Distributed photovoltaic energy storage system

Abstract

This utility model discloses a distributed photovoltaic energy storage system, belonging to the field of photovoltaic energy storage technology, aiming to solve the problems of high thermal runaway risk, low conversion efficiency, and insufficient synergy between photovoltaic and energy storage in existing centralized energy storage technologies. The system includes multiple distributed energy storage PACK modules and an inverter. Each PACK module integrates photovoltaic modules, an energy storage battery pack, a DC MPPT DC / DC charge / discharge controller, and a BMS. Multiple PACK modules are connected in series to form a series group, and the output of the series group is connected to the inverter to achieve AC / DC conversion. Intelligent control and monitoring can also be achieved through an EMS communication manager and a power detector. This utility model reduces the risk of thermal runaway through a distributed design, improves efficiency by integrating an MPPT controller, adapts to traditional installation methods and supports flexible expansion, and can achieve efficient synergy and peak shaving between photovoltaic and energy storage, thereby improving the economic efficiency of energy utilization.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic energy storage system technology, specifically to a distributed photovoltaic energy storage system that uses solar photovoltaic panels in conjunction with energy storage batteries. Background Technology

[0002] In the field of photovoltaic energy storage technology, the mainstream technical solutions currently include grid-side AC energy storage, DC-side DC energy storage, and photovoltaic grid-connected systems. The technical characteristics and existing defects of these three types of solutions are as follows: 1. Grid-side AC energy storage In this solution, the energy storage battery is connected to the AC bus via an inverter, enabling direct energy interaction with the power grid and achieving charge and discharge control. Its core advantages lie in its strong adaptability to existing AC power grids and loads, high degree of standardization, and good safety in low-voltage scenarios. It is suitable for traditional power systems, home energy storage, and other scenarios, and supports grid-connected and islanded operation.

[0003] However, this solution has significant drawbacks: energy conversion requires multiple steps of "DC → AC → DC", resulting in low conversion efficiency, slow response speed, and high cost; energy storage uses centralized battery cabinets, with a large number of energy storage batteries integrated in a single cabinet. Once thermal runaway occurs, it can easily cause large-scale fires that are difficult to extinguish. Therefore, it requires independent energy storage station space and should be far away from surrounding buildings, which limits installation and maintenance.

[0004] 2. DC-side DC energy storage This scheme couples photovoltaic modules to energy storage batteries via a DC bus. The DC power output from the photovoltaic system can be directly supplied to the energy storage batteries. Grid connection can be achieved with only one inverter. The overall system efficiency is typically 5%-15% higher than that of AC-side energy storage, reducing energy conversion losses.

[0005] However, its drawbacks are also prominent: in order to improve energy transmission efficiency, high-voltage DC design is often used, but the arc of DC is more difficult to extinguish than that of AC, which increases the technical difficulty and cost; and it still uses centralized battery energy storage cabinets, which face the same thermal runaway risk as AC side energy storage, requiring independent energy storage stations far away from buildings, thus limiting the applicable scenarios.

[0006] 3. Photovoltaic grid-connected system This system directly connects solar photovoltaic power generation to the public power grid, enabling local power consumption or transmission to the grid. It has advantages such as low cost, high efficiency, simple construction, and easy maintenance, and is currently the mainstream form of photovoltaic application.

[0007] However, the system relies on the power grid for operation, and the stability of power generation is significantly affected by sunlight. Furthermore, due to the lack of energy storage, the electricity needs to be consumed in real time, which cannot meet the peak-shaving demand. Excess electricity can only be fed into the grid at a low price, while at night or on cloudy days, electricity needs to be purchased from the grid at a high price. There is a contradiction between "curtailment of solar power" and "purchasing electricity", which limits its economic efficiency and applicability.

[0008] In summary, existing technical solutions have not solved the problems of "thermal runaway safety risks of centralized energy storage", "balance between energy conversion efficiency and cost" and "efficient synergy between photovoltaics and energy storage". There is an urgent need for a distributed photovoltaic energy storage technology solution that is structurally simple, safe and reliable, highly efficient and low cost. Utility Model Content

[0009] To address the aforementioned issues, this utility model aims to provide a distributed photovoltaic energy storage system to solve the problems of high thermal runaway risk, low conversion efficiency, and insufficient synergy between photovoltaics and energy storage in existing centralized energy storage technologies.

