacitor is used to provide instantaneous power compensation, and the lithium battery is used to provide continuous power compensation;

[0044] The capacitor and lithium battery are controlled to discharge according to the power distribution strategy to compensate for the voltage deviation caused by the grid voltage drop, so as to obtain an AC voltage that meets the preset requirements for continuous grid-connected operation.

[0045] Secondly, embodiments of this application provide a DC boost grid-connected system, comprising:

[0046] Photovoltaic arrays are used to output DC voltage;

[0047] The control terminal is used to acquire the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirement of the preset power grid, and adjust the DC voltage according to the light intensity to match the DC voltage with the light intensity, so as to obtain the adjusted DC voltage;

[0048] The H-bridge module group is used to adjust the number and switching time of the H-bridge modules according to the voltage requirements to obtain the adjusted H-bridge module group; wherein, the adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirements, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below a preset threshold during the adjustment process.

[0049] The control terminal is also used to convert the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement according to the adjusted H-bridge module group, and to connect the multi-level AC voltage into the preset power grid, so as to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset power grid.

[0050] Thirdly, embodiments of this application provide a DC-DC boost grid-connected device applied to the control terminal of a DC-DC boost grid-connected system, wherein the DC-DC boost grid-connected system further includes a photovoltaic array and an H-bridge module group, and the device includes:

[0051] The first acquisition module is used to acquire the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirement of the preset power grid.

[0052] The first adjustment module is used to adjust the DC voltage according to the light intensity so that the DC voltage matches the light intensity, thereby obtaining the adjusted DC voltage;

[0053] The second adjustment module is used to adjust the number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group according to the voltage requirement, so as to obtain the adjusted H-bridge module group; wherein, the adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirement, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below a preset threshold during the adjustment process.

[0054] The conversion module is used to convert the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement according to the adjusted H-bridge module group, and to connect the multi-level AC voltage into the preset power grid, so as to realize the step-up grid connection of the DC power from the photovoltaic array to the AC power from the preset power grid.

[0055] In one possible design, the photovoltaic array includes multiple photovoltaic strings, and the first adjustment module includes:

[0056] The first acquisition unit is used to acquire the ambient temperature of the environment where the photovoltaic array is located, the output voltage and output power of each photovoltaic string, and the current voltage value of the DC side capacitor of each H-bridge module in the H-bridge module group.

[0057] The first determining unit is used to determine the target voltage value of each photovoltaic string when it reaches the preset maximum output power under the light intensity condition, based on the output power and the light intensity.

[0058] The correction unit is used to perform temperature compensation correction on the target voltage value according to the ambient temperature to obtain the corrected target voltage value for each photovoltaic string.

[0059] The first generation unit is used to generate voltage adjustment instructions for each photovoltaic string based on the deviation between the output voltage of each photovoltaic string and the corrected target voltage value of each photovoltaic string; wherein, the voltage adjustment instructions are used to adjust the preset duty cycle of the voltage adjustment unit in each photovoltaic string so that the output voltage of each photovoltaic string converges to the corrected target voltage value of each photovoltaic string.

[0060] The first adjustment unit is used to adjust the preset duty cycle according to the voltage adjustment command to obtain the adjusted output voltage of each photovoltaic string, and to combine the adjusted output voltage of each photovoltaic string to obtain the adjusted DC voltage.

[0061] In one possible design, the second adjustment module includes:

[0062] The second acquisition unit is used to acquire the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group;

[0063] The first calculation unit is used to calculate the number of input modules and the number of bypass modules based on the voltage requirement and the peak value; wherein, the number of input modules refers to the number of H-bridge modules in the H-bridge module group that need to be input, and the number of bypass modules refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed;

[0064] The second determining unit is used to determine multiple modules to be put into operation from the H-bridge modules that have not been put into the H-bridge module group according to the number of the input modules, and to determine multiple modules to be bypassed from the H-bridge modules that have been put into the H-bridge module group according to the number of bypass modules.

[0065] The third determining unit is used to determine the activation time of each module to be activated and the bypass time of each module to be bypassed based on the voltage phase and the resonant frequency.

[0066] An execution unit is used to perform the input operation of each module to be input according to the input time, and to perform the bypass operation of each module to be bypassed according to the bypass time, so as to obtain the adjusted H-bridge module group.

[0067] In one possible design, the second determining unit includes:

[0068] An ascending order arrangement component is used to obtain the first real-time voltage value of the DC side capacitor of the H-bridge module that has not been put into the H-bridge module group, and to arrange the H-bridge modules that have not been put into the H-bridge module group in ascending order according to the deviation between the first real-time voltage value and the preset reference value, and to determine the H-bridge modules that are the first number of modules put into the group in the ascending order arrangement as the plurality of modules to be put into the group.

[0069] A descending order arrangement component is used to arrange the H-bridge modules already in the H-bridge module group in descending order based on the deviation between the current voltage value and the preset reference value, and to determine the H-bridge modules with the first number of bypass modules in the descending order as the plurality of bypass modules.

[0070] In one possible design, the conversion module includes:

[0071] The second generation unit is used to generate PWM drive signals for each H-bridge module in the H-bridge module group based on a preset carrier phase-shifting PWM strategy.

[0072] The input unit is used to input the adjusted DC voltage into each H-bridge module and control the switching state of multiple switches in each H-bridge module according to the PWM drive signal, so that each H-bridge module converts the adjusted DC voltage into AC voltage and obtains the AC voltage output by each H-bridge module.

[0073] The superposition unit is used to superimpose the AC voltages output by each H-bridge module to obtain the multi-level AC voltage.

[0074] In one possible design, the second generating unit includes:

[0075] The first acquisition component is used to acquire the DC-side capacitor voltage of the target H-bridge module; wherein, the target H-bridge module is any one of the H-bridge modules in the H-bridge module group;

[0076] The first generation component is used to generate a voltage equalization correction amount for the target H-bridge module based on the deviation between the DC-side capacitor voltage of the target H-bridge module and a preset voltage equalization reference value.

[0077] The second generation component is used to generate the PWM drive signal of the target H-bridge module according to the preset carrier phase-shift PWM strategy and the voltage equalization correction amount.

[0078] In one possible design, the second generating unit further includes:

[0079] An input component is used to input the PWM drive signal to the target H-bridge module to adjust the duty cycle of the switches in the target H-bridge module, so that the DC-side capacitor voltage of the target H-bridge module converges to the preset voltage equalization reference value.

[0080] The determination component is used to determine the target H-bridge module as having a permanent fault if the DC-side capacitor voltage of the target H-bridge module is greater than a preset fault threshold under the action of the PWM drive signal and the duration is greater than a preset time threshold, and to bypass the target H-bridge module and replace the target H-bridge module with a preset spare H-bridge module.

[0081] In one possible design, the conversion module includes:

[0082] The third acquisition unit is used to acquire the state of the preset power grid;

[0083] The second adjustment unit is used to adjust the frequency and phase of the multi-level AC voltage when the preset power grid is in the state of a disturbance, so as to obtain a stable AC voltage that is synchronized with the disturbance in the preset power grid, and to incorporate the stable AC voltage into the preset power grid.

[0084] The power release unit is used to release power through a preset energy storage module when the preset grid voltage drops, in order to compensate for the voltage deviation caused by the grid voltage drop, obtain an AC voltage that meets the preset requirements for continuous grid-connected operation, and integrate the AC voltage that meets the preset requirements for continuous grid-connected operation into the preset grid; wherein, the grid voltage drops refer to the voltage of the preset grid falling below the preset voltage rating after a preset time period.

[0085] In one possible design, the power release unit includes:

[0086] The second acquisition component is used to acquire the magnitude and duration of the voltage drop in the power grid.

[0087] The third generation component is used to generate a power allocation strategy for a preset energy storage system based on the drop amplitude and the drop duration; wherein the energy storage system includes a capacitor and a lithium battery, the capacitor is used to provide instantaneous power compensation, and the lithium battery is used to provide continuous power compensation.

[0088] The discharge component is used to control the capacitor and the lithium battery to discharge according to the power distribution strategy, so as to compensate for the voltage deviation caused by the grid voltage drop and obtain an AC voltage that meets the preset grid-connected continuous operation requirements.

[0089] Fourthly, embodiments of this application provide an electronic device, including: a processor, and a memory communicatively connected to the processor;

[0090] The memory stores computer-executed instructions;

[0091] When the processor executes the computer execution instructions stored in the memory, it is used to implement the DC boost grid-connected method as described in any of the first aspects.

[0092] Fifthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the DC boost grid-connected method as described in any of the first aspects.

[0093] In a sixth aspect, embodiments of this application provide a computer program product, including a computer program, which, when executed by a processor, is used to implement the DC boost grid-connected method as described in any of the first aspects.

[0094] This application provides a DC boost grid-connected method, system, device, equipment, medium, and product. By employing a cascaded topology of H-bridge modules, the DC voltage output of the photovoltaic array is dynamically adjusted at the control end according to the light intensity to match the light conditions. Simultaneously, the number and switching times of the H-bridge modules are dynamically adjusted according to the grid voltage demand, ensuring that the peak value of the multi-level AC voltage output by the adjusted H-bridge module group matches the voltage demand. Throughout the adjustment process, the harmonic distortion rate and amplitude fluctuation rate of the output voltage are actively constrained to be below preset thresholds. Without the need for a power frequency boost transformer and a large-capacity inverter, direct boost grid connection from photovoltaic DC to high-voltage AC is achieved. From a hardware architecture perspective, this eliminates the burden of volume, cost, and structural complexity brought by transformers and large inverters. It also solves the voltage distortion and amplitude fluctuation problems that easily occur during the dynamic adjustment of the number of modules, improves the grid-connected power quality and system operation stability, and reduces the cost of the photovoltaic DC boost grid-connected system. Attached Figure Description

[0095] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0096] Figure 1 This is a schematic diagram illustrating an application scenario of the DC boost grid connection method provided in the embodiments of this application;

[0097] Figure 2 A flowchart illustrating the DC boost grid-connected method provided in the embodiments of this application. Figure 1 ;

[0098] Figure 3 A flowchart illustrating the DC boost grid-connected method provided in the embodiments of this application. Figure 2 ;

[0099] Figure 4 This is a schematic diagram of the system topology for the traditional AC access method of rural distributed photovoltaic power generation, provided in an embodiment of this application.

[0100] Figure 5 This application provides an embodiment of a three-phase cascaded H-bridge photovoltaic DC boost grid-connected system architecture diagram.

[0101] Figure 6 The circuit schematic diagram of the H-bridge cascade module provided in the embodiments of this application;

[0102] Figure 7 A schematic diagram of the cascading of H-bridge cascading modules provided in the embodiments of this application;

[0103] Figure 8 A schematic diagram of a three-level H-bridge cascade module and its cascade provided in the embodiments of this application;

[0104] Figure 9 A circuit diagram of the H-bridge cascade module with T-type three-level circuit provided in the embodiments of this application;

[0105] Figure 10 Control logic block diagram of the H-bridge cascaded grid system provided in the embodiments of this application;

[0106] Figure 11 This is a schematic diagram of the structure of the DC boost grid-connected device provided in the embodiments of this application;

[0107] Figure 12 This is a schematic diagram of the hardware structure of the electronic device provided in the embodiments of this application.

[0108] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0109] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0110] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of the relevant data must comply with relevant laws, regulations and standards, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0111] In the embodiments of this application, the terms "first" and "second" are used to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that "first" and "second" do not necessarily imply difference. It should be noted that in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design scheme described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner. In the embodiments of this application, "at least one" refers to one or more, and "more than one" refers to two or more.

[0112] It should be noted that the phrase "at...time" in the embodiments of this application can refer to the instant at which a certain situation occurs, or to a period of time after the occurrence of a certain situation. The embodiments of this application do not specifically limit this. In addition, the DC boost grid-connected method, apparatus, equipment, medium and product provided in the embodiments of this application are only examples. A DC boost grid-connected method, apparatus, equipment, medium and product may also include more or fewer contents.

[0113] To facilitate a clear description of the technical solutions in the embodiments of this application, some terms and technologies involved in the embodiments of this application will be briefly introduced below:

[0114] H-bridge module group: This is a power conversion unit composed of multiple H-bridge power modules connected in series on the AC side. Each H-bridge module is independently configured with a DC-side capacitor and four switching devices, which can convert the input DC voltage into a positive and negative AC square wave with controllable amplitude. The AC voltages output by each module are superimposed on the output side to synthesize a high-voltage multi-level stepped waveform. This module group adapts to different grid voltage levels by dynamically adjusting the number of modules in operation, and achieves fault isolation and online maintenance based on a modular redundancy structure. It is the core execution component in this application for replacing the power frequency transformer to realize direct DC to high-voltage AC grid connection.

[0115] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0116] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0117] To clearly understand the technical solution of this application, the existing technology solutions will first be described in detail. Photovoltaic DC boost grid connection is a technology that converts the DC power generated by a photovoltaic array into high-voltage AC power and integrates it into the power grid. Distributed photovoltaic power generation is widely used in various distributed scenarios. Developing DC boost grid connection technology that can match the characteristics of new power systems and improve the grid connection performance of distributed photovoltaics is of great significance for optimizing energy resource allocation, enhancing grid resilience and flexibility, and promoting sustainable energy development.

[0118] In existing technologies, photovoltaic arrays typically output direct current (DC), which is then boosted through a DC-DC converter and converted into electrical energy by a large-capacity inverter equipped with a power frequency transformer. The system synchronizes phase and frequency by sampling the grid voltage and current before connecting AC power that meets grid connection standards to the grid. Existing photovoltaic DC-DC boost grid-connected solutions generally rely on power frequency transformers and large-capacity inverters. These devices are large and complex, directly increasing the overall construction and operating costs of the system and limiting the economic viability and large-scale application of photovoltaic grid-connected systems to some extent. Therefore, existing technologies suffer from high costs associated with photovoltaic DC-DC boost grid-connected systems.

[0119] Therefore, addressing the high cost of photovoltaic DC boost grid connection in existing technologies, this research found that a modular multilevel cascaded topology can be adopted to solve this problem. By dynamically adjusting the DC-side voltage and the number of modules on the AC side, high-voltage AC grid connection can be directly achieved without a power frequency transformer: ① The DC output voltage on the photovoltaic side can be adaptively adjusted according to the light intensity, and the number of power conversion units can be dynamically configured according to the grid voltage demand. This completes the DC-to-high-voltage AC power conversion and grid connection without relying on a power frequency transformer and a large-capacity inverter, reducing system cost and size from a hardware architecture perspective. ② A modular cascaded power conversion topology can be adopted. By adjusting the DC input voltage according to light intensity and dynamically combining the conversion units according to voltage adaptation, the photovoltaic DC power can be directly boosted to high-voltage AC power that meets grid requirements for grid connection, eliminating the need for traditional high-power inverters and transformers, thus improving system economy. ③ A coordinated control mechanism can be established between lighting conditions and DC voltage, grid voltage and the number of conversion units, so as to complete the integrated output of DC boost and AC grid connection with a lightweight, transformerless distributed conversion structure, simplifying the system structure and reducing the overall construction and operation costs.

