Energy efficiency analysis method and system for low-voltage industrial and commercial energy storage system

Abstract

The invention belongs to the technical field of power consumption management, and particularly relates to an energy efficiency analysis method and system for a low-voltage industrial and commercial energy storage system, and the method comprises the steps: recognizing the station comprehensive loss of the low-voltage industrial and commercial energy storage system, including the DC side battery charging and discharging loss, the AC side power conversion system loss, and the auxiliary equipment and line loss; according to the invention, the comprehensive evaluation of the energy efficiency of the energy storage system is realized by identifying the station comprehensive loss of the low-voltage industrial and commercial energy storage system, including the DC side battery charging and discharging loss, the AC side power conversion system loss and the auxiliary equipment and line loss. The comprehensive evaluation avoids the limitation that only a single efficiency index is concerned in a traditional method, so that the energy efficiency analysis result is more accurate and reliable.

Description

Technical Field

[0001] The present invention belongs to the technical field of electricity management, and in particular relates to an energy efficiency analysis method and system for a low-voltage industrial and commercial energy storage system. Background Art

[0002] In the field of industrial and commercial energy storage, the user-side energy storage market has developed rapidly, becoming a key area for commercial energy storage applications. Low-voltage access industrial and commercial energy storage projects, due to their small capacity and flexible deployment, place higher demands on system economy, safety, and intelligence. However, the quality of energy storage products currently on the market varies, as do their energy efficiency control levels. Some manufacturers engage in false labeling of energy efficiency, and their evaluation methods often focus on a single efficiency metric, ignoring actual operating factors such as standby losses and auxiliary power consumption. This results in significant deviations between actual user benefits and expectations.

[0003] Furthermore, existing energy efficiency analysis methods lack the time dimension and integrity of energy efficiency factors. They often employ static assessments within fixed timeframes and lack dynamic energy efficiency tracking across multiple timescales. Furthermore, due to the potential for inconsistent SOC start and end values ​​during energy storage unit operation, traditional methods fail to fully account for the energy disparity caused by this factor, leading to discrepancies between energy efficiency assessment results and actual operating conditions. Summary of the Invention

[0004] In view of the defect in the existing technology that traditional energy efficiency evaluation methods focus on a single efficiency indicator and ignore energy consumption items such as standby loss and auxiliary power consumption in actual operation, resulting in a large deviation between users' actual benefits and expectations, the present invention provides an energy efficiency analysis method and system for low-voltage industrial and commercial energy storage systems to solve the above technical problems.

[0005] In a first aspect, the present invention provides an energy efficiency analysis method for a low-voltage industrial and commercial energy storage system, comprising: Step S1: Obtaining the comprehensive site losses of the low-voltage industrial and commercial energy storage system, including DC-side battery charging and discharging losses, AC-side power conversion system losses, and auxiliary equipment and line losses; Step S2: Acquire the rated capacity and operating data of each level of the low-voltage industrial and commercial energy storage system. The operating data includes the total charge and discharge capacity of the station, the charge and discharge capacity of the AC-side power conversion system, the charge and discharge capacity of the DC-side battery cluster, and the corresponding SOC values ​​of each. Step S3: Based on the acquired comprehensive site losses, the rated capacities of each level of the low-voltage industrial and commercial energy storage system, and operational data, a four-dimensional energy efficiency model is defined, covering the site, DC-side battery charging and discharging, auxiliary equipment and lines, and AC-side power conversion system. Each dimensional model includes a loss model, a loss rate model, and an efficiency model. Step S4: Identify the SOC differences corresponding to each dimensional model at the start and end of the evaluation period, and modify each dimensional model according to the change direction of the SOC difference; Step S5: Based on the revised four-dimensional energy efficiency model, calculate the energy efficiency indicators under the daily, weekly, monthly, and annual evaluation cycles, and generate an energy efficiency trend curve; Step S6: Set a lower threshold for the site efficiency, DC side charging and discharging efficiency, and AC side power conversion system efficiency in the energy efficiency index, and set an upper threshold for the auxiliary equipment loss rate in the energy efficiency index. When any parameter exceeds the corresponding threshold, a positioning warning is triggered.

[0006] A further improvement of this technical solution is that the steps of obtaining the comprehensive site loss of the low-voltage industrial and commercial energy storage system include: Step S1.1, the DC side battery charge and discharge loss comes from the electric energy heat loss caused by the internal resistance of the battery cell during the charge and discharge process; Step S1.2: The AC side power conversion system loss is derived from the switching loss generated by the power switching device during operation; Step S1.3: The auxiliary equipment and line losses include the power consumption of the monitoring system, the power consumption of the lighting, the energy consumption of the temperature control system and the resistance loss of the power line.

[0007] A further improvement of this technical solution is that the specific method of obtaining the operating data in step S2 includes: Step S2.1: Read the accumulated forward active energy and reverse active energy at the connection point between the energy storage station and the grid in the low-voltage industrial and commercial energy storage system, and calculate the difference between the start and end readings of the evaluation period as the total charge and discharge capacity of the station; read the rated capacity corresponding to the station in the low-voltage industrial and commercial energy storage system; Step S2.2, obtaining the cumulative charge and discharge monitoring value of each AC side power conversion system; reading the rated capacity corresponding to each AC side power conversion system; Step S2.3, collecting the cumulative charge and discharge amount of each battery cluster; reading the rated capacity corresponding to each battery cluster; and identifying the real-time SOC value of each battery cluster during the evaluation period; Step S2.4: Calculate the SOC values ​​of the station and the AC-side power conversion system based on the SOC values ​​of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the station and the rated capacity of the AC-side power conversion system.

[0008] A further improvement of this technical solution is that step S2.4 includes: The formula for calculating the corresponding SOC value of the station based on the SOC value of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the station is: ; in, is the SOC value corresponding to the station; N is the total number of battery clusters; is the SOC value of the i-th battery cluster; is the rated capacity of the i-th battery cluster; is the rated capacity of the station; The formula for calculating the corresponding SOC value of the AC side power conversion system based on the SOC value of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the AC side power conversion system, is: ; in, is the SOC value corresponding to the AC side power conversion system; is the rated capacity of the AC side power conversion system.

