Light storage system

Abstract

This invention provides a photovoltaic-energy storage system, belonging to the field of power electronics technology. The system includes a photovoltaic power generation system, an energy storage system, and a photovoltaic power connection unit. The photovoltaic power generation system and the photovoltaic power connection unit are connected in series to form a first branch. The energy storage system is connected to a second branch, which is in turn connected to the first branch. The energy storage system adjusts the frequency of its output AC power to exceed a preset frequency threshold range when a first condition is detected. Meeting the first condition is related to the photovoltaic-energy storage system being in an off-grid state. The photovoltaic power connection unit disconnects the first branch when the frequency of the AC power output from the energy storage system exceeds the frequency threshold range. The photovoltaic power connection unit allows for effective and unified disconnection of photovoltaic inverters, eliminating compatibility issues between different photovoltaic inverters and improving the reliability and feasibility of disconnecting photovoltaic inverters.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to photovoltaic energy storage systems. Background Technology

[0002] With the rapid development of new energy power systems, the proportion of renewable energy power generation, represented by photovoltaics, continues to rise. Energy storage systems, due to their excellent power regulation and energy time-shifting capabilities, have become a key technical means to enhance the grid's ability to accept high proportions of photovoltaics and ensure the stable operation of the grid.

[0003] Currently, in scenarios where it is necessary to disconnect the photovoltaic inverter in a photovoltaic-storage system, the AC frequency value output by the energy storage system is changed to trigger an over-frequency alarm and shut down the photovoltaic inverter, thereby achieving the purpose of disconnecting the photovoltaic inverter.

[0004] However, in practical applications, the over-frequency and under-frequency shutdown function of photovoltaic inverters often requires professional settings to be enabled effectively. The professional threshold for setting up such functions is high and time-consuming. Therefore, there is an urgent need to provide a more effective way to disconnect the photovoltaic inverter. Summary of the Invention

[0005] This invention provides a photovoltaic-storage system to solve the problem that the over-frequency and under-frequency shutdown function of current photovoltaic inverters often requires professional settings to be enabled effectively, which is a highly technical and time-consuming process.

[0006] In a first aspect, the present invention provides a photovoltaic-storage system, comprising: a photovoltaic power generation system, an energy storage system, and a photovoltaic power connection unit, wherein the photovoltaic power generation system and the photovoltaic power connection unit are connected in series to form a first branch, the energy storage system is connected to a second branch, and the second branch is connected to the first branch; The energy storage system is used to adjust the frequency of the output AC power to a range exceeding a preset frequency threshold when a first condition is detected; wherein, the first condition is related to the photovoltaic energy storage system being in an off-grid state; The photovoltaic power connection unit is used to control the photovoltaic power connection unit to disconnect the first branch when it is detected that the frequency of the AC power output by the energy storage system exceeds the frequency threshold range.

[0007] In some embodiments, the photovoltaic-storage system further includes a grid-connected / off-grid switching unit, wherein the first branch and the second branch are connected in parallel to the power grid via a first power switch in the grid-connected / off-grid switching unit, and the first branch and the second branch are connected in parallel to the load; The first condition being met includes any one of the following: The first power switch is in the off state; The first power switch is in the off state, and the electrical energy required by the load is less than a first value; The first power switch is in the off state, and the electrical energy required by the energy storage system is less than the second value; The first power switch is in the off state, the electrical energy required by the load is less than a first value, and the electrical energy required by the energy storage system is less than a second value.

[0008] In some embodiments, the photovoltaic power connection unit includes: A second power switch is connected to the first branch; A voltage conversion module is used to convert the collected AC power output from the energy storage system into a first voltage within a preset voltage range; A waveform conversion module is used to convert the first voltage, which is a sine wave, into a second voltage, which is a square wave. A microcontroller is configured to determine the frequency of the AC power output by the energy storage system based on the second voltage, and to control the second power switch to disconnect the first branch when the frequency of the AC power output by the energy storage system exceeds the frequency threshold range.

[0009] In some embodiments, the voltage conversion module includes an operational amplifier, the two input terminals of which are used to acquire the AC power output by the energy storage system, and the output terminal of the operational amplifier is connected to the input terminal of the waveform conversion module for outputting the first voltage; Alternatively, the voltage conversion module includes a transformer, the two input terminals of which are used to collect the AC power output by the energy storage system, and the output terminal of the transformer is connected to the input terminal of the waveform conversion module to output the first voltage.

[0010] In some embodiments, the waveform conversion module includes a comparator, one input of which is connected to the output of the voltage conversion module, the other input of which is grounded, and the output of which is connected to the input of the microcontroller. Alternatively, the waveform conversion module may include an optocoupler, the input of which is connected to the output of the voltage conversion module, and the output of which is connected to the input of the microcontroller.

[0011] In some of these embodiments, the microcontroller is specifically used for: Calculate the first duration of the high level in the second voltage and the second duration of the low level in the second voltage, respectively; Based on the first time and the second time, the frequency of the AC power output by the energy storage system is determined.

