Stability testing system for off-grid inverters managing battery SOC

Abstract

This invention discloses a stability testing system for managing battery SOC in an off-grid inverter, comprising an off-grid inverter and a battery pack, with the DC input terminal of the off-grid inverter connected to the battery pack; a first switching unit, through which the AC input terminal of the off-grid inverter is connected to the power grid; and multiple loads of different power and multiple switches corresponding to these loads, with the AC output terminal of the off-grid inverter connected to the multiple loads in parallel via the multiple switches. This invention uses multiple loads of different power to simulate the off-grid inverter in different grid-connected scenarios, monitoring the difference in battery SOC measured under different load power, thereby verifying the stability of battery SOC management by the off-grid inverter under different grid-connected scenarios, and ensuring that overcharging or over-discharging of the battery is avoided in different grid-connected scenarios.

Description

Technical Field

[0001] This utility model relates to the field of battery SOC management technology, and in particular to a stability testing system for managing battery SOC in an off-grid inverter. Background Technology

[0002] Lithium-ion battery pack systems for stationary electronic devices should be designed with a Battery Management Unit (BMU) or Battery Management System (BMS) to manage the batteries and battery packs, ensuring they operate within their designated operating range. The BMU / BMS should be able to detect and control abnormal states in the voltage, temperature, and current of the batteries and battery packs. State of Charge (SOC) refers to the percentage of remaining charge in a battery relative to its nominal capacity. One of the core management functions of the BMU / BMS is managing the battery's SOC, specifically including estimating the battery's SOC and controlling its charging and discharging based on this estimate to ensure the SOC remains within a reasonable range and prevent damage from overcharging or over-discharging.

[0003] An off-grid inverter is a stand-alone power system device primarily used for off-grid power supply in residential and commercial settings. Its core function is to convert direct current (DC) from solar panels or batteries into alternating current (AC) to supply the load. It is suitable for areas without grid access or for emergency power needs. A power supply system based on an off-grid inverter typically includes the inverter, a battery pack, and the load. The inverter's AC input is connected to the grid, its AC output is connected to the load, and its DC input is connected to the battery pack. Under normal grid connection (grid-connected) conditions, the off-grid inverter directly supplies grid power to the load and simultaneously charges the battery pack. If the grid is disconnected (off-grid), the inverter converts the battery pack's power into AC to supply the load. During operation, the off-grid inverter manages battery charge and discharge based on monitored battery state of charge (SOC) to prevent overcharging or over-discharging. This management is achieved through firmware installed in the off-grid inverter. To prevent battery damage from overcharging or over-discharging, it is essential to ensure the reliability of the battery charge / discharge management firmware in off-grid inverters. Industry practice for verifying the reliability of off-grid inverter battery charge / discharge management firmware typically involves designing a grid-connected system (i.e., a grid-connected scenario). This system includes a test load, and grid on / off simulations are performed. During the simulation, the charging and discharging process of the off-grid inverter's battery is tested to verify the reliability of the firmware. However, in real-world applications, off-grid inverters may be used in various grid-connected scenarios. Existing verification methods cannot determine the adaptability of off-grid inverters to different grid-connected scenarios, making it difficult to ensure that the battery is not damaged by overcharging or over-discharging. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to ensure that the off-grid inverter avoids overcharging or over-discharging of the battery under different grid-connected scenarios.

[0005] To address the aforementioned technical problems, this utility model provides a stability testing system for off-grid inverter-managed battery SOC, as follows: Includes an off-grid inverter and a battery pack, with the DC input terminal of the off-grid inverter connected to the battery pack; Includes a first switching unit, through which the AC input terminal of the off-grid inverter is connected to the power grid; The inverter includes multiple loads of different power ratings and multiple switches corresponding to each load. The AC output terminals of the off-grid inverter are connected to the multiple loads in parallel via multiple switches.

[0006] Furthermore, the first switching unit includes a first logic control module and a relay. Specifically, the AC input terminal of the off-grid inverter is connected to the power grid via the relay, and the first logic control module is connected to the relay control terminal.

[0007] Furthermore, it includes a second logic control module, which is connected to the control terminals of the plurality of switches respectively.

[0008] Furthermore, the first logic control module and the second logic control module have the same structure, specifically including an MCU and a memory and clock chip connected to the MCU.

