Method for cutting battery assembly, energy storage system and electronic device

Abstract

The application relates to a battery assembly cutting-off method, an energy storage system and electronic equipment. The battery assembly cutting-off method configures active power of the energy storage system and power generation power of a photovoltaic assembly to be equal, makes average power of a battery assembly zero, and executes cutting-off at a moment when second harmonic current of the battery assembly is zero, realizes safe cutting-off of the battery assembly, effectively avoids switch arc damage, prolongs switch life, and simultaneously completes cutting-off without shutdown, and avoids energy waste.

Description

Technical Field

[0001] This application relates to the field of energy storage system technology, and in particular to a method for cutting battery modules, an energy storage system, and an electronic device. Background Technology

[0002] In energy storage systems comprising power generation components and battery modules, the battery modules need to be disconnected from the system when they are overcharged, over-discharged, or under other special conditions. In related technologies, direct disconnection poses a risk of arcing and damaging the switches, while shutdown and restart result in energy waste. Therefore, how to safely disconnect the battery modules has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0003] To address or partially address the problems existing in related technologies, this application provides a method for cutting off battery components, an energy storage system, and an electronic device, which can achieve safe cutting off of battery components.

[0004] The first aspect of this application provides a method for cutting off a battery assembly, comprising: In response to a disconnection command from the battery modules in the energy storage system, the active power of the grid-connected energy storage system is configured to be equal to the power generation of the photovoltaic modules in the energy storage system; wherein the battery modules and the photovoltaic modules are connected in parallel and then connected to the AC grid via an inverter; When the second harmonic current of the battery module is determined to be zero, the switching component in the energy storage system is controlled to turn off to disconnect the battery module.

[0005] Furthermore, the method for disconnecting the battery module described above, wherein configuring the active power of the energy storage system connected to the grid to be equal to the power generation of the photovoltaic modules in the energy storage system, includes: Adjust the active power output of the inverter to make the active power of the energy storage system connected to the grid equal to the power generation of the photovoltaic modules in the energy storage system.

[0006] Furthermore, in the above-described method for disconnecting the battery module, adjusting the active power of the energy storage system connected to the grid to be equal to the power generation of the photovoltaic modules in the energy storage system includes: The active power of the energy storage system connected to the grid is adjusted to be equal to the average power of the photovoltaic modules in the energy storage system.

[0007] Furthermore, in the above-described method for cutting off the battery assembly, the step of determining the moment when the second harmonic current of the battery assembly is zero includes: Based on the correspondence between the second harmonic current of the battery module and the power factor angle and phase angle, the moment when the second harmonic current is zero is calculated.

[0008] Furthermore, the above-described method for disconnecting the battery module, wherein controlling the switching component in the energy storage system to turn off to disconnect the battery module at the moment when the second harmonic current of the battery module is zero, includes: The timing of the turn-off signal is determined based on the switching delay time of the switching assembly and the zero-crossing sequence of the second harmonic current; the zero-crossing sequence is a sequence of times when the second harmonic current is zero. The shutdown signal is sent to the switching assembly at the sending time to disconnect the battery assembly when the second harmonic current is zero.

[0009] Furthermore, in the above-described method for cutting off the battery assembly, determining the transmission time of the turn-off signal based on the switching delay time of the switching assembly and the zero-crossing sequence of the second harmonic current includes: The transmission time of the shutdown signal is determined based on the first zero-crossing point selected from the zero-crossing sequence that is later than the current time and whose time difference with the current time is greater than the delay time.

[0010] Furthermore, in the above-described method for disconnecting the battery assembly, the switching assembly includes a switching transistor and / or a relay.

[0011] A second aspect of this application provides an energy storage system, including: photovoltaic modules, battery modules, inverters, switching modules, and controllers; The battery module and the photovoltaic module are connected in parallel and then connected to the AC power grid via the inverter; wherein, the battery module is electrically connected to the inverter through the switching assembly; The switching assembly is electrically connected to the controller; The controller is configured to, in response to the disconnection command of the battery module, set the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module; determine the moment when the second harmonic current of the battery module is zero, and control the switching component to turn off the battery module to disconnect the battery module at the moment when the second harmonic current of the battery module is zero.

[0012] Furthermore, in the energy storage system described above, the inverter is communicatively connected to the controller; The controller is used to adjust the active power output of the inverter so that the active power of the energy storage system connected to the grid is equal to the power generation of the photovoltaic module.

[0013] A third aspect of this application provides an electronic device, comprising: Processor; and A memory that stores executable code, which, when executed by the processor, causes the processor to perform the method described above.

