Grid-connected photovoltaic system and operation method therefor

Abstract

The present application relates to a grid-connected photovoltaic system and an operation method therefor. A switch changeover apparatus is provided between a photovoltaic panel and a direct-current converter, wherein an input end of the switch changeover apparatus is connected to the photovoltaic panel, and a first output end and a second output end of the switch changeover apparatus are connected to a micro-inverter and the direct-current converter, respectively; and the switch changeover apparatus is further connected to a processor. When the grid-connected photovoltaic system has the requirement for replacing an energy storage battery, it is only necessary to control, by means of the processor, the switch changeover apparatus to act to connect the photovoltaic panel to the micro-inverter, such that continuous grid-connected operation can be ensured; and after the replacement of the energy storage battery is completed, it is also only necessary to control, by means of the processor, the switch changeover apparatus to act and perform changeover to connect the direct-current converter to the photovoltaic panel. During replacement of the energy storage battery, a user does not need to manually remove or install a circuit, and the whole changeover process is implemented by means of the actions of the processor and the switch changeover apparatus, thereby effectively solving the problems of a rewiring operation of the photovoltaic panel being cumbersome and consuming time and labor during the replacement of the energy storage battery.

Description

Photovoltaic grid-connected system and operation method thereof Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a photovoltaic grid-connected system and an operating method thereof. Background Art

[0002] With the development of new energy technologies, photovoltaic power generation has gradually gained widespread application due to its advantages such as stable and reliable operation, simple operation and maintenance, low maintenance costs, and long service life. Grid-connected photovoltaic systems, consisting of photovoltaic panels and energy storage batteries, are generally connected to the AC grid through microinverters for grid operation. If the energy storage batteries are damaged, the photovoltaic panels must be rewired to ensure continuous operation of the AC grid connected to the microinverters. However, rewiring photovoltaic panels is cumbersome, time-consuming, and labor-intensive. Summary of the Invention

[0003] Based on this, it is necessary to provide a photovoltaic grid-connected system and an operating method thereof to solve the problem that the rewiring operation of the photovoltaic panels is cumbersome, time-consuming and labor-intensive when the energy storage battery is replaced.

[0004] The present application provides a photovoltaic grid-connected system, comprising: an energy storage battery, a photovoltaic panel, a microinverter, a switching device, a DC converter, and a processor, wherein the microinverter is used to connect to an AC power grid; an input end of the switching device is connected to the photovoltaic panel, a first output end of the switching device is connected to the microinverter, and a second output end of the switching device is connected to a DC converter; the DC converter is connected to the photovoltaic panel, the energy storage battery, and the microinverter, respectively; and the processor is connected to the switching device and the DC converter, respectively.

[0005] The aforementioned photovoltaic grid-connected system also includes a switching device between the photovoltaic panel and the DC converter. The switching device's input is connected to the photovoltaic panel, while its first and second outputs are connected to the microinverter and DC converter, respectively. The switching device is further connected to a processor. In this way, if the photovoltaic grid-connected system needs to replace the energy storage battery, the processor simply controls the switching device to connect the photovoltaic panel to the microinverter, ensuring continued grid-connected operation. After the energy storage battery is replaced, the processor similarly controls the switching device to connect the DC converter to the photovoltaic panel. This solution eliminates the need for manual wiring removal and installation when replacing the energy storage battery; the entire switching process is accomplished through the processor and switching device. This effectively eliminates the cumbersome and time-consuming issue of rewiring the photovoltaic panel when replacing the energy storage battery.

[0006] In one embodiment, the switch device is a relay.

[0007] In one embodiment, the photovoltaic panel includes a first photovoltaic panel and a second photovoltaic panel, the switching device includes a first switching device and a second switching device, and the DC converter includes a first DC converter and a second DC converter; the first photovoltaic panel is connected to the input end of the first switching device, the first output end of the first switching device is connected to the micro-inverter, the second output end of the first switching device is connected to the first DC converter, and the first DC converter is connected to the first photovoltaic panel, the energy storage battery, and the micro-inverter respectively; the second photovoltaic panel is connected to the input end of the second switching device, the first output end of the second switching device is connected to the micro-inverter, the second output end of the second switching device is connected to the second DC converter, and the second DC converter is connected to the second photovoltaic panel, the energy storage battery, and the micro-inverter respectively.

[0008] In one embodiment, the first DC converter is consistent with the second DC converter, and the first DC converter includes a first conversion unit and a second conversion unit. The first conversion unit is connected to the second output end of the first switching device, the first photovoltaic panel and the energy storage battery, and the second conversion unit is connected to the energy storage battery and the micro-inverter.

[0009] In one embodiment, the first conversion unit includes a first switching device, a second switching device, a third switching device, a fourth switching device, a first inductor and a first capacitor, the first end of the first switching device is connected to the second output end of the first switching device, the second end of the first switching device is connected to the first end of the second switching device and the first end of the first inductor, the second end of the first inductor is connected to the first end of the third switching device and the first end of the fourth switching device, the second end of the third switching device is connected to the first end of the first capacitor and the energy storage battery, the second end of the second switching device is connected to the first photovoltaic panel and the second end of the fourth switching device, the second end of the first capacitor is connected to the second end of the fourth switching device and the energy storage battery, and the third end of the first switching device, the third end of the second switching device, the third end of the third switching device and the third end of the fourth switching device are respectively connected to the processor.

