Building block type modularized miniature light storage power generation system and method

Abstract

The invention provides a building block type modularized miniature optical storage power generation system and a control method thereof. The system adopts a modular building block type topological structure and comprises a photovoltaic power generation module, an energy storage battery module and a power conversion module which can be flexibly increased and decreased, and all the modules are connected through a common direct current bus and are coordinated by a control unit to work. The photovoltaic power generation module outputs electric energy to a direct current bus to supply load and charges a battery when redundant electric energy exists, the energy storage battery module stabilizes photovoltaic power fluctuation on a direct current side and discharges and supplies power when illumination is insufficient or a grid is disconnected, and the inverter module realizes direct current and alternating current bidirectional or direct current and alternating current unidirectional conversion to provide alternating current output in a grid-connected or off-grid mode. Various modules (the MPPT module, the battery module and the inverter) of the system all have plug-and-play functions, have redundant fault-tolerant capability and can be flexibly expanded or cut within the range of 300W-10kW according to requirements, and the reliability and the energy utilization efficiency of the system are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of distributed photovoltaic power generation and energy storage technology, and in particular to a building block modular micro photovoltaic storage power generation system and method. Background Art

[0002] As an important form of renewable energy, solar photovoltaic power generation has been widely used in industrial, commercial, and residential scenarios. The current mainstream photovoltaic system solutions mainly include the following three types: Figure 1 Centralized all-in-one solution: PV strings are connected to the grid or used to charge batteries via a centralized inverter (commonly used for inverters above 100kW). A failure of the all-in-one inverter shuts down the entire system, and the capacity is fixed, making expansion expensive.

[0003] Figure 2 ,Micro-inverter distributed solution: Each component is equipped with a micro-inverter and is independently connected to the grid. Local shading does not affect the overall situation, but the energy storage device needs to be configured additionally, and the overall cost of the system is relatively high.

[0004] Figure 3 Outdoor discrete independent power supply: photovoltaic panel + battery + boost / inverter integrated, only suitable for special scenarios of a few watts to 500W, difficult to grid-connect or expand.

[0005] In summary, the 300W-10kW segment lacks a standardized solution that is both grid-connected and off-grid capable, and easily scalable. Authorized Chinese invention patent CN106788140B proposes a "modular common DC bus photovoltaic energy storage system." While this introduces the concept of a modular DC bus, it still suffers from the following issues in low-power scenarios: a) The module interface is complex and blind plug-in expansion is inconvenient; b) Over-reliance on the central EMS, resulting in insufficient system robustness in the event of a single point of failure; c) On-grid / off-grid switching requires external devices, and on-site wiring is complicated. Summary of the Invention

[0006] The purpose of the present invention is to provide a modular micro-photovoltaic power generation system and method in a building block-type manner to address the shortcomings of the existing technology, aiming to solve the problem that the existing technology lacks a standardized system in the power range of 300W-10kW that is easy to deploy, can be gradually expanded, and has highly reliable on / off-grid capabilities.

[0007] The present invention achieves the above-mentioned object through the following technical solutions: a modular micro-photovoltaic power generation system of building block type, comprising: at least one photovoltaic power generation module, at least one energy storage battery module and at least one power conversion module, and provided with a control unit for coordinating the operation of each module; The photovoltaic power generation module includes photovoltaic modules and a DC / DC boost converter, configured to boost the DC power output by the photovoltaic modules to a predetermined DC bus voltage and then feed it into a common DC bus. The energy storage battery module includes a battery pack and a bidirectional DC / DC converter, configured to draw power from the DC bus to charge the battery or boost the battery power and feed it into the DC bus. The power conversion module includes a bidirectional DC / AC converter, one end of which is connected to the DC bus and the other end is connected to the AC bus and can be connected to the power grid and AC loads. In grid-connected mode, the converter is configured to invert DC bus power into AC power and output it to the AC bus. In off-grid mode, the converter is configured to invert DC bus power into independent AC power and supply it to local loads. Furthermore, the converter is capable of rectifying the AC power into DC power and inputting it into the DC bus when the grid is powered. The control unit is configured to monitor the DC bus voltage and current and the status of each module, and control the coordinated operation of the above modules according to a preset strategy, so that the system maintains a stable DC bus voltage under different operating conditions and provides continuous external power output.

[0008] A modular micro photovoltaic power generation system, comprising: At least one photovoltaic power generation module, each of which converts solar energy through a DC / DC module or MPPT and then connects it to a public DC bus; at least one energy storage battery module, configured to absorb electrical energy from the DC bus in a charging state and to provide electrical energy to the DC bus in a discharging state; At least one power conversion module (inverter), one side of which is connected to the DC bus and the other side of which is connected to the AC bus and can be electrically connected to the power grid or AC load, and is used to switch between grid-connected mode and off-grid mode to perform DC-AC bidirectional energy conversion or unidirectional energy conversion; The control unit is used to monitor the voltage and current of the DC bus and the AC bus and the operating status of each module, and coordinate the operating mode and power distribution of the photovoltaic power generation module, the energy storage battery module and the power conversion module according to a preset strategy to ensure normal operation in the photovoltaic power generation state, the DC / AC power generation state, the AC / DC charging state or the photovoltaic charging / power generation state.

