Mppt control method, device, controller and photovoltaic system
By determining the first and second target converter modes based on the target voltage of the DC power supply in the photovoltaic converter system, the circuit loss problem caused by the rise in bus voltage is solved, and the efficient operation and reliability improvement of the power conversion device are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN KEHUA DIGITAL ENERGY TECH CO LTD
- Filing Date
- 2022-05-31
- Publication Date
- 2026-07-03
AI Technical Summary
In a multi-channel photovoltaic converter system, when the input voltage of one converter is high, the bus voltage rises, causing the output of other converters to increase, which increases circuit losses.
By acquiring the target voltage of each DC power supply, the first target converter is determined and controlled to be in the second mode. Other converters are determined to be the second target converter based on the comparison between the target voltage and the bus voltage and are controlled to be in the second mode, thereby reducing the bus voltage and reducing the stress and power consumption of the converter devices.
It effectively reduces bus voltage, reduces power conversion device losses and improves operational reliability, reduces switching transistor stress, and reduces inverter inductor losses and ripple.
Smart Images
Figure CN115021559B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power conversion technology, and in particular to an MPPT control method, device, controller, and photovoltaic system. Background Technology
[0002] With the development of photovoltaics, the number of converters with MPPT (Maximum Power Point Tracking, solar controller) functionality is increasing. Most multi-channel converters with MPPT functionality are connected between independent DC power supplies and inverters.
[0003] Because DC power supplies are independent of each other, the input voltage delivered to each converter will also be different. Currently, the common practice is to determine the bus voltage based on the highest input voltage of each branch and the mains voltage. However, when the input voltage of a converter in one branch is higher, it may cause the bus voltage to rise, leading to increased output voltage in the remaining converters and increased circuit losses. Summary of the Invention
[0004] This invention provides an MPPT control method, device, controller, and photovoltaic system to solve the problem that when the input voltage of a certain converter is high, the output bus voltage may rise, leading to increased output of other converters and increased circuit losses.
[0005] In a first aspect, the present invention provides an MPPT control method applied to a power conversion device including multiple DC power supplies, multiple first converters, and second converters; the multiple first converters have their input terminals connected to the multiple DC power supplies one-to-one, and their output terminals connected to the second converters; each first converter includes a first mode or a second mode; the first mode is used to indicate that the DC power supply corresponding to the first converter is subject to MPPT control by the first converter, and the second mode is used to indicate that the DC power supply corresponding to the first converter is subject to MPPT control by the second converter; the method may include:
[0006] The system acquires target voltages from multiple DC power supplies. These target voltages characterize the maximum output voltage of the DC power supply under MPPT control. When the maximum target voltage meets the startup conditions of the second converter, the first converter corresponding to the DC power supply with the maximum target voltage is identified as the first target converter, and the first target converter is controlled to be in the second mode. The system compares the target voltages of other DC power supplies (excluding the DC power supply with the maximum target voltage) with the current input voltage of the second converter to identify the second target converter, and controls the second target converter to be in the second mode. The system also controls other first converters (excluding the first target converter and the second target converter) to be in the first mode.
[0007] In one possible implementation, comparing the target voltage of a DC power supply other than the DC power supply with the current input voltage of the second converter to determine the second target converter may include: calculating the absolute value of the difference between the target voltage of the DC power supply other than the DC power supply with the maximum target voltage and the current input voltage of the second converter; and marking the first converter corresponding to the DC power supply whose absolute value of the difference is less than a preset absolute value of the difference as the second target converter.
[0008] In one possible implementation, comparing the target voltage of a DC power supply other than the DC power supply with the current input voltage of the second converter to determine the second target converter may include: calculating the ratio of the target voltage of the DC power supply other than the DC power supply with the current input voltage of the second converter; and marking the first converter corresponding to the DC power supply with a ratio less than a preset ratio as the second target converter.
[0009] In one possible implementation, the maximum target voltage satisfies the startup conditions of the second converter, including: the maximum target voltage is not less than the startup voltage of the second converter.