[0009] Furthermore, the photovoltaic device is included, and the PV input terminal of the off-grid inverter is connected to the photovoltaic device.

[0010] Furthermore, it includes a host computer, which communicates with the off-grid inverter, the first logic control module, and the second logic control module.

[0011] Furthermore, the communication connection is specifically an RJ485 communication connection.

[0012] Furthermore, the power of the multiple loads decreases stepwise from the highest power of the off-grid inverter to 0.

[0013] This invention utilizes multiple loads of varying power to simulate off-grid inverters applied to different grid-connected scenarios. It can monitor the difference in battery SOC changes measured under different load power, thereby verifying the stability of battery SOC management by the off-grid inverter under different grid-connected scenarios. If the stability of battery SOC management by the off-grid inverter meets the standard, it means that its battery charge and discharge management firmware has high reliability and can ensure that overcharging or over-discharging of the battery is avoided under different grid-connected scenarios. Attached Figure Description

[0014] Figure 1This is a structural block diagram of an embodiment of the stability testing system for off-grid inverter-managed battery SOC provided by this utility model.

[0015] Figure 2 This is a structural block diagram of Embodiment 2 of the stability testing system for off-grid inverter management battery SOC provided by this utility model.

[0016] Figure 3 This is a structural block diagram of Embodiment 3 of the stability testing system for off-grid inverter-managed battery SOC provided by this utility model.

[0017] Figure 4 This is a block diagram of the logic control module of the stability test system for off-grid inverter-managed battery SOC. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] Example 1 like Figure 1 In the stability testing system for off-grid inverter battery SOC management, the DC input terminal of the off-grid inverter is connected to the battery pack. The off-grid inverter, acting as a battery management system, manages the battery pack SOC and monitors its value in real time. The testing system includes a relay as the first switching unit, through which the AC input terminal of the off-grid inverter is connected to the power grid. The system includes multiple loads of different power ratings and multiple parallel switches corresponding to each load. The AC output terminal of the off-grid inverter is connected to each load via these switches. The number and power of the loads required for the system are set according to the power of the off-grid inverter being tested; for example, the power of the loads decreases progressively from the highest power of the off-grid inverter to 0. This embodiment uses a 5kW off-grid inverter as an example, with the multiple loads specifically being 5kW, 4kW, 3kW, 2kW, 1kW, and 0kW loads.

[0020] The aforementioned testing system simulates different grid-connected power scenarios using multiple loads of varying power. During testing, it can switch between different grid-connected power scenarios to test the off-grid inverter, verifying the reliability of the off-grid inverter's battery charge / discharge management firmware under different grid-connected power scenarios. This ensures that the off-grid inverter avoids overcharging or over-discharging the battery under different grid-connected power scenarios. This embodiment verifies the reliability of the off-grid inverter's battery charge / discharge management firmware by testing the stability of the off-grid inverter's managed battery SOC. Specifically, the stability test of the off-grid inverter's managed battery SOC is performed using the aforementioned testing system, as follows: When connected to the grid, the off-grid inverter simultaneously supplies power to the load and charges the battery. When disconnected from the grid, it converts battery power into AC power to supply the load. To verify the reliability of the off-grid inverter's battery charge / discharge management firmware under different grid-connected scenarios, it is necessary to ensure that the off-grid inverter can operate in both battery charging and discharging states under each load power. Therefore, testers operated the relays in a cyclic on / off cycle of 60 minutes on and 30 minutes off, and performed a load switching operation each time the grid was disconnected, i.e., disconnecting the previously connected switch and connecting the next switch, thereby switching the load. During the test, each switch cyclically connected to its corresponding load. During the test, once the off-grid inverter detected a change in battery SOC, it saved the current SOC, the current time, and the current load power. To ensure reliable test results, a long-term test was required; in this embodiment, the test lasted for 3 days, with multiple testers working in shifts. After three days of testing, the testers use the SOC data list saved by the off-grid inverter during these three days to determine whether the stability of the battery SOC managed by the off-grid inverter meets the standard. Specifically, they calculate the difference between any two adjacent SOCs saved in time, and use the load power corresponding to the later SOC as the load power corresponding to the difference. If the calculated SOC differences are within a preset range, such as [0, 1%], the stability of the battery SOC managed by the off-grid inverter is considered to meet the standard, and the charge / discharge management firmware is reliable. If the SOC difference does not meet the preset range for each load power, the battery pack cells are considered damaged. If only a few load power values ​​have SOC differences that do not meet the preset range, the stability of the battery SOC managed by the off-grid inverter is considered to be substandard, and the charge / discharge management firmware is unreliable.