[0012] In some embodiments, the photovoltaic-storage system further includes a photovoltaic-storage system management unit connected to the microcontroller in the photovoltaic power connection unit; The optical storage system management unit is used to output the adjusted frequency threshold range to the microcontroller; The microcontroller is specifically used to control the second power switch to close or open based on the adjusted frequency threshold range.

[0013] In some embodiments, the photovoltaic power generation system includes at least one photovoltaic power generation module and at least one corresponding photovoltaic inverter; At least one of the photovoltaic power generation components is connected to the photovoltaic power connection unit via at least one corresponding photovoltaic inverter.

[0014] In some embodiments, the energy storage system is further configured to adjust the frequency of the output AC power to within the frequency threshold range if the first condition is not met. The photovoltaic power connection unit is also used to control the photovoltaic power connection unit to connect the first branch when the frequency of the AC power output by the energy storage system is detected to be within the frequency threshold range.

[0015] In some embodiments, the on-grid / off-grid switching unit is used for: When the first power switch is open and the power grid is detected to be energized, the frequency and phase of the AC power output by the energy storage system are detected. If the frequency and phase of the AC power output by the energy storage system are detected to be consistent with the frequency and phase of the AC power output by the power grid, the first power switch is controlled to close so that the photovoltaic power generation system and the energy storage system are connected to the grid.

[0016] Compared with the prior art, the photovoltaic-storage system provided by this invention includes a first branch where the photovoltaic power generation system is located and a second branch where the energy storage system is located. Since the second branch is connected to the first branch, in order to avoid the large electrical energy output by the photovoltaic power generation system on the first branch from impacting the energy storage system on the second branch, this application sets up a photovoltaic power connection unit on the first branch. When the energy storage system detects that a first condition is met, it can be considered that the output electrical energy of the photovoltaic power generation system may impact the energy storage system. Therefore, at this time, the frequency of the output AC power of the energy storage system can be adjusted to exceed the preset frequency range. Then, the photovoltaic power connection unit detects that... When the frequency of the AC power output by the energy storage system exceeds the preset frequency range, the first branch can be disconnected to disconnect the photovoltaic power generation system, thereby ensuring that the energy storage system is not damaged by the impact. There is no need to professionally configure the over / under frequency shutdown function of the photovoltaic inverter in the photovoltaic power generation system so that the photovoltaic power generation system can be effectively disconnected. Even if the photovoltaic power generation system includes multiple photovoltaic inverters from different manufacturers or models, the photovoltaic power connection unit set in this application can effectively and uniformly disconnect these photovoltaic inverters. There is no compatibility problem between different photovoltaic inverters, which improves the reliability and feasibility of disconnecting the photovoltaic inverter.

[0017] Details of one or more embodiments of the present invention are set forth in the following drawings and description to make other features, objects and advantages of the invention more readily apparent. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this invention, illustrate the invention. Those skilled in the art will recognize that other drawings can be derived from these drawings without any inventive effort. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is one of the structural schematic diagrams of the photovoltaic energy storage system provided by the present invention.

[0019] Figure 2 This is the second schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention.

[0020] Figure 3 This is the third schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention.

[0021] Figure 4 This is the fourth schematic diagram of the optical energy storage system provided by the present invention.

[0022] Figure 5 This is the fifth schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention.

[0023] Figure 6This is the sixth schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention.

[0024] Figure label: 10: Photovoltaic and energy storage system; 20: Power grid; 101: Photovoltaic power generation system; 102: Energy storage system; 103: Photovoltaic power connection unit; 104: Grid-connected / off-grid switching unit; 105: Photovoltaic-energy storage system management unit; 1031: Voltage conversion module; 1032: Waveform conversion module; 1033: Microcontroller; A: Operational amplifier; B: Comparator; K1: First power switch; K2: Second power switch. Detailed Implementation

[0025] To more clearly understand the objectives, technical solutions, and advantages of this invention, the technical solutions of this invention will be clearly and completely described and explained below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the general meaning understood by one of ordinary skill in the art to which this invention pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this invention do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this invention are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled” used in this invention are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “A plurality” used in this invention refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this invention are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0027] In related technologies, in scenarios where the photovoltaic inverter needs to be disconnected from the current photovoltaic-storage system, the AC frequency value output by the energy storage system is usually changed. When this frequency value exceeds the frequency threshold of the photovoltaic inverter, the photovoltaic inverter will trigger an over-frequency alarm and shut down, thereby achieving the purpose of disconnecting the photovoltaic inverter.

[0028] However, in practical applications, the energy storage system and the photovoltaic inverter may not be from the same manufacturer. Furthermore, the over / under frequency shutdown function of the photovoltaic inverter requires specialized configuration to be effective. If there are photovoltaic inverters from different manufacturers or models on site, configuring them to simultaneously enable the over / under frequency shutdown function becomes extremely difficult. Therefore, a more efficient method is needed to disconnect the photovoltaic inverter via frequency control.

