Integrated grid-connected system of photovoltaic and energy storage facing grid interaction and control method thereof

Abstract

This invention provides a pure grid-connected integrated photovoltaic-storage grid-connected system. This system eliminates static transfer switches and off-grid related control logic, and consists of a photovoltaic DC input port, an internal DC bus, an integrated power conversion and management system, a battery interface, and a grid-connected system controller. The integrated power conversion and management system includes only an MPPT (Maximum Power Point Tracking) module, a bidirectional DC / DC module, and a bidirectional three-phase grid-connected inverter module, used to achieve photovoltaic maximum power point tracking and battery charge / discharge management, and AC / DC bidirectional energy conversion, respectively. The grid-connected system controller is dedicated to executing collaborative optimization control strategies in pure grid-connected mode. Simultaneously, this invention proposes a control method adapted to this system, ensuring that the system always operates in grid-connected mode, encompassing four modes: photovoltaic priority self-consumption, planned energy storage scheduling, dynamic grid support, and joint optimization operation, thereby achieving optimal power flow allocation between photovoltaic, energy storage, and the grid.

Description

Technical Field

[0001] This application relates to the field of new energy grid-connected power generation and energy storage technology, and in particular to an integrated photovoltaic-storage grid-connected system and its control method for grid interaction. Background Technology

[0002] Driven by the "dual carbon" goals, the volatility generated by high-proportion distributed photovoltaic (PV) grid connection poses challenges to the stable operation of the distribution network. Traditional separate PV inverter and power storage converter (PCS) solutions suffer from problems such as complex coordination and control, slow dynamic response, and limited grid support. Meanwhile, existing DC-coupled PV-storage systems are often designed with off-grid or backup power functions in mind. The built-in static transfer switch (STS) and related control logic add unnecessary cost and complexity. For purely grid-connected applications, these functions are not essential and may even reduce the system's grid performance and economic efficiency.

[0003] For example, existing publicly available DC-coupled photovoltaic-storage systems with off-grid capability require control strategies that consider both grid-connected and off-grid modes. In pure grid-connected operation, the algorithm fails to achieve optimal performance, and hardware costs include redundancy due to off-grid functionality. Therefore, for scenarios that do not require off-grid backup power and focus on improving grid-connected economics and grid interaction capabilities, there is an urgent need for a more streamlined, efficient, high-power-density, and deeply grid-service-oriented integrated solution. Summary of the Invention

[0004] Therefore, it is necessary to provide an integrated photovoltaic-storage grid-connected system and its control method that can interact with the power grid, addressing the aforementioned technical problems.

[0005] An integrated photovoltaic-storage grid-connected system for grid interaction includes: a photovoltaic DC input port; an internal DC bus; an integrated power conversion and management system consisting of an MPPT, bidirectional DC / DC modules, and a bidirectional three-phase grid-connected inverter module; a battery interface; and a grid-connected system controller. The MPPT and bidirectional DC / DC module are connected between the photovoltaic DC input port and the internal DC bus to achieve photovoltaic maximum power point tracking and battery charge and discharge management. The bidirectional three-phase grid-connected inverter module is connected to the internal DC bus and the AC grid to realize bidirectional energy conversion between DC and AC grids; The grid-connected system controller is communicatively connected to the MPPT, the bidirectional DC / DC module, and the bidirectional three-phase grid-connected inverter module, and is used to execute a collaborative optimization control strategy in pure grid-connected mode.

[0006] In one alternative embodiment, the system does not include a static transfer switch (STS) for load switching between the AC grid and the inverter.

[0007] In one optional embodiment, the bidirectional three-phase grid-connected inverter module includes a high-precision phase-locked loop for rapid synchronization with the AC grid, and features programmable power factor regulation and low / high voltage ride-through capabilities.

[0008] In one optional embodiment, the bidirectional three-phase grid-connected inverter module is a high-performance topology structure used to invert the electrical energy on the DC bus into three-phase AC power synchronized with the AC grid, and simultaneously absorb AC power from the AC grid and rectify it into DC power to charge the battery or supplement the DC bus.