[0014] The battery module disconnection method provided in this application configures the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module, so that the average power of the battery module is zero, and performs disconnection when the second harmonic current of the battery module is zero. This achieves safe shutdown of the battery module, effectively avoids switch arc damage, extends switch life, and completes disconnection without shutdown, thus avoiding energy waste.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0016] The above and other objects, features and advantages of this application will become more apparent from the following description of exemplary embodiments of this application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components.

[0017] Figure 1 This is a schematic diagram of a structure of an energy storage system shown in an embodiment of this application; Figure 2 This is another structural schematic diagram of the energy storage system shown in the embodiments of this application; Figure 3 This is a schematic flowchart illustrating the battery assembly cutting method according to an embodiment of this application; Figure 4 This is a phase diagram of a second harmonic current shown in an embodiment of this application; Figure 5 This is another phase diagram of the second harmonic current shown in the embodiments of this application; Figure 6 This is a schematic diagram of the structure of an electronic device shown in an embodiment of this application. Detailed Implementation

[0018] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0019] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0020] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0021] In an energy storage system that includes photovoltaic modules and battery modules, when the battery modules are overcharged, over-discharged, or in other abnormal states, the battery modules need to be disconnected from the energy storage system.

[0022] In related technologies, energy storage system shutdown methods include direct shutdown, shutdown followed by restart, and sensor detection of battery module current crossing zero. Direct shutdown places significant stress on the switching components. If a large current remains on the energy storage system side at the moment of shutdown, a violent arc will occur between the contacts of the switching components, severely shortening their lifespan and potentially causing safety accidents. Shutdown followed by restart results in energy waste, as the energy from the photovoltaic panels cannot be utilized, leading to further energy waste. Sensor detection of battery module current crossing zero relies on high-precision sensors. Traditionally, high-precision, high-frequency-response battery current sensors are added to capture the zero-crossing point to achieve low-current shutdown. However, this increases hardware costs, and the sensors may malfunction or be affected by noise interference, leading to misjudgments of the zero-crossing point and reduced reliability.

[0023] Therefore, how to safely disconnect battery components has become a technical problem that urgently needs to be solved by those skilled in the art.

[0024] To address the aforementioned issues, this application provides a method for disconnecting a battery module. By configuring the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module, the average power of the battery module becomes zero. Then, the disconnection is performed based on the zero-crossing moment of the second harmonic current, thereby achieving zero-current safe disconnection.

[0025] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0026] Figure 1 A schematic diagram of an energy storage system is shown. The system includes at least a controller 10, a battery module 11, an inverter 12, a photovoltaic module 13, and a switch assembly 14. The battery module 11 and the photovoltaic module 13 are connected in parallel and then connected to the AC power grid via the inverter 12. The photovoltaic module 13 is electrically connected to the inverter 12 via the switch assembly 14.

[0027] In some embodiments, the controller 10 is capable of communicating with at least the battery module 11, inverter 12, photovoltaic module 13, and switch assembly 14 via the target network 15. The controller 10 can adjust the power generation of the photovoltaic module 13 by sending commands to the photovoltaic module 13; it can adjust the grid-connected power of the energy storage system by sending commands to the inverter 12; and it can control the switch assembly 14 to be turned on or off by sending commands to the switch assembly 14, wherein when the switch assembly 14 is turned on, the battery module 11 is connected to the DC bus, and when the switch assembly 14 is turned off, the battery module 11 is disconnected.

[0028] The target network 15 can be any type of network. For example, the target network 15 can be a single network, which can be further subdivided into multiple sub-networks. Specifically, the target network 15 or the multiple sub-networks contained in the target network 15 can be at least one of wired networks, cellular mobile networks (e.g., 2G, 3G, 4G or 5G), ZIGBEE, Wi-Fi, and Bluetooth, or at least one of these networks in any combination with other networks.

[0029] The controller 10 can be an electronic device with certain computing capabilities. It may have a data acquisition interface, a PWM signal output interface, a communication interface, a processor core, and memory. Alternatively, the controller 10 can refer to software running within the electronic device. The controller 10 can also be a distributed processor, a system with multiple processor cores, memory, communication modules, etc., operating collaboratively. Alternatively, the controller 10 can be a processor cluster formed by several processors. Furthermore, with the development of science and technology, the controller 10 can also be a new technical means capable of realizing the corresponding functions of the embodiments described in the specification, such as a control unit based on a neural network processing unit or a field-programmable gate array.

[0030] Battery assembly 11 refers to a DC power supply unit in an energy storage system that is used to store electrical energy and can be repeatedly charged and discharged. Battery assembly 11 may include one or more battery modules connected in series or in parallel, and each battery module contains multiple cells.

[0031] Inverter 12 refers to a DC / AC (Direct Current to Alternating Current) inverter, specifically a power conversion device connected between the DC bus and the AC grid. It is used to convert DC power on the DC bus into AC power to feed into the AC grid, or to convert AC power from the AC grid into DC power to supply the DC bus. Inverter 12 typically consists of power switching devices, filters, and drive circuitry.