[0010] And / or, in one embodiment, the second conversion unit includes a fifth switching device, a sixth switching device, a second inductor and a second capacitor, the first end of the fifth switching device is connected to the energy storage battery, the second end of the fifth switching device is connected to the first end of the sixth switching device and the first end of the second inductor, the second end of the second inductor is connected to the first end of the second capacitor and the micro-inverter, the second end of the second switching device is connected to the energy storage battery, and the second end of the second capacitor is connected to the second end of the second switching device and the micro-inverter.

[0011] An operating method based on the above-mentioned photovoltaic grid-connected system includes: when the energy storage battery needs to be replaced, controlling the input end and the first output end of the switching device to be connected; when the energy storage battery is replaced, obtaining the output voltage of the photovoltaic panel; and switching the input end and the second output end of the switching device to be connected according to the output voltage.

[0012] In one embodiment, the output voltage includes a first output voltage of a first photovoltaic panel and a second output voltage of a second photovoltaic panel; switching the input end and the second output end of the switch switching device to be connected according to the output voltage includes: if the first output voltage is greater than a first preset voltage threshold and the second output voltage is less than a second preset voltage threshold, switching the input end and the second output end of the first switch switching device connected to the first photovoltaic panel to be connected; the second preset voltage threshold is less than the first preset voltage threshold; if the first output voltage is less than the second preset voltage threshold and the second output voltage is greater than the first preset voltage threshold, switching the input end and the second output end of the second switch switching device connected to the second photovoltaic panel to be connected; if both the first output voltage and the second output voltage are greater than the first preset voltage threshold, switching the input end and the second output end of the switch switching device to be connected according to the difference between the first output voltage and the second output voltage.

[0013] In one embodiment, switching the input end and the second output end of the switching device to be connected according to the difference between the first output voltage and the second output voltage includes: if the difference between the first output voltage and the second output voltage is less than a third preset voltage threshold, switching the input end and the second output end of the first switching device to be connected, and simultaneously switching the input end and the second output end of the second switching device to be connected; if the difference between the first output voltage and the second output voltage is greater than or equal to the third preset voltage threshold, switching the input end and the second output end of the switching device corresponding to the photovoltaic panel with the larger output voltage to be connected.

[0014] In one embodiment, when the input end and the second output end of the first switching device are switched to be connected, and the input end and the second output end of the second switching device are switched to be connected, the method further includes: performing a double closed-loop analysis based on the first output voltage of the first photovoltaic panel and the first preset current limit value, and outputting a first switching control signal to the first conversion unit of the first DC converter so that the first output voltage of the first photovoltaic panel is consistent with the voltage of the energy storage battery;

[0015] And / or, a double closed-loop analysis is performed based on the voltage of the energy storage battery and the second preset current limit value, and a second switch control signal is output to the second conversion unit of the first DC converter to make the voltage of the energy storage battery consistent with the input voltage of the micro-inverter.

[0016] In one embodiment, the operating method further includes: when the energy storage battery is in a charge-and-discharge operation state and the energy storage battery is fully charged, controlling the input end and the first output end of the switching device to be connected; regulating the DC converter according to the open-circuit voltage of the photovoltaic panel so that the input voltage of the micro-inverter is consistent with the input voltage before the switching device is actuated; switching the input end and the second output end of the switching device to be connected, and cutting off the connection between the energy storage battery and the DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] FIG1 is a schematic diagram of the structure of a photovoltaic grid-connected system according to an embodiment of the present application;

[0019] FIG2 is a schematic structural diagram of a photovoltaic grid-connected system according to another embodiment of the present application;

[0020] FIG3 is a schematic flow chart of an operating method of a photovoltaic grid-connected system according to an embodiment of the present application;

[0021] FIG4 is a schematic flow chart of an operating method of a photovoltaic grid-connected system according to another embodiment of the present application;

[0022] FIG5 is a schematic diagram of the operation logic flow of the photovoltaic grid-connected system in one embodiment of the present application. DETAILED DESCRIPTION

[0023] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0024] Please refer to Figure 1. A photovoltaic grid-connected system includes: an energy storage battery 14, a photovoltaic panel 11, a microinverter 15, a switching device 12, a DC converter 13, and a processor (not shown). The microinverter 15 is used to connect to the AC power grid; the input end of the switching device 12 is connected to the photovoltaic panel 11, the first output end of the switching device 12 is connected to the microinverter 15, and the second output end of the switching device 12 is connected to the DC converter 13; the DC converter 13 is respectively connected to the photovoltaic panel 11, the energy storage battery 14, and the microinverter 15; and the processor is respectively connected to the switching device 12 and the DC converter 13.

[0025] Specifically, photovoltaic panel 11, also known as a photovoltaic module, is a device that utilizes the photoelectric effect of semiconductor materials to convert solar energy (light energy) into electrical energy. Generally speaking, due to the low output voltage of single-chip photovoltaic devices and the vulnerability of electrodes in unpackaged photovoltaic devices to environmental influences, a certain number of single-chip photovoltaic devices are typically connected in series and / or parallel and sealed to form photovoltaic panel 11. Energy storage battery 14 is an electrical energy storage device used to store the DC power generated by the photovoltaic panel 11 through the photoelectric effect. It can be a lithium battery, etc., without limitation.