[0010] In one possible implementation, the multiple first converters are multiple DC / DC converter circuits with MPPT control function, the second converter is an inverter circuit with MPPT control function, and the multiple DC power supplies are multiple photovoltaic strings; the input terminals of the multiple DC / DC converter circuits are connected one-to-one with the multiple photovoltaic strings; the output terminals of the multiple DC / DC converter circuits are connected in parallel to the input terminals of the second converter; the output terminal of the second converter is connected to the power grid through a filter circuit; wherein, the photovoltaic strings corresponding to the DC / DC converter circuit in the first mode are MPPT controlled by the first converter, and the photovoltaic strings corresponding to the DC / DC converter circuit in the second mode are MPPT controlled by the inverter circuit.
[0011] Secondly, the present invention provides an MPPT control device applied to a power conversion device including multiple DC power supplies, multiple first converters, and multiple second converters; the multiple first converters have their input terminals connected to the multiple DC power supplies one-to-one, and their output terminals connected to the second converters; each first converter includes a first mode or a second mode; the first mode is used to indicate that the DC power supply corresponding to the first converter is MPPT controlled by the first converter, and the second mode is used to indicate that the DC power supply corresponding to the first converter is MPPT controlled by the second converter; the control device includes an acquisition module, a first control module, and a second control module.
[0012] The acquisition module is used to acquire the target voltages of multiple DC power supplies; the target voltage is used to characterize the maximum output voltage of the DC power supply under MPPT control; the first control module is used to determine the first converter corresponding to the DC power supply with the maximum target voltage as the first target converter when the maximum target voltage meets the start-up conditions of the second converter, and control the first target converter to be in the second mode; the second control module is used to compare the target voltages of other DC power supplies besides the DC power supply with the current input voltage of the second converter, determine the second target converter, control the second target converter to be in the second mode, and control other first converters besides the first target converter and the second target converter to be in the first mode.
[0013] In one possible implementation, the second control module includes a first calculation unit and a first comparison unit. The first calculation unit is used to calculate the absolute value of the difference between the target voltage of a DC power supply other than the DC power supply where the maximum target voltage is located and the current input voltage of the second converter; the first comparison unit is used to mark the first converter corresponding to the DC power supply whose absolute difference value is less than a preset absolute difference value as the second target converter.
[0014] Thirdly, the present invention provides a controller, including a memory and a processor, wherein the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the steps of the MPPT control method as described in the first aspect or any possible implementation of the first aspect.
[0015] Fourthly, the present invention provides a photovoltaic system, including a controller and a photovoltaic inverter as described in the third aspect above; the photovoltaic inverter is controlled by the controller.
[0016] Fifthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the MPPT control method as described in the first aspect or any possible implementation of the first aspect.
[0017] This invention provides an MPPT control method, controller, and photovoltaic system applied to a power conversion device comprising multiple DC power supplies, multiple first converters, and multiple second converters. The method determines a first target converter based on the target voltage of the DC power supply, and a second target converter based on the target voltage and the current input voltage of the second converter. Subsequently, the first and second target converters are controlled in a second mode, while the other first converters are controlled in a first mode. This allows the multiple DC power supplies to employ different MPPT tracking methods, reducing the output bus voltage of the multiple first converters, decreasing device stress and power consumption of each first converter, and thereby improving the operational reliability of the power conversion device. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of an application scenario provided by an embodiment of the present invention;
[0020] Figure 2 This is a schematic diagram of another application scenario provided by an embodiment of the present invention;
[0021] Figure 3 This is a flowchart illustrating the implementation of the MPPT control method provided in this embodiment of the invention.
[0022] Figure 4 This is a schematic diagram of the MPPT control device provided in an embodiment of the present invention;
[0023] Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Detailed Implementation
[0024] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.
[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.
[0026] Figure 1 This is a schematic diagram of an application scenario provided by an embodiment of the present invention. For example... Figure 1 As shown, the power conversion device may include N DC power sources, N first converters, and one second converter. Each DC power source corresponds to one first converter, and N ≥ 2, which is a positive integer. Each input terminal of the multiple first converters is connected to one of the multiple DC power sources, and each output terminal is connected to the second converter. The DC power sources supply power to the power grid through the first and second converters. The connection between the first and second converters is the bus.