[0009] In one alternative embodiment, the MPPT and bidirectional DC / DC module employ a coupled inductor or multiphase interleaved parallel topology.

[0010] In one alternative embodiment, the internal DC bus is connected to the battery system via a battery interface and is controlled by the MPPT and bidirectional DC / DC module.

[0011] A control method is provided for any of the integrated photovoltaic-storage grid-connected systems oriented towards grid interaction in the embodiments of this application, characterized in that the system always operates in grid-connected mode, and the method includes: If the system is in a photovoltaic priority self-consumption mode, the photovoltaic power is transmitted to the DC bus through the MPPT and bidirectional DC / DC module; The bidirectional three-phase grid-connected inverter module converts the power into AC power to supply the local grid-connected load, and the surplus or insufficient power is automatically balanced by the AC grid.

[0012] In one optional embodiment, the method further includes: if the system is in a planned energy storage scheduling mode, the grid-connected system controller plans the battery charging and discharging schedule according to the electricity price signal or grid dispatching instruction; during the charging period, the surplus energy of the AC grid or photovoltaic is controlled to charge the battery through the corresponding path; during the discharging period, the battery energy is controlled to be fed into the AC grid or used locally through the bidirectional three-phase grid-connected inverter module.

[0013] In one optional embodiment, the method further includes: if the system is in dynamic grid support mode, monitoring the grid status in real time; when the frequency of the AC grid fluctuates, automatically adjusting the output active power of the bidirectional three-phase grid-connected inverter module to respond to the frequency; and when the voltage of the AC grid is abnormal, automatically adjusting the reactive power output to support the voltage.

[0014] In one optional embodiment, the method further includes: if the system is in a joint optimization operation mode, real-time collaborative optimization of the MPPT operating point, battery charging and discharging power and inverter grid-connected power, and optimization of the power flow distribution among photovoltaic, energy storage and grid, with the goal of optimizing system economy or grid support.

[0015] This invention addresses the problems of complex coordination and slow dynamic response inherent in traditional discrete photovoltaic inverter and energy storage converter schemes, as well as the shortcomings of existing DC-coupled photovoltaic-energy storage systems, such as hardware redundancy, high cost, and poor grid-connected performance due to their off-grid functionality. It designs a purely grid-connected integrated photovoltaic-energy storage grid-connected system. This system eliminates static transfer switches and off-grid related control logic, and consists of a photovoltaic DC input port, an internal DC bus, an integrated power conversion and management system, a battery interface, and a grid-connected system controller. The integrated power conversion and management system includes only an MPPT, a bidirectional DC / DC module, and a bidirectional three-phase grid-connected inverter module. These modules are used to achieve photovoltaic maximum power point tracking and battery charge / discharge management, and AC / DC bidirectional energy conversion, respectively. The grid-connected system controller is dedicated to executing collaborative optimization control strategies in pure grid-connected mode. Furthermore, this invention proposes a control method adapted to this system. This method ensures that the system always maintains grid-connected operation and covers four modes: photovoltaic priority self-consumption, planned energy storage scheduling, dynamic grid support, and joint optimization operation, achieving optimal power flow allocation between photovoltaic, energy storage, and the grid. This invention significantly simplifies the system hardware structure and control logic, effectively improves the system power density and energy conversion efficiency, strengthens the grid interaction service capabilities, and can deeply participate in grid frequency regulation, voltage regulation, peak shaving and valley filling and other auxiliary services. It reduces manufacturing costs, eliminates potential faults when switching between grid-connected and off-grid modes, and improves the reliability of system operation. It has broad industrial applicability and commercial application prospects in pure grid-connected application scenarios such as large industrial and commercial parks and centralized photovoltaic power stations with supporting energy storage. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a system topology diagram of an integrated photovoltaic-storage grid-connected system for grid interaction in one embodiment; Figure 2 This is a flowchart illustrating the steps of a photovoltaic priority self-consumption mode method in a joint optimization operation mode, as shown in one embodiment of the control method. Figure 3This is a flowchart illustrating the steps of a planned energy storage scheduling mode in a joint optimization operation mode, as shown in one embodiment of the control method. Figure 4 This is a flowchart illustrating the steps of a control method in a joint optimization operation mode for a dynamic power grid support mode, as shown in one embodiment. Figure 5 This is a flowchart illustrating the steps of the control method in another embodiment when jointly optimizing the operating mode. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following will provide a more detailed description of this application in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0019] See Figure 1 This embodiment is a specific implementation scheme of an integrated photovoltaic-storage grid-connected system for grid interaction, which can be applied to a 64kWh distributed photovoltaic-storage project and is suitable for pure grid-connected power generation and energy storage application scenarios in large industrial and commercial parks. The system is designed for pure grid connection, without off-grid power supply function and static transfer switch (STS). The components, connections, and functions strictly correspond to the aforementioned independent claims, as detailed below: Photovoltaic DC input port: As the photovoltaic power input unit of the system, this port is directly connected to 22 series-connected monocrystalline silicon photovoltaic arrays. It is used to receive the high-voltage DC power generated by the photovoltaic arrays and transmit it to the subsequent power conversion module. It is the only DC input channel for photovoltaic power to enter the system.