[0032] Photovoltaic module 13 refers to a power generation device that converts solar energy into direct current (DC) electricity. Photovoltaic module 13 is composed of multiple photovoltaic cells connected in series or parallel, and its power generation varies with light intensity and temperature. When there is sufficient sunlight, the DC power generated by photovoltaic module 13 powers inverter 12 or charges battery module 11 via the DC bus; when there is insufficient sunlight, the power output of photovoltaic module 13 decreases or becomes zero.

[0033] Figure 1 The illustrated embodiment also includes a DC-DC converter 17, a battery-side capacitor 18, and a bus capacitor 19. The specific connection methods and installation locations can be found in [reference needed]. Figure 1 This embodiment will not be described in detail.

[0034] In the above embodiment, the controller 10 can detect the operating state of the battery module 11. When the battery module 11 is overcharged, over-discharged, or in other abnormal states, it generates a cut-off command. In response to the cut-off command, the controller 10 adjusts the photovoltaic module 13 or the inverter 12 to configure the active power of the energy storage system connected to the grid to be equal to the power generation of the photovoltaic module 13. Then, it determines the moment when the second harmonic current of the battery module 11 is zero, and controls the switching component 14 to cut off the battery module 11 at the moment when the second harmonic current of the battery module 11 is zero, thereby achieving zero-current safe cut-off.

[0035] In some other embodiments, the controller 10 is communicatively connected to the inverter 12. When the controller 10 configures the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module 13 in response to the disconnection command, it is specifically used to adjust the active power output of the inverter 12 to adjust the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module 13.

[0036] In the above embodiments, the controller 10 configures the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module 13, so that the average power of the battery module 11 is zero, and performs the disconnection when the second harmonic current of the battery module 11 is zero, thereby realizing the safe shutdown of the battery module, effectively avoiding the damage of the switching arc, and completing the disconnection without stopping the machine, thus avoiding energy waste.

[0037] Based on the same inventive concept, an exemplary embodiment of this specification provides a method for cutting a battery assembly. The description is based on an example of this method applied to an electronic device, which may specifically be a device with communication and computing functions, such as a controller as described in the above embodiments. (Refer to...) Figure 2 As shown, the method includes: S101. In response to the disconnection command of the battery module in the energy storage system, configure the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module in the energy storage system.

[0038] As described in the above embodiments, the battery module and photovoltaic module are connected in parallel and then connected to the AC power grid via an inverter.

[0039] The aforementioned disconnection command refers to the control command generated to trigger the disconnection process when an overcharge, over-discharge, abnormal temperature, or other fault that requires the battery module to be isolated from the energy storage system is detected.

[0040] Upon receiving the aforementioned disconnection command, the active power of the energy storage system connected to the grid can be adjusted based on the command, and / or the power generation of the photovoltaic modules in the energy storage system can be adjusted to make the active power of the energy storage system connected to the grid equal to the power generation of the photovoltaic modules in the energy storage system. In some embodiments, the active power of the energy storage system connected to the grid can be adjusted by adjusting the inverter in the energy storage system; the power generation of the photovoltaic modules in the energy storage system can be adjusted by adjusting the photovoltaic modules in the energy storage system.

[0041] In some embodiments, the active power of the grid-connected energy storage system is equal to the power generated by the photovoltaic modules in the energy storage system, which means that the average power of the active power and the power generated is equal.

[0042] When the active power of the energy storage system connected to the grid equals the power generated by the photovoltaic modules in the energy storage system, the average power output of the battery modules is zero, and the DC component of the battery module's current is adjusted to zero. At this time, the current of the battery module only contains the second harmonic current component. This setting provides the prerequisite for subsequently disconnecting the battery modules at the zero current moment.

[0043] S102. Determine the moment when the second harmonic current of the battery module is zero. At the moment when the second harmonic current of the battery module is zero, control the switching components in the energy storage system to turn off to disconnect the battery module.

[0044] Once the active power of the grid-connected energy storage system is equal to the power generation of the photovoltaic modules in the energy storage system, the moment when the second harmonic current of the battery module is zero can be further calculated, so that the battery module can be removed from the energy storage system at the moment when the second harmonic current of the battery module is zero.

[0045] This configuration, by setting the active power of the energy storage system connected to the grid to be equal to the power generation of the photovoltaic modules, makes the average power of the battery modules zero, and performs the disconnection when the second harmonic current of the battery modules is zero, thus achieving safe shutdown of the battery modules, effectively avoiding switch arc damage, extending switch life, completing the disconnection without shutdown, avoiding energy waste, and eliminating the need for operation.