[0027] Optionally, the first converter includes a first mode or a second mode. The first mode indicates that the DC power supply corresponding to the first converter is controlled by the first converter using MPPT (Multi-Purpose Test and Response Time), and the second mode indicates that the DC power supply corresponding to the first converter is controlled by the second converter using MPPT. Both the first and second converters have MPPT functionality.
[0028] Specifically, in the first mode, the DC power supply corresponding to the first converter is controlled by the first converter through MPPT (Multi-Purpose Test and Power Supply) so that the DC power supply supplies power to the second converter through the first converter. In the second mode, the DC power supply corresponding to the first converter is controlled by the second converter through MPPT so that the DC power supply supplies power directly to the second converter.
[0029] For example, when the first converter 1 is in the first mode, it performs MPPT control on the DC power supply 1, so that the DC power supply 1 supplies power to the second converter through the first converter 1. In this mode, the first converter performs power conversion. When the first converter 1 is in the second mode, it performs MPPT control on the DC power supply 2, so that the DC power supply 1 directly supplies power to the second converter. In this mode, the second converter acts as a bypass, allowing the DC power supply to be directly connected to the second converter through a diode or bypass relay in the first converter.
[0030] like Figure 2 As shown, this illustrates another application scenario provided by an embodiment of the present invention. Figure 2 As shown, in some embodiments of the present invention, the multiple first converters are multiple DC / DC converter circuits with MPPT control function, the second converter is an inverter with MPPT control function, and the multiple DC power supplies are multiple photovoltaic strings (PV). The input terminals of the multiple DC / DC converter circuits are connected one-to-one with the multiple photovoltaic strings; the output terminals of the multiple DC / DC converter circuits are connected in parallel to the input terminals of the second converter; the output terminal of the second converter is connected to the power grid through a filter circuit; wherein, the photovoltaic strings corresponding to the DC / DC converter circuit in the first mode are MPPT controlled by the first converter, and the photovoltaic strings corresponding to the DC / DC converter circuit in the second mode are MPPT controlled by the inverter circuit. The DC / DC converter circuit typically employs a Boost circuit.
[0031] Optionally, the DC / DC-1 has MPPT control functionality, and the inverter also has MPPT control functionality. Each first converter, in addition to its DC / DC conversion circuit, also has a bypass circuit, each with a bypass switch K. By controlling the bypass switch, the first converter can be controlled to operate in either the first or second mode.
[0032] For example, when the bypass switch K1 is closed, the photovoltaic string PV-1 supplies power to the inverter through the K1 branch. At this time, the first converter 1 is in the second mode, and the inverter performs MPPT control on PV-1. When the bypass switch K1 is open, the photovoltaic string PV-1 supplies power to the inverter through the DC / DC-1 branch of the conversion circuit. At this time, the first converter 1 is in the first mode, and the DC / DC-1 performs MPPT control on PV1. The same applies to other first converters, and will not be described in detail here.
[0033] In practical applications, during power plant startup, each DC power supply is typically controlled by its corresponding first converter using MPPT (Multi-Level Testing). However, since the DC power supplies are independent, the bus voltage during power conversion startup is generally determined by the input voltage of the first converter and the grid voltage. If the input voltage of a DC power supply to the first converter is too high, it may cause the bus voltage to rise. Other first converters must then raise their output voltage, leading to increased switching time, inductor ripple, and losses in these converters. It may also increase stress on the switching transistors, reducing product reliability.
[0034] To address the above problems, this invention proposes an MPPT control method. See also... Figure 3 This illustrates a flowchart of the MPPT control method provided in an embodiment of the present invention. Figure 3 As shown, an MPPT control method is applied to, for example... Figure 1 The power conversion device shown may include S101, S102, and S103, as follows:
[0035] S101, obtain the target voltage of multiple DC power supplies; the target voltage is used to characterize the maximum output voltage of the DC power supply under MPPT control.
[0036] Optionally, the power conversion device may include N DC power supplies, where N ≥ 2 and is a positive integer. Each DC power supply can output DC voltage. Each DC power supply can correspond to a target voltage, which represents the maximum output voltage of the DC power supply under MPPT control. The target voltage can be calculated based on the open-circuit voltage of the DC power supply or measured according to actual conditions. Generally, the target voltage of the DC power supply is 80% of its open-circuit voltage. For example, depending on the characteristics of different DC power supplies, the target voltage = (0.7~0.85) * open-circuit voltage.
