Photovoltaic unit control method and device based on hybrid control of network construction type and network following type

Abstract

The application provides a photovoltaic unit control method and device based on network construction type and network following type hybrid control, equipment and medium, and belongs to the technical field of power system control. The control method comprises the following steps: adding a network construction type control method based on direct current voltage synchronization in the grid-connected converter control logic of the photovoltaic unit; obtaining real-time short-circuit ratio, high short-circuit ratio threshold value and low short-circuit ratio threshold value according to real-time operation data of the photovoltaic unit; when the real-time short-circuit ratio is higher than the high short-circuit ratio threshold value, switching the voltage source type control to the current source type control; when the real-time short-circuit ratio is lower than the low short-circuit ratio threshold value, pre-synchronizing the current source type control and the voltage source type control, and after pre-synchronization, switching the current source type control to the voltage source type control; and after completing the control switching, re-synchronizing the current source type control and the voltage source type control. The control strategy can realize disturbance-free switching of the photovoltaic unit, and can also improve the ability of the photovoltaic unit to cope with strong and weak network changes.

Description

Technical Field

[0001] This invention belongs to the field of power system control technology, specifically relating to a photovoltaic unit control method, control device, electronic equipment, and computer-readable storage medium based on a hybrid control of grid-connected and grid-following types. Background Technology

[0002] Building a new power system with new energy sources as the mainstay necessitates addressing the power system's safety and stability issues caused by the uncertainty and random fluctuations of new energy sources, such as wind and solar power. Maintaining the stable operation of wind and solar power systems under conditions of random fluctuations in wind and solar resources, variations in grid connection strength, and various disturbances, and further exploring their flexibility, is a core bottleneck restricting new energy from becoming the primary power source. Existing wind and solar power units are mostly designed for connection to strong grids; while mature, their topologies are simplistic and their control modes rigid, making them ill-suited to scenarios with large-scale changes in resources and grid strength.

[0003] Current research on photovoltaics mainly focuses on the design of grid-connected converters, i.e., current-source control models. Stable control of photovoltaic units is achieved by improving the current-source control mode. The grid-connected (voltage-source) control proposed by the University of Wisconsin is more adaptable to weak grids, but its stability margin decreases when connected to strong grids with lower real-time equivalent impedances. Furthermore, it suffers from lower grid-connected power quality and difficulty in maximum power point tracking, resulting in poor economic efficiency. The introduction of voltage-source control provides a new solution for renewable energy integration systems. Voltage-source control technology, by improving the control system of renewable energy generation equipment, can give renewable energy generation equipment similar frequency and voltage regulation characteristics to conventional synchronous generators, thus solving the problem of insufficient grid support capacity after a high proportion of renewable energy integration. However, the current voltage-source control uses a virtual synchronous machine control method, which requires sacrificing DC voltage control capability in the grid-side converter within the photovoltaic unit structure. Traditional photovoltaic unit voltage source control is based on a virtual synchronous active power outer loop to achieve voltage-source grid-connected control; however, the grid-side control of photovoltaic units typically uses DC voltage control to maintain DC line voltage stability. However, the traditional virtual synchronous active outer loop synchronization method requires the addition of grid-side control, which will conflict with the control objective of grid-side DC voltage control. Therefore, it is necessary to introduce DC voltage synchronization control to grid-side DC voltage control.

[0004] The current reliance on a single control mode makes it difficult for wind and solar power systems to operate stably under conditions of drastic grid strength fluctuations caused by real-time power penetration rate volatility. Therefore, researching flexible control strategies for wind and solar power units to achieve stable operation and improved flexibility under complex power source-grid conditions remains a challenging problem to be solved.

[0005] In summary, the adaptability of photovoltaic (PV) units to both strong and weak grid stability is of universal and critical significance for the reliable operation and absorption of large-scale renewable energy integration. There is an urgent need to further explore the voltage source support capabilities of PV units and fully integrate them with their current source support capabilities to achieve voltage and current source control mode switching based on real-time changes in the grid short-circuit ratio. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a photovoltaic unit control method, device, equipment, and medium based on a hybrid control of grid-connected and grid-connected technologies. This allows the photovoltaic unit to fully utilize its voltage and current source control capabilities while maintaining DC voltage stability. Consequently, when large-scale renewable energy access causes changes in the voltage short-circuit ratio, the grid-side converter of the photovoltaic unit can be switched freely and without disturbance, improving the grid-connected stability and adaptability of the photovoltaic unit.