[0020] Internal DC bus: As the only DC power collection and distribution bus in the system, its DC voltage is stably controlled at 750Vdc in this embodiment. It receives the power converted from the photovoltaic DC input port, the charging and discharging power of the battery system, and provides a stable DC power input to the grid-connected inverter module, realizing the interconnection of power among the DC side units in the system.

[0021] Integrated Power Conversion and Management System: This system is strictly composed of two power modules: an MPPT and a bidirectional DC / DC module, and a bidirectional three-phase grid-connected inverter module. These are the core power conversion units of the system, and their specific implementation is as follows: MPPT and bidirectional DC / DC module: This module is directly connected between the photovoltaic DC input port and the internal DC bus. It can adopt a multi-phase interleaved parallel structure with a bidirectional Buck-Boost circuit topology. On the one hand, it integrates an advanced MPPT algorithm, which can track the maximum power point of the photovoltaic array in real time and efficiently convert the high-voltage DC power from the photovoltaic DC input port to the internal DC bus, thus completing the photovoltaic maximum power point tracking function. On the other hand, as the execution unit of the battery management system, it has bidirectional buck-boost function, accurately controls the bidirectional energy flow between the internal DC bus and the battery system, and completes the full-process management of battery charging and discharging, including constant current and constant voltage.

[0022] Bidirectional three-phase grid-connected inverter module: This module is directly connected to the internal DC bus and the 380V three-phase AC grid. It adopts a T-type three-level topology and is equipped with an LCL filter. It can invert the DC power on the internal DC bus into three-phase AC power synchronized with the grid and feed it into the AC grid. At the same time, it can also absorb AC power from the AC grid, rectify it into DC power, and supplement the internal DC bus or charge the battery system. It realizes bidirectional energy conversion between DC and AC grids, and the grid-connected current harmonics meet the national standards.

[0023] Battery Interface: As the connection unit between the system and the energy storage battery, this interface can directly connect the lithium battery pack to the internal DC bus. The charging and discharging process of the battery is precisely controlled by the MPPT and bidirectional DC / DC module mentioned above, realizing the power interaction between the battery system and the internal DC bus, and adapting to the energy storage capacity requirements of a 64kWh distributed photovoltaic energy storage project.

