Photovoltaic power generation energy storage system switching system and switching method

Abstract

The invention belongs to the technical field of power supply, and particularly relates to a photovoltaic power generation energy storage system switching system and a switching method, and the method comprises the steps: building an output trend prediction model and issuing an early warning signal at the initial stage of illumination change, starting the pre-charging and state self-inspection of an energy storage battery in advance, and synchronously carrying out the phase locking and voltage matching preparation of a commercial power side, a real-time monitoring network covering the whole system is constructed before switching so as to evaluate the bus stability, and then grading decreasing of photovoltaic output and synchronous power undertaking of an energy storage battery are executed after the condition is confirmed to be met, so that smooth transition between power supplies is realized. According to the method, the passive response of a traditional system after the voltage drops is avoided, the voltage fluctuation and power supply interruption in the switching process are effectively eliminated, the power supply continuity and the electric energy quality are remarkably improved, and the power utilization experience of a user and the equipment operation safety are guaranteed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power supply, and particularly relates to a photovoltaic power generation energy storage system switching system and a switching method. BACKGROUND

[0002] In the prior art, a photovoltaic power generation system applied to off-grid or grid-connected type homestays usually adopts a photovoltaic energy storage power supply three-stage architecture. When the light is sufficient, the system preferentially uses photovoltaic power, and stores the excess power in the battery; when the light is insufficient or at night, the system switches to the energy storage battery or the power supply. The conventional switching mode relies on a voltage drop triggering mechanism, that is, when the photovoltaic output voltage drops below the set threshold, the control system starts the standby power supply. In this process, the access of the energy storage battery or the power supply often has a millisecond-level response delay, and lacks pre-judgment and preparation of the power supply state.

[0003] Especially under dynamic light conditions such as rainy weather or rapid movement of clouds, the photovoltaic output presents a sharp fluctuation, which leads to frequent start-stop switching logic of the system, and easily causes voltage sag, current impact or temporary power failure at the switching moment. This problem directly affects the normal operation of sensitive loads such as lighting, temperature control and communication, causing light flickering, equipment restart or even damage, and seriously reduces the living comfort and power supply safety. SUMMARY

[0004] The purpose of the present application is to provide a photovoltaic power generation energy storage system switching system and a switching method, which avoids the passive response of the traditional system after the voltage has dropped, effectively eliminates the voltage fluctuation and power supply interruption in the switching process, and significantly improves the power supply continuity and power quality, so as to solve the problems raised in the background technology.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: a switching method of a photovoltaic power generation energy storage system, comprising: When it is detected that the light condition change leads to a photovoltaic output decline trend, a photovoltaic output trend prediction model is established and updated in real time; In response to the output attenuation warning signal, the energy storage battery pre-charging and state self-checking program is started, and after the energy storage battery enters the standby discharge state, the city side synchronous phase locking and voltage matching program is started; On the basis that the city power supply completes synchronization and the energy storage battery is ready, a multi-source power supply state monitoring network is constructed and the bus stability is evaluated in real time; After confirming that the bus voltage, frequency and harmonic index meet the switching conditions, the graded power transfer from photovoltaic power supply to energy storage battery is performed; After the energy storage battery completely bears the load output, the city static switch is activated and the dual-source parallel power supply mode is established; Under the premise of stable operation of dual-source power supply, the load-side power supply path reconstruction and electrical isolation are performed. After the power path adjustment is completed, the switching completion status is released and the energy-saving operation mode is started.

[0006] Preferably, the establishment of the photovoltaic output trend prediction model includes: Collect the output power sequence of the photovoltaic array over a continuous daily period; Typical output mode intervals are divided based on the output power sequence; The current power output curve is compared with the model characteristics in the template library in real time, and the power output trend prediction results are corrected by combining real-time meteorological data.

[0007] Preferably, the step of dividing the typical output mode range based on the output power sequence includes: The average power and standard deviation for each interval were calculated using a 5-minute sliding window. Based on the average power range, they are classified into high power range, medium power range, low power range, and extremely low power range; A power output pattern template library is established based on the classification results, and real-time pattern matching is performed based on the template library.

[0008] Preferably, the initiation of the energy storage battery pre-charging and status self-check procedure includes: Read the current state of charge and health parameters of the energy storage battery; The minimum usable capacity of the energy storage battery is calculated based on the aforementioned state of charge and health parameters. Perform battery pack pre-charging to compensate for self-discharge losses and detect the internal balance and connection reliability of the battery pack.

[0009] Preferably, the reading of the current state of charge and health parameters of the energy storage battery is obtained based on the ampere-hour integration method combined with open-circuit voltage calibration.

[0010] Preferably, the initiation of the mains-side synchronous phase-locked loop and voltage matching procedure includes: Measure the real-time voltage and frequency at the mains power connection point; Based on the voltage and frequency, an inverter output reference signal with the same frequency and phase as the mains power is generated, and the inverter output voltage amplitude is adjusted to approximate the mains power level. Based on the generated reference signal and the adjusted voltage amplitude, the matching status of frequency, phase and voltage is verified, and standby grid connection conditions are established.

[0011] Preferably, the construction of a multi-source power supply status monitoring network and real-time evaluation of bus stability includes: Deploy distributed voltage and current detection nodes to collect electrical parameters from photovoltaic output terminals, energy storage battery ports, mains power access points, DC buses, AC buses, and major load branches; The DC bus voltage fluctuation rate and ripple coefficient are calculated based on the sampling data of the detection nodes to determine the stability of the DC side energy supply. Based on the calculation results of the volatility and ripple coefficient, analyze the AC bus frequency offset and harmonic distortion, and evaluate whether the AC side power quality meets the load operation requirements. Based on the results of the DC bus stability assessment and the AC bus power quality evaluation, a comprehensive determination is made as to whether the system is ready to perform subsequent power transfer.

[0012] Preferably, the step-by-step power transfer from photovoltaic power to energy storage batteries includes: Set the time window and step size for the decrease in photovoltaic output power, determine the total transition time as 800 milliseconds and divide it into 8 adjustment intervals of 100 milliseconds; Based on the time window and step size, the duty cycle of the photovoltaic DC-DC converter is adjusted to reduce the output power, so that the photovoltaic output power gradually decreases according to a preset slope. While the output power of photovoltaics decreases, the discharge power of energy storage batteries is increased simultaneously to compensate for the power gap and ensure that the total input power of DC bus remains stable. During the power transfer process, the bus voltage deviation is monitored in real time, and the discharge power adjustment ratio of the energy storage battery is dynamically adjusted according to the voltage fluctuation to maintain the bus voltage within ±2% of the nominal value.

