Photovoltaic inverter control method, device, and photovoltaic-storage integrated power supply system

Abstract

The present application relates to the field of energy storage technology, and in particular to a control method, device, and photovoltaic storage integrated power supply system for photovoltaic inverters. The method includes: when the energy storage inverter is off-grid, when the terminal power of the AC side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery, calculating the target output frequency of the photovoltaic inverter; calculating the single controlled frequency for each fine-tuning of the photovoltaic inverter based on the target output frequency, the current frequency of the photovoltaic inverter, and the first frequency before the last frequency regulation; controlling the energy storage inverter based on the single controlled frequency to achieve control of the photovoltaic inverter. This solves the problem that photovoltaic power generation in traditional systems cannot be utilized in an off-grid state, and ensures the safe operation of energy storage batteries and loads.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a control method and device for a photovoltaic inverter, and a photovoltaic-storage integrated power supply system. Background Art

[0002] In existing integrated photovoltaic and energy storage power supply systems, the energy storage inverter and the photovoltaic inverter typically utilize AC coupling. This means that the AC grid side of the energy storage inverter and the AC side of the photovoltaic inverter are connected to a common coupling point (PCC), where they are connected to the grid for power exchange. In essence, the photovoltaic inverter and the energy storage inverter operate independently. This structure creates a strong dependence on the grid. When the grid is absent, the photovoltaic inverter cannot function properly, and the electricity generated by the photovoltaic modules cannot be utilized by the photovoltaic inverter. Consequently, the system's energy utilization is low. Summary of the Invention

[0003] In view of the above problems, the present application provides a control method, device, and integrated photovoltaic and storage power supply system for a photovoltaic inverter, which overcomes the above problems or at least partially solves the technical problem of low energy utilization of the above integrated photovoltaic and storage power supply system.

[0004] According to one aspect of the present application, a control method for a photovoltaic inverter is provided, which is applied to a photovoltaic-storage integrated power supply system, wherein the photovoltaic-storage integrated power supply system includes an energy storage battery, an energy storage inverter, a photovoltaic inverter, a photovoltaic module and a load, wherein the DC side of the energy storage inverter is connected to the energy storage battery, the AC side grid terminal thereof is connected to the grid, and the AC side load terminal thereof is connected to the load; the DC side of the photovoltaic inverter is connected to the photovoltaic module, and the AC side thereof is connected to the load and the AC side load terminal of the energy storage inverter; the method includes the following steps: S1. When the energy storage inverter is off-grid, when the terminal power of the AC side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery, the photovoltaic module is calculated. The target output frequency of the inverter; S2. Obtain the current frequency of the photovoltaic inverter and the first frequency before the last frequency regulation, wherein the current frequency is the frequency of the photovoltaic inverter after the last frequency regulation; S3. Calculate the frequency increment for each fine-tuning of the photovoltaic inverter based on the target output frequency, the current frequency, and the first frequency; S4. Calculate the single controlled frequency for fine-tuning the photovoltaic inverter based on the frequency increment and the current frequency; S5. Control the energy storage inverter based on the single controlled frequency to achieve control of the photovoltaic inverter; S6. Repeat steps S2-S5 until the current frequency of the photovoltaic inverter is the target output frequency.

[0005] In an optional manner, the formula for calculating the target output frequency of the photovoltaic inverter in step S1 is:

[0006]

[0007] Among them, the is the target output frequency, the is the proportional coefficient of the photovoltaic inverter, is the maximum allowable charging power of the energy storage battery, is the load power;

[0008] described The calculation formula is:

[0009]

[0010] Among them, the is the maximum operating frequency of the photovoltaic inverter, is the minimum operating frequency of the photovoltaic inverter, is the frequency dead zone of the photovoltaic inverter, is the rated power of the photovoltaic inverter.

[0011] In an optional manner, the formula for the frequency increment in step S3 is:

[0012]

[0013] Among them, the is the frequency increment, the is the first experience value, is the second experience value, is the difference between the target output frequency and the current frequency, is the difference between the current frequency and the first frequency.

[0014] In an optional manner, the first experience value is 0.01, and the second experience value is 0.002.

[0015] In an optional manner, the step S5 includes: calculating a single controlled power of the energy storage inverter for single regulation according to the single controlled frequency; and controlling the energy storage inverter according to the single controlled power to achieve control of the photovoltaic inverter.

[0016] In an optional manner, the formula for calculating the single controlled power of the energy storage inverter for single regulation of power according to the single controlled frequency is:

[0017]

[0018] Among them, the is the single controlled power, the is the last controlled power of the energy storage inverter, is the single controlled frequency, the single controlled frequency is the sum of the current frequency and the frequency increment, is the rated frequency of the energy storage inverter, is the frequency dead zone of the energy storage inverter, is the proportional coefficient of the energy storage inverter.