[0046] More specifically, for ease of understanding, this embodiment analyzes the battery power of the battery modules in the energy storage system, the power generation of the photovoltaic modules, and the active power of the energy storage system connected to the grid as follows: Figure 3 The diagram shown is a simplified representation of an energy storage system, which includes a photovoltaic module 13, a battery module 11, and an inverter 12, all of which are connected to a DC bus.

[0047] Figure 3 In the diagram, the arrow indicates the positive direction. In this embodiment, the DC bus voltage is considered constant, and the second harmonic ripple, i.e., the second harmonic current in the above embodiment, is borne by the battery module 11 side. Therefore, the power generation P... pv With the instantaneous power p of the battery module bat The sum of (t) equals the instantaneous power p of the energy storage system connected to the grid. grid (t), i.e., P pv +p bat (t)=p grid (t), we can obtain: p bat (t)=p grid (t)-P pv (1) p grid (t)=v g (t)×i g (t), v g (t)=√2V g sin(ωt), I g (t)=√2I g sin(ωt-φ), where v g (t) represents the instantaneous value of the grid-connected voltage of the energy storage system, i g (t) represents the instantaneous value of the grid-connected current of the energy storage system, ω represents the angular frequency of the grid-connected voltage of the energy storage system, t represents the current moment, and φ represents the power factor angle.

[0048] Therefore, we can conclude that: p grid (t)=V g I g cosφ-V g I g cos(2ωt-φ)(2) It can be seen that the instantaneous power of the energy storage system connected to the grid is composed of a constant component V. g I g cosφ and a second harmonic current component V g I g It is composed of cos(2ωt-φ).

[0049] Substituting formula (2) into formula (1), the instantaneous power of the battery module is: p bat (t)=p grid (t)-P pv =(V g I g cosφ-P pv )-V g I g cos(2ωt-φ) V g I g cosφ-P pv P represents the DC component bat_dc V g I g cos(2ωt-φ) represents the AC component p bat_ac (t).

[0050] The current i of the battery module bat (t) is determined by its power and terminal voltage. The terminal voltage of the battery module changes slowly; in this embodiment, it is considered constant. Assume the terminal voltage of the battery module is V. bat ,but: i bat (t)=P bat (t) / V bat (3) i bat (t)=(V g I g cosφ-P pv ) / V bat -V g I g cos(2ωt-φ) / V bat (4) Therefore, it can be determined that the current of the battery module also consists of a DC component (V). g I g cosφ-Ppv ) / V bat and the second harmonic current component V g I g cos(2ωt-φ) / V bat composition.

[0051] As can be seen from formula (4), when the active power of the energy storage system connected to the grid is equal to the power generation of the photovoltaic modules in the energy storage system, the DC component of the battery module current is adjusted to zero, and the current is entirely a second harmonic current: i bat (t)=-V g I g cos(2ωt-φ) / V bat (5) Based on the above formula (5), the precise moment when the second harmonic current crosses zero can be calculated, and this moment is affected by the power factor angle φ.

[0052] Therefore, the steps in the above embodiments to determine the moment when the second harmonic current of the battery module is zero may specifically include the following steps: calculating the moment when the second harmonic current is zero based on the correspondence between the second harmonic current of the battery module and the power factor angle and phase angle.

[0053] In the embodiments of this application, the moment when the second harmonic current is zero can be calculated according to the above formula (5), that is, according to the correspondence between the second harmonic current of the battery module and the power factor angle φ and the phase angle ωt of the AC power grid.

[0054] Specifically, i bat (t)=-V g I g cos(2ωt-φ) / V bat When the condition 2ωt-φ=π / 2+kπ is met, and k is any integer, the second harmonic current is 0. Based on this condition, the zero-crossing sequence of the second harmonic current can be calculated, and a selected moment can be chosen as the cutoff moment. At this moment, the switching component is controlled to open, thus completing the disconnection of the battery assembly.

[0055] In other words, the instantaneous current of the battery module will return to zero at a specific phase. This zero-point moment is entirely determined by known quantities ωt and φ, and can be calculated in real time without the need for any current sensors.

[0056] This configuration allows for the precise determination of the zero-crossing moment of the second harmonic current through calculation and enables the interruption of the current, achieving zero-current interruption without the need for a current sensor.

[0057] As an optional implementation, the steps of the above embodiments configure the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic modules in the energy storage system. Specifically, the steps include: adjusting the active power output of the inverter to adjust the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic modules in the energy storage system.

[0058] Specifically, upon receiving a disconnection command, in this embodiment, the power generation of the photovoltaic modules remains unchanged, while the active power of the energy storage system connected to the grid is adjusted to achieve the goal of adjusting the active power of the energy storage system connected to the grid to be equal to the power generation of the photovoltaic modules in the energy storage system. In some embodiments, the active power output of the inverter in the energy storage system can be adjusted to achieve the same goal as the power generation of the photovoltaic modules in the energy storage system.

