Off-grid energy storage twin trawling test platform and method

Abstract

The invention provides an off-grid energy storage twin trawling test platform and method, and the platform comprises a dynamic off-grid switching module which is used for automatically triggering and quitting a peak clipping and valley filling strategy, closing a converter PCS, and switching to an off-grid mode when the access of a test load is detected; the VF / PQ cooperative control module is linked with the dynamic off-grid switching module, dynamically distributes the proportion of a constant voltage source VF and a power tracking source PQ according to the performance of the converter, and adjusts the output power of the PQ source through a power automatic tracking algorithm; the intelligent SOC adjustment module acquires electric quantity data of a tested system in real time, calculates a target SOC value and synchronizes the target SOC value to the VF / PQ cooperative control module; the multi-level protection module is used for monitoring grid-connected point power, transformer load and PCS states in real time and triggering countercurrent prevention, super capacitance prevention and error fault-tolerant protection; and after completing mode switching, the dynamic off-network switching module sends a starting signal to the VF / PQ cooperative control module.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage system testing and power electronics control, and particularly relates to an off-grid energy storage back-to-back test platform and method, which are used to achieve efficient and safe testing of the energy storage system by dynamically switching the converter mode, coordinately controlling power distribution, intelligently adjusting the battery SOC, and multi-level protection mechanisms in an off-grid environment. Background Art

[0002] The current back-to-back test method for energy storage systems mainly relies on the actual power grid environment, and the energy storage devices need to be directly connected to the power grid during the test. However, such methods have significant limitations: Power grid security risks: The fluctuations or abnormal operating conditions of the test load may be directly fed back to the power grid, resulting in problems such as voltage fluctuations and frequency deviations, threatening the stability of the power grid. Especially when testing high-power or highly fluctuating loads, such risks are more prominent.

[0003] Limited test scenarios: It is difficult to simulate extreme operating conditions (such as island operation, high proportion of load mutations, etc.) under the power grid connection state, resulting in insufficient test coverage and inability to fully verify the performance of the energy storage system in real complex scenarios.

[0004] High operation complexity: Traditional off-grid tests require manual switching of device modes, parameter adjustment, and monitoring of the operating status. The operation steps are cumbersome and rely on manual experience, and it is easy to cause test interruption or equipment damage due to misoperation.

[0005] Low automation level: Existing test platforms lack a unified control strategy. For example, key links such as dynamic regulation of charge and discharge power and closed-loop control of the state of charge (SOC) of the battery still require manual intervention, and it is difficult to guarantee test efficiency and consistency.

[0006] Although some off-grid test schemes have tried to solve the above problems, they still have the following deficiencies: Low mode switching efficiency: The switching between off-grid and grid-connected modes takes a long time, and system oscillations are easily caused due to out-of-sync device states during the switching process; Unfriendly human-computer interaction: Functions such as test parameter setting, status monitoring, and fault handling are scattered, lacking an integrated interface, and the operation experience is poor; Incomplete protection mechanism: The response strategies for abnormal operating conditions such as reverse current at the grid connection point and transformer overcapacity are single, and the fault tolerance ability is limited, making it difficult to meet complex test requirements.

[0007] Therefore, there is an urgent need for an energy storage test platform that can be compatible with the normal operation of the power grid (such as peak shaving and valley filling), can quickly switch to the off-grid test mode, and has intelligent control and protection capabilities to improve the test safety, comprehensiveness, and automation level. Summary of the Invention

