Black start control method of energy storage system, energy storage system and readable storage medium

Abstract

The application discloses a black start control method of an energy storage system, an energy storage system and a readable storage medium, and relates to the technical field of energy storage system control. The method comprises the following steps: acquiring a historical database, wherein the historical database stores weather information at each time point in a preset time period and a black start success record; acquiring current system state information, including a weather forecast for the day and astronomical information calculated based on a geographical position and a date; dynamically determining an expected black start time for the day according to the weather forecast for the day, the astronomical information and the black start success record on similar days in the historical database; starting an energy storage inverter at the expected black start time to establish an alternating voltage, so that the micro inverter can detect and follow the start. Through dynamic adjustment of the start window, the problems of energy waste and low success rate caused by fixed start time are avoided, and the black start success rate and system robustness are improved.

Description

Technical Field

[0001] This invention relates to the field of energy storage system control technology, and more specifically to a black-start control method for an energy storage system, an energy storage system, and a readable storage medium. Background Technology

[0002] With the continuous development of photovoltaic power generation and energy storage technologies, the application mode of combining energy storage systems with microinverters is gradually increasing, especially in off-grid or weak grid scenarios. Energy storage systems often need to provide initial AC voltage to microinverters in the event of grid outages to enable the photovoltaic system to start up automatically. To this end, the industry typically adopts "black start" technology, in which the energy storage system actively establishes AC voltage, allowing the microinverter to detect the grid signal and enter the working state, thereby enabling the photovoltaic power generation system to resume operation.

[0003] In relevant technical solutions, black start typically relies on a pre-set start-up time and a reserved amount of remaining battery charge (SOC) to ensure that the microinverter can be powered to start at a specific time. However, existing technologies often employ a fixed-time strategy for black start, failing to adequately consider the impact of different installation locations, seasonal variations, and weather conditions on photovoltaic power generation capacity. For example, if the start-up time is set too early, insufficient sunlight can cause the microinverter to output power stably, easily leading to start-up failure; while if the start-up time is set too late, it may miss effective power generation periods, reducing the overall power generation revenue of the system.

[0004] Furthermore, existing technologies for black start control typically lack the utilization of historical operating data and fail to optimize the start-up timing based on past successful start-ups, resulting in poor adaptability of the start-up strategy. The successful start-up timing of microinverters varies significantly under different weather conditions; without dynamic correction using historical data, the success rate of black start can be easily affected.

[0005] Therefore, how to reasonably determine the black start time under different weather conditions and time environments in order to improve the start-up success rate of micro-inverters while taking into account power generation efficiency has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a black-start control method for an energy storage system, an energy storage system, and a readable storage medium. To improve the startup success rate of microinverters while maintaining power generation efficiency, this invention dynamically determines the expected black-start time of the day by acquiring weather information and successful black-start records from a historical database, combined with the day's weather forecast and astronomical information. This allows the energy storage inverter to start at a time that better matches actual sunlight conditions, making it easier for the microinverter to start. Since a fixed-time strategy is no longer used, but rather adaptive adjustments are made based on environmental changes, the problems of insufficient sunlight due to startup too early or wasted power generation time due to startup too late can be effectively avoided. Simultaneously, by incorporating historical successful data and correcting for successful startup times under similar weather conditions, the startup decision becomes more targeted and stable, thereby improving the black-start success rate, reducing the risk of startup failure due to environmental uncertainties, and overall enhancing the reliability and power generation utilization efficiency of the coordinated operation of the energy storage system and the microinverter.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a black-start control method for an energy storage system, used to perform black-start on a micro-inverter in the system. The black-start control method includes the following steps: Retrieve the historical database, which stores weather information for each moment within a preset time period, as well as records of successful black start. Obtain current system status information, including the day's weather forecast and astronomical information calculated based on geographical location and date; Based on the day's weather forecast, astronomical information, and similar successful dark start records in the historical database, the expected dark start time for the day is dynamically determined. The energy storage inverter is activated at the expected black start moment to establish AC voltage for the micro-inverter to detect and follow up with its startup.

[0008] In some embodiments, the astronomical information includes the sunrise time of the day, and dynamically determining the expected dark start time of the day includes: The earliest possible start time is determined by subtracting the first preset duration from the sunrise time. The earliest possible start time will be adjusted based on the day's weather forecast; Search the historical database for historical dates similar to the current day's weather forecast, obtain the time when a black start was successfully performed on that date, and align the corrected start time with that historical successful time to obtain the final expected black start time.