[0009] A further improvement of this technical solution is that step S3 includes: Step S3.1: Based on the total charge and discharge capacity of the station, construct a station-level energy efficiency model that includes the following three elements: Station loss model: The difference between the station charging amount and the total discharge amount is taken as the station loss; Station efficiency model: The ratio of the station's discharge capacity to the charge capacity is taken as the station efficiency; Station loss rate model: The ratio of station loss to station charging volume is taken as the station loss rate; Step S3.2: Based on the charge and discharge capacity of the DC-side battery cluster, construct a DC-side battery charge and discharge dimension energy efficiency model that includes the following three elements: DC side loss model: The difference between the charge and discharge capacity of the DC side battery cluster is used as the DC side battery cluster loss; DC side efficiency model: The ratio of the discharge capacity to the charge capacity of the DC side battery cluster is used as the DC side charge and discharge efficiency; DC side loss rate model: The ratio of the DC side battery cluster loss to the DC side battery cluster charge is used as the DC side battery cluster loss rate; Step S3.3: Based on the charge and discharge capacity of the AC power conversion system, construct an AC power conversion system dimensional energy efficiency model including the following three elements: AC side loss model: The difference between the AC side power conversion system charge, the AC side power conversion system discharge, and the DC side battery cluster loss is taken as the AC side power conversion system loss. AC side efficiency model: The ratio of the discharge capacity of the AC side power conversion system to the charge capacity of the AC side power conversion system and the DC side charge and discharge efficiency is used as the AC side power conversion system efficiency; AC side loss rate model: The ratio of the AC side power conversion system loss to the station charging capacity is used as the AC side power conversion system loss rate; Step S3.4: Based on the site losses, DC-side battery cluster losses, and AC-side power conversion system losses, an auxiliary equipment and line-level energy efficiency model is constructed, which includes the following three elements: Auxiliary equipment and line loss model: The difference between the station loss and the DC side battery cluster loss and the AC side power conversion system loss is used as the auxiliary equipment and line loss; Auxiliary equipment and line loss rate model: The ratio of auxiliary equipment and line loss to the station charging volume is used as the auxiliary equipment and line loss rate; Auxiliary equipment and line efficiency model: The ratio of the station efficiency to the DC side charging and discharging efficiency and the AC side power conversion system efficiency is used as the auxiliary equipment and line efficiency.

[0010] A further improvement of this technical solution is that step S4 includes: Step S4.1, identifying the SOC values ​​corresponding to the station, the DC-side battery cluster, and the AC-side power conversion system at the start and end times of the evaluation cycle; Step S4.2: Determine the correction direction based on the identified SOC value: If the SOC value at the end time is greater than the SOC value at the start time, it indicates that the low-voltage industrial and commercial energy storage system is net charged during the evaluation period, and the excess stored energy needs to be deducted from the charge amount; If the SOC value at the end time is less than the SOC value at the start time, it indicates that the low-voltage industrial and commercial energy storage system has a net discharge during the evaluation period, and the excess energy needs to be deducted from the discharge amount; If the SOC value at the end time is equal to the SOC value at the start time, no correction is required.

[0011] A further improvement of this technical solution is that step S5 includes: Step S5.1: Based on the revised four-dimensional energy efficiency model, calculate the station efficiency, DC side charging and discharging efficiency, AC side power conversion system efficiency, and auxiliary equipment and line loss rate for each evaluation period, including daily, weekly, monthly, and annual evaluation periods; the calculated station efficiency, DC side charging and discharging efficiency, AC side power conversion system efficiency, and auxiliary equipment and line loss rate serve as energy efficiency indicators for the corresponding dimensional model; Step S5.2: Using the evaluation period as the horizontal axis and each energy efficiency indicator as the vertical axis, draw the station efficiency trend curve, the DC side charging and discharging efficiency trend curve, the AC side power conversion system efficiency trend curve, and the auxiliary equipment and line loss rate trend curve; Step S5.3: By comparing the slope changes of the curves of adjacent cycles, the continuous degradation trend of the energy efficiency index is identified, and the degradation starting cycle is located.

[0012] A further improvement of this technical solution is that step S6 includes: Step S6.1: Set independent lower thresholds for the energy efficiency indicators of the site efficiency, DC battery charge and discharge efficiency, and AC power conversion system efficiency; and set independent upper thresholds for the auxiliary equipment and line loss rates. Step S6.2: Perform real-time comparison of each energy efficiency indicator within each evaluation cycle, and when any energy efficiency indicator exceeds the corresponding threshold, locate the specific level of the abnormal source corresponding to the exceeded energy efficiency indicator: If it is a site-level anomaly, the site will be located at the entire low-voltage industrial and commercial energy storage system; If the DC side is abnormal, locate the battery cluster number; If the AC side is abnormal, locate the number of the power conversion system; If the auxiliary equipment is abnormal, locate the temperature control subsystem / monitoring subsystem in the low-voltage industrial and commercial energy storage system.

[0013] A further improvement of the technical solution is that step S6 also includes: pushing the positioning result and the calculated over-limit energy efficiency index data to a remote terminal for display and storage, and triggering an audible and visual alarm.

[0014] In a second aspect, the present invention provides an energy efficiency analysis system for a low-voltage industrial and commercial energy storage system, comprising: The loss acquisition module is used to obtain the comprehensive site losses of low-voltage industrial and commercial energy storage systems, including DC-side battery charging and discharging losses, AC-side power conversion system losses, and auxiliary equipment and line losses. The data acquisition module is used to obtain the rated capacity and operating data of each level of the low-voltage industrial and commercial energy storage system. The operating data includes the total charge and discharge capacity of the station, the charge and discharge capacity of the AC side power conversion system, the charge and discharge capacity of the DC side battery cluster, and the corresponding SOC value of each; The energy efficiency model construction module is used to define a four-dimensional energy efficiency model covering the station, DC-side battery charging and discharging, auxiliary equipment and lines, and AC-side power conversion system based on the acquired comprehensive station losses, rated capacity of each layer of the low-voltage industrial and commercial energy storage system, and operating data. Each dimensional model includes a loss model, a loss rate model, and an efficiency model. The energy efficiency model correction module is used to identify the SOC differences corresponding to each dimensional model at the start and end of the evaluation period, and to correct each dimensional model according to the direction of change of the SOC difference; Energy efficiency index calculation module, which is used to calculate energy efficiency indicators under daily, weekly, monthly and annual evaluation cycles based on the revised four-dimensional energy efficiency model, and generate energy efficiency trend curves; The energy efficiency warning module is used to set lower thresholds for the site efficiency, DC side charging and discharging efficiency, and AC side power conversion system efficiency in the energy efficiency indicators, and set upper thresholds for the auxiliary equipment loss rate in the energy efficiency indicators. When any parameter exceeds the corresponding threshold, a positioning warning is triggered.

[0015] The beneficial effects of the present invention are: This method comprehensively evaluates the energy efficiency of low-voltage industrial and commercial energy storage systems by capturing their comprehensive losses, including DC battery charge and discharge losses, AC power conversion system losses, and auxiliary equipment and line losses. This comprehensive assessment avoids the limitations of traditional methods that focus on a single efficiency metric, resulting in more accurate and reliable energy efficiency analysis results.