[0008] In view of the defects and shortcomings of the prior art, the present invention provides an off-grid energy storage towing test platform and method, which solves the problems of high dependence on the power grid, limited scene coverage and complex operation of traditional test methods through the following innovative designs: Dynamic off-grid switching and coordinated control: Automatically trigger off-grid mode switching based on the test load access signal, build a stable voltage reference by starting the constant voltage source (VF) in sequence from master to slave, and link the power tracking source (PQ) to achieve dynamic VF / PQ ratio allocation in an off-grid environment, supporting seamless conversion between on-grid and off-grid modes; Intelligent power tracking and SOC closed-loop adjustment: The automatic power tracking algorithm is used to dynamically calculate the PQ source output power according to the number of VF sources, and gradually approach the full load demand of the system under test through cyclic iteration; the target SOC value calculation and charge and discharge template control are integrated synchronously to reserve safety margin and realize dynamic closed-loop adjustment of SOC; Multi-level protection and full-process automation: Integrate anti-reverse flow, anti-overcapacity and error tolerance mechanisms, monitor the grid power, transformer load and converter status in real time, dynamically respond to abnormal conditions through threshold judgment and gradient adjustment, and realize closed-loop control of the entire test process in combination with inter-module signal feedback; Generalization of test scenarios and improvement of efficiency: It is compatible with both conventional peak shaving and valley filling operation and off-grid testing scenarios. It replaces manual intervention with intelligent strategies, significantly reduces the risk of grid shocks, and improves the ability to simulate extreme working conditions and test efficiency.

[0009] The present invention takes modular collaboration, algorithm-driven and closed-loop protection as its core, and realizes efficient, safe and fully automated towing testing of energy storage systems in off-grid environments, providing a reliable technical support for industrial and commercial energy storage scenarios.

[0010] The technical solution specifically adopted by the present invention to solve the technical problem is: An off-grid energy storage towing test platform, comprising: Dynamic off-grid switching module, used to automatically trigger the exit of peak shaving and valley filling strategy, shut down the converter PCS and switch to off-grid mode when the test load is detected; A VF / PQ collaborative control module, which is linked with the dynamic off-grid switching module, dynamically allocates the ratio of the constant voltage source VF to the power tracking source PQ according to the converter performance, and adjusts the output power of the PQ source through an automatic power tracking algorithm; An intelligent SOC adjustment module obtains the power data of the system under test in real time, calculates the target SOC value and synchronizes it to the VF / PQ collaborative control module; Multi-level protection module monitors the grid connection point power, transformer load and PCS status in real time, triggering anti-reverse flow, anti-overcapacity and error tolerance protection; After the dynamic off-grid switching module completes the mode switching, it sends a start signal to the VF / PQ collaborative control module; The VF / PQ collaborative control module receives the target SOC value from the intelligent SOC adjustment module and dynamically adjusts the charge and discharge strategy; The warning signal of the multi-level protection module is real-time fed back to other modules to terminate or adjust the operating state.

[0011] Furthermore, the dynamic off-grid switching module, VF / PQ collaborative control module, intelligent SOC adjustment module, and multi-level protection module interact data through a real-time communication interface, including the operating state, target SOC value, and power distribution instruction; After the dynamic off-grid switching module completes the mode switching, it sends an initialization signal to the VF / PQ collaborative control module to trigger the power distribution and tracking operation; When the multi-level protection module detects a fault, it sends an interrupt signal to the dynamic off-grid switching module to force the restoration of the grid-connected mode; When the intelligent SOC adjustment module detects overcharge or over-discharge, it sends a power correction instruction to the VF / PQ collaborative control module.

[0012] Furthermore, when the dynamic off-grid switching module switches from grid-connected to off-grid, it starts the VF source PCS in the order of main first and then slave, constructs a stable voltage frequency, and then starts the PQ source PCS; when switching from off-grid to grid-connected, it shuts down the PCS in the order of slave first and then master, closes the grid connection switch, and then switches to the PQ mode and resumes the peak shaving and valley filling strategy.

[0013] Furthermore, the VF / PQ collaborative control module dynamically allocates the ratio of the constant voltage source VF and the power tracking source PQ according to the performance of the converter, and adjusts the output power of the PQ source through a power automatic tracking algorithm, where: The power of the PQ source is the result of dividing the total power by the number of VF sources plus 1; The power adjustment range of the measured system is gradually expanded through cyclic iteration.

[0014] Furthermore, the intelligent SOC adjustment module calculates the target SOC value according to the difference between the current power of the measured system and the rated capacity of the energy storage system, specifically: the target SOC value is the percentage of the difference in the rated capacity, and a 5% reserved margin is deducted.