[0009] In some embodiments, the historical database adopts a rolling update method: at midnight every day, the data of the current day is stored in the previous day, the data of the previous day is stored in the previous two days, the data of the previous two days is stored in the previous three days, and the data of the current day is cleared to record new data. Based on the historical data that is updated on a rolling basis, the average start time and success rate under different weather conditions are statistically analyzed, and the mapping relationship between weather information and black start success records is updated.

[0010] In some embodiments, the current system status information also includes the real-time remaining battery power of the energy storage system, and the method further includes: The remaining battery power is divided into power ranges, and corresponding inverter start-up modes are preset for different power ranges. At the expected black start time, the inverter is started according to the start mode corresponding to the power range.

[0011] In some embodiments, the power range includes: When the battery is fully charged, the first startup mode is activated, which is when the inverter is always on. The normal mode range corresponds to the second startup mode, which is the intermittent startup mode with the first duty cycle. The conservative mode range corresponds to the third start mode, which is an intermittent start mode with the second duty cycle, and the second duty cycle is smaller than the first duty cycle; The survival mode range corresponds to the fourth startup mode, which is a mode that attempts to start with a low duty cycle only during a preset period before and after the strongest sunlight.

[0012] In some embodiments, the power range is divided by a first power threshold, a second power threshold, and a third power threshold, wherein the first power threshold > the second power threshold > the third power threshold; The first, second, and third power thresholds are calculated based on the total capacity of the energy storage system, standby power consumption, and additional startup power consumption, ensuring that the reserved power in each power range can support the energy storage system to operate in the corresponding mode for at least one day.

[0013] In some embodiments, the method further includes: If startup fails, the system will wait for a predetermined time and then attempt to start again, according to the intermittent retry strategy corresponding to the current battery level range.

[0014] In some embodiments, when the energy storage inverter is started at the expected black start moment, a low-voltage regulation method is used to establish the AC voltage. The low-voltage regulation method involves setting the inverter output voltage to a value slightly higher than the grid-connected certification undervoltage point, reducing the bus voltage, and shutting down unnecessary power-consuming modules.

[0015] In some embodiments, the method further includes: Monitor the output power of the microinverter after startup; If the output power of the micro inverter exceeds the first power threshold for a continuous period of time, it is determined that the startup is successful, and the inverter output voltage is gradually adjusted to the rated value. If the output power of the microinverter remains below the second power threshold for the second time period without any upward trend, it is determined to be a startup failure, and the startup result at the current moment is recorded in the historical database; wherein, the second power threshold is less than the first power threshold.

[0016] In some embodiments, the method further includes: After a successful start-up is determined, the output power of the micro-inverter is continuously monitored. When the output power remains below the shutdown threshold and the current time is later than sunset, the inverter is shut down and the start-prohibited flag is set until the next day.

[0017] Secondly, the present invention also provides an energy storage system, the system comprising: Photovoltaic modules, microinverters, energy storage batteries, energy storage inverters, loads and controllers; The DC side of the energy storage inverter is connected to the energy storage battery, and the DC side of the microinverter is connected to the photovoltaic module; the AC side of the microinverter and the AC side of the energy storage inverter are connected in parallel and then connected to the load. The controller includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the black-start control method for the energy storage system provided in the first aspect.

[0018] Thirdly, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the black-start control method for the energy storage system provided in the first aspect.

[0019] The beneficial effects of this invention are as follows: Compared with the prior art, this application dynamically determines the expected black start time of the day by acquiring weather information and successful black start records from historical databases, and combining them with the daily weather forecast and astronomical information. This allows the energy storage inverter to be started at a time that better matches the actual sunlight conditions, making it easier for the micro-inverter to start up. Since a fixed-time strategy is no longer used, but rather adaptive adjustments are made based on environmental changes, the problems of insufficient sunlight due to starting too early or wasted power generation time due to starting too late can be effectively avoided. Simultaneously, by introducing historical successful data and correcting for successful start times under similar weather conditions, the start-up decision becomes more targeted and stable, thereby improving the black start success rate, reducing the risk of start-up failure due to environmental uncertainties, and overall improving the reliability and power generation utilization efficiency of the coordinated operation of the energy storage system and the micro-inverter.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 A schematic diagram of the architecture of an energy storage system provided by the present invention; Figure 2 This is a flowchart illustrating a black-start control method for an energy storage system according to an embodiment of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that references to "an embodiment," "embodiment," "example embodiment," etc., in this specification refer to the described embodiment including specific features, structures, or characteristics; however, not every embodiment must include these specific features, structures, or characteristics. Furthermore, such expressions do not refer to the same embodiment. Moreover, when describing specific features, structures, or characteristics in conjunction with embodiments, whether or not explicitly described, it is indicated that incorporating such features, structures, or characteristics into other embodiments is within the knowledge of those skilled in the art.