[0009] Furthermore, a slot-type MPPT module chassis is provided, and a plurality of blind-insertion slots are arranged on the front panel of the chassis, and a power contact, a CAN communication contact and a SYNC synchronization contact are sequentially arranged in each slot; Each photovoltaic power generation module is equipped with a pluggable MPPT control board. The DC output terminal, communication terminal and synchronization terminal of the MPPT control board are electrically connected to the corresponding contacts in the slot through a blind-plug connector, and are electrically connected to the photovoltaic power generation module and connected in parallel to the DC bus.

[0010] Furthermore, positive and negative copper bars are arranged side by side inside the slot-type MPPT module chassis to form the DC bus; A CAN communication bus and a SYNC synchronization bus are arranged in parallel with the blind-plug slots, wherein the SYNC synchronization bus is connected to the synchronization port of each MPPT control board and is used to transmit synchronization pulses with a period of 10ms and a pulse width of 5µs to achieve multi-board phase synchronization; the CAN communication bus is connected to each MPPT control board and the control unit and is used to broadcast reference parameters and complete master-slave role determination.

[0011] The MPPT control board is used to adopt the exit specified transfer mode (when supported by the hardware) or the remaining working modules adopt the adjacent principle setting mode with the original master MPPT board when the master MPPT board fails or exits, and take over the rights of the master MPPT board. At this time, the new master MPPT board automatically changes the passive receiving SYNC signal mode to the active sending SYNC mode, and the working modes of the other slave boards remain unchanged; at the same time, each time the photovoltaic power generation module is restarted, the first MPPT control board started automatically becomes the master MPPT board.

[0012] Furthermore, each energy storage battery module includes a battery pack, a bidirectional DC / DC converter, and a battery management system (BMS); The positive and negative electrodes of the battery pack are directly connected in parallel to the DC busbar via a quick-swap DC connector; The battery management system is electrically connected to the CAN communication bus via an isolated CAN transceiver to collect and report battery voltage, temperature and state of charge.

[0013] Furthermore, when CAN communication is abnormal, the battery management system automatically adjusts the charge and discharge power of the bidirectional DC / DC converter according to a preset droop curve based on the detected DC bus voltage to maintain the DC bus voltage within a safe range.

[0014] Furthermore, the power conversion module is provided with an on-grid / off-grid switching unit, which is composed of a grid-connected relay, a bypass contactor and a drive control circuit; when it is detected that the voltage or frequency of the AC bus deviates from the rated range, the drive control circuit disconnects the grid-connected relay and closes the bypass contactor within 20ms, so that the power conversion module enters the off-grid inverter mode.

[0015] Furthermore, when at least two power conversion modules are connected in parallel to the same AC bus, each power conversion module performs masterless synchronization according to a uniformly set voltage-frequency droop coefficient; if any of the power conversion modules fails and exits operation, the remaining power conversion modules automatically increase the output power according to the droop coefficient to maintain the voltage and frequency stability of the AC bus.

[0016] A photovoltaic power generation method comprises the following steps: Module access and identification steps: connect the photovoltaic power generation module, energy storage battery module and power conversion module in parallel to the DC bus through the standard interface and establish communication with the control unit; Grid-connected operation steps: When the grid is normal, the control unit synchronizes the power conversion module with the grid, maintains the DC bus voltage within the target range, and dispatches the output power of the photovoltaic power generation module and the charging power of the energy storage battery module in real time based on the DC bus voltage; Off-grid operation steps: When the grid loses power or is in an independent power supply scenario, the control unit drives the on-grid / off-grid switching unit to disconnect the power conversion module from the grid and maintain local AC output. Each energy storage battery module discharges or stands by according to the droop characteristics to balance the DC bus power; Mode switching step: When it is detected that the grid is restored and the synchronization conditions are met, the control unit first synchronizes the AC bus to the grid, and then closes the on / off-grid switching unit to allow the power conversion module to smoothly restore grid connection and re-execute the grid connection operation step.

[0017] Furthermore, in the grid-connected operation step, when the DC bus voltage is higher than the upper threshold, the control unit instructs the energy storage battery module to enter a constant voltage charging mode; when the DC bus voltage is lower than the lower threshold and the grid is available, the control unit instructs the power conversion module to take power for boost compensation; otherwise, the control unit instructs the energy storage battery module to increase discharge power according to a droop curve; During the off-grid operation step, the control unit selects a power conversion module as the main inverter source to output the reference voltage and frequency. The remaining power conversion modules use voltage-frequency droop control to adjust their respective output powers according to the monitored deviation to realize a masterless synchronous parallel system.