[0019] In an optional manner, before step S1, the method further includes: obtaining the current output power of the photovoltaic inverter, the load power of the load, and the maximum allowable charging power of the energy storage battery; determining whether the current output power of the photovoltaic inverter is greater than the load power; if not, controlling the photovoltaic inverter and the energy storage inverter to collaboratively supply power to the load; if so, calculating the difference between the current output power of the photovoltaic inverter and the load power to obtain the terminal power of the AC side load terminal of the energy storage inverter; determining whether the terminal power is greater than the maximum allowable charging power of the energy storage battery; if so, executing step S1; if not, controlling the photovoltaic inverter to directly charge the energy storage battery through the energy storage inverter.

[0020] In an optional manner, the method further includes: when the energy storage inverter is connected to the grid, controlling the photovoltaic inverter to supply power to the load; obtaining the current output power of the photovoltaic inverter and the load power of the load; judging whether the current output power of the photovoltaic inverter is greater than the load power; if not, controlling the photovoltaic inverter and the energy storage inverter or the grid to collaboratively supply power to the load; if so, obtaining the difference between the current output power of the photovoltaic inverter and the load power to obtain the terminal power of the AC side load terminal of the energy storage inverter; and controlling the photovoltaic inverter to feed power to the grid through the energy storage inverter at the terminal power.

[0021] According to one aspect of the present application, a control device for a photovoltaic inverter is provided, which is applied to a photovoltaic-storage integrated power supply system, wherein the photovoltaic-storage integrated power supply system includes an energy storage battery, an energy storage inverter, a photovoltaic inverter, a photovoltaic module and a load, wherein the DC side of the energy storage inverter is connected to the energy storage battery, the AC side grid terminal thereof is connected to the grid, and the AC side load terminal thereof is connected to the load; the DC side of the photovoltaic inverter is connected to the photovoltaic module, and the AC side thereof is connected to the load and the AC side load terminal of the energy storage inverter; the control device includes: a first calculation module for calculating the target output frequency of the photovoltaic inverter when the energy storage inverter is off-grid and the terminal power of the AC side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery; an acquisition module , used to obtain the current frequency of the photovoltaic inverter and the first frequency before the last frequency regulation, the current frequency being the frequency of the photovoltaic inverter after the last frequency regulation; a second calculation module, used to calculate the frequency increment when the photovoltaic inverter is fine-tuned each time according to the target output frequency, the current frequency, and the first frequency; a third calculation module, used to calculate the single controlled frequency for fine-tuning the photovoltaic inverter according to the frequency increment and the current frequency; a control module, used to control the energy storage inverter according to the single controlled frequency to achieve control of the photovoltaic inverter, and control the execution of the acquisition module, the second calculation module, and the third calculation module until the current frequency of the photovoltaic inverter is the target output frequency.

[0022] According to one aspect of an embodiment of the present application, a photovoltaic and storage integrated power supply system is provided, which includes: at least one processor, and a memory, the memory being communicatively connected to the at least one processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the at least one processor so that the at least one processor can execute the method described above.

[0023] According to one aspect of an embodiment of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor performs the steps of the above method.

[0024] The beneficial effects of the present application include: the AC side of the photovoltaic inverter is no longer connected to the PCC point, but is connected to the load and the AC side load end of the energy storage inverter. When the energy storage inverter is operating off-grid, the electricity generated by the photovoltaic modules can be directly used to power the load through the photovoltaic inverter, and the remaining electricity can be used to charge the energy storage battery through the AC side load end of the energy storage inverter. This solves the problem that photovoltaic power generation in traditional systems cannot be used in an off-grid state. Photovoltaic energy can be consumed immediately by the load or stored in the battery, achieving maximum storage of photovoltaic energy, and significantly improving the overall energy utilization of the system. At the same time, the grid-connected line between the photovoltaic inverter and the PCC is eliminated, reducing the complexity of the system, and reducing the risk of disconnection due to grid fluctuations, thereby improving the stability of off-grid operation. Through the control method of the photovoltaic inverter, a progressive frequency adjustment strategy is adopted to control the frequency of the energy storage inverter to ensure the safe operation of the energy storage battery and the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0026] Figure 1 This is a schematic diagram of a photovoltaic and storage integrated power supply system in the prior art;

[0027] Figure 2 Schematic diagram of the photovoltaic and storage integrated power supply system provided in an embodiment of the present application;

[0028] Figure 3 Schematic diagram of the hardware structure of the controller provided in the embodiment of the present application;

[0029] Figure 4 1 is a flow chart of a photovoltaic inverter control method provided in an embodiment of the present application;

[0030] Figure 5 This is a schematic diagram of a flow chart for controlling an energy storage inverter according to a single controlled frequency provided in an embodiment of the present application;

[0031] Figure 6 This is a flow chart of another photovoltaic inverter control method provided by an embodiment of the present application;

[0032] Figure 7 1 is a flow chart of another photovoltaic inverter control method provided in an embodiment of the present application;

[0033] Figure 8 Schematic diagram of a photovoltaic inverter control device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described are part of the embodiments of the present application, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of this application.