[0037] For example, if the open-circuit voltage of DC power supply 1 is 800V, then the target voltage of DC power supply 1 is 640V. The same applies to other DC power supplies, which will not be elaborated here.
[0038] S102, when the maximum target voltage meets the start-up conditions of the second converter, the first converter corresponding to the DC power supply where the maximum target voltage is located is determined as the first target converter, and the first target converter is controlled to be in the second mode.
[0039] Optionally, the MPPT control method provided in this embodiment of the invention is generally applied during the startup of a power conversion device, specifically during the startup of the second converter of the power conversion device. The second converter can be an inverter. The DC power supply will supply power to the second converter through the first converter or directly to the second converter. By judging the relationship between the target voltage and the startup voltage of the second converter, it can be determined whether the second converter meets the startup conditions.
[0040] Specifically, the second converter meets the startup condition when the target voltage of at least one DC power supply is not less than the startup voltage of the second converter. Alternatively, the second converter meets the startup condition when the maximum target voltage among all target voltages is not less than the startup voltage of the second converter.
[0041] Optionally, when the start-up conditions of the second converter are met, the first converter corresponding to the DC power supply with the highest target voltage among all target voltages can be selected as the first target converter. Subsequently, the first target converter is controlled to enter the second mode so that the DC power supply corresponding to the first target converter can directly supply power to the second converter, and this DC power supply is controlled by the second converter using MPPT.
[0042] For example, the open-circuit voltage of DC power supply 1 is 800V, the open-circuit voltage of DC power supply 2 is 790V, the open-circuit voltage of DC power supply 3 is 750V, and the start-up voltage of the second converter is 600V. Calculations show that the target voltage of DC power supply 1 is 640V, the target voltage of DC power supply 2 is 632V, and the target voltage of DC power supply 3 is 600V. As can be seen from the above, the maximum target voltage of 640V is greater than the start-up voltage of the second converter of 600V. Therefore, the first converter 1 is controlled in the second mode so that DC power supply 1 directly supplies power to the second converter. In this case, DC power supply 1 is controlled by the second converter using MPPT.
[0043] S103, compare the target voltage of other DC power supplies (excluding the DC power supply with the maximum target voltage) with the current input voltage of the second converter, determine the second target converter, control the second target converter to be in the second mode, and control other first converters (excluding the first target converter and the second target converter) to be in the first mode.
[0044] Optionally, the current input voltage of the second converter is the current bus voltage of the power conversion device, which is also the current bus voltage after the first target converter is controlled in the second mode. After the first target converter is controlled in the second mode, the DC power supply with the maximum target voltage, i.e., the DC power supply corresponding to the first target converter, can be marked as the first target DC power supply. When the first target converter is controlled in the second mode, the output voltage of the first DC target power supply is the output voltage of the first target converter, which is also the current bus voltage. The target voltages of all other DC power supplies besides the first target DC power supply are compared with the current input voltage of the second converter to determine the second target converter, which is the converter that is close to the first target converter.
[0045] Specifically, the absolute value, sum, ratio, etc., of the difference between each target voltage and the current bus voltage can be compared to determine the second target converter from the first converters other than the first target converter. There can be zero, one, or more second target converters, depending on the comparison results. After determining the second target converters, all second target converters are controlled to enter a second mode, so that the DC power supply corresponding to each second target converter directly supplies power to the second converter.
[0046] Optionally, after controlling the first target converter and all second target converters to be in the second mode, the remaining first converters are controlled to be in the first mode.
[0047] This invention first determines a first target converter by setting a target voltage and controls it to a second mode. This allows a second converter to perform MPPT control on the DC power supply corresponding to the first target converter, thereby reducing bus voltage, power conversion device losses, and improving efficiency. Then, a second target converter is determined based on the current bus voltage and the target voltage, and all second target converters are also controlled in the second mode to further reduce power conversion device losses and improve efficiency. Determining the first target converter first facilitates the rapid selection of the second target converter while reducing power conversion device losses, and lowering the bus voltage simplifies the selection of the second target converter. Furthermore, for the remaining first converters still in the first mode, even though these first converters still require two-stage conversion during the MPPT process, the bus voltage effectively reduced by the soft-start method compared to direct start-up effectively reduces the stress and losses of the components within these first converters.