[0029] To address the aforementioned issues, this invention provides a photovoltaic-storage system. By installing a photovoltaic power connection unit on the branch where the photovoltaic power generation system (including various photovoltaic inverters) is located, when the photovoltaic inverter needs to be disconnected from the photovoltaic storage system, the energy storage system can adjust the frequency of its output AC power. The photovoltaic power connection unit controls the connection or disconnection of the branch where the photovoltaic power generation system is located based on the frequency of the AC power output by the energy storage system. When the branch where the photovoltaic power generation system is located is disconnected, it can be considered that the photovoltaic inverter has been disconnected. This invention utilizes the photovoltaic power connection unit to uniformly disconnect various photovoltaic inverters, eliminating the need for technicians to perform professional settings for photovoltaic inverters from different manufacturers or models, effectively reducing the difficulty of disconnecting photovoltaic inverters.

[0030] The optical energy storage system of the present invention will now be described with reference to the accompanying drawings.

[0031] Figure 1 This is one of the structural schematic diagrams of the photovoltaic energy storage system provided by the present invention, such as... Figure 1 As shown, the optical storage system 10 may include: The photovoltaic power generation system 101, the energy storage system 102 and the photovoltaic power connection unit 103 are connected in series to form a first branch, the energy storage system 102 is connected to the second branch, and the second branch is connected to the first branch. The energy storage system 102 is used to adjust the frequency of the output AC power to a range exceeding a preset frequency threshold when a first condition is detected; wherein, the first condition is related to the photovoltaic energy storage system 10 being in an off-grid state; The photovoltaic power connection unit 103 is used to disconnect the first branch when the frequency of the AC power output by the energy storage system 102 exceeds the frequency threshold range.

[0032] It should be noted that the above frequency threshold range can be preset by technicians according to the actual situation, or it can be dynamically adjusted.

[0033] It should also be noted that the aforementioned frequency threshold range needs to be unified between the photovoltaic power connection unit 103 and the energy storage system 102, so that when the energy storage system 102 detects that the first condition is met and the output of AC power exceeds the preset frequency threshold range, the photovoltaic power connection unit 103 can determine that it is necessary to disconnect the photovoltaic power generation system 101 at this time, and control the photovoltaic power connection unit 103 to disconnect the first branch, so as to disconnect the photovoltaic power generation system 101 and the energy storage system 102, and avoid the output power of the photovoltaic power generation system 101 from impacting the energy storage system 102.

[0034] It should also be noted that the fulfillment of the first condition mentioned above may be related to the photovoltaic-storage system 10 being in an off-grid state. When the photovoltaic-storage system 10 is in an off-grid state, the large electrical energy output by the photovoltaic power generation system 101 is difficult to transmit normally to the grid side and will be transmitted to the energy storage system 102 through the first branch. The large electrical energy output by the photovoltaic power generation system 101 may impact the energy storage system 102, causing the energy storage system 102 to malfunction or even be damaged. In this regard, the energy storage system 102 can indirectly control the photovoltaic power connection unit 103 to disconnect the first branch between the photovoltaic power generation system 101 and the energy storage system 102 by adjusting the frequency of the output AC power, thereby preventing the photovoltaic power generation system 101 from transmitting large electrical energy to the energy storage system 102, and allowing the energy storage system 102 to operate normally.

[0035] Optionally, one specific implementation of the photovoltaic power generation system 101 is provided. The photovoltaic power generation system 101 may include at least one photovoltaic power generation module and at least one corresponding photovoltaic inverter; At least one photovoltaic power generation module is connected to the photovoltaic power connection unit 103 through at least one corresponding photovoltaic inverter.

[0036] It should be noted that the aforementioned photovoltaic power generation components include, for example, multiple solar cells and other components that can convert light energy into electrical energy. The direct current output by the photovoltaic power generation components is then converted into alternating current by a photovoltaic inverter.

[0037] Optionally, the photovoltaic inverters of the photovoltaic power generation system 101 may include multiple photovoltaic inverters from different manufacturers or models, or photovoltaic inverters from the same manufacturer or model. The present invention does not limit this.

[0038] In this embodiment of the invention, the photovoltaic-storage system 10 includes a first branch containing a photovoltaic power generation system 101 and a second branch containing an energy storage system 102. Since the second branch is connected to the first branch, to prevent the large electrical output of the photovoltaic power generation system 101 on the first branch from impacting the energy storage system 102 on the second branch, a photovoltaic power connection unit 103 is provided on the first branch. When the energy storage system 102 detects that a first condition is met, it can be considered that the output electrical energy of the photovoltaic power generation system 101 may impact the energy storage system 102. Therefore, the frequency of the output AC power of the energy storage system 102 can be adjusted to exceed a preset frequency range. When the photovoltaic power connection unit 103 detects that the frequency of the output AC power of the energy storage system 102 exceeds the preset frequency range, it can disconnect the first branch to disconnect the photovoltaic power generation system 101, thereby ensuring that the energy storage system 102 is not damaged by the impact. This eliminates the need for professional settings for the over / under frequency shutdown function of the photovoltaic inverter in the photovoltaic power generation system 101, allowing the photovoltaic power generation system 101 to be effectively disconnected. The photovoltaic power generation system 101 includes multiple photovoltaic inverters from different manufacturers or models. The photovoltaic power connection unit 103 provided in this application can effectively and uniformly disconnect these photovoltaic inverters, eliminating compatibility issues between different photovoltaic inverters and improving the reliability and feasibility of disconnecting the photovoltaic inverters. Furthermore, compared to setting up an additional control unit to detect whether the first condition is met and sending a signal to the photovoltaic power connection unit 103 to control its disconnection via an additional communication line, this embodiment of the invention allows the energy storage system 102 to detect whether the first condition is met and adjust the frequency of the output AC power based on the detection result to indirectly control the photovoltaic power connection unit 103 to disconnect or connect the first branch. This eliminates the need for an additional communication line between the control unit and the photovoltaic power connection unit 103, saving communication lines. Moreover, the photovoltaic power connection unit 103 directly detects the frequency and reacts faster, allowing it to disconnect the first branch as quickly as possible when the first condition is met, ensuring the normal operation of the energy storage system 102.