[0035] In addition, the technical features involved in the embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0036] In order to facilitate readers to understand the inventive concept of this application, a brief description of the prior art photovoltaic storage integrated power supply system 100p is now given. Figure 1 The conventional integrated photovoltaic and energy storage power supply system 100p includes an energy storage inverter 10p, an energy storage battery 20p, a photovoltaic inverter 30p, a photovoltaic module 40p, and a load 50p. The DC side of the energy storage inverter 10p is connected to the energy storage battery 20p, and its AC side load terminal is connected to the load 50p. The DC side of the photovoltaic inverter 30p is connected to the photovoltaic module 40p. The AC side grid terminal of the energy storage inverter 10p and the AC side of the photovoltaic inverter 30p are connected to a common coupling (PCC) point, and are connected to the grid through the PCC to achieve power exchange.

[0037] The PV inverter 30p can be a centralized inverter, string inverter, or microinverter, with microinverters being preferred. Microinverters provide independent MPPT (maximum power point tracking) and DC / AC conversion for each PV module, significantly improving the system's overall power generation efficiency. This significantly reduces energy loss caused by string mismatches, especially when there's shading, aging, or orientation differences between modules. Furthermore, their low DC side voltage (typically less than 60V) significantly reduces the risk of high-voltage electric shock and fire, meeting stricter safety standards. Microinverters utilize a distributed architecture, ensuring that single-point failures won't affect the operation of other modules. This ensures high reliability and supports real-time module-level monitoring for precise operation and maintenance. The system offers flexible expansion, allowing for the addition and removal of modules without adjusting the original configuration. Designed for a lifespan of over 25 years, they are perfectly matched to PV modules, making them economical over the long term.

[0038] When the energy storage inverter 10p operates off-grid, there is no energy exchange between the energy storage inverter 10p and the grid, and the load 50p is powered only by the energy storage battery 20p.

[0039] When connected to the grid, the energy storage inverter 10p interacts with the grid in both directions: the grid can charge it or share load, and the energy storage inverter can also feed power back to the grid. When connected to the grid, the photovoltaic inverter 30p can feed the power generated by the photovoltaic panels 40p into the grid.

[0040] However, since the photovoltaic inverter 30p is not directly connected to the energy storage inverter 10p, when the photovoltaic inverter 30p is disconnected from the grid (such as due to a grid failure or planned off-grid operation), the electricity generated by the photovoltaic module 40p cannot be stored or utilized by the energy storage system, resulting in a decrease in the overall energy utilization rate of the system and a limited ability to absorb renewable energy.

[0041] Based on the technical problem of low energy utilization rate of the photovoltaic integrated power supply system 100p in the prior art, the embodiment of the present application provides a control method for a photovoltaic inverter. The method is applied in Figure 2 The illustrated integrated photovoltaic and energy storage power supply system 100 includes an energy storage inverter 10, an energy storage battery 20, a photovoltaic inverter 30, a photovoltaic module 40, and a load 50. The DC side of the energy storage inverter 10 is connected to the energy storage battery 20, its AC side grid terminal 102 is connected to the grid, and its AC side load terminal 101 is connected to the load 50. The DC side of the photovoltaic inverter 30 is connected to the photovoltaic module 40, and its AC side is connected to the load 50 and the AC side load terminal 101 of the energy storage inverter.

[0042] Unlike the structure in the prior art, the AC side of its photovoltaic inverter 30 is no longer connected to the PCC point, but is connected to the load 50 and the AC side load terminal 101 of the energy storage inverter 10. When the energy storage inverter 10 is operating off-grid, the electricity generated by the photovoltaic module 40 can be directly used to power the load 50 through the photovoltaic inverter 30, and the remaining electricity can be used to charge the energy storage battery 20 through the AC side load terminal 101 of the energy storage inverter 10, thereby maximizing the storage of photovoltaic energy. By establishing a direct connection channel between the photovoltaic inverter and the load / energy storage inverter, the problem of photovoltaic power generation in the traditional system being unusable in an off-grid state is solved. Photovoltaic energy can be consumed immediately by the load or stored in the battery, and the overall energy utilization rate of the system is greatly improved. At the same time, the grid-connected line between the photovoltaic inverter and the PCC is eliminated, reducing system complexity, reducing the risk of disconnection due to grid fluctuations, and improving off-grid operation stability.

[0043] It is understandable that the photovoltaic and storage integrated power supply system 100 may further include a controller 11, see Figure 3The controller 11 is responsible for monitoring the operating status of the integrated photovoltaic and storage power supply system 100 to ensure its safe and reliable operation. The controller 11 can actually monitor and collect the status parameters of the integrated photovoltaic and storage power supply system 100, perform necessary analysis and calculations on the relevant status parameters, obtain more status assessment parameters, and effectively manage and control the integrated photovoltaic and storage power supply system 100 according to specific protection and control strategies, thereby ensuring the safe and reliable operation of the entire integrated photovoltaic and storage power supply system 100.

[0044] Figure 3 The hardware structure diagram of the controller 11 provided in the embodiment of the present application is specifically shown, which can execute the control method of the photovoltaic inverter. The controller 11 includes:

[0045] At least one processor 111 and memory 112 ( Figure 2 A bus connection and a processor are used as an example). A person skilled in the art will understand that Figure 2 The structure shown is only for illustration and does not limit the structure of the controller 11. For example, the controller 11 may also include Figure 2 More or fewer components than shown, or with Figure 2 Different configurations shown.