[0024] Grid-connected system controller: This controller, based on a high-performance microprocessor, establishes real-time communication connections with the MPPT, bidirectional DC / DC modules, and bidirectional three-phase grid-connected inverter modules. Its core function is to execute collaborative optimization control strategies in pure grid-connected mode, without any off-grid power supply or seamless switching logic between grid and off-grid. Based on real-time data such as grid status, photovoltaic output, and electricity price signals, the controller collaboratively adjusts the photovoltaic maximum power point tracking operating point of the MPPT and bidirectional DC / DC modules, the battery charging and discharging power, and the grid-connected power of the bidirectional three-phase grid-connected inverter modules to achieve optimal power flow distribution among photovoltaic, energy storage, and grid components. Simultaneously, it can respond to grid frequency and voltage regulation commands, completing grid support and economic optimization control in pure grid-connected mode.

[0025] The integrated photovoltaic-storage grid-connected system of this embodiment fully realizes the functions of all the technical features in the independent claims through the coordinated work of the above-mentioned units. The system has high power density and simple control logic, which can effectively improve the self-consumption rate of photovoltaic power generation, provide auxiliary services such as frequency regulation and voltage regulation for AC power grid, and adapt to the grid interaction needs of pure grid-connected scenarios.

[0026] In one optional embodiment, the AC output of the bidirectional three-phase grid-connected inverter module does not have any static transfer switch (STS), nor is it configured with any load switching hardware components and supporting control circuits related to off-grid power supply. The inverter output is directly hard-connected to the grid access point through a standard grid-connected switch (an AC power distribution unit consisting of a circuit breaker, contactor, and surge protector), becoming the sole AC channel for photovoltaic and battery energy to feed into the grid and for grid energy to supplement the system. By eliminating the STS and related redundant components, the system thoroughly simplifies the hardware structure, eliminates potential fault points during grid-connected / off-grid mode switching, and reduces hardware costs and control logic complexity caused by the STS, fully adapting to the usage requirements of pure grid-connected scenarios.

[0027] In one optional embodiment, the control unit of the bidirectional three-phase grid-connected inverter module integrates a high-precision composite phase-locked loop (PLL), employing a collaborative scheme of "high-speed hardware sampling + software anti-distortion PLL." This enables rapid synchronization with the grid under conditions of grid voltage harmonic distortion, three-phase voltage imbalance, and small frequency fluctuations, with a synchronization response time ≤50ms and a synchronization phase error ≤±0.5°, meeting the grid's synchronization accuracy requirements for grid-connected equipment. The inverter module also features programmable power factor continuous adjustment, allowing stepless adjustment within the range of 0.8 leading to 0.8 lagging. The grid-connected system controller can adjust the power factor according to grid dispatch. Based on the reactive power demand or reactive power characteristics of the local load, the inverter module automatically adjusts the power factor by issuing commands to achieve local reactive power compensation or grid reactive power support. Simultaneously, the inverter module has built-in low-voltage ride-through (LVRT) and high-voltage ride-through (HVRT) functions, fully complying with the latest grid operation regulations: when the grid voltage drops to 20% of the rated voltage, the module can maintain grid-connected operation for ≥0.15s; when the grid voltage rises to 130% of the rated voltage, the module can stably connect to the grid without disconnection; after the grid voltage recovers to the rated range, it can quickly restore active / reactive power output, achieving continuous support during grid fault periods.

[0028] In one optional embodiment, the bidirectional three-phase grid-connected inverter module can consider adopting a T-type three-level high-performance topology, combined with an LCL passive filter to form a power conversion unit. Compared with the traditional two-level topology, this topology has the advantages of low switching losses, low output voltage harmonics, and high power density. In inverter mode, the module inverts the 750Vdc DC power from the internal DC bus into sinusoidal AC power with the same frequency, phase, and amplitude as the 380V three-phase AC grid. After filtering by the LCL filter, the total harmonic distortion rate of the grid-connected current is ≤3%, which meets the requirements. The national standard requires harmonic control of the grid-connected current to achieve efficient feeding of photovoltaic and battery energy to the grid. In rectification mode, the module can rectify the 380V three-phase AC power from the grid side into a stable 750Vdc DC power, which can be directly supplied to the internal DC bus or charged to the battery pack through MPPT and bidirectional DC / DC modules. For example, during off-peak hours when the grid electricity price is low, the inverter module operates in rectification mode, converting grid power into DC power, which is then regulated by the DC / DC module to charge the lithium battery pack with constant current and constant voltage, realizing the storage and utilization of grid energy.