[0018] Furthermore, during off-grid operation, when the energy storage battery module reaches its upper limit and the load power is less than the output power of the photovoltaic power generation module, the control unit limits the photovoltaic power by offsetting the MPPT target voltage of the photovoltaic power generation module to prevent the DC bus voltage from being too high; Before the grid-connected switching in the mode switching step, the control unit gradually adjusts the active and reactive outputs of each power conversion module at a current limiting rate of 10% / s, and smoothly restores the grid-connected operation after the grid-connected relay is closed.

[0019] Beneficial effects of the present invention: (1) The modular blind-plug design enables photovoltaic, energy storage, and inverter modules to be added or replaced as needed, with low initial investment and one-step capacity expansion, solving the problem of centralized capacity expansion. Specifically, the photovoltaic power generation module, energy storage battery module, and power conversion module are connected to the DC busbar through a unified blind-plug interface, allowing for plug-and-play expansion or replacement at any time, avoiding large-scale shutdowns and complex wiring, and greatly reducing expansion and maintenance costs.

[0020] (2) Each photovoltaic module has its own MPPT, which is combined with the battery side droop control to improve the power generation utilization rate. Specifically, each photovoltaic power generation module is equipped with an independent MPPT control board, and cooperates with the control management unit through the CAN bus to track the optimal output of each component in real time. At the same time, the energy storage battery module droop control in claim 5 (which can also be self-adjusted when there is no CAN) can effectively smooth out the photovoltaic output fluctuation and improve the power generation utilization rate.

[0021] (3) The power conversion module has a built-in on-grid / off-grid switching unit. Multiple inverters are connected in parallel. When the grid loses power within a certain threshold, the inverter switches to off-grid mode without interruption of power supply. Specifically, the on-grid relay and bypass contactor are integrated inside the power conversion module. After detecting grid anomalies at the millisecond level, the inverter can automatically switch to off-grid inverter mode, achieving seamless switching and continuous power supply, effectively eliminating the problem of power outages and load interruptions.

[0022] (4) The control unit is combined with module autonomy. Even if the communication is abnormal, each module can still self-regulate according to the bus voltage, and the system robustness is high. Specifically, even if the CAN communication is abnormal or the control management unit is unavailable, each module can self-adjust the MPPT or discharge power based on the DC bus voltage or AC bus frequency, ensuring that the basic power supply function does not rely on a single center, significantly improving the system robustness.

[0023] (5) Standard interface + no need for professional wiring, making the installation threshold extremely low for developing regions or home users. Specifically, it adopts a unified blind-plug DC and communication interface, making on-site installation as simple as "building blocks", reducing professional wiring and debugging, so that small and medium-sized users can also easily deploy and maintain the solar storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the existing traditional centralized photovoltaic energy storage power generation system.

[0025] Figure 2 Schematic diagram of the existing distributed photovoltaic energy storage power generation system based on micro-inverters.

[0026] Figure 3 This is a schematic diagram of the existing discrete independent photovoltaic-energy storage power supply application.

[0027] Figure 4 This is a schematic diagram of the overall topological structure of the modular micro-photovoltaic storage and power generation system of the present invention.

[0028] Figure 5 This is a schematic diagram of the circuit structure of a single functional module unit in the present invention (taking the energy storage battery module as an example). DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It will be understood that the drawings are only provided for reference and illustration purposes and are not intended to limit the present invention. The connection relationship shown in the drawings is only for the convenience of clear description and does not limit the connection method.

[0030] In the related art, see Figure 1-Figure 3 : Figure 1 The following diagram illustrates the structure of a traditional centralized solar-to-storage system. In this solution, the DC output from PV panels P is combined and processed centrally by a single inverter INV. The inverter integrates the PV boost circuit, the inverter grid-connected circuit, and the charge-discharge circuitry connected to the battery BAT. All functional units share a common controller and power supply unit. When PV power is sufficient and the grid permits, the inverter feeds energy into the grid and local AC loads. When sunlight is insufficient, the inverter draws power from the battery or purchases electricity from the grid to ensure output. Due to the high degree of integration of the entire system, if any module within the inverter fails (for example, a burnout of the inverter bridge), both the PV and battery systems will cease to function, resulting in a lack of redundancy. Furthermore, the system has a fixed capacity. Since the control and power units are already designed, users cannot expand capacity by adding PV panels or batteries; they can only replace the entire system with a higher power rating, which limits its flexibility.