[0015] Furthermore, the multi-level protection module includes: An anti-backflow protection unit for monitoring the grid-connected point power during discharge. If the power is less than or equal to the set threshold, the discharge is terminated and retried after a delay; An anti-overcapacity protection unit for monitoring the transformer load during charging. If it exceeds the safe capacity threshold, the charging power is reduced in a gradient; The error-tolerant protection unit is used to monitor the PQ source power error. If it exceeds the limit, the retry mechanism is triggered. After failure, the abnormal PCS is isolated and the power is reallocated.

[0016] And, an off-grid energy storage towing test method, comprising the following steps: Off-grid mode triggering and switching: Real-time monitoring of the test load access signal in the peak shaving and valley filling mode to trigger the off-grid mode switch; Exit the peak-shaving and valley-filling strategy and shut down the PCS, and switch some PCS to the constant voltage source (VF) mode; Disconnect the grid-connected switch, start the VF source to build a stable voltage and frequency, and start the power tracking source (PQ) and the system under test in a linked manner.

[0017] VF / PQ dynamic coordination and power tracking: Dynamically allocate the ratio of VF source to PQ source according to converter performance; The PQ source output power is adjusted through the power automatic tracking algorithm, gradually expanding the power adjustment range of the system under test; Approach the full load demand of the system under test in a loop iteration manner.

[0018] Intelligent SOC adjustment and charge and discharge control: Based on the current power of the system under test and the rated capacity of the energy storage system, the target SOC value is calculated and a safety margin is reserved; Select the charge and discharge template according to the target SOC value, and automatically perform constant current charging, constant voltage charging or constant power discharging operations; Real-time monitoring and dynamic adjustment of SOC to the target value during charging and discharging.

[0019] Multi-level protection and feedback control: Real-time monitoring of grid connection point power, transformer load and PCS status; Trigger anti-backflow, anti-overcapacity and error tolerance protection according to the preset protection strategy; The protection signal is fed back to the charge and discharge control and power tracking process to dynamically terminate or adjust the operating status.

[0020] Furthermore, in the automatic power tracking algorithm, the PQ source power is the result of dividing the total power by the number of VF sources plus 1.

[0021] Furthermore, the target SOC value is the percentage of the difference to the rated capacity, minus a 5% reserve margin.

[0022] Furthermore, the anti-reverse flow protection is triggered when the grid connection point power is ≤ a set threshold, and the anti-overcapacity protection is triggered when the transformer load exceeds a safe capacity threshold.

[0023] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects: Significantly reduce the risk of power grid impact: Through the dynamic off-grid switching mechanism, the tested system is automatically isolated from the power grid when the test load is connected, avoiding the impact of abnormal conditions such as voltage fluctuations and reverse current during the test on the power grid stability; Improve the coverage and accuracy of the test scenario: Based on the VF / PQ collaborative control strategy, dynamically allocate the proportion of power sources, and combined with the progressive power tracking algorithm, it can flexibly simulate extreme load conditions and accurately approximate the full-load demand of the tested system; Ensure the safety and integrity of the test process: Through the closed-loop adjustment of the target SOC and the design of safety margins, avoid the risks of overcharging and over-discharging, and ensure the full charge and full discharge test conditions of the tested energy storage system; Enhance the robustness and reliability of the system: Integrate multi-level protection mechanisms, real-time monitor the power at the grid connection point, the transformer load and the converter status, and quickly respond to abnormal conditions through dynamic adjustment and fault tolerance strategies, reducing the need for manual intervention; Simplify the complexity of test operations: Replace the traditional manual switching mode, parameter adjustment and status monitoring process with an automated strategy, realize one-key switching between grid-connected and off-grid modes, and improve test efficiency and consistency.