[0021] This invention utilizes multiple loads of varying power to simulate an off-grid inverter applied to different grid-connected scenarios. It can monitor the difference in battery SOC (State of Charge) measured under different load power, thereby verifying the stability of battery SOC management by the off-grid inverter in different grid-connected scenarios. By determining whether the difference in SOC under different grid-connected scenarios meets a preset range, the stability of battery SOC management by the off-grid inverter is judged. If the stability of battery SOC management by the off-grid inverter meets the standard, it means that its battery charge and discharge management firmware has high reliability and can ensure that overcharging or over-discharging of the battery is avoided in different grid-connected scenarios.

[0022] Example 2 like Figure 2As shown, in the stability test system for off-grid inverters managing battery SOC, the DC input terminal of the off-grid inverter is connected to the battery pack. The off-grid inverter acts as a battery management system to manage the battery pack SOC. The test system includes a first logic control module (serving as a first switching unit) and a relay. The AC input terminal of the off-grid inverter is connected to the power grid via the relay, and the first logic control module is connected to the relay control terminal. The test system includes a second logic control module, multiple loads of different power ratings, and multiple parallel switches corresponding to these loads. The AC output terminal of the off-grid inverter is connected to the aforementioned loads via these switches. The test system sets the required number and power of the loads according to the power of the off-grid inverter being tested; for example, the power of the multiple loads decreases progressively from the highest power of the off-grid inverter to 0. In this embodiment, a 5kW off-grid inverter is used as an example, and the multiple loads are specifically 5kW, 4kW, 3kW, 2kW, 1kW, and 0kW loads. In this embodiment, the first and second logic control modules have the same structure, as shown below. Figure 4 As shown, the logic control module includes an MCU and a memory and clock chip connected to the MCU. The test system includes a host computer, which is connected to the off-grid inverter, the first logic control module, and the second logic control module via RJ485 communication. This embodiment provides the hardware connection structure of the above test system. After software engineers program the host computer, the first logic control module, and the second logic control module in the hardware connection structure, they can use this test system to automatically test the stability of the off-grid inverter's managed battery SOC.

[0023] Before starting the test, the testers pre-configure a first preset cycle (stored in memory) in the first logic control module via the host computer, for example, configuring it to be on for 60 minutes and off for 30 minutes. They also configure a second preset cycle (stored in memory) in the second logic control module, for example, configuring it as "Switch S0 on for 30 minutes → Switch S1 on for 30 minutes → Switch S2 on for 30 minutes → Switch S3 on for 60 minutes → Switch S4 on for 30 minutes → Switch S5 on for 30 minutes". The second preset cycle needs to be set in conjunction with the first preset cycle, ensuring that the off-grid inverter exhibits both battery charging and discharging conditions under each load power during the grid's on / off cycle. After configuring the first and second preset cycles, the testers can use the test system to automatically test the stability of the off-grid inverter's managed battery SOC. The test process is as follows: To ensure reliable test results, a long-term test is required; in this embodiment, the test period is 7 days. During these 7 days, the host computer instructs the first logic control module MCU to control the relays to cycle on and off according to the first preset cycle (60 minutes on, 30 minutes off) stored in its memory, and instructs the second logic control module MCU to cycle on each switch according to the second preset cycle (switch S0 on for 30 minutes → switch S1 on for 30 minutes → switch S2 on for 30 minutes → switch S3 on for 60 minutes → switch S4 on for 30 minutes → switch S5 on for 30 minutes), thereby controlling the off-grid inverter output to cycle-switch to connect to loads of different power. When connected to the grid, the off-grid inverter uses the grid to power the load and charges the battery; when disconnected from the grid, it converts the battery's electrical energy into AC power to power the load. During the test, once the off-grid inverter detects a change in battery SOC, it saves the current SOC, the current time, and the current load power and uploads this information to the host computer. After 7 days of testing, the host computer calculates the difference between any two adjacent SOC records based on the SOC data recorded in the SOC data list during these 7 days. The load power corresponding to the later SOC is taken as the load power corresponding to the difference. The host computer uses the calculated SOC differences to determine whether the stability of the off-grid inverter's managed battery SOC meets the standard. Specifically, if the calculated SOC differences are within a preset range, such as [0, 1%], the stability of the off-grid inverter's managed battery SOC is considered to be up to standard, and the charge / discharge management firmware is reliable. If SOC differences for each load power do not meet the preset range, the battery pack cells are considered damaged. If only a few load power values ​​have SOC differences that do not meet the preset range, the stability of the off-grid inverter's managed battery SOC is considered to be down to standard, and the charge / discharge management firmware is unreliable.