[0048] In some embodiments of the present invention, the step of "comparing the target voltage of a DC power supply other than the DC power supply where the maximum target voltage is located with the current input voltage of the second converter and determining the second target converter" in S103 above may include at least two cases.
[0049] The first method involves calculating the ratio of the target voltage of the DC power supply other than the DC power supply with the maximum target voltage to the current input voltage of the second converter; and marking the first converter corresponding to the DC power supply with a ratio less than a preset ratio as the second target converter.
[0050] The second method involves calculating the absolute value of the difference between the target voltage of other DC power supplies (excluding the DC power supply with the maximum target voltage) and the current input voltage of the second converter; and marking the first converter corresponding to the DC power supply with a difference absolute value less than a preset difference absolute value as the second target converter.
[0051] Optionally, a ratio less than a preset ratio or an absolute difference less than a preset absolute difference indicates that the two are relatively close. The target voltage of a DC power supply other than the first target DC power supply is compared with the current bus voltage, and the ratio or absolute difference between the two is calculated. The first converter corresponding to a DC power supply with a ratio less than the preset ratio or an absolute difference less than the preset absolute difference is marked as the second target converter. The number of second target converters can be zero, one, or more. The preset absolute difference and preset ratio can be determined based on historical data or experimental simulation, depending on the actual situation. For example, the preset absolute difference is generally between 10V and 30V.
[0052] For example, the target voltage of DC power supply 1 is 640V, the target voltage of DC power supply 2 is 632V, and the target voltage of DC power supply 3 is 600V, with a preset absolute difference of 20V. After the first converter 1 is controlled in the second mode, the current bus voltage is 640V.
[0053] The absolute difference between the target voltage and the current bus voltage of DC power supply 2 is 8V. Since 8V is less than 20V, the first converter 2 is marked as the second target converter, and it is controlled to be in the second mode. The absolute difference between the target voltage and the current bus voltage of DC power supply 3 is 40V. Since 40V is greater than 20V, the first converter 3 is controlled to be in the first mode. In summary, the first converters 1 and 2 are controlled in the second mode, and the second converter performs MPPT control on DC power supply 1 and DC power supply 2. The first converter 3 is controlled in the first mode, and it performs MPPT control on DC power supply 3.
[0054] The MPPT control method of this invention enables soft starting of the power conversion device. Compared with existing direct starting methods, it can reduce the bus voltage by more than 15%, significantly reducing the stress on the switching transistors in the first converter and improving operational reliability. Simultaneously, when the second converter is an inverter, it can also significantly reduce the voltage difference across the inverter inductor, reducing inductor losses and circuit ripple.
[0055] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
[0056] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above. Figure 4 A schematic diagram of the MPPT control device provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below:
[0057] like Figure 4 As shown, the MPPT control device 20 is applied to a power conversion device including multiple DC power supplies, multiple first converters, and multiple second converters; each of the multiple first converters has its input terminal connected to one of the multiple DC power supplies, and each of its output terminals connected to a second converter; each first converter includes a first mode or a second mode; the first mode is used to indicate that the DC power supply corresponding to the first converter is MPPT controlled by the first converter, and the second mode is used to indicate that the DC power supply corresponding to the first converter is MPPT controlled by the second converter.
[0058] The control device 20 may include an acquisition module 201, a first control module 202, and a second control module 203. The acquisition module 201 acquires target voltages from multiple DC power supplies; the target voltage characterizes the maximum output voltage of the DC power supply under MPPT control. The first control module 202, when the maximum target voltage meets the startup conditions of the second converter, identifies the first converter corresponding to the DC power supply with the maximum target voltage as the first target converter and controls the first target converter to be in a second mode. The second control module 203 compares the target voltages of other DC power supplies besides the DC power supply with the current input voltage of the second converter, identifies the second target converter, controls the second target converter to be in the second mode, and controls other first converters besides the first and second target converters to be in a first mode.