[0024] Through the comprehensive design of modular collaboration, algorithm drive and closed-loop protection, the present invention solves the pain points of strong dependence on the power grid, poor scenario adaptability and cumbersome operation of traditional test platforms, and provides reliable technical support for the efficient verification of energy storage systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described in detail below with reference to the drawings and specific embodiments: Figure 1 It is a flowchart of the peak shaving and valley filling mode in an embodiment of the present invention; Figure 2 It is a flowchart of the grid-connected and off-grid switching operation in an embodiment of the present invention; Figure 3 It is an example diagram of the SOC preparation operation adjustment before the back-to-back test in an embodiment of the present invention; Figure 4 It is a flowchart of the SOC preparation operation adjustment before the back-to-back test in an embodiment of the present invention; Figure 5 It is a flowchart of the automatic power following mode in the off-grid mode in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the features and advantages of the present invention more obvious and understandable, specific embodiments are given below and described in detail as follows: It should be noted that the following detailed description is illustrative and aims to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application pertains.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] The purpose of the embodiment of the present invention is to provide an off-grid energy storage test counter-dragging platform. In the normal peak shaving and valley filling operation environment of the energy storage, to avoid the impact on the power grid caused by connecting unstable test loads, the platform can automatically switch to the off-grid environment, and the energy storage system can automatically follow the load size connected to the test platform and adjust the output power in real time to meet the charge and discharge test requirements of the connected load.

[0029] The purpose of the embodiment of the present invention can be achieved in this way: design an off-grid energy storage test counter-dragging platform, including daily peak shaving and valley filling, intelligent grid connection and disconnection switching, SOC adjustment before counter-dragging test, and automatic power following strategy in off-grid mode: Daily peak shaving and valley filling This platform not only meets the peak shaving and valley filling operation scenarios of a normal energy storage system but also has an intelligent protection strategy. Set the peak shaving and valley filling plan period and charge and discharge power in advance according to the local peak and valley periods. The set value of the charge and discharge power needs to consider the transformer capacity and the total power data of the unit. Real-time obtain the operating status of the PCS and BMS, the maximum charge and discharge power, and the alarm and fault status, and adjust the final power target value in real time, and distribute the power according to the status of each unit. Consider the demand during the charging period, and the demand fixed value needs to be set, which is set according to the actual data of the transformer. During charging, the real-time load of the grid connection point or the transformer is detected, and if it exceeds the demand set value, the charging power is reduced; consider anti-counterflow during the discharging period. During discharging, the power value of the grid connection point is detected in real time. When the power of the grid connection point ≤ the set value, the discharging power is reduced. At the same time, the platform has intelligent protection strategies such as anti-counterflow, anti-overcapacity, demand control, SOC upper and lower limit restrictions, fault alarm monitoring, and unit condition monitoring in the daily peak shaving and valley filling operation mode.

[0030] Intelligent grid connection and disconnection switching After determining the load of the system under test to be connected, the energy storage system automatically performs the following operations: exit the current peak shaving and valley filling strategy, and shut down all PCSs; after determining that the shutdown is complete, switch the operating mode of the PCS to be used as the VF source to the off-grid mode; disconnect the bus tie switch and start the PCSs in the order of main first and then slave. After the back-to-back test is completed, it is necessary to restore to the normal peak shaving and valley filling mode and perform the following operations: shut down the PCSs in the order of slave first and then main, switch the operating mode of the PCSs to the grid-connected mode; after the switching is completed, close the bus tie switch, turn on all PCSs, and put them into the peak shaving and valley filling operation mode, and thus restore to the normal grid-connected state. In addition, when the platform performs off-grid switching, it has a simple human-computer interaction and can perform mode switching in the form of buttons on the main monitoring interface.

[0031] SOC adjustment before back-to-back test The platform will collect the existing real-time power of the system under test and calculate the target SOC of the energy storage power station according to the current power of the energy storage under test. When the current SOC is higher than the target, it will discharge, and when it is lower than the target, it will perform a charging operation, and thus perform corresponding charge and discharge coordination operations to ensure that the full charge and full discharge test conditions are met. To simplify the operation process, the peak shaving and valley filling mode is adopted. In the peak shaving and valley filling mode, multiple charge and discharge templates can be set, and the charge and discharge SOC targets and charge and discharge powers of the off-grid preparation template can be set. After the energy storage system reaches the target SOC, it will stop the charge and discharge operations. The calculation method of the target SOC value is: SOC = (Wn - Wc) / Wn * 100%, where Wn is the rated capacity of the energy storage system and Wc is the current power of the system under test; it should be noted that the rated capacity of the system under test cannot be greater than the rated capacity of the energy storage system, otherwise the full charge and full discharge experiment cannot be carried out.