[0120] Specifically, a cascaded multilevel converter architecture can be adopted. By dynamically adapting and adjusting the DC-side voltage according to the light intensity, and dynamically adjusting the number of cascaded units participating in level synthesis on the AC side according to the grid voltage demand, the converter can directly output high-voltage AC power that matches the grid voltage, thereby achieving direct DC to high-voltage AC grid connection without the need for a power frequency transformer and a large-capacity inverter.

[0121] This application discloses a DC boost grid-connected method, system, device, equipment, medium, and product. By employing a cascaded topology of H-bridge modules, the DC voltage output of the photovoltaic array is dynamically adjusted at the control end according to the light intensity to match the light conditions. Simultaneously, the number and switching times of the H-bridge modules are dynamically adjusted according to the grid voltage demand, ensuring that the peak value of the multi-level AC voltage output by the adjusted H-bridge module group matches the voltage demand. Throughout the adjustment process, the harmonic distortion rate and amplitude fluctuation rate of the output voltage are actively constrained to be below preset thresholds. Without the need for a power frequency boost transformer and a large-capacity inverter, direct boost grid connection from photovoltaic DC to high-voltage AC is achieved. This eliminates the burden of volume, cost, and structural complexity associated with transformers and large inverters at the hardware architecture level. It also solves the voltage distortion and amplitude fluctuation problems that easily occur during the dynamic adjustment of the number of modules, improving the grid-connected power quality and system operational stability, and reducing the cost of the photovoltaic DC boost grid-connected system.

[0122] Based on the above-mentioned inventive discovery, the technical solution of this application is proposed.

[0123] The following describes the application scenarios of the DC boost grid connection method provided in the embodiments of the present invention. Figure 1 This is a schematic diagram illustrating an application scenario of the DC boost grid-connected method provided in the embodiments of this application. For example... Figure 1 As shown, the application scenario includes a photovoltaic array 101, an H-bridge module group 102, a control terminal 103, and a power grid 104. The control terminal 103 acquires the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the preset voltage requirement of the power grid. The control terminal 103 adjusts the DC voltage according to the light intensity to match the light intensity, thus obtaining an adjusted DC voltage. The control terminal 103 adjusts the number of H-bridge modules in the H-bridge module group according to the voltage requirement, thus obtaining an adjusted H-bridge module group. The control terminal 103 converts the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement based on the adjusted H-bridge module group, and connects the multi-level AC voltage to the power grid 104 to realize the step-up and grid connection of the DC power from the photovoltaic array to the AC power from the power grid 104.

[0124] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0125] Figure 2A flowchart illustrating the DC boost grid-connected method provided in the embodiments of this application. Figure 1 .like Figure 2 As shown, in this embodiment, the execution entity of this invention is the control terminal. Therefore, the DC boost grid-connected method provided in this embodiment includes the following steps:

[0126] S201. Obtain the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirements of the preset power grid.

[0127] Specifically, a voltage sampling circuit can be directly electrically connected to the output of the photovoltaic array to collect the DC voltage signal output by the photovoltaic array in real time and transmit it to the control terminal. A light sensor is placed in the environment where the photovoltaic array is located and electrically connected to the control terminal to obtain the current light intensity value of the environment. Through electrical connection with the signal interface of the grid side, the voltage parameters specified by the grid side are read as the preset grid voltage requirement. This step is used to provide input basis for subsequent DC voltage adjustment and H-bridge module number adjustment, ensuring that the power conversion and grid connection operations can be stably executed.

[0128] S202. Adjust the DC voltage according to the light intensity to match the light intensity, and obtain the adjusted DC voltage.

[0129] Specifically, a DC voltage regulation unit can be set between the photovoltaic array and the H-bridge module group. One end of the DC voltage regulation unit is electrically connected to the output terminal of the photovoltaic array, and the other end is electrically connected to the input terminal of the H-bridge module group. The control terminal changes the duty cycle of the switching devices inside the DC voltage regulation unit according to the light intensity to adjust the amplitude of the DC voltage output by the photovoltaic array and stabilize the DC voltage at a level corresponding to the current light intensity, thus obtaining the adjusted DC voltage. This step is used to make the DC voltage output by the photovoltaic array compatible with the current light conditions, providing a stable and matched DC input for subsequent multi-level AC voltage conversion.

[0130] Matching the DC voltage to the light intensity means that the control unit adjusts the DC voltage output by the photovoltaic array to a value suitable for the current light intensity. This ensures the photovoltaic array operates within a suitable voltage range under the current light conditions, guaranteeing a stable output of electrical energy corresponding to the light intensity, rather than operating at excessively high or low voltage levels. For example, in environments with strong light intensity, the photovoltaic array has a higher power generation capacity, so the control unit adjusts the DC voltage to a higher suitable value to match the output capacity corresponding to strong light. In environments with weak light intensity, the photovoltaic array has a lower power generation capacity, so the control unit adjusts the DC voltage to a lower suitable value to match the output capacity corresponding to weak light, ensuring that the DC voltage level always remains consistent with the power generation state supported by the current light intensity.

[0131] S203. Adjust the number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group according to the voltage requirements to obtain the adjusted H-bridge module group; wherein, the adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirements, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below the preset threshold during the adjustment process.

[0132] Specifically, the number of H-bridge modules required to reach the desired peak voltage can be calculated based on the preset voltage demand of the power grid. By acquiring the current voltage value of the DC-side capacitor of each H-bridge module in the H-bridge module group in real time, modules with lower current voltage values ​​are prioritized for activation to balance the energy of each module, while modules with higher current voltage values ​​are prioritized for bypass. Combined with the preset voltage phase of the power grid and the resonant frequency of the output filter circuit, the activation and bypass timing of each module is accurately calculated, so that each module completes the switching action near the voltage zero crossing point. In the process of dynamically adjusting the number of modules to match the voltage demand, voltage jumps and shocks caused by switching actions are suppressed, and the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage are controlled below the preset threshold. This step is used to dynamically adjust the number of H-bridge modules involved in the operation and their switching sequence to ensure that the peak value of the output multi-level AC voltage accurately matches the power grid demand, and to ensure the stability of the power quality of the output voltage during the adjustment process.

[0133] For example, assuming the preset grid voltage requirement is 10kV, the H-bridge module group consists of 50 H-bridge modules connected in series. Each module's DC-side capacitor voltage is stable at 200V, ideally outputting a peak voltage of 200V × 50 = 10kV. When a sudden drop in sunlight intensity causes a significant reduction in the photovoltaic array's output power, the DC-side capacitor voltage of some modules drops to 180V. To match the 10kV voltage requirement, the control unit calculates in real-time that 56 modules (56 × 180V ≈ 10kV) are needed to meet the peak voltage requirement. At this point, the control terminal prioritizes selecting the six modules with the lowest DC-side capacitor voltage values ​​from the bypassed modules. Assuming their voltages are 172V, 175V, 177V, 178V, 179V, and 180V respectively, these are selected as modules to be put into operation to ensure energy balance. Simultaneously, from the modules already in the H-bridge module group, the six modules with the highest current voltage values ​​are selected. Assuming their voltages are 198V, 197V, 196V, 195V, 194V, and 193V respectively, these are selected as modules to be bypassed. The control terminal also detects in real-time that the current grid voltage phase is 45° and the resonant frequency of the output filter circuit is 350Hz. To avoid voltage spikes and harmonics during switching, calculations show that modules to be put into operation should be switched in synchronously when the grid voltage phase reaches 50°, and modules to be bypassed should be switched out synchronously when the grid voltage phase reaches 40°. By precisely controlling the switching of these 12 modules at specified times, the peak value of the multi-level AC voltage actually output by the H-bridge module group is stabilized within the range of 9.98kV to 10.02kV. The harmonic distortion rate is controlled at 2.8% and the amplitude fluctuation rate is controlled at 1.5%, both lower than the preset thresholds of 3% and 2%, respectively. This achieves the matching of output voltage quality with grid demand under power fluctuation scenarios.

[0134] The switching time refers to the specific point in time when the control terminal sends a switching command or bypass command to a specific H-bridge module during dynamic adjustment of the H-bridge module group. The selection of this time point is not arbitrary, but needs to be calculated based on the phase information of the current grid voltage and the electrical characteristics of the output filter circuit. Its goal is to ensure that the module completes the action near the voltage zero crossing point or current zero crossing point, thereby reducing the impact on the output voltage waveform caused by the change of module state.

[0135] Harmonic distortion rate is a key indicator for measuring the quality of multi-level AC voltage waveforms. It quantifies the deviation between the actual output voltage waveform and the ideal sine wave. It is the ratio of the effective value of all harmonic components to the effective value of the fundamental component in the voltage waveform. The lower this ratio, the closer the waveform is to a pure sine wave, and the higher the power quality. During the switching process of H-bridge modules, improper control can generate additional harmonic components, leading to an increase in harmonic distortion rate.

[0136] Amplitude fluctuation rate describes the stability of the peak value of a multi-level AC voltage during dynamic adjustment. It is typically defined as the percentage of the maximum fluctuation of the actual peak voltage relative to the target peak value within a specific time window. When adding or bypassing an H-bridge module, if the energy switching is not smooth, it may cause a brief increase or decrease in the output voltage amplitude. This metric is used to quantify the magnitude of this fluctuation, ensuring the stability of the voltage output.

[0137] Both harmonic distortion rate and amplitude fluctuation rate are below the preset threshold. This means that during the actual control process, the harmonic distortion rate of the multi-level AC voltage output by the H-bridge module group must be less than the preset upper limit of the harmonic distortion rate, and the amplitude fluctuation rate must also be less than the preset upper limit of the amplitude fluctuation rate. Both of these indicators must be met simultaneously to ensure that the output voltage maintains both the sinusoidal waveform and the stability of the amplitude during the dynamic adjustment of the number of modules and the switching time, thereby achieving high-quality power grid connection.

[0138] S204. Based on the adjusted H-bridge module group, the adjusted DC voltage is converted into a multi-level AC voltage that matches the voltage requirement, and the multi-level AC voltage is connected to the preset grid to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset grid.

[0139] Specifically, the adjusted DC voltage can be input into the H-bridge module group that has completed the quantity adjustment. Each H-bridge module sequentially performs level conversion and phase switching on the input DC voltage to form a multi-level stepped AC level signal. This AC level signal is processed by the filter circuit electrically connected to the output terminal of the H-bridge module group and then directly connected to the power grid, completing the DC to AC conversion and grid connection. This step is used to complete the step-up conversion and grid connection of photovoltaic DC to grid AC without connecting to the power frequency transformer and large-capacity inverter.

[0140] This application can be applied to rural photovoltaic power generation scenarios. Addressing the pain points of weak power grid structure, high line loss, high cost and complex maintenance of traditional transformer-type grid-connected equipment in rural areas, it adopts the technical advantages of cascaded H-bridge direct voltage boosting, no power frequency transformer, and modular expansion. It can significantly reduce equipment investment costs and line losses, while supporting small-capacity start-up and batch expansion. It can improve the power generation efficiency and long-term operational reliability of the power station, help the inclusive implementation of clean energy in rural areas, and provide an efficient, low-cost, and easy-to-maintain grid connection solution for rural photovoltaic power generation scenarios.

[0141] This application demonstrates strong adaptability and application value in the construction of microgrids in remote areas. Remote mountainous regions and islands are often far from the main power grid, with long power supply radii, poor construction conditions, and insufficient operation and maintenance capabilities. Traditional medium-voltage grid-connected solutions are difficult to construct and economically inefficient. This DC boost grid-connected system enables direct cascading boosting of photovoltaic DC power and stable integration into the microgrid. Combined with low-voltage ride-through and virtual synchronization control capabilities, it effectively improves the voltage and frequency stability of the microgrid. Furthermore, the equipment features a simple structure, high reliability, and adaptability to harsh environments. It can provide stable, efficient, and lightweight photovoltaic grid-connected support for independent microgrids and on-grid / off-grid switching microgrids in remote areas, contributing to stable power supply and energy self-sufficiency in these regions.

[0142] This embodiment provides a DC boost grid connection method that employs a cascaded topology of H-bridge modules. At the control end, the DC voltage output of the photovoltaic array is dynamically adjusted according to the light intensity to match the light conditions. Simultaneously, the number and switching times of the H-bridge modules are dynamically adjusted according to the grid voltage demand. This ensures that the peak value of the multi-level AC voltage output by the adjusted H-bridge module group matches the voltage demand. Throughout the adjustment process, the harmonic distortion rate and amplitude fluctuation rate of the output voltage are actively constrained to be below preset thresholds. Without requiring a power frequency boost transformer and a large-capacity inverter, this method achieves direct boost grid connection from photovoltaic DC to high-voltage AC. From a hardware architecture perspective, it eliminates the burden of size, cost, and structural complexity associated with transformers and large inverters. It also solves the voltage distortion and amplitude fluctuation problems that easily occur during the dynamic adjustment of the number of modules, improving grid-connected power quality and system operational stability, and reducing the cost of the photovoltaic DC boost grid connection system.

[0143] In one possible design, the photovoltaic array includes multiple photovoltaic strings. S202, adjusting the DC voltage according to the light intensity to match the light intensity, resulting in an adjusted DC voltage, includes:

[0144] S2021. Obtain the ambient temperature of the photovoltaic array, the output voltage and output power of each photovoltaic string, and the current voltage value of the DC side capacitor of each H-bridge module in the H-bridge module group.

[0145] Specifically, a high-precision temperature sensor can be mounted on the backplane surface of the photovoltaic array. Ambient temperature data can be collected in real time through an analog input module. Voltage Hall sensors and current Hall sensors are connected in parallel at the output terminals of each photovoltaic string. The output voltage and output power of each photovoltaic string are obtained in real time through a signal conditioning circuit and an analog-to-digital converter sampling module. In the H-bridge module group, a voltage detection circuit is connected in parallel across the DC-side capacitor of each H-bridge module. The capacitor voltage signal is transmitted to the digital signal processor at the control terminal through an isolation amplifier to obtain the current voltage value of the DC-side capacitor of each H-bridge module in real time. This step is used to provide real-time ambient temperature parameters, electrical operation data of each photovoltaic string, and energy state data of each H-bridge module for subsequent DC voltage adjustment, serving as the input basis for voltage adjustment command generation and module equalization control.

[0146] S2022. Based on the output power and light intensity, determine the target voltage value of each photovoltaic string when it reaches the preset maximum output power under the light intensity conditions.

[0147] Specifically, each photovoltaic (PV) string can be tested in advance, and the output voltage data corresponding to different output powers under different light intensity levels can be recorded. After organizing this data, a correspondence table between light intensity, output power, and output voltage can be established. In actual operation, the current output power of each PV string and the light intensity of the environment can be obtained in real time. Based on these two parameters and referring to the table, the voltage value that matches the current output power under the current light intensity and allows the PV string to reach the preset maximum output power can be found. This voltage value is determined as the target voltage value for each PV string. This step is used to provide a clear benchmark for the subsequent adjustment of the PV string output voltage, ensuring that each PV string can output the preset maximum output power under the current light conditions, and providing a stable voltage foundation for subsequent DC voltage adjustment and grid connection.