[0039] In some of these embodiments, another specific implementation of the optical storage system 10 is provided. Figure 2 This is the second schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention, as shown below. Figure 2 As shown, the photovoltaic-storage system 10 may also include a grid-connected / off-grid switching unit 104, wherein the first branch and the second branch are connected in parallel to the power grid 20 through the first power switch K1 in the grid-connected / off-grid switching unit 104, and the first branch and the second branch are connected in parallel to the load. Meeting the first condition can include any of the following: 1) The first power switch K1 is in the open state; 2) The first power switch K1 is in the open state, and the electrical energy required by the load is less than the first value; 3) The first power switch K1 is in the open state, and the electrical energy required by the energy storage system 102 is less than the second value; 4) The first power switch K1 is in the open state, the electrical energy required by the load is less than the first value, and the electrical energy required by the energy storage system 102 is less than the second value.

[0040] It should be noted that the first and second values ​​mentioned above can be flexibly set according to the actual situation, and there are no restrictions on this.

[0041] Specifically, the photovoltaic power generation system 10 may also include a grid-connected / off-grid switching unit 104. The photovoltaic power generation system 101 and the energy storage system 102 may be connected to the grid 20 via the grid-connected / off-grid switching unit 104 through the first branch and the second branch, respectively, to supply power to the grid 20 or be supplied by the grid 20. The grid-connected / off-grid switching unit 104 is used to control the grid connection or disconnection of the photovoltaic power generation system 101 and the energy storage system 102.

[0042] In addition, the photovoltaic power generation system 101 and the energy storage system 102 can be connected in parallel to the load through the first branch and the second branch, respectively, to supply power to the load.

[0043] Furthermore, since the photovoltaic power generation system 101 and the energy storage system 102 are connected in parallel, when the power grid 20 does not supply power to the photovoltaic power generation system 101 and the energy storage system 102, the power output of the photovoltaic power generation system 101 can also be supplied to the energy storage system 102 to charge the energy storage system 102.

[0044] Regarding the power supply relationship described above, the following situations may exist: In scenario 1, when the first power switch K1 of the grid-connected / off-grid switching unit 104 is in the open state, the photovoltaic-storage system 10 is disconnected from the grid. At this time, the electrical energy output by the photovoltaic power generation system 101 cannot be transmitted to the grid 20 through the grid-connected / off-grid switching unit 104, but can only be transmitted to the load or the energy storage system 102. The electrical energy output by the photovoltaic power generation system 101 may be large, which will have a large impact on the load or the energy storage system 102, and may easily damage the load or the energy storage system 102. Therefore, at this time, it can be considered that the first condition is met. The energy storage system 102 and the photovoltaic power connection unit 103 cooperate to cut off the first branch of the electrical energy output by the photovoltaic power generation system 101, ensuring that the load or the energy storage system 102 can operate normally.

[0045] In scenario 2, when the first power switch K1 of the grid-connected / off-grid switching unit 104 is in the off state, the photovoltaic-storage system 10 is disconnected from the grid. At this time, the electrical energy output by the photovoltaic power generation system 101 cannot be transmitted to the grid 20 through the grid-connected / off-grid switching unit 104, but can only be transmitted to the load or the energy storage system 102.

[0046] Unlike Case 1, this case also considers that the electrical energy output by the photovoltaic power generation system 101 can supply power to the load to ensure the normal operation of the load. If the electrical energy required by the load is detected to be less than the first value, for example, if the load stops operating for a period of time and does not require power supply, the large electrical energy output by the photovoltaic power generation system 101 will still have a large impact on the load or the energy storage system 102, which may easily damage the load or the energy storage system 102. Therefore, the first condition can be considered to be met at this time. The energy storage system 102 and the photovoltaic power connection unit 103 cooperate to cut off the first branch of the electrical energy output by the photovoltaic power generation system 101 to protect the load or the energy storage system 102 from damage due to impact.