[0029] In one optional embodiment, the MPPT and bidirectional DC / DC module adopt a bidirectional Buck-Boost topology with two-phase interleaved parallel connection and integrates a coupling inductor as an energy storage element. This design combines the technical advantages of multiphase interleaved parallel connection and coupling inductor: on the one hand, the two-phase interleaved parallel connection cancels out the input and output current ripple of the module, with a current ripple coefficient ≤5%, which significantly reduces the capacity requirement of the filter capacitor and improves the power density of the module; on the other hand, the coupling inductor effectively reduces the inductor volume and core loss, enabling the module to achieve a maximum conversion efficiency ≥98.5%; at the same time, this topology allows the module to have a wide range of bidirectional buck-boost capabilities, which can adapt to the input voltage fluctuations of the photovoltaic array (300Vdc~800Vdc) and the charging and discharging voltage range of the battery pack, and the response speed to the dynamic changes of photovoltaic input power is ≤100ms, which can quickly track the maximum power point of the photovoltaic and accurately control the charging and discharging power of the battery, meeting the system's requirements for high efficiency and accuracy in power conversion.

[0030] In one optional embodiment, the system features a standardized high-voltage battery interface that integrates voltage, current, and temperature sampling units, as well as reverse connection and overcurrent protection circuits. The lithium battery pack is directly connected to the internal 750Vdc DC bus via this interface, providing a unique channel for power exchange between the battery system and the DC bus. All charging and discharging processes of the battery system are fully controlled by the MPPT and bidirectional DC / DC modules as execution units of the battery management system (BMS). The grid-connected system controller receives battery status information (SOC, individual cell voltage, battery temperature, cycle time) uploaded by the BMS. The module (MPPT) and bidirectional DC / DC module are notified of the number of charging cycles. The module adjusts its working mode and power parameters according to the instructions. During charging, the 750Vdc of the DC bus is converted to the rated charging voltage of the battery pack to achieve constant current / constant voltage / float charging in a stepped manner. During discharging, the DC power of the battery pack is boosted to 750Vdc to supplement the DC bus. When the battery SOC is below 20% (undervoltage), above 80% (overvoltage), or the temperature exceeds the rated range of 0℃~55℃, the module will automatically cut off the battery charging and discharging circuit to achieve safety protection of the battery system.

[0031] In one optional embodiment, a control method is provided for controlling the integrated photovoltaic-storage grid-connected system with grid interaction described in the above embodiments, wherein the system always operates in grid-connected mode. The system achieves different control modes through four modes: photovoltaic-priority self-consumption mode, planned energy storage dispatch mode, dynamic grid support mode, and joint optimized operation mode.

[0032] When the system is in photovoltaic-priority self-consumption mode, the high-voltage direct current generated by the photovoltaic array is transmitted to the MPPT and bidirectional DC / DC module via the photovoltaic DC input port and then delivered to the DC bus. It is then converted into AC power by the bidirectional three-phase grid-connected inverter module to supply local grid-connected loads, and any surplus or insufficient power is automatically balanced by the AC grid. Specifically, this includes: STEP11: The MPPT and bidirectional DC / DC modules use a composite MPPT algorithm of perturbation observation method + conductance increment method to track the maximum power point of the photovoltaic array in real time, and efficiently convert photovoltaic power into electricity and deliver it to the internal 750Vdc DC bus. STEP12: The grid-connected system controller collects the power demand of local grid-connected loads (production equipment, lighting, office power, etc. in industrial and commercial parks) in real time, and controls the bidirectional three-phase grid-connected inverter module to convert the power on the DC bus into 380V three-phase AC power, which is given priority to supply to local grid-connected loads to realize the self-generation and self-consumption of photovoltaic power. STEP13: When the photovoltaic output exceeds the local load power demand, the surplus photovoltaic power is directly fed into the AC grid through the inverter module and absorbed by the grid; when the photovoltaic output is less than the local load power demand, the insufficient power is supplemented by the AC grid in real time. The entire power balance process is automatically closed-loop regulated by the grid-connected system controller by detecting the DC bus voltage and the inverter output power, without the need for manual intervention.