[0026] The DC converter 13 is a device that converts a DC power source into another DC power source with different output characteristics. Based on the circuit structure, it can be categorized as a buck converter, a boost converter, a buck-boost converter, and a Cuck converter. The choice should be based on actual needs. The microinverter 15, also known as a micro-inverter, generally refers to an inverter with a power of 1000 watts or less and module-level MPPT (Maximum Power Point Tracking) in a photovoltaic power generation system. It can also be called a micro photovoltaic grid-connected inverter. Each photovoltaic panel 11 is equipped with a corresponding microinverter 15. This advantage is that it can independently control the MPPT of each photovoltaic panel 11, significantly improving overall efficiency. It also avoids the problems of centralized inverters, such as high DC voltage, poor low-light performance, and the "barrel effect."

[0027] The switch 12 is a switching device capable of switching between different circuits in response to an input control signal. A processor is a device that has certain data storage and processing functions. The specific type of processor is not limited to a single one and can include an MCU (Microcontroller Unit), a CPU (Central Processing Unit), or a DSP (Digital Signal Processor).

[0028] In the photovoltaic grid-connected system provided in the embodiments of the present application, if the energy storage battery 14 fails and needs to be replaced, the processor detects and obtains relevant information regarding the replacement of the energy storage battery 14. Specifically, a user may directly input relevant information into the processor, which then determines that the energy storage battery 14 needs to be replaced. Alternatively, the processor may monitor the operation of the energy storage battery 14 and, if the energy storage battery 14 fails, determine that the energy storage battery 14 needs to be replaced.

[0029] If energy storage battery 14 needs to be replaced, the processor sends a drive signal to switch device 12, causing it to activate and connect its input to its first output. DC power from photovoltaic panel 11 then flows into the input of switch device 12, exits through its first output, and enters microinverter 15. Microinverter 15 then inverts the DC power and converts it into AC power for supply to the AC grid. This allows the power generated by photovoltaic panel 11 to be directly transferred to the AC grid even when energy storage battery 14 is replaced, ensuring optimal energy utilization.

[0030] Afterward, the processor will detect whether the energy storage battery 14 has been replaced. Again, this detection method is not exclusive. In one embodiment, it can be achieved by detecting whether a user-input instruction indicating replacement completion has been received. In another embodiment, it can be achieved by detecting whether the energy storage battery 14 connected to the current photovoltaic grid-connected system has changed (for example, by checking the battery label).

[0031] If the processor detects that energy storage battery 14 has been replaced, to improve the reliability of the photovoltaic grid-connected system, the processor obtains the output voltage of photovoltaic panel 11, performs switching control based on the output voltage of photovoltaic panel 11, and inputs another drive signal to switch device 12, connecting the input terminal and the second output terminal. Through this switching action, the DC power generated by photovoltaic panel 11 is converted by DC converter 13 and ultimately stored in energy storage battery 14. The power required by the AC grid is then transmitted from energy storage battery 14 to microinverter 15 for conversion.

[0032] It should be noted that the number of energy storage batteries 14, photovoltaic panels 11, microinverters 15, switching devices 12, and DC converters 13 is not unique. In a more detailed embodiment, the photovoltaic grid-connected system may include a plurality of energy storage batteries 14, photovoltaic panels 11, microinverters 15, switching devices 12, and DC converters 13 of the same number. Each energy storage battery 14, photovoltaic panel 11, microinverter 15, switching device 12, and DC converter 13 is connected via the aforementioned connection relationship and ultimately connected to the AC grid via the microinverter 15. In another embodiment, the photovoltaic grid-connected system may also include a plurality of photovoltaic panels 11, switching devices 12, and DC converters 13 of the same number, with two or more photovoltaic panels 11 sharing one energy storage battery 14, or two or more photovoltaic panels 11 sharing one microinverter 15. The specific selection may be based on actual needs.

[0033] The above-mentioned photovoltaic grid-connected system also includes a switching device 12 disposed between the photovoltaic panel 11 and the DC converter 13. The input of the switching device 12 is connected to the photovoltaic panel 11, and the first and second outputs of the switching device 12 are connected to the microinverter 15 and the DC converter 13, respectively. The switching device 12 is further connected to the processor. Thus, if the photovoltaic grid-connected system needs to replace the energy storage battery 14, the processor simply controls the switching device 12 to connect the photovoltaic panel 11 with the microinverter 15, ensuring continued grid-connected operation. After the energy storage battery 14 is replaced, the processor similarly controls the switching device 12 to connect the DC converter 13 with the photovoltaic panel 11. This solution eliminates the need for the user to manually remove and install wiring when replacing the energy storage battery 14. The entire switching process is accomplished through the actions of the processor and the switching device 12, effectively resolving the cumbersome and time-consuming issue of rewiring the photovoltaic panel 11 when replacing the energy storage battery 14.

[0034] It should be noted that the specific type of switch device 12 is not limited. In one embodiment, the switch device 12 may include two switching devices. In different states, the corresponding switching device is controlled to be turned on and the other switching device is turned off. In other embodiments, a single-pole double-throw (SPDT) or double-pole double-throw (DPDT) device may be used, and the specific embodiment is not limited thereto.

[0035] In more detail, in one embodiment, the switch device 12 is a relay.