[0016] The present invention supports energy efficiency analysis in multiple time dimensions (such as day, week, month, and year) and can dynamically track energy efficiency changes of the energy storage system. This dynamic energy efficiency tracking mechanism helps to detect energy efficiency anomalies in a timely manner.

[0017] To address the problem of inconsistent SOC start and end values ​​that may occur during the operation of energy storage units, the present invention identifies the SOC differences corresponding to each dimensional model at the start and end times of the evaluation period, and corrects each dimensional model according to the direction of change of the SOC difference, thereby avoiding the energy difference caused by SOC offset and ensuring the accuracy and credibility of the energy efficiency evaluation results.

[0018] The present invention sets independent lower thresholds for the energy efficiency indicators of site efficiency, DC-side charging and discharging efficiency, and AC-side power conversion system efficiency, and sets independent upper thresholds for the auxiliary equipment and line loss rates. When any energy efficiency indicator exceeds the corresponding threshold, the system can immediately trigger a positioning warning and locate the specific level of the abnormal source corresponding to the exceeded energy efficiency indicator. This precise warning mechanism helps operation and maintenance personnel quickly locate the problem and take appropriate measures to repair it, thereby ensuring the safe and stable operation of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 A schematic flow chart of a method according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic block diagram of an industrial and commercial energy storage station according to an embodiment of the present invention.

[0022] Figure 3 A schematic block diagram of a system according to an embodiment of the present invention.

[0023] Figure 4 A schematic diagram of the structure of a terminal provided by an embodiment of the present invention.

[0024] 210 is a loss identification module, 220 is a data acquisition module, 230 is an energy efficiency model construction module, 240 is an energy efficiency model correction module, 250 is an energy efficiency index calculation module, and 260 is an energy efficiency early warning module. DETAILED DESCRIPTION

[0025] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the specific embodiments. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0027] The energy efficiency analysis method for a low-voltage industrial and commercial energy storage system provided by an embodiment of the present invention is executed by a computer device. Accordingly, the energy efficiency analysis system for a low-voltage industrial and commercial energy storage system runs in the computer device.

[0028] Figure 1 is a schematic flow chart of a method according to an embodiment of the present invention. Figure 1 The execution entity can be an energy efficiency analysis system for a low-voltage industrial and commercial energy storage system. According to different needs, the order of the steps in the flowchart can be changed, and some steps can be omitted.

[0029] like Figure 1 As shown, the method includes: Step S1: Obtaining the comprehensive site losses of the low-voltage industrial and commercial energy storage system, including DC-side battery charging and discharging losses, AC-side power conversion system losses, and auxiliary equipment and line losses; Step S2: Acquire the rated capacity and operating data of each level of the low-voltage industrial and commercial energy storage system. The operating data includes the total charge and discharge capacity of the station, the charge and discharge capacity of the AC-side power conversion system, the charge and discharge capacity of the DC-side battery cluster, and the corresponding SOC values ​​of each. Step S3: Based on the acquired comprehensive site losses, the rated capacities of each level of the low-voltage industrial and commercial energy storage system, and operational data, a four-dimensional energy efficiency model is defined, covering the site, DC-side battery charging and discharging, auxiliary equipment and lines, and AC-side power conversion system. Each dimensional model includes a loss model, a loss rate model, and an efficiency model. Step S4: Identify the SOC differences corresponding to each dimensional model at the start and end of the evaluation period, and modify each dimensional model according to the change direction of the SOC difference; Step S5: Based on the revised four-dimensional energy efficiency model, calculate the energy efficiency indicators under the daily, weekly, monthly, and annual evaluation cycles, and generate an energy efficiency trend curve; Step S6: Set a lower threshold for the site efficiency, DC side charging and discharging efficiency, and AC side power conversion system efficiency in the energy efficiency index, and set an upper threshold for the auxiliary equipment loss rate in the energy efficiency index. When any parameter exceeds the corresponding threshold, a positioning warning is triggered.

[0030] To facilitate understanding of the present invention, the energy efficiency analysis method for a low-voltage industrial and commercial energy storage system provided by the present invention is further described below based on the principles of the energy efficiency analysis method for a low-voltage industrial and commercial energy storage system of the present invention and combined with the process of performing energy efficiency analysis on the low-voltage industrial and commercial energy storage system in the embodiment.

[0031] Specifically, the steps for obtaining the comprehensive site loss of the low-voltage industrial and commercial energy storage system include: Step S1.1, the DC side battery charge and discharge loss comes from the electric energy heat loss caused by the internal resistance of the battery cell during the charge and discharge process; Step S1.2: The AC side power conversion system loss is derived from the switching loss generated by the power switching device during operation; Step S1.3: The auxiliary equipment and line losses include the power consumption of the monitoring system, the power consumption of the lighting, the energy consumption of the temperature control system and the resistance loss of the power line.

[0032] Through detailed monitoring and analysis of battery clusters in energy storage stations, it was discovered that the internal resistance of the battery cells causes heat loss during the charge and discharge process. In specific implementation, high-precision current and voltage sensors are used to collect real-time current and voltage data from the battery cluster during charge and discharge. Combined with the battery cell internal resistance parameters, the heat loss during each charge and discharge process is calculated to determine the specific value of the DC-side battery charge and discharge losses.

[0033] In the AC power conversion system (PCS), losses primarily come from switching losses incurred by power switching devices during operation. To accurately identify these losses, a high-speed data acquisition system is used to perform high-frequency sampling of the PCS's power switching devices, recording the voltage and current waveforms during their switching processes. By analyzing these waveform data and combining them with the switching device's electrical characteristics, the losses incurred during each switching action are calculated, and the total losses of the AC power conversion system are then summarized.

[0034] Auxiliary equipment and line losses include monitoring system power consumption, lighting power consumption, temperature control system energy consumption, and power line resistance losses. During implementation, individual metering is performed on auxiliary equipment such as the monitoring system, lighting equipment, and temperature control system within the energy storage site, and their power consumption data is recorded during operation. Furthermore, the power line resistance parameters and current data are used to calculate the power line resistance losses. By summarizing these loss data, the total auxiliary equipment and line losses can be calculated.

[0035] By identifying DC-side battery charge and discharge losses, AC-side power conversion system losses, and auxiliary equipment and line losses, this method can more accurately assess the overall energy efficiency of energy storage sites. This helps operators and maintenance personnel promptly understand the energy efficiency status of the energy storage system and provides a reliable basis for optimizing operational strategies.