[0013] Preferably, activating the mains static switch and establishing a dual-source parallel power supply mode includes: Once it is confirmed that the energy storage battery has undertaken the full load power, by comparing the matching degree between the total input power of the DC bus and the output power of the energy storage battery, it is determined that the photovoltaic power has been completely withdrawn and the battery is in an independent and stable power supply state. After the independent power supply status of the energy storage battery is confirmed, a pre-trigger pulse signal is sent to the static switch to make the thyristor enter the quasi-conducting state to shorten the closing delay. During the application of the pre-trigger pulse, the phase difference between the mains power and the inverter output voltage is continuously monitored. When both voltages are detected to cross zero simultaneously and have the same polarity, the static switch is closed synchronously to achieve grid connection without impact. After the static switch is fully turned on, the inverter output is adjusted to achieve power distribution on demand, gradually reducing its output power and shifting the load proportion to the mains side, forming a dual-source parallel power supply mode with mains power as the main source and energy storage battery as the auxiliary source.

[0014] On the other hand, the present invention proposes a switching system for a photovoltaic power generation and energy storage system, comprising: Photovoltaic array units are used to collect output power sequences and participate in the establishment of photovoltaic power output trend prediction models. The energy storage battery pack is used to initiate pre-charging and status self-check after receiving an output attenuation warning signal; The mains power access port is used to perform synchronous phase-locking and voltage matching after the energy storage battery enters standby mode. A multi-channel power detection network is used to build a monitoring network and assess bus stability after mains power synchronization is completed; The central control unit is used to control the reduction of photovoltaic output, start the grid power connection, reconfigure the power supply path and release the operating status after confirming that the switch is ready; The four-quadrant bidirectional converter is used to adjust the power output during load transfer and to achieve on-demand power distribution during the dual-source parallel phase.

[0015] Technical effects and advantages of the present invention: The photovoltaic power generation and energy storage system switching system and switching method proposed in this invention have the following advantages compared with the prior art: This invention establishes a power output trend prediction model and issues early warning signals at the initial stage of changes in sunlight, proactively initiating pre-charging and status self-checks of the energy storage battery, and simultaneously preparing for phase-locked looping and voltage matching on the mains side. Before switching, a real-time monitoring network covering the entire system is constructed to assess bus stability. Then, once conditions are confirmed, a graded reduction in photovoltaic output and synchronous power takeover of the energy storage battery are implemented, achieving a smooth transition between power sources. This method avoids the passive response of traditional systems after voltage drops, effectively eliminating voltage fluctuations and power interruptions during switching, significantly improving power supply continuity and power quality, and ensuring user experience and equipment operational safety. Attached Figure Description

[0016] Figure 1 This is a flowchart of the switching method for the photovoltaic power generation and energy storage system of the present invention; Figure 2 This is a block diagram of the switching system of the photovoltaic power generation and energy storage system of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit 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.

[0018] This invention provides, for example Figure 1The method for switching a photovoltaic power generation and energy storage system, as shown, constructs a multi-level real-time status sensing network and combines dynamic power prediction with a phased power intervention mechanism. This achieves a smooth transition from photovoltaic power supply to energy storage batteries or mains power supply without relying on external energy storage dispatch center intervention, ensuring that the voltage fluctuation at the user end is controlled within ±3% to avoid impacting electrical equipment. Specifically, the method includes the following steps: When a downward trend in photovoltaic power output is detected due to changes in illumination conditions, a photovoltaic power output trend prediction model is established and updated in real time. Specifically, this includes: collecting the output power sequence of the photovoltaic array within a continuous daily cycle; dividing typical power output mode intervals based on the output power sequence; comparing the current power output curve with the mode characteristics in the template library in real time; and correcting the power output trend prediction results by combining real-time meteorological data.

[0019] The process of dividing typical power output mode intervals based on the output power sequence includes: calculating the average power and standard deviation of each interval with a 5-minute sliding window; classifying the intervals into high power, medium power, low power, and extremely low power based on the average power range; establishing a power output mode template library based on the classification results; and performing real-time mode matching based on the template library.

[0020] By establishing a power output mode template library based on historical data and combining it with real-time meteorological information for dynamic matching, the system can identify the degradation trend of photovoltaic power in advance, realize the prediction of changes in power supply capacity, avoid relying on passive response after voltage drop, provide decision-making basis for the active intervention of backup power, and improve the foresight and reliability of switching control.

[0021] In response to the power attenuation warning signal, the energy storage battery pre-charging and status self-check program is initiated, specifically including: reading the current state of charge and health parameters of the energy storage battery; calculating the minimum usable capacity of the energy storage battery based on the state of charge and health parameters; performing battery pack pre-charging to compensate for self-discharge losses; and checking the internal balance and connection reliability of the battery pack. The reading of the current state of charge and health parameters of the energy storage battery is based on the ampere-hour integration method combined with open-circuit voltage calibration.

[0022] After the energy storage battery enters the standby discharge state, the grid-side synchronous phase-locked loop and voltage matching program is started; specifically, it includes: measuring the real-time voltage and frequency of the grid connection point; generating an inverter output reference signal that is in phase and frequency with the grid, and adjusting the inverter output voltage amplitude to approximate the grid level; and verifying the matching status of frequency, phase and voltage based on the generated reference signal and the adjusted voltage amplitude, and establishing standby grid connection conditions.

[0023] By activating the capacity assessment and status self-check of the energy storage battery in advance after receiving the output attenuation warning, and simultaneously completing the frequency, phase and voltage matching preparation on the mains side, the backup power supply is ensured to have the ability to respond in time before the switching is triggered. This effectively avoids switching delays and power outages caused by insufficient battery capacity or unmet grid connection conditions, and improves the system's response speed and operational reliability during power conversion.

[0024] With the mains power synchronized and the energy storage battery ready, a multi-source power supply status monitoring network is constructed to assess bus stability in real time. Specifically, this includes: deploying distributed voltage and current detection nodes to collect electrical parameters from the photovoltaic output terminal, energy storage battery port, mains power access point, DC bus, AC bus, and major load branches; calculating the DC bus voltage fluctuation rate and ripple coefficient based on the sampling data from the detection nodes to determine the stability of the DC side energy supply; analyzing the AC bus frequency offset and harmonic distortion based on the fluctuation rate and ripple coefficient calculation results to assess whether the AC side power quality meets the load operation requirements; and combining the DC bus stability assessment results and the AC bus power quality assessment results to comprehensively determine whether the system is ready to perform subsequent power transfer.

[0025] By constructing a distributed monitoring network covering the entire system and implementing multi-dimensional power quality assessment, the real-time operating status of each power source and bus can be fully grasped before switching. Based on comprehensive criteria, the timing of switching can be confirmed, effectively avoiding voltage oscillations, frequency instability, or equipment abnormalities caused by forced switching under unstable system or substandard power quality conditions, thus ensuring the safety and reliability of the power transfer process.