[0047] In scenario 3, when the first power switch K1 of the grid-connected / off-grid switching unit 104 is in the off state, the photovoltaic-storage system 10 is disconnected from the grid. At this time, the electrical energy output by the photovoltaic power generation system 101 cannot be transmitted to the grid 20 through the grid-connected / off-grid switching unit 104, but can only be transmitted to the load or the energy storage system 102.

[0048] Unlike Case 1, this case also considers that the electrical energy output by the photovoltaic power generation system 101 can charge the energy storage system 102 to store electrical energy for later use. If the electrical energy required by the energy storage system 102 is detected to be less than the second value, for example, if the energy storage system 102 is fully charged, the large electrical energy output by the photovoltaic power generation system 101 will still have a large impact on the load or the energy storage system 102, which may easily damage the load or the energy storage system 102. Therefore, the first condition can be considered to be met at this time, and the energy storage system 102 and the photovoltaic power connection unit 103 cooperate to cut off the first branch of the electrical energy output by the photovoltaic power generation system 101 to protect the load or the energy storage system 102 from damage due to impact.

[0049] Case 4: When the first power switch K1 of the grid-connected / off-grid switching unit 104 is in the open state, the photovoltaic-storage system 10 is disconnected from the grid. At this time, the electrical energy output by the photovoltaic power generation system 101 cannot be transmitted to the grid 20 through the grid-connected / off-grid switching unit 104, but can only be transmitted to the load or the energy storage system 102.

[0050] Unlike case 1, this case considers the situation where the power output of the photovoltaic power generation system 101 can supply power to the load and charge the energy storage system 102. If the power required by the load is less than the first value and the power required by the energy storage system 102 is less than the second value, it is considered that the load and the energy storage system 102 do not need to be supplied or charged by the photovoltaic power generation system 101 at this time. In order to protect the load or the energy storage system 102 from damage due to impact, it can be considered that the first condition is met at this time. The energy storage system 102 and the photovoltaic power connection unit 103 cooperate to cut off the first branch of the power output of the photovoltaic power generation system 101.

[0051] In some of these embodiments, a specific implementation of the photovoltaic power connection unit 103 is provided. Figure 3 This is the third schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention, as shown below. Figure 3 As shown, the photovoltaic power connection unit 103 may include: The second power switch K2 is connected to the first branch; The voltage conversion module 1031 is used to convert the AC power output from the energy storage system 102 into a first voltage within a preset voltage range. The waveform conversion module 1032 is used to convert a first voltage that is a sine wave into a second voltage that is a square wave. The microcontroller 1033 is configured to determine the frequency of the AC power output by the energy storage system 102 based on the second voltage, and to control the second power switch K2 to disconnect the first branch when the frequency of the AC power output by the energy storage system 102 exceeds the frequency threshold range.

[0052] It should be noted that the above-mentioned preset voltage range can be flexibly set according to the actual situation. Usually, the larger AC current on the AC bus is converted to the preset voltage range that the waveform conversion module 1032 can recognize, so as to avoid the larger AC current on the AC bus from impacting the waveform conversion module 1032 and the microcontroller 1033.

[0053] Specifically, the voltage conversion module 1031 can first collect the AC power output by the energy storage system 102 and convert it into a first voltage within a preset voltage range, and output it to the waveform conversion module 1032. The waveform conversion module 1032 converts the first voltage (in the form of a sine wave) into a second voltage (in the form of a square wave) to facilitate the subsequent determination of the voltage frequency. Then, the microcontroller 1033 determines the frequency of the AC power output by the energy storage system 102 based on the second voltage. If the frequency of the AC power output by the energy storage system 102 is detected to exceed the frequency threshold range, the microcontroller controls the second power switch K2 to open to disconnect the first branch.

[0054] It should also be noted that the method for detecting the frequency of the AC power output by the energy storage system 102 described above can also be other methods that can determine the frequency of the AC power. This is just an example and there are no restrictions on this method.

[0055] Optionally, a specific implementation of the voltage conversion module 1031 is provided. Figure 4 This is the fourth schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention, as shown below. Figure 4As shown, the voltage conversion module 1031 may include an operational amplifier A. The two input terminals of the operational amplifier A are used to collect the AC power (L and N lines) output by the energy storage system 102. The output terminal of the operational amplifier A is connected to the input terminal of the waveform conversion module 1032 and is used to output a first voltage. Alternatively, the voltage conversion module 1031 may include a transformer, the two input terminals of which are used to collect the AC power output by the energy storage system 102, and the output terminal of the transformer is connected to the input terminal of the waveform conversion module 1032 for outputting a first voltage.

[0056] Specifically, for operational amplifier A, the alternating current output from the two input terminals of operational amplifier A can be converted into a first voltage output within a preset voltage range; for transformer, the two ends of the primary winding of transformer can be connected to the alternating current output by energy storage system 102, and the two ends of secondary winding are used to output the first voltage. The turns ratio between the primary winding and secondary winding can be flexibly set according to the actual situation to adjust the preset voltage range of the output first voltage.