[0046] The processor 111 is used to provide computing and control capabilities, and to control the controller 11 to execute any method provided in the following application embodiments.

[0047] It is understandable that the processor 111 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0048] The memory 112 is a non-transient computer-readable storage medium that can be used to store non-transient software programs, non-transient computer executable programs and modules, such as program instructions / modules corresponding to the various calculation methods in the embodiments of the present application. The processor 111 can implement the various calculation methods in any of the following method embodiments by running the non-transient software programs, instructions and modules stored in the memory 112. The memory 112 may include a high-speed random access memory and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory 112 may also include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network and a combination thereof.

[0049] An embodiment of the present application also provides a non-volatile computer-readable storage medium, which stores computer-executable instructions. The computer-executable instructions are used by the integrated photovoltaic and storage power supply system to execute the various calculation methods in any of the following method embodiments.

[0050] An embodiment of the present application provides a computer program product, including a computing program stored on a non-volatile computer-readable storage medium, wherein the computer program includes program instructions. When the program instructions are executed by a computer, the computer is caused to perform each computing method in any of the following method embodiments.

[0051] Through the description of the above embodiments, it can be clearly understood by those skilled in the art that each embodiment can be implemented by means of software plus a general hardware platform, and of course can also be implemented by hardware. It can be understood by those skilled in the art that all or part of the processes in the above embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0052] Example 1

[0053] The following describes the control method of the photovoltaic inverter provided by the embodiment of the present application. Figure 4 , Figure 4 1 is a flow chart of a method for controlling a photovoltaic inverter provided in an embodiment of the present application, the method comprising the following steps:

[0054] Step S1: When the energy storage inverter is off-grid, when the terminal power of the AC side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery, the target output frequency of the photovoltaic inverter is calculated.

[0055] When the energy storage inverter is off-grid, the energy storage inverter is disconnected from the grid, and energy flows between the photovoltaic modules, photovoltaic inverter, load, energy storage inverter, and energy storage battery. The electric energy generated by the photovoltaic modules is converted by the photovoltaic inverter and directly supplied to the load. The remaining electric energy is converted into direct current through the AC side load terminal of the energy storage inverter and charges the energy storage battery. Photovoltaic power generation gives priority to meeting the load demand, and the excess energy is stored in the energy storage battery. However, in order to ensure the safety of the energy storage battery, it is necessary to ensure that the power of the electric energy flowing to the energy storage battery is not greater than the maximum allowable charging power of the energy storage battery. That is, when the terminal power of the AC side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery, regulation is required.

[0056] The target output frequency of the photovoltaic inverter should be able to ensure that the power of the electric energy flowing to the energy storage battery is not greater than the maximum allowable charging power of the energy storage battery.

[0057] In some embodiments, the formula for calculating the target output frequency of the photovoltaic inverter is:

[0058]

[0059] Among them, the is the target output frequency, the is the proportional coefficient of the photovoltaic inverter, is the maximum allowable charging power of the energy storage battery, is the load power.

[0060] Among them, the is the maximum allowable charging power of the energy storage battery, and the calculation formula for the maximum allowable charging power of the energy storage battery is:

[0061]

[0062] described is the maximum allowable charging power of the energy storage battery, is the rated voltage of the energy storage battery, is the maximum allowable charging current of the energy storage battery.

[0063] The rated voltage of the energy storage battery is usually referred to the technical specifications provided by the energy storage battery manufacturer.

[0064] To determine the maximum allowable charging current for the energy storage battery, multiple factors must be considered. First, the capacity (Q) of the energy storage battery is an important parameter. The larger the capacity of the energy storage battery, the higher the maximum allowable charging current. However, this does not mean that a larger capacity energy storage battery can withstand a higher charging current, as other factors must also be considered, including the temperature (T) of the energy storage battery, the state of charge (SOC) of the energy storage battery, the aging (SOH) of the energy storage battery, and the consistency of the energy storage battery.

[0065] Specifically, the maximum allowable charging current I of an energy storage battery can be expressed as: I = f(Q, T, SOC, SOH, EQ). This means that the maximum allowable charging current of an energy storage battery is a function related to multiple factors such as the battery capacity, temperature, state of charge, aging, and consistency.

[0066] In practical applications, to determine the maximum allowable charging current of an energy storage battery, the manufacturer's technical specifications or datasheets are usually referenced. These documents provide the maximum allowable charging current value or range for the energy storage battery under different factors.

[0067] In some embodiments, the maximum allowable charging current of the energy storage battery is sent from the energy storage battery to the energy storage inverter via communication to calculate the maximum allowable charging power of the energy storage battery and further calculate the target output frequency of the photovoltaic inverter.