[0059] In some embodiments of the present invention, the second control module 203 may include a first calculation unit and a first comparison unit. The first calculation unit is used to calculate the absolute value of the difference between the target voltage of a DC power supply other than the DC power supply where the maximum target voltage is located and the current input voltage of the second converter. The first comparison unit is used to mark the first converter corresponding to the DC power supply whose absolute difference value is less than a preset absolute difference value as the second target converter.
[0060] In some embodiments of the present invention, the second control module 203 may further include a second calculation unit and a second comparison unit. The second calculation unit is used to calculate the ratio of the target voltage of a DC power supply other than the DC power supply with the maximum target voltage to the current input voltage of the second converter. The second comparison unit is used to mark the first converter corresponding to the DC power supply with a ratio less than a preset ratio as the second target converter.
[0061] In some embodiments of the present invention, the maximum target voltage satisfies the start-up conditions of the second converter, including: the maximum target voltage is not less than the start-up voltage of the second converter.
[0062] In some embodiments of the present invention, the plurality of first converters are plurality of DC / DC converter circuits with MPPT control function, the second converter is an inverter circuit with MPPT control function, and the plurality of DC power supplies are plurality of photovoltaic strings; the input terminals of the plurality of DC / DC converter circuits are respectively connected one-to-one with the plurality of photovoltaic strings; the output terminals of the plurality of DC / DC converter circuits are connected in parallel to the input terminal of the second converter; the output terminal of the second converter is connected to the power grid through a filter circuit; wherein, the photovoltaic string corresponding to the DC / DC converter circuit in the first mode is MPPT controlled by the first converter, and the photovoltaic string corresponding to the DC / DC converter circuit in the second mode is MPPT controlled by the inverter circuit.
[0063] Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 5 As shown, the controller 30 in this embodiment includes a processor 300 and a memory 301. The memory 301 stores a computer program 302 that can run on the processor 300. When the processor 300 executes the computer program 302, it implements the steps in the various MPPT control method embodiments described above, for example... Figure 3 S101 to S103 are shown. Alternatively, when the processor 300 executes the computer program 302, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 4 The functions of modules 201 to 203 are shown.
[0064] For example, computer program 302 can be divided into one or more modules / units, one or more of which are stored in memory 301 and executed by processor 300 to complete the present invention. One or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 302 in controller 30. For example, computer program 302 can be divided into... Figure 4 Modules 201 to 203 are shown.
[0065] The controller 30 may be a DSP chip, a microcontroller chip, or a central control circuit. The controller 30 may include, but is not limited to, a processor 300 and a memory 301. Those skilled in the art will understand that... Figure 5 This is merely an example of controller 30 and does not constitute a limitation on controller 30. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.
[0066] The processor 300 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.
[0067] The memory 301 can be an internal storage unit of the controller 30, such as a hard disk or RAM of the controller 30. The memory 301 can also be an external storage device of the controller 30, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 30. Furthermore, the memory 301 can include both internal and external storage units of the controller 30. The memory 301 is used to store computer programs and other programs and data required by the controller. The memory 301 can also be used to temporarily store data that has been output or will be output.
[0068] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.
[0069] This invention also provides a photovoltaic system, including the controller 30 and the photovoltaic inverter as described above; the photovoltaic inverter is controlled by the controller 30.
[0070] Optionally, the structure of the photovoltaic inverter can be as follows: Figure 1 or Figure 2 As shown.
[0071] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.
[0072] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software 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 implementations should not be considered beyond the scope of this invention.
[0073] In the embodiments provided by this invention, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.
[0074] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.
[0075] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.
[0076] If integrated modules / units are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various MPPT control method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.
[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A method of MPPT control, characterized by, An application is made to a power conversion device comprising multiple DC power supplies, multiple first converters, and multiple second converters; each of the multiple first converters has its input terminal connected to one of the multiple DC power supplies, and each of its output terminals connected to the second converter; the first converter includes a first mode and a second mode; The first mode is used to indicate that the DC power supply corresponding to the first converter is controlled by the first converter via MPPT, and the second mode is used to indicate that the DC power supply corresponding to the first converter is controlled by the second converter via MPPT. The control method includes: Obtain the target voltage of the plurality of DC power supplies; the target voltage is used to characterize the maximum output voltage of the DC power supply under MPPT control; When the maximum target voltage meets the start-up conditions of the second converter, the first converter corresponding to the DC power supply where the maximum target voltage is located is determined as the first target converter, and the first target converter is controlled to be in the second mode; The target voltage of a DC power supply other than the DC power supply where the maximum target voltage is located is compared with the current input voltage of the second converter to determine the second target converter, and the second target converter is controlled to be in the second mode, and other first converters other than the first target converter and the second target converter are controlled to be in the first mode.