[0036] In addition, the specific method of obtaining the operating data in step S2 includes: Step S2.1: Read the accumulated forward active energy and reverse active energy at the connection point between the energy storage station and the grid in the low-voltage industrial and commercial energy storage system, and calculate the difference between the start and end readings of the evaluation period as the total charge and discharge capacity of the station; read the rated capacity corresponding to the station in the low-voltage industrial and commercial energy storage system; Step S2.2, obtaining the cumulative charge and discharge monitoring value of each AC side power conversion system; reading the rated capacity corresponding to each AC side power conversion system; Step S2.3, collecting the cumulative charge and discharge amount of each battery cluster; reading the rated capacity corresponding to each battery cluster; and identifying the real-time SOC value of each battery cluster during the evaluation period; Step S2.4: Calculate the SOC values ​​of the station and the AC-side power conversion system based on the SOC values ​​of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the station and the rated capacity of the AC-side power conversion system.

[0037] A typical embodiment involves an industrial and commercial energy storage station. For this example, please refer to the attached Figure 2 The station includes two electric meters and four integrated energy storage cabinets. Each integrated cabinet consists of a PCS, a battery cluster and auxiliary equipment.

[0038] The station's charge and discharge capacity is measured from the meter between the energy storage station and the grid, representing the sum of the data from Meter 1 and Meter 2. The accumulated positive and negative active energy on the meter represents the cumulative charge and discharge capacity of the station since commissioning. The charge and discharge capacity during the evaluation period is the difference between the accumulated positive and negative active energy readings from the start and end times.

[0039] The charge and discharge data on the AC side of the energy storage cabinet is obtained from the power station monitoring system's monitoring of the PCS equipment. The charge and discharge data on the AC side during the evaluation period is the difference between the cumulative charge and discharge data points at the start and end times, including PCS1, PCS2, PCS3, and PCS4.

[0040] The DC-side charge and discharge data of the energy storage cabinet is measured from the power station monitoring system's monitoring of the battery cluster equipment. The DC-side charge and discharge data for the evaluation period is the difference between the cumulative charge and discharge data for the battery clusters 1, 2, 3, and 4 during the start and end time periods.

[0041] Wherein, step S2.4 includes: Step S2.41: Based on the SOC value of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the station, the formula for calculating the corresponding SOC value of the station is: ; in, is the SOC value corresponding to the station; N is the total number of battery clusters; is the SOC value of the i-th battery cluster; is the rated capacity of the i-th battery cluster; is the rated capacity of the station; Step S2.42: Based on the SOC value of each battery cluster and its corresponding rated capacity, and the rated capacity of the AC side power conversion system, the formula for calculating the corresponding SOC value of the AC side power conversion system is: ; in, is the SOC value corresponding to the AC side power conversion system; is the rated capacity of the AC side power conversion system.

[0042] This invention directly reads monitoring data from the energy storage station's electricity meters (Meter 1 and Meter 2), PCS equipment, and battery clusters at the grid connection point, eliminating errors caused by manual meter reading or estimation. For example, the total charge and discharge capacity at the station is directly calculated by accumulating the difference in forward and reverse active energy over the evaluation period, ensuring objective and accurate data. Furthermore, data collection spans a three-tiered architecture: station, PCS, and battery cluster, forming a complete data chain and providing a foundation for multi-level energy efficiency analysis.

[0043] By calculating the SOC value corresponding to the station based on the SOC value and rated capacity of each battery cluster and the rated capacity of the station, this method can more comprehensively and accurately assess the energy status of the entire energy storage station. This helps operation and maintenance personnel understand the energy storage level of the station in real time, providing a reliable basis for subsequent charge and discharge scheduling, energy management, etc. Similarly, for the AC-side power conversion system, calculating its SOC (State of Charge, also known as the remaining capacity) value based on the relevant parameters of each battery cluster can accurately grasp the energy status of the subsystem and ensure stable system operation.

[0044] In addition, step S3 includes: Step S3.1: Based on the total charge and discharge capacity of the station, construct a station-level energy efficiency model that includes the following three elements: Station loss model: The difference between the station charging amount and the total discharge amount is taken as the station loss; Station efficiency model: The ratio of the station's discharge capacity to the charge capacity is taken as the station efficiency; Station loss rate model: The ratio of station loss to station charging volume is taken as the station loss rate; Step S3.2: Based on the charge and discharge capacity of the DC-side battery cluster, construct a DC-side battery charge and discharge dimension energy efficiency model that includes the following three elements: DC side loss model: The difference between the charge and discharge capacity of the DC side battery cluster is used as the DC side battery cluster loss; DC side efficiency model: The ratio of the discharge capacity to the charge capacity of the DC side battery cluster is used as the DC side charge and discharge efficiency; DC side loss rate model: The ratio of the DC side battery cluster loss to the DC side battery cluster charge is used as the DC side battery cluster loss rate; Step S3.3: Based on the charge and discharge capacity of the AC power conversion system, construct an AC power conversion system dimensional energy efficiency model including the following three elements: AC side loss model: The difference between the AC side power conversion system charge, the AC side power conversion system discharge, and the DC side battery cluster loss is taken as the AC side power conversion system loss. AC side efficiency model: The ratio of the discharge capacity of the AC side power conversion system to the charge capacity of the AC side power conversion system and the DC side charge and discharge efficiency is used as the AC side power conversion system efficiency; AC side loss rate model: The ratio of the AC side power conversion system loss to the station charging capacity is used as the AC side power conversion system loss rate; Step S3.4: Based on the site losses, DC-side battery cluster losses, and AC-side power conversion system losses, an auxiliary equipment and line-level energy efficiency model is constructed, which includes the following three elements: Auxiliary equipment and line loss model: The difference between the station loss and the DC side battery cluster loss and the AC side power conversion system loss is used as the auxiliary equipment and line loss; Auxiliary equipment and line loss rate model: The ratio of auxiliary equipment and line loss to the station charging volume is used as the auxiliary equipment and line loss rate; Auxiliary equipment and line efficiency model: The ratio of the station efficiency to the DC side charging and discharging efficiency and the AC side power conversion system efficiency is used as the auxiliary equipment and line efficiency.

[0045] Step S4 includes: Step S4.1, identifying the SOC values ​​corresponding to the station, the DC-side battery cluster, and the AC-side power conversion system at the start and end times of the evaluation cycle; Step S4.2: Determine the correction direction based on the identified SOC value: If the SOC value at the end time is greater than the SOC value at the start time, it indicates that the low-voltage industrial and commercial energy storage system is net charged during the evaluation period, and the excess stored energy needs to be deducted from the charge amount; If the SOC value at the end time is less than the SOC value at the start time, it indicates that the low-voltage industrial and commercial energy storage system has a net discharge during the evaluation period, and the excess energy needs to be deducted from the discharge amount; If the SOC value at the end time is equal to the SOC value at the start time, no correction is required.