[0024] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] like Figure 1 As shown, an energy storage system is provided, including photovoltaic modules (PV), microinverters (MINV), energy storage batteries (BAT), energy storage inverters (INV), grid-connected relays (S1), loads (LOAD), and a power grid (GRID). The DC side of the energy storage inverters is connected to the energy storage batteries, and the DC side of the microinverters is connected to the photovoltaic modules. The AC sides of the microinverters (MINV), the energy storage inverters (INV), the load (LOAD), and the grid-connected relays (S1) are all connected to the PCC (Point of Common Coupling). When the grid is present, the grid-connected relays (S1) are energized, receiving voltage support from the grid, and interacting with MINV, INV, and LOAD. When the grid is absent, the grid-connected relays (S1) are de-energized, the PCC is supplied with voltage support from INV, absorbing energy from the MINV and providing energy to the load.

[0026] In a black-start scenario, the energy storage inverter starts first and actively establishes an AC voltage (e.g., 220V / 50Hz). The microinverter starts later; upon detecting the AC voltage, it automatically follows and begins converting the DC power from the photovoltaic modules into AC power for power output. For the energy storage inverter, "start-up" refers to the process of switching from standby / dormant state to power output state and establishing a rated voltage on the AC side. For the microinverter, "start-up" refers to the process of switching from monitoring state to power generation state and beginning to feed power into the AC side.

[0027] To address the issues of fixed black start time and lack of response to severe weather in existing technologies, the following are several black start control methods for energy storage systems.

[0028] Example 1 like Figure 2 As shown, a black-start control method for an energy storage system is provided, including: S101, retrieve historical database.

[0029] The historical database stores weather information for each moment within a preset time period, as well as records of successful black start.

[0030] Specifically, the energy storage system is used to perform black-start control on micro-inverters in off-grid or grid outage scenarios. First, the system establishes and maintains a historical database to store weather information and successful black-start records for each moment within a preset time period. The preset time period can be flexibly configured according to the system's storage capacity and algorithm requirements; for example, it can store data from the past three days, seven days, or one month. Weather information includes not only macro-level weather conditions (such as sunny, cloudy, overcast, and rainy) but can also be further refined to micro-level meteorological parameters such as light intensity and cloud cover. Successful black-start records include at least whether the start was successful, the corresponding time information, and weather information. The historical database can be continuously updated chronologically to reflect the actual execution effect of black-start under different weather conditions.

[0031] Specifically, the historical database is maintained using a rolling update method, meaning that the data is updated on a daily basis. When the system time reaches midnight each day, the current day's data is transferred to the previous day's data, the previous day's data is transferred to the previous two days' data, the previous two days' data is transferred to the previous three days' data, and so on, and the current day's data storage area is cleared to prepare for recording the operational data of the new day, thus forming a continuous historical data sequence spanning multiple days.

[0032] During data recording, the system stores the weather information and corresponding black start execution results at each moment. The black start execution results include whether the start was successful and the specific time and weather information corresponding to a successful start. Through the above rolling update method, the historical database can be guaranteed to always reflect the operation status of the most recent few days and has strong timeliness.

[0033] Based on continuously updated historical data, the average startup time and success rate under different weather conditions are statistically analyzed to update the mapping relationship between weather information and successful black start records. For example, historical data is divided into weather types such as sunny, cloudy, and overcast, and the average startup time and success rate under each weather condition are statistically analyzed to establish a correlation between weather information and successful black start records. This correlation can be used in the subsequent dynamic calculation of black start time, allowing the startup time to be optimized and adjusted based on historical experience, thereby improving the rationality and stability of the overall startup strategy.