[0031] Figure 2 The figure shows a schematic diagram of a photovoltaic-storage system using microinverters. Each PV module P is equipped with a microinverter uINV, which directly feeds its power into the AC bus (ACBus). Each module independently connects to the grid and generates electricity, thus avoiding the local shading issues of centralized MPPT systems and allowing for the gradual addition of PV units to expand scale. When adding energy storage, one approach is to use a standalone bidirectional energy storage inverter (PCS) connecting the battery (BAT) and the AC busbar, achieving charge and discharge regulation for the entire system through AC coupling. While this approach provides modularity on the PV side, the energy storage component remains centralized, requiring a higher-power PCS for capacity expansion. Furthermore, the AC / DC conversion process is complex, slightly impacting system efficiency. Another approach is to equip each PV-inverter unit with a small battery and DC booster, transforming it into an AC micromodule with energy storage. However, this significantly increases the cost and complexity of each microinverter and is not yet widely used in real-world home energy storage.

[0032] Figure 3The figure shows a single-panel off-grid power supply architecture, typically consisting of a solar panel, an MPPT controller, a battery, and a load. It is primarily used in outdoor low-power scenarios, such as surveillance cameras and lighting fixtures. This type of system is compact and flexible, with power typically ranging from a few watts to 500W, and battery capacity typically not exceeding 1kWh. However, its application is discrete and case-specific, lacking versatility and system integration.

[0033] In summary, mature solutions for photovoltaic systems currently exist within two power ranges: small-power off-grid systems below 300W, and string-type or distributed grid-connected systems above 10kW. However, for small and medium-sized solar power generation between 300W and 10kW, there is currently a lack of standardized system solutions that are highly integrated, modular, and flexible in deployment. This leads to the following problems: 1. If users require flexible deployment within this power range, they must customize system integration, increasing design and installation costs. 2. The existing system architecture lacks targeted optimization for this power range and cannot meet requirements such as on-grid / off-grid switching, optional energy storage, and strong scalability. 3. The system has low integration, complex on-site wiring, and inconvenient maintenance, which is not conducive to promotion and application by small and medium-sized users.

[0034] Therefore, there is an urgent need for a scalable, easy-to-deploy solar-storage power generation system architecture that supports multiple operating modes (grid-connected, off-grid, and hybrid) and covers the power range of 300W~10kW to address the shortcomings of existing technologies.

[0035] To this end, the purpose of the present invention is to provide a modular small and micro photovoltaic storage power generation system and method, which improves system reliability and flexibility through modular topology design and is particularly suitable for small photovoltaic storage applications in the power range of 300W~10kW.

[0036] like Figure 4~Figure 5 As shown, in an embodiment of the present invention, a modular micro-photovoltaic power generation system is provided, comprising a number of functional modules and a control unit that coordinates their operation. The modules are electrically connected in a "building block" manner via a common DC bus to form a complete power generation system. Preferably, the system includes: Photovoltaic power generation modules: These consist of photovoltaic panels and photovoltaic DC / DC converters. Each module is connected to the DC bus via its own DC / DC voltage converter, converting the DC power generated by the panels to the system bus voltage for output. Each module is equipped with an independent maximum power point tracking (MPPT) control unit that automatically adjusts output based on sunlight conditions, ensuring that each module operates at optimal power.

[0037] Energy storage battery modules: These modules consist of a rechargeable battery pack, a bidirectional DC / DC converter, and a battery management system (BMS). Each energy storage battery module is connected to the DC bus via its bidirectional DC / DC converter, enabling bidirectional energy exchange between the battery and the DC bus. When there is surplus photovoltaic energy, the energy storage battery module performs charging (stepping down the bus voltage for storage). When the load demand exceeds photovoltaic power generation or photovoltaic power generation is intermittent, the energy storage battery module quickly switches to discharge mode (boosting the voltage to feed battery energy into the bus), providing continuous and stable DC power to the system. Preferably, each energy storage battery module has a built-in BMS to monitor the battery cell status and an independent control circuit for charge and discharge management and protection.

[0038] Power conversion module: includes a bidirectional DC / AC converter and an on / off-grid switching unit. One end of the power conversion module is connected to the DC bus and the other end is connected to the AC bus. It is used to invert the DC bus power into AC power in the on-grid mode and feed it into the grid or supply AC loads, and to obtain power from the DC bus to form an independent AC output in the off-grid mode. The DC / AC converter supports bidirectional operation and can send excess energy to the grid when there is excess photovoltaic power, or rectify AC power into DC power to charge the battery when there is power in the grid and the battery needs to be charged. To ensure safety, the power conversion module is integrated with an island detection and switching circuit. When a power outage is detected, it automatically disconnects from the grid and switches to an off-grid power supply mode; it is synchronized to the grid after the grid is restored. According to application requirements, the system can be configured with one power conversion module to take on all AC outputs, or multiple modules can be connected in parallel to take on higher power or achieve three-phase power supply. Power sharing is ensured between modules through master-slave-free current sharing control.