[0059] It should be noted that the adjustment rate needs to balance system stability and response speed. For example, it can be adjusted at a certain slope, but this embodiment does not impose such a limitation. After the adjustment is completed, the average output power of the battery module is zero.

[0060] With this configuration, this embodiment achieves power balance by adjusting the active power of the energy storage system connected to the grid, without changing the operating status of the photovoltaic modules. The photovoltaic power generation is always kept at its maximum, thus avoiding energy waste.

[0061] As an optional implementation, the steps of the above embodiments to adjust the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic modules in the energy storage system include: adjusting the average power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic modules in the energy storage system.

[0062] Specifically, because the instantaneous power of the energy storage system connected to the grid includes second harmonic current, the instantaneous values ​​of the grid-connected active power and the photovoltaic power generation cannot be exactly equal at every moment. Therefore, in this embodiment, the average value of the grid-connected active power over one power frequency cycle is adjusted to be equal to the average value of the photovoltaic module's power generation.

[0063] By adjusting the active power output of the inverter, the average active power of the grid-connected energy storage system can be made equal to the average power generated by the photovoltaic modules, thus making the average output power of the battery modules zero. At this time, the DC component of the battery module current is adjusted to zero, and the current is entirely a second harmonic current.

[0064] This configuration ensures that the DC component of the battery current is zero, providing a prerequisite for subsequent disconnection at the zero-crossing moment of the second harmonic current.

[0065] As an optional implementation, the steps of the above embodiments, which control the switching component in the energy storage system to turn off the battery component when the second harmonic current of the battery component is zero, specifically include the following steps: determining the transmission time of the turn-off signal based on the switching delay time of the switching component and the zero-crossing sequence of the second harmonic current; the zero-crossing sequence is a sequence composed of the times when the second harmonic current is zero; and sending the turn-off signal to the switching component at the transmission time to cut off the battery component when the second harmonic current is zero.

[0066] The above zero-crossing sequence is a sequence of moments when the second harmonic current is zero.

[0067] Specifically, according to the above formula (5), when the condition 2ωt-φ=π / 2+kπ is satisfied, and k is any integer, the second harmonic current is zero. After solving 2ωt-φ=π / 2+kπ, a series of discrete time points can be obtained. These time points are arranged in chronological order, forming a zero-crossing sequence.

[0068] In practical systems, there is a certain switching delay between the receipt of a turn-off signal and the actual physical disconnection of the contacts by the switching component. Different types of switching components have different switching delays; for example, the switching delay of a transistor is short, even negligible, while the switching delay of a relay is relatively long. To ensure that physical disconnection can be completed when the second harmonic current is zero, the switching delay of the switching component needs to be considered.

[0069] Specifically, in the embodiments of this application, the first moment later than the current moment is selected from the zero-crossing sequence as the first cut-off moment. The time difference between the first cut-off moment and the current moment is compared to see if it is greater than the switching delay time of the switching component. If the time difference is greater than or equal to the switching delay time of the switching component, it means that the switching component can complete the physical disconnection at the precise moment when the current crosses zero, and the first cut-off moment is determined as the cut-off moment of the switching component.

[0070] If the time difference is less than the switching delay time of the switching component, then the second time point later than the current time is selected from the zero-crossing sequence as the second cut-off time. The time difference between the second cut-off time and the current time is compared to see if it is greater than or equal to the switching delay time of the switching component. This process is repeated until a target cut-off time with a time difference greater than or equal to the switching delay time is found. The target cut-off time is then determined as the cut-off time of the switching component to ensure that the switching component can physically disconnect at the precise moment when the current crosses zero.

[0071] After determining the cut-off time of the switching component, the cut-off time minus the switching delay time of the switching component can be used as the time to send the turn-off signal. Sending the turn-off signal to the switching component at this time ensures that the switching component physically disconnects at the precise moment when the current is zero.

[0072] It should be noted that the switching delay time can be obtained by consulting the device manual or by experimental calibration, and this embodiment does not limit it.

[0073] This configuration provides multiple precise zero-current moments for the cut-off operation through the zero-crossing sequence, allowing for flexible selection of the optimal cut-off timing based on the current time and switching delay time. This avoids reliance on real-time sampling by the current sensor while ensuring the accuracy of zero current at the cut-off moment.

[0074] As an optional implementation, the steps of the above embodiments determine the transmission time of the turn-off signal based on the switching delay time of the switching component used to cut off the battery module in the energy storage system and the zero-crossing sequence of the second harmonic current. Specifically, the steps include: determining the transmission time of the turn-off signal based on the first zero-crossing point selected from the zero-crossing sequence that is later than the current time and has a time difference greater than the delay time.