[0032] Power automatic following strategy in off-grid mode The platform realizes an automatic tracking strategy for connecting to the load of the system under test according to a specific algorithm, and can perform the test of the system under test without manual intervention. There are two automatic operation methods in total: One is that the number of PCSs is small and their own performance meets the off-grid parallel operation of all units. Under this condition, only need to switch all PCSs to the off-grid mode and automatically support the load of the system under test as the VF source.

[0033] The other is that the number of PCSs is large, or their own performance cannot meet the off-grid parallel operation of all units. Under this condition, the platform will arrange the ratio of the VF source to the PQ source according to the performance of the energy storage system converter. When the converter performance cannot meet the requirement that all converters are in the VF source, the system will appropriately arrange some converters to participate in the automatic tracking regulation in the PQ mode. The energy storage system will divide the PCSs into parts as the VF source for basic support to the greatest extent, and the remaining PCSs will be used as the PQ source for power tracking output.

[0034] After completing the off-grid preparation and connecting to the load under test, it is necessary to calculate the total power P_all, which is calculated as the sum of the output power of the VF source PCS and the output power of the PQ source PCS. It is necessary to calculate the power P_pq that the PQ source PCS needs to bear, and the calculation method is: P_pq = P_all / 5. If the current output power of the PQ source pcs is P1, then the adjustable power range for the load of the system under test each time is: P1~(Pn * num_vf), where Pn is the rated power of the PCS and num_vf is the number of VF source PCSs. Through the way of cyclic approximation, the load of the system under test is gradually and infinitely close to the full-load state. The present invention adopts the method of using the PQ source PCS alone as the flexible adjustment source, and gradually meets the full-load demand of the system under test in a step-by-step manner.

[0035] In summary, the off-grid energy storage back-to-back test platform of the present invention has four main strategies and performs four different automatic control and adjustment functions. The following further demonstrates and introduces the solution of the present invention through a specific example: In this embodiment, it is set that the energy storage system is connected under a transformer with a capacity of 800 kVA, and there are a total of 4 PCSs with a rated power of 462 kW; due to performance constraints, at most only 4 PCSs are supported to operate in parallel in the VF mode.

[0036] 1. Peak shaving and valley filling strategy As Figure 1 shown, according to the peak and valley periods, the charge and discharge time periods and corresponding powers are set in advance; when the actual time reaches the set time, the charge and discharge control of the unit is carried out according to the set power, and at the same time, it is judged whether the unit is in a controllable state and whether the battery pack soc has reached the locking condition; if the working condition is good, it is judged whether the maximum charge and discharge power sent by the unit exceeds the rated value of the unit, and the smaller value is taken as the maximum charge and discharge limit condition of the unit to control the unit to charge and discharge.

[0037] During charging, start the anti-overcapacity protection strategy to ensure that the real-time load does not exceed the rated capacity of the transformer of 800 kVA; during discharging, start the anti-counterflow protection strategy, measure the power at the grid connection point, and control the output power of the energy storage system to prevent counterflow.

[0038] In the preferred implementation manner of this embodiment, it further includes: Condition judgment mechanism Plan day / month judgment: Before the peak shaving and valley filling strategy is started, the system needs to judge whether it is in the preset "planned day" or "planned month" according to the configuration file. The planned day supports single-day or multi-day combinations (such as the 1st to 5th of each month), and the planned month can set specific months (such as the peak electricity consumption period in winter). If neither is satisfied, the charge and discharge operation is skipped.

[0039] Policy Plan Time Period Matching: When the planned day / month is entered, further match whether the current time is within the time period of the policy plan (e.g., 9:00 - 11:00 every day is the charging period, and 18:00 - 20:00 is the discharging period). The policy is only executed when the match is successful.

[0040] 2. Grid Connection and Disconnection Switching As Figure 2 shown, before switching from grid-connected to off-grid operation mode, first shut down all PCSs, and ensure the reliability of the secondary communication power supply of EMS, PCS, and BMS to ensure that the entire system operates normally after disconnecting the grid connection switch. After remotely disconnecting the grid connection switch, first start 4 PCSs in VF mode, build a stable voltage and frequency, and then start the PQ unit and the measured energy storage unit system.