[0039] The control unit monitors the operating status of each module and coordinates power distribution. This unit can be implemented as a standalone energy management module (EMS) or as a distributed controller embedded in each power module. The control unit connects to all photovoltaic power generation modules, energy storage battery modules, and power conversion modules via a wired or wireless communication network (e.g., bus communication). It collects real-time information such as voltage, current, and power from each module and sends control instructions to each module based on a preset strategy, thereby achieving energy management for the entire system. Control strategies include: prioritizing local load power consumption and using surplus photovoltaic power for battery charging and grid access in grid-connected mode; seamlessly switching to off-grid power supply in the event of a grid power outage; and, in off-grid mode, adjusting the battery charging and discharging sequence and load power supply sequence based on bus voltage and frequency stability requirements. Preferably, the present invention utilizes a control method that combines module autonomy with centralized coordination. Under normal circumstances, the control unit coordinates the operation of each module. In the event of a communication failure or loss of connection with a module, the remaining modules can autonomously adjust based on local variables such as bus voltage or frequency (e.g., the energy storage battery module automatically switches to charging or discharging based on bus voltage levels). This ensures that basic power supply functions are independent of a single control center, enhancing system robustness.

[0040] In summary, each module unit connects to the common DC bus and communication network via standard interfaces, enabling plug-and-play modular integration. Users can select a specific number of photovoltaic power generation modules and energy storage battery modules based on their actual power needs. When capacity expansion is needed, simply add the corresponding module and connect it to the system. The control unit will automatically identify the new module and incorporate it into coordinated control, eliminating the need to replace the entire system. This makes expansion simple and convenient. Similarly, if a module fails, it can be individually replaced while the remaining system maintains basic operation, improving system maintenance convenience and power supply continuity.

[0041] The present invention also provides a control method for the aforementioned photovoltaic power generation system, namely, a photovoltaic power generation method, to ensure efficient and coordinated operation of the modules. The method comprises the following steps: Module access initialization: When setting up or expanding the system, new photovoltaic power generation modules, energy storage battery modules, and power conversion modules are connected to the DC bus and control communication network through standard interfaces. After the control unit detects the new module, it assigns an address or identification code to it and reads its initial state parameters (such as voltage, power, etc.).

[0042] Grid-connected mode operation control: When the grid is normally connected, the control unit directs the power conversion module to operate in parallel with the grid, maintaining the DC bus voltage at the target value. Each photovoltaic power generation module outputs at its maximum power point. When the photovoltaic power exceeds the local load demand and the DC bus voltage rises to the upper threshold, the control unit coordinates the energy storage battery module to charge, and the remaining excess power is fed into the grid through the power conversion module. When insufficient photovoltaic power causes the bus voltage to drop to the lower threshold, the control unit notifies the energy storage battery module to quickly discharge to provide support. If necessary, electricity is purchased from the grid and rectified by the power conversion module to supplement the DC bus, maintaining bus voltage stability and continuous load power supply.

[0043] Off-grid Operation Control: When the grid is out of power or in an independent power supply scenario, the control unit switches the power conversion module to inverter output mode, establishing the local AC bus standard voltage and frequency. During this time, each PV module continues to output as much power as possible to supply the load and charge the battery. If the instantaneous PV power exceeds the load demand, the control unit raises the DC bus voltage limit or reduces the PV module output power (by offsetting the MPPT operating point) to reduce power generation. Conversely, when PV power is insufficient, the energy storage battery module automatically increases discharge power to support the bus voltage based on the preset bus voltage-power droop characteristic. This control allows multiple PV and energy storage battery modules to autonomously share the load in an off-grid state, maintaining a stable power supply. For multiple inverters connected in parallel, one inverter can be selected as the master reference source to maintain the AC frequency and voltage, while the remaining inverters follow synchronously using droop control, achieving balanced power supply without a master controller.

[0044] Mode switching and protection: The control unit continuously monitors the grid status. When it detects that the grid has returned to stability and the grid-connected conditions are met, the power conversion module is switched from off-grid to grid-connected operation according to the phase synchronization conditions, and the power distribution of each module is gradually adjusted to restore the grid-connected mode. If a grid fault is detected, the power conversion module is instructed to quickly disconnect from the grid within milliseconds of detection, and the energy storage battery module and photovoltaic power generation module are used to jointly maintain the DC bus and AC load power supply to avoid affecting personal and grid safety. The system is equipped with complete protection logic. For example, bus overvoltage, undervoltage, module overload, short circuit, etc. are all quickly responded to by the corresponding modules and control unit to ensure safe operation of the system.

[0045] Through the above method, the system of the present invention can automatically switch between grid-connected and off-grid modes according to real-time working conditions, and intelligently dispatch the power output / absorption of each module to achieve a dynamic balance among photovoltaic power generation, energy storage and electrical load.