[0075] In the embodiments of this application, zero-crossing points later than the current time can be selected from the zero-crossing point sequence as candidate zero-crossing points. Then, for each candidate zero-crossing point, the time difference between it and the current time is calculated. Candidate zero-crossing points with a time difference greater than the switching delay time are selected as valid candidates. The earliest one in time from the valid candidates is selected as the cut-off time of the battery module.

[0076] After determining the cut-off time of the switching component, the cut-off time minus the switching delay time of the switching component can be used as the time to send the turn-off signal. Sending the turn-off signal to the switching component at this time ensures that the switching component physically disconnects at the precise moment when the current is zero.

[0077] For example, the current time is 0, the zero-crossing sequence is t1=5ms, t2=15ms, t3=25ms, and the switching delay time is 6ms.

[0078] Zero-crossing points t2 and t3, which are later than the current time, are selected as candidate zero-crossing points. Since the time difference between each candidate zero-crossing point and the current time is greater than the switching delay time, the earliest t2 is selected as the battery module's cut-off time. The calculated cut-off signal transmission time is 9ms, obtained by subtracting the switching delay time from t2. Therefore, a cut-off signal needs to be sent to the switching component at 9ms to ensure that the switching component physically disconnects at the precise moment when the current is zero.

[0079] This configuration ensures sufficient time to send a turn-off signal to the switching component in advance, enabling the component to physically disconnect at the precise moment when the second harmonic current is zero. It avoids the problem of failing to complete the cut-off at the target zero-crossing point due to insufficient delay time, while fully utilizing the earliest available zero-crossing point to shorten the waiting time for the cut-off operation, thus improving the timeliness of the cut-off response.

[0080] As an alternative implementation, the switching assembly includes a switching transistor and / or a relay.

[0081] The switching components used to disconnect the battery modules in the energy storage system can be switching transistors, such as bidirectional switches composed of metal-oxide-semiconductor field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs). This implementation is not limited to these components, and mechanical switches such as relays can also be used.

[0082] Switching transistors have a faster cut-off speed and negligible delay time, enabling them to cut off more precisely at the calculated zero-crossing moment. Relays, on the other hand, have a slower cut-off speed and a certain degree of delay time dispersion. When using them, it is necessary to determine their delay time through the device manual or data calibration and compensate for it in the software, but this can save costs.

[0083] With this configuration, this embodiment is compatible with the characteristics of different types of switching components, and adopts corresponding compensation strategies based on the actual delay characteristics of the selected switching components, thereby improving the applicability and flexibility of the solution.

[0084] Furthermore, it should be noted that the above formula (5) is based on the condition that the DC bus voltage is constant. In this case, the current ripple of the battery module is not related to the size of the capacitor on the inverter side, but only to the instantaneous power between the photovoltaic module, the battery module, and the grid. bat (t)∝cos(2ωt-φ).

[0085] In practical applications, the formula for the second harmonic current will change due to factors such as the impedance of the battery module itself, the capacitance of the DC-side bus, and the different control methods of the DC / DC converter. Its amplitude is ibat(t)∝cos(2ωt-φ-θ), where θ is the phase angle error that may occur during the actual operation of the energy storage system. When the value of θ is small and negligible, ibat(t) can still be used. bat (t)=-V g I g cos(2ωt-φ) / V batWhen the value of θ is large, the phase angle error θ in this energy storage system needs to be calculated based on the actual situation for compensation.

[0086] The value of the phase angle error θ can be calculated through experimental calibration and other methods, and this embodiment does not limit it.

[0087] In one specific embodiment, the energy storage system operates at unity power factor on the grid-connected side, where the power factor angle φ = 0. The active power of the grid-connected energy storage system is 200W, and the power generation of the photovoltaic modules is 400W.

[0088] Upon receiving a disconnection command from the battery module, an active power adjustment command is sent to the DC / AC inverter to adjust the active power from 200W to 400W, so that the active power of the energy storage system connected to the grid is equal to the power generation of the photovoltaic module.

[0089] At unity power factor, the power factor angle φ = 0. When the condition 2ωt = π / 2 + kπ, where k is any integer, i.e., ωt = π / 4 + kπ / 2, where k is any integer, the second harmonic current of the battery module is zero. Figure 4 The diagram shows the phase diagram of the second harmonic current in the current scenario.