[0033] When the system is in planned energy storage dispatch mode, the grid-connected system controller plans the battery charging and discharging schedule based on electricity price signals or grid dispatch instructions. During the charging period, it controls surplus energy from the AC grid or photovoltaic system to charge the battery through appropriate paths. During the discharging period, it controls the battery energy to be fed into the AC grid or supplied locally through the bidirectional three-phase grid-connected inverter module. Specifically, this includes: STEP21: The grid-connected system controller has a built-in real-time electricity price acquisition module and a grid dispatch instruction receiving unit. It can automatically acquire grid peak-valley-flat electricity price signals, electricity market transaction instructions and grid peak-shaving dispatch instructions. Based on the above information and combined with photovoltaic power output forecast and local load power forecast data, it can automatically plan the charging and discharging schedule of the lithium battery pack (including charging / discharging period, rated power and target SOC). STEP22: Charging periods (e.g., off-peak electricity prices from 23:00 to 7:00, or midday when photovoltaic output is much greater than local load): If there is surplus photovoltaic energy, the controller controls the surplus photovoltaic power to directly charge the battery through the MPPT and bidirectional DC / DC module; if there is no surplus photovoltaic energy or it is during a period of no sunlight, the controller controls the inverter module to work in rectification mode, converting grid power into DC power, which is then used to charge the battery through the DC / DC module. During the charging process, the module dynamically adjusts the charging power according to BMS information to avoid overcharging the battery; STEP23: Discharge period (e.g., peak electricity price periods 10:00-14:00 / 18:00-22:00, when the grid issues a peak-shaving discharge command): The controller controls the battery pack to boost the voltage to 750Vdc through the MPPT and bidirectional DC / DC module, and delivers the battery energy to the DC bus. Then, the inverter module inverts it into AC power, which is preferentially supplied to local grid-connected loads to reduce the purchase of electricity from the grid. If the local load has no power demand, the battery energy is directly fed into the AC grid to achieve peak shaving and valley filling or to respond to the grid's peak-shaving command, thereby improving the economic efficiency of system operation.

[0034] When the system is in dynamic grid support mode, it monitors the grid status in real time. When the AC grid frequency fluctuates, it automatically adjusts the active power output of the bidirectional three-phase grid-connected inverter module to respond to the frequency fluctuation; when the AC grid voltage is abnormal, it automatically adjusts the reactive power output to support the voltage. Specific steps include: STEP31: The grid-connected system controller collects the three-phase voltage, frequency, phase, active / reactive power and other status parameters of the AC grid in real time at a sampling frequency of 1kHz through the grid measurement and control unit, so as to realize the monitoring of the grid status without blind spots. STEP32: Grid Frequency Response: When the grid frequency deviates from the rated value of 50Hz (e.g., rising to 50.2Hz or falling to 49.8Hz), the controller sends an active power regulation command to the bidirectional three-phase grid-connected inverter module within 200ms: When the frequency is too high, the inverter's active power output is reduced (or the battery discharge is paused and the battery charging power is increased) to reduce the active power input to the grid; when the frequency is too low, the inverter's active power output is increased (or the battery discharge is started) to supplement the grid with active power, thereby achieving primary grid frequency regulation. STEP33: Grid Voltage Support: When abnormal situations such as grid voltage drops, voltage surges, or three-phase voltage imbalance occur, the controller automatically adjusts the reactive power output of the inverter module: When the grid voltage drops, the inverter injects capacitive reactive power into the grid to quickly raise the grid voltage; when the grid voltage surges, the inverter injects inductive reactive power into the grid to suppress the voltage from rising further; when the three-phase voltage is unbalanced, the inverter performs phase-by-phase reactive power compensation to make the three-phase voltage of the grid tend to be balanced. The entire voltage support process does not require grid dispatch instructions and is completed autonomously by the controller in a closed loop.