[0046] In the above example station, the sum of the losses of energy storage cabinets 1 to 4 is taken as the station loss, which is measured and analyzed by a meter.

[0047] Step S3.1: Construct a site energy efficiency model and correct the energy difference caused by the inconsistency of the SOC start and end values. The analysis is as follows.

[0048] Case 1: If the SOC at the start and end of the evaluation cycle is consistent, a direct calculation method can be used. The loss and efficiency are calculated using the difference and ratio of the charge and discharge amounts within the evaluation cycle, respectively. The details are as follows: Station loss model: ; Station loss rate model: ; Station efficiency model: ; Where, They are the total loss, charging and discharging amount of the station respectively; are loss rate and efficiency respectively.

[0049] The operation of the energy storage system may be affected by other factors such as regulation or fault shutdown, resulting in inconsistent battery SOC values ​​at the start and end of the evaluation cycle, which will cause large calculation deviations.

[0050] The SOC of the energy storage station can be calculated using the SOC of the battery according to the calculation formula. Specifically, the station SOC is calculated by multiplying the SOC of all battery clusters by the sum of their rated capacities and dividing it by the total rated capacity of the station.

[0051] ; Where, are the rated capacity and SOC of the station respectively; are the rated capacity and SOC of the i-th battery cluster respectively; N is the total number of battery clusters.

[0052] To ensure accuracy, the energy efficiency calculation model is modified in Cases 2 and 3 by combining the changes in the station SOC at the start and end times to ensure the accuracy and credibility of the model.

[0053] Case 2: If the battery state of charge at the station at the start of the evaluation period <Battery charge status of the station at the end time , indicating that the station has stored too much energy during the evaluation period, and the excess storage needs to be deducted.

[0054] Station loss model: ; Station loss rate model: ; Station efficiency model: .

[0055] Case 3: If the battery state of charge at the station at the start of the evaluation period > End time (i.e. termination time) station battery charge status , indicating that the station released more energy during the evaluation period, and the excess energy needs to be deducted.

[0056] Station loss model: ; Station loss rate model: ; Station efficiency model: .

[0057] Step S3.2: Construct a DC side battery charging and discharging energy efficiency model and correct the energy difference caused by the inconsistent SOC start and end values. The analysis is as follows.

[0058] Compared to the site energy efficiency model, the DC battery charge-discharge energy efficiency model analyzes a single device, namely a battery cluster. However, the two models share the same formulas, except for the operating parameters. Therefore, the subscript "S" in the site energy efficiency model can be replaced with "Battery B" and no further explanation is provided here.

[0059] Step S3.3: Construct an energy efficiency model of the AC side power conversion system, deduct the impact of DC side charging and discharging, and correct the energy difference caused by the inconsistency of the SOC start and end values. The analysis is as follows.

[0060] The metering data of the PCS monitoring point includes the battery charging and discharging and the power conversion system. The DC side battery charging and discharging loss should be deducted when constructing the energy efficiency model.

[0061] Case 1: If the SOC at the start and end of the evaluation period are the same.

[0062] AC side loss model: ; AC side loss rate model: ; AC side efficiency model: ; Where, They are the loss, charge and discharge of the AC side power conversion system respectively; are the loss rate and efficiency of the AC side power conversion system respectively; is the loss of the DC side battery cluster; is the efficiency of the DC side battery cluster.

[0063] The PCS of the energy storage cabinet manages each cluster individually. Therefore, the energy difference caused by inconsistent SOC start and end values ​​on the AC side model can be corrected using battery cluster data.

[0064] Case 2: If the battery state of charge on the DC side at the start of the evaluation cycle < Battery state of charge on the DC side at the end time , indicating that the battery has stored more energy during this evaluation cycle, and the excess storage needs to be deducted.

[0065] AC side loss model: ; AC side loss rate model: ; AC side efficiency model: ; Case 3: If the battery state of charge on the DC side at the start of the evaluation cycle > Battery state of charge on the DC side at the end time , indicating that the battery released more energy during this evaluation cycle, and the excess energy needs to be deducted.

[0066] AC side loss model: ; AC side loss rate model: ; AC side efficiency model: ; Step S3.4: Construct an auxiliary equipment and line energy efficiency model, and analyze it as follows.

[0067] Auxiliary equipment and lines do not have independent metering devices, and require comprehensive analysis based on the station, DC side charging and discharging, and AC side power conversion system models.

[0068] Auxiliary equipment and line loss model: ; Auxiliary equipment and line loss rate: ; Auxiliary equipment and line efficiency model: ; Where, They are the loss amount, loss rate and efficiency of auxiliary equipment and lines respectively.

[0069] Furthermore, step S5 includes: Step S5.1: Based on the revised four-dimensional energy efficiency model, calculate the station efficiency, DC side charging and discharging efficiency, AC side power conversion system efficiency, and auxiliary equipment and line loss rate for each evaluation period, including daily, weekly, monthly, and annual evaluation periods; the calculated station efficiency, DC side charging and discharging efficiency, AC side power conversion system efficiency, and auxiliary equipment and line loss rate serve as energy efficiency indicators for the corresponding dimensional model; Step S5.2: Using the evaluation period as the horizontal axis and each energy efficiency indicator as the vertical axis, draw the station efficiency trend curve, the DC side charging and discharging efficiency trend curve, the AC side power conversion system efficiency trend curve, and the auxiliary equipment and line loss rate trend curve; Step S5.3: By comparing the slope changes of the curves of adjacent cycles, the continuous degradation trend of the energy efficiency index is identified, and the degradation starting cycle is located.

[0070] Based on the revised four-dimensional energy efficiency model from step S4, this model fully accounts for the impact of SOC variations at the start and end of the evaluation cycle for the power plant, DC battery charging and discharging, auxiliary equipment and lines, and AC power conversion system, ensuring data accuracy and reliability. Simultaneously, the rated capacity and operating data for each layer (power plant, DC battery cluster, AC power conversion system, auxiliary equipment and lines) are prepared. This data was acquired in step S2 and used for subsequent calculations.