[0068] Among them, the is the load power, which can be monitored and output by the energy storage inverter. The terminal power at the AC load end of the energy storage inverter is equal to the difference between the output power of the photovoltaic inverter and the load power. That is, a portion of the electrical energy output by the photovoltaic inverter is supplied to the load, and the remaining portion is supplied to the energy storage battery through the energy storage inverter. Therefore, after obtaining the maximum allowable charging power of the energy storage battery and the load power, the target output power of the photovoltaic inverter can be obtained: the sum of the maximum allowable charging power of the energy storage battery and the load power.

[0069] Among them, the The calculation formula is:

[0070]

[0071] Among them, the is the maximum operating frequency of the photovoltaic inverter, is the minimum operating frequency of the photovoltaic inverter, is the frequency dead zone of the photovoltaic inverter, is the rated power of the photovoltaic inverter.

[0072] It is worth noting that the The maximum operating frequency of the photovoltaic inverter may be selected from a grid-connected certification standard, such as IEEE 1547, based on the operating parameters of the photovoltaic inverter.

[0073] It is worth noting that the The minimum operating frequency of the photovoltaic inverter may be selected from a grid-connected certification standard, such as IEEE 1547, based on the operating parameters of the photovoltaic inverter.

[0074] described The frequency dead zone of the photovoltaic inverter is the allowable deviation range from the grid frequency, which balances response speed and system stability. The frequency dead zone can be selected based on the operating parameters of the photovoltaic inverter and the grid certification standard, such as IEEE 1547.

[0075] Although the target output frequency of the photovoltaic inverter has been calculated based on the above information, it is actually impossible to directly adjust the photovoltaic inverter based on this target output frequency. The main reasons are: First, according to the design and function of existing photovoltaic inverters, they are constrained by the grid-connected synchronization mechanism. The output frequency of the photovoltaic inverter is forcibly synchronized with the grid frequency through a phase-locked loop (PLL), and human intervention in the frequency output is prohibited. Second, distributed photovoltaic inverters such as microinverters generally lack large-capacity energy storage support, resulting in weak frequency regulation capabilities and insufficient frequency regulation inertia. Actual frequency regulation requires unified coordination by a master control device (such as an energy storage inverter). Third, even if unified coordination is achieved through the energy storage inverter, because the photovoltaic inverter in this embodiment directly powers the load, implementing rapid or large frequency adjustments (such as step frequency modulation) can cause torque fluctuations in motor loads, induce mechanical stress, trigger malfunction of load protection devices, and cause unplanned downtime.

[0076] Therefore, in this embodiment, a progressive frequency regulation strategy is adopted to control the frequency of the energy storage inverter, and the photovoltaic inverter tracks the frequency of the energy storage inverter through a phase-locked loop, thereby achieving progressive regulation of the frequency of the photovoltaic inverter.

[0077] Step S2: Acquire the current frequency of the photovoltaic inverter and the first frequency before the last frequency regulation, wherein the current frequency is the frequency of the photovoltaic inverter after the last frequency regulation.

[0078] The current frequency is actually the frequency of the photovoltaic inverter after the last frequency adjustment. If the current frequency of the photovoltaic inverter is obtained for the first time, the target output frequency is taken as the current frequency of the photovoltaic inverter.

[0079] It is understood that the first frequency of the photovoltaic inverter before the last frequency adjustment is actually the current frequency of the photovoltaic inverter before the last frequency adjustment. In fact, the first frequency before the last frequency adjustment is also the frequency after the previous (and previous) frequency adjustment. If the current frequency adjustment is the first time, the rated frequency of the photovoltaic inverter is used as the first frequency.

[0080] Step S3: Calculate the frequency increment for each fine-tuning of the photovoltaic inverter according to the target output frequency, the current frequency, and the first frequency.

[0081] In some embodiments, the frequency increment is calculated as follows:

[0082]

[0083] Among them, the is the frequency increment, the is the first experience value, is the second experience value, is the difference between the target output frequency and the current frequency, is the difference between the current frequency and the first frequency.

[0084] In some embodiments, the first empirical value is 0.01, and the second empirical value is 0.002.

[0085] Step S4: calculating a single controlled frequency for fine-tuning the photovoltaic inverter according to the frequency increment and the current frequency.

[0086] The single controlled frequency is the sum of the current frequency and the frequency increment.

[0087]

[0088] in, is a single controlled frequency, is the current frequency, is the frequency increment.

[0089] Step S5: Control the energy storage inverter according to the single controlled frequency to achieve control of the photovoltaic inverter.

[0090] As mentioned above, the frequency control of the photovoltaic inverter requires the use of a progressive frequency regulation strategy to control the frequency of the energy storage inverter.

[0091] In some embodiments, see Figure 5, the step of controlling the energy storage inverter according to the single controlled frequency includes:

[0092] Step S501 : calculating the single controlled power of the energy storage inverter for single regulation according to the single controlled frequency.

[0093] Frequency control of the energy storage inverter can be achieved through power regulation.

[0094] In some embodiments, the calculation formula of the single controlled power is:

[0095]

[0096] Among them, the is the single controlled power, the is the last controlled power of the energy storage inverter, is the single controlled frequency, the single controlled frequency is the sum of the current frequency and the frequency increment, is the rated frequency of the energy storage inverter, is the frequency dead zone of the energy storage inverter, is the proportional coefficient of the energy storage inverter.