[0007] The technical solution adopted in this invention is: A photovoltaic unit control method based on a hybrid control of grid-connected and grid-following control, comprising: A grid-connected control method based on DC voltage synchronization is added to the grid-connected converter control logic of the photovoltaic unit; The real-time short-circuit ratio, high short-circuit ratio threshold, and low short-circuit ratio threshold are obtained based on the real-time operating data of the photovoltaic unit. When the real-time short-circuit ratio is higher than the high short-circuit ratio threshold, the voltage source control is switched to the current source control; when the real-time short-circuit ratio is lower than the low short-circuit ratio threshold, the current source control and voltage source control are pre-synchronized, and after pre-synchronization, the current source control is switched to the voltage source control. After the control switch is completed, the current source control and voltage source control are resynchronized to prepare for the next control switch.

[0008] Furthermore, incorporating a grid-connected control method based on DC voltage synchronization into the grid-connected converter control logic of the photovoltaic unit includes: DC voltage synchronization control is introduced into the grid-side DC voltage control of photovoltaic units. The process of DC voltage synchronization control is calculated as follows: , Where θ represents the synchronization angle of the DC voltage synchronization control output. Indicates the modulation voltage. The reference value representing the AC bus voltage. This indicates the DC voltage value of the photovoltaic unit. This indicates the rated DC voltage of the photovoltaic unit. The reference value representing the modulation voltage. This represents the reference value for the reactive power of the photovoltaic unit. This represents the control gain of the reactive power loop. Indicates the system's rated capacity. Represents the reference value of angular frequency. Indicates the initial angular frequency. and These represent the proportional and integral coefficients of the DC voltage synchronous controller, respectively. This indicates the reference value of the DC voltage of the photovoltaic unit. This represents the reactive power value of the photovoltaic unit; In the outer-loop DC voltage control, a DC voltage feedforward is introduced, and the control process of the outer and inner loops is calculated as follows: , , ;in, This represents the reference value for the d-axis current of the photovoltaic unit. This represents the d-axis modulation ratio of the grid-side converter. This indicates the q-axis modulation ratio of the grid-side converter. The feedback coefficient represents the DC voltage. This represents a reference value for the d-axis voltage of the photovoltaic unit. This represents the d-axis voltage value of the photovoltaic unit. and These are the proportional coefficient and integral coefficient of the outer voltage loop, respectively. and These are the proportional coefficient and integral coefficient of the inner current loop, respectively. This indicates the DC voltage value of the photovoltaic unit. and These represent the actual feedback values ​​of the d-axis and q-axis currents of the photovoltaic unit, respectively. This represents the reference value for the q-axis current of the photovoltaic unit.

[0009] Furthermore, the low short-circuit ratio threshold is expressed as: Where U represents the voltage output by the converter to the power grid, and E represents the electromotive force inside the system.

[0010] Furthermore, the high short-circuit ratio threshold is expressed as: ,in P represents the impedance of the power grid, and P and U represent the active power and voltage output by the converter to the power grid, respectively.

[0011] Furthermore, both the pre-synchronization and re-synchronization methods are expressed as follows: , , ;in This indicates the angular frequency reference of the synchronous control output. This represents the internal potential reference of the synchronous control output. This represents the inner loop reference value of the synchronous control output current. Indicates the initial angular frequency. This indicates the output phase angle based on DC voltage synchronization. This indicates the phase angle of the phase-locked loop output. Indicates the reference value for the inner current loop in the network configuration; This indicates the reference value for the inner loop of the current grid; Δi represents the compensation amount of the current loop. The compensation coefficient representing the current. The initial electromotive force of the system is given by U, and the voltage value at the AC terminal of the inverter is given by U. Represents the angular frequency compensation coefficient. This represents the internal potential compensation coefficient.