[0035] When the system is in joint optimization operation mode, it coordinates and optimizes the MPPT operating point, battery charging and discharging power, and inverter grid-connected power in real time to optimize the power flow distribution among photovoltaic, energy storage, and grid, aiming to achieve system economy or grid support optimization. This mode can have either maximizing system economy or optimizing grid support as dual objectives, achieving optimal power flow distribution among photovoltaic, energy storage, and grid. The specific execution steps are as follows: STEP41: Target Selection: Users or grid dispatchers can set optimization targets through the system's host computer. The two can be switched in real time according to grid demand (e.g., during peak grid periods, priority is given to grid support optimization, and during flat grid periods, priority is given to maximizing system economy). STEP42: Data Acquisition and Prediction: The controller collects real-time data such as actual photovoltaic output, actual local load power, grid status parameters, and battery SOC. At the same time, it calls up data such as short-term photovoltaic output prediction, local load power prediction, and electricity price trend prediction to provide a basis for optimization calculation. STEP43: Multi-parameter Cooperative Optimization: The controller uses a preset multi-objective optimization algorithm with a calculation cycle of 200ms to optimize three core parameters in real time: ① Optimize the MPPT and MPPT operating point of the bidirectional DC / DC module to balance maximizing photovoltaic output and battery charging efficiency; ② Optimize battery charging and discharging power to determine the power threshold and rate of battery charging / discharging; ③ Optimize the grid-connected active / reactive power of the bidirectional three-phase grid-connected inverter module to control the power fed into / purchased from the grid. STEP44: Goal Implementation: If maximizing system economy is chosen: The controller focuses on reducing electricity costs in industrial and commercial parks, optimizing power flow distribution to maximize photovoltaic self-consumption rate, maximize grid-purchased charging during off-peak hours, and maximize battery discharge power supply during peak hours, while reducing the proportion of grid-purchased electricity during peak hours; If grid support optimization is chosen: The controller focuses on grid frequency and voltage stability, appropriately reducing the priority of photovoltaic MPPT power point tracking, prioritizing the inverter's reactive power support and active power frequency regulation response speed, and dynamically adjusting battery charging and discharging response strategies to achieve deep grid support and improve the grid friendliness of distributed energy.

[0036] The solutions described above enable the integrated photovoltaic-storage grid-connected system to achieve the technical goals of simplified hardware structure, high-efficiency power conversion, intelligent control logic, and deep optimization of grid interaction. The system eliminates redundant components and control logic related to off-grid applications, focusing on the usage requirements of pure grid-connected scenarios. While reducing manufacturing costs and operational complexity, it significantly improves the system's power density, operational reliability, and economy. It can effectively increase the self-consumption rate of photovoltaic power generation, reduce electricity costs in industrial and commercial parks, and provide auxiliary services such as frequency regulation, voltage regulation, and peak shaving and valley filling for the grid. It has broad industrial applicability and commercial application prospects in pure grid-connected scenarios such as large industrial and commercial parks and centralized photovoltaic power stations with energy storage.

[0037] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by computer program instructions and related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can cover the processes of the above method embodiments. Any references to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. It should be noted that RAM takes many forms, such as Static Random Access Memory (SRAM) and Dynamic Random Access Memory (DRAM). The databases involved in the embodiments of this application cover at least one of relational and non-relational databases. Non-relational databases include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application can be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these. With the rapid development of technology, especially the advancements in quantum computing and AI technologies, it is expected that by 2025, these processors will achieve higher levels of performance and applications, thereby fundamentally changing the way we live and work.