[0036] Specifically, this embodiment employs a single-pole, double-throw (SPDT) relay as the switching device 12. When the energy storage battery 14 needs to be replaced, or when the energy storage battery 14 has been replaced, the processor controls the relay's switch to a different state, thereby implementing the switching function of the interface. This embodiment employs a relay as the switching device 12, resulting in high switching reliability.

[0037] In one embodiment, the photovoltaic panel 11 includes a first photovoltaic panel and a second photovoltaic panel, the switching device 12 includes a first switching device and a second switching device, and the DC converter 13 includes a first DC converter and a second DC converter; the first photovoltaic panel is connected to the input end of the first switching device, the first output end of the first switching device is connected to the micro-inverter 15, the second output end of the first switching device is connected to the first DC converter, and the first DC converter is connected to the first photovoltaic panel, the energy storage battery 14 and the micro-inverter 15 respectively; the second photovoltaic panel is connected to the input end of the second switching device, the first output end of the second switching device is connected to the micro-inverter 15, the second output end of the second switching device is connected to the second DC converter, and the second DC converter is connected to the second photovoltaic panel, the energy storage battery 14 and the micro-inverter 15 respectively.

[0038] Specifically, in this embodiment, there are two photovoltaic panels 11, two switching devices 12, and two DC converters 13. The DC power generated by the first photovoltaic panel is converted by the first DC converter and stored in the energy storage battery 14. The DC power generated by the second photovoltaic panel is converted by the second DC converter and stored in the energy storage battery 14. Furthermore, the first switching device and the processor are used to connect and disconnect the first photovoltaic panel and the microinverter 15, while the second switching device and the processor are used to connect and disconnect the second photovoltaic panel and the microinverter 15.

[0039] It is understood that the energy storage battery 14 and microinverter 15 connected to the first DC converter, and the energy storage battery 14 and microinverter 15 connected to the second DC converter can be the same, or they can be configured differently or completely different. That is, in one embodiment, the first DC converter and the second DC converter can share the energy storage battery 14 and the microinverter 15. In another embodiment, the first DC converter and the second DC converter share the energy storage battery 14, but each is connected to a microinverter 15. In yet another embodiment, the first DC converter and the second DC converter can share the microinverter 15, but each is connected to a different energy storage battery 14. In yet another embodiment, the first DC converter and the second DC converter can each be connected to an energy storage battery 14 and a microinverter 15, and each can be connected to the same AC power grid through its corresponding microinverter 15.

[0040] It should be noted that, based on the above embodiment, where there are two photovoltaic panels 11, two switching devices 12, and two DC converters 13, when replacing the energy storage battery 14, it may be necessary to bypass both the first and second switching devices so that the input terminal is connected to the first output terminal. This means that the shared energy storage battery 14 is faulty and needs to be replaced, or both energy storage batteries 14 are faulty and need to be replaced. After the energy storage battery 14 is replaced, it is necessary to energize the relay (using the relay as an example, to control the input terminal of the switching device 12 to connect to the second output terminal). Direct energization without control often risks damaging the switching device 12. To activate the relay, the voltage across the relay must be controlled to within a certain voltage difference (e.g., 5V).

[0041] More specifically, the photovoltaic grid-connected system described above has two circuits: a circuit consisting of the first photovoltaic panel, a first switching device, a first DC converter, an energy storage battery 14, and a microinverter 15; and a circuit consisting of the second photovoltaic panel, a second switching device, a second DC converter, an energy storage battery 14, and a microinverter 15. If only the circuit corresponding to the first photovoltaic panel has power, while the circuit corresponding to the second photovoltaic panel does not, directly connecting the two circuits can easily cause voltage backflow to the circuit corresponding to the second photovoltaic panel, posing a certain safety hazard. Furthermore, the capacitance in the circuit corresponding to the second photovoltaic panel can easily cause a large current to be generated when the circuit is connected, potentially damaging the relay.

[0042] Therefore, in a more detailed embodiment, the first output voltage PV1 of the first photovoltaic panel and the second output voltage PV2 of the second photovoltaic panel are detected before being attracted. When PV1 is greater than 16V and PV2 is less than 10V, it is considered that only the output circuit corresponding to the first photovoltaic panel exists, and only the first switch switching device is attracted. When PV2 is greater than 16V and PV1 is less than 10V, it is considered that only the output circuit corresponding to the second photovoltaic panel exists, and only the second switch switching device is attracted. When both PV1 and PV2 are greater than 16V, it is determined whether the voltage difference between PV1 and PV2 is less than 5V. If so, it is considered that both the output circuit corresponding to the first photovoltaic panel and the output circuit corresponding to the second photovoltaic panel exist, and can be attracted at the same time; if the voltage difference is not less than 5V, only the switch switching device 12 corresponding to the circuit with the higher voltage among the two is attracted, and the other circuit is not attracted to prevent backflow.

[0043] Furthermore, the specific type of the DC converter 13 is not unique. Please refer to Figure 2. In one embodiment, the first DC converter is consistent with the second DC converter. The first DC converter includes a first conversion unit 131 and a second conversion unit 132. The first conversion unit 131 is connected to the second output end of the first switching device 121, the first photovoltaic panel 111 and the energy storage battery 14, and the second conversion unit 132 is connected to the energy storage battery 14 and the micro-inverter 15.