[0090] Figure 4 In the diagram, the horizontal axis represents the phase angle ωt of the AC power grid, the vertical axis represents the amplitude, and the blue curve represents the instantaneous value v of the grid-connected voltage of the energy storage system. g (t), where the red curve represents the instantaneous value i of the grid-connected current of the energy storage system. g (t), the black curve represents the current of the battery module after the active power of the grid-connected energy storage system is configured to be equal to the power generation of the photovoltaic modules in the energy storage system. At this time, the DC component of the current in the battery module is zero, and the current is entirely a second harmonic current. Figure 4 As shown, if the current time t=0, the nearest time is selected from the zero-crossing sequence, that is, when the grid phase is π / 4, as the cut-off time. A turn-off signal is sent to the switching component according to the cut-off time to complete the cut-off of the battery component.

[0091] In other embodiments, the battery module disconnection method can be applied to non-unity power factor scenarios. The grid-connected energy storage system has an active power of 200W, a reactive power of 300Var, and a photovoltaic module power generation capacity of 400W.

[0092] Upon receiving a disconnection command from the battery module, an active power adjustment command is sent to the DC / AC inverter to adjust the active power from 200W to 400W, so that the active power of the energy storage system connected to the grid is equal to the power generation of the photovoltaic module.

[0093] Based on the grid-connected active power of the energy storage system being 400W and reactive power being 300Var, the apparent power is calculated to be 500VA. The power factor cosφ = active power / apparent power = 400 / 500 = 0.8, and the power factor angle φ = 0.205π. When the condition 2ωt = π / 2 + kπ, where k is any integer, i.e., ωt = π / 4 + kπ / 2, where k is any integer, substituting φ = 0.205π, we get ωt = π / 4 + 0.1025π + kπ / 2, where k is any integer. In this case, the second harmonic current of the battery module is zero. Figure 5 The diagram shows the phase diagram of the second harmonic current in the current scenario.

[0094] Figure 5 In the diagram, the horizontal axis represents the phase angle ωt of the AC grid, and the vertical axis represents the amplitude. The blue curve represents the instantaneous value of the grid-connected voltage of the energy storage system, vg(t); the red curve represents the instantaneous value of the grid-connected current of the energy storage system, ig(t); and the black curve represents the current of the battery module after the active power of the grid-connected energy storage system is configured to be equal to the power generation of the photovoltaic modules in the energy storage system. At this time, the DC component of the current in the battery module is zero, and the current is entirely a second harmonic current. Figure 5 As shown, if the current time t=0, the nearest time from the zero-crossing sequence is selected, i.e., when the grid phase is π / 4+0.1025π, as the cut-off time. A turn-off signal is sent to the switching component based on the cut-off time to complete the disconnection of the battery module.

[0095] Corresponding to the foregoing method embodiments, this application also provides an electronic device, a computer-readable storage medium, a computer program product, and corresponding embodiments.

[0096] Figure 6 This is a schematic diagram of the structure of an electronic device shown in an embodiment of this application.

[0097] See Figure 6 The electronic device includes a memory 200 and a processor 210.

[0098] The memory 200 is connected to the processor 210 and is used to store programs; Processor 210 is used to implement some or all of the methods described above by running programs stored in memory 200.

[0099] Specifically, the aforementioned electronic device may further include: a bus, a communication interface 220, an input device 230, and an output device 240.

[0100] The processor 210, memory 200, communication interface 220, input device 230, and output device 240 are interconnected via a bus. Among them: A bus can include a pathway for transmitting information between various components of a computer system.

[0101] The processor 210 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0102] Processor 210 may include a main processor, as well as a baseband chip, modem, etc.

[0103] Memory 200 may include various types of storage units, such as system memory, read-only memory (ROM), and permanent storage devices. ROM may store static data or instructions required by processor 210 or other modules of the computer. Permanent storage devices may be read-write storage devices. Permanent storage devices may be non-volatile storage devices that retain stored instructions and data even when the computer is powered off. In some embodiments, permanent storage devices employ mass storage devices (e.g., magnetic or optical disks, flash memory) as permanent storage devices. In other embodiments, permanent storage devices may be removable storage devices (e.g., floppy disks, optical drives). System memory may be a read-write storage device or a volatile read-write storage device, such as dynamic random access memory. System memory may store some or all of the instructions and data required by the processor during operation. Furthermore, memory 200 may include any combination of computer-readable storage media, including various types of semiconductor memory chips (e.g., DRAM, SRAM, SDRAM, flash memory, programmable read-only memory), and disks and / or optical disks may also be used. In some embodiments, memory 200 may include a removable storage device that is readable and / or writable, such as a laser disc (CD), a read-only digital multifunction optical disc (e.g., DVD-ROM, dual-layer DVD-ROM), a read-only Blu-ray disc, an ultra-high density optical disc, a flash memory card (e.g., SD card, mini SD card, Micro-SD card, etc.), a magnetic floppy disk, etc. Computer-readable storage media do not contain carrier waves or transient electronic signals transmitted wirelessly or via wired connections.