[0071] Taking one day as the evaluation cycle, the relevant formulas and algorithms in the four-dimensional energy efficiency model are used to calculate the station efficiency, DC-side charge-discharge efficiency, AC-side power conversion system efficiency, and auxiliary equipment and line loss rate. For example, station efficiency is calculated as the ratio of the station's discharge capacity to its charge capacity; DC-side charge-discharge efficiency is calculated based on the ratio of the DC-side battery cluster's discharge capacity to its charge capacity; AC-side power conversion system efficiency is calculated based on the ratio of the AC-side power conversion system's discharge capacity to its charge capacity and the DC-side charge-discharge efficiency; and the auxiliary equipment and line loss rate is calculated as the ratio of auxiliary equipment and line losses to the station's charge capacity. Taking one week as the evaluation cycle, the relevant data within the week is also summarized and calculated based on the four-dimensional energy efficiency model. For example, the total station charge-discharge capacity is the sum of the daily charge-discharge capacity within the week. Using the corresponding efficiency calculation formulas, the station efficiency, DC-side charge-discharge efficiency, AC-side power conversion system efficiency, and auxiliary equipment and line loss rate for that week are calculated. The calculation principles for a one-month and one-year evaluation cycle are the same as for a one-week evaluation cycle and are not further explained here.

[0072] Enter the energy efficiency index data for different evaluation cycles calculated in step S5.1 into the drawing tool. For example, in Excel, enter the energy efficiency index data corresponding to the daily evaluation cycle into the corresponding columns in sequence. Then, use the line graph function to draw the station efficiency trend curve with the evaluation cycle as the horizontal axis and the energy efficiency index as the vertical axis. Similarly, draw the DC side charging and discharging efficiency trend curve, the AC side power conversion system efficiency trend curve, and the auxiliary equipment and line loss rate trend curve. In Python, you can use the plot function of the Matplotlib library to connect the data points into a broken line to generate the corresponding trend curve.

[0073] Annotate the drawn trend curve, including the curve name, axis labels, data point values, etc., to make the curve clearer and easier to understand. At the same time, you can adjust the curve color, line type, etc. as needed to improve the curve visualization effect.

[0074] Compare the slope changes of adjacent cycle curves. If the slope continues to decrease (for the efficiency curve) or continues to increase (for the loss rate curve), it indicates that the energy efficiency index has a continuous degradation trend. For example, in the site efficiency trend curve, if the slope is negative for many consecutive days and the absolute value gradually increases, it means that the site efficiency is continuously declining. By analyzing the turning point of the slope change, the starting cycle of the continuous degradation of the energy efficiency index is determined. For example, in the DC side charge and discharge efficiency trend curve, when the slope changes from positive to negative and then continues to be negative, the evaluation cycle corresponding to the turning point is the degradation starting cycle. This process can be achieved by writing an algorithm or manual observation to ensure that the degradation starting cycle can be accurately identified and located, providing a basis for subsequent decision-making.

[0075] In addition, step S6 includes: Step S6.1: Set independent lower thresholds for the energy efficiency indicators of the site efficiency, DC battery charge and discharge efficiency, and AC power conversion system efficiency; and set independent upper thresholds for the auxiliary equipment and line loss rates. Step S6.2: Perform real-time comparison of each energy efficiency indicator within each evaluation cycle, and when any energy efficiency indicator exceeds the corresponding threshold, locate the specific level of the abnormal source corresponding to the exceeded energy efficiency indicator: If it is a site-level anomaly, the site will be located at the entire low-voltage industrial and commercial energy storage system; If the DC side is abnormal, locate the battery cluster number; If the AC side is abnormal, locate the number of the power conversion system; If the auxiliary equipment is abnormal, locate the temperature control subsystem / monitoring subsystem in the low-voltage industrial and commercial energy storage system.

[0076] Furthermore, step S6 also includes: pushing the positioning results and the calculated over-limit energy efficiency index data to a remote terminal for display and storage, and triggering an audible and visual alarm.

[0077] Set warning thresholds and establish an over-limit warning mechanism. Efficiency parameters (energy efficiency indicators), i.e., station efficiency, AC side PCS efficiency, and DC side charge and discharge efficiency, set lower thresholds. Loss rate parameters, i.e., auxiliary equipment and line loss rate, set upper thresholds. Specifically, set warning thresholds as follows: Station efficiency lower threshold , DC side battery charging and discharging efficiency lower limit threshold , AC side power conversion system efficiency lower limit threshold , auxiliary system and line loss rate upper threshold .

[0078] If an efficiency parameter in the evaluation period is less than or equal to the warning threshold, the system will immediately determine that it is abnormal, issue a warning message, and at the same time indicate the source location of the abnormal parameter to assist users in quick troubleshooting and optimization adjustments; if the loss rate parameter in the evaluation period is greater than or equal to the warning threshold, the system will immediately determine that the energy efficiency of the auxiliary equipment and lines of the industrial and commercial energy storage station is abnormal, issue a warning message, and at the same time indicate the source location of the abnormal parameter.

[0079] In some embodiments, the energy efficiency analysis system 200 for low-voltage industrial and commercial energy storage systems may include multiple functional modules composed of computer program segments. The computer programs of the various program segments in the energy efficiency analysis system 200 for low-voltage industrial and commercial energy storage systems may be stored in a memory of a computer device and executed by at least one processor to perform (see Figure 1 (Description) Energy efficiency analysis function for low-voltage industrial and commercial energy storage systems.

[0080] In this embodiment, the energy efficiency analysis system 200 of the low-voltage industrial and commercial energy storage system can be divided into multiple functional modules according to the functions it performs, such as Figure 3 As shown. The functional modules may include: a loss identification module 210, a data acquisition module 220, an energy efficiency model construction module 230, an energy efficiency model correction module 240, an energy efficiency index calculation module 250, and an energy efficiency early warning module 260. A module as referred to in the present invention refers to a series of computer program segments that can be executed by at least one processor and can perform fixed functions, and is stored in a memory. In this embodiment, the functions of each module will be described in detail in subsequent embodiments.

[0081] The loss acquisition module 210 is used to obtain the comprehensive loss of the site of the low-voltage industrial and commercial energy storage system, including the DC side battery charge and discharge loss, the AC side power conversion system loss, and the auxiliary equipment and line loss; the data acquisition module 220 is used to obtain the rated capacity and operating data of each level of the low-voltage industrial and commercial energy storage system. The operating data includes the total charge and discharge amount of the site, the charge and discharge amount of the AC side power conversion system, the charge and discharge amount of the DC side battery cluster and their corresponding SOC values; the energy efficiency model construction module 230 is used to define the four-dimensional coverage of the site, DC side battery charge and discharge, auxiliary equipment and lines, and AC side power conversion system based on the obtained comprehensive loss of the site, the rated capacity of each level of the low-voltage industrial and commercial energy storage system and the operating data. Energy efficiency model, each dimensional model includes a loss model, a loss rate model and an efficiency model; the energy efficiency model correction module 240 is used to identify the SOC difference corresponding to each dimensional model at the start and end times of the evaluation period, and correct each dimensional model according to the change direction of the SOC difference; the energy efficiency index calculation module 250 is used to calculate the energy efficiency index under the daily, weekly, monthly and annual evaluation periods based on the corrected four-dimensional energy efficiency model, and generate an energy efficiency trend curve; the energy efficiency early warning module 260 is used to set a lower limit threshold for the site efficiency, DC side charging and discharging efficiency, and AC side power conversion system efficiency in the energy efficiency index, and set an upper limit threshold for the auxiliary equipment loss rate in the energy efficiency index. When any parameter exceeds the corresponding threshold, a positioning early warning is triggered.