[0026] After confirming that the bus voltage, frequency, and harmonic parameters meet the switching conditions, a tiered power transfer from photovoltaic power to energy storage batteries is executed. Specifically, this includes: setting a time window and step size for the decrease in photovoltaic output power, determining the total transfer time to be 800 milliseconds and dividing it into eight 100-millisecond adjustment intervals; adjusting the duty cycle of the photovoltaic DC-DC converter based on the time window and step size to reduce the output power, so that the photovoltaic output power gradually decreases according to a preset slope; while the photovoltaic output power decreases, the discharge power of the energy storage battery is simultaneously increased to compensate for the power gap, ensuring that the total input power of the DC bus remains stable; during the power transfer process, the bus voltage deviation is monitored in real time, and the discharge power adjustment ratio of the energy storage battery is dynamically adjusted according to the voltage fluctuation to maintain the bus voltage within ±2% of the nominal value.

[0027] By implementing a stepped decrease in photovoltaic output and a synchronous increase in the discharge power of energy storage batteries, combined with real-time feedback adjustment of bus voltage deviation, a smooth power transfer between power sources is achieved. This effectively suppresses voltage fluctuations and current surges caused by sudden energy injection during the switching process, ensures the stability of DC bus voltage, avoids power outages or power quality degradation at the load end, and improves the continuity of the switching process and the stability of the operation of electrical equipment.

[0028] After the energy storage battery fully assumes the load output, the mains static switch is activated and a dual-source parallel power supply mode is established. Specifically, this includes: confirming that the energy storage battery has assumed the full load power; determining that the photovoltaic power has been completely deactivated and the battery is in an independent and stable power supply state by comparing the matching degree between the total input power of the DC bus and the output power of the energy storage battery; after confirming the independent power supply state of the energy storage battery, a pre-trigger pulse signal is sent to the static switch to cause the thyristor to enter a quasi-conducting state to shorten the closing delay; during the application of the pre-trigger pulse, the phase difference between the mains power and the inverter output voltage is continuously monitored; when both are detected to cross zero simultaneously and have the same polarity, the static switch is closed synchronously to achieve impact-free grid connection; after the static switch is fully turned on, the inverter output is adjusted to achieve power distribution on demand, gradually reducing its output power and transferring the load ratio to the mains side, forming a dual-source parallel power supply mode with the mains power as the main source and the energy storage battery as the auxiliary source.

[0029] By implementing zero-voltage synchronous grid connection of the mains power on the basis of stable independent power supply of the energy storage battery, and combining pre-trigger control and power on-demand allocation strategy, the inrush current and voltage surge at the moment of mains power connection are effectively eliminated, realizing seamless connection of backup power. At the same time, a hybrid power supply structure with mains power as the mains power and energy storage as the coordinator is constructed to improve the economy and stability of the system in long-term operation.

[0030] Under the premise of stable operation of dual-source power supply, the load-side power supply path reconstruction and electrical isolation are performed. After the power path adjustment is completed, the switching completion status is released and the energy-saving operation mode is started.

[0031] By dynamically adjusting the internal power supply path and implementing electrical isolation between power sources after the dual-source power supply is stabilized, the energy transmission structure is optimized, standby losses are reduced, reverse power feedback and circulating current risks are prevented, and the system operating efficiency and safety are improved. At the same time, status information is released in a timely manner and the system switches to energy-saving control mode, enhancing user perception transparency, extending the continuous energy supply time, and achieving a smooth transition from the completion of the switchover to long-term stable operation.

[0032] On the other hand, this invention proposes a switching system for a photovoltaic power generation and energy storage system, such as... Figure 2 The following are included: Photovoltaic array units are used to collect output power sequences and participate in the establishment of photovoltaic power output trend prediction models. The energy storage battery pack is used to initiate pre-charging and status self-check after receiving an output attenuation warning signal; The mains power access port is used to perform synchronous phase-locking and voltage matching after the energy storage battery enters standby mode. A multi-channel power detection network is used to build a monitoring network and assess bus stability after mains power synchronization is completed; The central control unit is used to control the reduction of photovoltaic output, start the grid power connection, reconfigure the power supply path and release the operating status after confirming that the switch is ready; The four-quadrant bidirectional converter is used to adjust the power output during load transfer and to achieve on-demand power distribution during the dual-source parallel phase.

[0033] The overall system architecture includes photovoltaic array units, energy storage battery packs, mains power input ports, a multi-channel power monitoring network, a central control unit, and a four-quadrant bidirectional converter. The photovoltaic array units convert solar energy into DC power during the day and transmit it to the DC bus via a DC-DC converter. The energy storage battery packs are connected to the AC bus via a bidirectional DC-AC converter, allowing them to accept surplus photovoltaic power for charging and discharge to the load when photovoltaic output is insufficient. The mains power input ports are connected to the AC bus via a static switch, serving as a final backup power source. The multi-channel power monitoring network is distributed across the photovoltaic output, battery port, mains input, and load side, continuously collecting electrical parameters such as voltage, current, frequency, and power factor. The central control unit receives data streams from the monitoring network and performs status judgment and switching decisions. The four-quadrant bidirectional converter adjusts the energy flow direction according to instructions, achieving seamless connection between different power sources.

[0034] In addition, the components in the above system are also used to implement other steps of a switching method for a photovoltaic power generation and energy storage system, as follows: Step 1: Establish a photovoltaic power output trend prediction model and update it in real time. This step aims to identify power output degradation trends in advance by fusing historical output data of the photovoltaic array with real-time meteorological information, providing early warning signals for subsequent power switching. Unlike passive response systems that only initiate switching when the voltage drops, this step proactively predicts changes in power generation capacity within the next 5 to 15 minutes, allowing energy storage batteries or grid power to prepare in advance and avoiding power outages caused by response delays.

[0035] Step 1.1: Collect the output power sequence of the photovoltaic array over a continuous daily period: During the initial operation phase of the system, the data acquisition unit is activated to continuously record the DC output power value of the photovoltaic array over at least 7 consecutive daily cycles at a sampling interval of 1 second, forming a time series dataset. ,in The sampling time is indicated in seconds. This sequence covers power output characteristics under various weather conditions, including sunny, cloudy, and rainy days, with particular focus on typical operating conditions such as power rise after sunrise, peak power maintenance at noon, power decay before sunset, and sudden power drops caused by cloud cover. Ambient light intensity is recorded synchronously during the acquisition process. Ambient temperature and array surface temperature This dataset provides foundational data for establishing the correlation between power and environmental variables. It forms the basis for subsequent trend analysis, and its completeness and diversity directly impact prediction accuracy.