[0012] Furthermore, the output phase angle based on DC voltage synchronization is expressed as: ,in This is the reference value for angular frequency. Indicates the initial value of angular frequency. and These are the proportional and integral coefficients of the DC voltage synchronous controller. This indicates the DC voltage value of the photovoltaic unit. This indicates the rated DC voltage of the photovoltaic unit. This indicates the reference value for the DC voltage of the photovoltaic unit.

[0013] Furthermore, the phase angle of the phase-locked loop output is expressed as: , , ,in This is the output angular frequency of the phase-locked loop. Indicates the rated angular frequency. and Phase-locked loop controllers The proportional coefficient and integral coefficient.

[0014] A photovoltaic unit control device based on hybrid grid-connected and grid-linked control includes a data acquisition module, a calculation module, a detection module, and a control module. The data acquisition module is used to acquire real-time operating data of the photovoltaic unit. The calculation module is used to calculate the real-time grid-connected short-circuit ratio, high short-circuit ratio threshold, and low short-circuit ratio threshold of the photovoltaic unit based on the operating data acquired by the data acquisition module. The detection module is used to determine whether to issue a switching signal based on the grid-connected short-circuit ratio obtained by the calculation module, and the high short-circuit ratio threshold and the low short-circuit ratio threshold. The control module is used to switch between current source control and voltage source control based on the switching signal issued by the detection module.

[0015] An electronic device includes a processor and a memory; the memory is used to store executable instructions, and the processor is used to execute the instructions to implement the control method.

[0016] A computer-readable storage medium storing instructions that, when executed, implement the control method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention, through hysteresis switching control and post-switching resynchronization process control, not only achieves autonomous switching of photovoltaic (PV) units between grid-connected and grid-connected configurations after changes in the short-circuit ratio at the grid connection point, but also realizes resynchronization after switching, facilitating subsequent grid-connected / grid-connected configuration switching processes. This not only fully leverages the voltage source control capabilities of PV units to achieve disturbance-free switching, but also enhances their ability to cope with changes in grid strength, further promoting the development and utilization of large-scale renewable energy.

[0018] This invention introduces a DC voltage synchronization-based control method into the control of photovoltaic (PV) units, enabling the equivalent voltage source of the PV unit to be synchronized. In addition to the traditional current source control, it adds voltage source control capability to the PV unit. During the switching process, margin range control is considered to determine whether the PV unit is within the margin range. After real-time short-circuit ratio detection and margin range discrimination of the PV unit, the voltage source control is directly switched to current source control, or the current source control is switched to voltage source control after pre-synchronization. After the switch, phase-locked loop (PLL) is used to re-synchronize the PLL, again achieving pre-synchronization of power angle, voltage, and current between current source and voltage source control. The control strategy of this invention considers the allocation of grid-side and generator-side control objectives for the PV unit, the control characteristics of grid-connected and grid-connected control, and the organic unity of grid-connected and grid-connected control. By combining grid-connected control, grid-connected control, real-time short-circuit ratio, and outer-loop pre-synchronization control, it fully integrates the advantages of both grid-connected and grid-connected control while realizing grid-connected control of the PV unit from a new perspective of DC voltage synchronization.

[0019] The control strategy of this invention can not only fully utilize the voltage source control capability of photovoltaic units and achieve disturbance-free switching of photovoltaic units, but also enhance the ability of photovoltaic units to cope with changes in strong and weak grids, further promoting the development and utilization of large-scale renewable energy. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings.