[0034] S102, Obtain current system status information.

[0035] The system status information includes the day's weather forecast and astronomical information calculated based on geographical location and date.

[0036] Specifically, the system first acquires current system status information, including the day's weather forecast and astronomical information calculated based on the energy storage system's installation location and the current date. The astronomical information primarily refers to the sun's orbital parameters, including at least sunrise and sunset times. Subsequently, the system determines a baseline time point based on this astronomical information, for example, using sunrise time as a reference to determine the time range where sunlight conditions may be present.

[0037] S103 dynamically determines the expected dark start time of the day based on the day's weather forecast, astronomical information, and similar successful dark start records in the historical database.

[0038] Specifically, the system adjusts the base time based on the day's weather forecast. For example, in good weather conditions, the start time is moved forward, while in cloudy or poor lighting conditions, the start time is postponed. Furthermore, the system searches the historical database for historical dates with similar weather conditions, extracts the corresponding successful black start times, and adjusts the currently calculated start time to align it with historical successful start times, thus obtaining the final expected black start time.

[0039] Optionally, the astronomical information includes the sunrise time of the day. Dynamically determining the expected black start time of the day includes: subtracting a first preset duration from the sunrise time to obtain the earliest possible start time; making weather corrections to the earliest possible start time based on the weather forecast of the day; searching the historical database for historical dates similar to the weather forecast of the day, obtaining the time of successful black start on that date, and aligning the corrected start time with that historical successful time to obtain the final expected black start time.

[0040] Specifically, the astronomical information includes the sunrise time of the day, which the system uses as a reference benchmark for changes in lighting conditions. First, the earliest possible start-up time is determined by subtracting a first preset duration from the sunrise time, ensuring that the system enters the start-up preparation phase before basic lighting conditions are met.

[0041] Based on this, the system adjusts the earliest possible start-up time according to the weather forecast for the day. For example, if the weather forecast is sunny, the lighting conditions are good, and the earliest possible start-up time does not need to be delayed; if the weather forecast is cloudy or overcast, the earliest possible start-up time is delayed according to preset rules to avoid starting the micro-inverter under insufficient lighting conditions.

[0042] Furthermore, the system searches the historical database for historical dates similar to the current day's weather forecast and obtains the time information of successful blackouts on those dates. Based on this, the weather-corrected start time is adjusted to align with historical successful start times, for example, through weighted averaging or offset correction, so that the final determined expected blackout start time is closer to historically high-success-rate start times.

[0043] By employing a triple dynamic calibration mechanism combining astronomical calculations, weather forecasts, and historical experience, an adaptive start-up window is constructed that is neither blindly aggressive nor overly conservative. This mechanism can obtain a more reasonable expected black start time based on a full consideration of the changing trends of daily sunlight conditions and historical operating experience. This fundamentally solves the problem of premature power consumption or excessively late waste of photovoltaic energy caused by fixed-time start-ups, thus providing a more reliable time basis for subsequent black start operations.

[0044] S104 starts the energy storage inverter at the expected black start moment, establishes AC voltage, and provides the micro-inverter with detection and follow-up startup.

[0045] Specifically, when the system time reaches the expected black-start moment, the control energy storage inverter starts and establishes AC voltage output, enabling the micro-inverter to detect the AC side voltage and complete grid-connected follow-up startup. This method allows the black-start process to be executed at a time more consistent with actual lighting conditions, thereby improving the startup success rate of the micro-inverter and enhancing the system's adaptability to different environmental conditions.

[0046] Unlike the fixed start-up time in existing technologies, this application dynamically determines the expected black start time of the day by combining the daily weather forecast, astronomical information calculated based on geographical location and date (such as sunrise time), and similar successful black start records in the historical database. This allows the start-up time to adapt to changes in installation location, season, and real-time weather, avoiding both insufficient photovoltaic energy consumption due to start-up too early and wasted photovoltaic energy due to start-up too late. Thus, while ensuring the success rate of black start, the start-up time is advanced as much as possible, effectively improving system stability and user benefits.

[0047] Example 2 Building upon Example 1, this example further introduces a tiered defense mechanism based on remaining battery power to address the system's survival issues when battery power is low or during prolonged periods of severe weather. When the system is in islanded operation and photovoltaic energy is insufficient to power the micro-inverter for an extended period, blindly continuing to operate the energy storage inverter will rapidly deplete the battery, leading to complete system failure. Therefore, this example deeply integrates battery status with startup behavior, shifting from "indiscriminate startup" to "refined startup based on survival probability."