[0097] described The rated frequency of the energy storage inverter is shown in FIG. 1 . The rated power can be referred to the technical specification provided by the manufacturer of the energy storage inverter.

[0098] Among them, the The calculation formula is:

[0099]

[0100] Among them, the is the maximum operating frequency of the energy storage inverter, is the minimum operating frequency of the energy storage inverter, is the frequency dead zone of the energy storage inverter, is the rated power of the energy storage inverter.

[0101] Energy storage inverter 、 、 、 The acquisition method can be selected according to the usage parameters of the energy storage inverter and the grid-connected certification standard, such as IEEE 1547.

[0102] Step S502 : Control the energy storage inverter according to the single controlled power to achieve control of the photovoltaic inverter.

[0103] Step S6, repeating steps S1-S5 until the current frequency of the photovoltaic inverter reaches the target output frequency.

[0104] It is worth noting that, in some embodiments, see Figure 6 When the energy storage inverter is off-grid, before step S1, the method further includes:

[0105] Step A1: Get the current output power of the photovoltaic inverter P PV , load power of the load , Maximum allowable charging power of energy storage battery .

[0106] Current output power of the PV inverter P PV It can be detected by the photovoltaic inverter. Load power , Maximum allowable charging power of energy storage battery The method of obtaining can refer to the above content and will not be repeated here.

[0107] Step A2: Determine the current output power of the photovoltaic inverter Is it greater than the load power? If not, go to step A3; if so, go to step A4.

[0108] By judgment and size to trigger the hybrid power supply mode or enter the energy distribution stage.

[0109] Step A3: Control the photovoltaic inverter and the energy storage inverter to collaboratively supply power to the load.

[0110] when Less than When the load is disconnected, the hybrid power supply mode is triggered to control the photovoltaic inverter and energy storage inverter to collaboratively supply power to the load to avoid power outage.

[0111] Step A4: Calculate the difference between the current output power of the photovoltaic inverter and the load power to obtain the terminal power of the AC side load terminal of the energy storage inverter.

[0112] when Greater than When the system is in the energy distribution stage, part of the energy generated by the photovoltaic panels is used to power the load, and part of the energy is used to charge the energy storage battery through the energy storage inverter.

[0113] The part used to charge the energy storage battery can be called the photovoltaic surplus power, that is, the terminal power of the AC side load end of the energy storage inverter. The terminal power is - .

[0114] Step A5, determining whether the terminal power is greater than the maximum allowable charging power of the energy storage battery, if so, proceeding to step S1; if not, proceeding to step A6.

[0115] When the terminal power at the AC-side load end of the energy storage inverter exceeds the maximum allowable charging power of the energy storage battery, to ensure the safety of the energy storage battery, it is necessary to ensure that the power of the electric energy flowing to the energy storage battery does not exceed the maximum allowable charging power of the energy storage battery. In other words, when the terminal power at the AC-side load end of the energy storage inverter exceeds the maximum allowable charging power of the energy storage battery, regulation is required, and the process proceeds to step S1 for regulation. The specific regulation method can be found in the above content and will not be repeated here.

[0116] It can be understood that when the controlled frequency of the photovoltaic inverter reaches the target output frequency, the terminal power of the AC side load end of the energy storage inverter is equal to the maximum allowable charging power of the energy storage battery, so that the photovoltaic inverter can not only supply power to the load, but also the excess electric energy can be safely and efficiently supplied to the energy storage battery through the energy storage inverter, and the energy utilization rate of the system is high.

[0117] Step A6: Control the photovoltaic inverter to directly charge the energy storage battery through the energy storage inverter.

[0118] When the terminal power of the AC side load terminal of the energy storage inverter is not greater than the maximum allowable charging power of the energy storage battery, the photovoltaic inverter can be directly controlled to store the surplus electric energy directly into the energy storage battery through the energy storage inverter.

[0119] Through the above method, since the photovoltaic inverter is connected to the load and the AC side load end of the energy storage inverter, when the energy storage inverter is off-grid, the electricity generated by the photovoltaic module can be supplied to the load through the photovoltaic inverter, and the surplus photovoltaic power can also be used to charge the energy storage battery through the energy storage inverter, thereby greatly improving the overall energy utilization rate of the system.

[0120] In addition, when the energy storage inverter is off-grid, the photovoltaic inverter is controlled and the output frequency of the photovoltaic inverter is adjusted to obtain a controlled frequency. The photovoltaic inverter is then controlled according to the controlled frequency to ensure the safety of the energy storage battery operation.

[0121] Example 2

[0122] Hereinafter, another control method of a photovoltaic inverter provided by the embodiment of the present application will be discussed. Figure 7 , Figure 7 FIG1 is a flow chart of another photovoltaic inverter control method provided in an embodiment of the present application. The method includes:

[0123] Step S100: When the energy storage inverter is connected to the grid, the photovoltaic inverter is controlled to supply power to the load.