[0148] For example, photovoltaic power plant operation and maintenance personnel conduct calibration tests on a certain type of photovoltaic string, at a light intensity of 200... 400 600 800 and 1000 Under these conditions, the output power of each string was recorded until it reached its preset maximum output power, and a table comparing light intensity, output power, and maximum power point voltage was created based on this data. On a certain day during actual operation, the control terminal collected real-time data showing that the current light intensity of one string was 820... The output power is 245W, and the control terminal immediately uses 820 Using 245W as an index, the corresponding voltage value of 68.5V is found in this lookup table using linear interpolation, thus obtaining the target voltage value for this string to reach the preset maximum output power under the current operating conditions.

[0149] The maximum output power refers to the maximum electrical power that a photovoltaic string can output under the current light intensity and temperature conditions. This value increases with increasing light intensity and decreases with increasing temperature. For example, a photovoltaic string with a nominal maximum output power of 300W will output more power under 1000W light intensity. Under standard test conditions at a temperature of 25℃, its maximum output power is 300W.

[0150] The target voltage value at maximum output power refers to the DC voltage value between the positive and negative output terminals of the photovoltaic string when it reaches its maximum power point. This voltage value will shift with changes in operating conditions. For example, for the 300W photovoltaic string mentioned above, at 1000... At 25℃, its maximum power point voltage is likely 36V, and when the light intensity drops to 600... When the temperature rises to 40℃, its maximum power point voltage may drop to 32V. The control terminal needs to adjust the string output voltage to this target value of 32V in order to extract the maximum power that can be obtained under the current operating conditions from the string.

[0151] The illuminance-output power-maximum power point voltage (MPPTV) table is a pre-calibrated three-dimensional data mapping table. It uses illuminance and output power as two input dimensions, recording the voltage value corresponding to the photovoltaic string reaching its maximum power output under these two conditions. For example, it measures the voltage value of a photovoltaic string at an illuminance of 800 kDa at maximum power point. When the output power is 240W, its maximum power point voltage is 68.5V, and the illuminance is 600 lux. When the output power is 180W, its maximum power point voltage is 65.2V. After organizing these data points into a table, in actual operation, you only need to input the real-time collected light intensity and output power to quickly find the corresponding target voltage value.

[0152] S2023. Perform temperature compensation correction on the target voltage value based on the ambient temperature to obtain the corrected target voltage value for each photovoltaic string.

[0153] Specifically, the open-circuit voltage temperature coefficient marked in the photovoltaic module's factory parameters can be read. This coefficient represents the percentage decrease in open-circuit voltage for every 1°C increase in temperature. The difference between the current ambient temperature and the standard test temperature of 25°C is multiplied by this temperature coefficient, and then multiplied by the target voltage value determined based on the light intensity to calculate the voltage deviation caused by the temperature change. Finally, this deviation is subtracted from the target voltage value to obtain the corrected target voltage value for each photovoltaic string after temperature compensation. This step is used to eliminate the influence of ambient temperature changes on the output voltage characteristics of photovoltaic modules, making the corrected target voltage value closer to the true maximum power point voltage under the current actual operating conditions.

[0154] For example, in the actual operation of a photovoltaic power station, the control terminal collected real-time data at 2 PM showing an ambient temperature of 38 degrees Celsius. The open-circuit voltage temperature coefficient specified in the photovoltaic module's factory specifications is -0.32. Prior to this, the target voltage value determined by the control unit based on the light intensity was 72.5V, which corresponds to a standard test temperature of 25°C. The maximum power point voltage is calculated by the control terminal first, which calculates the difference between the current temperature and the standard temperature: 38. -25 =13 Then, the voltage correction is calculated based on the temperature coefficient: 72.5V × 0.32% × 13 = 72.5V × 0.0416 ≈ 3.02V. Finally, the target voltage value is subtracted from the correction: 72.5V - 3.02V = 69.48V, thus obtaining the corrected target voltage value of 69.48V.

[0155] Temperature compensation correction refers to adjusting the previously determined target voltage value by adding or subtracting based on the difference between the real-time ambient temperature and the standard reference temperature (usually 25°C) and the inherent temperature characteristics of the photovoltaic module. Since the output voltage of the photovoltaic module decreases as the temperature rises and increases as the temperature falls, this correction process can offset the voltage deviation caused by temperature changes, so that the corrected voltage value always corresponds to the appropriate operating point at the current actual temperature.

[0156] The open-circuit voltage temperature coefficient is a key manufacturing parameter for photovoltaic modules. It is usually expressed as a negative number, such as -0.32% / ℃. It quantifies the percentage change in the open-circuit voltage of the module when the temperature changes by 1 degree Celsius. This coefficient reflects the sensitivity of photovoltaic materials to temperature. That is, when the temperature rises, the maximum voltage that can be generated across the module will decrease by this proportion. It is an indispensable data for temperature compensation correction calculations.

[0157] S2024. Based on the deviation between the output voltage of each photovoltaic string and the corrected target voltage value of each photovoltaic string, generate a voltage adjustment command for each photovoltaic string; wherein, the voltage adjustment command is used to adjust the preset duty cycle of the voltage adjustment unit in each photovoltaic string so that the output voltage of each photovoltaic string converges to the corrected target voltage value of each photovoltaic string.

[0158] Specifically, a comparator unit and a proportional-integral (PI) controller unit can be integrated into the digital signal processor (DSP) at the control end via hardware logic circuitry. The real-time acquired output voltage of each photovoltaic (PV) string and the target voltage value after temperature compensation correction are simultaneously input to the comparator unit. The difference between the two is calculated as the voltage deviation. This deviation is then sent to the PPI controller unit, which calculates the deviation based on a preset proportional coefficient and integral time constant, outputting a duty cycle adjustment value. Finally, the duty cycle adjustment value is converted into a corresponding pulse-width modulation (PWM) waveform, which is sent as a voltage adjustment command to the switching transistor driver of the Boost converter in each PV string. This step converts the voltage deviation into a specific switching transistor drive signal, driving the converter to change its operating state and causing the output voltage of the PV string to converge towards the corrected target voltage value.

[0159] For example, in the actual operation of a photovoltaic power station, the control terminal collects the current output voltage of the photovoltaic string in real time as 64.2V, while the target voltage value of the string after temperature compensation correction is 69.5V. The hardware comparator unit inside the control terminal first compares these two voltage values ​​and calculates the difference as 5.3V, indicating that the current voltage is lower than the target value of 5.3V. This 5.3V voltage deviation is sent to the subsequent proportional-integral controller hardware unit, which has a preset proportional coefficient of 0.2 and an integral time constant of 0.05 seconds. The proportional-integral controller calculates the input 5.3V deviation: first, the proportional part outputs an instantaneous response of 5.3V × 0.2 = 1.06V, and at the same time, the integral part calculates the cumulative deviation over the past 0.05 seconds. After the two parts are superimposed, a duty cycle adjustment value of 0.08 is finally output, indicating that the duty cycle of the current switching transistor needs to be increased by 0.08. After receiving the adjustment value of 0.08, the pulse width modulation generator at the control end immediately adjusts the comparison threshold of its internal counter to generate a new set of pulse width modulation waveforms. This waveform is then sent via optical fiber to the switching transistor drive circuit of the string Boost converter as a voltage adjustment command. This drives the switching transistors to increase their on-time, thereby gradually increasing the output voltage from 64.2V to the target value of 69.5V.

[0160] In each photovoltaic string, the Boost converter is a DC-DC boost power conversion circuit, typically composed of an energy storage inductor, a switching transistor, a diode, and an output capacitor. The voltage conversion relationship between the input and output is adjusted by controlling the switching transistor's on and off states. When the switching transistor is on, the energy storage inductor stores energy. When the switching transistor is off, the energy stored in the inductor, combined with the input voltage, is released to the output capacitor through the diode, thus achieving a boost function where the output voltage is higher than the input voltage. The boost ratio is determined by the duty cycle of the switching transistor's drive pulse.

[0161] S2025. Adjust the preset duty cycle according to the voltage adjustment command to obtain the adjusted output voltage of each photovoltaic string, and combine the adjusted output voltage of each photovoltaic string to obtain the adjusted DC voltage.

[0162] Specifically, the duty cycle adjustment value carried in the voltage adjustment command can be input to the pulse width modulation (PWM) waveform generator of each photovoltaic string Boost converter. The PWM waveform generator updates the comparison value of its internal counter accordingly, thereby changing the drive pulse width output to the insulated gate bipolar transistor, achieving precise adjustment of the duty cycle. By adjusting the duty cycle, the voltage conversion ratio of the Boost converter is changed, so that the actual output voltage of each photovoltaic string follows the command change, and finally the adjusted output voltage is obtained. Then, the adjusted output voltages of all photovoltaic strings are connected in parallel through a DC bus to obtain the adjusted DC voltage at the output of the bus. This step is used to actually perform voltage regulation by physically changing the conduction time of the power switch, and to gather the regulated power of multiple strings into a unified DC source to provide the required input voltage for the subsequent H-bridge module group.

[0163] For example, in the actual operation of a photovoltaic power station, the control terminal sends a voltage adjustment command to the Boost converter of the photovoltaic string, requiring an increase in the duty cycle of 0.08. Upon receiving the command, the PWM waveform generator of the converter adjusts the comparison value of its internal counter from 600 to 648. Assuming a counter period of 1000, this corresponds to an increase in the duty cycle from 0.60 to 0.648, thereby adjusting the drive pulse width of the insulated gate bipolar transistor from 60% on-time to 64.8% on-time. Through this duty cycle adjustment, the voltage conversion ratio of the Boost converter changes accordingly, causing the output voltage of the photovoltaic string to gradually rise from 64.2V before adjustment and stabilize at 69.5V, obtaining the adjusted output voltage. These adjusted output voltages are connected in parallel to the DC bus via anti-reverse diodes of each group. The adjusted DC voltage measured at the bus output is 69.3V, which is the unified DC input provided to the subsequent H-bridge module group after the bus is connected.

[0164] The technical effect of this solution in this embodiment is as follows: By acquiring the ambient temperature, the output voltage and output power of each photovoltaic string, and the current voltage value of the DC-side capacitor of the H-bridge module, the maximum power point target voltage of each photovoltaic string under illumination conditions is first determined based on the output power and light intensity. Then, temperature compensation is applied to eliminate the influence of ambient temperature on the output voltage of the photovoltaic module. Finally, a voltage adjustment command is generated based on the deviation between the output voltage of each photovoltaic string and the corrected target voltage, so that each photovoltaic string independently converges to the optimal voltage point under its current conditions, thereby obtaining a DC voltage that accurately matches the illumination and temperature conditions. This solves the problem of power generation efficiency loss caused by the photovoltaic DC voltage adjustment in the prior art only considering the light intensity and ignoring the influence of temperature and the differences between strings, and improves the overall power generation efficiency of the photovoltaic array in complex environments.

[0165] In one possible design, S203 adjusts the number of H-bridge modules and the switching timing of the H-bridge modules in the H-bridge module group according to voltage requirements, resulting in an adjusted H-bridge module group, including:

[0166] S2031. Obtain the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group.

[0167] Specifically, a voltage transformer can be connected in parallel at the grid connection point of the H-bridge module group and the preset grid. After the grid voltage is stepped down and isolated, it is input to the zero-crossing comparator circuit. The zero-crossing comparator outputs a square wave signal to the capture unit at the control end. The capture unit records the time of the rising edge of the square wave and calculates the time interval between adjacent rising edges, thereby obtaining the voltage phase of the preset grid in real time. At the same time, the resonant frequency value calculated based on the inductance value of the output filter inductor and the capacitance value of the filter capacitor is pre-written into the memory at the control end. In actual operation, the resonant frequency of the output filter circuit of the H-bridge module group can be obtained by directly reading this pre-stored value. This step is used to provide the real-time phase reference point of the grid voltage and the inherent electrical parameters of the filter circuit for subsequent determination of the connection and bypass time of each H-bridge module, ensuring that the switching action is performed at the appropriate time.

[0168] The resonant frequency refers to the inherent frequency of the filter circuit connected to the output of the H-bridge module group in terms of electrical characteristics. It is determined by the inductance of the filter inductor and the capacitance of the filter capacitor. When the current flowing through the inductor and the capacitor are in phase, the circuit will resonate. At this time, the impedance of the filter circuit to a specific frequency signal is at its minimum or maximum. In module switching control, accurately determining this frequency value can help determine the appropriate action time to avoid oscillation of the output voltage waveform caused by resonance triggered by the switching action.

[0169] S2032. Calculate the number of modules to be put into operation and the number of modules to be bypassed based on voltage requirements and peak values; where the number of modules to be put into operation refers to the number of H-bridge modules in the H-bridge module group that need to be put into operation, and the number of modules to be bypassed refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed.

[0170] Specifically, based on the preset voltage demand of the power grid, the peak voltage value is taken as the target output voltage value. Then, the average voltage value of the DC-side capacitor of each H-bridge module is obtained as the contribution voltage of a single module. The target output voltage value is then divided by the contribution voltage of a single module and rounded up to calculate the total number of modules required to reach the voltage peak. This total number is compared with the number of modules currently in operation. If the total number is greater than the current number of modules in operation, the difference is the number of modules that need to be added. If the total number is less than the current number of modules in operation, the difference is the number of bypass modules that need to be reduced. This step is used to calculate the specific number of modules that need to be adjusted in the H-bridge module group at the current moment so that the total number of modules in operation after adjustment can synthesize an output voltage peak that matches the voltage demand of the power grid.

[0171] For example, in a high-voltage direct current (HVDC) boost grid-connected system, the preset grid voltage requirement is 10kV, meaning the peak value of the multi-level AC voltage output by the H-bridge module group is required to be 10kV. The control terminal collects the average voltage value of the DC-side capacitors of all currently engaged H-bridge modules in real time, which is 185V, and uses this as the contribution voltage of a single module. The control terminal calculates: 10kV ÷ 185V ≈ 54.05, rounding up to find that a total of 55 modules are needed to reach this voltage peak. At this point, the control terminal detects that the actual number of modules currently engaged is 50. Comparing the required total of 55 modules with the current number of 50 modules, the difference is found to be 5. Therefore, it is determined that 5 more modules need to be added this time, and since there is no over-limit, the number of modules that need to be bypassed is 0.

[0172] S2033. Based on the number of modules to be deployed, determine multiple modules to be deployed from the H-bridge modules that have not been deployed into the H-bridge module group, and based on the number of bypass modules, determine multiple modules to be bypassed from the H-bridge modules that have been deployed into the H-bridge module group.