[0048] The current system status information also includes the real-time remaining battery power of the energy storage system. The method also includes: dividing the battery power into power ranges based on the remaining battery power and pre-setting corresponding inverter start-up modes for different power ranges; and starting the inverter according to the start-up mode corresponding to the power range at the expected black start time.

[0049] The State of Charge (SOC) refers to the percentage of the energy storage battery's current available capacity relative to its rated total capacity. Before each decision, the system reads the latest SOC value from the Battery Management System (BMS) and uses this value to categorize the current state of charge into one of the preset ranges. Each range corresponds to a distinct startup mode.

[0050] The power range includes: the fully charged range, corresponding to the first start-up mode, in which the inverter is always on; the normal mode range, corresponding to the second start-up mode, in which the second start-up mode is an intermittent start-up mode with the first duty cycle; the conservative mode range, corresponding to the third start-up mode, in which the third start-up mode is an intermittent start-up mode with the second duty cycle, which is less than the first duty cycle; and the survival mode range, corresponding to the fourth start-up mode, in which the fourth start-up mode attempts to start up with a low duty cycle only during a preset period before and after the strongest sunlight.

[0051] These four ranges constitute a four-level degradation defense line for the system to cope with energy crises. When the State of Charge (SOC) is in the sufficient charge range, the system has ample energy budget, so it adopts the first startup mode, i.e., the inverter is always on. After the expected black start moment arrives, the energy storage inverter continuously outputs AC voltage, providing the most relaxed following environment for the micro-inverter without worrying about standby losses. When the SOC is in the normal mode range, the system begins to recognize the energy crisis. At this time, it adopts the second startup mode, i.e., the intermittent startup mode with the first duty cycle, to ensure a certain probability of successful startup while reducing energy consumption. In a typical implementation, this first duty cycle is a cycle of "5 minutes on, 5 minutes off". When the SOC is in the conservative mode range, the system enters a high alert state and adopts the third startup mode, i.e., the intermittent startup mode with the second duty cycle, to further reduce energy consumption during the inverter startup process. In a typical implementation, this second duty cycle is a cycle of "2 minutes on, 8 minutes off". It should be understood that 5 minutes / 5 minutes and 2 minutes / 8 minutes are merely illustrative preferred examples and not restrictive, as long as the overall on-time percentage of the second duty cycle is less than that of the first duty cycle. Finally, when the SOC is in the most dangerous survival mode range, the system is already on the verge of death, and any regular intermittent startup may exhaust the last bit of power due to the accumulated additional power consumption during startup; therefore, the fourth startup mode only performs tentative startups with an extremely low duty cycle within a preset time period before and after the moment of highest sunlight (i.e., solar noon, which can be accurately calculated using the astronomical algorithm in Example 1), for example, within a window of 1 hour before and after noon, in order to minimize unnecessary energy consumption and extend system uptime.

[0052] The power range is divided by a first power threshold, a second power threshold, and a third power threshold, where the first power threshold > the second power threshold > the third power threshold. The first, second, and third power thresholds are calculated based on the total capacity of the energy storage system, standby power consumption, and additional startup power consumption, ensuring that the reserved power within each power range can support the energy storage system to operate in the corresponding mode for at least one day. In a typical implementation, the first power threshold is set to 25%, the second power threshold to 15%, and the third power threshold to 10%.

[0053] The method further includes: if the startup fails, waiting for a predetermined time and then attempting to start again according to the intermittent retry strategy corresponding to the current power range.

[0054] For example, when the system attempts to start at the expected black start time, if the microinverter fails to keep up with the output power, the system must stop its current on state to mitigate losses, but this does not mean the system should give up. If the system is in normal mode, its retry strategy follows the first duty cycle, such as waiting 5 minutes and then trying to start again for 5 minutes; if it is in conservative mode, it follows the second duty cycle, such as waiting 8 minutes and then trying to start again for 2 minutes. The system does not need to recalculate the waiting time after each failure, but directly uses the off period in the preset duty cycle of the current power range as the waiting time. This not only simplifies the control logic, but more importantly, ensures that the cumulative energy consumption of the entire retry process strictly conforms to the aforementioned preset duty cycle, and will not disrupt the energy budget balance due to frequent retry impulses. For survival mode, since it only attempts at the noon window, if the noon attempt fails, it will not retry, but directly enter deep sleep to wait for the arrival of noon the next day, protecting the last power energy in an absolutely conservative manner.