[0044] Specifically, in the solution of this embodiment, the first DC converter and the second DC converter both include a first conversion unit 131 and a second conversion unit 132, wherein the first conversion unit 131 is arranged between the photovoltaic panel 11 and the energy storage battery 14, and is used to convert the DC power generated by the photovoltaic panel 11 and store it in the energy storage battery 14. The second conversion unit 132 is arranged between the energy storage battery 14 and the microinverter 15, and is used to convert and transmit the electric energy stored in the energy storage battery 14 to the microinverter 15 for inversion processing, thereby supplying power to the AC power grid.

[0045] 2 , in one embodiment, the first conversion unit 131 includes a first switching device G1, a second switching device G2, a third switching device G3, a fourth switching device G4, a first inductor L1, and a first capacitor C1. A first end of the first switching device G1 is connected to the second output end of the first switching device 121, a second end of the first switching device G1 is connected to the first end of the second switching device G2 and the first end of the first inductor L1, a second end of the first inductor L1 is connected to the first end of the third switching device G3 and the first end of the fourth switching device G4, a second end of the third switching device G3 is connected to the first end of the first capacitor C1 and the energy storage battery 14, a second end of the second switching device G2 is connected to the first photovoltaic panel 111 and the second end of the fourth switching device G4, a second end of the first capacitor C1 is connected to the second end of the fourth switching device G4 and the energy storage battery 14, and a third end of the first switching device G1, a third end of the second switching device G2, a third end of the third switching device G3, and a third end of the fourth switching device G4 are respectively connected to the processor.

[0046] And / or, in one embodiment, the second conversion unit 132 includes a fifth switching device G5, a sixth switching device G6, a second inductor L2, and a second capacitor C2, a first end of the fifth switching device G5 is connected to the energy storage battery 14, a second end of the fifth switching device G5 is connected to the first end of the sixth switching device G6 and the first end of the second inductor L2, a second end of the second inductor L2 is connected to the first end of the second capacitor C2 and the micro-inverter 15, a second end of the second switching device G2 is connected to the energy storage battery 14, and a second end of the second capacitor C2 is connected to the second end of the second switching device G2 and the micro-inverter 15.

[0047] Specifically, in a more detailed embodiment, the first conversion unit 131 includes a first switching device G1, a second switching device G2, a third switching device G3, a fourth switching device G4, a first inductor L1 and a first capacitor C1, while the second conversion unit 132 includes a fifth switching device G5, a sixth switching device G6, a second inductor L2 and a second capacitor C2. After the energy storage battery 14 is replaced, when controlling the input end of the switching device 12 to connect to the second output end, it is necessary to control the on / off of the first switching device G1, the second switching device G2, the third switching device G3, and the fourth switching device G4 so that the first output voltage of the first photovoltaic panel 111 is consistent with the battery voltage. Furthermore, the on / off of the fifth switching device G5 and the sixth switching device G6 is controlled so that the battery voltage is consistent with the input voltage of the micro-inverter 15. The entire control process should not exceed 5 seconds (the time from the voltage of the micro-inverter 15 to the start of operation is 5s-10s). Otherwise, the micro-inverter 15 will start to operate, causing the input voltage of the micro-inverter 15 to drop rapidly, the photovoltaic grid-connected system to remain in the adjustment state, and the first switching device 121 to fail to engage. Furthermore, during the control process, the duty cycle of the first switching device G1 and the third switching device G3 cannot be directly controlled to 100%, otherwise it will easily cause a large current to be generated in the first capacitor C1, ultimately damaging the switching devices.

[0048] Please refer to FIG. 3 . The present application provides an operation method based on the above-mentioned photovoltaic grid-connected system, including step 302 , step 304 and step 306 .

[0049] Step 302: When the energy storage battery needs to be replaced, the input end and the first output end of the control switch device are connected.

[0050] Step 304: When the energy storage battery is replaced, the output voltage of the photovoltaic panel is obtained.

[0051] Step 306 : switching the input terminal of the switching device to be connected to the second output terminal according to the output voltage.

[0052] Specifically, in the photovoltaic grid-connected system as shown in the above embodiment and the accompanying drawings, in the photovoltaic grid-connected system provided by the embodiment of the present application, in the event that the energy storage battery 14 fails and needs to be replaced, the processor monitors and obtains relevant information regarding the replacement of the energy storage battery 14. Specifically, the user may directly input relevant information into the processor, which then determines that the energy storage battery 14 needs to be replaced. Alternatively, the processor may monitor the operation of the energy storage battery 14 and, in the event of a failure of the energy storage battery 14, determine that the energy storage battery 14 needs to be replaced.

[0053] If energy storage battery 14 needs to be replaced, the processor sends a drive signal to switch device 12, causing it to activate and connect its input to its first output. DC power from photovoltaic panel 11 then flows into the input of switch device 12, exits through its first output, and enters microinverter 15. Microinverter 15 then inverts the DC power and converts it into AC power for supply to the AC grid. This allows the power generated by photovoltaic panel 11 to be directly transferred to the AC grid even when energy storage battery 14 is replaced, ensuring optimal energy utilization.

[0054] Afterward, the processor will detect whether the energy storage battery 14 has been replaced. Again, this detection method is not exclusive. In one embodiment, this can be achieved by detecting whether a user-input instruction indicating replacement completion has been received. In another embodiment, this can be achieved by detecting whether the energy storage battery 14 connected to the current photovoltaic grid-connected system has changed (for example, by detecting a battery tag).