[0046] Compared with the prior art, the topological architecture of the modular micro-photovoltaic power generation system of the present invention has the following advantages: Modularity improves reliability: The system consists of multiple independent functional modules, avoiding the single point of failure that can lead to systemic failure in traditional centralized solutions. For example, a failure in a battery storage module only reduces the corresponding storage capacity, while other modules continue to operate normally and provide power. If a photovoltaic power generation module experiences an anomaly, the battery and the grid compensate for the power shortfall without affecting load power supply. This modular, redundant design provides fault tolerance and significantly improves power supply reliability.

[0047] Plug and play, easy to expand: The present invention adopts a building block-style module combination method. Users can flexibly add or remove small power module units of 300W level to expand the system capacity according to their needs, thereby solving the problem of high cost in the background technology that the expansion of small and micro systems requires the purchase of additional whole machines. During the initial installation, only a small number of modules that meet the current load can be configured. When the load increases in the future, photovoltaic or energy storage battery modules can be gradually added. The system will automatically be compatible with the new modules without replacing the core equipment. This gradual investment model reduces the initial cost threshold and avoids the waste of idle equipment.

[0048] Smoothing out fluctuations and improving stability: By effectively integrating energy storage battery modules into photovoltaic power generation systems, the present invention achieves real-time smoothing of photovoltaic output fluctuations and energy adjustment. When changes in solar irradiation cause photovoltaic power fluctuations, the energy storage battery module is instantly charged and discharged for smoothing, ensuring the stability of the DC bus voltage, and thus ensuring the smooth and reliable AC output or grid-connected power. This power generation-energy storage synergy effectively solves the adverse effects of photovoltaic intermittency on the power grid and load, and improves power quality and system stability. At the same time, in off-grid scenarios, the addition of energy storage battery modules enables photovoltaics to continue to supply power to local loads when the grid is out of power, overcoming the defect of traditional photovoltaic power generation that "power generation stops as soon as the grid loses power" (improving solar energy utilization). Ensure that the basic power supply function does not rely on a single control center, and enhance system robustness.

[0049] Mode switching and energy self-adaptation capabilities: The system of the present invention can be connected to the grid or independently powered, and can automatically switch operating modes according to the state of the grid. Various technical features ensure seamless switching between grid-connected and off-grid modes and power autonomy between modules. When the grid is out of power, the system quickly switches to off-grid mode for power supply, and smoothly connects to the grid after the grid is restored, ensuring uninterrupted power supply and a safe and controllable conversion process. Each module collaboratively distributes the load based on a unified strategy or droop characteristics, so that "whichever module has spare capacity will supply more, and whichever module lacks will obtain it from others", realizing a swarm-like intelligent control capability, further enhancing the system's adaptability to complex application scenarios.

[0050] Easy Installation and Maintenance: This system utilizes standardized interfaces and a modular design. Each module is pre-commissioned at the factory, making on-site installation as simple as connecting building blocks. No specialized technicians are required to complete basic deployment. The system's highly intelligent control significantly reduces manual setup and maintenance workload. When a module requires repair or replacement, it can be hot-swapped and replaced without affecting other components. Compared to traditional solutions that require specialized personnel to disassemble the entire system, this system offers more convenient, safer, and cost-effective maintenance.

[0051] Figure 4The overall topology of the modular micro-scale photovoltaic power generation system of the present invention is presented. As shown in the figure, the system consists of multiple photovoltaic power generation modules, energy storage battery modules, and a set of power conversion modules interconnected via a common DC bus (DCBUS). Each photovoltaic power generation module includes a photovoltaic panel and a DC / DC booster. Multiple photovoltaic power generation modules are connected in parallel to the DCBUS to collect solar power. Each energy storage battery module includes a battery pack and a bidirectional DC / DC converter, also connected in parallel to the DCBUS, providing buffer energy from the DC side to the system. The voltage level of the DCBUS bus is maintained by the power conversion module, which connects to the AC bus (ACBUS) via an internal DC / AC inverter and further connects to the grid (GRID) and AC loads (LOAD). In grid-connected mode, the AC bus is connected to the public grid, and the power conversion module transfers power from the DC bus to the AC side. In off-grid mode, the power conversion module is disconnected from the grid and maintains the voltage and frequency of the local ACBUS. This embodiment also includes a system control unit, which communicates with each of the above modules via a signal bus (indicated by dashed lines in the figure). The control unit can be a standalone controller or integrated into a power conversion module as the master controller. It is responsible for monitoring bus voltage and current and the operating status of each module, coordinating the output of each module, and ensuring stable operation of the system under various operating conditions.

[0052] Figure 5 The internal structure of an energy storage battery module in the system of the present invention and its connection relationship with other components are schematically shown. Each energy storage battery module contains a battery pack BAT, whose positive and negative poles are connected to the DC bus DCBUS through a bidirectional DC / DC converter. The DC / DC converter is composed of power switch tubes Q1-Q4 to form a full-bridge circuit, a high-frequency transformer T to achieve electrical isolation and voltage conversion, and inductors, capacitors, etc. to form an input and output filter network. The controller MCU controls the PWM duty cycle of the bridge arm switch by detecting the battery voltage V_bat and the bus voltage V_bus to switch the energy flow between boost mode (discharge) and buck mode (charge). To ensure safety, each module is equipped with an independent management unit BMS to collect battery temperature, voltage and current parameters. When the battery is overcharged, over-discharged or overheated, it issues a protection instruction, and the MCU adjusts or stops the operation of the module accordingly.