[0010] The distributed photovoltaic energy storage system of this utility model includes: Multiple distributed energy storage PACK modules, and inverter devices; Each of the distributed energy storage PACK modules includes photovoltaic modules, energy storage battery packs, DC MPPT DC / DC charge / discharge controllers, and BMS battery management systems. The output terminal of the photovoltaic module is connected to the input terminal of the DC MPPT DC / DC charge / discharge controller, the output terminal of the DC MPPT DC / DC charge / discharge controller is connected to the input terminal of the energy storage battery pack, and the BMS battery management system is electrically connected to the energy storage battery pack to monitor and manage its charge and discharge status. Multiple distributed energy storage PACK modules are connected in series via DC lines to form a series group. The output terminal of the series group is connected to the DC input terminal of the inverter, which is used to convert DC power into AC power.

[0011] Preferably, the output voltage range of the series group is 200V-1000V, which is compatible with the MPPT voltage range of the inverter.

[0012] Preferably, each of the distributed energy storage PACK modules contains 1-2 photovoltaic modules and the energy storage battery pack has a capacity of 2KW-6KW.

[0013] Preferably, multiple series groups are connected in parallel and then connected to the DC input terminal of the inverter. The inverter is equipped with multiple MPPT interfaces, and each series group is connected to one MPPT interface.

[0014] Preferably, the photovoltaic module and the distributed energy storage PACK module are installed close to each other, with the photovoltaic module installed above the support frame and the distributed energy storage PACK module installed below the photovoltaic module.

[0015] Preferably, it also includes an EMS communication manager, which is connected to the DC MPPT DC / DC charge / discharge controller, the BMS battery management system, and the inverter via an RS485 communication interface.

[0016] Preferably, it also includes a power detector, which monitors the user load power and the grid power supply power through a current transformer, and is connected to the EMS communication manager through an RS485 communication interface.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. The distributed low-capacity PACK module design, combined with the voltage, current, and temperature detection and charge / discharge protection circuit of the BMS, can significantly reduce the risk of thermal runaway in centralized energy storage, avoid overcharging and over-discharging of the battery, effectively extend battery life, and further improve system safety.

[0018] 2. Each PACK module integrates a DC MPPT DC / DC charge / discharge controller, reducing energy conversion steps. At the same time, the MPPT control circuit tracks the maximum power point of the photovoltaic, significantly improving the photovoltaic energy storage efficiency by 5%-15%.

[0019] 3. Photovoltaic modules and distributed PACK modules can be installed nearby (e.g., integrated on the upper and lower brackets), eliminating the need for a separate energy storage station. The installation method is compatible with traditional photovoltaic systems, significantly reducing site limitations and construction costs, and adapting to various installation needs.

[0020] 4. Multiple PACK modules are connected in series to form a series group, which can adapt to the voltage requirements of the inverter. At the same time, it supports multiple series groups to be connected in parallel to the multiple MPPT interfaces of the inverter. It can not only use the photovoltaic grid-connected system installation method to reduce the retrofit cost, but also flexibly expand the system power (such as from 10KW to 100KW), adapting to different scale scenarios such as residential, industrial and commercial.

[0021] 5. Photovoltaic and energy storage can operate in close coordination to solve the problem of peak shaving in traditional systems. Energy utilization efficiency can be improved through charging and discharging scheduling during peak and valley periods, and dependence on the power grid can be reduced. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a distributed photovoltaic energy storage system.

[0024] Figure 2 This is a schematic diagram of a distributed energy storage PACK module.

[0025] Figure 3 This is a schematic diagram showing the connection between photovoltaic modules and distributed energy storage PACK modules.

[0026] Figure 4 This is a schematic diagram of the extended connection of multiple cascade groups.

[0027] In the diagram: Distributed energy storage PACK module 10, photovoltaic module 11, DC MPPT DC / DC charge / discharge controller 12, BMS battery management system 13, energy storage battery pack 14, DC cable 15, support beam 16, inverter 20, EMS communication manager 21, RS485 bus 22, power detector 23, user load 30, power grid 40. Detailed Implementation

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0029] This embodiment discloses a distributed photovoltaic energy storage system, suitable for scenarios such as residential rooftops and industrial / commercial buildings. Its overall structure is as follows: Figure 1 As shown, it includes multiple distributed energy storage PACK modules, inverters, and can be optionally equipped with an EMS communication manager and power detector. The specific implementation details of each component are as follows: 1. Composition and structure of distributed energy storage PACK modules Each distributed energy storage PACK module 10 is an independent functional unit (e.g., Figure 2 As shown in the figure, this is the core of the system to realize "distributed energy storage", which specifically includes: Photovoltaic module 11: A 640W monocrystalline silicon photovoltaic panel is selected. Each 1-2 photovoltaic modules (preferably) correspond to one energy storage PACK module. In this embodiment, one photovoltaic module is matched with one PACK. The output terminal of the photovoltaic module is connected to a DC MPPTDC / DC charge and discharge controller.