[0055] If the processor detects that energy storage battery 14 has been replaced, to improve the reliability of the photovoltaic grid-connected system, the processor obtains the output voltage of photovoltaic panel 11, performs switching control based on the output voltage of photovoltaic panel 11, and inputs another drive signal to switch device 12, connecting the input terminal and the second output terminal. Through this switching action, the DC power generated by photovoltaic panel 11 is converted by DC converter 13 and ultimately stored in energy storage battery 14. The power required by the AC grid is then transmitted from energy storage battery 14 to microinverter 15 for conversion.

[0056] Referring to FIG. 4 , in one embodiment, the output voltage includes a first output voltage of the first photovoltaic panel 111 and a second output voltage of the second photovoltaic panel; step 306 includes step 402 , step 404 and step 406 .

[0057] Step 402 : If the first output voltage is greater than a first preset voltage threshold and the second output voltage is less than a second preset voltage threshold, switching the input terminal and the second output terminal of a first switching device connected to the first photovoltaic panel to be connected.

[0058] Step 404 : If the first output voltage is less than the second preset voltage threshold and the second output voltage is greater than the first preset voltage threshold, switching the input terminal and the second output terminal of the second switching device connected to the second photovoltaic panel to be connected.

[0059] Step 406 : If both the first output voltage and the second output voltage are greater than the first preset voltage threshold, the input terminal and the second output terminal of the switching device are switched to be connected according to the difference between the first output voltage and the second output voltage.

[0060] Specifically, the second preset voltage threshold is lower than the first preset voltage threshold. The values ​​of the first preset voltage threshold and the second preset voltage threshold are not unique. In one embodiment, considering that when the lighting conditions are relatively good, the voltage output by the photovoltaic panel 11 is higher than 16V, when the lighting conditions are average, the voltage output by the photovoltaic panel 11 is generally between 10V and 16V, and when the photovoltaic panel 11 is shaded or cloudy, the output of the photovoltaic panel 11 will be lower than 10V. Therefore, the first preset voltage threshold can be set to 16V and the second preset voltage threshold can be set to 10V.

[0061] Before the energization, the processor detects the first output voltage PV1 of the first photovoltaic panel 111 and the second output voltage PV2 of the second photovoltaic panel. When PV1 is greater than 16V and PV2 is less than 10V, it is considered that only the output line corresponding to the first photovoltaic panel 111 exists, and only the first switch switching device 121 is energized. When PV2 is greater than 16V and PV1 is less than 10V, it is considered that only the output line corresponding to the second photovoltaic panel exists, and only the second switch switching device is energized. When both PV1 and PV2 are greater than 16V, it is necessary to further combine the difference between the first output voltage and the second output voltage to determine which photovoltaic panel 11 corresponds to the output line switch switching device 12 to be energized. In this way, in the case of multiple photovoltaic output lines, it is possible to effectively energize and cause voltage backflow, thereby improving the operational reliability of the photovoltaic grid-connected system.

[0062] In one embodiment, according to the difference between the first output voltage and the second output voltage, the input terminal and the second output terminal of the switching device are connected, including:

[0063] If the difference between the first output voltage and the second output voltage is less than the third preset voltage threshold, the input end and the second output end of the first switch switching device are switched to be connected, and the input end and the second output end of the second switch switching device are switched to be connected.

[0064] If the difference between the first output voltage and the second output voltage is greater than or equal to a third preset voltage threshold, the input end and the second output end of the switch device corresponding to the photovoltaic panel with the larger output voltage are connected.

[0065] Specifically, the third preset voltage threshold is less than the second preset voltage threshold. More specifically, the third preset voltage threshold can be set to 5V. When both PV1 and PV2 are greater than 16V, the controller determines whether the voltage difference between PV1 and PV2 is less than 5V. If so, it is assumed that both the output circuit corresponding to the first photovoltaic panel 111 and the output circuit corresponding to the second photovoltaic panel are present and can be simultaneously energized. If the voltage difference is not less than 5V, only the switch device 12 corresponding to the circuit with the higher voltage is energized, and the other circuit is not energized to prevent backflow.

[0066] In one embodiment, when the input end and the second output end of the first switch switching device 121 are switched to be connected, and the input end and the second output end of the second switch switching device are switched to be connected, the method further includes: performing a double closed-loop analysis based on the first output voltage of the first photovoltaic panel and the first preset current limit value, and outputting a first switch control signal to the first conversion unit of the first DC converter, so that the first output voltage of the first photovoltaic panel is consistent with the voltage of the energy storage battery;

[0067] And / or, a double closed-loop analysis is performed based on the voltage of the energy storage battery and the second preset current limit value, and a second switch control signal is output to the second conversion unit of the first DC converter to make the voltage of the energy storage battery consistent with the input voltage of the micro inverter.