[0021] Figure 1 : Flowchart of Embodiment 1 of the present invention; Figure 2: A schematic diagram of the structure and control of Embodiment 1 of the present invention; Figure 3 The following is a simulation experiment of the photovoltaic unit after grid connection switching in Embodiment 1 of the present invention, showing the three-phase voltage and dq voltage curves of the photovoltaic grid connection. Figure 4 The following is a simulation experiment of the photovoltaic unit after grid connection switching in Embodiment 1 of the present invention, showing the three-phase voltage and three-phase current curves of the photovoltaic grid connection. Figure 5 : A schematic diagram of Embodiment 2 of the present invention; Figure 6 : A schematic diagram of Embodiment 3 of the present invention. Detailed Implementation

[0022] To better understand the present invention, the content of the invention is further clearly illustrated below with reference to embodiments and accompanying drawings. However, the scope of protection of the present invention is not limited to the embodiments described below. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0023] Example 1: See Figures 1-2 The purpose of this embodiment is to provide a photovoltaic unit control method based on a hybrid control of grid-connected and grid-following types, including: S1. Add a grid-type control method based on DC voltage synchronization to the grid-connected converter control logic of the photovoltaic unit to add equivalent voltage source control capability to the grid-side control of the converter.

[0024] By introducing a grid-type control method based on DC voltage synchronization into the grid-connected converter control of photovoltaic units, the equivalent voltage source of the grid-side converter of the photovoltaic unit is realized to be the synchronization process. In addition to the traditional grid-following control (current source control) of the grid-side converter of the photovoltaic unit, grid-type control (equivalent voltage source control) capability is additionally given.

[0025] Specifically, traditional photovoltaic (PV) unit control is based on a virtual synchronous active power outer loop to achieve voltage source-type grid control. Grid-side control of PV units typically uses DC voltage control to maintain DC line voltage stability. However, the synchronization method of the traditional virtual synchronous active power outer loop needs to be added to the grid-side control, which conflicts with the control objective of grid-side DC voltage control. Therefore, DC voltage synchronization control needs to be introduced into the grid-side DC voltage control. The DC voltage synchronization control process is calculated as follows:

[0026]

[0027] Where θ represents the synchronization angle of the DC voltage synchronization control output. Indicates the modulation voltage. The reference value representing the AC bus voltage. This indicates the DC voltage value of the photovoltaic unit. This indicates the rated DC voltage of the photovoltaic unit. The reference value representing the modulation voltage. This represents the reference value for the reactive power of the photovoltaic unit. This represents the control gain of the reactive power loop. Indicates the system's rated capacity. Represents the reference value of angular frequency. Indicates the initial value of angular frequency. and These represent the proportional and integral coefficients of the DC voltage synchronous controller, respectively. This indicates the reference value of the DC voltage of the photovoltaic unit. This represents the reactive power value of the photovoltaic unit.

[0028] After introducing DC voltage synchronization control, to ensure the stability of the DC voltage of the photovoltaic unit, a DC voltage feedforward quantity needs to be introduced into the outer loop DC voltage control, based on ensuring DC voltage synchronization, to correctly respond to changes in DC voltage and ensure DC voltage stability. The control process of the outer and inner loops is calculated as follows:

[0029]

[0030]

[0031] in, This represents a reference value for the d-axis current of the photovoltaic unit (the value is usually 0). This represents the d-axis modulation ratio of the grid-side converter. This indicates the q-axis modulation ratio of the grid-side converter. The feedback coefficient represents the DC voltage. This represents a reference value for the d-axis voltage of the photovoltaic unit. This represents the d-axis voltage value of the photovoltaic unit. and These are the proportional coefficient and integral coefficient of the outer voltage loop, respectively. and These are the proportional coefficient and integral coefficient of the inner current loop, respectively. This indicates the DC voltage value of the photovoltaic unit. and These represent the actual feedback values ​​of the d-axis and q-axis currents of the photovoltaic unit, respectively. This represents the reference value for the q-axis current of the photovoltaic unit.

[0032] Subsequently, after introducing the voltage source control method for the DC voltage of the photovoltaic unit, the photovoltaic unit has grid-connected current source control and grid-connected voltage source control, and can calculate the corresponding voltage source type and current source type synchronization process.

[0033] Specifically, the photovoltaic unit is calculated based on the reference values ​​of the grid-type phase angle and the following-type phase angle during DC voltage synchronization:

[0034]

[0035]

[0036]

[0037] in, The output phase angle is based on DC voltage synchronization. This is the reference value for angular frequency. , These are the proportional and integral coefficients of the DC voltage synchronous controller. , The phase angle and angular frequency are output by the phase-locked loop (PLL). The subscript GFL represents the control system variables based on the PLL, distinguishing them from the actual system system variables. and Phase-locked loop controllers proportionality coefficient and integral coefficient, This represents the q-axis output voltage feedback value of the converter. Indicates the initial value of angular frequency. This indicates the rated angular frequency.