[0030] Energy storage battery pack 14: It adopts lithium iron phosphate batteries (multiple batteries connected in series) with a capacity of 2KW-6KW. In this embodiment, 40V 40Ah, i.e. 1.6KW, is selected to meet the energy storage needs of Jiangsu's spring and autumn peak-valley electricity price scenario.

[0031] DC MPPT DC / DC Charge / Discharge Controller 12: Integrates MPPT control circuit. The input terminal is connected to the output terminal of the photovoltaic module via a waterproof plug, and the output terminal is connected to the input terminal of the energy storage battery pack of the adjacent distributed energy storage PACK module via a copper busbar. The MPPT control circuit can detect the voltage-current curve of the photovoltaic module in real time and dynamically match the maximum power point by adjusting the PWM duty cycle. For example, when the light intensity changes, it automatically adjusts the charging voltage from 40V to 44.57V and the current from 10A to 14.33A.

[0032] BMS Battery Management System 13: Includes a voltage detection module (sampling accuracy ±0.5%), a current detection module (Hall sensor), a temperature detection module (NTC thermistor), and a charge / discharge protection circuit (relay + fuse); the voltage / current / temperature detection modules are respectively connected to the positive and negative terminals of the energy storage battery pack and the surface of the cells, and the charge / discharge protection circuit is connected in series between the energy storage battery pack and the MPPT controller; when the detected voltage is >44V (overcharge), voltage <32V (over-discharge), or temperature >60℃, the protection circuit automatically cuts off the circuit to avoid battery damage.

[0033] See Figure 3 The photovoltaic module 11 and the distributed energy storage PACK module 10 are integrated and installed in close proximity. The photovoltaic module 11 is installed on the roof or ground via a triangular bracket, with the panel tilted 30° to the south (to maximize sunlight reception); the distributed energy storage PACK module 10 is fixed to the bracket beam 16 below the photovoltaic module via clips or bolts, with a distance of <1 meter from the photovoltaic module (to reduce DC line loss, line resistance <0.5Ω), and the installation method is compatible with traditional photovoltaic systems.

[0034] 2. Formation of the series connection group and its connection with the inverter. Series Group Formation: Individual distributed energy storage PACK modules 10 are connected in series via DC cables 15 to form a series group. In this embodiment, the output voltage range of the series group is 200V-1000V, which is compatible with the MPPT voltage range of the inverter.

[0035] Inverter 20: The Huawei SUN2000 100KTL-M2 photovoltaic inverter is selected. Its DC input terminal is equipped with 10 MPPT interfaces (each MPPT voltage range 200V-1000V). The output terminal of the series group is connected to one of the MPPT interfaces of the inverter through the combiner box. The inverter converts DC power to AC400V AC power and outputs it to the user load 30 or the power grid 40.

[0036] See Figure 4 Extended connection of multiple series groups: To adapt to higher power scenarios (such as industrial and commercial), 10 of the above series groups (each with 18 PACK modules) are connected to the 10 MPPT interfaces of the inverter to form a parallel structure, and the total system power can reach 100KW.

[0037] 3. Connection of EMS communication manager and power detector EMS Communication Manager 21: Employs an industrial-grade RS485 bus module, connecting all PACK modules' BMS battery management system and MPPT controller via an RS485 bus 22 (each device is assigned a unique address code, such as 001-180; the bus supports up to 256 nodes to meet expansion needs). Simultaneously, it connects to the inverter via another RS485 management bus. Its core function is to collect data such as photovoltaic output, battery SOC, and inverter status, and to issue charging and discharging commands.

[0038] The power detector 23 collects current signals through a current transformer (which runs through the cables on the grid side and the load side), converts them into power data (accuracy ±1%), and connects to the EMS communication manager 21 through an RS485 communication interface to upload the data to the EMS for determining the interaction status between the user's load power and the grid (such as whether reverse power is being supplied).

[0039] 4. System operation process (based on Jiangsu's spring and autumn peak-valley electricity pricing scenario, taking the power of a series of 18 modules as an example): 1) 6:00-10:00 (off-peak hours): The EMS communication manager 21 detected that the user load power was approximately 3KW through the power detector 23, and the grid power was ≥0 (no reverse power supply).

[0040] The EMS communication manager (EMS) 21 issues the following command: disable the energy storage function of all PACK modules (the BMS controls the charging and discharging protection circuit to disconnect the charging circuit), and connect the output of photovoltaic module 11 directly to the series group via the MPPT controller (without passing through the energy storage battery pack); the total DC power of the 18 photovoltaic modules in series is approximately 18 × 640W = 11.52KW, which outputs 11.52KW AC after being connected to the inverter, and is given priority to supply the user load (3KW), with the remaining 8.52KW going to the grid (there is no energy storage demand during this period, and the traditional photovoltaic grid connection mode is used).