[0038] The technical features in the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of technical features are described. However, as long as these combinations do not contradict each other, they should all be considered within the scope of this application.

[0039] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and such modifications and improvements are all within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. An integrated photovoltaic-storage grid-connected system for grid interaction, characterized in that it comprises: a photovoltaic DC input port; an internal DC bus; an integrated power conversion and management system consisting of an MPPT, bidirectional DC / DC modules, and a bidirectional three-phase grid-connected inverter module; a battery interface; and a grid-connected system controller, wherein... The MPPT and bidirectional DC / DC module are connected between the photovoltaic DC input port and the internal DC bus to achieve photovoltaic maximum power point tracking and battery charge and discharge management. The bidirectional three-phase grid-connected inverter module is connected to the internal DC bus and the AC grid to realize bidirectional energy conversion between DC and AC grids; The grid-connected system controller is communicatively connected to the MPPT, the bidirectional DC / DC module, and the bidirectional three-phase grid-connected inverter module, and is used to execute a collaborative optimization control strategy in pure grid-connected mode.

2. The integrated photovoltaic-storage grid-connected system for grid interaction as described in claim 1, characterized in that, The system does not include a static transfer switch (STS) for load switching between the AC grid and the inverter.

3. The integrated photovoltaic-storage grid-connected system for grid interaction as described in claim 1, characterized in that, The bidirectional three-phase grid-connected inverter module includes a high-precision phase-locked loop for rapid synchronization with the AC grid, and features programmable power factor regulation and low / high voltage ride-through capabilities.

4. The integrated photovoltaic-storage grid-connected system for grid interaction according to claim 1, characterized in that, The bidirectional three-phase grid-connected inverter module is a high-performance topology structure used to invert the electrical energy on the DC bus into three-phase AC power synchronized with the AC grid, and at the same time absorb AC power from the AC grid and rectify it into DC power to charge the battery or supplement the DC bus.

5. The integrated photovoltaic-storage grid-connected system for grid interaction according to claim 1, characterized in that, The MPPT and bidirectional DC / DC module adopt a coupled inductor or multi-phase interleaved parallel topology.

6. The integrated photovoltaic-storage grid-connected system for grid interaction according to claim 1, characterized in that, The internal DC bus is connected to the battery system via a battery interface and is controlled by the MPPT and bidirectional DC / DC module.

7. A control method for an integrated photovoltaic-storage grid-connected system for grid interaction as described in any one of claims 1-6, characterized in that, The system always operates in grid-connected mode, and the method includes: If the system is in a photovoltaic priority self-consumption mode, the photovoltaic power is transmitted to the DC bus through the MPPT and bidirectional DC / DC module; The bidirectional three-phase grid-connected inverter module converts the power into AC power to supply the local grid-connected load, and the surplus or insufficient power is automatically balanced by the AC grid.

8. The control method according to claim 7, characterized in that, The method further includes: If the system is in planned energy storage dispatch mode, the grid-connected system controller plans the battery charging and discharging schedule according to the electricity price signal or grid dispatch instructions; During the charging period, the surplus energy from the AC grid or photovoltaic system is controlled to charge the battery through the appropriate path; during the discharging period, the battery energy is controlled to be fed into the AC grid or used locally through the bidirectional three-phase grid-connected inverter module.

9. The control method according to claim 7 or 8, characterized in that, The method further includes: if the system is in dynamic grid support mode, monitoring the grid status in real time; when the frequency of the AC grid fluctuates, automatically adjusting the output active power of the bidirectional three-phase grid-connected inverter module to respond to the frequency; and when the voltage of the AC grid is abnormal, automatically adjusting the reactive power output to support the voltage.

10. The control method according to claim 7 or 8, characterized in that, The method further includes: if the system is in a joint optimization operation mode, real-time collaborative optimization of the MPPT operating point, battery charging and discharging power and inverter grid-connected power, and optimization of the power flow distribution among photovoltaic, energy storage and grid, with the goal of optimizing system economy or grid support.

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