[0038] S2. Obtain the real-time short-circuit ratio, high short-circuit ratio threshold, and low short-circuit ratio threshold based on the real-time operating data of the photovoltaic unit.

[0039] Based on S1 control, margin range control is considered during the switching process. The margin range is defined by the high short-circuit ratio threshold and the low short-circuit ratio threshold.

[0040] To avoid repeated switching at the boundaries, hysteresis switching control needs to be set up to ensure that the high and low thresholds for switching within the margin range are calculated as follows:

[0041]

[0042] in, The short-circuit ratio relationship represents the voltage source type, which determines the high short-circuit ratio threshold for margin switching, i.e. the high short-circuit ratio threshold for switching to the current source type. The short-circuit ratio relationship represents the current source type, which determines the low short-circuit ratio threshold for margin switching, i.e. the low short-circuit ratio threshold for switching to the voltage source type. The impedance of the power grid is represented by P and U, which represent the active power and voltage output by the converter to the power grid, respectively, and E represents the electromotive force inside the system.

[0043] S3. When the real-time short-circuit ratio is higher than the high short-circuit ratio threshold, a first switching signal is issued; when the real-time short-circuit ratio is lower than the low short-circuit ratio threshold, a second switching signal is issued.

[0044] To determine whether the photovoltaic unit is within the margin range, when the real-time short-circuit ratio of the photovoltaic unit connected to the grid is higher than the high short-circuit ratio threshold, a first switching signal is issued, planning to switch from voltage source control to current source control (grid-connected type to grid-following type); when the real-time short-circuit ratio of the photovoltaic unit connected to the grid is lower than the low short-circuit ratio threshold, a second switching signal is issued, planning to switch from current source control to voltage source control (grid-following type to grid-connected type).

[0045] S4. In response to the first switching signal, switch the voltage source control to the current source control; after responding to the second switching signal, perform pre-synchronization between the current source control and the voltage source control, and after pre-synchronization, switch the current source control to the voltage source control.

[0046] For the second switching signal, the power angle, voltage, and current of the current source control and voltage source control are pre-synchronized during the pre-synchronization control stage.

[0047] To ensure that the photovoltaic unit has both current-source and voltage-source control capabilities and can switch flexibly, it is necessary to ensure that the photovoltaic unit achieves pre-synchronization of power angle, voltage, and current before switching between the two modes. The specific pre-synchronization process is calculated as follows:

[0048]

[0049]

[0050] in This indicates the angular frequency reference of the synchronous control output. This represents the internal potential reference of the synchronous control output. This represents the inner loop reference value of the synchronous control output current. Indicates the initial angular frequency. This indicates the output phase angle based on DC voltage synchronization. This indicates the phase angle of the phase-locked loop output. Indicates the reference value for the inner current loop in the network configuration; This indicates the reference value for the inner loop of the current grid; Δi represents the compensation amount of the current loop. The compensation coefficient representing the current. This represents the compensation amount for DC synchronous loop control. This represents the amount of compensation for the internal potential. The initial electromotive force of the system is given by U, and the voltage value at the AC terminal of the inverter is given by U. Represents the angular frequency compensation coefficient. This represents the internal potential compensation coefficient.

[0051] S5. After completing the control switch, resynchronize the current source control and voltage source control to prepare for the next control switch.

[0052] After the first switch from grid-based to network-based configuration, a dual-mode resynchronization process is required to prepare for the second switch. The calculation method for the resynchronization process is the same as the pre-synchronization method in S4. Specifically, after switching from voltage source control to current source control, a phase-locked loop (PLL) is used for resynchronization.