[0053] Figure 5The figure also shows the interface of the photovoltaic power generation module. Its internal structure is similar to that of the energy storage battery module, but it only has a boost operating mode. The input is the photovoltaic array, and its control objective is to maintain the photovoltaic array voltage at the maximum power point. All modules communicate with the system control unit through their respective MCUs, reporting their status and receiving scheduling instructions. As mentioned earlier, even if communication is interrupted, each module still has basic autonomous functions. For example, the energy storage battery module can automatically decide whether to charge or discharge based on the detected bus voltage level. This can temporarily maintain DC bus stability in the event of a control unit failure, improving the system's fault tolerance.

[0054] The system operates as follows: During bright daylight hours, the photovoltaic modules continuously output energy, which is aggregated via the DCBUS and preferentially supplied to the inverter module to meet AC load and grid-connected requirements. When there is excess DC power but the batteries are not fully charged, the control unit instructs some of the energy storage modules to enter charging mode to store energy. In the evening or during rainy weather, when photovoltaic power drops, the control unit instructs the energy storage modules to sequentially switch to discharge mode to make up the difference. If necessary, the inverter module purchases power from the grid (grid-connected mode) to maintain a stable bus voltage. Late at night, when there is no photovoltaic input and the load is light, the system enters a standby energy-saving mode: most photovoltaic modules cease operation, while a small number of energy storage modules intermittently supply power to the bus or receive a basic power supply from the grid, while monitoring for signs of sunrise to restore photovoltaic power at any time. The following morning, when sunlight returns, the photovoltaic modules restart and take over primary power supply, and the cycle repeats. It is worth noting that when new photovoltaic or energy storage modules are added, the control unit automatically incorporates them into this coordinated control process. For example, when a new photovoltaic power generation module is connected, its MCU first performs a self-test and MPPT initialization, then detects the bus voltage and begins outputting power. The control unit monitors bus power changes and adjusts the battery charging strategy and inverter grid-connected power limit accordingly, ensuring efficient use of the new module's power without causing bus overvoltage. Similarly, when a module is removed, the system can also adaptively adjust to ensure overall stable operation.

[0055] The modular micro-scale photovoltaic power generation system of the present invention is fully illustrated through the above-described embodiments. With its modular structure and intelligent control, this system can be widely applied in scenarios such as household photovoltaic storage systems, small off-grid power supply systems, portable emergency power supplies, and backup power supplies for communication base stations. Without departing from the spirit of the present invention, those skilled in the art may also make various modifications and adjustments to the specific implementation, such as changing the power level of individual modules, adopting different communication protocols or control algorithms, etc., without affecting the functional essence of the present invention.

[0056] In summary, the present invention realizes a small and micro photovoltaic energy storage power generation system that is highly reliable, easy to expand, has stable power supply, and is easy to use through a unique building block modular topology and control method. It can effectively solve the shortcomings of photovoltaic energy storage power generation applications in the power range of 300W~10kW proposed in the background technology, and has significant practical value and promotion significance.

[0057] Finally, it should be noted that those skilled in the art can cross-reference or superimpose the various embodiments of this solution, which still falls within the original disclosure scope of this solution. In addition, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A modular micro-photovoltaic power generation system, characterized by: include: At least one photovoltaic power generation module, each converting solar energy through MPPT and then connecting it to the public DC bus; at least one energy storage battery module, configured to absorb electrical energy from the DC bus in a charging state and to provide electrical energy to the DC bus in a discharging state; At least one power conversion module, one side of which is connected to the DC bus and the other side of which is connected to the AC bus and can be electrically connected to the power grid or AC load, and is used to switch between grid-connected mode and off-grid mode to perform DC-AC bidirectional energy conversion or unidirectional energy conversion; A control unit is used to monitor the voltage and current of the DC bus and the AC bus, as well as the operating status of the photovoltaic power generation module, the energy storage battery module and the power conversion module, and coordinate the operating mode and power distribution of the photovoltaic power generation module, the energy storage battery module and the power conversion module according to a preset strategy.

2. The modular micro-photovoltaic power generation system according to claim 1, characterized in that: A slot-type MPPT module chassis is provided, and the front panel of the chassis is arranged with several blind-insertion slots, each of which is provided with power contacts, CAN communication contacts and SYNC synchronization contacts in sequence; Each photovoltaic power generation module is equipped with a pluggable MPPT control board. The DC output terminal, communication terminal and synchronization terminal of the MPPT control board are electrically connected to the corresponding contacts in the slot through a blind-plug connector, and are electrically connected to the photovoltaic power generation module and connected in parallel to the DC bus.