[0036] Step 1.2: Divide typical power output mode intervals based on historical power sequences: Using the information obtained in step 1.1 The sequence was processed by segmenting the daily power output curve using the sliding window method, dividing it into intervals of 5 minutes, and calculating the average power within each interval. with standard deviation and according to The numerical range is classified as the "high power range" ( "Medium power range" "Low power range" ) and "extremely low power range" ),in This represents the maximum output power recorded in historical data. By statistically analyzing the time-varying patterns of different intervals under various weather types, a "power output pattern template library" was established. For example, the sunny weather pattern shows a rapid increase in the morning, a long plateau period at midday, and a slow decrease in the evening; while the cloudy and rainy pattern is characterized by generally low output power, frequent fluctuations, and no obvious peak. This template library provides a reference benchmark for subsequent real-time data matching.

[0037] Step 1.3: Real-time comparison of the current output curve with the pattern features in the template library: During the system's daily operation, data is continuously collected at the current moment. The rate of change of power within a 15-minute sliding window was calculated. Cumulative value: ; This formula is used to quantify the severity of power fluctuations. A higher value indicates more unstable lighting conditions. Simultaneously, the initial power of the current window is extracted. End power Average power and power descent slope The above parameters are then compared with the feature vectors of various patterns in the template library using similarity analysis, with Euclidean distance used to measure the matching degree. ; Subscript The corresponding template library This model The smaller the value, the closer the current output trend is to this pattern. Select The simplest pattern is used as a preliminary determination of the current weather type. This matching process is performed every 30 seconds to ensure dynamic tracking of weather evolution.

[0038] Step 1.4: Correct the power output trend forecast results by combining real-time meteorological data: Based on the preliminary model matching results obtained in step 1.3, the precipitation probability for the next hour provided by an external meteorological data source is introduced. Cloud coverage and solar radiation intensity forecast .like or If so, the current mode will be forcibly adjusted to "rainy weather attenuation mode," and it will be predicted that photovoltaic output will drop to below 50% of the current value within the next 10 minutes; if If the trend shows a continuous decline, then the expected duration of the "low power range" will be extended. Conversely, if... However, if the current output is still declining, it is determined to be a natural decay before sunset, and the nighttime switching plan is activated. The revised forecast result is released to the central control unit as an event, marked as "output decay warning signal," along with the expected decay magnitude and time window. This signal becomes the trigger condition for the next step.

[0039] This step achieves forward-looking identification of photovoltaic power output changes by constructing a dual prediction system based on historical data and real-time perception. Data acquisition in step 1.1 provides the factual basis for the entire prediction logic, ensuring that subsequent analysis remains aligned with actual operating conditions. Pattern segmentation in step 1.2 transforms complex continuous power curves into categorizable discrete states, facilitating rapid matching. Real-time comparison in step 1.3 introduces mathematical measurement methods, improving the objectivity and consistency of pattern recognition. Step 1.4, by integrating external meteorological information, compensates for the limitations of relying solely on internal electrical parameters, enhancing the robustness of the prediction.

[0040] Step 2: Start the energy storage battery pre-charge and status self-check program. Upon receiving the "output degradation warning signal," the system immediately initiates preparations for the energy storage battery, ensuring it has independent power supply capability before the photovoltaic output drops below the critical value. This step avoids the risk of switching failure due to insufficient battery SOC (state of charge) or abnormal internal resistance in traditional systems, guaranteeing the immediate availability of backup power.

[0041] Step 2.1: Read the current state of charge and health parameters of the energy storage battery: In response to the warning signal issued in step 1.4, the central control unit sends a status query command to the energy storage management system to obtain the real-time state of charge of the battery pack. (State of Charge) and Health (State of Health). Obtained by combining ampere-hour integration with open-circuit voltage calibration: ; in For the battery's rated capacity, This represents the real-time charging and discharging current (negative for charging, positive for discharging). Coulomb efficiency is dynamically adjusted with temperature and aging degree. Based on the battery's internal resistance With rated internal resistance Ratio estimation: ; in This is an empirical value for the internal resistance at the end of the battery's lifespan. If... If the system enters an alarm state, it will prioritize initiating the mains charging process; otherwise, it will continue with subsequent steps. This judgment ensures that the battery has sufficient energy reserves and output capacity.

[0042] Step 2.2: Calculate the minimum usable capacity of the energy storage battery based on load requirements: Based on the battery status confirmed in step 2.1, further assess its ability to meet load demands over the next 15 minutes. First, obtain the average active power for each time period over the past hour from the load monitoring unit. And, in conjunction with the current list of operating equipment (such as air conditioners, lighting, water heaters, etc.), estimate the expected load for the next 15 minutes. Minimum available capacity required Calculate using the following formula: ; Where 0.25 represents the number of hours corresponding to 15 minutes. This represents the inverter's conversion efficiency (typically taken as 0.92–0.96). If... If the battery capacity is sufficient, it is determined that the battery has enough power; otherwise, the mains power should be switched on in advance to supplement the power supply. This calculation ensures that the battery not only has power, but also has enough power, preventing power outages due to misjudgment of capacity.

[0043] Step 2.3: Perform battery pack pre-charge to compensate for self-discharge losses: Despite the current battery The requirements are met, but considering the self-discharge effect and potential capacity drift caused by temperature changes, the system automatically initiates a pre-charge program. (Set target) This means increasing the current by 5 percentage points to compensate for potential self-discharge losses within the next 15 minutes. Charging current. The charging strategy follows a three-stage approach: first, constant current charging at 0.1C until the cell voltage reaches 3.6V; then, constant voltage charging until the current decreases to 0.02C; finally, float charging begins. Battery temperature is continuously monitored throughout the charging process. ,like If the charging current is reduced to 0.05C, thermal runaway is prevented. This pre-charging process typically lasts 3–8 minutes, after which the battery enters a "standby discharge" state.

[0044] Step 2.4: Check the internal balance and connection reliability of the battery pack: After pre-charging is complete, the system performs a final health check. The voltage of each individual cell is read through the Battery Management System (BMS). Calculate the standard deviation of voltage : ; like Then the active balancing circuit is activated, transferring energy from the high-voltage cell to the low-voltage cell until... Simultaneously, the contact resistance of the battery pack's main circuit is detected. ,like If the connection fails, a "connection error" warning will be issued, and the main contactor will be attempted to be closed again. After all tests pass, the BMS will send a "battery ready" signal to the central control unit, indicating that this step is complete. This check ensures that the battery pack can provide a stable current during discharge, avoiding voltage drops caused by individual cell imbalance or poor contact.