[0104] Input device 230 may include a device for receiving user input data and information, such as a keyboard, mouse, camera, scanner, light pen, voice input device, touch screen, pedometer, or gravity sensor.

[0105] Output device 240 may include devices that allow information to be output to a user, such as a display screen, printer, speaker, etc.

[0106] The communication interface 220 may include a device that uses any transceiver to communicate with other devices or communication networks, such as Ethernet, Radio Access Network (RAN), Wireless Local Area Network (WLAN), etc.

[0107] The processor 210 executes the program stored in the memory 200 and calls other devices, and can be used to implement some or all of the methods described above.

[0108] Furthermore, the method according to this application can also be implemented as a computer program product, which includes computer program code instructions for performing some or all of the steps in the method described above. Optionally, the computer program can be stored on a readable storage medium of a computer device or in the cloud; the processor of the computer device reads the computer program from the readable storage medium or the cloud.

[0109] Computer program products can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this application. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0110] The aforementioned computer program product can be implemented through hardware, software, or a combination thereof. In one optional embodiment, the computer program product is specifically embodied in a computer storage medium; in another optional embodiment, the computer program product is specifically embodied in a software product, such as a software development kit (SDK), etc.

[0111] Alternatively, this application may be implemented as a computer-readable storage medium (or a non-transitory machine-readable storage medium or a machine-readable storage medium) storing executable code (or computer program or computer instruction code) that, when executed by a processor of an electronic device (or server, etc.), causes the processor to perform part or all of the steps of the methods described above according to this application.

[0112] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may, for example, include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0113] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for cutting a battery assembly, characterized in that, include: In response to a disconnection command from the battery modules in the energy storage system, the active power of the grid-connected energy storage system is configured to be equal to the power generation of the photovoltaic modules in the energy storage system; wherein the battery modules and the photovoltaic modules are connected in parallel and then connected to the AC grid via an inverter; When the second harmonic current of the battery module is determined to be zero, the switching component in the energy storage system is controlled to turn off to disconnect the battery module.

2. The method for cutting the battery assembly according to claim 1, characterized in that, The step of configuring the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic modules in the energy storage system includes: Adjust the active power output of the inverter to make the active power of the energy storage system connected to the grid equal to the power generation of the photovoltaic modules in the energy storage system.

3. The method for cutting the battery assembly according to claim 2, characterized in that, Adjusting the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic modules in the energy storage system includes: The active power of the energy storage system connected to the grid is adjusted to be equal to the average power of the photovoltaic modules in the energy storage system.

4. The method for cutting the battery assembly according to claim 1, characterized in that, The moment when the second harmonic current of the battery assembly is determined to be zero includes: Based on the correspondence between the second harmonic current of the battery module and the power factor angle and phase angle, the moment when the second harmonic current is zero is calculated.

5. The method for cutting the battery assembly according to claim 1, characterized in that, The step of controlling the switching components in the energy storage system to turn off the battery module at the moment when the second harmonic current of the battery module is zero includes: The timing of the turn-off signal is determined based on the switching delay time of the switching assembly and the zero-crossing sequence of the second harmonic current; the zero-crossing sequence is a sequence of times when the second harmonic current is zero. The shutdown signal is sent to the switching assembly at the sending time to disconnect the battery assembly when the second harmonic current is zero.

6. The method for cutting the battery assembly according to claim 5, characterized in that, Determining the transmission time of the turn-off signal based on the switching delay time of the switching component and the zero-crossing sequence of the second harmonic current includes: The transmission time of the shutdown signal is determined based on the first zero-crossing point selected from the zero-crossing sequence that is later than the current time and whose time difference with the current time is greater than the delay time.

7. The method for cutting the battery assembly according to claim 1, characterized in that, The switching assembly includes a switching transistor and / or a relay.

8. An energy storage system, characterized in that, include: Photovoltaic modules, battery modules, inverters, switching components, and controllers; The battery module and the photovoltaic module are connected in parallel and then connected to the AC power grid via the inverter; wherein, the battery module is electrically connected to the inverter through the switching assembly; The switching assembly is electrically connected to the controller; The controller is configured to, in response to the disconnection command of the battery module, set the active power of the grid-connected energy storage system to be equal to the power generation of the photovoltaic module; determine the moment when the second harmonic current of the battery module is zero, and control the switching component to turn off the battery module at the moment when the second harmonic current of the battery module is zero.

9. The energy storage system according to claim 8, characterized in that, The inverter is communicatively connected to the controller; The controller is used to adjust the active power output of the inverter so that the active power of the energy storage system connected to the grid is equal to the power generation of the photovoltaic module.

10. An electronic device, characterized in that, include: processor; as well as A memory having executable code stored thereon, which, when executed by the processor, causes the processor to perform the method for cutting off the battery assembly as described in any one of claims 1-7.

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