[0124] When the energy storage inverter is connected to the grid, the electric energy generated by the photovoltaic module is first supplied to the load through the photovoltaic inverter. If there is any surplus, it is supplied to the grid through the energy storage inverter.

[0125] Step S200: obtaining the current output power of the photovoltaic inverter and the load power of the load.

[0126] The method for obtaining the current output power of the photovoltaic inverter and the load power can refer to the above-mentioned embodiment 1, which will not be repeated here.

[0127] Step S300 , determining whether the current output power of the photovoltaic inverter is greater than the load power of the load, if not, executing step S400 , and if so, executing step S500 .

[0128] Step S400: Control the photovoltaic inverter and the energy storage inverter or the power grid to collaboratively supply power to the load.

[0129] If the current output power of the photovoltaic inverter is less than the load power, it means that there is a shortage of electric energy generated by the photovoltaic module when supplying the load through the photovoltaic inverter. The shortage is supplemented by the power grid or energy storage battery through the energy storage inverter.

[0130] Step S500: Obtain the difference between the current output power of the photovoltaic inverter and the load power to obtain the terminal power of the AC side load terminal of the energy storage inverter.

[0131] If the current output power of the photovoltaic inverter is greater than the load power, it means that there is still surplus electricity generated by the photovoltaic module after supplying the load through the photovoltaic inverter. In this case, the electricity generated by the photovoltaic module can also be fed to the grid through the photovoltaic inverter and the energy storage inverter.

[0132] The difference between the current output power of the photovoltaic inverter and the load power is used to obtain the terminal power at the AC side load end of the energy storage inverter, which is the surplus power. This surplus power can be fed to the grid.

[0133] Step S600: Control the photovoltaic inverter to feed power to the power grid with the terminal power through the energy storage inverter.

[0134] Through the above method, when the energy storage inverter is connected to the grid, the electric energy generated by the photovoltaic module can be supplied to the load through the photovoltaic inverter. When the electric energy generated by the photovoltaic module is in surplus after being supplied to the load through the photovoltaic inverter, it can also be fed to the grid through the energy storage inverter. When the electric energy generated by the photovoltaic module is in short supply to the load, it can be supplemented by the grid or the energy storage battery through the energy storage inverter. This can ensure the normal operation of the load on the one hand, and the electric energy generated by the photovoltaic module can also be utilized, and the energy utilization rate of the integrated photovoltaic power supply system is high.

[0135] Example 3

[0136] The following describes the control device for the photovoltaic inverter provided by the embodiment of the present application. Figure 8 , Figure 8 : is a schematic diagram of a photovoltaic inverter control device provided in an embodiment of the present application. The photovoltaic inverter control device 1 includes a first calculation module 11, which is used to calculate the target output frequency of the photovoltaic inverter when the energy storage inverter is off-grid and the terminal power of the AC side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery; an acquisition module 12, which is used to obtain the current frequency of the photovoltaic inverter and the first frequency before the last frequency regulation, where the current frequency is the frequency of the photovoltaic inverter after the last frequency regulation; a second calculation module 13, which is used to calculate the frequency increment for each fine-tuning of the photovoltaic inverter based on the target output frequency, the current frequency, and the first frequency; a third calculation module 14, which is used to calculate a single controlled frequency for fine-tuning the photovoltaic inverter based on the frequency increment and the current frequency; and a control module 15, which is used to control the energy storage inverter according to the single controlled frequency to achieve control of the photovoltaic inverter, and control the execution of the acquisition module, the second calculation module, and the third calculation module until the current frequency of the photovoltaic inverter reaches the target output frequency.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the idea of ​​the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present application as above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A control method for a photovoltaic inverter, characterized in that: Applicable to a photovoltaic-storage integrated power supply system, the photovoltaic-storage integrated power supply system includes an energy storage battery, an energy storage inverter, a photovoltaic inverter, a photovoltaic module and a load; the DC side of the energy storage inverter is connected to the energy storage battery, its AC side grid terminal is connected to the grid, and its AC side load terminal is connected to the load; the DC side of the photovoltaic inverter is connected to the photovoltaic module, and its AC side is connected to the load and the AC side load terminal of the energy storage inverter; The method comprises the following steps: S1. When the energy storage inverter is off-grid, when the terminal power of the AC-side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery, calculate the target output frequency of the photovoltaic inverter; the target output frequency of the photovoltaic inverter satisfies that the power of the electric energy flowing to the energy storage battery is not greater than the maximum allowable charging power of the energy storage battery; S2. Obtaining the current frequency of the photovoltaic inverter and the first frequency before the last frequency regulation, wherein the current frequency is the frequency of the photovoltaic inverter after the last frequency regulation; S3. Calculate the frequency increment for each fine-tuning of the photovoltaic inverter according to the target output frequency, the current frequency, and the first frequency; S4. Calculating a single controlled frequency for fine-tuning the photovoltaic inverter based on the frequency increment and the current frequency; S5. Controlling the energy storage inverter according to the single controlled frequency to achieve control of the photovoltaic inverter; S6. Repeat steps S2-S5 until the current frequency of the photovoltaic inverter reaches the target output frequency.