[0045] The core of this step lies in "preparing in advance and verifying thoroughly". Step 2.1, status reading, is the starting point for decision-making, providing an objective basis for subsequent operations; Step 2.2, capacity calculation, directly links battery capacity with load requirements, avoiding "blind preparation"; Step 2.3, pre-charging, is a preventative maintenance measure that improves system redundancy through small energy replenishments; Step 2.4, balancing and connectivity detection, focuses on ensuring physical-level reliability.

[0046] Step 3: Start the mains-side synchronization phase-locked loop and voltage matching program. While the energy storage battery is ready, the system simultaneously initiates the grid connection preparation work. Because the grid has fluctuations in parameters such as frequency, phase, and voltage amplitude, direct grid connection may cause circulating current or inrush current. Therefore, precise alignment of electrical parameters must be completed before the switchover.

[0047] Step 3.1: Measure the real-time voltage and frequency at the mains connection point: After confirming the battery is ready in step 2.4, the system activates the mains voltage sensor and frequency detection circuit to continuously collect the three-phase voltage at the mains connection point. The sampling frequency is not lower than 5kHz. The fundamental frequency of the mains power is extracted based on the zero-crossing detection method. ; in This is the time interval between two consecutive voltage zero-crossings. Simultaneously, calculate the effective values ​​of the three-phase voltages. ; Under normal circumstances It should be 50Hz ± 0.2Hz. The voltage range is 220V ± 10V. If the voltage exceeds this range, the system enters "grid anomaly" mode, delays the switching process, and issues an alarm; otherwise, it proceeds to the next step. This measurement provides a reference parameter for subsequent synchronization operations.

[0048] Step 3.2: Generate an inverter output reference signal that is in phase and frequency with the mains power: Using the measurements obtained in step 3.1 With initial phase The central control unit instructs the inverter control system to generate a synchronization reference signal. : ; in Set as with The target amplitude is equal. This signal serves as the reference waveform for the inverter's PWM modulation, ensuring that its output voltage is consistent with the mains voltage in frequency and phase. The synchronization process employs digital phase-locked loop (PLL) technology, through continuous comparison... and phase difference ,Adjustment angular frequency until This process typically completes within 200ms, achieving fast phase-locked loop (PLL).

[0049] Step 3.3: Adjust the inverter output voltage amplitude to approximate the mains voltage level: After frequency and phase alignment, the inverter output voltage amplitude is further adjusted. This is achieved through voltage closed-loop control and real-time comparison. effective value difference .like Then adjust the PWM modulation ratio proportionally. ; make The amplitude gradually approaches During regulation, the voltage change rate is limited to no more than 1V / ms to prevent overshoot. Furthermore, if this process continues for more than 10 cycles, the voltage amplitude matching is considered complete. This fine adjustment ensures no voltage difference during grid connection and eliminates inrush current.

[0050] Step 3.4: Verify synchronization status and establish standby grid connection conditions: After completing the triple matching of frequency, phase, and amplitude, the system enters the synchronization verification phase. Continuous monitoring. 10 seconds, if both conditions are always met If the inverter is fully synchronized with the mains power, it is considered to be in the open state. At this time, the static switch remains open, but the internal thyristor trigger signal is ready and can be turned on within 10ms after receiving the switching command. The central control unit records the "mains synchronization ready" status, which, together with the "battery ready" signal, serves as a prerequisite for starting the next step. This verification mechanism prevents accidental grid connection under parameter drift conditions.

[0051] This step addresses the "electrical compatibility" issue of mains power connection. Step 3.1, measurement, is the starting point for all synchronization operations, providing real grid parameters; Step 3.2, through phase-locked loop (PLL) technology, achieves frequency and phase alignment, which is the foundation for grid connection; Step 3.3, amplitude regulation, ensures no voltage abrupt changes and eliminates circulating current risks; Step 3.4, continuous verification, provides safety redundancy and prevents transient synchronization loss.

[0052] Step 4: Construct a multi-source power supply status monitoring network and evaluate bus stability in real time. After both energy storage and mains power are put into standby mode, the system establishes a real-time monitoring system covering the entire link, focusing on monitoring the voltage and current dynamics of the DC bus and AC bus, assessing the stability of the current power supply mode, and providing real-time basis for the final switching decision.

[0053] Step 4.1: Deploy distributed voltage and current sensing nodes: After completing mains synchronization in step 3.4, the system activates 12 pre-positioned detection nodes at the photovoltaic output terminal, energy storage battery port, mains connection point, DC bus, AC bus, and main load branches. Each node is equipped with a high-precision Hall sensor and ADC conversion circuit to synchronously acquire voltage at a 10kHz sampling rate. With current The data is transmitted to the central control unit via differential signals to reduce electromagnetic interference. All nodes use a unified timestamp to ensure spatiotemporal consistency of data. This network forms a "panoramic perception" of the entire system, providing a high-resolution data source for condition assessment.

[0054] Step 4.2: Calculate the DC bus voltage fluctuation rate and ripple coefficient: Using the DC bus voltage acquired in step 4.1 Calculate its volatility within a 1-second sliding window. : ; in The nominal DC voltage (e.g., 700V). and The maximum and minimum values ​​within the window are also calculated. The voltage ripple coefficient is also calculated simultaneously. : ; in The effective value of the AC component is extracted using a high-pass filter. If If the signal is positive, it indicates the presence of instability on the DC side (such as photovoltaic MPPT oscillation or sudden load changes), and the system should temporarily postpone switching; otherwise, proceed to the next evaluation stage. This indicator reflects the stability of DC energy supply.

[0055] Step 4.3: Analyze AC bus frequency offset and harmonic distortion: AC bus voltage Perform FFT analysis to extract the fundamental frequency. Calculate its offset relative to 50Hz. .like This indicates that the system's frequency regulation capability is insufficient. The total harmonic distortion (THD) was also calculated. : ; in This is the effective value of the fundamental voltage. For the first Second harmonic components. If This indicates a deterioration in power quality, which may affect sensitive equipment. Both indicators must be within the normal range for the system to be ready for switching. This analysis ensures that the AC power quality meets load requirements.

[0056] Step 4.4: Comprehensive assessment of power supply mode switching readiness status: After completing independent evaluations of the DC and AC sides, the system makes a comprehensive judgment. A switching readiness index is defined. : ; in Weight Once both the "battery ready" and "mains synchronization ready" signals have been confirmed, the central control unit generates a "switchover permission" flag, allowing the process to proceed to the next step. This comprehensive evaluation mechanism balances multi-dimensional stability requirements, preventing misjudgments caused by anomalies in a single indicator.