[0057] Optionally, a specific implementation of the waveform conversion module 1032 is provided. For example... Figure 4 As shown, the waveform conversion module 1032 may include a comparator B. One input terminal of the comparator B is connected to the output terminal of the voltage conversion module 1031, and the other input terminal is grounded (0V). The output terminal of the comparator B is connected to the input terminal of the microcontroller 1033. Alternatively, the waveform conversion module 1032 may include an optocoupler, with the input of the optocoupler connected to the output of the voltage conversion module 1031 and the output of the optocoupler connected to the input of the microcontroller 1033.

[0058] Specifically, for comparator B, one of its input terminals is connected to the output terminal of voltage conversion module 1031 to receive the first voltage, and the other input terminal is grounded (0V). If the first voltage is greater than 0, comparator B outputs a high level; if the first voltage is less than 0, comparator B outputs a low level. When the first voltage is a sine wave, the comparator B can output a second voltage that is a square wave.

[0059] For the optocoupler, the input terminal of the optocoupler is connected to the output terminal of the voltage conversion module 1031 to receive the first voltage. Specifically, the light-emitting diode side of the optocoupler is connected to the output terminal of the voltage conversion module 1031. When the first voltage is positive, the light-emitting diode works normally and emits light. At this time, the photoelectric receiving side receives light and outputs a high level. When the first voltage is negative, the light-emitting diode does not work (does not emit light). At this time, the photoelectric receiving side does not receive light and outputs a low level, thereby converting the first voltage, which is a sine wave, into a second voltage, which is a square wave, for output.

[0060] In some embodiments, a specific implementation is provided that controls the second power switch K2 via a microcontroller 1033. For example... Figure 3 and Figure 4 As shown, the microcontroller 1033 is specifically used for: Calculate the first duration of the high level in the second voltage and the second duration of the low level in the second voltage, respectively; Based on the first and second time points, the frequency of the AC power output by the energy storage system 102 is determined.

[0061] Specifically, after receiving the second voltage in the form of a square wave, the microcontroller unit (MCU) 1033 can calculate the first time of the high level in the second voltage and the second time of the low level in the second voltage, and determine the frequency of the AC power output by the energy storage system 102 based on the first time and the second time. Specifically, it can calculate the sum of the first time and the second time as the period (T), and then calculate 1 / T as the frequency f of the AC power.

[0062] In some of these embodiments, a specific implementation of adjusting the frequency threshold range is provided. Figure 5 This is the fifth schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention, as shown below. Figure 5 As shown, in Figure 1 Based on this, the photovoltaic power storage system 10 may also include a photovoltaic power storage system management unit 105, which is connected to the microcontroller 1033 in the photovoltaic power connection unit 103; The photovoltaic storage system management unit 105 is used to output the adjusted frequency threshold range to the microcontroller 1033; The microcontroller 1033 is specifically used to control the second power switch K2 to close or open based on the adjusted frequency threshold range.

[0063] Specifically, the present invention can enable technicians to flexibly adjust the frequency threshold range by setting up a photovoltaic storage system management unit 105.

[0064] Optionally, the photovoltaic storage system management unit 105 may include an operable interface through which technicians can input an adjusted frequency threshold range to transmit via the photovoltaic storage system management unit 105 to the microcontroller 1033, so that the microcontroller 1033 can control the second power switch K2 to close or open based on the adjusted frequency threshold range.

[0065] Optionally, after obtaining the adjusted frequency threshold range, the photovoltaic-storage system management unit 105 can also output it to the energy storage system 102 so that the energy storage system 102 can update the frequency threshold range. Then, after detecting that the first condition is met, it can adjust the frequency of the output AC power to exceed the adjusted frequency threshold range, so as to cooperate with the photovoltaic power connection unit 103 to cut off the first branch.

[0066] In some embodiments, a specific implementation of controlling the optical storage system 10 when a first condition is not met is provided. For example... Figures 1 to 5 As shown, the energy storage system 102 is also used to adjust the frequency of the output AC power to a frequency threshold range when the first condition is not met. The photovoltaic power connection unit 103 is also used to control the photovoltaic power connection unit 103 to connect the first branch when the frequency of the AC power output by the energy storage system 102 is detected to be within the frequency threshold range.

[0067] Specifically, when the energy storage system 102 detects that the first condition is not met, it can adjust the frequency of the output AC power to within the frequency threshold range to cooperate with the photovoltaic power connection unit 103. When the photovoltaic power connection unit 103 detects that the frequency of the AC power output by the energy storage system 102 is within the frequency threshold range, it controls the photovoltaic power connection unit 103 to connect the first branch to connect the photovoltaic power generation system 101 into the photovoltaic energy storage system 10.

[0068] In some embodiments, a specific implementation method is provided for controlling grid connection via the grid-connected / off-grid switching unit 104. For example... Figures 2 to 5 As shown, the on-grid / off-grid switching unit 104 is used for: When the first power switch K1 is open and the power grid 20 is detected to be energized, the frequency and phase of the AC power output by the energy storage system 102 are detected. When the frequency and phase of the AC power output by the energy storage system 102 are detected to be consistent with the frequency and phase of the AC power output by the grid 20, the first power switch K1 is closed to connect the photovoltaic power generation system 101 and the energy storage system 102 to the grid.