[0173] Specifically, the real-time voltage values ​​of the DC-side capacitors of each H-bridge module in the unused H-bridge module group can be obtained first. These voltage values ​​are then compared with a preset reference voltage value to calculate the voltage deviation of each module. All unused modules are then sorted in ascending order of deviation, and the modules at the top of the list, whose number equals the number of used modules, are identified as modules to be used. Simultaneously, the real-time voltage values ​​of the DC-side capacitors of each used H-bridge module in the used H-bridge module group are obtained, and the deviations are again compared with the preset reference voltage value to calculate. All used modules are then sorted in descending order of deviation, and the modules at the top of the list, whose number equals the number of bypass modules, are identified as modules to be bypassed. This step is used to accurately select the modules that most need to be used and bypassed from all available H-bridge modules. By prioritizing the use of modules with lower voltages and prioritizing the bypass of modules with higher voltages, a balanced energy distribution among the modules is achieved.

[0174] For example, in a DC boost grid-connected system, the control terminal calculates that two additional modules need to be put into operation, and no bypass modules are required. At this time, there are eight modules available in the unoperated H-bridge module group. The control terminal obtains the current voltage values ​​of the DC-side capacitors of these eight modules in real time, which are 172V, 183V, 177V, 192V, 179V, 188V, 195V, and 176V, respectively, with a preset reference voltage value of 185V. The control terminal calculates the deviation of each module's voltage value from the reference value and sorts them in ascending order of deviation, i.e., from low to high voltage. The sorted voltage sequence is 172V, 176V, 177V, 179V, 183V, 188V, 192V, and 195V. The first two modules are those with voltages of 172V and 176V, so these two modules are identified as modules to be put into operation. Since no bypass modules are required in this case, no screening of bypass modules is performed.

[0175] S2034. Based on the voltage phase and resonant frequency, determine the activation time of each module to be activated and the bypass time of each module to be bypassed.

[0176] Specifically, based on the real-time acquired grid voltage phase information, the specific phase angle of the zero-crossing point of the voltage value within a complete voltage cycle can be determined, such as 0° and 180°. Simultaneously, combined with the pre-acquired resonant frequency of the output filter circuit, the corresponding cycle time is calculated. Then, the voltage zero-crossing point is used as the time reference point, and half of the resonant cycle is used as the time offset. Finally, it is determined that the module's activation operation is performed half a resonant cycle after the voltage zero-crossing point, and the module's bypass operation is performed half a resonant cycle before the voltage zero-crossing point. This determines the activation time of each module to be activated and the bypass time of each module to be bypassed. This step is used to calculate the precise action time point for each module to be operated, ensuring that the module completes the switching at the appropriate phase angle of the voltage waveform, thereby minimizing disturbances to the output voltage waveform.

[0177] For example, in a DC boost grid-connected system, the control terminal obtains the current grid voltage phase as 30° in real time and detects that the positive zero-crossing of the voltage will occur in 2 milliseconds. Simultaneously, the control terminal reads from memory the pre-set values ​​of the output filter inductor (5mH) and the filter capacitor (10mH). The calculated resonant frequency is 712Hz, corresponding to a resonant period of 1 / 712Hz ≈ 0.001404 seconds. The control terminal uses the voltage zero-crossing point of 0° as the time reference point and takes half a resonant period of 0.702 milliseconds as the time offset. Finally, it is calculated that each module to be put into operation should be put into operation 0.702 milliseconds after the voltage zero-crossing point, that is, when the grid voltage phase is approximately 15°. Each module to be bypassed should be bypassed 0.702 milliseconds before the voltage zero-crossing point, that is, when the grid voltage phase is approximately -15° or 345°. The current voltage phase is 30°. Therefore, the modules to be put into operation will be put into operation when the phase reaches 15° in about 1.298 milliseconds, while the modules to be bypassed will have to wait for the next cycle.

[0178] S2035. Execute the input operation of each module to be input according to the input time, and execute the bypass operation of each module to be bypassed according to the bypass time, to obtain the adjusted H-bridge module group.

[0179] Specifically, based on the determined activation and bypass times of each module to be activated and each module to be bypassed, corresponding switching transistor trigger pulse signals are generated internally at the control terminal. These pulse signals are sent via optical fiber to the drive circuits of the insulated gate bipolar transistors in the corresponding H-bridge modules. When the activation time arrives, the control terminal sends a turn-off command to the bypass switch of the module to be activated and a turn-on command to its H-bridge switch, causing the DC-side capacitor of the module to be connected to the main circuit and begin contributing voltage. When the bypass time arrives, the control terminal sends a turn-off command to the H-bridge switch of the module to be bypassed and a turn-on command to its bypass switch, causing the module to be disconnected from the main circuit. After all the module switching operations are completed, an adjusted H-bridge module group matching the current voltage demand is obtained. This step is used to physically execute the module connection and disconnection operations through precise timing control, so that the series structure of the H-bridge module group can adapt to the grid voltage demand in real time, while ensuring the smoothness of the switching process.

[0180] For example, in a DC boost grid-connected system, the control terminal has determined that the activation time of two modules to be put into operation is when the grid voltage phase reaches 15°, that is, 0.702 milliseconds after the voltage zero crossing point. The bypass time of two modules to be bypassed is when the grid voltage phase reaches 345°, that is, 0.702 milliseconds before the voltage zero crossing point. The internal timer of the control terminal counts continuously with microsecond-level precision. When the timer count reaches the corresponding time, a switching transistor trigger pulse signal is immediately generated. When the activation time arrives, the control terminal sends a shutdown command to the bypass switches of the two modules to be activated (172V and 176V) via optical fiber, and simultaneously sends an activation command to their H-bridge switches, causing the DC-side capacitors of these two modules to be connected to the main circuit at the 15° phase point and begin contributing voltage. When the bypass time arrives, the control terminal sends a shutdown command to the H-bridge switches of the two modules to be bypassed, and simultaneously sends an activation command to their bypass switches, causing these two modules to be smoothly disconnected from the main circuit at the 345° phase point. After all the switching actions are completed, the total number of activated modules in the H-bridge module group changes from 50 to 52, and the peak output voltage increases from 9.25kV to 9.62kV, resulting in an adjusted H-bridge module group that matches the current voltage requirement.

[0181] Furthermore, after each switching operation, the harmonic components of the current output multi-level AC voltage can be analyzed in real time using Fast Fourier Transform to identify the characteristic harmonic order with the largest amplitude. Then, based on the actual number of modules in the current H-bridge module group, a fine-tuning angle is calculated and superimposed on the original carrier phase shift angle. By dynamically changing the carrier phase relationship of each module, the most prominent harmonic component is suppressed in a targeted manner, so that the harmonic distortion rate of the multi-level AC voltage output by the adjusted H-bridge module group is always stable below the preset harmonic threshold.

[0182] The technical effect of this solution in this embodiment is as follows: by obtaining the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group, the number of modules to be put into operation and bypassed is accurately calculated based on the difference between the voltage demand and the current peak output voltage. Based on the power grid phase and resonant frequency, the switching time is determined for each module to be switched, so that the operation of all modules avoids the resonant range of the filter circuit. While meeting the matching of the peak output voltage with the power grid demand, the voltage oscillation and current surge that may be caused by the instant of module switching are suppressed. This solves the problem of power quality degradation caused by unreasonable switching timing during the adjustment of the number of modules in the prior art, and improves the operational stability and grid connection reliability of the cascaded H-bridge converter during the dynamic adjustment process.

[0183] In one possible design, S2033, multiple modules to be deployed are determined from the H-bridge modules that have not been deployed in the H-bridge module group based on the number of deployed modules, and multiple modules to be bypassed are determined from the H-bridge modules that have been deployed in the H-bridge module group based on the number of bypass modules, including:

[0184] S20331. Obtain the first real-time voltage value of the DC side capacitor of the H-bridge module that has not been put into the H-bridge module group, and sort the H-bridge modules that have not been put into the H-bridge module group in ascending order according to the deviation between the first real-time voltage value and the preset reference value, and determine the H-bridge modules with the first number of modules put into the group in the ascending order as multiple modules to be put into the group.

[0185] Specifically, a voltage sampling circuit can be connected in parallel across the DC-side capacitor of each H-bridge module. The capacitor voltage signal is transmitted to the analog input module of the control terminal through an isolation amplifier to obtain the first real-time voltage value of the DC-side capacitor of all unused H-bridge modules. The digital signal processor of the control terminal compares these voltage values ​​one by one with the preset reference value stored internally to calculate the voltage deviation of each module. Then, all unused modules are sorted in ascending order of deviation. Finally, the number of modules equal to the number of modules to be put into operation is taken from the beginning of the sorting queue and these modules are identified as modules to be put into operation. This step is used to prioritize the modules with the lowest voltage from all the waiting modules to put them into operation, so as to balance the energy differences between modules and prevent individual modules from affecting the overall performance due to long-term idleness or over-discharge.

[0186] For example, in a DC boost grid-connected system, the control terminal needs to select three modules from the bypassed modules to put into operation. At this time, there are a total of six H-bridge modules that are not in operation. The control terminal collects the first real-time voltage values ​​of these six modules in real time through the voltage detection circuit connected in parallel across the DC side capacitor of each module. These values ​​are 191V, 182V, 188V, 176V, 195V, and 179V, respectively. The preset reference value stored in the control terminal is 185V. The digital signal processor calculates the deviation of each module's voltage value from the reference value: 191V deviation +6V, 182V deviation -3V, 188V deviation +3V, 176V deviation -9V, 195V deviation +10V, and 179V deviation -6V. Then, the six modules are sorted in ascending order according to the deviation amount from smallest to largest, that is, the voltage from lowest to highest. The sorting result is: 176V (deviation -9V), 179V (deviation -6V), 182V (deviation -3V), 188V (deviation +3V), 191V (deviation +6V), 195V (deviation +10V). The control terminal takes the first three modules from the beginning of the sorting queue, that is, the three modules with voltages of 176V, 179V and 182V, and determines them as the modules to be put into use.

[0187] The preset reference value is a voltage value used as a reference standard to measure the deviation of the current voltage of the DC-side capacitor of each H-bridge module. It is usually set as the rated operating value or target average value of the DC-side capacitor voltage of all H-bridge modules. This value can be determined according to the design parameters of the entire system. For example, the nominal voltage of the DC-side capacitor of the H-bridge module can be used as the preset reference value, or a dynamic average value can be calculated in real time based on the voltage of all currently engaged modules as the preset reference value.

[0188] S20332. Based on the deviation between the current voltage value and the preset reference value, the H-bridge modules that have been put into the H-bridge module group are arranged in descending order, and the H-bridge modules with the number of front bypass modules in the descending order are determined as multiple bypass modules.

[0189] Specifically, a voltage detection circuit can be connected in parallel across the DC-side capacitor of each H-bridge module that has been put into operation. The current voltage value acquired in real time is transmitted to the field-programmable gate array (FPGA) at the control end through an analog-to-digital converter. The FPGA compares the current voltage value of each module with the preset reference value stored in its internal register, calculates the voltage deviation of each module, and then sorts all the modules put into operation in descending order of deviation. Finally, the number of modules equal to the number of bypass modules is taken out from the beginning of the sorting queue and these modules are identified as the modules to be bypassed. This step is used to prioritize the removal of the module with the highest voltage from the currently working modules. By bypassing the modules with excess energy in a timely manner, the voltage balance between the modules is maintained and individual modules are prevented from being damaged due to excessive voltage.

[0190] For example, in a DC boost grid-connected system, the control terminal calculates based on voltage requirements that two already-operated H-bridge modules need to be bypassed. At this point, there are a total of eight H-bridge modules in operation. The control terminal uses a voltage sampling circuit connected in parallel across the DC-side capacitor of each module to collect the current voltage values ​​of these eight modules in real time: 192V, 188V, 196V, 179V, 201V, 185V, 193V, and 178V. The preset reference value stored internally in the control terminal is 185V. The digital signal processor calculates the deviation of each module's voltage value from the reference value: 192V deviation +7V, 188V deviation +3V, 196V deviation +11V, and 179V deviation -6V. The eight modules are then sorted in descending order of deviation (i.e., voltage from highest to lowest): 201V (deviation +16V), 196V (deviation +11V), 193V (deviation +8V), 192V (deviation +7V), 188V (deviation +3V), 185V (deviation 0V), 179V (deviation -6V), and 178V (deviation -7V). The control unit retrieves the first two modules from the beginning of the sorted queue, namely the modules with voltages of 201V and 196V, and identifies them as the modules to be bypassed.

[0191] The technical effect of this solution in this embodiment is as follows: by obtaining the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group, the number of modules to be put into operation and bypassed is accurately calculated based on the difference between the voltage demand and the current peak output voltage. Based on the power grid phase and resonant frequency, the switching time is determined for each module to be switched, so that the operation of all modules avoids the resonant range of the filter circuit. While meeting the matching of the peak output voltage with the power grid demand, the voltage oscillation and current surge that may be caused by the instant of module switching are suppressed. This solves the problem of power quality degradation caused by unreasonable switching timing during the adjustment of the number of modules in the prior art, and improves the operational stability and grid connection reliability of the cascaded H-bridge converter during the dynamic adjustment process.

[0192] In one possible design, S204 converts the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirements based on the adjusted H-bridge module group, including:

[0193] S2041. Based on the preset carrier phase-shifting PWM strategy, generate PWM drive signals for each H-bridge module in the H-bridge module group.

[0194] Specifically, a carrier generation unit, a phase adjustment unit, and a comparison unit can be set up inside the control terminal. The carrier generation unit is electrically connected to the phase adjustment unit, and the phase adjustment unit is in turn electrically connected to the comparison unit. The carrier generation unit generates multiple basic carrier signals, and the phase adjustment unit assigns a fixed phase offset to each basic carrier signal to form multiple carrier signals that satisfy the Pulse Width Modulation (PWM) strategy. The multiple carrier signals are input to the comparison unit and compared with the unified modulation wave signal input inside the comparison unit. The comparison unit directly outputs the corresponding number of PWM drive signals with mutually offset phases. Then, each PWM drive signal is transmitted to the switching transistor drive interface of the corresponding H-bridge module in the H-bridge module group through an independent signal transmission line. This completes the generation and transmission of PWM drive signals for each H-bridge module. This step is used to provide timing-coordinated drive signals for each H-bridge module, so that each H-bridge module can perform switching actions according to the set phase relationship.

[0195] Among them, the carrier phase-shifting PWM strategy is a waveform control method used in multi-module cascaded structures. In the H-bridge module group, this strategy allocates a set of carrier signals with the same frequency and amplitude but with fixed phase offset between each independent H-bridge module. All carrier signals share the same modulation wave signal. By cross-comparing the modulation wave with each carrier, a driving sequence that is staggered in time is formed, allowing different H-bridge modules to complete the conduction and turn-off actions in different phase intervals. Ultimately, the voltages output by each module are superimposed at the output terminal, forming a multi-level AC voltage with more steps and a smoother waveform. At the same time, it reduces the interference caused by voltage abrupt changes and improves the output waveform quality of the overall conversion structure.

[0196] The PWM drive signal is a square wave control signal with a fixed frequency and a variable duty cycle. In this application, it is generated by the control terminal according to the carrier phase-shift PWM strategy and transmitted to the switching interface of the H-bridge module. The signal directly controls the on and off states of the power switching devices inside the H-bridge module by alternating between high and low levels. When the level is high, the corresponding switching device is turned on, and when the level is low, the corresponding switching device is turned off. By adjusting the duration ratio of the high and low levels, the equivalent voltage value of the output voltage of the H-bridge module is changed, thereby converting the input DC voltage into an AC voltage that conforms to the target amplitude and frequency, providing basic control commands for subsequent voltage superposition and grid connection.