[0055] Once the microinverter starts successfully and the output power stably exceeds the minimum maintenance threshold, the system will immediately exit the intermittent mode and enter continuous operation, no longer periodically shutting down according to the preset duty cycle.

[0056] By dividing the battery into different power ranges (sufficient, normal, conservative, and survival) based on real-time remaining battery power, and pre-setting corresponding inverter start-up modes for each range (always on, intermittent start-up with different duty cycles, and trial start-up with extremely low duty cycles), the system can intelligently reduce the total time and frequency of inverter start-up when the battery is low or encounters continuous severe weather. The principle behind this graded protection and intermittent retry strategy is: accurately calculating the threshold for each range based on the system's standby power consumption and additional start-up power consumption, ensuring that the reserved power can support the system to operate in the corresponding low-power mode for at least one day, thereby minimizing unnecessary system losses, significantly extending the system's islanded "survival time," and improving robustness against severe weather.

[0057] Example 3 Based on Embodiment 1 and Embodiment 2, this embodiment further elaborates on the hardware-level energy-saving measures at the moment of startup of the energy storage inverter and the closed-loop monitoring of the entire life cycle after startup, thereby forming a full-process protection from dynamic planning before startup, extreme energy saving during startup, closed-loop judgment after startup to sunset shutdown at the end of operation.

[0058] Regarding the ultimate energy-saving strategy at startup, when starting the energy storage inverter at the expected black start moment, a low-voltage regulation method is used to establish the AC voltage. The low-voltage regulation method involves setting the inverter output voltage to a value slightly higher than the grid-connected certification undervoltage point, reducing the bus voltage, and shutting down unnecessary power-consuming modules.

[0059] Specifically, the "grid connection certification undervoltage point" refers to the minimum AC voltage threshold allowed for grid connection of an inverter as specified in national grid regulations or product certification standards, typically between 0.85 and 0.9 times the rated voltage Un. In a typical implementation, if the grid connection certification undervoltage point is 0.85Un, the low-voltage regulation method sets the energy storage inverter output voltage at 0.88Un, which is slightly higher than the undervoltage point by about 3%-5%, to ensure that the micro-inverter can reliably detect the presence of the grid. Simultaneously, the system actively reduces the internal DC bus voltage and shuts down unnecessary power-consuming modules such as the display screen, some sampling circuits, and cooling fans. Before the micro-inverter successfully follows the output power, the AC power established by the energy storage inverter is in an unloaded or low-load standby state. Maintaining the rated voltage (e.g., 220V) at this time requires the bus to maintain high voltage and all modules to operate at full load, resulting in significant no-load losses. Since the system's sole objective at this time is to wake up the micro-inverter, the micro-inverter only needs to detect the presence of voltage and does not require the voltage amplitude to immediately reach the rated full-power output standard. Therefore, by actively suppressing the output voltage of the energy storage inverter to just slightly above the minimum detection threshold and cutting off all redundant power-consuming circuits, the system's standby power consumption at startup can be reduced to the minimum level. This is crucial in low power ranges (especially in conservative or survival modes) and determines whether the system can survive the startup attempt period.

[0060] Regarding the closed-loop judgment mechanism after startup, the method further includes: monitoring the output power of the microinverter after startup; if the output power of the microinverter exceeds the first power threshold for a first time period, it is determined that the startup is successful, and the inverter output voltage is gradually adjusted to the rated value; if the output power of the microinverter is lower than the second power threshold for a second time period and there is no increasing trend, it is determined that the startup has failed, and the startup result at the current moment is recorded to the historical database; wherein, the second power threshold is less than the first power threshold.