[0057] This step establishes a "final safety check" mechanism before the switchover. Step 4.1, node deployment, forms the data foundation, ensuring no blind spots in information. Steps 4.2 and 4.3 quantify system stability from DC and AC dimensions, respectively, covering the two major energy transmission paths. Step 4.4, the comprehensive index, integrates multi-source information into a single decision-making basis, improving judgment efficiency.

[0058] After confirming that the system is ready for switching, this step initiates a power reduction process from the photovoltaic array to the energy storage battery to prevent bus voltage instability caused by a sudden power outage. This process employs a phased load reduction strategy, allowing the energy storage battery to gradually take over the load and achieve a smooth transition of energy source.

[0059] Step 5.1: Set the time window and step size for the photovoltaic output power decrease: Based on the "switching permission" flag generated in step 4.4, the central control unit initiates the power transfer procedure and sets the total transfer time. This time period is divided into 8 equal-length intervals, each lasting... Within each interval, the target output power value of the photovoltaic array. Decreasing according to a linear pattern: ; in This is the current interval index. The total number of intervals, This is the measured photovoltaic output power at the start of the transfer. This formula ensures that the photovoltaic output power drops uniformly to zero within 800ms, avoiding voltage surges caused by abrupt power outages. This time window has been experimentally verified to meet both the human eye's perception threshold for light flicker (>50ms) and ensure switching speed.

[0060] Step 5.2: Adjust the duty cycle of the photovoltaic DC-DC converter to reduce the output power: Under the power reduction plan set in step 5.1, the central control unit sends a dynamic duty cycle command to the photovoltaic-side DC-DC converter. The converter operates in a "controlled descent" mode, outside of the maximum power point tracking (MPPT) mode, with its output current... Forced to adjust to the target value: ; in This represents the real-time DC bus voltage. By adjusting the duty cycle of the PWM signal, the actual output current is made to approximate the voltage level. The command is updated every 100ms, forming a stepped decline curve. This process suppresses energy injection from the photovoltaic side, forcing the power required by the load to be supplemented by other power sources, thus creating conditions for the intervention of energy storage batteries.

[0061] Step 5.3: Simultaneously increase the discharge power of the energy storage battery to compensate for the power gap: As photovoltaic output declines, a power deficit occurs at the load end. To maintain bus power balance, energy storage batteries need to increase their discharge power within the same time window. The central control unit sends a discharge command to the bidirectional inverter to increase its output power. Increase according to the following pattern: ; in The initial discharge power of the battery before transfer (typically zero or a small value). The inverter ensures this by adjusting the modulation depth and output current phase. Precise following Because the power changes of photovoltaic cells and batteries are strictly aligned in time, the total input power of the DC bus remains constant, effectively suppressing voltage fluctuations.

[0062] Step 5.4: Monitor bus voltage deviation and dynamically adjust power distribution ratio: During the power transfer process, the DC bus voltage is monitored in real time using the detection nodes deployed in step 4.1. .like If the deviation from the nominal value exceeds ±2%, a dynamic correction mechanism will be activated. Define the voltage deviation amount. ,like This indicates a downward trend in the bus power, requiring a faster rate of increase in battery power; conversely, if... This would slow down the increase in battery output. The revised target battery power is: ; The proportionality coefficient This feedback regulation ensures that even with slight load fluctuations or changes in line impedance, the bus voltage remains stable within a safe range, enabling a seamless transition from photovoltaic power to battery power.

[0063] This process achieves a "soft shutdown" of the main power supply and a "gradual takeover" of the backup power supply. Step 5.1's time planning sets a clear rhythm for the entire transfer process, preventing risks associated with being too fast or too slow. Step 5.2, through active control of the photovoltaic converter, breaks its natural power generation characteristics to achieve on-demand load reduction. Step 5.3's synchronous increase in battery power ensures energy conservation and is the core of seamless switching. Step 5.4's closed-loop correction provides fault tolerance to address uncertainties in actual operation.

[0064] Step Six: Activate the mains static switch and establish a dual-source parallel power supply mode. Once the energy storage battery has fully taken over the load, the system further introduces mains power as a long-term backup power source to extend off-grid operation time and reduce the battery's burden. This step achieves mains power integration without interrupting the power supply through precise triggering of a static switch.

[0065] Step 6.1: Confirm that the energy storage battery has handled the full load power: After the photovoltaic output is reduced to zero in step 5.4, the system first verifies whether the energy storage battery has stably handled the entire load. The total input power of the DC bus is then read. With battery output power Calculate the matching degree: ; like If this continues for more than 200ms, it indicates that the photovoltaic system has completely shut down and the battery is in independent power supply mode. Simultaneously check the AC bus frequency. Check if the frequency is stable at 50Hz ± 0.1Hz to confirm that the inverter's closed-loop control is functioning correctly. This state serves as a prerequisite for mains power connection, preventing the introduction of new variables when the power supply handover is unclear.

[0066] Step 6.2: Send a pre-trigger pulse signal to the static switch: After confirming stable independent battery power supply, the system sends a set of pre-trigger pulses to the mains-side static switch (composed of anti-parallel thyristors). This pulse has a width of 50μs and a period of 10ms, its function being to put the thyristors into a "quasi-conducting" state, reducing their forward blocking voltage. This operation does not fully close the switch, but prepares it for subsequent full conduction, shortening the actual closing delay. The pre-trigger process lasts 100ms, during which the phase difference between the mains power and the inverter output is continuously monitored. Ensure that it remains below 2° to prevent false triggering due to grid drift.

[0067] Step 6.3: Synchronously close the static switch at the voltage zero-crossing point: The common zero-crossing point of the mains voltage and the inverter output voltage is selected as the closing timing. When detected... and When both cross zero and have the same polarity, the central control unit issues a full-conduction command, driving the thyristor gate to apply a continuous current, causing it to... The circuit is fully conductive at all times. Since the voltage difference between the two ends is close to zero at this time, theoretically no inrush current will be generated. After closing, the mains power begins to provide some power to the load, while the energy storage battery continues to maintain its original output, forming a parallel power supply mode between the mains power and the inverter.

[0068] Step 6.4: Adjust the inverter output to achieve power distribution on demand: After the static switch is closed, the system enters the dual-source coordination phase. The central control unit issues a new power distribution command, requiring the inverter to gradually reduce its output power and shift the load proportion to the mains side. The final goal is for the mains to bear 80% of the load and the battery to bear 20%. The inverter adjusts the amplitude and phase of its output current to ensure its active power... Decays exponentially: ; in For initial power, This represents the decay rate constant. Simultaneously, the mains power automatically increases to compensate for the shortfall, the AC bus voltage is dominated by the mains, and the inverter switches to current source mode. This process is completed within 1 second, ultimately forming a hybrid power supply pattern with mains power as the primary source and battery power as the secondary source.