[0053] By employing hysteresis switching control and post-switching resynchronization process control, this system not only enables autonomous switching of photovoltaic (PV) units between grid-following control (current source control) and grid-connected control (voltage source control) after changes in the short-circuit ratio at the grid connection point, but also achieves resynchronization after switching, facilitating subsequent grid-following / grid-connected switching processes. This not only fully leverages the voltage source control capabilities of PV units, achieving disturbance-free switching, but also enhances their ability to cope with changes in grid strength, further promoting the development and utilization of large-scale renewable energy.

[0054] This embodiment simulates the photovoltaic unit and grid type / grid configuration control switching process under different grid connection scenarios. The simulation results are as follows: Figures 3-4 The above, wherein Figure 3 When the short-circuit ratio is 5, the control method of this invention is used to display the photovoltaic grid-connected three-phase voltage and dq voltage curves after the photovoltaic unit and grid switching. Figure 4 The graph shows the three-phase current and three-phase voltage curves of the photovoltaic grid-connected system after grid switching, corresponding to the control method of this invention under weak grid conditions with a short-circuit ratio of 1.7. Figures 3-4 It is evident that by employing this invention, the voltage source control capability of photovoltaic units can be fully utilized, enabling seamless switching of photovoltaic units. Furthermore, it can enhance the photovoltaic units' ability to cope with changes in strong and weak grids, thereby further promoting the development and utilization of large-scale renewable energy.

[0055] Example 2: The purpose of this example is to provide a photovoltaic unit control device based on a hybrid control of grid-connected and grid-fed types, for executing the control method as described in Example 1. Figure 5As shown, the control device 200 includes an acquisition module 201, a calculation module 202, a detection module 203, and a control module 204.

[0056] The acquisition module 201 is used to acquire real-time operating data of the photovoltaic unit.

[0057] The calculation module 202 is used to calculate the real-time short-circuit ratio, high short-circuit ratio threshold, and low short-circuit ratio threshold of the photovoltaic unit based on the operating data collected by the acquisition module 201. In conjunction with Embodiment 1, the calculation module 202 is used to execute step S2.

[0058] The detection module 203 is used to determine whether to issue a switching signal based on the grid-connected short-circuit ratio obtained by the calculation module 202 and a preset margin range (high short-circuit ratio threshold and low short-circuit ratio threshold). In conjunction with Embodiment 1, the detection module 203 is used to execute step S3.

[0059] The control module 204 is used to switch between current source control and voltage source control according to the switching signal issued by the detection module 203. Referring to Embodiment 1, the control module 204 is used to execute steps S4-S5.

[0060] Regarding the apparatus in this embodiment, the specific manner in which each unit performs its operations has been described in detail in Embodiment 1, and will not be elaborated upon here.

[0061] Those skilled in the art should understand that, for the sake of convenience and brevity, the device embodiments are only illustrated by the division of the above-mentioned functional modules or units. In actual applications, the above functions can be assigned to different functional modules or units as needed, that is, the internal structure of the device can be divided into different functional modules or units to complete all or part of the functions described above.

[0062] Example 3: See Figure 6 The purpose of this embodiment is to provide an electronic device 300, including at least one processor 301 and one or more memories 302 for storing executable instructions of the processor 301. The processor 301 executes the instructions in the memories 302 to implement the control method described in Embodiment 1.

[0063] The electronic device 300 also includes a bus 304, through which the processor 301 and the memory 302 are interconnected, or in other ways.

[0064] The processor 301 can be a central processing unit (CPU), a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The processor 301 can also be other devices with processing capabilities, such as circuits, devices, or software modules, without limitation. In one example, the processor 301 may include one or more CPUs, for example... Figure 6 CPU0 and CPU1 in the CPU.

[0065] The memory 302 can be a read-only memory (ROM) or other type of static storage device that can store static information and / or instructions; it can also be a random access memory (RAM) or other type of dynamic storage device that can store information and / or instructions; it can also be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, etc., without limitation.

[0066] It should be noted that the memory 302 can exist independently of the processor 301, or it can be integrated with the processor 301. The memory 302 can be used to store instructions, program code, or some data, etc. The memory 302 can be located inside or outside the electronic device 300, without restriction.