[0197] S2042. Input the adjusted DC voltage into each H-bridge module, and control the switching state of multiple switches in each H-bridge module according to the PWM drive signal, so that each H-bridge module converts the adjusted DC voltage into AC voltage, and obtains the AC voltage output by each H-bridge module.

[0198] Specifically, the adjusted DC voltage can be connected to the DC input interface of each H-bridge module in operation through the DC bus. The PWM drive signal is transmitted to the power switching device interface inside each H-bridge module through an independent drive line. By changing the high and low levels of the PWM drive signal, the conduction and cutoff of different power switching devices inside each H-bridge module are controlled sequentially, forming an alternating conduction state in the same H-bridge module. This transforms the DC input voltage into an AC voltage with alternating positive and negative polarities at the output interface of the H-bridge module, thus obtaining the AC voltage independently output by each H-bridge module. This step is used to convert the stable input DC voltage into an AC voltage that meets the phase and amplitude requirements, providing the basic output for subsequent voltage superposition to form a multi-level AC voltage.

[0199] S2043. The AC voltages output by each H-bridge module are superimposed to obtain a multi-level AC voltage.

[0200] Specifically, the AC output terminals of each H-bridge module in operation within the H-bridge module group can be electrically connected in series. The negative output terminal of the previous H-bridge module is directly connected to the positive output terminal of the next H-bridge module. The AC voltages output by each H-bridge module are superimposed in amplitude and phase within the series-connected circuit, forming a multi-level AC voltage with more steps and consistent amplitude and voltage requirements at the total output terminal of the series structure. This step is used to integrate the AC voltages output by a single H-bridge module into a smooth multi-level AC voltage that meets the grid access standards.

[0201] The technical effect of this scheme in this embodiment is as follows: Based on the carrier phase-shifting PWM strategy, phase-shifted drive signals are generated for each H-bridge module, and the switching state of each module is independently controlled to output AC voltage. The output voltages of each module are superimposed to form a multi-level stepped waveform. Through phase-shifted carrier allocation, the switching time of each H-bridge module is evenly distributed in the time domain, avoiding DC-side current spikes and severe bus voltage pulsations caused by synchronous switching of multiple modules. At the same time, the harmonic content of the output voltage is reduced through the multi-level superposition effect, making the grid-connected waveform closer to a sine wave. This solves the problem that existing cascaded inverters have excessive DC-side electrical stress and output power quality that is difficult to meet grid-connected standards when multiple modules work together due to concentrated switching time.

[0202] In one possible design, S2041 generates PWM drive signals for each H-bridge module in the H-bridge module group based on a preset carrier phase-shift PWM strategy, including:

[0203] S20411. Obtain the DC-side capacitor voltage of the target H-bridge module; wherein, the target H-bridge module is any one of the H-bridge modules in the H-bridge module group.

[0204] Specifically, a voltage sampling resistor network can be connected in parallel across the DC-side capacitor of each target H-bridge module in the H-bridge module group. The output of the voltage sampling resistor network is electrically connected to the voltage sampling interface inside the control terminal. The voltage sampling resistor network converts the voltage across the DC-side capacitor into a voltage signal adapted to the sampling interface. The voltage sampling interface directly receives the voltage signal and converts it into the corresponding electrical parameters, thereby obtaining the DC-side capacitor voltage of the target H-bridge module. This step is used to provide accurate voltage parameters for subsequent calculation of voltage deviation and generation of voltage equalization correction.

[0205] The DC-side capacitor voltage of the target H-bridge module refers to the DC voltage maintained across the DC-side capacitor connected in parallel at the DC input terminal of the H-bridge module. This voltage is provided by the DC voltage output from the photovoltaic array and adjusted to support the H-bridge module in completing the DC-to-AC conversion. It is the basic voltage for each H-bridge module to perform normal switching operations and output the corresponding AC level. Its magnitude directly determines the AC voltage amplitude that the H-bridge module can output. It is also a key electrical parameter for achieving voltage balance among multiple modules and ensuring stable output of the overall multi-level waveform.

[0206] S20412. Generate the voltage balance correction amount of the target H-bridge module based on the deviation between the DC-side capacitor voltage of the target H-bridge module and the preset voltage balance reference value.

[0207] Specifically, a numerical calculation unit can be set up inside the control terminal. The acquired DC-side capacitor voltage of the target H-bridge module and the voltage equalization reference value are synchronously input into the numerical calculation unit. The numerical calculation unit calculates the difference between the two electrical parameters to obtain the deviation value between the DC-side capacitor voltage and the voltage equalization reference value. Then, the deviation value is input to the adjustment calculation unit inside the control terminal. The adjustment calculation unit performs proportional calculation based on the magnitude and direction of the deviation value and outputs an electrical parameter adjustment value that matches the deviation. This forms the voltage equalization correction amount corresponding to the target H-bridge module. This step is used to provide a correction basis for the generation of the PWM drive signal of the target H-bridge module, so that the DC-side capacitor voltage of the target H-bridge module is consistent with the voltage equalization reference value.

[0208] Among them, the voltage equalization reference value is the ideal operating voltage value of the DC-side capacitor uniformly set for all H-bridge modules in the H-bridge module group. This voltage value is jointly determined by the adjusted DC voltage output by the photovoltaic array, the rated operating voltage of the H-bridge module, and the amplitude of the multi-level AC voltage required by the overall cascaded structure. It is used as a reference standard to judge whether the DC-side capacitor voltage of each target H-bridge module is balanced, so as to ensure that each H-bridge module maintains the same DC-side voltage level during operation.

[0209] The voltage equalization correction of the target H-bridge module is an adjustment parameter calculated based on the deviation between the DC-side capacitor voltage of the H-bridge module and the voltage equalization reference value. When the DC-side capacitor voltage is higher or lower than the voltage equalization reference value, the corresponding correction amount is calculated. This correction amount directly participates in the generation process of the PWM drive signal to fine-tune the drive signal parameters of the corresponding H-bridge module, change the conduction duration and working sequence of the internal switching devices of the H-bridge module, so that the DC-side capacitor voltage of the H-bridge module moves closer to the voltage equalization reference value.

[0210] S20413. Generate the PWM drive signal for the target H-bridge module according to the preset carrier phase-shift PWM strategy and voltage equalization correction amount.

[0211] Specifically, the original carrier signal and modulation wave signal of the target H-bridge module can be generated internally at the control terminal according to the carrier phase-shift PWM strategy. Then, the previously obtained voltage equalization correction is superimposed on the original modulation wave signal to finely adjust the amplitude or phase of the modulation wave signal. The modulation wave signal with voltage equalization correction and the original carrier signal are input together to the comparison unit inside the control terminal for level comparison. The comparison unit outputs the corrected PWM drive signal according to the comparison result. Then, the PWM drive signal is transmitted to the switching device interface of the target H-bridge module through a dedicated drive line to complete the generation of the PWM drive signal of the target H-bridge module. This step is used to correct the drive signal of the target H-bridge module while maintaining the normal output waveform of the carrier phase-shift PWM strategy, so that the DC side capacitor voltage of the target H-bridge module tends to be consistent.

[0212] The technical effect of this solution in this embodiment is as follows: The DC-side capacitor voltage of any target H-bridge module is obtained, its deviation from the voltage equalization reference value is calculated, and a corresponding voltage equalization correction is generated. This correction is integrated into the carrier phase-shift PWM strategy to generate a dedicated PWM drive signal for that module. By converting the voltage deviation into an independent duty cycle correction and injecting it into the drive signals of each module in a closed loop, modules whose DC-side capacitor voltage deviates from the reference value can actively converge to the reference value by adjusting their own energy throughput. This suppresses the voltage differentiation phenomenon between modules caused by differences in device parameters, uneven losses, or accumulated control delays in the cascaded topology. It solves the problem of overvoltage damage to some modules, output waveform distortion, and decreased system reliability caused by the continuous imbalance of DC-side capacitor voltages in each module during long-term operation of existing cascaded H-bridge inverters.

[0213] In one possible design, S204 integrates a multi-level AC voltage into a preset power grid, including:

[0214] S2044. Obtain the status of the preset power grid.

[0215] Specifically, a voltage sampling branch and a frequency sampling branch can be set at the grid connection interface. The input terminals of both the voltage sampling branch and the frequency sampling branch are electrically connected to the power grid line, and the output terminals are electrically connected to the signal acquisition interface inside the control terminal. The voltage sampling branch collects the real-time voltage amplitude in the power grid line and converts it into a level signal adapted to the signal acquisition interface. The frequency sampling branch collects the real-time period and phase changes in the power grid line and converts them into corresponding timing signals. The signal acquisition interface synchronously receives the above voltage and frequency signals. The control terminal analyzes the values ​​and timing of the two signals to distinguish whether there is a disturbance in the power grid, a voltage drop in the power grid, or the power grid is in normal operation. This completes the acquisition of the power grid status. This step is used to provide the corresponding power grid operation basis for subsequent multi-level AC voltage adjustment, power compensation of energy storage modules, and grid connection control.

[0216] The state of the power grid refers to the comprehensive electrical operating characteristics of the public power grid at the grid connection interface, including voltage amplitude, frequency, phase, and waveform stability. Specifically, it includes different manifestations such as normal and stable operation, voltage or frequency disturbances, and voltage drops. These characteristics can directly reflect whether the power grid is currently in a stable and reliable operating condition. They are the key basis for determining whether multi-level AC voltage can be directly connected to the power grid and whether phase and frequency regulation or voltage compensation is required. They also determine what grid connection control method the entire DC boost grid connection system needs to adopt to ensure a smooth connection process without affecting the operation of the power grid and its own equipment.

[0217] The grid connection interface refers to the point where the AC output of the entire DC boost grid-connected system is electrically connected to the public power grid. It is the key physical node where the multi-level AC voltage output by the system is formally connected to the grid. It is usually located after the series output of the H-bridge module group and before the grid connection switch and filter device. The voltage sampling branch, frequency sampling branch, and subsequent grid-connected control and protection devices are all arranged around this location to realize real-time perception of the grid status and smooth and safe grid connection operation.

[0218] S2045. When the preset power grid is in the state of disturbance, the frequency and phase of the multi-level AC voltage are adjusted to obtain a stable AC voltage that is synchronized with the disturbance in the preset power grid, and the stable AC voltage is then incorporated into the preset power grid.

[0219] Specifically, the phase acquisition unit and frequency adjustment unit inside the control terminal can be used to input the real-time frequency and phase signals of the power grid into the phase acquisition unit. The phase acquisition unit transmits the frequency and phase fluctuation parameters under power grid disturbances to the frequency adjustment unit. The frequency adjustment unit dynamically adjusts the original output multi-level AC voltage according to these parameters, synchronously changes the carrier period and phase offset of the PWM drive signal, and then adjusts the switching timing of each H-bridge module. This makes the frequency and phase of the multi-level AC voltage change synchronously with the power grid disturbances in real time, forming a stable AC voltage that is consistent with the power grid fluctuations. Then, the stable AC voltage is smoothly connected to the power grid through the grid connection interface. This step is used to ensure that the output voltage matches and aligns with the power grid in real time when there are fluctuations in the power grid, avoiding grid connection impact caused by frequency and phase mismatch, and ensuring the continuous and stable grid-connected operation of the system.

[0220] S2046. When the preset grid state is that the grid voltage drops, power is released through the preset energy storage module to compensate for the voltage deviation caused by the grid voltage drop, so as to obtain an AC voltage that meets the preset grid-connected continuous operation requirements, and the AC voltage that meets the preset grid-connected continuous operation requirements is connected to the preset grid; wherein, the grid voltage drops refer to the voltage of the preset grid being lower than the preset voltage rating after a preset time period.

[0221] Specifically, when the grid voltage drops, the control terminal outputs a power release command to a preset energy storage module. The DC output terminal of the energy storage module is electrically connected to the DC bus of the H-bridge module group. After receiving the command, the energy storage module converts the stored electrical energy into corresponding power and releases it to the DC bus to supplement the insufficient output power of the photovoltaic array and increase the input voltage of the DC bus. The control terminal then adjusts the duty cycle and output amplitude of the carrier phase-shift PWM drive signal according to the deviation value of the voltage drop, so that the multi-level AC voltage output by the H-bridge module group is raised to the rated amplitude required for grid connection, making up for the deviation caused by the grid voltage drop, forming an AC voltage that meets the requirements for continuous grid connection operation, and then stably connecting the AC voltage to the grid through the grid connection line. This step is used to quickly supplement power and voltage by the energy storage module when the grid voltage drops, maintain the uninterrupted output voltage of the system, realize low voltage ride-through and maintain grid connection without disconnection.

[0222] Among them, a voltage drop in the power grid refers to a situation where the actual voltage amplitude of the public power grid is continuously lower than the preset voltage rating within a preset time period. This manifests as an abnormal operating state in which the power grid voltage drops sharply in a short period of time. This state will affect the normal output and stable operation of the grid-connected system and is a typical form of power grid fault that requires active compensation and response during grid-connected operation.

[0223] Energy storage modules are energy storage units used to pre-store electrical energy and quickly release power when needed. They can be installed on the DC bus side of the H-bridge module group. Their DC input terminal is electrically connected to the DC bus, and their DC output terminal is also electrically connected to the DC bus. They can absorb and store electrical energy when the grid voltage is normal, and release power to the DC bus when the grid voltage drops, providing voltage and power compensation for the system and supporting the continuous and stable operation of the grid-connected system.

[0224] The technical effects of this solution in this embodiment are: real-time acquisition of grid status; active adjustment of the frequency and phase of multi-level AC voltage to achieve synchronous and stable grid connection when disturbances occur; release of power through preset energy storage modules to compensate for voltage deviation and maintain continuous grid connection operation when voltage drops occur; and construction of a dual-mode grid connection support architecture of frequency and phase synchronization adjustment and active power dynamic compensation, enabling the system to have inertial response capability under grid disturbance conditions and low voltage ride-through capability under grid voltage drop conditions. This solves the problem that DC boost grid connection solutions lack active support means and are prone to triggering passive grid disconnection protection when facing grid frequency fluctuations, phase shifts and voltage drops.

[0225] In one possible design, S2046 uses a pre-set energy storage module to release power to compensate for voltage deviations caused by grid voltage drops, thereby obtaining an AC voltage that meets the preset requirements for continuous grid-connected operation, including:

[0226] S20461. Obtain the magnitude and duration of the voltage drop when the grid voltage drops.