[0069] This step solves the problem of "seamless integration" of backup power. The status confirmation in step 6.1 ensures a clear starting point for operation and avoids multi-source conflicts; the pre-triggering in step 6.2 improves the switching response speed and reduces grid connection delay; the zero-crossing closure in step 6.3 eliminates inrush current from the physical principle; and the power redistribution in step 6.4 optimizes the energy structure.

[0070] Step 7: Perform load-side power supply path reconfiguration and electrical isolation: After the mains power is successfully connected, the internal circuit structure needs to be adjusted to cut off the original photovoltaic path, optimize energy transmission efficiency, and ensure electrical isolation between power sources to prevent reverse feedback or circulating current.

[0071] Step 7.1: Disconnect the main contactor between the photovoltaic array and the DC bus: After confirming stable dual-source power supply in step 6.4, the central control unit issues a command to disconnect the photovoltaic-side main contactor. This contactor is electromagnetically driven, with a breaking time of less than 30ms. Before disconnecting, reconfirm that the photovoltaic output power has returned to zero and the DC-DC converter is in standby mode to prevent arcing. After disconnecting, use an insulation testing device to measure the resistance to ground at the photovoltaic port. ,like If the signal is detected, a leakage fault is identified, and the protection program is activated; otherwise, subsequent operations continue. This completely isolates the photovoltaic branch, reducing standby power consumption.

[0072] Step 7.2: Switch the DC load power supply path to the dedicated energy storage bus: For high-power DC loads such as air conditioners and refrigerators, the original power supply was directly from the DC bus. To improve efficiency, the system switches their power supply path to a dedicated DC bus for energy storage batteries. The battery-side power supply contactor is then closed. At the same time, disconnect the original busbar contactor. During the switching process, the voltage difference between the two power supplies is less than 1V, ensuring that there is no sudden change in the load voltage. After the switching is completed, only small-power devices such as communication and monitoring are retained on the DC bus, reducing line losses and improving the overall energy efficiency of the system.

[0073] Step 7.3: Enable the load classification management strategy with mains power priority: According to the importance and electricity consumption characteristics of the loads, reconfigure the power supply priorities. Primary loads (such as lighting and network equipment) are fixed to be directly supplied by the mains power; secondary loads (such as water heaters and washing machines) are supplied by the mains power when the mains power is normal and automatically switched to the inverter when abnormal; tertiary loads (such as charging piles) are only enabled when there is surplus photovoltaic power or during low electricity price periods. This strategy is executed by the intelligent power distribution unit, and each load circuit is equipped with an independent relay, which can automatically adjust the on / off according to the system status. This measure optimizes the energy utilization structure and reduces unnecessary battery consumption.

[0074] Step 7.4: Verify the electrical isolation status between power supplies: After the path reconstruction is completed, the system performs isolation detection. Measure the insulation resistance between the mains power and the DC bus, and between the energy storage battery and the photovoltaic array respectively. Apply a test voltage using a 500V DC megohmmeter. If the measured resistance is greater than 10MΩ, it is determined that the isolation is qualified. At the same time, monitor the leakage current of each branch. If the leakage current of any loop exceeds 30mA, trigger the leakage protection and give an alarm. This verification ensures that each power supply operates independently without interference and complies with safety specifications.

[0075] This step completes the "dynamic reorganization" of the system architecture. The isolation in Step 7.1 cuts off the failed power supply, enhancing safety; the path optimization in Step 7.2 reduces transmission losses and improves efficiency; the hierarchical management in Step 7.3 achieves refined allocation of energy; and the verification in Step 7.4 ensures the reliability of the renovated system.

[0076] Step Eight: Publish the completion status of the switching and start the energy-saving operation mode After completing all hardware operations, the system enters a new operation stage, publishes status information, and adjusts control parameters to adapt to the long-term standby power supply mode, saving energy to the greatest extent.

[0077] Step 8.1: Push a power supply mode change notice to the user terminal: Send a message to the user terminals in the homestay through the local wireless network or display screen: "The power supply has been automatically switched to the mains power / energy storage hybrid mode, and your electricity consumption is not affected." The notice content includes the current main power supply type, the estimated battery life (based on the battery SOC and load level), and recommended energy-saving measures (such as reducing the use of high-power devices). This information enhances the transparency of user perception and avoids doubts caused by unknown switching.

[0078] Step 8.2: Record the entire process log of this handover event: The system automatically generates a switchover log, including start and end times, triggering reasons (e.g., "insufficient photovoltaic output due to rainy weather"), execution status at each stage, and key parameter change curves (e.g., ...). The logs include the operator's confirmation information (if any). The logs are encrypted and stored locally, and can be uploaded to the operations and maintenance platform via a remote interface for subsequent analysis and system optimization.

[0079] Step 8.3: Adjust inverter control parameters to reduce standby power consumption: In hybrid power supply mode, the inverter does not need to operate at full load. The system switches it to "light load high efficiency" mode, reducing the PWM switching frequency from 20kHz to 10kHz to reduce switching losses; at the same time, it enables intermittent operation mode, pausing part of the control circuit when the load is stable and periodically waking up for detection. Actual measurements show that this can reduce the inverter's own power consumption by more than 40% and extend the duration of available energy.

[0080] Step 8.4: Start the photovoltaic power generation recovery monitoring and automatic restart program: The system has not completely abandoned photovoltaic resources. It continuously monitors solar irradiance. ,when If this continues for more than 10 minutes, the weather is considered to have improved. At this point, the adjustment of the mains power supply ratio is paused, and the photovoltaic array self-check is initiated first. After confirming that there are no faults, the photovoltaic power supply is gradually restored in reverse order, eventually returning to the solar priority mode. The entire process requires no manual intervention, maximizing energy utilization.

[0081] This step marks the successful completion of the switchover process and the beginning of a new operating cycle. Step 8.1, information dissemination, enhances the human-computer interaction experience; Step 8.2, logging provides a basis for system maintenance; Step 8.3, parameter optimization improves long-term operating efficiency; and Step 8.4, recovery monitoring, ensures the system has self-healing capabilities.

[0082] In summary, this invention establishes a power output trend prediction model and issues early warning signals at the initial stage of changes in sunlight, initiates pre-charging and status self-checking of the energy storage battery in advance, and simultaneously prepares for phase-locking and voltage matching on the mains side. Before switching, a real-time monitoring network covering the entire system is constructed to assess the stability of the bus. Then, after confirming that the conditions are met, the photovoltaic power output is reduced in stages and the energy storage battery takes over synchronously, thus achieving a smooth transition between power sources.