2. The method according to claim 1, characterized in that The formula for calculating the target output frequency of the photovoltaic inverter in step S1 is: Among them, the is the target output frequency, the is the proportional coefficient of the photovoltaic inverter, is the maximum allowable charging power of the energy storage battery, is the load power; described The calculation formula is: Among them, the is the maximum operating frequency of the photovoltaic inverter, is the minimum operating frequency of the photovoltaic inverter, is the frequency dead zone of the photovoltaic inverter, is the rated power of the photovoltaic inverter.

3. The method according to claim 2, characterized in that The formula for the frequency increment in step S3 is: Among them, the is the frequency increment, the is the first experience value, is the second experience value, is the difference between the target output frequency and the current frequency, is the difference between the current frequency and the first frequency.

4. The method according to claim 3, characterized in that The first experience value is 0.01, and the second experience value is 0.

002.

5. The method according to claim 4, characterized in that The step S5 comprises: Calculating a single controlled power of the energy storage inverter for single regulation according to the single controlled frequency; The energy storage inverter is controlled according to the single controlled power to achieve control of the photovoltaic inverter.

6. The method according to claim 5, characterized in that The formula for calculating the single controlled power of the energy storage inverter for single regulation of power according to the single controlled frequency is: Among them, the is the single controlled power, the is the last controlled power of the energy storage inverter, is the single controlled frequency, the single controlled frequency is the sum of the current frequency and the frequency increment, is the rated frequency of the energy storage inverter, is the frequency dead zone of the energy storage inverter, is the proportional coefficient of the energy storage inverter.

7. The method according to claim 6, characterized in that Before step S1, the method further includes: Obtaining the current output power of the photovoltaic inverter, the load power of the load, and the maximum allowable charging power of the energy storage battery; Determining whether the current output power of the photovoltaic inverter is greater than the load power; If not, controlling the photovoltaic inverter and the energy storage inverter to collaboratively supply power to the load; If so, the difference between the current output power of the photovoltaic inverter and the load power is calculated to obtain the terminal power of the AC side load terminal of the energy storage inverter; Determining whether the terminal power is greater than the maximum allowable charging power of the energy storage battery; If yes, execute step S1; If not, the photovoltaic inverter is controlled to directly charge the energy storage battery through the energy storage inverter.

8. The method according to any one of claims 1 to 7, characterized in that The method further comprises: When the energy storage inverter is connected to the grid, controlling the photovoltaic inverter to supply power to the load; Obtaining the current output power of the photovoltaic inverter and the load power of the load; Determining whether the current output power of the photovoltaic inverter is greater than the load power; If not, controlling the photovoltaic inverter and the energy storage inverter or the power grid to collaboratively supply power to the load; If so, the difference between the current output power of the photovoltaic inverter and the load power is obtained to obtain the terminal power of the AC side load terminal of the energy storage inverter; The photovoltaic inverter is controlled to feed power to the power grid with the terminal power through the energy storage inverter.

9. A photovoltaic inverter control device, characterized in that: Applicable to a photovoltaic-storage integrated power supply system, the photovoltaic-storage integrated power supply system includes an energy storage battery, an energy storage inverter, a photovoltaic inverter, a photovoltaic module and a load; the DC side of the energy storage inverter is connected to the energy storage battery, its AC side grid terminal is connected to the grid, and its AC side load terminal is connected to the load; the DC side of the photovoltaic inverter is connected to the photovoltaic module, and its AC side is connected to the load and the AC side load terminal of the energy storage inverter; The control device comprises: a first calculation module, configured to calculate a target output frequency of the photovoltaic inverter when the energy storage inverter is off-grid and when the terminal power of the AC-side load terminal of the energy storage inverter is greater than the maximum allowable charging power of the energy storage battery; the target output frequency of the photovoltaic inverter satisfies that the power of the electric energy flowing to the energy storage battery is not greater than the maximum allowable charging power of the energy storage battery; an acquisition module, configured to acquire the current frequency of the photovoltaic inverter and a first frequency before the last frequency regulation, wherein the current frequency is the frequency of the photovoltaic inverter after the last frequency regulation; a second calculation module, configured to calculate a frequency increment for each fine-tuning of the photovoltaic inverter according to the target output frequency, the current frequency, and the first frequency; a third calculation module, configured to calculate a single controlled frequency for fine-tuning the photovoltaic inverter according to the frequency increment and the current frequency; a control module configured to control the energy storage inverter according to the single controlled frequency to achieve control of the photovoltaic inverter, and to control the acquisition module, the second calculation module, and the third calculation module to execute until the current frequency of the photovoltaic inverter reaches the target output frequency.

10. A photovoltaic and storage integrated power supply system, characterized in that: include: at least one processor; as well as A memory, the memory being communicatively connected to the at least one processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the at least one processor so that the at least one processor can execute the method according to any one of claims 1 to 8.

11. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor performs the steps of the method according to any one of claims 1 to 8.

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