[0061] For example, after the energy storage inverter establishes voltage in low-voltage mode, the microinverter begins to attempt to follow. At this time, the system must continuously perform a "power value judgment" on the output power of the microinverter to confirm whether the photovoltaic energy has been effectively captured. This embodiment sets two decision branches. In the success decision branch, if the output power of the microinverter exceeds the first power threshold (e.g., P_min is 200W) for a first time period (e.g., T1 is 3 to 5 minutes), it is determined that the startup is successful. The selection and setting of the first power threshold should not only cover the operating losses of the energy storage inverter at rated voltage, but also generate a net margin to charge the energy storage battery, indicating that the microinverter has crossed the minimum self-sufficiency threshold and the system has entered a positive energy accumulation state. Once the determination is successful, the system will gradually adjust the inverter output voltage to the rated value, for example, slowly boosting it to 220V at a rate of 1V per second, while restoring the bus voltage and shutting down unnecessary modules. The reason for using a slow voltage increase instead of an instantaneous jump is to avoid the micro-inverter disconnecting from the grid due to overcurrent protection during transient voltage surges, ensuring a smooth and stable transition process. In the failure judgment branch, if the micro-inverter's output power remains below the second power threshold (e.g., P2 is 100W) for a continuous second time period (e.g., T2 is 5 to 10 minutes) and shows no increasing trend, it is judged as a startup failure. The selection and setting of the second power threshold must meet the following condition: it cannot even cover the operating losses of the energy storage inverter, meaning that the photovoltaic energy is severely insufficient, the micro-inverter is in an ineffective idling state or an extremely low power output state, and continuing to maintain the voltage will only consume battery power in one direction. At this time, the system must decisively judge the failure, shut down the inverter output, and record the current weather information and failure result to the historical database, providing negative sample experience for subsequent rolling updates and matching of similar days, realizing a decision-making closed loop.

[0062] Regarding the sunset shutdown logic at the end of operation, the method further includes: after determining that the startup is successful, continuously monitoring the output power of the micro-inverter; when the output power is continuously lower than the shutdown threshold and the current time is later than the sunset time, shutting down the inverter and setting the prohibition startup flag until the next day.

[0063] For example, after the system successfully starts up and runs for a period of time, the photovoltaic radiation intensity inevitably decreases as the sun gradually sets. The shutdown threshold mentioned in this embodiment can be the same as the aforementioned second power threshold (e.g., 100W), or it can be set to a slightly higher value (e.g., 150W). The selection and setting standard is that the power has dropped to the critical point where the system can no longer maintain positive energy accumulation. After the black start is determined to be successful, the system enters the operation monitoring stage, continuously tracking the output power changes of the micro-inverter. When the output power is detected to be continuously lower than the preset shutdown threshold, the system further judges based on the current system time; if the current time is later than the sunset time of the day, the inverter is controlled to shut down the output and the start-prohibited flag is set to avoid repeated startup under conditions of no effective light, which would cause energy waste; if the current time has not yet reached the sunset time, it is considered that the current situation is an abnormal fluctuation in the operation process, and the system can enter intermittent operation or try to start again according to the preset strategy, thereby realizing closed-loop control of the black start process and improving the system's operational stability and energy utilization efficiency under complex environmental conditions.

[0064] By continuously updating the historical database and statistically analyzing the average startup time and success rate under different weather conditions, the system can continuously optimize subsequent startup decisions based on past experience, achieving refined historical learning. At the same time, from power planning before startup, low-voltage attempts and power value judgment during startup, to slow voltage recovery after successful startup, and then to continuous power monitoring during operation and automatic shutdown of the inverter and setting of the start-prohibited flag during sunset and low power periods, a closed-loop control is formed throughout the entire life cycle, effectively avoiding continuous power consumption at night and during inactive periods, and ensuring refined energy management of the system.

[0065] Example 4 This application also provides a computer-readable storage medium for storing a computer program that executes a black-start control method for an energy storage system. For example, computer program instructions, when executed by a computer, can invoke or provide the methods and / or technical solutions according to this application through the operation of the computer. The program instructions that invoke the methods of this application may be stored in a fixed or removable storage medium, and / or transmitted via data streams in broadcast or other signal carrying media, and / or stored in a storage medium that operates according to the program instructions.

[0066] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device, or fabricating them separately as individual integrated circuit modules, or fabricating multiple modules or steps as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0067] The technical features of the above embodiments can be arbitrarily integrated. For the sake of brevity, not all possible integrations of the technical features in the above embodiments are described. However, as long as the integration of these technical features does not contradict each other, they should be considered to be within the scope of this specification.