[0041] For the off-grid to grid-connected mode, first gradually withdraw the measured energy storage system, and then withdraw the Yingpai Energy Storage Power Station. After all are shut down, close the grid connection switch, restore 5 PCSs to PQ operation mode, and put into the peak shaving and valley filling mode to enter the grid-connected operation state.

[0042] All the above steps are realized through automated means to avoid process errors caused by human operation intervention.

[0043] In the preferred implementation manner of this embodiment, it further includes: Emergency Manual Network Disconnection: In the grid-connected to off-grid process, if the automated switch fails (such as communication interruption), it supports the operator to manually disconnect the bus-tie switch through a physical button, and the system automatically recognizes the switching signal and starts the off-grid mode.

[0044] UPS Power Supply Redundancy: Before going off-grid, it is necessary to verify the dual-path power supply redundancy of the UPS to ensure sufficient main and standby power supply switching time and avoid policy failure caused by secondary communication interruption.

[0045] 3. SOC Adjustment before Back-to-Back Test As Figure 3 、 Figure 4 shown, calculate the target SOC of the energy storage power station based on the current power of the measured energy storage (see below). If the SOC of any one of the 5 energy storage units is higher than the target SOC, perform a discharging operation and stop discharging when the target SOC is reached. If the SOC of any one of the 5 cabinets is lower than the target SOC, perform a charging operation and stop the charging operation when the target SOC is reached.

[0046] To simplify the operation process, the peak shaving and valley filling mode is used. In this mode, multiple charge and discharge templates can be set, and the charge and discharge SOC targets and charge and discharge powers of the off-grid preparation template can be set. The energy storage system will stop the charge and discharge operations after reaching the target SOC. The locking and control logics of charge and discharge refer to peak shaving and valley filling.

[0047] Calculation of the target SOC: SOC = (4.6 - Wc) / 4.6 * 100% - 5%; Wc is the current power of the system under test, and subtracting 5% is to reserve a certain dead zone margin.

[0048] 4. Off-grid parallel test automatic power tracking The system monitors the off-grid signal. If it detects that the bus tie switch is disconnected, it will enter the off-grid operation mode; in the off-grid mode, the peak shaving and valley filling strategy will be exited, 4 pcs will be set to the vf mode and operate in parallel; the automatic power tracking strategy will be run, and the number of cycles can be extended according to the actual situation. At the same time, the unit under test needs to set the charge and discharge power according to the actual power of the current energy storage system. The initial maximum charge and discharge power shall not be greater than 462 * 4 = 1.85 MW, and the subsequent power shall be set according to the power of the PQ unit.

[0049] Under the automatic tracking strategy mode, the test of the system under test can be carried out without manual intervention, but it is impossible to adjust the power to the rated power (2.2 MW) for charging and discharging at one time. After exceeding 1.85 MW, it needs to be adjusted slowly and can only approach the rated power infinitely slowly. The following is the calculation method of the power adjustment range each time.

[0050] Taking the actual charging of the test system as an example, assume that the current power of the PQ mode unit is P1: A. Each pcs is rated at 462 kW. 4 pcs are used as vf sources and one pcs is used as a pq source. The chargeable power range of the system under test is: P1 to (1850 + P1) kW; B. The initial load of the system under test cannot exceed the rated value of 4 vf machines, that is: 1.85 MW. The initial power range of the unit under test is: 0 - 1850 kW.

[0051] C. Assume that the initial load is 1.85 MW. 4 vf machines can meet the initial working conditions. Then, the average value is obtained through the automatic tracking strategy, and a power of 1.85 / 5 = 0.37 MW is sent to the pcs of the pq source; D. At this time, the power of all five pcs is balanced to 370 kW. At this time, the pcs of the pq source still has an adjustment capacity of 92 kW. That is, the next power range that the unit under test can set becomes: 370 kW - (370 + 1850 = 2220) kW.