[0068] Specifically, after the energy storage battery 14 is replaced, when the input end of the switching device 12 is connected to the second output end, the first output voltage of the first photovoltaic panel 111 must be aligned with the battery voltage by controlling the on / off of the first switching device G1, the second switching device G2, the third switching device G3, and the fourth switching device G4. Furthermore, the battery voltage must be aligned with the input voltage of the micro-inverter 15 by controlling the on / off of the fifth switching device G5 and the sixth switching device G6. The entire control process must take no longer than 5 seconds (the time it takes for the micro-inverter 15 to establish voltage and start operating is 5s-10s). Otherwise, the micro-inverter 15's input voltage will rapidly decrease upon operation, causing the photovoltaic grid-connected system to remain in an adjustment state and the first switching device 121 to fail to engage. Furthermore, during the control process, the duty cycle of the first switching device G1 and the third switching device G3 cannot be directly controlled to 100%, as this will easily cause a large current to flow in the first capacitor C1, ultimately damaging the switching devices.

[0069] For more detailed information, see FIG5 . The photovoltaic panel 11 includes a first photovoltaic panel 111 and a second photovoltaic panel 112, and the switching device 12 includes a first switching device 121 and a second switching device 122. Taking the output circuit corresponding to the first photovoltaic panel 111 as an example, dual closed-loop regulation is required to control the on / off operation of each switching device in the DC conversion unit. To ensure that the first output voltage of the first photovoltaic panel 111 is consistent with the voltage of the energy storage battery 14, the target output value of the voltage outer loop is set to the first output voltage of the first photovoltaic panel 111, and the first preset current limit value is set to the inner current loop. The processor calculates the PWM (pulse width modulation) signals required for driving the first, second, third, and fourth switching devices G1, G2, G3, and G4, respectively, based on a control algorithm pre-stored in the processor. These signals are then used to generate switching signals G1, G2, G3, and G4, which respectively drive the first, second, third, and fourth switching devices G1, G2, G3, and G4. In this way, it is possible to ensure that there is no large current when the first switch 121 is closed, and the first switch device 121 can be closed at the fastest speed.

[0070] Similarly, to ensure consistency between the voltage of the energy storage battery 14 and the input voltage of the micro-inverter 15, dual closed-loop control is also employed. The target output value of the outer voltage loop is set to the voltage of the energy storage battery 14, while the inner current loop is set to a second preset current limit value. Calculations are performed based on a pre-stored control algorithm in the processor to obtain the PWM signals required for driving the fifth and sixth switching devices G5 and G6. These signals are then used to generate switching signals to respectively drive the fifth and sixth switching devices G5 and G6. This ensures that no high current flows during energization while energizing the first switching device 121 at the fastest possible speed. Ultimately, this ensures consistency between the input voltages from the first photovoltaic panel 111 to the micro-inverter 15, ultimately achieving energization of the first switching device 121 and connecting the input and second output terminals. A similar method is employed for the output circuit corresponding to the second photovoltaic panel, generating drive signals to drive the various switching devices in the DC converter 13, ultimately ensuring consistency between the output voltage of the second photovoltaic panel and the input voltage of the micro-inverter 15.

[0071] In one embodiment, the operating method further includes: when the energy storage battery 14 is in a charging and discharging operation state and the energy storage battery 14 is fully charged, controlling the input end and the first output end of the switch switching device 12 to be connected; according to the open-circuit voltage of the photovoltaic panel 11, regulating the DC converter 13 so that the input voltage of the micro-inverter 15 is consistent with the input voltage before the switch switching device 12 is actuated; switching the input end and the second output end of the switch switching device 12 to be connected, and cutting off the connection between the energy storage battery 14 and the DC converter 13.

[0072] Specifically, when the energy storage battery 14 is not fully charged, the energy from the photovoltaic panel 11 first flows into the energy storage battery 14 for charging, and then discharges from the energy storage battery 14 to the micro-inverter 15. This charging and discharging process continues until the battery is fully charged. If the energy storage battery 14 is fully charged, but the current power of the photovoltaic panel 11 exceeds the grid-connected power of the micro-inverter 15 (typically 800W or 1000W, set by the user), continued charging and discharging will cause the energy storage battery 14 to remain in a circulating state, so bypass is also required. This process requires first disabling charging, that is, connecting the input terminal and the first output terminal of the switching device 12, so that the photovoltaic panel 11 outputs directly to the micro-inverter 15. The processor quickly detects the open-circuit voltage of the photovoltaic panel 11 and then controls it through the DC converter 13, so that the output voltage of the DC converter 13 (i.e., the input voltage of the micro-inverter 15) is consistent with the input voltage before the switching device 12 is activated. After that, the switch is closed, that is, the input end and the second output end of the switch switching device 12 are connected; then the output is closed, that is, the connection between the energy storage battery 14 and the DC converter 13 is cut off (which can be achieved through the control of the battery management system). This can also maximize the energy utilization rate and eliminate the intermediate control link.

[0073] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A photovoltaic grid-connected system, characterized in that: include: Energy storage batteries; Photovoltaic panels; Microinverter, used to connect to the AC grid; A switch device, wherein an input end of the switch device is connected to the photovoltaic panel, a first output end of the switch device is connected to the micro-inverter, and a second output end of the switch device is connected to a DC converter; A DC converter is connected to the photovoltaic panel, the energy storage battery and the micro-inverter respectively; A processor is connected to the switch device and the DC converter respectively.