[0082] Figure 4 This is a structural diagram of a terminal 300 provided in an embodiment of the present invention. The terminal 300 can be used to execute the energy efficiency analysis method of the low-voltage industrial and commercial energy storage system provided in an embodiment of the present invention.

[0083] The terminal 300 may include a processor 310, a memory 320, and a communication module 330. These components communicate via one or more buses. Those skilled in the art will appreciate that the server structure shown in the figure does not limit the present invention. The server structure may be a bus structure or a star structure, and may include more or fewer components than shown, or may combine certain components or arrange the components differently.

[0084] Memory 320 can be used to store execution instructions of processor 310. Memory 320 can be implemented by any type of volatile or non-volatile storage device, or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk, or optical disk. When the execution instructions in memory 320 are executed by processor 310, terminal 300 can perform some or all of the steps in the above-described method embodiments.

[0085] The processor 310 is the control center of the storage terminal. It uses various interfaces and lines to connect various parts of the entire electronic terminal. It executes various functions of the electronic terminal and / or processes data by running or executing software programs and / or modules stored in the memory 320, and calling data stored in the memory. The processor can be composed of an integrated circuit (IC), for example, it can be composed of a single packaged IC, or it can be composed of multiple packaged ICs with the same or different functions. For example, the processor 310 can only include a central processing unit (CPU). In the embodiment of the present invention, the CPU can be a single computing core or multiple computing cores.

[0086] The communication module 330 is used to establish a communication channel so that the storage terminal can communicate with other terminals, receive user data sent by other terminals, or send user data to other terminals.

[0087] The present invention also provides a computer storage medium, wherein the computer storage medium may store a program that, when executed, may include some or all of the steps of each embodiment provided herein. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0088] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software plus a necessary general-purpose hardware platform. Based on this understanding, the technical solutions in the embodiments of the present invention, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, among other media capable of storing program code, and includes instructions for causing a computer terminal (which can be a personal computer, a server, or a second terminal, a network terminal, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention.

[0089] In this specification, the same or similar parts between the various embodiments can be referred to each other. In particular, for the terminal embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description in the method embodiment.

[0090] In the several embodiments provided by the present invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative. For example, the division of the modules is merely a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or modules, and can be electrical, mechanical or other forms.

[0091] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected to achieve the purpose of the present embodiment according to actual needs.

[0092] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0093] Although the present invention has been described in detail with reference to the accompanying drawings and in conjunction with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be easily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A method for analyzing energy efficiency of a low-voltage industrial and commercial energy storage system, characterized in that: include: Step S1: Obtaining the comprehensive site losses of the low-voltage industrial and commercial energy storage system, including DC-side battery charging and discharging losses, AC-side power conversion system losses, and auxiliary equipment and line losses; Step S2: Acquire the rated capacity and operating data of each level of the low-voltage industrial and commercial energy storage system. The operating data includes the total charge and discharge capacity of the station, the charge and discharge capacity of the AC-side power conversion system, the charge and discharge capacity of the DC-side battery cluster, and the corresponding SOC values ​​of each. Step S3: Based on the acquired comprehensive site losses, the rated capacities of each level of the low-voltage industrial and commercial energy storage system, and operational data, a four-dimensional energy efficiency model is defined, covering the site, DC-side battery charging and discharging, auxiliary equipment and lines, and AC-side power conversion system. Each dimensional model includes a loss model, a loss rate model, and an efficiency model. Step S4: Identify the SOC differences corresponding to each dimensional model at the start and end of the evaluation period, and modify each dimensional model according to the change direction of the SOC difference; Step S5: Based on the revised four-dimensional energy efficiency model, calculate the energy efficiency indicators under the daily, weekly, monthly, and annual evaluation cycles, and generate an energy efficiency trend curve; Step S6: Set a lower threshold for the site efficiency, DC side charging and discharging efficiency, and AC side power conversion system efficiency in the energy efficiency index, and set an upper threshold for the auxiliary equipment loss rate in the energy efficiency index. When any parameter exceeds the corresponding threshold, a positioning warning is triggered.

2. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 1, characterized in that: The steps to obtain the comprehensive site loss of a low-voltage commercial and industrial energy storage system include: Step S1.1, the DC side battery charge and discharge loss comes from the electric energy heat loss caused by the internal resistance of the battery cell during the charge and discharge process; Step S1.2: The AC side power conversion system loss is derived from the switching loss generated by the power switching device during operation; Step S1.3: The auxiliary equipment and line losses include the power consumption of the monitoring system, the power consumption of the lighting, the energy consumption of the temperature control system and the resistance loss of the power line.

3. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 1, characterized in that: The specific method for obtaining the operating data in step S2 includes: Step S2.1: Read the accumulated forward active energy and reverse active energy at the connection point between the energy storage station and the grid in the low-voltage industrial and commercial energy storage system, and calculate the difference between the start and end readings of the evaluation period as the total charge and discharge capacity of the station; read the rated capacity corresponding to the station in the low-voltage industrial and commercial energy storage system; Step S2.2, obtaining the cumulative charge and discharge monitoring value of each AC side power conversion system; reading the rated capacity corresponding to each AC side power conversion system; Step S2.3, collecting the cumulative charge and discharge amount of each battery cluster; reading the rated capacity corresponding to each battery cluster; and identifying the real-time SOC value of each battery cluster during the evaluation period; Step S2.4: Calculate the SOC values ​​of the station and the AC-side power conversion system based on the SOC values ​​of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the station and the rated capacity of the AC-side power conversion system.

4. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 3, characterized in that: Step S2.4 includes: The formula for calculating the corresponding SOC value of the station based on the SOC value of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the station is: ； in, is the SOC value corresponding to the station; N is the total number of battery clusters; is the SOC value of the i-th battery cluster; is the rated capacity of the i-th battery cluster; is the rated capacity of the station; The formula for calculating the corresponding SOC value of the AC side power conversion system based on the SOC value of each battery cluster and its corresponding rated capacity, as well as the rated capacity of the AC side power conversion system, is: ； in, is the SOC value corresponding to the AC side power conversion system; is the rated capacity of the AC side power conversion system.

5. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 4, characterized in that: Step S3 includes: Step S3.1: Based on the total charge and discharge capacity of the station, construct a station-level energy efficiency model that includes the following three elements: Station loss model: The difference between the station charging amount and the total discharge amount is taken as the station loss; Station efficiency model: The ratio of the station's discharge capacity to the charge capacity is taken as the station efficiency; Station loss rate model: The ratio of station loss to station charging volume is taken as the station loss rate; Step S3.2: Based on the charge and discharge capacity of the DC-side battery cluster, construct a DC-side battery charge and discharge dimension energy efficiency model that includes the following three elements: DC side loss model: The difference between the charge and discharge capacity of the DC side battery cluster is used as the DC side battery cluster loss; DC side efficiency model: The ratio of the discharge capacity to the charge capacity of the DC side battery cluster is used as the DC side charge and discharge efficiency; DC side loss rate model: The ratio of the DC side battery cluster loss to the DC side battery cluster charge is used as the DC side battery cluster loss rate; Step S3.3: Based on the charge and discharge capacity of the AC power conversion system, construct an AC power conversion system dimensional energy efficiency model including the following three elements: AC side loss model: The difference between the AC side power conversion system charge, the AC side power conversion system discharge, and the DC side battery cluster loss is taken as the AC side power conversion system loss. AC side efficiency model: The ratio of the discharge capacity of the AC side power conversion system to the charge capacity of the AC side power conversion system and the DC side charge and discharge efficiency is used as the AC side power conversion system efficiency; AC side loss rate model: The ratio of the AC side power conversion system loss to the station charging capacity is used as the AC side power conversion system loss rate; Step S3.4: Based on the site losses, DC-side battery cluster losses, and AC-side power conversion system losses, an auxiliary equipment and line-level energy efficiency model is constructed, which includes the following three elements: Auxiliary equipment and line loss model: The difference between the station loss and the DC side battery cluster loss and the AC side power conversion system loss is used as the auxiliary equipment and line loss; Auxiliary equipment and line loss rate model: The ratio of auxiliary equipment and line loss to the station charging volume is used as the auxiliary equipment and line loss rate; Auxiliary equipment and line efficiency model: The ratio of the station efficiency to the DC side charging and discharging efficiency and the AC side power conversion system efficiency is used as the auxiliary equipment and line efficiency.

6. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 5, characterized in that: Step S4 includes: Step S4.1, identifying the SOC values ​​corresponding to the station, the DC-side battery cluster, and the AC-side power conversion system at the start and end times of the evaluation cycle; Step S4.2: Determine the correction direction based on the identified SOC value: If the SOC value at the end time is greater than the SOC value at the start time, it indicates that the low-voltage industrial and commercial energy storage system is net charged during the evaluation period, and the excess stored energy needs to be deducted from the charge amount; If the SOC value at the end time is less than the SOC value at the start time, it indicates that the low-voltage industrial and commercial energy storage system has a net discharge during the evaluation period, and the excess energy needs to be deducted from the discharge amount; If the SOC value at the end time is equal to the SOC value at the start time, no correction is required.

7. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 1, characterized in that: Step S5 includes: Step S5.1: Based on the revised four-dimensional energy efficiency model, calculate the station efficiency, DC side charging and discharging efficiency, AC side power conversion system efficiency, and auxiliary equipment and line loss rate for each evaluation period, including daily, weekly, monthly, and annual evaluation periods; the calculated station efficiency, DC side charging and discharging efficiency, AC side power conversion system efficiency, and auxiliary equipment and line loss rate serve as energy efficiency indicators for the corresponding dimensional model; Step S5.2: Using the evaluation period as the horizontal axis and each energy efficiency indicator as the vertical axis, draw the station efficiency trend curve, the DC side charging and discharging efficiency trend curve, the AC side power conversion system efficiency trend curve, and the auxiliary equipment and line loss rate trend curve; Step S5.3: By comparing the slope changes of the curves of adjacent cycles, the continuous degradation trend of the energy efficiency index is identified, and the degradation starting cycle is located.

8. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 7, characterized in that: Step S6 includes: Step S6.1: Set independent lower thresholds for the energy efficiency indicators of the site efficiency, DC battery charge and discharge efficiency, and AC power conversion system efficiency; and set independent upper thresholds for the auxiliary equipment and line loss rates. Step S6.2: Perform real-time comparison of each energy efficiency indicator within each evaluation cycle, and when any energy efficiency indicator exceeds the corresponding threshold, locate the specific level of the abnormal source corresponding to the exceeded energy efficiency indicator: If it is a site-level anomaly, the site will be located at the entire low-voltage industrial and commercial energy storage system; If the DC side is abnormal, locate the battery cluster number; If the AC side is abnormal, locate the number of the power conversion system; If the auxiliary equipment is abnormal, locate the temperature control subsystem / monitoring subsystem in the low-voltage industrial and commercial energy storage system.

9. The energy efficiency analysis method of a low-voltage industrial and commercial energy storage system according to claim 8, characterized in that: Step S6 also includes: pushing the positioning results and the calculated over-limit energy efficiency index data to a remote terminal for display and storage, and triggering an audible and visual alarm.

10. An energy efficiency analysis system for a low-voltage industrial and commercial energy storage system, characterized in that: include: The loss acquisition module is used to obtain the comprehensive site losses of low-voltage industrial and commercial energy storage systems, including DC-side battery charging and discharging losses, AC-side power conversion system losses, and auxiliary equipment and line losses. The data acquisition module is used to obtain the rated capacity and operating data of each level of the low-voltage industrial and commercial energy storage system. The operating data includes the total charge and discharge capacity of the station, the charge and discharge capacity of the AC side power conversion system, the charge and discharge capacity of the DC side battery cluster, and the corresponding SOC value of each; The energy efficiency model construction module is used to define a four-dimensional energy efficiency model covering the station, DC-side battery charging and discharging, auxiliary equipment and lines, and AC-side power conversion system based on the acquired comprehensive station losses, rated capacity of each layer of the low-voltage industrial and commercial energy storage system, and operating data. Each dimensional model includes a loss model, a loss rate model, and an efficiency model. The energy efficiency model correction module is used to identify the SOC differences corresponding to each dimensional model at the start and end of the evaluation period, and to correct each dimensional model according to the direction of change of the SOC difference; Energy efficiency index calculation module, which is used to calculate energy efficiency indicators under daily, weekly, monthly and annual evaluation cycles based on the revised four-dimensional energy efficiency model, and generate energy efficiency trend curves; The energy efficiency warning module is used to set lower thresholds for the site efficiency, DC side charging and discharging efficiency, and AC side power conversion system efficiency in the energy efficiency indicators, and set upper thresholds for the auxiliary equipment loss rate in the energy efficiency indicators. When any parameter exceeds the corresponding threshold, a positioning warning is triggered.

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