[0052] E. Similarly, when the load of the system under test is 2.2 MW, the power of the pq source is automatically adjusted to 2.2 / 5 = 0.44 MW, that is, 440 kW. At this time, the pcs of the PQ source has a remaining adjustment capacity of 22 kW; at this time, the power range that the unit under test can set becomes: 440 kW - 2222 kW.

[0053] F. The calculation method of the discharge of the unit under test is the same.

[0054] G. Iterate in a loop successively to gradually meet the requirements of the full - scale charge - discharge test.

[0055] In a preferred implementation manner of this embodiment, it further includes: SOC safety boundary control Discharge boundary: When the SOC of the PQ source < 5%, further discharge is prohibited, and it is forced to switch to other PQ sources or terminate the test.

[0056] Charge boundary: When the SOC of the PQ source > 95%, charging is prohibited, and the SOC balancing strategy is triggered (transferring the excess power to the unit with a lower SOC).

[0057] Error tolerance and loop mechanism Error retry strategy: If the PCS telemetered power error > 2kW, the system automatically retries 3 times, with an interval of 2 seconds each time; if it still exceeds the limit, fault isolation is triggered (disabling the abnormal PCS) and the power is re - allocated.

[0058] Loop period optimization: By default, it loops once every 1 second. If the system load fluctuates greatly (such as a change rate > 10% / s), the period is automatically shortened to 0.5 seconds to improve the adjustment response speed.

[0059] As can be seen from the above embodiments, the present invention mainly adopts the grid - connected peak - shaving and valley - filling mode and the off - grid counter - dragging test mode to meet the daily peak - valley arbitrage profit requirements and off - grid test experiment requirements. The present invention conducts the counter - dragging test in the off - grid mode, avoiding the impact of the unstable system under test on the power grid, making the risk controllable. The present invention uses automatic grid - connection and disconnection switching to achieve a friendly switch between the two operating modes, avoiding the uncontrollable risks caused by manual intervention operations. In the off - grid counter - dragging test of the present invention, an automatic power tracking strategy is adopted; with the assistance of a specific algorithm, it approximates the test rated power step by step, realizing full - process automation, reducing manual intervention, and ensuring the intelligence and reliability of the overall counter - dragging test experiment.

[0060] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not represent any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects. The terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "up", "down", "left", "right" are only used to represent relative position relationships, and when the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0061] As described above, it is only the preferred embodiment of the present invention, and it is not a limitation to the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

[0062] The present invention is not limited to the above best implementation manner. Anyone can obtain various other forms of an off-grid energy storage counter-dragging test platform and method under the inspiration of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. An off-grid energy storage tow test platform, characterized in that, Including: A dynamic off-grid switching module, which is used to automatically trigger the exit of the peak shaving and valley filling strategy, turn off the converter PCS and switch to the off-grid mode when detecting the access of the test load; A VF / PQ collaborative control module, which is linked with the dynamic off-grid switching module, dynamically allocates the ratio of the constant voltage source VF and the power tracking source PQ according to the performance of the converter, and adjusts the output power of the PQ source through a power automatic tracking algorithm; An intelligent SOC adjustment module, which obtains the power data of the measured system in real time, calculates the target SOC value and synchronizes it to the VF / PQ collaborative control module; A multi-level protection module, which monitors the grid connection point power, transformer load and PCS status in real time, and triggers anti-counterflow, anti-overcapacity and error tolerance protection; After the dynamic off-grid switching module completes the mode switching, it sends a start signal to the VF / PQ collaborative control module; The VF / PQ collaborative control module receives the target SOC value of the intelligent SOC adjustment module and dynamically adjusts the charge and discharge strategy; The alarm signal of the multi-level protection module is fed back to other modules in real time to terminate or adjust the operating state.

2. The off-grid energy storage back-to-back test platform according to claim 1, characterized in that: The dynamic off-grid switching module, VF / PQ collaborative control module, intelligent SOC adjustment module and multi-level protection module interact data through a real-time communication interface, including operating status, target SOC value and power distribution instructions; After the dynamic off-grid switching module completes the mode switching, it sends an initialization signal to the VF / PQ collaborative control module to trigger power distribution and tracking operations; When the multi-level protection module detects a fault, it sends an interrupt signal to the dynamic off-grid switching module to force the restoration of the grid-connected mode; When the intelligent SOC adjustment module detects overcharge or over-discharge, it sends a power correction instruction to the VF / PQ collaborative control module.