[0227] Specifically, a voltage sampling circuit electrically connected to the power grid line can be installed at the grid connection point. The output of the voltage sampling circuit is connected to the signal processing unit inside the control unit. The signal processing unit contains an amplitude calculation module and a timing module. The voltage sampling circuit collects the instantaneous voltage value of the power grid in real time and transmits it to the amplitude calculation module. The amplitude calculation module compares the real-time voltage with the preset voltage rating and calculates the difference ratio between the real-time voltage and the rated value, thereby obtaining the voltage drop amplitude of the power grid. When the amplitude calculation module detects that the voltage is lower than the rated value and the drop condition is met, the timing module starts synchronously and accumulates the duration of the voltage drop until the voltage recovers to the rated value range. The accumulated duration is the drop duration. This step is used to provide accurate drop parameters for subsequent power distribution strategies, ensuring that the capacitor and lithium battery can output compensation power reasonably according to the actual drop situation.

[0228] Among them, the voltage drop amplitude refers to the ratio of the difference between the real-time voltage amplitude of the power grid and the preset rated voltage value to the rated voltage when a voltage drop occurs. It is used to intuitively reflect the severity of the voltage drop. The larger the value, the deeper the voltage drop and the more obvious the impact on the operation of the grid-connected system. It is the core basis for determining how much compensation power the energy storage module needs to output. The voltage drop duration refers to the total time that the grid voltage starts to fall below the preset rated voltage value and returns to the rated value range. It is used to indicate how long the voltage drop phenomenon lasts. This duration determines how the capacitor and lithium battery in the energy storage module need to cooperate in discharging to achieve a reasonable distribution between instantaneous compensation and continuous support.

[0229] S20462. Generate a power allocation strategy for a preset energy storage system based on the drop amplitude and drop duration; wherein the energy storage system includes a capacitor and a lithium battery, the capacitor is used to provide instantaneous power compensation, and the lithium battery is used to provide continuous power compensation.

[0230] Specifically, a strategy calculation unit can be set up inside the control terminal. The acquired drop amplitude and drop duration are synchronously input into the strategy calculation unit. The strategy calculation unit determines the required instantaneous compensation power intensity based on the drop amplitude value and the required continuous compensation power duration based on the drop duration value. When a large drop amplitude is detected, the capacitor is preferentially allocated to provide instantaneous high-power compensation. When a long drop duration is detected, the output power of the lithium battery is increased to provide stable continuous compensation. Combining the characteristics of the two energy storage devices, a power allocation strategy for the capacitor and lithium battery to work together is formed. This step is used to provide a clear discharge coordination scheme for the capacitor and lithium battery in the energy storage system, allowing the two energy storage devices to compensate for the power and voltage gap caused by grid voltage drops according to their respective advantages.

[0231] The power allocation strategy is a coordinated discharge scheme for capacitors and lithium batteries in the energy storage system, formulated based on the magnitude and duration of voltage drops in the grid. It defines the output power, start-up and stop times, and duration of continuous discharge for each device, allowing them to work in harmony according to their characteristics. This achieves both rapid compensation and sustained support during voltage drops, ultimately resulting in a stable and reliable power compensation output. Capacitors are energy storage components capable of rapid charging and discharging with extremely fast response times. They are primarily used to provide instantaneous high-power compensation at the initial moment of a large voltage drop, quickly filling the voltage gap. Lithium batteries are electrochemical energy storage devices with high energy density and long discharge times. They are mainly used to provide continuous and stable power output during prolonged voltage drops, maintaining uninterrupted system voltage and power for extended periods. Together, they achieve the dual effects of instantaneous compensation and sustained support.

[0232] S20463. Control the capacitor and lithium battery to discharge according to the power distribution strategy to compensate for the voltage deviation caused by the grid voltage drop, so as to obtain an AC voltage that meets the preset grid-connected continuous operation requirements.

[0233] Specifically, based on the generated power allocation strategy, the control terminal outputs corresponding discharge control commands, which are transmitted to the discharge control circuits corresponding to the capacitors and the discharge management circuits corresponding to the lithium batteries in the energy storage system. Under the command drive, the capacitors quickly release instantaneous high power to directly supplement the instantaneous voltage gap of the DC bus. The lithium batteries synchronously discharge steadily according to the power and duration set by the strategy, maintaining the DC bus voltage at a level not lower than the grid-connected level during voltage drops. The control terminal then adjusts the amplitude and duty cycle of the carrier phase-shift PWM drive signal according to the real-time compensated DC bus voltage, so that the multi-level AC voltage output by the H-bridge module group always remains within the range required for continuous grid-connected operation, thereby compensating for the deviation caused by the grid voltage drop. This step is used to allow the capacitors and lithium batteries to discharge in coordination according to their respective characteristics, accurately compensate for the power deficiency caused by the voltage drop, and ensure that the grid-connected system can still output qualified AC voltage and continue to operate in grid-connected mode when the grid is abnormal.

[0234] The technical effect of this solution in this embodiment is as follows: it acquires the magnitude and duration of grid voltage drops in real time, generates a dynamic power allocation strategy accordingly, and controls the capacitor and lithium battery to discharge at different ratios to compensate for voltage deviations. By constructing a closed-loop control architecture of drop feature perception, allocation strategy generation, and heterogeneous energy storage collaborative response, the capacitor can leverage its instantaneous high power density advantage to respond to short-term deep drops, while the lithium battery can leverage its high energy density advantage to support long-term mild drops. The two energy storage components complement each other on both the time and power scales, solving the problem that existing photovoltaic grid-connected systems suffer from insufficient instantaneous response capability or inability to simultaneously maintain continuous power supply capability in grid voltage drop scenarios due to single energy storage configuration and fixed power allocation.

[0235] Figure 3 A flowchart illustrating the DC boost grid-connected method provided in the embodiments of this application. Figure 2 In this embodiment, in Figure 2 Based on the provided embodiments, the DC-DC boost grid-connected method is further explained. The DC-DC boost grid-connected method includes:

[0236] S301. Obtain the DC-side capacitor voltage of the target H-bridge module; wherein, the target H-bridge module is any one of the H-bridge modules in the H-bridge module group.

[0237] S302. Generate the voltage equalization correction amount of the target H-bridge module based on the deviation between the DC-side capacitor voltage of the target H-bridge module and the preset voltage equalization reference value.

[0238] S303. Generate the PWM drive signal for the target H-bridge module according to the preset carrier phase-shift PWM strategy and voltage equalization correction amount.

[0239] S301-S303 are similar to S20411-S20413, and will not be described again in this embodiment.

[0240] S304. Input the PWM drive signal to the target H-bridge module to adjust the duty cycle of the switches in the target H-bridge module, so that the DC-side capacitor voltage of the target H-bridge module converges to the preset voltage equalization reference value.

[0241] Specifically, the voltage-balanced PWM drive signal can be directly transmitted to the power switching device drive interface of the target H-bridge module through a dedicated drive line. By utilizing the duration changes of the high and low levels of this drive signal, the conduction duration of the power switching device inside the target H-bridge module within a switching cycle is altered, thereby adjusting the duty cycle of the corresponding switch. The change in duty cycle changes the energy charging and discharging state of the target H-bridge module during operation, thereby changing the charging and discharging speed of the DC-side capacitor of the target H-bridge module. This allows the DC-side capacitor voltage to gradually approach the voltage balancing reference value and remain stable. This step is used to finely adjust the switch duty cycle through the corrected PWM drive signal, ensuring that the DC-side capacitor voltage of the target H-bridge module is consistent with the voltage balancing reference value, thus achieving voltage balancing among the H-bridge module groups.

[0242] S305. If the DC-side capacitor voltage of the target H-bridge module exceeds the preset fault threshold under the action of the PWM drive signal and the duration exceeds the preset time threshold, the target H-bridge module is determined to be a permanent fault, and the target H-bridge module is bypassed and replaced with a preset spare H-bridge module.

[0243] Specifically, a voltage judgment unit and a timer unit can be set up inside the control terminal. The voltage judgment unit and the timer unit are electrically connected to each other. The DC-side capacitor voltage of the target H-bridge module is input to the voltage judgment unit in real time and compared with the fault threshold. When the voltage judgment unit determines that the DC-side capacitor voltage is greater than the fault threshold, the timer unit starts to accumulate the duration synchronously. When the accumulated duration is greater than the time threshold, the control terminal outputs a bypass control signal to the bypass switch device connected in series across the two ends of the target H-bridge module, driving the bypass switch to conduct to disconnect the target H-bridge module from the circuit and realize electrical bypass. At the same time, the control terminal outputs a switching signal to the access switch device corresponding to the preset backup H-bridge module, driving the access switch to conduct to connect the backup H-bridge module to the series circuit where the original target H-bridge module is located, completing the replacement operation. This step is used to remove the faulty module and put the backup module into the backup module in time when the target H-bridge module is abnormal and cannot be restored by voltage equalization correction, so as to ensure that the overall output status of the H-bridge module group is not interrupted.

[0244] The technical effect of this solution in this embodiment is as follows: a PWM drive signal carrying voltage equalization correction is input to the target H-bridge module to drive its duty cycle adjustment and cause the capacitor voltage to converge to the reference value. Under the premise that this closed-loop control is effective, only when the DC side capacitor voltage of the module is still greater than the fault threshold and exceeds the preset time threshold is it determined to be a permanent fault and bypass and redundancy replacement is performed. By setting the execution order of regulation first and fault judgment later and the judgment threshold of timeout duration, false bypass and frequent switching of redundant modules caused by instantaneous disturbances, sampling noise or control transient processes are avoided. At the same time, it is ensured that faulty modules that have lost voltage regulation capability can be accurately identified and reliably isolated from the running queue. This solves the problem that existing cascaded inverters cannot distinguish between recoverable voltage transient offset and unrecoverable permanent module faults when voltage equalization control fails, resulting in frequent false bypass, waste of redundant resources and insufficient system fault tolerance.

[0245] This application also provides a DC boost grid-connected system, including:

[0246] Photovoltaic arrays are used to output DC voltage.

[0247] Specifically, multiple photovoltaic cells can be connected in series and parallel to form a photovoltaic module. Several photovoltaic modules can then be connected in series and parallel to form a complete photovoltaic array. Under the action of sunlight, the photovoltaic cells generate the photovoltaic effect, which directly converts solar energy into DC power and outputs a stable DC voltage through output cables. This setup is used to provide the original DC power input for the entire DC boost grid-connected system, serving as the energy source for subsequent voltage regulation, power conversion, and grid-connected output.

[0248] The control terminal is used to acquire the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the preset voltage requirements of the power grid. It adjusts the DC voltage according to the light intensity to match the DC voltage with the light intensity, thus obtaining the adjusted DC voltage.

[0249] Specifically, a DC voltage sampling circuit can be set at the output end of the photovoltaic array, and a light intensity sensor can be placed in the environment where the photovoltaic array is located. The output ends of both the voltage sampling circuit and the light intensity sensor are connected to the analog signal acquisition interface of the control terminal. At the same time, the control terminal reads the preset grid voltage requirement parameters. The control terminal compares the collected DC voltage with the light intensity through its internal computing unit, and adjusts the output amplitude of the DC voltage according to the intensity of the light, so that the magnitude of the DC voltage is adapted to the current light conditions, resulting in a stable and matched adjusted DC voltage. This setting is used to ensure that the photovoltaic array operates at a suitable voltage point under different light conditions, improves the utilization rate of light energy, and provides a stable DC input for the subsequent H-bridge module group to perform power conversion.

[0250] The H-bridge module group is used to adjust the number of H-bridge modules and the switching time according to the voltage requirements to obtain the adjusted H-bridge module group. The adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirements, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below the preset threshold during the adjustment process.

[0251] Specifically, an H-bridge module group can be composed of multiple H-bridge modules with identical structures connected in series. The DC side of each H-bridge module is connected to the DC bus after the photovoltaic array is combined. Each H-bridge module integrates a bypass switch and a voltage detection circuit. After receiving the command from the control terminal to switch on and off modules, the H-bridge module group prioritizes switching on the module with the lowest voltage and bypassing the module with the highest voltage based on the real-time voltage value of the DC side capacitor of each module. At the same time, combined with the grid voltage phase and the resonant frequency of the output filter circuit, it precisely controls the switching action of each module to be executed near the voltage zero crossing point. In the process of dynamically adjusting the number of series modules to match the grid voltage demand, it maintains a smooth transition of the output voltage waveform, so that the harmonic distortion rate and amplitude fluctuation rate are both lower than the preset threshold. This setting is used to ensure the stability of grid-connected power quality while changing the number of output levels to match different voltage demands through automatic selection and precise timing control of modules.

[0252] The control unit is also used to convert the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement based on the adjusted H-bridge module group, and to connect the multi-level AC voltage into the preset grid, so as to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset grid.

[0253] Specifically, the control terminal can generate carrier phase-shifted PWM drive signals with corresponding number of groups and staggered phases based on the adjusted number of H-bridge module groups. These drive signals are then input to each H-bridge module that is already in operation, controlling the internal switching devices of each H-bridge module to turn on and off according to a set timing sequence. This process sequentially superimposes and converts the adjusted DC voltage into a multi-level AC voltage with more level levels and amplitude consistent with the grid voltage requirements. The multi-level AC voltage is then smoothly connected to the public grid through the grid connection interface. This setup is used to complete the efficient boost and conversion of photovoltaic DC to AC, achieving stable transmission of solar energy to electrical energy, while ensuring that the output voltage accurately matches the grid requirements, thus completing the entire process of photovoltaic DC boost and grid connection.

[0254] The technical effect of this solution in this embodiment is as follows: By adopting a cascaded topology of H-bridge modules, the DC voltage output of the photovoltaic array is dynamically adjusted at the control end according to the light intensity to match the light conditions. At the same time, the number of H-bridge modules and the switching time are dynamically adjusted according to the grid voltage demand, so that the peak value of the multi-level AC voltage output by the adjusted H-bridge module group matches the voltage demand. In the entire adjustment process, the harmonic distortion rate and amplitude fluctuation rate of the output voltage are actively constrained to be lower than the preset threshold. Without the need to configure a power frequency step-up transformer and a large-capacity inverter, direct step-up grid connection from photovoltaic DC to high-voltage AC is achieved. From the hardware architecture level, the burden of volume, cost and structural complexity brought by transformers and large inverters is eliminated. At the same time, the voltage distortion and amplitude fluctuation problems that are prone to occur during the dynamic adjustment of the number of modules are solved, improving the grid-connected power quality and system operation stability, and reducing the cost of photovoltaic DC step-up grid connection system.

[0255] The DC boost grid connection method provided in this application is applicable to rural distributed photovoltaic (PV) scenarios. It achieves direct boosting of the PV DC bus to 10kV AC grid connection via H-bridge cascaded modules, eliminating the need for a 10kV / 400V power frequency transformer and reducing system costs and losses. Traditional rural PV systems require a DC / AC inverter (400V) + a boost transformer (10kV), resulting in high equipment costs, efficiency losses of approximately 5-8%, and significant line losses due to the high impedance of rural power grids. Furthermore, transformer maintenance is complex and unsuitable for remote areas. Conventional DC / DC boosting to 10kV DC followed by inversion requires a high-voltage, high-capacity DC / DC converter, leading to high costs. Modular multilevel converters (MMCs) are complex and difficult to control.