[0068] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A black-start control method for an energy storage system, characterized in that, The black start control method for performing a black start on a micro inverter in a system includes the following steps: Obtain the historical database, which stores weather information for each moment within a preset time period and records of successful black start; Obtain current system status information, including the day's weather forecast, as well as astronomical information calculated based on geographical location and date, and the real-time remaining battery power of the energy storage system; Based on the daily weather forecast, astronomical information, and similar successful dark start records in the historical database, the expected dark start time for the day is dynamically determined, including: subtracting a first preset duration from the sunrise time to obtain the earliest possible start time; applying weather correction to the earliest possible start time based on the daily weather forecast; searching the historical database for historical dates similar to the daily weather forecast, obtaining the successful dark start time for that date, and aligning the corrected start time with that historical successful time to obtain the final expected dark start time; The remaining battery power is divided into power ranges based on the real-time battery power, and corresponding inverter start-up modes are preset for different power ranges; at the expected black start time, the inverter is started according to the start-up mode corresponding to the power range; an AC voltage is established for the micro inverter to detect and start accordingly; The power range includes: a fully charged range, corresponding to the first startup mode, where the inverter is always on; a normal mode range, corresponding to the second startup mode, where the second startup mode is an intermittent startup mode with a first duty cycle; a conservative mode range, corresponding to the third startup mode, where the third startup mode is an intermittent startup mode with a second duty cycle, where the second duty cycle is less than the first duty cycle; and a survival mode range, corresponding to the fourth startup mode, where the fourth startup mode is a mode that attempts to start the inverter with a low duty cycle only during a preset period before and after the strongest sunlight.

2. The black-start control method for an energy storage system according to claim 1, characterized in that, The historical database adopts a rolling update method: at midnight every day, the data of the day is stored in the previous day, the data of the previous day is stored in the previous two days, the data of the previous two days is stored in the previous three days, and the data of the day is cleared to record new data. Based on the continuously updated historical data, the average startup time and success rate under different weather conditions are statistically analyzed, and the mapping relationship between weather information and successful black start records is updated.

3. The black-start control method for an energy storage system according to claim 1, characterized in that, The power range is divided by a first power threshold, a second power threshold, and a third power threshold, wherein the first power threshold > the second power threshold > the third power threshold; The first, second, and third power thresholds are calculated based on the total capacity of the energy storage system, standby power consumption, and additional startup power consumption, ensuring that the power reserved in each power range can support the energy storage system to operate in the corresponding mode for at least one day.

4. The black-start control method for an energy storage system according to claim 1, characterized in that, The method further includes: If startup fails, the system will wait for a predetermined time and then attempt to start again, according to the intermittent retry strategy corresponding to the current battery level range.

5. The black-start control method for an energy storage system according to claim 1, characterized in that, When the energy storage inverter is started at the expected black start time, a low-voltage regulation method is used to establish the AC voltage. The low-voltage regulation method is to set the inverter output voltage to a value slightly higher than the grid connection certification undervoltage point, reduce the bus voltage, and shut down unnecessary power-consuming modules.

6. The black-start control method for an energy storage system according to claim 1, characterized in that, The method further includes: Monitor the output power of the microinverter after startup; If the output power of the micro inverter exceeds the first power threshold for a continuous period of time, it is determined that the startup is successful, and the inverter output voltage is gradually adjusted to the rated value. If the output power of the microinverter remains below the second power threshold for the second time period without any upward trend, it is determined to be a startup failure, and the startup result at the current moment is recorded in the historical database; wherein, the second power threshold is less than the first power threshold.

7. The black-start control method for an energy storage system according to claim 6, characterized in that, The method further includes: After a successful start-up is determined, the output power of the micro-inverter is continuously monitored. When the output power remains below the shutdown threshold and the current time is later than sunset, the inverter is shut down and the start-prohibited flag is set until the next day.

8. An energy storage system, characterized in that, include: Photovoltaic modules, microinverters, energy storage batteries, energy storage inverters, loads and controllers; The DC side of the energy storage inverter is connected to the energy storage battery, and the DC side of the micro-inverter is connected to the photovoltaic module; the AC side of the micro-inverter and the AC side of the energy storage inverter are connected in parallel and then connected to the load. The controller includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the black-start control method of the energy storage system as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the black-start control method for the energy storage system as described in any one of claims 1 to 7.

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