[0069] Specifically, during the process of switching the photovoltaic-storage system 10 from off-grid to grid-connected, the grid-connected / off-grid switching unit 104 can detect the frequency and phase of the AC power output by the energy storage system 102 when it detects that the first power switch K1 is open and the grid 20 is energized. The energy storage system 102 can also adjust the frequency and phase of the output AC power until the grid-connected / off-grid switching unit 104 detects that the frequency and phase of the AC power output by the energy storage system 102 are consistent with the frequency and phase of the AC power of the grid 20. Then, it controls the first power switch K1 to close so that the photovoltaic power generation system 101 and the energy storage system 102 are connected to the grid, avoiding grid oscillations or impacts on the photovoltaic-storage system 10.

[0070] Optionally, after the energy storage system 102 is powered on by the grid 20, it can reduce its output power (the output power is used to supply power to the load normally) in order to connect to the grid smoothly.

[0071] The following example illustrates the optical energy storage system provided in an embodiment of the present invention. Figure 6 This is the sixth schematic diagram of the structure of the photovoltaic energy storage system provided by the present invention, as shown below. Figure 6 As shown, in Figure 1 Based on the existing design, dashed lines represent communication connections, while the remaining solid lines represent power connections. It should be noted that in this embodiment of the invention, the energy storage system 102 indirectly controls the photovoltaic power connection unit 103 to disconnect or connect via frequency modulation, eliminating the need for additional communication lines to control the photovoltaic power connection unit 103 and thus saving on communication lines.

[0072] like Figures 1 to 6 As shown, the main feature of this embodiment of the invention is the addition of a photovoltaic power connection unit 103 to the photovoltaic energy storage system 10. This unit detects the change in the AC frequency of the system to control the opening or closing of the switch, thereby achieving the purpose of disconnecting the photovoltaic inverter.

[0073] like Figure 6 As shown, the descriptions of each part of the photovoltaic energy storage system 10 are as follows: 1) The photovoltaic inverter of the photovoltaic power generation system 101 is connected to the photovoltaic power connection unit 103, and the photovoltaic power connection unit 103 is connected to the grid-connected and off-grid switching unit 104. The energy storage system 102 is connected to the grid-connected and off-grid switching unit 104 for power and communication, and the photovoltaic power connection unit 103 is connected to the photovoltaic-storage system management unit 105 for communication.

[0074] 2) The photovoltaic power connection unit 105 sets a frequency threshold range for the photovoltaic power connection unit 103 via communication. The photovoltaic power connection unit 103 detects the frequency of the AC bus. If the frequency exceeds the set frequency threshold range, it controls the second power switch K2 to open. If the frequency of the AC bus is within the threshold range, it controls the second power switch K2 to close.

[0075] 3) When the grid 20 is normal and the photovoltaic-storage system 10 is running on the grid, the first power switch K1 of the off-grid switching unit 104 is closed, the photovoltaic-storage system 10 is normally connected to the grid, the second power switch K2 of the photovoltaic power connection unit 103 is closed, the photovoltaic inverter is running normally on the grid, and the energy storage system 102 is running normally on the grid.

[0076] 4) When the grid 20 loses power, the first power switch K1 of the grid-connected and off-grid switching unit 104 is opened, and the energy storage system 102 switches from grid-connected mode to off-grid mode. At the same time, the AC output frequency is adjusted to increase or decrease the AC bus frequency. After the photovoltaic power connection unit 103 detects that the AC output frequency of the energy storage system 102 exceeds the preset frequency threshold, it disconnects the second power switch K2 and disconnects the photovoltaic inverter.

[0077] 5) When the power grid 20 is restored, the energy storage system 102 adjusts the voltage phase and frequency to be consistent with the power grid 20, the second power switch K2 of the photovoltaic power connection unit 103 is closed, the photovoltaic inverter starts to operate, and at the same time the first power switch K1 of the grid-connected and off-grid switching unit 104 is closed to connect the photovoltaic and energy storage system 10 to the grid.

[0078] like Figure 4 As shown, the relevant descriptions of the photovoltaic power connection unit are as follows: <1> The photovoltaic power connection unit 103 uses operational amplifier A to detect and sample the AC bus waveform, and adjusts the rated 220Vac AC voltage waveform to a suitable voltage range.

[0079] <2> The adjusted AC sine wave (first voltage) is fed into the input of comparator B and compared with 0V, outputting a square wave signal (second voltage). During the positive half-cycle of the AC sine wave, the comparator outputs a high level; during the negative half-cycle of the AC sine wave, the comparator outputs a low level.

[0080] <3> The square wave signal output by comparator B is sent to the MCU. The MCU detects the square wave and calculates the duration of the high and low levels to obtain the AC voltage frequency value.

[0081] <4> When the detected frequency value exceeds the set threshold (too high or too low), the MCU controls the second power switch K2 to open, disconnecting the photovoltaic inverter from the AC bus, thus achieving the purpose of bypassing the photovoltaic inverter.