[0041] 2) 10:00-14:00 (off-peak hours): When EMS detects the start of the valley period, it issues the following commands: the inverter stops (disconnects AC output), the charge and discharge protection circuit of the PACK module closes, and the photovoltaic module charges the energy storage battery pack through the MPPT controller.

[0042] Charging parameters of a single PACK module: The MPPT controller tracks the photovoltaic peak voltage of 44.57V and the current of 14.33A, with a charging power of approximately 640W; the total charging power of 18 photovoltaic modules connected in series matches the total photovoltaic output (18×640W=11.52KW).

[0043] BMS monitors battery status in real time: when the SOC reaches 90% (approximately 1.44 kWh / cell), it sends feedback to EMS via RS485. EMS then controls the corresponding PACK module to stop charging (MPPT controller switches to standby) to prevent overcharging.

[0044] 3) 14:00-15:00 (regular hours): If all PACK modules have reached 100% SOC (1.6 kW·h / module), the EMS command is: the inverter is turned on, the photovoltaic modules directly supply power to the load (without energy storage), the output power matches the load (e.g., 3 kW), and the excess power is fed into the grid.

[0045] If there are still PACK modules that are not fully charged, continue charging until they are fully charged before starting the inverter.

[0046] 4) 15:00-22:00 (Peak Hour): When the user load increases to 8KW, the EMS command is to discharge the PACK module (the BMS control and protection circuit switches to the discharge circuit), and the photovoltaic modules and energy storage battery pack are connected in parallel to output to the series group (total DC power = real-time photovoltaic output + energy storage discharge power).

[0047] Power regulation logic: The EMS monitors the grid-side power in real time through a power detector (ensuring ≥0 and no reverse). If the inverter's full-load output is 11.52KW > the user's load of 8KW, the inverter's output power is reduced to 8KW, and the energy storage discharge power is adjusted (e.g., 3KW photovoltaic output + 5KW energy storage discharge) to ensure that the electricity is fully absorbed by the user, thus solving the problem of peak regulation in traditional systems.

[0048] 5. Exception handling: If the BMS of a certain PACK module detects a temperature of 60°C, it immediately cuts off its own charging and discharging circuit and sends an alarm signal to the EMS via RS485. After receiving the signal, the EMS displays the fault location on the local touch screen (e.g., "3rd string, 5th module"), without affecting the operation of other modules (demonstrating the security advantages of distributed design).

[0049] The preferred embodiments of this utility model disclosed above are merely illustrative of the present utility model. These preferred embodiments do not exhaustively describe all details, nor do they limit the utility model to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to better understand and utilize it. This utility model is limited only by the claims and their full scope and equivalents.

Claims

1. A distributed photovoltaic energy storage system, characterized in that, include: Multiple distributed energy storage PACK modules, and inverter devices; Each of the distributed energy storage PACK modules includes photovoltaic modules, energy storage battery packs, DC MPPT DC / DC charge / discharge controllers, and BMS battery management systems; The output terminal of the photovoltaic module is connected to the input terminal of the DC MPPT DC / DC charge / discharge controller, the output terminal of the DC MPPT DC / DC charge / discharge controller is connected to the input terminal of the energy storage battery pack, and the BMS battery management system is electrically connected to the energy storage battery pack to monitor and manage its charge and discharge status. Multiple distributed energy storage PACK modules are connected in series via DC lines to form a series group. The output terminal of the series group is connected to the DC input terminal of the inverter, which is used to convert DC power into AC power.

2. The distributed photovoltaic energy storage system according to claim 1, characterized in that, The output voltage range of the series group is 200V-1000V, which is compatible with the MPPT voltage range of the inverter.

3. The distributed photovoltaic energy storage system of claim 1, wherein, Each of the distributed energy storage PACK modules contains 1-2 photovoltaic modules and the energy storage battery pack has a capacity of 2KW-6KW.

4. The distributed photovoltaic energy storage system of claim 1, wherein, Multiple series groups are connected in parallel and then connected to the DC input terminal of the inverter. The inverter is equipped with multiple MPPT interfaces, and each series group is connected to one MPPT interface.

5. The distributed photovoltaic energy storage system of claim 1, wherein, The photovoltaic modules and distributed energy storage PACK modules are installed close to each other, with the photovoltaic modules installed above the support frame and the distributed energy storage PACK modules installed below the photovoltaic modules.

6. The distributed photovoltaic energy storage system of claim 1, wherein, It also includes an EMS communication manager, which is connected to the DC MPPT DC / DC charge / discharge controller, the BMS battery management system, and the inverter via an RS485 communication interface.

7. The distributed photovoltaic energy storage system of claim 6, wherein, It also includes a power detector, which monitors the user load power and the grid power supply power through a current transformer and is connected to the EMS communication manager through an RS485 communication interface.

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