[0256] This application also provides a DC boost grid-connected system suitable for rural distributed photovoltaic systems, the core components of which include:

[0257] Photovoltaic DC bus: After the rural distributed photovoltaic arrays are synchronized by Maximum Power Point Tracking (MPPT), the current is uniformly collected to the DC bus (voltage range: 600-1500V).

[0258] H-bridge cascaded inverter: Consists of N cascaded H-bridge power modules (single module input DC voltage 600-1500V, output AC single-phase superposition). The number of modules N is dynamically configured according to the 10kV voltage requirement (e.g., N=12, single module output peak 850V, cascaded to 10kV line voltage).

[0259] DC circuit breaker and protection module: Enables rapid isolation of DC side faults.

[0260] A control method for H-bridge cascading in a DC boost grid-connected system suitable for rural distributed photovoltaic power generation is as follows:

[0261] 1. Voltage Equalization Control: Carrier Phase-Shifted Pulse Width Modulation (CPS-PWM) is used to ensure balanced DC-side voltage across all H-bridge modules. The number of modules in operation is dynamically adjusted (e.g., reducing the number of modules on cloudy days to lower switching losses).

[0262] 2. Transformerless grid connection synchronization: Based on the Virtual Synchronous Generator (VSG) algorithm, inertia is simulated to enhance grid stability.

[0263] 3. Adaptive DC bus voltage: The DC bus voltage is dynamically adjusted according to the light intensity (e.g., it is boosted to 1500V under strong light to reduce line loss).

[0264] This control method eliminates the need for a power frequency transformer: H-bridge cascade directly outputs 10kV AC, improving efficiency by ≥3%, and the modular design supports the phased expansion of rural photovoltaic systems. A single module failure does not affect the overall operation. At the same time, it features Low Voltage Ride Through (LVRT): short-term compensation for power deficit is achieved through DC energy storage modules (supercapacitors).

[0265] Figure 4 This is a schematic diagram of the system topology for traditional AC access methods of rural distributed photovoltaic systems provided in the embodiments of this application. Figure 4 This showcases the grid connection architecture of a traditional rural distributed photovoltaic power station. Figure 4 The system uses four 400kW distribution transformers as core grid-connected nodes, with two photovoltaic inverter units connected to each node. Each unit consists of photovoltaic modules, a DC / DC boost stage, and an AC / DC inverter stage. The eight units together form a total installed capacity of 1.5MW. The DC power output from the photovoltaic modules is boosted by the DC / DC converter, then inverted into low-voltage AC power by the AC / DC converter, and finally boosted by the distribution transformer before being connected to the grid. The diagram shows that the cost of the photovoltaic inverter is approximately 0.2 yuan / W. It clearly presents the multi-stage energy conversion path of the traditional scheme: photovoltaic modules → DC / DC boost → AC / DC inverter → distribution transformer boost and grid connection. This demonstrates the technical characteristics of this scheme in terms of equipment level, cost structure, and grid connection process.

[0266] Figure 5The three-phase cascaded H-bridge photovoltaic DC boost grid-connected system architecture diagram provided in this application embodiment illustrates the complete energy conversion and grid connection path from photovoltaic array to DC bus to cascaded H-bridges to the 10kV power grid. The diagram shows a symmetrical design for phases A, B, and C, with each phase consisting of six independent sub-units connected in series. Each sub-unit sequentially includes a photovoltaic array, a DC / DC link, and an H-bridge module. The DC output from the photovoltaic array, after being regulated by the DC / DC link, serves as the DC input to the corresponding H-bridge module. The H-bridge modules within each phase, through cascading and superposition, directly convert the DC voltage into a multi-level AC voltage that meets the 10kV requirement. This voltage is then fed into the 10kV power grid after three-phase convergence. This demonstrates the core technical features of this scheme: no power frequency transformer, modular cascading, and direct boost grid connection. It also showcases the advantages of the three-phase structure in outputting symmetrical AC voltage and improving grid connection stability.

[0267] Figure 6 The circuit diagram of the H-bridge cascade module provided in this application embodiment illustrates the internal topology of a single H-bridge power unit in a cascaded H-bridge grid-connected system. The left side of the diagram represents the DC input section, consisting of two sets of series capacitors and parallel resistors, used to support the DC bus voltage and achieve voltage equalization. The right side represents the full-bridge inverter main circuit, composed of four power switching devices (such as IGBTs or MOSFETs) with anti-parallel diodes forming a standard H-bridge structure. By controlling the on and off timing of the four switching devices, the DC input on the left can be converted into an AC square wave or stepped wave output with controllable amplitude. This module serves as the basic unit of the cascaded system; multiple identical modules connected in series can be superimposed to output a higher level of AC voltage, making it the core power conversion unit for achieving transformerless direct voltage boosting and grid connection.

[0268] Figure 7 This diagram illustrates the cascading of H-bridge modules provided in this application, demonstrating how multiple independent H-bridge power units can be superimposed in series to output a higher level of AC voltage. The diagram clearly shows three identical H-bridge modules. Each module consists of four power switching devices with anti-parallel diodes, such as Insulated Gate Bipolar Transistors (IGBTs), and a DC support capacitor, forming a standard full-bridge structure. The AC output terminals of each module are connected in series, forming a complete cascaded link from terminal a to terminal n. The DC side remains independently powered. By independently controlling the switching devices of each H-bridge module, different phases or amplitudes of AC voltage can be output from each module. These voltages are then superimposed to form a multi-level, high-amplitude composite AC output. This intuitively demonstrates the core principle of series connection and voltage superposition of cascaded H-bridge topology modules, a key method for achieving direct step-up to medium-voltage grid connection without a power frequency transformer.

[0269] Figure 8The three-level H-bridge cascade module and its cascade diagram provided for embodiments of this application are used to illustrate the circuit structure of an H-bridge power unit using a three-level topology and its series cascade. The diagram includes two identical three-level H-bridge units (unit 1 and unit 2), each unit containing eight power switching transistors with anti-parallel diodes (e.g., ...). – ), 4 clamping diodes (such as – ) and two DC support capacitors connected in series (such as , Composed of three levels, the three-level topology can output three different AC voltage waveforms through the cooperation of clamping diodes and switching transistors. Compared with the traditional two-level H-bridge, it can effectively reduce output harmonics and switching losses. The AC output terminals (A1, A2) of the two units can be further cascaded in series. By superimposing their respective three-level outputs, a higher-level and more-level composite AC voltage is formed. This intuitively demonstrates the advantages of the three-level topology in improving output quality and reducing device stress, as well as the core role of the cascaded structure in realizing direct grid connection of medium voltage.

[0270] Figure 9 This is a circuit diagram of a T-type three-level H-bridge cascaded module provided in an embodiment of this application, used to illustrate the internal structure of an H-bridge power unit employing a T-type three-level topology. The left side of the diagram represents the DC-side input section, consisting of two series-connected DC support capacitors. , The first section is designed to support the DC bus voltage and provide the midpoint potential. The second section is a T-type three-level H-bridge main circuit, which includes four main power switching transistors with anti-parallel diodes and four bidirectional clamping switching transistors located at the midpoint of the bridge arms. By controlling the on and off sequence of these switching transistors, three different voltage levels—positive, zero, and negative—can be output on the AC side. Compared with the traditional two-level H-bridge, it can effectively reduce output harmonics, reduce switching losses, and improve power quality. As the basic unit of a cascaded system, multiple identical modules can be connected in series to superimpose higher-level AC voltages. This is an efficient topology scheme for achieving transformerless direct voltage boosting and grid connection. The diagram clearly shows the electrical connection relationships of key components such as DC support, T-type clamping, and full-bridge inverter.

[0271] Figure 10The control logic block diagram of the H-bridge cascaded grid-connected system provided in this application embodiment illustrates the overall control architecture based on the Virtual Synchronous Generator (VSG) synchronization and voltage equalization algorithm. The control logic in the diagram is divided into two main modules: the left side is the Virtual Synchronous Generator (VSG) control, which includes four sub-stages: virtual inertia simulation, damping control, frequency regulation, and phase synchronization. This simulates the inertia and damping characteristics of a synchronous generator, achieving friendly synchronization with the power grid and improving system stability. The right side is the voltage equalization control, which includes sub-stages such as module dynamic configuration, voltage balancing, carrier stacking, and carrier phase shifting. This ensures DC-side voltage balance among each H-bridge module and optimizes the multi-level output waveform quality through carrier strategies. The waveform diagram below visually presents the control effects of carrier stacking and carrier phase shifting, demonstrating the role of the control algorithm in output waveform optimization and module voltage equalization. Overall, the diagram clearly demonstrates the core control concept of this system: VSG grid-connected synchronization + module voltage equalization control.

[0272] The H-bridge module can use SiC MOSFET devices with a withstand voltage of 1700V and a switching frequency of 20kHz, which can effectively reduce switching losses and conduction losses and improve system conversion efficiency. At the same time, a bidirectional DC / DC interface can be configured on the DC bus to reserve expansion space for the subsequent access of energy storage modules (such as lithium batteries and supercapacitors), which facilitates the realization of photovoltaic-storage synergy and peak shaving and valley filling. It can also realize energy management through real-time dispatching algorithms, prioritizing the consumption of local photovoltaic output to meet local load demand. When the power generation exceeds the local load, the surplus power is smoothly integrated into the grid, which not only improves the utilization rate of clean energy, but also enhances the system's friendly support capability to the grid.

[0273] Figure 11 This is a schematic diagram of the structure of the DC boost grid-connected device provided in an embodiment of this application. Figure 11 As shown, the DC boost grid-connected device includes:

[0274] The first acquisition module 1101 is used to acquire the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirements of the preset power grid.

[0275] The first adjustment module 1102 is used to adjust the DC voltage according to the light intensity so that the DC voltage matches the light intensity, thereby obtaining the adjusted DC voltage.

[0276] The second adjustment module 1103 is used to adjust the number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group according to the voltage requirements, so as to obtain the adjusted H-bridge module group. The adjustment is used to make the peak value of the multi-level AC voltage output by the adjusted H-bridge module group match the voltage requirements, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below the preset threshold during the adjustment process.

[0277] The conversion module 1104 is used to convert the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement according to the adjusted H-bridge module group, and to connect the multi-level AC voltage into the preset grid, so as to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset grid.

[0278] In one possible design, the photovoltaic array includes multiple photovoltaic strings, and the first adjustment module 1102 includes:

[0279] The first acquisition unit is used to acquire the ambient temperature of the environment where the photovoltaic array is located, the output voltage and output power of each photovoltaic string, and the current voltage value of the DC side capacitor of each H-bridge module in the H-bridge module group.

[0280] The first determining unit is used to determine the target voltage value of each photovoltaic string when it reaches the preset maximum output power under the light intensity condition, based on the output power and light intensity.

[0281] The correction unit is used to perform temperature compensation correction on the target voltage value based on the ambient temperature, so as to obtain the corrected target voltage value for each photovoltaic string.

[0282] The first generation unit is used to generate voltage adjustment commands for each photovoltaic string based on the deviation between the output voltage of each photovoltaic string and the corrected target voltage value of each photovoltaic string; wherein, the voltage adjustment commands are used to adjust the preset duty cycle of the voltage adjustment unit in each photovoltaic string so that the output voltage of each photovoltaic string converges to the corrected target voltage value of each photovoltaic string.

[0283] The first adjustment unit is used to adjust the preset duty cycle according to the voltage adjustment command to obtain the adjusted output voltage of each photovoltaic string, and to combine the adjusted output voltage of each photovoltaic string to obtain the adjusted DC voltage.

[0284] In one possible design, the second adjustment module includes:

[0285] The second acquisition unit is used to acquire the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group.

[0286] The first calculation unit is used to calculate the number of modules to be put into operation and the number of modules to be bypassed based on voltage demand and peak value. The number of modules to be put into operation refers to the number of H-bridge modules in the H-bridge module group that need to be put into operation, and the number of modules to be bypassed refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed.

[0287] The second determining unit is used to determine multiple modules to be put into operation from the H-bridge modules that have not been put into operation based on the number of modules put into operation, and to determine multiple modules to be bypassed from the H-bridge modules that have been put into operation based on the number of bypass modules.

[0288] The third determining unit is used to determine the activation time of each module to be activated and the bypass time of each module to be bypassed based on the voltage phase and resonant frequency.

[0289] The execution unit is used to perform the input operation of each module to be input according to the input time, and to perform the bypass operation of each module to be bypassed according to the bypass time, so as to obtain the adjusted H-bridge module group.

[0290] In one possible design, the second defining unit includes:

[0291] The ascending order arrangement component is used to obtain the first real-time voltage value of the DC side capacitor of the H-bridge module that has not been put into the H-bridge module group, and to arrange the H-bridge modules that have not been put into the H-bridge module group in ascending order according to the deviation between the first real-time voltage value and the preset reference value, and to determine the H-bridge modules that have been put into the group in the ascending order as multiple modules to be put into the group.

[0292] The descending order arrangement component is used to arrange the H-bridge modules that have been put into the H-bridge module group in descending order according to the deviation between the current voltage value and the preset reference value, and to determine the H-bridge modules with the number of front bypass modules in the descending order as multiple bypass modules.

[0293] In one possible design, the conversion module 1104 includes:

[0294] The second generation unit is used to generate PWM drive signals for each H-bridge module in the H-bridge module group based on a preset carrier phase-shift PWM strategy.

[0295] The input unit is used to input the adjusted DC voltage into each H-bridge module and control the switching state of multiple switches in each H-bridge module according to the PWM drive signal, so that each H-bridge module converts the adjusted DC voltage into AC voltage, and obtains the AC voltage output by each H-bridge module.

[0296] The superposition unit is used to superimpose the AC voltages output by each H-bridge module to obtain a multi-level AC voltage.

[0297] In one possible design, the second generating unit includes:

[0298] The first acquisition component is used to acquire the DC-side capacitor voltage of the target H-bridge module; wherein the target H-bridge module is any one of the H-bridge modules in the H-bridge module group.

[0299] The first generation component is used to generate a voltage equalization correction amount for the target H-bridge module based on the deviation between the DC-side capacitor voltage of the target H-bridge module and a preset voltage equalization reference value.

[0300] The second generation component is used to generate the PWM drive signal for the target H-bridge module according to the preset carrier phase-shift PWM strategy and voltage equalization correction amount.

[0301] In one possible design, the second generating unit further includes:

[0302] The input component is used to input the PWM drive signal to the target H-bridge module to adjust the duty cycle of the switches in the target H-bridge module, so that the DC-side capacitor voltage of the target H-bridge module converges to the preset voltage equalization reference value.

[0303] The determination component is used to determine that if the DC-side capacitor voltage of the target H-bridge module is greater than a preset fault threshold and the duration is greater than a preset time threshold under the action of the PWM drive signal, the target H-bridge module is determined to be permanently faulty, the target H-bridge module is bypassed, and a preset spare H-bridge module is used to replace the target H-bridge module.

[0304] In one possible design, the conversion module 1104 includes:

[0305] The third acquisition unit is used to acquire the state of the preset power grid.