3. The off-grid energy storage tow test platform according to claim 1, characterized in that: When the dynamic off-grid switching module switches from grid-connected to off-grid, it starts the VF source PCS in the order of main first and then slave, constructs a stable voltage frequency and then starts the PQ source PCS; when switching from off-grid to grid-connected, it shuts down the PCS in the order of slave first and then master, closes the grid connection switch and then switches to the PQ mode and resumes the peak shaving and valley filling strategy.

4. The off-grid energy storage back-to-back test platform according to claim 1, characterized in that: The VF / PQ collaborative control module dynamically allocates the ratio of the constant voltage source VF and the power tracking source PQ according to the performance of the converter, and adjusts the output power of the PQ source through a power automatic tracking algorithm, where: The power of the PQ source is the result of dividing the total power by the number of VF sources plus 1; The power adjustment range of the measured system is gradually expanded through cyclic iteration.

5. The off-grid energy storage drag test platform according to claim 1, characterized in that: The intelligent SOC adjustment module calculates the target SOC value according to the difference between the current power of the measured system and the rated capacity of the energy storage system, specifically: the target SOC value is the percentage of the difference in the rated capacity, and a 5% reserved margin is deducted.

6. The off-grid energy storage back-to-back test platform according to claim 1, characterized in that: The multi-level protection module includes: An anti-counterflow protection unit, which is used to monitor the grid connection point power during discharge. If the power is less than or equal to the set threshold, the discharge is terminated and retried after a delay; The overcapacity protection unit is used to monitor the transformer load during charging. If the safe capacity threshold is exceeded, the charging power is reduced according to the gradient. The error-tolerant protection unit is used to monitor the PQ source power error. If it exceeds the limit, the retry mechanism is triggered. After failure, the abnormal PCS is isolated and the power is reallocated.

7. An off-grid energy storage counter-dragging test method, characterized in that, The following steps are involved: Off-grid mode triggering and switching: Real-time monitoring of the test load access signal in the peak shaving and valley filling mode to trigger the off-grid mode switch; Exit the peak-shaving and valley-filling strategy and shut down the PCS, and switch some PCS to the constant voltage source (VF) mode; Disconnect the grid-connected switch, start the VF source to build a stable voltage and frequency, and start the power tracking source (PQ) and the system under test in conjunction; VF / PQ dynamic coordination and power tracking: Dynamically allocate the ratio of VF source to PQ source according to converter performance; The PQ source output power is adjusted through the power automatic tracking algorithm, gradually expanding the power adjustment range of the system under test; Approach the full load demand of the system under test in a cyclic iteration manner; Intelligent SOC adjustment and charge and discharge control: Based on the current power of the system under test and the rated capacity of the energy storage system, the target SOC value is calculated and a safety margin is reserved; Select the charge and discharge template according to the target SOC value, and automatically perform constant current charging, constant voltage charging or constant power discharging operations; Real-time monitoring and dynamic adjustment of SOC to the target value during charging and discharging; Multi-level protection and feedback control: Real-time monitoring of grid connection point power, transformer load and PCS status; Trigger anti-backflow, anti-overcapacity and error tolerance protection according to the preset protection strategy; The protection signal is fed back to the charge and discharge control and power tracking process to dynamically terminate or adjust the operating status.

8. A method for off-grid energy storage counter-dragging test according to claim 7, characterized in that: In the automatic power tracking algorithm, the PQ source power is the total power divided by the number of VF sources plus 1.

9. A method for off-grid energy storage counter-dragging test according to claim 7, characterized in that: The target SOC value is the percentage of the difference to the rated capacity, minus a 5% reserve margin.

10. A method for off-grid energy storage tow test according to claim 7, characterized in that: The anti-reverse flow protection is triggered when the grid-connected point power is less than or equal to a set threshold, and the anti-overcapacity protection is triggered when the transformer load exceeds a safe capacity threshold.

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