[0067] As an optional implementation, the electronic device 300 also includes a communication interface 303. The communication interface 303 is a wired interface (or port), such as a fiber distributed data interface (FDDI), a gigabit Ethernet interface (GE), etc. Alternatively, the communication interface 303 can be a wireless interface. The communication interface 303 can be a module, circuit, communication interface, or any device capable of communication. The communication interface 303 is used to communicate with other devices or other communication networks, such as Ethernet, radio access network (RAN), wireless local area network (WLAN), etc.

[0068] As an optional implementation, the electronic device 300 also includes an input device 305 and an output device 306. For example, the input device 305 is a device such as a keyboard, mouse, microphone, or joystick, and the output device 306 is a device such as a display screen or speaker.

[0069] It should be noted that electronic device 300 can be a desktop computer, laptop computer, network server, mobile phone, tablet computer, wireless terminal, embedded device, chip system, or something else. Figure 6 Equipment with a similar structure. Furthermore... Figure 6 The structural composition shown herein does not constitute a limitation on the terminal device, except... Figure 6 In addition to the components shown, the electronic device 300 may include more or fewer components than illustrated, or combine certain components, or have different component arrangements.

[0070] Example 4: The purpose of this example is to provide a computer-readable storage medium.

[0071] All or part of the processes in the above method embodiments can be instructed by computer instructions to be completed by related hardware. The program can be stored in the computer-readable storage medium. When the program is executed, it can implement the control method described in Embodiment 1.

[0072] The computer-readable storage medium can be an internal storage unit of the electronic device of Embodiment 3, such as a hard disk or memory. The computer-readable storage medium can also be an external storage device of the electronic device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc. Furthermore, the computer-readable storage medium can include both internal storage units and external storage devices of the aforementioned electronic device. The computer-readable storage medium is used to store computer programs and other programs and data required by the electronic device. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0073] Based on the several embodiments provided in this application, it should be understood that the provided apparatus and method can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of modules or units is only a logical functional division, and there may be other division methods in actual implementation. For example, multiple modules, units, or components may be combined or integrated into another device, or some features may be ignored or not executed.

[0074] Furthermore, in the device embodiments of this application, each functional module or unit can be integrated into one unit, or each module or unit can exist physically separately, or two or more modules or units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional module.

[0075] If the integrated units described above are implemented as software functional modules and sold or used as independent products, they can be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A photovoltaic unit control method based on a hybrid control of grid-connected and grid-following types, characterized in that, include: Add grid-type control based on DC voltage synchronization to the grid-connected converter control logic of the photovoltaic unit; The real-time short-circuit ratio, high short-circuit ratio threshold, and low short-circuit ratio threshold are obtained based on the real-time operating data of the photovoltaic unit. When the real-time short-circuit ratio is higher than the high short-circuit ratio threshold, the voltage source control is switched to the current source control; when the real-time short-circuit ratio is lower than the low short-circuit ratio threshold, the current source control and voltage source control are pre-synchronized, and after pre-synchronization, the current source control is switched to the voltage source control. After the control switch is completed, the current source control and voltage source control are resynchronized to prepare for the next control switch.

2. The photovoltaic unit control method based on hybrid control of grid-connected and grid-following types according to claim 1, characterized in that, Incorporating grid-connected control methods based on DC voltage synchronization into the grid-connected converter control logic of photovoltaic units includes: DC voltage synchronization control is introduced into the grid-side DC voltage control of photovoltaic units. The process of DC voltage synchronization control is calculated as follows: , Where θ represents the synchronization angle of the DC voltage synchronization control output. Indicates the modulation voltage. The reference value representing the AC bus voltage. This indicates the DC voltage value of the photovoltaic unit. This indicates the rated DC voltage of the photovoltaic unit. The reference value representing the modulation voltage. This represents the reference value for the reactive power of the photovoltaic unit. This represents the control gain of the reactive power loop. Indicates the system's rated capacity. Represents the reference value of angular frequency. Indicates the initial angular frequency. and These represent the proportional and integral coefficients of the DC voltage synchronous controller, respectively. This indicates the reference value of the DC voltage of the photovoltaic unit. This represents the reactive power value of the photovoltaic unit; In the outer-loop DC voltage control, a DC voltage feedforward is introduced, and the control process of the outer and inner loops is calculated as follows: , , ;in, This represents the reference value for the d-axis current of the photovoltaic unit. This represents the d-axis modulation ratio of the grid-side converter. This indicates the q-axis modulation ratio of the grid-side converter. The feedback coefficient represents the DC voltage. This represents a reference value for the d-axis voltage of the photovoltaic unit. This represents the d-axis voltage value of the photovoltaic unit. and These are the proportional coefficient and integral coefficient of the outer voltage loop, respectively. and These are the proportional coefficient and integral coefficient of the inner current loop, respectively. This indicates the DC voltage value of the photovoltaic unit. and These represent the actual feedback values ​​of the d-axis and q-axis currents of the photovoltaic unit, respectively. This represents the reference value for the q-axis current of the photovoltaic unit.