3. The modular micro-photovoltaic power generation system according to claim 2, characterized in that: Positive and negative copper bars are arranged side by side inside the slot-type MPPT module chassis to form the DC bus; The MPPT control board includes a master MPPT board and a slave board. The blind-plug slots are arranged in parallel with the CAN communication bus and the SYNC synchronization bus, wherein the SYNC synchronization bus is connected to the synchronization port of each MPPT control board, and is sent by the master MPPT board and received by the slave board, and is used to transmit synchronization pulses to achieve multi-board phase synchronization; the CAN communication bus connects each MPPT control board and the control unit, and is used to broadcast reference parameters and complete master-slave role determination.

4. The modular micro-photovoltaic power generation system according to claim 1, characterized in that: Each energy storage battery module includes a battery pack, a bidirectional DC / DC converter and a battery management system (BMS); The positive and negative electrodes of the battery pack are directly connected in parallel to the DC busbar via a quick-swap DC connector; The battery management system is electrically connected to the CAN communication bus via an isolated CAN transceiver to collect and report battery voltage, temperature and state of charge.

5. The modular micro-photovoltaic power generation system according to claim 3, characterized in that: The MPPT control board is used to adopt the exit designated transfer mode or the remaining working modules adopt the adjacent principle setting mode with the original master MPPT board when the master MPPT board fails or exits, and take over the rights of the master MPPT board. At this time, the new master MPPT board automatically changes the passive receiving SYNC signal mode to the active sending SYNC mode, and the working modes of the other slave boards remain unchanged; at the same time, each time the photovoltaic power generation module is restarted, the first MPPT control board started automatically becomes the master MPPT board.

6. The modular micro-photovoltaic power generation system according to claim 1, characterized in that: The power conversion module is equipped with an on-grid / off-grid switching unit, which is composed of a grid-connected relay, a bypass contactor and a drive control circuit. When it is detected that the voltage or frequency of the AC bus deviates from the rated range, the drive control circuit disconnects the grid-connected relay and closes the bypass contactor within a predetermined time, causing the power conversion module to switch to an off-grid inverter mode.

7. The modular micro-photovoltaic power generation system according to claim 6, characterized in that: When at least two power conversion modules are connected in parallel to the same AC bus, each power conversion module performs masterless synchronization according to a uniformly set voltage-frequency droop coefficient; if any of the power conversion modules fails and exits operation, the remaining power conversion modules automatically increase their output power according to the droop coefficient to maintain the voltage and frequency stability of the AC bus.

8. A photovoltaic power generation method, characterized in that: The following steps are involved: Module access and identification steps: connect the photovoltaic power generation module, energy storage battery module and power conversion module in parallel to the DC bus through the standard interface and establish communication with the control unit; Grid-connected operation steps: When the grid is normal, the control unit synchronizes the power conversion module with the grid, maintains the DC bus voltage within the target range, and dispatches the output power of the photovoltaic power generation module and the charging power of the energy storage battery module in real time based on the DC bus voltage; Off-grid operation steps: When the grid loses power or is in an independent power supply scenario, the control unit drives the on-grid / off-grid switching unit to disconnect the power conversion module from the grid and maintain local AC output. Each energy storage battery module discharges or stands by according to the droop characteristics to balance the DC bus power; Mode switching step: When it is detected that the grid is restored and the synchronization conditions are met, the control unit first synchronizes the AC bus to the grid, and then closes the on / off-grid switching unit to allow the power conversion module to smoothly restore grid connection and re-execute the grid connection operation step.

9. The photovoltaic power generation method according to claim 8, characterized in that: In the grid-connected operation step, when the DC bus voltage is higher than the upper threshold, the control unit instructs the energy storage battery module to enter a constant voltage charging mode; when the DC bus voltage is lower than the lower threshold and the grid is available, the control unit instructs the power conversion module to take power for boost compensation; otherwise, the control unit instructs the energy storage battery module to increase discharge power according to a droop curve; During the off-grid operation step, the control unit selects a power conversion module as the main inverter source to output the reference voltage and frequency. The remaining power conversion modules use voltage-frequency droop control to adjust their respective output powers according to the monitored deviation to realize a masterless synchronous parallel system.

10. The photovoltaic power generation method according to claim 8, characterized in that: During off-grid operation, when the power of the energy storage battery module reaches the upper limit and the load power is less than the output power of the photovoltaic power generation module, the control unit limits the photovoltaic power by offsetting the MPPT target voltage of the photovoltaic power generation module to prevent the DC bus voltage from being too high; Before the grid-connected switching in the mode switching step, the control unit gradually adjusts the active and reactive outputs of each power conversion module at a current limiting rate of 10% / s, and smoothly restores the grid-connected operation after the grid-connected relay is closed.

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