2. The MPPT control method according to claim 1, characterized by, The step of comparing the target voltage of other DC power supplies besides the DC power supply where the maximum target voltage is located with the current input voltage of the second converter to determine the second target converter includes: calculating the absolute value of the difference between the target voltage of other DC power supplies besides the DC power supply where the maximum target voltage is located and the current input voltage of the second converter; and marking the first converter corresponding to the DC power supply whose absolute value of the difference is less than a preset absolute value of the difference as the second target converter.
3. The MPPT control method according to claim 1, characterized by, The step of comparing the target voltage of other DC power sources besides the DC power source where the maximum target voltage is located with the current input voltage of the second converter to determine the second target converter includes: calculating the ratio of the target voltage of other DC power sources besides the DC power source where the maximum target voltage is located to the current input voltage of the second converter; and marking the first converter corresponding to the DC power source with a ratio less than a preset ratio as the second target converter.
4. The MPPT control method according to claim 1, characterized by, The maximum target voltage satisfies the start-up conditions of the second converter, including: the maximum target voltage is not less than the start-up voltage of the second converter.
5. The MPPT control method according to any one of claims 1 to 4, characterized by, The plurality of first converters are plurality of DC / DC converter circuits with MPPT control function, the second converter is an inverter circuit with MPPT control function, and the plurality of DC power supplies are plurality of photovoltaic strings; the input terminals of the plurality of DC / DC converter circuits are respectively connected one-to-one with the plurality of photovoltaic strings; the output terminals of the plurality of DC / DC converter circuits are connected in parallel to the input terminals of the second converter; the output terminal of the second converter is connected to the power grid through a filter circuit; wherein, the photovoltaic strings corresponding to the DC / DC converter circuit in the first mode are MPPT controlled by the first converter, and the photovoltaic strings corresponding to the DC / DC converter circuit in the second mode are MPPT controlled by the inverter circuit.
6. An MPPT control device, characterized by comprising: An application is made to a power conversion device comprising multiple DC power supplies, multiple first converters, and multiple second converters; each of the multiple first converters has its input terminal connected to one of the multiple DC power supplies, and each of its output terminals connected to the second converter; the first converter includes a first mode and a second mode; The first mode is used to indicate that the DC power supply corresponding to the first converter is controlled by the first converter via MPPT, and the second mode is used to indicate that the DC power supply corresponding to the first converter is controlled by the second converter via MPPT; the control device includes an acquisition module, a first control module, and a second control module. The acquisition module is used to acquire the target voltage of the plurality of DC power supplies; the target voltage is used to characterize the maximum voltage output by the DC power supply under MPPT control; The first control module is configured to determine the first converter corresponding to the DC power supply where the maximum target voltage is located as the first target converter when the maximum target voltage meets the start-up conditions of the second converter, and control the first target converter to be in the second mode; The second control module is used to compare the target voltage of other DC power supplies besides the DC power supply where the maximum target voltage is located with the current input voltage of the second converter, determine the second target converter, control the second target converter to be in the second mode, and control other first converters besides the first target converter and the second target converter to be in the first mode.
7. The control device of claim 6, wherein The second control module includes a first calculation unit and a first comparison unit; the first calculation unit is used to calculate the absolute value of the difference between the target voltage of other DC power supplies besides the DC power supply where the maximum target voltage is located and the current input voltage of the second converter; the first comparison unit is used to mark the first converter corresponding to the DC power supply with a difference absolute value less than a preset difference absolute value as the second target converter.
8. A controller comprising a memory and a processor, the memory having stored therein a computer program executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the MPPT control method as described in any one of claims 1 to 5 above.
9. A photovoltaic system, characterized in that, It includes the controller and photovoltaic inverter as described in claim 8; the photovoltaic inverter is controlled by the controller.
10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the MPPT control method as described in any one of claims 1 to 5 above.