[0306] The second regulating unit is used to regulate the frequency and phase of the multi-level AC voltage when the preset power grid is in the state of disturbance, so as to obtain a stable AC voltage that is synchronized with the disturbance in the preset power grid, and to integrate the stable AC voltage into the preset power grid.

[0307] The power release unit is used to release power through a preset energy storage module when the preset grid voltage drops, in order to compensate for the voltage deviation caused by the grid voltage drop, obtain an AC voltage that meets the preset requirements for continuous grid connection, and then connect the AC voltage that meets the preset requirements for continuous grid connection into the preset grid. Here, a grid voltage drop means that the voltage of the preset grid is lower than the preset voltage rating after a preset time period.

[0308] In one possible design, the power release unit includes:

[0309] The second acquisition component is used to acquire the magnitude and duration of the voltage drop in the power grid.

[0310] The second generation component is used to generate a power allocation strategy for a preset energy storage system based on the drop magnitude and drop duration; wherein the energy storage system includes a capacitor and a lithium battery, the capacitor is used to provide instantaneous power compensation, and the lithium battery is used to provide continuous power compensation.

[0311] The discharge component is used to control the discharge of capacitors and lithium batteries according to the power distribution strategy to compensate for the voltage deviation caused by the grid voltage drop and obtain an AC voltage that meets the preset requirements for continuous grid-connected operation.

[0312] The DC boost grid-connected device provided in this embodiment can perform... Figure 2 and Figure 3 The technical solution of the DC boost grid connection method embodiment shown herein, its implementation principle and technical effects are similar to Figure 2 and Figure 3 The embodiment of the DC boost grid connection method shown is similar and will not be described in detail here.

[0313] Figure 12 This is a schematic diagram of the hardware structure of the electronic device provided in an embodiment of this application. Figure 12 As shown, the electronic device 120 includes at least one processor 1201 and a memory 1202. The electronic device 120 also includes a communication component 1203. The processor 1201, the memory 1202, and the communication component 1203 are connected via a bus 1204.

[0314] In a specific implementation, at least one processor 1201 executes computer execution instructions stored in memory 1202, causing at least one processor 1201 to implement a DC boost grid-connected method according to the above embodiment.

[0315] The specific implementation process of processor 1201 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0316] In the above embodiments, it should be understood that the processor 1201 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0317] The memory 1202 may include high-speed RAM memory, and may also include non-volatile memory (NVM), such as at least one disk storage.

[0318] Bus 1204 can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Bus 1204 can be divided into address bus, data bus, control bus, etc. For ease of illustration, bus 1204 in the accompanying drawings of this application is not limited to only one bus or one type of bus.

[0319] The above description of the functions implemented by electronic devices and main control devices has introduced the solutions provided by the embodiments of the present invention. It is understood that, in order to implement the above functions, the electronic device or main control device includes hardware structures and / or software modules corresponding to the execution of each function. By combining the units and algorithm steps of the various examples described in the embodiments of the present invention, the embodiments of the present invention can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed by hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the technical solutions of the embodiments of the present invention.

[0320] This application also provides a computer-readable storage medium storing computer-executable instructions. When executed by a processor, these instructions are used to implement a DC-DC boost grid-connected method as described in the above embodiments. In the specific implementation of the aforementioned DC-DC boost grid-connected method, each module can be implemented as a processor.

[0321] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0322] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in application-specific integrated circuits (ASICs). Alternatively, the processor and the readable storage medium can exist as discrete components in an electronic device or a host device.

[0323] This application also provides a computer program product, including a computer program, which, when executed by a processor, is used to implement a DC boost grid-connected method according to the above embodiments.

[0324] The computer program is stored in a readable storage medium, and at least one processor can read the computer program from the readable storage medium and execute the computer program to perform the scheme provided in any of the above embodiments.

[0325] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disk, or optical disk.

[0326] The technical solutions of this application have been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A DC boost grid-connected method, characterized in that, The method is applied to the control terminal of a DC-DC boost grid-connected system, which further includes a photovoltaic array and an H-bridge module group. The DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirements of the preset power grid are obtained. The DC voltage is adjusted according to the light intensity to match the light intensity, thereby obtaining the adjusted DC voltage. The number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group are adjusted according to the voltage requirement to obtain an adjusted H-bridge module group. The adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirement, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below a preset threshold during the adjustment process. The adjusted DC voltage is converted into a multi-level AC voltage that matches the voltage requirement according to the adjusted H-bridge module group, and the multi-level AC voltage is connected to the preset grid to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset grid; The step of adjusting the number of H-bridge modules and the switching timing of the H-bridge modules in the H-bridge module group according to the voltage requirement to obtain the adjusted H-bridge module group includes: Obtain the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output of the H-bridge module group; The number of modules to be put into operation and the number of modules to be bypassed are calculated based on the voltage requirement and the peak value; wherein, the number of modules to be put into operation refers to the number of H-bridge modules in the H-bridge module group that need to be put into operation, and the number of modules to be bypassed refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed. Based on the number of modules to be deployed, multiple modules to be deployed are determined from the H-bridge modules that have not been deployed in the H-bridge module group, and multiple bypass modules to be bypassed are determined from the H-bridge modules that have been deployed in the H-bridge module group. Based on the voltage phase and the resonant frequency, determine the activation time of each module to be activated and the bypass time of each module to be bypassed. The input operation of each module to be input is performed according to the input time, and the bypass operation of each module to be bypassed is performed according to the bypass time, so as to obtain the adjusted H-bridge module group.

2. The DC boost grid connection method according to claim 1, characterized in that, The photovoltaic array includes multiple photovoltaic strings. Adjusting the DC voltage according to the light intensity to match the light intensity, thus obtaining the adjusted DC voltage, includes: The ambient temperature of the environment in which the photovoltaic array is located, the output voltage and output power of each photovoltaic string, and the current voltage value of the DC side capacitor of each H-bridge module in the H-bridge module group are obtained. Based on the output power and the light intensity, determine the target voltage value of each photovoltaic string when it reaches the preset maximum output power under the light intensity conditions; The target voltage value is corrected by temperature compensation based on the ambient temperature to obtain the corrected target voltage value for each photovoltaic string. Based on the deviation between the output voltage of each photovoltaic string and the corrected target voltage value of each photovoltaic string, a voltage adjustment command is generated for each photovoltaic string; wherein, the voltage adjustment command is used to adjust the preset duty cycle of the voltage regulation unit in each photovoltaic string so that the output voltage of each photovoltaic string converges to the corrected target voltage value of each photovoltaic string. The preset duty cycle is adjusted according to the voltage adjustment command to obtain the adjusted output voltage of each photovoltaic string, and the adjusted output voltages of each photovoltaic string are combined to obtain the adjusted DC voltage.

3. The DC boost grid connection method according to claim 2, characterized in that, The step of determining multiple modules to be deployed from the H-bridge modules that have not been deployed in the H-bridge module group based on the number of deployed modules, and determining multiple modules to be bypassed from the H-bridge modules that have been deployed in the H-bridge module group based on the number of bypass modules, includes: Obtain the first real-time voltage value of the DC side capacitor of the H-bridge module that is not in the H-bridge module group, and sort the H-bridge modules that are not in the H-bridge module group in ascending order according to the deviation between the first real-time voltage value and the preset reference value, and determine the H-bridge modules that are the first number of modules in the ascending order as the plurality of modules to be put into the group. The H-bridge modules already in the H-bridge module group are arranged in descending order based on the deviation between the current voltage value and the preset reference value, and the H-bridge modules with the highest number of bypass modules in the descending order are determined as the plurality of bypass modules.

4. The DC boost grid connection method according to claim 1, characterized in that, The step of converting the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement based on the adjusted H-bridge module group includes: Based on a preset carrier phase-shifting PWM strategy, a PWM drive signal is generated for each H-bridge module in the H-bridge module group. The adjusted DC voltage is input to each H-bridge module, and the switching state of multiple switches in each H-bridge module is controlled according to the PWM drive signal, so that each H-bridge module converts the adjusted DC voltage into AC voltage, and obtains the AC voltage output by each H-bridge module. The AC voltages output by each H-bridge module are superimposed to obtain the multi-level AC voltage.

5. The DC boost grid connection method according to claim 4, characterized in that, The method of generating PWM drive signals for each H-bridge module in the H-bridge module group based on a preset carrier phase-shift PWM strategy includes: Obtain the DC-side capacitor voltage of the target H-bridge module; wherein, the target H-bridge module is any one of the H-bridge modules in the H-bridge module group; Based on the deviation between the DC-side capacitor voltage of the target H-bridge module and the preset voltage equalization reference value, a voltage equalization correction amount for the target H-bridge module is generated. The PWM drive signal for the target H-bridge module is generated based on the preset carrier phase-shift PWM strategy and the voltage equalization correction amount.

6. The DC boost grid connection method according to claim 5, characterized in that, After generating the PWM drive signal for the target H-bridge module according to the preset carrier phase-shift PWM strategy and the voltage equalization correction amount, the method further includes: The PWM drive signal is input to the target H-bridge module to adjust the duty cycle of the switches in the target H-bridge module, so that the DC-side capacitor voltage of the target H-bridge module converges to the preset voltage equalization reference value. If the DC-side capacitor voltage of the target H-bridge module exceeds a preset fault threshold and the duration exceeds a preset time threshold under the action of the PWM drive signal, the target H-bridge module is determined to be a permanent fault, and the target H-bridge module is bypassed and replaced by a preset backup H-bridge module.

7. The DC boost grid connection method according to claim 1, characterized in that, The step of integrating the multi-level AC voltage into the preset power grid includes: Obtain the state of the preset power grid; When the preset power grid is in a state of disturbance, the frequency and phase of the multi-level AC voltage are adjusted to obtain a stable AC voltage that is synchronized with the disturbance in the preset power grid, and the stable AC voltage is then incorporated into the preset power grid. When the preset grid state is such that the grid voltage drops, power is released through the preset energy storage module to compensate for the voltage deviation caused by the grid voltage drop, so as to obtain an AC voltage that meets the preset grid-connected continuous operation requirements, and the AC voltage that meets the preset grid-connected continuous operation requirements is connected to the preset grid; wherein, the grid voltage drops refer to the voltage of the preset grid being lower than the preset voltage rating after a preset time period.

8. The DC boost grid connection method according to claim 7, characterized in that, The process of releasing power through a preset energy storage module to compensate for voltage deviations caused by grid voltage drops, thereby obtaining an AC voltage that meets the preset requirements for continuous grid-connected operation, includes: Obtain the magnitude and duration of the voltage drop in the power grid; Based on the drop amplitude and the drop duration, a power allocation strategy for a preset energy storage system is generated; wherein, the energy storage system includes a capacitor and a lithium battery, the capacitor is used to provide instantaneous power compensation, and the lithium battery is used to provide continuous power compensation; The capacitor and lithium battery are controlled to discharge according to the power distribution strategy to compensate for the voltage deviation caused by the grid voltage drop, so as to obtain an AC voltage that meets the preset requirements for continuous grid-connected operation.

9. A DC boost grid-connected system, characterized in that, include: Photovoltaic arrays are used to output DC voltage; The control terminal is used to acquire the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirement of the preset power grid, and adjust the DC voltage according to the light intensity to match the DC voltage with the light intensity, so as to obtain the adjusted DC voltage; The H-bridge module group is used to adjust the number and switching time of the H-bridge modules according to the voltage requirements to obtain the adjusted H-bridge module group; wherein, the adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirements, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below a preset threshold during the adjustment process. The control terminal is also used to convert the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement according to the adjusted H-bridge module group, and to connect the multi-level AC voltage into the preset grid, so as to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset grid; The step of adjusting the number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group according to the voltage requirements to obtain the adjusted H-bridge module group includes: obtaining the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group; The number of modules to be put into operation and the number of modules to be bypassed are calculated based on the voltage requirement and the peak value; wherein, the number of modules to be put into operation refers to the number of H-bridge modules in the H-bridge module group that need to be put into operation, and the number of modules to be bypassed refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed. Based on the number of modules to be deployed, multiple modules to be deployed are determined from the H-bridge modules that have not been deployed in the H-bridge module group, and multiple bypass modules to be bypassed are determined from the H-bridge modules that have been deployed in the H-bridge module group. Based on the voltage phase and the resonant frequency, determine the activation time of each module to be activated and the bypass time of each module to be bypassed. The input operation of each module to be input is performed according to the input time, and the bypass operation of each module to be bypassed is performed according to the bypass time, so as to obtain the adjusted H-bridge module.

10. A DC boost grid-connected device, characterized in that, A control terminal for a DC-DC boost grid-connected system, the DC-DC boost grid-connected system further including a photovoltaic array and an H-bridge module group, the device comprising: The first acquisition module is used to acquire the DC voltage output by the photovoltaic array, the light intensity of the environment where the photovoltaic array is located, and the voltage requirement of the preset power grid. The first adjustment module is used to adjust the DC voltage according to the light intensity so that the DC voltage matches the light intensity, thereby obtaining the adjusted DC voltage; The second adjustment module is used to adjust the number of H-bridge modules and the switching time of the H-bridge modules in the H-bridge module group according to the voltage requirement, so as to obtain the adjusted H-bridge module group; wherein, the adjustment is used to match the peak value of the multi-level AC voltage output by the adjusted H-bridge module group with the voltage requirement, while keeping the harmonic distortion rate and amplitude fluctuation rate of the multi-level AC voltage below a preset threshold during the adjustment process. The conversion module is used to convert the adjusted DC voltage into a multi-level AC voltage that matches the voltage requirement according to the adjusted H-bridge module group, and to connect the multi-level AC voltage into the preset power grid, so as to realize the step-up grid connection of the DC power of the photovoltaic array to the AC power of the preset power grid; The second adjustment module includes: The second acquisition unit is used to acquire the voltage phase of the preset power grid and the resonant frequency of the filter circuit at the output end of the H-bridge module group; The first calculation unit is used to calculate the number of input modules and the number of bypass modules based on the voltage requirement and the peak value; wherein, the number of input modules refers to the number of H-bridge modules in the H-bridge module group that need to be input, and the number of bypass modules refers to the number of H-bridge modules in the H-bridge module group that need to be bypassed; The second determining unit is used to determine multiple modules to be put into operation from the H-bridge modules that have not been put into the H-bridge module group according to the number of the input modules, and to determine multiple modules to be bypassed from the H-bridge modules that have been put into the H-bridge module group according to the number of bypass modules. The third determining unit is used to determine the activation time of each module to be activated and the bypass time of each module to be bypassed based on the voltage phase and the resonant frequency. An execution unit is used to perform the input operation of each module to be input according to the input time, and to perform the bypass operation of each module to be bypassed according to the bypass time, so as to obtain the adjusted H-bridge module group.

11. An electronic device, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; When the processor executes the computer execution instructions stored in the memory, it is used to implement the DC boost grid-connected method as described in any one of claims 1 to 8.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the DC boost grid-connected method as described in any one of claims 1 to 8.

13. A computer program product, characterized in that, Includes a computer program, which, when executed by a processor, is used to implement the DC boost grid-connected method as described in any one of claims 1 to 8.

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