[0082] The optical energy storage system provided in this embodiment of the invention has at least the following beneficial effects: 1) High reliability: Different photovoltaic inverters can be controlled and disconnected uniformly, eliminating compatibility issues between different photovoltaic inverters. No communication method is required; the equipment detects AC frequency changes and autonomously determines whether to disconnect the photovoltaic inverter.

[0083] 2) High feasibility: No need to coordinate the frequency control of the photovoltaic inverter; the photovoltaic inverter is actually hard-cut off by power.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic energy storage system, characterized in that, include: A photovoltaic power generation system, an energy storage system, and a photovoltaic power connection unit are provided. The photovoltaic power generation system and the photovoltaic power connection unit are connected in series to form a first branch. The energy storage system is connected to a second branch, and the second branch is connected to the first branch. The energy storage system is used to adjust the frequency of the output AC power to exceed a preset frequency threshold range when a first condition is detected; wherein, the first condition is related to the photovoltaic energy storage system being in an off-grid state; The photovoltaic power connection unit is used to control the photovoltaic power connection unit to disconnect the first branch when it is detected that the frequency of the AC power output by the energy storage system exceeds the frequency threshold range.

2. The photovoltaic energy storage system according to claim 1, characterized in that, The photovoltaic-storage system also includes a grid-connected / off-grid switching unit, wherein the first branch and the second branch are connected in parallel to the power grid through a first power switch in the grid-connected / off-grid switching unit, and the first branch and the second branch are connected in parallel to the load; The first condition being met includes any one of the following: The first power switch is in the off state; The first power switch is in the off state, and the electrical energy required by the load is less than a first value; The first power switch is in the off state, and the electrical energy required by the energy storage system is less than the second value; The first power switch is in the off state, the electrical energy required by the load is less than a first value, and the electrical energy required by the energy storage system is less than a second value.

3. The photovoltaic storage system according to claim 1 or 2, characterized in that, The photovoltaic power connection unit includes: A second power switch is connected to the first branch; A voltage conversion module is used to convert the collected AC power output from the energy storage system into a first voltage within a preset voltage range; A waveform conversion module is used to convert the first voltage, which is a sine wave, into a second voltage, which is a square wave. A microcontroller is configured to determine the frequency of the AC power output by the energy storage system based on the second voltage, and to control the second power switch to disconnect the first branch when the frequency of the AC power output by the energy storage system exceeds the frequency threshold range.

4. The photovoltaic energy storage system according to claim 3, characterized in that, The voltage conversion module includes an operational amplifier. The two input terminals of the operational amplifier are used to collect the AC power output by the energy storage system. The output terminal of the operational amplifier is connected to the input terminal of the waveform conversion module and is used to output the first voltage. Alternatively, the voltage conversion module includes a transformer, the two input terminals of which are used to collect the AC power output by the energy storage system, and the output terminal of the transformer is connected to the input terminal of the waveform conversion module to output the first voltage.

5. The photovoltaic energy storage system according to claim 3, characterized in that, The waveform conversion module includes a comparator, one input terminal of which is connected to the output terminal of the voltage conversion module, and the other input terminal is grounded. The output terminal of the comparator is connected to the input terminal of the microcontroller. Alternatively, the waveform conversion module may include an optocoupler, the input of which is connected to the output of the voltage conversion module, and the output of which is connected to the input of the microcontroller.

6. The photovoltaic energy storage system according to claim 3, characterized in that, The microcontroller is specifically used for: Calculate the first duration of the high level in the second voltage and the second duration of the low level in the second voltage, respectively; Based on the first time and the second time, the frequency of the AC power output by the energy storage system is determined.

7. The photovoltaic energy storage system according to claim 3, characterized in that, The photovoltaic-storage system also includes a photovoltaic-storage system management unit, which is connected to the microcontroller in the photovoltaic power connection unit; The optical storage system management unit is used to output the adjusted frequency threshold range to the microcontroller; The microcontroller is specifically used to control the second power switch to close or open based on the adjusted frequency threshold range.

8. The photovoltaic energy storage system according to claim 1 or 2, characterized in that, The photovoltaic power generation system includes at least one photovoltaic power generation module and at least one corresponding photovoltaic inverter; At least one of the photovoltaic power generation components is connected to the photovoltaic power connection unit via at least one corresponding photovoltaic inverter.

9. The photovoltaic energy storage system according to claim 1 or 2, characterized in that, The energy storage system is also used to adjust the frequency of the output AC power to the frequency threshold range when the first condition is not met. The photovoltaic power connection unit is also used to control the photovoltaic power connection unit to connect the first branch when the frequency of the AC power output by the energy storage system is detected to be within the frequency threshold range.

10. The photovoltaic energy storage system according to claim 2, characterized in that, The on-grid / off-grid switching unit is used for: When the first power switch is open and the power grid is detected to be energized, the frequency and phase of the AC power output by the energy storage system are detected. If the frequency and phase of the AC power output by the energy storage system are detected to be consistent with the frequency and phase of the AC power output by the power grid, the first power switch is controlled to close so that the photovoltaic power generation system and the energy storage system are connected to the grid.

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