[0083] This method avoids the passive response of traditional systems after the voltage has dropped, effectively eliminates voltage fluctuations and power outages during the switching process, significantly improves power supply continuity and power quality, and ensures user power experience and equipment operation safety.

[0084] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A switching method of a photovoltaic power generation energy storage system, characterized by, The application relates to a photovoltaic power supply system switching method. When a light condition change is detected to cause a photovoltaic output decline trend, a photovoltaic output trend prediction model is established and updated in real time; In response to an output attenuation early warning signal, a storage battery pre-charging and state self-checking program is started, after the storage battery enters a standby discharging state, a power grid side synchronous phase locking and voltage matching program is started; On the basis that the power grid is synchronized and the storage battery is ready, a multi-source power supply state monitoring network is constructed and the bus stability is evaluated in real time; After confirming that bus voltage, frequency and harmonic indicators meet switching conditions, a graded power transfer from photovoltaic power supply to the storage battery is performed; After the storage battery completely bears the load output, a power grid static switch is activated and a dual-source parallel power supply mode is established; On the premise that the dual-source power supply is stably operated, a load side power supply path reconstruction and electrical isolation are performed, after the power supply path adjustment is completed, a switching completion state is issued and an energy-saving operation mode is started.

2. The switching method of a photovoltaic power generation and energy storage system according to claim 1, characterized in that: The method comprises the following steps: An output power sequence of a photovoltaic array in a continuous daily cycle is collected; Typical output mode intervals are divided based on the output power sequence; Real-time comparison is made between a current output curve and mode characteristics in a template library, and real-time meteorological data are used to correct the output trend prediction result.

3. The switching method of a photovoltaic power generation and energy storage system according to claim 2, characterized in that: The method comprises the following steps: An average power and a standard deviation of each interval are calculated with a 5-minute sliding window; According to the average power range, the intervals are classified into high-power intervals, medium-power intervals, low-power intervals and extremely low-power intervals; An output mode template library is established based on the classification result, and real-time mode matching is performed according to the template library.

4. The switching method of a photovoltaic power generation and energy storage system according to claim 1, characterized in that: The method comprises the following steps: Current state of charge and health degree parameters of the storage battery are read; The minimum available capacity of the storage battery is calculated based on the state of charge and health degree parameters; Battery pack pre-charging is performed to compensate for self-discharge loss, and the internal balance and connection reliability of the battery pack are detected.

5. The switching method of a photovoltaic power generation and energy storage system according to claim 4, characterized in that: The current state of charge and health degree parameters of the storage battery are obtained based on the ampere-hour integration method combined with open-circuit voltage calibration.

6. The switching method of a photovoltaic power generation and energy storage system according to claim 1, characterized in that: The method comprises the following steps: Real-time voltage and frequency of a power grid access point are measured; An inverter output reference signal with the same frequency and phase as the power grid is generated based on the voltage and frequency, and the inverter output voltage amplitude is adjusted to approximate the power grid level; Based on the generated reference signal and the adjusted voltage amplitude, the matching state of frequency, phase and voltage is verified, and a standby grid-connected condition is established.

7. The switching method of a photovoltaic power generation and energy storage system according to claim 1, characterized in that: The method comprises the following steps: Distributed voltage and current detection nodes are deployed to collect electrical parameters of photovoltaic output ends, storage battery ports, power grid access points, direct-current buses, alternating-current buses and main load branches; Direct-current bus voltage fluctuation rate and ripple coefficient are calculated based on sampling data of the detection nodes to judge the stability of direct-current side energy supply; According to the calculation results of the fluctuation rate and the ripple coefficient, frequency offset and harmonic distortion of the alternating-current bus are analyzed to evaluate whether the alternating-current side power quality meets the load operation requirements; The DC bus stability judgment result and the AC bus power quality evaluation result are combined to comprehensively determine whether the system has conditions to perform subsequent power transfer.

8. The switching method of a photovoltaic power generation and energy storage system according to claim 1, characterized in that: The executing the hierarchical power transfer from the photovoltaic power supply to the energy storage battery includes: A time window and a step size of photovoltaic output power reduction are set, the total transfer time is determined as 800 milliseconds and divided into 8 adjustment intervals of 100 milliseconds; Based on the time window and the step size, the duty cycle of the photovoltaic DC-DC converter is adjusted to reduce the output power, so that the photovoltaic output power gradually decreases at a preset slope; At the same time of the photovoltaic output power reduction, the discharge power of the energy storage battery is simultaneously increased to compensate for the power gap, so as to ensure that the total input power of the DC bus is maintained stable; During the power transfer process, the bus voltage deviation is monitored in real time, and the discharge power adjustment proportion of the energy storage battery is dynamically corrected according to the voltage fluctuation to maintain the bus voltage within ±2% of the nominal value.

9. The switching method of a photovoltaic power generation and energy storage system according to claim 1, characterized in that: The activating the static switch of the commercial power and establishing the dual-source parallel power supply mode includes: Confirming that the energy storage battery has assumed all load power, determining that the photovoltaic has completely exited and the battery is in an independent stable power supply state by comparing the matching degree of the total input power of the DC bus and the output power of the energy storage battery; After the independent power supply state of the energy storage battery is confirmed, a pre-trigger pulse signal is sent to the static switch, so that the thyristor enters a quasi-conduction state to shorten the closing delay; During the pre-trigger pulse application period, the phase difference between the commercial power and the inverter output voltage is continuously monitored, and when it is detected that both cross zero points at the same time and the polarities are consistent, the static switch is closed synchronously to realize non-impact grid connection; After the static switch is fully turned on, the inverter output is adjusted to realize power on-demand distribution, gradually reducing its output power and transferring the load proportion to the commercial power side to form a dual-source parallel power supply mode with the commercial power as the main source and the energy storage battery as the auxiliary source.

10. A switching system for a photovoltaic power generation and energy storage system for implementing the method according to any one of claims 1 to 9, characterized in that: It includes: A photovoltaic array unit for collecting output power sequences and participating in establishing a photovoltaic output trend prediction model; An energy storage battery group for starting pre-charging and state self-checking after receiving an output attenuation warning signal; A commercial power access port for performing synchronous phase locking and voltage matching after the energy storage battery enters a standby state; A multi-channel power detection network for building a monitoring network and evaluating bus stability after the commercial power synchronization is completed; A central control unit for controlling photovoltaic output reduction, starting commercial power access, reconstructing a power supply path, and issuing an operating state after confirming that the switching is ready; A four-quadrant bidirectional conversion device for adjusting power output during load transfer and realizing power on-demand distribution in the dual-source parallel stage.

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