2. The photovoltaic grid-connected system according to claim 1, characterized in that: The switch device is a relay.

3. The photovoltaic grid-connected system according to claim 1 or 2, characterized in that: The photovoltaic panel includes a first photovoltaic panel and a second photovoltaic panel, the switch device includes a first switch device and a second switch device, and the DC converter includes a first DC converter and a second DC converter; The first photovoltaic panel is connected to the input end of the first switch switching device, the first output end of the first switch switching device is connected to the micro-inverter, the second output end of the first switch switching device is connected to the first DC converter, and the first DC converter is respectively connected to the first photovoltaic panel, the energy storage battery and the micro-inverter; The second photovoltaic panel is connected to the input end of the second switch switching device, the first output end of the second switch switching device is connected to the micro-inverter, the second output end of the second switch switching device is connected to the second DC converter, and the second DC converter is respectively connected to the second photovoltaic panel, the energy storage battery and the micro-inverter.

4. The photovoltaic grid-connected system according to claim 3, characterized in that: The first DC converter is consistent with the second DC converter, and the first DC converter includes a first conversion unit and a second conversion unit, the first conversion unit is connected to the second output end of the first switch switching device, the first photovoltaic panel and the energy storage battery, and the second conversion unit is connected to the energy storage battery and the micro inverter.

5. The photovoltaic grid-connected system according to claim 4, characterized in that: The first conversion unit includes a first switch device, a second switch device, a third switch device, a fourth switch device, a first inductor and a first capacitor, wherein a first end of the first switch device is connected to a second output end of the first switch switching device, a second end of the first switch device is connected to a first end of the second switch device and a first end of the first inductor, a second end of the first inductor is connected to a first end of the third switch device and a first end of the fourth switch device, a second end of the third switch device is connected to a first end of the first capacitor and the energy storage battery, a second end of the second switch device is connected to a first photovoltaic panel and a second end of the fourth switch device, a second end of the first capacitor is connected to a second end of the fourth switch device and the energy storage battery, and a third end of the first switch device, a third end of the second switch device, a third end of the third switch device and a third end of the fourth switch device are connected to the processor respectively; And / or, the second conversion unit includes a fifth switching device, a sixth switching device, a second inductor and a second capacitor, the first end of the fifth switching device is connected to the energy storage battery, the second end of the fifth switching device is connected to the first end of the sixth switching device and the first end of the second inductor, the second end of the second inductor is connected to the first end of the second capacitor and the micro-inverter, the second end of the second switching device is connected to the energy storage battery, and the second end of the second capacitor is connected to the second end of the second switching device and the micro-inverter.

6. An operating method of a photovoltaic grid-connected system according to any one of claims 1 to 5, characterized in that: include: When the energy storage battery needs to be replaced, controlling the input end of the switch device to be connected to the first output end; When the energy storage battery is replaced, obtaining the output voltage of the photovoltaic panel; According to the output voltage, the input terminal and the second output terminal of the switch switching device are switched to be connected.

7. The operating method according to claim 6, characterized in that: The output voltage includes a first output voltage of the first photovoltaic panel and a second output voltage of the second photovoltaic panel; and switching the input end and the second output end of the switch device to be connected according to the output voltage includes: If the first output voltage is greater than a first preset voltage threshold, and the second output voltage is less than a second preset voltage threshold, switching the input end and the second output end of the first switch device connected to the first photovoltaic panel to be connected; the second preset voltage threshold is less than the first preset voltage threshold; If the first output voltage is less than the second preset voltage threshold, and the second output voltage is greater than the first preset voltage threshold, switching the input end and the second output end of the second switch device connected to the second photovoltaic panel to be connected; If the first output voltage and the second output voltage are both greater than the first preset voltage threshold, the input terminal and the second output terminal of the switch switching device are switched to be connected according to the difference between the first output voltage and the second output voltage.

8. The operating method according to claim 7, characterized in that: The step of switching the input end of the switch device to be connected to the second output end according to the difference between the first output voltage and the second output voltage comprises: If the difference between the first output voltage and the second output voltage is less than a third preset voltage threshold, switching the input end of the first switch switching device to be connected to the second output end, and switching the input end of the second switch switching device to be connected to the second output end; If the difference between the first output voltage and the second output voltage is greater than or equal to the third preset voltage threshold, the input end and the second output end of the switch device corresponding to the photovoltaic panel with the larger output voltage are connected.

9. The photovoltaic grid-connected system according to claim 8, characterized in that: When the input end and the second output end of the first switch switching device are switched to be connected, and the input end and the second output end of the second switch switching device are switched to be connected, the method further includes: Performing a double closed-loop analysis according to the first output voltage of the first photovoltaic panel and the first preset current limit value, and outputting a first switch control signal to the first conversion unit of the first DC converter, so that the first output voltage of the first photovoltaic panel is consistent with the voltage of the energy storage battery; And / or, a double closed-loop analysis is performed according to the voltage of the energy storage battery and the second preset current limit value, and a second switch control signal is output to the second conversion unit of the first DC converter to make the voltage of the energy storage battery consistent with the input voltage of the micro inverter.

10. The operating method according to claim 6, characterized in that: Also includes: When the energy storage battery is in a charging and discharging operation state and the energy storage battery is fully charged, controlling the input end of the switch switching device to be connected to the first output end; According to the open circuit voltage of the photovoltaic panel, the DC converter is regulated so that the input voltage of the micro-inverter is consistent with the input voltage before the switching device is actuated; The input end and the second output end of the switch switching device are switched to be connected, and the connection between the energy storage battery and the DC converter is cut off.

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