[0024] This invention utilizes multiple loads of varying power to simulate an off-grid inverter applied to different grid-connected scenarios. It can monitor the difference in battery SOC (State of Charge) measured under different load power, thereby verifying the stability of battery SOC management by the off-grid inverter in different grid-connected scenarios. By determining whether the difference in SOC under different grid-connected scenarios meets a preset range, the stability of battery SOC management by the off-grid inverter is judged. If the stability of battery SOC management by the off-grid inverter meets the standard, it means that its battery charge and discharge management firmware has high reliability and can ensure that overcharging or over-discharging of the battery is avoided in different grid-connected scenarios.

[0025] Example 3 like Figure 3As shown, this embodiment is largely the same as Embodiment 2, except that in this test system, the PV input terminal of the off-grid inverter is connected to a photovoltaic device, which can supply power to the load and / or charge the battery. The testing process in this embodiment is the same as in Embodiment 2; please refer to the above.

[0026] Because the voltage generated by a photovoltaic (PV) device fluctuates due to sunlight, the addition of a PV device to the test system in this embodiment complicates the battery charging and discharging scenarios under various grid-connected conditions during testing. For example, in grid-connected mode: both the PV device and the grid may supply power to the load, with the grid charging the battery; the PV device may supply power to the load alone, with the grid charging the battery; or the PV device may supply power to the load while simultaneously charging the battery. In grid-disconnected mode: both the PV device and the battery may supply power to the load; the PV device may supply power to the load alone, with the battery neither charging nor discharging; or the PV device may supply power to the load while simultaneously charging the battery. Therefore, the test system in this embodiment can simulate the charging and discharging process of the battery in an off-grid inverter under more complex grid-connected scenarios, resulting in more accurate reliability test results for the battery charging and discharging management firmware of the off-grid inverter.

[0027] The above description is merely an embodiment of the present invention and does not limit the scope of patent protection. Any non-substantial changes or substitutions made by those skilled in the art based on the present invention will still fall within the scope of patent protection.

Claims

1. A stability testing system for off-grid inverter-managed battery SOC, characterized in that: Includes an off-grid inverter and a battery pack, with the DC input terminal of the off-grid inverter connected to the battery pack; Includes a first switching unit, through which the AC input terminal of the off-grid inverter is connected to the power grid; The inverter includes multiple loads of different power ratings and multiple switches corresponding to each load. The AC output terminals of the off-grid inverter are connected to the multiple loads in parallel via multiple switches.

2. The stability testing system for off-grid inverter managed battery SOC as described in claim 1, characterized in that, The first switching unit includes a first logic control module and a relay. The AC input terminal of the off-grid inverter is specifically connected to the power grid via the relay, and the first logic control module is connected to the relay control terminal.

3. The stability testing system for off-grid inverter managed battery SOC as described in claim 2, characterized in that, It includes a second logic control module, which is connected to the control terminals of the plurality of switches respectively.

4. The stability testing system for off-grid inverter managed battery SOC as described in claim 3, characterized in that, The first logic control module and the second logic control module have the same structure, specifically including an MCU and a memory and clock chip connected to the MCU.

5. The stability testing system for off-grid inverter managed battery SOC as described in any one of claims 1 to 4, characterized in that, It includes a photovoltaic device, and the PV input terminal of the off-grid inverter is connected to the photovoltaic device.

6. The stability testing system for off-grid inverter managed battery SOC as described in claim 3 or 4, characterized in that, It includes a host computer, which communicates with the off-grid inverter, the first logic control module, and the second logic control module.

7. The stability testing system for off-grid inverter managed battery SOC as described in claim 6, characterized in that, The communication connection is specifically an RJ485 communication connection.

8. The stability testing system for off-grid inverter managed battery SOC as described in claim 1, characterized in that, The power of the multiple loads decreases stepwise from the highest power of the off-grid inverter to 0.

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