3. The photovoltaic unit control method based on hybrid control of grid-connected and grid-following types according to claim 1, characterized in that, The low short-circuit ratio threshold is expressed as: Where U represents the voltage output by the converter to the power grid, and E represents the electromotive force inside the system.

4. The photovoltaic unit control method based on hybrid control of grid-connected and grid-following types according to claim 1, characterized in that, The high short-circuit ratio threshold is expressed as: ,in P represents the impedance of the power grid, and P and U represent the active power and voltage output by the converter to the power grid, respectively.

5. The photovoltaic unit control method based on hybrid control of grid-connected and grid-following types according to claim 1, characterized in that, Both the pre-synchronization and re-synchronization methods are expressed as follows: , , ;in This indicates the angular frequency reference of the synchronous control output. This represents the internal potential reference of the synchronous control output. This represents the inner loop reference value of the synchronous control output current. Indicates the initial angular frequency. This indicates the output phase angle based on DC voltage synchronization. This indicates the phase angle of the phase-locked loop output. Indicates the reference value for the inner current loop in the network configuration; This indicates the reference value for the inner loop of the grid current; The compensation coefficient representing the current. The initial electromotive force of the system is given by U, and the voltage value at the AC terminal of the inverter is given by U. Represents the angular frequency compensation coefficient. This represents the internal potential compensation coefficient.

6. The photovoltaic unit control method based on hybrid control of grid-connected and grid-following types according to claim 5, characterized in that, The output phase angle based on DC voltage synchronization is expressed as: ,in This is the reference value for angular frequency. Indicates the initial value of angular frequency. and These are the proportional and integral coefficients of the DC voltage synchronous controller. This indicates the DC voltage value of the photovoltaic unit. This indicates the rated DC voltage of the photovoltaic unit. This indicates the reference value of the DC voltage for the photovoltaic unit.

7. The photovoltaic unit control method based on hybrid control of grid-connected and grid-following types according to claim 5, characterized in that, The phase angle of the phase-locked loop output is expressed as: , , ,in This is the output angular frequency of the phase-locked loop. Indicates the rated angular frequency. and Phase-locked loop controllers The proportional coefficient and integral coefficient.

8. A photovoltaic unit control device based on hybrid control of grid-connected and grid-following types, characterized in that, It includes a data acquisition module, a calculation module, a detection module, and a control module; The acquisition module is used to collect real-time operating data of the photovoltaic unit; The calculation module is used to calculate the real-time grid-connected short-circuit ratio, high short-circuit ratio threshold, and low short-circuit ratio threshold of the photovoltaic unit based on the operating data collected by the acquisition module. The detection module is used to determine whether to issue a switching signal based on the grid-connected short-circuit ratio obtained by the calculation module, and on a high short-circuit ratio threshold and a low short-circuit ratio threshold. The control module is used to switch between current source control and voltage source control according to the switching signal issued by the detection module.

9. An electronic device, characterized in that, It includes a processor and a memory; the memory is used to store executable instructions, and the processor is used to execute the instructions to implement the control method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The readable storage medium stores instructions that, when executed, implement the control method according to any one of claims 1-7.

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